UNITED STATES DEPARTMENT OF THE INTERIOR, Douglas McKay, Secretary //9 FISH AND WILDLIFE SERVICE, John L. Farley, Director GULF OF MEXICO ITS ORIGIN, WATERS, AND MARINE LIFE Prepared by American scientists under the sponsorship of the Fish and Wildlife Service, United States Department of the Interior Coordinated by Paul S. Galtsofl FISHERY BULLETIN 89 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE VOLUME 55 UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON : 1954 For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C. Price $3.25 LIST OF CONTRIBUTORS Anderson, William W., Chief, Gulf Fishery Investigations, Fish and Wildlife Service. Banner, Albert H., Associate Professor of Zoology, University of Hawaii. Bayer, Frederick M., Associate Curator, Division of Marine Invertebrates, U. S. National Museum. Behre, Ellinor H., Professor of Embryology, Louisiana State University. Butler, Philip A., Fishery Research Biologist, Fish and Wildlife Service. Chace, Fenner A., Jr., Curator, Division of Marine Invertebrates, U. S. National Museum. Chandler, Asa C, Professor of Biology, Rice Institute. Chitwood, B. G., formerly Professor of Biology, Catholic University of America. Clark, Austin H., Associate, Department of Zoology, U. S. National Museum. Coe, Wesley R., Professor Emeritus, Yale University. Conger, Paul S., Associate Curator in Charge Diatom Collection, U. S. National Museum. Cooper, G. Arthur, Associate Curator, Division of Invertebrate Paleontology and Paleobotany, U. S. National Museum. Davis, Charles C, Assistant Professor of Biology, Cleveland College, Western Reserve University. Deevey, Edward S., Jr., Osborn Zoological Laboratory, Yale University. Deichmann, Elisabeth, Curator, Museum of Comparative Zoology, Harvard College. GaltsofT, Paul S., Fishery Research Biologist, Fish and Wildlife Service. Graham, Herbert W., Chief, North Atlantic Fishery Investigations, Fish and Wildlife Service. Gunter, Gordon, Acting Director, Institute of Marine Science, University of Texas. Hartman, Olga, Allan Hancock Foundation, University of Southern California. Hedgpeth, Joel W., Marine Biologist, Scripps Institution of Oceanography, Universit3^ of California. Henry, Dora Priaulx, Oceanographic Laboratories, University of Washington. Hyman, Libbie H., American Museum of Natural History. Lasker, Reuben, Research Assistant, Marine Laboratory, University of Miami. Leipper, Dale F., Head, Department of Oceanography, Agricultural and Mechanical College of Texas. Lindner, Milton J., Chief, Fishery Mission to Mexico, Foreign Service of the U. S. A. Lowery, George H., Jr., Museum of Zoology, Louisiana State University. Lj-nch, S. A., Head, Department of Geology, Agricultural and Mechanical College of Texas. Manter, Harold W., Professor of Zoology, University of Nebraska. Marmer, H. A., Late Assistant Chief, Division of Tides and Currents, U. S. Coast and Geodetic Survey. m IV LIST OF CONTRIBUTORS Moore, Hilary B., Assistant Director, Marine Laboratory, University of Miami. Newman, Robert J., Museum of Zoology, Louisiana State University. Osburn, Raymond C, Allan Hancock Foundation, University of Southern Cali- fornia. Parker, Frances L., Scripps Institution of Oceanography, LTniversity of California. Phleger, Fred B., Scripps Institution of Oceanography, University of California. Pierce, E. Lowe, Associate Professor, Department of Biology, University of Florida. Price, W. Armstrong, Department of Oceanography, Agricultural and Mechanical College of Texas. Rehder, Harald A., Curator, Division of Mollusks, U. S. National Museum. Rivas, Luis Rene, Associate Professor of Zoology, University of Miami. Rounsefell, George A., Fishery Research Biologist, Fish and Wildlife Service. Schmitt, Waldo L., Head Curator, Department of Zoology, U. S. National Museum. Sears, Mary, Planktonologist, Woods Hole Oceanographic Institution. Shigley, C. M., Dow Chemical Company. Shoemaker, W. S., Department of Photographic Technology, Rochester Institute of Technology. Smith, F. G. Walton, Director, Marine Laboratory, University of Miami. Sprague, Victor, Director, Lake Chatuge Biological Laboratory. Taylor, Wm. Randolph, Professor of Botany, University of Michigan. Thorne, Robert F., Professor of Botany, State University of Iowa. Tierney, J. Q., Research Assistant, Marine Laboratory, University of Miami. Timm, R. W., Catholic University of America. Tressler, Willis L., U. S. Navy Hydrographic Office. U. S. Public Health Service, Division of Water Pollution Control, Shellfish Branch, Division of Sanitation. Van Name, Willard G., Curator, American Museum of Natural History. Voss, Gilbert L., Research Assistant, Marine Laboratory, University of Miami. Williams, Robert H., Chairman, Department of Marine Sciences, Marine Labora- tory, University of Miami. ZoBell, Claude E., Professor of Microbiology, Scripps Institution of Oceanography, University of California. PREFACE The purpose of this book is to summarize in a convenient form the present knowledge about the Gulf of Mexico. Such a summary is needed in con- nection with a large number of new investigations which are now being conducted in the Gulf of Mexico by Federal and State organizations and private institutions. It is hoped that the background information presented here will be useful to the investigators engaged in the new research projects and will save their time and effort. Scientific data concerning the Gulf of Mexico have been accumulating since the first explorations in the sixteenth century. They are scattered in thousands of technical publications, some of them rare and not readily avail- able to persons in the Gulf States. The preparation of a digest of the existing knowledge about the Gulf was suggested by a group of scientists attending, in November 1949, the meeting of the Gulf and Caribbean Fisheries Institute at Miami. The idea, proposed independently by Dr. Lionel A. Walford of the Fish and Wildlife Service and Dr. Waldo L. Schmitt, head curator, Department of Zoology, U. S. National Museum, was unanimously approved, and Paul S. Galtsoff was selected to carry out the project. The magnitude of the task has proved much greater than had been expected. Only through the hearty cooperation of the 55 contributors to this volume has it been possible to complete the work in about 3 years. For the purpose of this book the Gulf of Mexico is defined as a partially landlocked body of water indenting the southeastern periphery of the North American Continent. Its eastern boundary was drawn from Cabo Catoche at the tip of the Yucatan Peninsula to Key West at the southernmost tip of Florida. This boundary does not constitute a natural barrier; it was arbi- trarily determined because of the necessity of restricting the scope of the project. Inland the area under consideration extends to the limits of tidal waters. The book comprises a number of articles each written by a recognized authority in his field; these are arranged, with minor exceptions, in a taxo- nomic order following a list of phyla, classes, and orders prepared in 1936 for the American Association for the Advancement of Science and published by Duke University Press. This plan was carried out with the following exceptions: the sections on Rotatoria and Branchiopoda were omitted be- cause of the inability to find anyone willing to review these two groups; and, for the sake of convenience, the articles on parasitic worms were assembled in a single chapter. A pertinent bibliography is given at the end of each section. A greater number of bibliographical references, comprising more than 4,000 author and subject cards, was prepared in cooperation with Mrs. Margaret M. Quat- tromini of the Fish and Wildlife Service. The 12 sets of these files have been assembled for distribution among the institutions engaged in research in the Gulf of Mexico. No claim is made that these files are complete, and additional items can be added as new references become available. VI PREFACE In organizing and carrying out the project, splendid cooperation and valuable suggestions were received from the contributors to the book. The writer wishes to express his profound thanks to them for their continuous interest, the great amount of work required to prepare the articles, and their constructive criticism. Waldo L. Schmitt, head curator, U. S. National Museum, and William Randolph Taylor showed unremitting interest in the progress of the work, gave valuable advice in the formulation of the plan, and were most helpful in suggesting some of the authors and persuading them to undertake the review of various groups. My thanks are also due Richard S. Green, Chief, Shellfish Branch, Division of Sanitation, Public Health Service and A. F. Bartsch, biologist. Division of Water Pollution Control, Public Health Service, for organizing the material in the chapter on water pollution; to William S. von Arx of the Woods Hole Oceanographic Institution, Francis P. Shepard of Scripps Institution of Oceanography, Remington Kellogg, Director, U. S. National Museum, Frederick C. Lincoln, assistant to the Director, Fish and Wildlife Service, and Isaac Ginsburg, Ichthyologist, Fish and Wildlife Service, for valuable comments and constructive criticism of certain parts of the book. The work of Mrs. Margaret M. Quattromini in retyping the text and ar- ranging the bibliographies is gratefully acknowledged. Paul S. Galtsoff, Fishery Research Biologist. CONTENTS Chapter Pago I. Historical sketch of the explorations in the Gulf of Mexico. By Paul S. Galtsoff 3 Sources 3 Pre-Columbian era 3 Discovery of the Gulf of Mexico 4 Sixteenth and seventeenth centuries 8 Eighteenth century 18 From the beginning of the nineteenth century to the present time 22 Bibliography 32 II. Geology. Shorelines and coasts of the Gulf of Mexico. By W. Armstrong Price 39 Status of studies of coasts and shorelines 39 Shoreline classification 39 Sources of information 42 Acknowledgments 43 Structural and regional geo-oceanographic approach to shoreline descrip- tion and classification 43 Coasts and hinterland 43 Regional coastal types 44 Young erogenic coasts 44 Alluvial coasts 46 Drowned limestone-plateau coastal plains 48 Biogenous environment 50 Emergent and submergent shorelines of the Gulf 53 Use of terms 53 Submergent shoreline features 54 Emergent shoreline features 55 Shoreline changes and processes 58 Shoreline simplification 58 Equilibrium profiles of continental shelf bottom 59 Directions of longshore drift 62 References 62 Geology of the Gulf of Mexico. By S. A. Lynch 67 Early concepts 67 Gulf coast geosyncline 68 Geomorphology of Gulf of Mexico 71 General characteristics 71 Origin of major features 71 Geomorphology by areas 72 Eastern Gulf area 73 Mississippi Delta area 73 Northern Gulf of Mexico - 74 Mexico 75 Mexican Basin 75 Sediments of Gulf of Mexico 75 Source of sediments 75 Place of deposition 76 Early studies of submarine deposits 77 Recent studies of submarine deposits 77 Sedimentary provinces 78 Eastern Gulf 78 Mississippi Delta 80 7495? VIII CONTENTS Chapter — Continued II. Geology of the Gulf of Mexico — Continued Sediments of Gulf of Mexico — Continued Page Louisiana shelf 81 Western Gulf 81 Yucatdn Peninsula 82 Cuba 82 Mexican Basin 82 Conclusions 82 Bibliography 83 III. Marine meteorology of the Gulf of Mexico, a brief review. By Dale F. Leipper 89 Extra tropical cyclones 89 The general air circulation and some of its consequences 89 Average conditions 90 Weather observing stations 93 Typical upper air soundings 93 Northers 95 Meteorological tides 95 Hurricanes 96 Applications of marine meteorology in the Gulf 96 Further sources of information 96 Conclusion 97 Literature cited 97 IV. Physics and chemistry of Gulf waters. Tides and sea level in the Gulf of Mexico. By H. A. Marmer 101 Harmonic constants 104 Types of tide 108 Semidaily type 110 Daily type 110 Mixed types 112 Characteristics from harmonic constants 113 Disturbing effects of wind and weather 113 The tide in the Gulf of Mexico 114 Sea level 115 Availability of tidal data 117 Literature cited 118 Physical oceanography of the Gulf of Mexico. By Dale F. Leipper 119 Ocean currents 119 Sea surface temperatures 125 Sea temperature variations with depth 131 Salinity 135 Temperature-salinity relationships 135 Ocean wind waves and swell 136 Shallow water oceanography 136 Bibliography 136 Light penetration in the Gulf of Mexico. By William S. Shoemaker 139 Distribution of chemical constituents of sea water in the Gulf of Mexico. By Robert H. Williams 143 Salinity H3 Dissolved oxygen 145 Phosphorus 145 Nitrate-nitrogen 147 Nitrite-nitrogen 148 Hydrogen ion concentration (pH) 148 Alkalinitv and carbon dioxide components 148 Copper.] 148 Miscellaneous chemical constituents 148 CONTENTS IX Chapter — Continued IV. Distribution of chemical constituents of sea water — Continued Paee Summary 149 Literature cited 150 The recovery of minerals from sea water. By C. M. Shigley 153 V. Plant and animal communities. Phytoplankton of the Gulf of Mexico. By Charles C. Davis 163 The zooplankton of the Gulf of Mexico. By Hilary B. Moore 171 Material 171 Bibliography 172 Red tide. By Reuben Lasker and F. G. Walton Smith 173 Sketch of the character of the marine algal vegetation of the shores of the Gulf of Mexico. By Wm. Randolph Taylor 177 General nature of the flora ^ 177 Marine botanical studies of the Gulf of Mexico 177 Collateral works of reference for the Gulf algal flora 178 Chief types of algal vegetation 179 Shifting sandy beaches and estuarine mud flats 179 Stable sand and mud; pools, small lagoons and coves 179 Protected coves and pools with a marine channel 180 Protected bays and lagoons 180 Mangrove thickets 180 Tidal streams 1 80 Sandy shallows and "reefs" of shell and coral rubble 183 Rocky shores and inshore reefs 183 Pelagic seaweeds 185 Local features of the Gulf coast marine algal flora 186 Cited literature of Gulf of Mexico algae and bibliography of principal works dealing with comparable West Indian marine algae 189 Flowering plants of the waters and shores of the Gulf of Mexico. By Robert F. Thorne 193 Submarine meadow 193 Mangrove swamp 194 Salt marsh 196 Sand-strand vegetation 198 Conclusion 199 Bibliography 199 Bottom communities of the Gulf of Mexico. By Joel W. Hedgpeth 203 Investigations of recent facies 205 The oyster community 206 Serpuloid reefs 210 The jetty community 210 Sand beach communities 211 The shrimp ground community 211 The coral and sponge communities 213 Literature cited 213 VI. Bacteria, fungi, and unicellular algae. Marine bacteria and fungi in the Gulf of Mexico. By Claude E. ZoBelL., 217 Dinoflagellates of the Gulf of Mexico. By Herbert W. Graham 223 Present status of diatom studies in the Gulf of Mexico. By Paul Conger. 227 Literature 227 Campeche Bay 227 Mobile Bay 228 Tortugas and west coast of Florida 228 Other records 228 Diatom floras of Gulf and adjacent waters 229 Ecology 229 Productivity 229 Silica relationships 230 Bibliography 23 1 CONTENTS Chapter — Continued VII. Protozoa. Page Gulf of Me.xico Foraminifera. By Fred B. Phleger and Frances L. Parker. 235 Benthonic Foraminifera 235 Planktonic Foraminifera 241 Literature cited 241 Protozoa. By Victor Sprague 243 Survey of the literature 243 Distribution of Protozoa 244 Mastigophora 245 Sarcodina 246 Sporozoa 247 Unidentified species of Nematopsis 249 Ciliata 251 Suctoria 255 Literature cited 255 VIII. Sponges, coelenterates, and ctenophores. The Porifera of the Gulf of Mexico. By J. Q. Tierney 259 Biology of commercial sponges. By F. G. Walton Smith 263 Hydroids of the Gulf of Mexico. By Edward S. Deevey, Jr 267 Collecting 267 Zoogeography 268 Check list of Gulf of Mexico hydroids 269 Summary 27 1 Literature cited 27 1 Hydromedusae of the Gulf of Mexico. By Mary Sears 273 Siphonophores in the Gulf of Mexico. By Mary Sears 275 Scyphozoa. By Joel W. Hedgpeth 277 Anthozoa: Alcyonaria. By Frederick M. Bayer 279 Anthozoa: The anemones. By Joel W. Hedgpeth 285 Notes on common species 287 Bibliography 290 Gulf of Mexico Madreporaria. By F. G. Walton Smith 291 Ctenophores in the Gulf of Mexico. By Mary Sears 297 IX. Free-living flatworms, nemerteans, nematodes, tardigrades, and chae- tognaths. Free-living flatworms [Turbellaria] of the Gulf of Mexico. By L. H. Hy man 30 1 The nemertean fauna of the Gulf of Mexico. By Wesley R. Coe 303 Geographical distribution 303 Reproduction and regeneration 304 Ecology 304 Food 304 Key for identification 305 Systematic description of species 305 Paleonemertea 305 Heteronemertea 306 Hoplonemertea 307 Bdellonemertea 309 Bibliography 309 Eehnioderida of the Gulf of Mexico. By B. G. Chitwood 311 Free-living nematodes of the Gulf of Mexico. By B. G. Chitwood and R. W. Timm 313 Nematode anatomy 313 Historical r&um6 314 Classified list of species 314 Phasmidea 314 Aphasmidea 314 CONTENTS XI Chapter — Continued IX. Free-living nematodes of tlie Gulf of Mexico — Continued Page Geographic distribution 318 Ecology and life habits 319 Li terat ure cited 320 Tardigrades of the Gulf of Mexico. By B. G. Chitwood 325 Notes on the Chaetognatha of the Gulf of Mexico. By E. Lowe Pierce 327 Notes on the range of species collected in the Gulf of Mexico 328 Summary 328 Literature cited 329 X. Parasitic worms. Parasitic helminths. By Asa C. Chandler and Harold W. Manter 333 Trematoda of the Gulf of Mexico. By Harold W. Manter 335 Monogenea 335 Aspidogastrea 336 Digenea 336 Gasterostomata 336 Prosostomata 336 Host specificity of trematodes of marine fishes of the Gulf of Mexico. . 342 The geographical distribution of trematodes of fishes at Tortugas, Florida 343 Trematodes of turtles 345 Trematodes of birds 346 Trematodes of mammals 346 Studies on larval stages and life cycles of trematodes of the Gulf of Mexico 347 Summary 348 Literature cited 348 Cestoda. By Asa C. Chandler 351 Tetraphyllidea 351 Trypanorhyncha 352 Incertae sedis 353 Pseudophyllidea 353 Cyclophyllidea 353 Acanthocephala. By Asa C. Chandler 355 Eoacanthocephala 355 Palaeacanthocephala 355 Nematoda. By Asa C. Chandler 357 Ascaridata 357 Incertae sedis 358 Bibliography (Cestoda, Acanthocephala, Nematoda) 358 XI. Bryozoa, Brachiopoda, Phoronida, and Enteropneusta. The Bryozoa of the Gulf of Mexico. By Raymond C. Osburn 361 Brachiopoda occurring in the Gulf of Mexico. By G. Arthur Cooper 363 Phoronida. By Joel W. Hedgpeth 367 Enteropneusta. By Joel W. Hedgpeth 369 XII. Echinoderm. Echinoderms (other than holothurians) of the Gulf of Mexico. By Austin H. Clark 373 Crinoidea 373 Echinoidea 374 Asteroidea 375 Ophiuroidea 376 Bibliography 378 The holothurians of the Gulf of Mexico. By Elisabeth Deichmann 381 Technique 382 Key to the orders 383 Elasipoda 383 Aspidochirota 384 XII CONTENTS Chapter — Continued XII. The holothurians of the Gulf of Mexico — Continued Page Dendrochirota 394 Molpadonia 405 Apoda 406 Bibliography 408 XIII. Annelids and miscellaneous worms. Polyehaotous annelids of the Gulf of Mexico. By Olga Hartman 413 Review of the families 413 Appendix on some ecological associations 416 Literature cited 416 Miscellaneous vermes. By Joel W. Hedgpeth 419 Echiurida 419 Sipuneulida 419 Literature cited 420 XIV. Arthropods: Xiphosura, Pycnogonida, and Crustacea. Xiphosura. By Joel W. Hedgpeth 423 Pycnogonida. By Joel W. Hedgpeth 425 Marine Ostracoda. By Willis L. Tressler 429 Ecology 430 Ostracoda reported from adjacent regions 436 Caribbean Sea (off Colon) 436 West Indies . 436 Cuba 1. 436 Bahama Islands 436 Conclusions 436 Bibliography 436 Copepoda. By Waldo L. Schniitt 439 Cirripedia. The barnacles of the Gulf of Mexico. By Dora Priaulx Henry,. 443 Mysidacea and Euphausiacea. By Albert H. Banner 447 Stomatopoda. By Fenner A. Chace, Jr 449 Decapoda of the Gulf of Mexico. By Ellinor H. Behre 451 General physiographic regions 451 Comparison of faunas 453 Reference collections 453 Papers of particular reference to Gulf decapods 454 Biology of commercial shrimps. By Milton J. Lindner and William W. Anderson 457 XV. xMollusks. Biology of the spiny lobster. By F. G. Walton Smith 463 Mollusks. By Harald A. Rehder 469 Past work done in this area 469 General 469 Florida 469 Alabama-Louisiana 470 Texas 470 Mexico 470 Cuba 470 Deeper waters 47 1 Ecology 47 1 Caribbean Province 471 Carolinian Province 472 Deeper waters of the Gulf of Mexico 472 Bibliography 473 Cephalopoda of the Gulf of Mexico. By Gilbert L. Voss 475 Systematic list 477 Literature cited 477 Summary of our knowledge of the oyster in the Gulf of Mexico. By Philip A. Butler 479 Oyster reefs of the Gulf of Mexico. By W. Armstrong Price 491 CONTENTS XIII Chapter — Continued XVI. Tunicates and lancelets. P«Be TheTtinicataof the Gulf of Mexico. By Willard G. Van Name 495 Ascidian fauna of the Gulf of Mexico 495 The pelagic Tunicata 496 Bibliography 497 The lancelets. Branchiostomidae. By Joel W. Hedgpeth 499 XVII. Fishes and sea turtles. The origin, relationships, and geographical distribution of the marine fishes of the Gulf of Mexico. By Luis Rene Rivas 503 Shore fishes 504 Pelagic fishes 505 Deep sea fishes 505 Literature cited 505 Biology of the commercial fishes of the Gulf of Mexico. By George A. Rounsefell 507 Taxonomy and distribution of sea turtles. By F. G. Walton Smith 513 Family Cheloniidae 513 Family Dermochelidae 513 Key to the Gulf of Mexico sea turtles 514 Distribution in the Gulf of Mexico 515 Bibliography 515 XVIII. The birds of the Gulf of Mexico. By George H. Lowery, Jr., and Robert J. Newman 519 Offshore birds 520 Birds of the coast 526 Coastal breeding birds 529 Regular visitants on the coast 530 Visitants to coast not of regular annual occurrence 532 Land birds over the open Gulf 535 Literature cited 538 XIX. Mammals of the Gulf of Mexico. By Gordon Gunter 543 Pinnipedia 543 Sirenia 543 Cetacea 545 General information 545 Cetaceans of the Gulf of Mexico 546 Odontoceti. Toothed whales 546 Mysticeti. Baleen whales 550 Literature cited 550 XX. Pollution of water. Aspects of water pollution in the coastal area of the Gulf of Mexico. Pre- pared in the Division of Water Pollution Control, and Shellfish Branch, Division of Sanitation, Public Health Service, U. S. Department of Health, Education and Welfare 555 Nature of pollution affecting the Gulf waters 555 Water pollution control agencies, programs, and laws 556 Florida 557 Alabama 557 Mississippi 557 Louisiana 557 Texas 557 Federal-State shellfish control program 557 Summary of water pollution data 558 Damages to resources caused by pollution 561 Lower Florida area 564 Peace River area 564 Tampa Bay area 564 Withlacoochee River area 565 XIV CONTENTS Chapter — Continued XX. Aspects of water pollution — Continued Damages to resources caused by pollution — Continued Page Suwannee River area 565 Ochlockonee River area 566 Apalachicola River area 566 Choctawatchee River area 566 Perdido-Escambia area 567 Mobile Bay area 567 Pascagoula River area 568 Pearl River area 569 Lower Mississippi River area 569 Atchafalaya River area 569 Calcasieu River area 570 Sabine River area 570 Neches River area 570 Trinity River area 571 Brazos River area 571 Colorado River area 572 Guadalupe River area 572 Nueces River area 572 Lower Rio Grande area 573 The Gulf coast of the Republic of Mexico 573 Literature cited 574 Index 577 CHAPTER I HISTORICAL SKETCH OF THE EXPLORATIONS IN THE GULF OF MEXICO HISTORICAL SKETCH OF THE EXPLORATIONS IN THE GULF OF MEXICO By Paul S. Galtsoff, Fish and Wildlife Service, United States Department of the Interior The brief historical sketch of discoveries and explorations in the Gulf of Mexico presented m this paper is based on published materials avail- able in this country. Fortunately, the large collection of books and maps in the Library of Congress, Harvard University, American Geo- graphical Society, and the Public Library of New York York City provided abundant material from which the progress of scientific knowledge of the Gulf of Mexico could be traced with reasonable completeness. A wealth of data about the earlier discoveries in the Gulf can be found in the classical works of Winsor (1884-89), Thacher (1896), Lelewel (1852), in 20 volumes of history of voy- ages by Prevost (1746-89), Harrisse (1900), and Fiske (1892). A student of history of explorations in the New World finds in the writing of Alexander von Humboldt, especially his Examen Critique . . . (1836-39) a rich source of critical information. A catalog of maps of the Spanish possessions published by the Library of Congress under the title, The Lowery Collection (Lowery 1912) not only gives detailed descriptions of maps printed from 1502 to 1820 but also contains a great amount of information about the explorations and cartography of the Gulf. A brief but com- prehensive review of the explorations between 1492 and 1543 is given by Kohl (1863). Many other publications and maps in various institutions in the United States were consulted. The more important of them are the catalog of maps, British Museum (1884, 1885), the catalog of geographical documents in the national library in Paris (Paris, Bibliothqeue nationale, 1892), Phillips' list of maps of America, list of geo- graphical atlases (U. S. Library of Congress, 1901, 1909-20), and the description of Mexican maps by Torres Lanzas (1900). The publications of Phillips are listed in some libraries under his name, while in others they appear only under his titles (see Bibliography) ; the work of Torres Lanzas may be found under "Spain," "Torres," 259534 O— 54 2 and "Lanzas." Other references not discussed in the text are listed in the bibliography. Reports, letters, and other documents written by the earlier explorers show clearly that ad- venture, military conquest, and search for fabulous riches were the principal impelling forces that lured thousands of men of the sixteenth and seventeenth centuries to embark on the daring voyages beyond the unknown western ocean. Science played only a minor part in these risky undertakings, and scientific observations made in the course of these explorations, which so greatly enhanced the knowledge of the inhabitable world, were merely incidental byproducts of mercenary or military ventures. History of the discovery and colonization of the New World is beyond the scope of this chapter. The following pages contain, therefore, only a brief summary of scientific achievements of the many explorations in the Gulf of Mexico from the time of its discovery to the present days. The author hopes that the picture of the scientific progress in the studies of the Gulf which he pre- sents here has not been distorted by errors or omissions. PRE-COLUMBIAN ERA Written history of the explorations in the Gulf of Mexico naturally begins with the discovery of the New World by Columbus in 1492, but long before the white man set foot on the shores of the islands of America the existence of a large, landlocked body of water now called the Gulf of Mexico was known to the tribes that inhabited its coastal plains and sailed and fished in its waters. Indians living along the west coast of Florida did not venture beyond a narrow coastal zone in which they fished from small dugout canoes. This conclusion is well substantiated by archaeological research in Florida and especially by the study of the contents of numerous shell heaps (Walker 1880, 1885; Wiley 1949), which contain the rem- 3 4 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE nants of birds, fishes, and mollusks found only in coastal waters. The Aztecs, who developed their own system of navigation, were fairly well acquainted with certain parts of the Gulf. This is probably true also of the Mexican and Yucatec Indians, who sailed over considerable distances off shore. Evidence for this is given in the report of the fourth voyage of Columbus, who on July 2,1502, sighted a large Indian ship of the size of a Spanish galley about 80 miles east of the Yucatdn coast (Kohl 1863). The art of map making practiced by Aztecs had reached a high degree of perfection as can be judged from the incident described by Bernal Diaz de Castillo (Hakluyt Society Works, 2d ser.. No. 24, p. 129, quoted from W. Lowery, 1912, p. 27). During the Cortes invasion of Mexico, he writes, "The great Montezuma gave our Captain a henequen cloth on which were painted and marked very true to nature, all the rivers and bays on the northern coast from Pdnuco to Tabasco, that is, for a matter of one hundred and forty leagues, and the river of Coatzacoalcos was marked on it." For more than 1,400 years of the Chi'istian era the geography of the western world was under the influence of the writings of Claudius Ptolemy, an Egyptian who lived in Alexandria about the middle of the second century (the dates of his life are usually given as between 90 and 168 A. D.), and spent 40 years in making astronomical observations. For many centuries Ptolemy's data on the locations of many places on earth with reference to the parallel of Alexandria were the principal source of information for map makers. No existing Ptolemy maps are known earlier thaa that of the thirteenth century, the first printed edition of which was executed in 1475 in Vicenza (Thacher 1896). Some idea of the type of maps available to navigators at the end of the fifteenth and the beginning of the sixteenth century can be gained from examining figure 1 representing the map of the world by Johannes Ruysch, copied from Ptolemy's geography of 1507-08. The discovery of the New World has been already incorporated in it, and the name "Mundus novus" appears for the first time on the engraved map. During the last 40 years of the fifteenth century the Portuguese seamen made persistent and almost continuous efforts to search for new Atlantic islands beyond the Azores. So far, no docu- mentary proof has been found of the pre- Columbian discovery of western lands by Portu- guese, but, as stated by the Portuguese historian, Antonio Baiao, "... there are numerous in- dications that the existence of other islands be- yond the Azores was known or suspected in Portugal. It was in the wake of these indications that Columbus sailed. His voyage is integrated with cycle of Portuguese explorations of the Western Ocean." (Quoted from Morison, 1940, p. 75.) Because of the secrecy attached by the Portu- guese Government to the discoveries of new lands and their location, the findings of Portu- guese seamen were lost, and only inconclusive traces of their efforts remain on certain documents originated in Lisbon. One of these is the famous map by Alberto Cantino which is discussed in the next section of this article (p. 8). DISCOVERY OF THE GULF OF MEXICO The discoverer of the New World came almost to the very entrance of the Gulf of Mexico but failed to enter it. On his second voyage, June 1494, Columbus followed the southern shores of Cuba as far as Isia de Pinos, where he stopped. Disregarding the infoi'mation received from the Indians that the end of the land was not far, he changed his course and sailed eastward. The decision was influenced by his strong belief that Cuba represented the end of the new continent. As it is generally known, he asked his companions to sign a statement to this effect. The declaration, however, was not universally accepted since the earliest maps of the New World by Cosa, 1500 (fig. 3, p. 9), and Waldseemiiller, 1507 (fig. 2), show Cuba (Isabella) as an island. The question who was the first European ex- plorer to sail along the coast of the American continent is by no means settled. The credit is usually given to the man whose name is forever associated with the New World. Amerigo Ves- pucci, the third son of a Florentine notary, was born on March 9, 1451. He studied diligently and became proficient in astronomy and in the use of the astrolabe, but his principal interest was in a commercial career. After establishing himself as an agent for the House of Cadiz, Vespucci undertook to settle the claims left after the death GULF OF MEXICO o a oi o a c o ■-s a o Oh a o FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE GULF OF MEXICO of his friend, Juanito Beranii, who contracted to supply and equip 12 vessels of 900 tons each for the Spanish Crown. In 1497, at the request of the king, Vespucci joined the expedition to the New World. In his own words, "the King, Don Fernando of Castile, being about to dispatch four ships to discover new lands toward the west, I was chosen to aid in making discovery" (Thacher 1896, p. 69). He never explained his exact duties aboard the ship, but judging from his previous experience in commercial methods he probably went as a sort of supercargo to supervise the distribution of food, to weigh the gold, and to keep accurate tally of the Crown's share which, according to the royal decree of 1495, was one- third of the total gold obtained by the expeditions. Vespucci started from Cadiz on May 10, 1497. After reaching the Canary Islands in about 10 days, the fleet sailed west and quarter-southwest for 37 days (27 days according to the Latin text of Vespucci's letter) until land was sighted a thousand leagues from the Canaries. Making allowance for an error of 1° latitude and about 8° longitude, Thacher (1896) estimated that the landfall would be off the coast of Honduras in the vicinity of Cabo Gracias a Dios. It is interesting to note that the ships passed between the islands of the Caribbean without noticing them. A safe harbor was found after 2 more days of sailing northward. Vespucci describes how, skirting the coast, he saw villages one of which, consisting of 40 houses, was built, like Venice — upon the water. It was near this village that a fierce encounter with Indians took place in which 15 or 20 natives were killed. The place is probably on the shores of Campeche Bay, north of Tabasco. Continuing for 80 leagues farther along the coast, the expedition came to a place inhabited by different people. It was called the Province of Lariab, a name which later on caused a great deal of confusion and argument since in the Latin edition of Vespucci's letter the name was trans- lated "Parias," a mistake that led many to believe that the explorer referred to the Gulf of Paria off the Venezuelan coast discovered by Columbus in 1498 during his third voyage. According to Thacher, the word "Lariab" is a compound word of Quiche dialect which means "there are many." It is assumed that the expres- sion was used by the natives, who misunderstood the question addressed to them by Spaniards about the name of their province and answered that there were many people in the land. Vespucci states that this land, which is probably near Tampico in Mexico, is "within the torrid zone, close or just under the parallel described by the Tropic of Cancer where the pole of the horizon has an elevation of 23° at the extremity of the second climata." (Quoted from Thacher, 1896.) The term "clima" (plural "climata") of ancient Greek cartographers denotes parallel zone or belt, the width of which, according to Hipparchus, is determined by astronomical observations on the basis of the longest day of the year. The rest of the letter (Vespucci, 1926 edition) caused endless arguments among geographers. Vespucci states that from Lariab they navigated in sight of land and covered 870 leagues, still going in the direction of the "maestrale." This course, corresponding to northwest, would have brought the expedition over the continent nearly to the coast of California. Harrisse (1900) ignores the western component of the direction of "maestrale" and considers only its northerly meaning. He states that plotting 870 leagues along the American coast would bring Vespucci's ships as far north as Cape Hatteras. According to Vespucci's narrative, the expedition turned east toward Bermuda from this place and returned to Cadiz on October 15, 1498. Humboldt (1836-39) expresses doubt whether Vespucci ever made this voyage and denies him the credit of discovery of the new continent. According to Humboldt, at the time of his sup- posed voyage Vespucci was engaged in equipping the third expedition of Columbus and could not possibly have taken part in the explorations he describes. Obvious inconsistencies in the text of Vespucci's informal letters are unfortunately augmented by errors in translation. The accusa- tions that Vespucci was a fake (see Winsor 1886, v. 2, pp. 129-136; Harrisse 1895) are answered, however, by pro-Vespuccian writers (Varnhagen, 1865, 1869a, 1869b, 1870), and final settlement of the question awaits further historical research. Bremer (1940) advances an entirely new theory that the honor of the discovery of the Gulf of Mexico belongs to a Portuguese by the name of Caspar Corte Viall who, shortly before 1500, sailed to the west and upon returning to Portugal spread the news of the existence of a new continent and islands in the western ocean. In support of his 8 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE hypothesis, Bremer mentions a place on the northern coast of the Gulf of Mexico known by tradition as Portuguese Field, which he considers may be a landing place of Portuguese sailors. The evidence, however, is not convincing. SIXTEENTH AND SEVENTEENTH CENTURIES The progress of early discoveries in the Gulf may best be followed by studying the maps of this period. Since the data concerning the location of new lands were considered by the Spanish Govern- ment a state secret, maps and reports which the captains of the ships were requested to submit to tte government immediately upon their return to Spain were carefully guarded, and all means were taken to prevent them from falling into the hands of other European powers. As a consequence of this policy of secrecy the first maps of the New World were engraved and published outside Spain (in Italy, France, and Germany), using data which were often surreptitiously obtained or smuggled out of the countr3\ Many of the original docu- ments, usually drawn on parchment or oxhide, were lost or destroyed in war and by accidents; only a few of these valuable documents were recovered in more recent years after many vicissitudes. The first map of the world summarizing the discoveries in the western ocean and showing the Gulf of Mexico was drawn by Juan de la Cosa, the companion and pilot of Columbus and owner of the caravel, Santa Maria, which bore the admiral's flag and was the first ship to reach the New World. The map embodies the results of seven important voyages: the three voyages of Columbus in 1492, 1493, and 1498; the first and second voyages of Vespucci in 1497 and 1498; and the first and second voyages of Cabot in 1497 and 1498. The date of the execution of the map is established by the inscription which reads, "Juan de la Cosa el fiso en el porto de Santa Maria en ano de: 1500." The history of this unique historical document is interesting. After being lost for tlu-ee centuries, the map was found in 1832 in a Paris bric-a-brac shop where it was purchased for a small sum by Baron de Walckenaer. Its great significance was pointed out by Humboldt (1836) when in 1832 he drew public attention to its importance. After the death of Walckenaer . the map was offered for sale at public auction and was purchased for 420 francs by the Hydrographic Department of the Spanish Government. Today it hangs in the Naval Museum of Madrid, listed in the museum guide book as number 553, with a detailed descrip- tion and a brief history of this remarkable docu- ment (Madrid, Museo Naval, 1945). The original map is drawn on oxhide, 5 feet 9 inches long, cut square at the tail of the hide where its width is 3 feet 2 inches. The Tropic of Cancer runs vertically through the middle; the top corresponds to the extreme west and includes the Caribbean Sea and the Gulf of Mexico. The latter area, instead of geographical details, is occupied by a rectangular drawing representing St. Christopher bearing the Christ child, a rather crude imitation of the famous woodcut engraving of 1423. Originally the map was rich in blue and gold and illuminated after the fashion of medieval manuscripts, but today it is torn and faded. Peter Martyr, who saw it in 1514 in the house of the Bishop of Burgos, head of the Maritime Department of the Casa de Contratacion, re- marked on its highly colored beauty. The photographic reproduction of the Cosa map available in the Library of Congress is too blurred and cannot be clearly copied in the text. The part of the map referring to the Gulf of Mexico can be seen in figure 3, representing a copy found in volume 4 of Humboldt's Examen Critique (1836-39); this part of the map was redrawn and oriented by Humboldt in the con- ventional manner. One of the earliest documents showing certain details of the New World and a part of the Gulf of Mexico is Cantino's map of the world. It represents for the first time what appears to be the west coast of Florida and the adjacent part of the Gulf (fig. 4). It was drawn as a large planisphere on parchment in gold and various colors. The map derives its name from Alberto Cantino, Ambassador of the Duke of Ferrara t«. the King of Portugal. The original, located in Biblioteca Estense in Modena, was obtained by Cantino for 12 ducats and was sent by him with a letter to Senor "Duca Hercole" in Lisbon. In later years the map was used as a screen and finally was recovered in a damaged condition from' the shop of a pork butcher in Modena and deposited in the library. Some cartographers (see Lowery 1912, pp. 5-6) GULF OF MEXICO Figure 3. — Western part of the map of the new discoveries drawn by Juan de la Cosa. Reproduced from a copy Humboldt's Examen Critique (1836). 10 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Miisartittis: H, #(cm\^ v n ^ iTt P 36 antllbaetitf ^cyttcalld la: *^ t-^ 5 ^ Ml '\ .M '-^A ^nSd r(k f>frti^W.rmUhi n maSWtf Figure 4. — Western portion of the Cantino map of the world, 1502. Original without name, date, or title. Reproduced from a copy in Harrisse's Les Corte-Real 1883. GULF OF MEXICO 11 consider that Cantino was familiar with the Portufjuese voyages to the New Workl and incor- porated their discoveries in his drawing. This subject, as well as the questions whether "Ilha Ysabella" on the map represents the island of Cuba or the Crooked Islands group called "Isa- bella" by Columbus, and whether the peninsula west of it is Florida, are critically discussed by Morison (1940). The Gulf of Mexico is very crudely shown on the map of the world made by the German carto- grapher, Waldseemiiller, and printed in 1507 in St. Die, Lorraine. This map is famous because for the first time the continent of the New World is shown with the name "America" attached to it in honor of the Florentine explorer. The origi- nal is owned by Franz Joseph II of Liechtenstein.' Of the many expeditions that sailed to the New World during the first decade of the sixteenth century, the more important ones were those headed by Hojeda, 1499; Nino and Guerra, 1500; Pinzon, 1499-1500; Lepe, 1500; Bastidas, 1500-02; Hojeda and Vergara, 1502-03; and Cosa, 1504-05. Results of these ventures materially enlarged the knowledge of the geography of the eastern part of the Caribbean area, but its western section, in- cluding the Gulf of Mexico, remained unexplored. In 1513 the expedition headed by Ponce de Le6n made a formal discovery of Florida, the existence of which was probably known to Spanish and Portuguese adventurers who visited the land north of Cuba but left no records of their findings. On Easter Sunday, March 27 of that year. Ponce de Leon with his three ships was in sight of land not far from the present city of Jacksonville. To commemorate the holiday the land was named la Florida. Failing in his attempt to circumnavi- gate the "island" Ponce de Le6n turned south and on May 12 of the same year found a chain of islands which he named las Islas de los Mdrtires (present Florida Keys), and about a month later he discovered the Tortugas. In the following year, 1514, the King of Spain incorporated the newly discovered land in an administrative re- gion known as Adelantado de la Isla Bimini e la Florida. Ponce de Le6n was the first explorer who re- corded the existence of a strong current along the • In May 1950 the map was offered for sale at an auction in New York City with the condition that bids should exceed $50,000, but in the last minute was withdrawn by the owner. east coast of Florida. He reported that his ships' while crossing the stream near Cape Canaveral, frequently were swept by strong current. He obviously was referring to that part of the Gulf Stream which at present is known as the Florida Current (Herrera 1601, 1728; Stommel 1950). In 1516 Diego Miruelo undertook another ex- pedition to Florida, and in the following year, 1517, Fernando de Cordoba and Antonio de Ala- minos explored the northern and western coasts of Yucatin. Driven for several days by a severe storm they finally saw land with a large Indian town, near Cabo Catoche. The expedition re- corded many points, bays, and harbors along the west coast of the Gulf and safely reached the Bay of Campeche, giving it its present name. Trouble started, however, near the place called Champo- ton where C6rdoba and his landing party were attacked by Indians. In this encounter, C6rdoba was badly wounded and many of his soldiers were killed. Alaminos, the principal pilot of the ex- pedition, decided to take advantage of the pre- vailing easterly winds and sailed north to Florida and then turned south toward Cuba. His deci- sion was a right one. In a few days the ships crossed the Gulf and returned to Cuba, where C6rdoba died of his wounds. Scientific results of the expedition were signifi- cant. More than 500 miles of the Gulf coast were mapped; proof was obtained of the existence of an open channel between the Florida and Yucatdn Peninsulas; and valuable information was accumulated regarding the prevailing winds, cur- rents, and depth of water. Alaminos was still under the impression that Yucatan was an island. The name Yucatdn was taken from the expression "Uyucatan" which the Spaniards frequently re- ceived from Indians in reply to their questions, the meaning of which was "we don't understand you." Before his death, C6rdoba appointed his nephew , Juan de Grijalva, commander of a force consisting of 4 ships and 250 men. Experienced Antonio de Alaminos was again the senior pilot of the expedition which on April 20, 1518, sailed from the harbor of Matanzas (Cuba) and followed C6rdoba's former route toward the Cape of Yuca- tdn. Stormy weather drove the expedition far- ther south along the eastern coast of the peninsula toward an island called by the Spaniards la Isla de Santa Cruz but known at present as Isla de 12 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Cozumel. From this point the ships turned north around the Yucatan Peninsula and on May 26 passed the point reached by the previous expedi- tion and entered a large bay which was called Boca de Terminos (Laguna de Terminos on mod- ern charts) . Grijalva thought that he had reached the end of the YucatAn island which he named La Isla de Santa Maria de Remedios, the name which appeared on maps of that time. The expedition continued along the unknown coast for nearly a thousand statute miles to a point a short distance south of the present location of Tampico. Grijalva's expedition substantially contributed to our knowledge of Gulf geography. The names of many familiar places such as Grijalva River, the bay and river of Tonola, Coatzacoalcos River, Alvarado River, and many others were established and their positions indicated on maps. Alaminos made many astronomical observations between Yucatan and Tampico. Some of his determina- tions of latitude — for instance, that of a small island where the present town of Veracruz is located — were accurate within 1°. He also ob- served and recorded the currents along the coast and made soundings and other hydrographical observations. When the expedition entered the mouth of the Grijalva River the Spaniards were encountered by many Indians having gold in their possession. When asked for the name of the land the metal came from, the Indians replied, "Mexico." In this way the Spaniards heard for the first time the name of the country which played such an important role in the expansion of Spanish power in America. Upon reaching his farthermost point at Pinuco, Grijalva became convinced that he was exploring the coast of a large continent and not of an island as he had first believed. Realizing the importance of this discovery, he dispatched Pedro de Alvarado on a fast ship to inform Governor VeMsquez of Cuba of his important finding and saOed back fol- lowing the same route the expedition took from Cuba. A new expedition organized by Velasquez in 1519 was in command of Hernando Cortes with Antonio de Alaminos again serving as chief pilot. In May of the same year the expedition sailed around Cape Catoche, following in general the route taken previously by Grijalva. This time the Laguna de Terminos was explored more care- fully by Captain Escobar who established its true nature as a shallow, landlocked body of water not suitable for establishing a colony on its banks. Antonio de Alaminos, who was sent northward to Cabo Rojo south of Tampico, discovered a large river emptying into the Gulf and named it Rio Grande de Pdnuco. Besides the surveys of the coast from Cape Catoche to Tampico, Alaminos' principal con- tribution to the exploration of the Gulf was the discovery of a free passage between Florida and Cuba which represented the shortest route for Spanish vessels carrying silver from Mexico to Europe. In 1519 Francisco de Garay, Governor of Ja- maica, sponsored an expedition of Don Alonzo Alvarez de Pineda to explore the northern coast of the Gulf. Four ships provided by Garay sailed from Jamaica toward Florida. Believing that Florida was an island, Pineda followed the west coast looking for a passage and, not finding it, turned west along the northern coast of the Gulf. In the course of his exploration he discovered the mouth of the Mississippi River which he called "Rio del Espiritu Santu" and described the body of water east of the delta as "Mar Pequena" or a small sea, the name of the present Mississippi Sound which persisted on many charts for nearly two centuries. Pineda noted the physiographical character of the shoreline, recorded the positions of dunes, low-lying sandspits, bays, knolls, marshes, and oyster banks {ostiales) which abounded in the Mississippi Sound and in the delta of the Missis- sippi River. He realized that the majestic fresh- water stream which he ascended for several miles must originate on a large land area, and other observations convinced him that he was exploring the coast of a great continent. Although the majority of writers agree with Hari'isse (1900) that the river Pineda named Rio del Espiritu Santu is the present Mississippi River, there are others who think that the de- scription of the country given in his reports does not agree with that of the mouth of the Mis- sissippi and that Pineda's expedition actually was in Mobile Bay (Scaife 1892). This question probably never will be answered with complete certainty. As a result of his explorations Pineda produced several new maps showing, with ap- proximate accuracy, the outlines of the Gulf coast. Only one of them, bearing the title "Traza GULF OF MEXICO 13 de Costas de Ticrra Firme y las Tierras Nuevas," was published. The original, datod 1521, is in the Archive General de Indias, in Seville, and its reproduction is given by Navarrettc (1837) and Winsor (1884, v. 2, p. 218), In 1521 the west coast of Florida was revisited by Ponce de Le6n, who landed probably in Char- lotte Harbor where he was seriously wounded in a battle with Indians. He died within a few days, after being taken back to Cuba. This expedition added nothing to the progress of geo- graphical knowledge of the Gulf, The next attempt to conquer Florida and ex- plore the northern part of the Gulf was made by Panfilo de Narvaez, who had distinguished himself in the conquest of Cuba under Velasquez and was at the head of an expedition sent by the Spanish Goverimient to compel Cortes to relinquish his command in Mexico, His defeat and imprison- ment by Cortes did not reflect on his reputation, and upon returning to Spain he obtained from Charles I a grant to colonize a vast expanse of land from Florida proper as far west as Rio Panuco, On June 17, 1527, five ships under the command of Narvaez sailed from San Lucas, Spain, with 600 men and officers aboard. One of his com- panions was Cabeza de Vaca, the treasurer of the fleet. After leaving the south shore of Cuba in March 1528, the ships, driven north by strong winds, found shelter in a large bay which the Spaniards called Bahia de Santa Cruz. Ac- cording to the description given by Cabeza de Vaca, the bay extended from 7 to 8 leagues inland, had many islands, and presented an excellent anchorage with a depth of water of about 6 fathoms. There is no doubt that it was the present Tampa Bay. Misinformed by Indians that the land north of the bay, known as Apalachee, was rich in gold, Narvaez marched overland with 300 officers and men while his ships under the command of Miruelo followed the northern direction along the coast. The rendezvous was supposed to be in a bay north of the point of their departure. In about 2 months, Narvaez's column reached the village of Apalachee where with great difficulty the men found only a few bushels of corn. Trying to establish contact with the ships, Narvaez turned south and discovered a river, Rio de Magdalena, as the Spaniards called it, which probably cor- responds to the present Apalachicola River, The party suffered many hardships in the swamps of this region, and many men perished of exhaustion and disease. Failing to contact the ships, Narvaez decided to march west rather than to return to Tampa Bay, On the shores of a bay, which probably corresponds to the present St, George Sound and which was named Bahia de los Caballos, the Spaniards were compelled to slaughter their last horses to make crude boats of their skins, and sailed westward. They followed the shoreline, entering different lagoons (Pensacola, Santa Rosa, and others). In November they reached a bay with many islands (probably Chandeleur Sound in the Mississippi Sound), Since the water was fresh they realized that thej' were near the mouth of a great river which they attempted to enter, but strong wind and current drove them into the sea where Narvaez perished in the storm. His companion, Cabeza de Vaca, found refuge on a small island 5 leagues long and 2 leagues wide which he named Isla de Malhado. The place may be Ship Island, Horn Island, or some other island in the Mississippi Sound, Scattered by the storm, most of Narvaez's men perished. With a few men, Cabeza de Vaca succeeded in landing on the mainland, where for 6 years he lived among the Indians. In 1533 he gave up hope that any European ship would visit the coast and with Lope Oviedo decided to march westward. Encountering a few small streams they came to the banks of a very large river which they considered to be Rio del Espiritu Santu (Mississippi River), and after crossing it marched for a long time through Texas until they reached the Bay of California. In 1536 Cabeza de Vaca returned to Europe where the results of the unfortunate expedition became known. Its principal scientific achieve- rnents can be briefly summarized as follows: The Mississippi River was seen for a second time; Tampa Bay was more fully explored, and new names, such as Apalachee Bay, were added to geography. After waiting in vain for Narv&,ez at the place of rendezvous, Miruelo returned with his ships to Tampa Bay. It is interesting to note that, al- though he failed to reach the bay at the north coast of the Gulf where he was supposed to meet Narvaez, the name of Bahia de Miruelo 14 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE appeared for many years on the charts in the place of the present Apalachee Bay. Shortly after the tragic end of the Narvaez expedition, Fernando de Soto, a Spanish captain and explorer, was preparing for a new adventure. De Soto acquired a large fortune from the con- quest of the Inca Empire in Peru in which he played a prominent role. He obtained from Charles V a commission as "Adelantado" of the lands of Florida and Governor of Cuba and invested his large fortune in a new adventure. On May 18, 1539, seven ships comprising De Soto's flotilla carrying 700 soldiers, 200 horses, mules, supplies, and materials, sailed from Havana. On May 25 they reached Tampa Bay, known as Bahia de Espiritu Santu. From Tampa Bay, De Soto with a large detachment of horsemen and foot soldiers went by land to Apalache. One of his companions, Juan de Anasco, a prominent seaman, cosmographer, and astronomer was en- gaged in making scientific observations during this military expedition. After reaching the land north of Apalachee, De Soto despatched Anasco south to find a harbor. During this travel the party discovered the bones and other remains of Narv^ez's men, and coming finally to the shores of the sea discovered a large bay which they called Bahia de Ante (present Apalachee Bay). In January 1540, De Soto ordered Captain Diego Maldenado to sail for 100 leagues along the coast to take records of all the bays, harbors, and rivers and to return in 2 months. In the course of this survey Maldenado found a bay 60 leagues west of the Bay Aute which he described as the most beautiful harbor in the world ("un hermosis- simo puerto"), protected against all winds. He named it Achusi. The entire harbor was sounded with great detail, for De Soto wanted to use it as a rendezvous and a base for his operations. De- tailed descriptions made by Maldenado leave no doubt that Achusi corresponds in every respect to the present Pensacola Bay. After exploring the east coast of the American continent as far north as the Savannah River, De Soto returned to the Gulf and in October 1540 investigated the place called Mavill or Mauvill which is the present Mobile. His further ex- plorations lead him inland and westward to the banks of the Mississippi which he crossed at Chickasaw Bluffs near the present location of Memphis, Tennessee. In 1542 he died and was buried at the bottom of the Mississippi River. Before his death he ap- pointed Luis de Moscozo de Alvarado as his successor. After many vicissitudes the Spaniards, under the leadership of their new chief, constructed several boats in which they sailed down the river, successfully evading the pursuit of Indians. Upon reaching Gulf waters they turned westward with the hope of landing somewhere on the Mexican coast. All navigation instruments were lost when the Indians burned the Spanish camp at Mobile, but one astrolabe was saved by Aiiasco. Being a careful and resourceful man, he managed to make a sea chart from a parchment of deerskin, and with a forestaff, made from a ruler, and an astrolabe salvaged from the fire at Mobile, at- tempted to guide the course of the flotilla. His worthwhile efforts were so much ridiculed by the other seamen because Anasco had never before embarked on any other maritime expeditions, that in disgust he threw his instruments, except the astrolabe, into the sea. One day, because of bad weather, the ships sought refuge in a small cove. While some of the Spaniards were gathering shellfish along the shore they foimd some slabs of black bitumen almost like tar which the ocean had cast upon the beach. Garcilaso, who tells this story (Garcilaso de la Vega, Vamer's translation, 1951, p. 601), says, "This substance must come from some spring which flows into the sea or which is born in the sea itself. The slabs weighed 8, 10, 12, and 14 pounds; and they were found in quantity." The tar-like substance was successfully used by the Spaniards to repair the leaky vessels, and after spending a few days on the shore they continued westward. This is probably the earliest reference to the finding of asphalt along the Gulf coast. After many days of sailing along the coast line Moscozo entered the mouth of the Panuco River and landed in Mexico.^ The discovery of Pensacola Bay, exploration of the delta of the Mississippi River and of the northern coast of the Gulf, and the convincing evidence that the Mississippi was a mighty stream draining from a large continent, were the principal scientific contributions of the De Soto expeditioh. ' Detailed account of De Soto's expedition can be found in the report of the U. S. De Soto Commission (1939). GULF OF MEXICO 15 Its unliappy completion marked the end of the period of the earliest explorations in the Gulf. Sbcteen years after the return of Moscozo a Spanish conquistador, Don Tristan de Luna, organized a new expedition to the Gulf. This expedition contributed little to the science of geography. By this time Spain's interest in the new land across the ocean and the enthusiasm of her rulers for new explorations and colonization of the New World somewhat slackened. Although the great advantages derived from the possession and colonization of the newly dis- covered territories were fully appreciated by the Spanish Government and by the educated class of the Spanish nation, the country lacked ability and resources to develop them. At the same time, the Spanish Government jealously watched the efforts of other nations to establish themselves in the New World. It tried by every means to prevent French colonization of the country sur- rounding the Gulf of Mexico and did not hesitate to send military expeditions to destroy French colonies. The results of many expeditions in the Gulf conducted during the first half of the sixteenth century provided the cartographers with new, reliable material for the construction of new maps, and consequently, the outlines of the Gulf shown by them in their drawings began to assume more or less correct configuration. This can be noticed, for instance, by examining figure 5, representing Mercator's map of 1538, in which for the first time the name America was applied to the entire western continent. It may be of interest at this point to make a brief survey of the geographical names which were given to the Gulf of Mexico. No special name for the Gulf is found on the map of Juan de la Cosa of 1500 or the Waldseemiiller map of 1507, al- though in both of them the location of the Gulf is clearly shown. Cortes, in his despatches, referred to the Gulf as Mar del Norte, while the names Golfo de Florida and Golfo de Cortes are found in the writings of other explorers. The name Sinus Magnus Antilliarum appears on an old Portuguese map made in 1558 by Diego Homen (original in British Museum). Probably the most remarkable name is that of Mare CathajTium (Chinese Sea) which is foimd on one chart of the middle of the sixteenth century (copy reproduced in the Memoirs de la Societe de Nancy, 1832). In 1550 the name Golfo de Mexico appears for the first time on the world map the original of which, according to Kohl, is in the Bodleian Library in Oxford. Earlier Spanish geographers used, also, the name of Golfo de Nueva Espana. Herrera (1728) called it Ensenada Mexicana and Seno Mexicano, the names which persisted in Spanish admiralty charts until the eighteenth century. The present name, the Gulf of Mexico, and the corresponding names, Golphe du Mexique in French and Golfo Mexicano in Spanish, appear to have been in use since the middle of the seventeenth century. During the latter half of the sixteenth century the French Huguenots, trying to escape religious persecution in Europe, made many attempts to establish colonies in Florida. Their efTorts were primarily directed to the east coast of Florida where the French penetration lead to many bloody encounters with the Spaniards. Probably the most significant French contribution to geo- graphical knowledge of this time was Le Moyne's map of Florida. Jacques Le Moyne de Morgues was an artist who accompanied a French expedi- tion to Florida under Laudonniere in 1564. His map shows only a part of the Gulf of Mexico east of the Mississippi River. Since it is known that French observations were limited to the east coast of America between the point south of St. Augustine and Rio Jordedan (Charleston Harbor) in the north, the rest of the map was obviously borrowed from Spanish sources. The names of many places are corrupted as, for in- stance, Apalache Bay is indicated as Sinus Morquel, corrupted from the Bay of Miruelo, and the Bay of Ponce de Leon (Tampa Bay) is called Sinus Joannis Ponce. This map, published by De Bry in 1591 after the death of the artist, was for 50 years copied by Dutch and French cartog- raphers but was completely ignored by the Spaniards. Le Moyne produced, also, a series of extraor- dinarily interesting drawings depicting the home life, habits, methods of hunting, and cere- monies of the Timucua Indians. Excellent repro- ductions of these illustrations together with a translation of the Latin text of De Bry were published in English (Le Moyne, 1564, ed. 1875) and some of the drawings are reproduced by Swanton (1946, tables 51, 53-57, 81, 82, 85, 87, and 106). Examination of these illustrations gives an insight into the tribal life of Florida 16 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE o O >. « 3 o GULF OK MEXICO 17 Indians as it was inter reted by a French artist. Particularly amusing are the scenes of alligator hunting in wliich the beast exceeds many times its normal size and the peaceful scene of the Timucua Indian women sowing their fields, the latter drawing conveying a bucolic atmosphere in conformity with the prevailing artistic taste of that time. No significant advance in geographical knowl- edge of the Gulf was made during the latter part of the sixteenth and the first half of the seven- teenth century. In this period Spanish ships loaded with gold and silver continued to sail from Mexico to Havana following the northern coast of the Gulf ami passing the delta of the Mississippi River which was called Cabo de Lodo, or Mud Cape. The names of the earlier discoverers, such as Pineda, Narvdez, Ponce de Le6n, De Soto, and others whose exploits made possible the relatively safe sailings of these ships, were almost forgotten. During the last quarter of the seventeenth cen- tury -a new era of explorations was initiated by French adventurers who attempted to reach the Gulf coast from the north in order to establish there new colonies. In 1673 two French explorers, Louis Joliet and Father Marquette, descended the Mississippi River from Lake Michigan and voyaged south to the mouth of tiie Arkansas River. In 1682 La Salle entered the Mississippi by way of the Illinois route, explored the river to its mouth, and in the name of France took possession of its entire drainage basin. Seeing great political and economic advantages in establishing a colony at the mouth of the Mississippi River, he obtained support of the French Government and in 1684 sailed from Europe with four ships, one of which was shortly captured by Spaniards. La Salle missed the mouth of the Mississippi River and landed farther west in Matagorda Bay, Texas, where he established his colony. Misfortunes, disease, and death so devastated the ranks of the colonists that in a few years only 45 survivors remained from several hundred who comprised the original party. In desperation. La Salle decided to reach Canada by land and during this journey was assassinated by his men. One of the results of La Salle's exploration, which is of definite interest to the geography of the Gulf, is the sketch map of the location of his camp on the shores of Matagorda Bay with the soundings sliown in feet. The reproduction of this map, in tlie form of a tracing from a photo- graph of the original, is given by Dunn (1917, p. 33). Rumors of the French penetration in the land bordering the Gulf aroused the half-dormant rivalry between Spain and France and induced the Spanish Government to send several military expeditions with orders to destroy French colonies. As one of the official documents of that time stated, it was necessary to "desarraygar esta espina que se a yntroducido en el corazon del cuerpo de la America" which means to uproot the thorn that had been thrust into the heart of America (Dunn, p. 42). In 1686 Martin de Echegaray, a naval captain of the presidio of St. Augustine, Florida, attempted to interest the Spanish Government in strength- ening Spanish influence in the domain of Florida by transporting 50 Spanish families from the Canary Islands and 25 Indian families from Cam- peche. In support of his plan, Echegaray sub- mitted a map, wdiich is a good example of the defects of the geographical knowledge of that time, of the interior of the American continent. The Echegaray map shows the large "river Canada," or St. Lawrence River emptying into a lake from which two rivers lead southward to the Gulf of Mexico, both emptying into Espiritu Santu Bay (Mississippi River). Echegaray's scheme was not accepted, but the Spanish Gov- ernment took other measures to counteract the French penetration into the new continent and to destroy La Salle's colony of which they were afraid. An interesting account of these attempts is given by Dunn (1917). It is sufficient to men- tion here that not less than four maritime ex- peditions were sent by the Spanish Government, and the whole Gulf of Mexico was examined with great diligence. One of the important results of this search for French colonies was the rediscovery of Pensacola Bay which the Spaniards decided to occupy. Admiral Pez was placed in command of an expedition organized for this purpose in 1693. One of his principal companions was Dr. Carlos de Siguenza y Gongora, professor of mathematics in the Royal University of Mexico and chief cos- mographer of the kingdom. Siguenza kept a detailed journal of the journey in which he re- corded his observations. The vessels of the expedition reached Pensacola Bay on St. Mary's 18 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Day, August 14, 1693, and following their custom, the Spaniards immediately renamed it "Bahia de Santa Maria de Galve," the last name being added to the holy name of the Virgin in honor of the viceroy of the territory. Siguenza made a detailed survey of Pensacola Bay and described its configuration, depth, islands, and rivers. The expedition proceeded farther east and after some difficulty entered Mobile Bay, made soundings in the channel, and found that the depth was only 20 "palmas." As a result of Siguenza's observa- tions strong recommendations were made to oc- cupy Pensacola, but a final order for this action was not issued until 1698. Rivalry among the western European powers in establishing a foothold on the shores of the Gulf of Mexico greatly enhanced the geographical knowledge of the region. As a military necessity the whole northern coast of the Gulf, with har- bors, rivers, and lagoons, was surveyed; fairly accurate navigational charts were prepared; and information was accumulated regarding the pre- vailing winds and currents. In this way marked progress was attained in the cartography of the Gulf and adjacent coastal lands. EIGHTEENTH CENTURY At the beginning of the eighteenth century sailing vessels of European powers engaged in trade or in pursuit of military designs continued to traverse the waters of the Gulf in ever in- creasing numbers, but the era of ambitious ex- peditions and daring adventures, which in the past fired public enthusiasm, was over. As a matter of routine the ships made astronomical observations and determined the longitude and latitude of the places already known, surveyed the harbors and passes, made numerous soxmd- ings, and recorded the direction and velocities of winds and currents. These navigational data were eagerly sought by the cartographers to be incorporated in new maps, numbers of which ap- peared in various European countries and in Mexico. Examples given below, which illustrate this progress, have been selected from a large array of the cartographic material issued during this period. French interest in the Mississippi River and the surrounding country is clearly expressed in the work of the famous French geographer, Guillaume Delisle (in the French publications the name is spelled "de L'Isle" and "Del'Isle") whose chart of Louisiana and of the course of the Mississippi was composed in 1719. The inscription reads that it was drawn after consulting many memoirs of Le Maire and others. The map shows the routes of De Soto and of other explorers and depicts the course of the principal rivers. The name Texas (Los Teijas) for the first time appears in cartography. According to Kohl (1857, No. 238), the Delisle map is "the mother and main source of all the later maps of the Mississippi and of the whole West of the United States." The entrances to the Mississippi River, being of great importance to the French mariners, were surveyed with great persistency. Among the many persons who contributed to our knowledge of the physiography of the river, Lemoyne de Serigny occupies a prominent position. In 1719 he participated in military operations in Florida and Louisiana and led a successful attack from the sea against Pensacola. His observations along the northern part of the Gulf coast are incorporated in a map drawn by an anonymous French cartographer and entitled "Carte de la cote de la Louisiane depuis I'Embouchure du Mississippi jusqu' a la Baie de St. Joseph, etc." The Library of Congress has a photographic reproduction of this document. The original is in Paris in Dep6t de la Marine. Serigny produced, also, a detailed map in colors of the approaches to Pensacola Bay. The notation on the body of the latter map contains reference to a strong surface current and the rise and fall of tides approximating 3 feet during a 24-hour period. In connection with the construction of fortifica- tions around the recently founded city of New Orleans, the French Government detailed many engineers to Louisiana. Among them Bernard de la Harpe distinguished himself by numerous observations which were incorporated in the de Beauvilliers map of 1720. The map shows many streams, mountains, towns, and Indian villages along the Gulf of Mexico and many islands off the coast of Yucatan. The chart of the Louisiana coast drawn about the same time (1719-20) by Devin was also made on the basis of the reports of De la Harpe and other French army officers. It shows many soundings and the positions of shallows and reefs in St. Louis Bay and adjacent waters. The necessity of having accurate maps for safe GULF OF MEXICO 19 navigation along the coasts of America was fully recognized in England. Among tlie many charts published tliere chiring the first half of the eighteenth century that of Henry Popple, issued in 1733 on 20 sheets with an index, is of particular interest. This large chart, measuring 232 by 239 centimeters has the following title: "A Map of the British Empire in America with the French and Spanish Settlements adjacent thereto." A prospectus attached to the first impression con- tains a detailed description of the map. The Librarj' of Congress has three impressions, one of which is imperfect. About the middle of the eighteenth century the Spanish Government, feeling the need for more accurate information regarding the extent of its dominions in the New World, demanded by the royal decree of 1741 the submission by local authorities of detailed suveys of their adminis- trative districts. Data thus obtained were summarized by Don Jose Antonio de Villasenor y Sanchez, Auditor General of the Department of Quicksilver, who enjoyed a reputation as a "distinguished mathematician, accurate historian, and a good citizen" (Bancroft, 1883-86, v. 3, p. 510). The entire undertaking resulted in the map issued in 1746 under the title, "Icomismo hidro- terro 6 Mapa Geographico de la America Sep- tentrional" (original in Arch. Gen. de Indias, Seville ; copy in Library of Congress) . In the same year the Spanish Government detailed Fernando Consag to explore the upper part of the Gulf coast. A reproduction of his map is given by Bancroft (1883-86, v. 1, p. 463). Jacques Nicolas Bellin, an engineer of the French navy, was probably the most outstanding cartographer of the second half of the eighteenth century. In carrying out official orders of the French Govermnent he made a detailed survey of the coast of Louisiana and of the course of the Mississippi River, drew a plan of Pensacola Bay (1742), published marine atlases and many maps (BeUiu 1749, 1755, 1764). His map of the Gulf of Mexico and of the islands of America, issued in 1754 and published in volume 12 of Prevost's Histoire generale des voyages (1746-89, pp. 8-9), illustrates the state of geographical knowledge of that time. One can see from this map (fig. 6) that the configuration of the Gulf, especially along its west coast, is still incorrect, and the shape of the Florida Peninsula is far from being true. 250D34 0—54 3 In this respect, as well as in the manner of drawing and the angularity of the coastal line, BcUin's map resembles the one prepared by liis predecessor, Royal Cartographer D'Anville, in 1731 (fig. 7). Although the outlines of Florida are almost identi- cal in the two maps, it is interesting to note that Bellin does not show such a fantastic array of bays and sounds as are indicated in the southern- most part of Florida by D'Anville. One of the most notable documents of the second half of the eighteenth century is a map of the British and French dominions in North America published in London by John Mitchell in 1775 in accordance with the Act of Parliament (Mitchell 1755, 1757). The original of one of the earlier issues, identified by only one insert (Hudson Bay) instead of four in the later editions, can be found in the library of Harvard University. A copy of a French edition of 1756 is in the Library of Congress. Mitchell's map was first used by American and British diplomats at the Paris peace conference of 1782-83 after the surrender of Cornwallis at Yorktown. Since that time it had been referred to and quoted as an authentic document in many boundary disputes between the United States and European countries. The Harvard University copy has an interesting quotation from John Adams attached to the map which reads as follows: "We had before us ... a variety of maps but it was the Mitchell's map upon whicli was marked out the whole boundary lines of the United States." The map shows only a small section of the northern part of the Gulf of Mexico between longitudes 83°4' and 97° W. and latitudes 28°20' and 30°20' N. Tampa Bay is still called Baia del Espiritu Santo, and there are interesting notations regarding the depth of the water "20 feet water over the Bar of Pensacola the Chief Harbour hereabout" and the depth of "Y* Missisipi" stated to be "18 feet water into Balise, 12 feet over the Bar, 45 feet within, 50, 60, and 100 afterwards." In 1764-71 George Gauld ordered by the British Admiralty to make a survey of the coast of the provinces of West Florida and Louisiana, produced a map known as "Admiralty Chart." He also gave accounts of his surveys of Florida and sailing directions in the West Indies and Florida Keys (Gauld 1790, 1796). Several edi- tions of Gauld 's maps were issued in the United 20 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE GULF OF MEXICO 21 :;^} .^ -.-1 'K' <■■ K2t^ ^J^C^ \" ^s ^\^i-: 4* ■•■'/ ^■■] ' /:^.:\, i (1*1' ;;^. ^ H • >-■*■ r^:: .1 • lAj, V \ ^^'•.jt .:i ■' li'- ?■ i ? • ). ) : y. - H I ;• „■>.- illy 4- 03 •a is 03 3 C 03 x: o 03 ^iffi^ir,^^ GULF OF MEXICO 25 line explorations by authorizing the President to "cause a survey of the coast of the United States and to employ proper persons in accomplishing the purpose prescribed in the act," for which a sum not exceeding $50,000 was appropriated. From 1816 to 1843 the reports of the Superin- tendent of the United States Coast Survey, made in compliance with this act, contained no references to the work in the Gulf of Mexico. Some explorations in the Gulf were conducted, however, by the United States Navy. In 1839 the U. S. S. Vandaiia, under the command of Uriah B. Levy, was engaged, from February 4 to August 3, in the hydrographic exploration between Galveston and the southwestern pass of the Mississippi River.^ The reconnaissance survey of the Gulf coast was commenced by the United States Coast Survey in January 1845 (Report of the Super- intendent for the year ending November 1846), and since that time the work of the organization, renamed in 1878 United States Coast and Geodetic Survey, is being continued at the present time. A large number of hydrographic and topographic charts issued during this time show the high degree of perfection achieved by this agency during more than a century of continuous work. The years of different surveys made in various sections of the Gulf can be found in the Hydrographic Index Charts, Nos. 80-91, and Topographic Index Charts, Nos. 20-32, issued by the United States Coast and Geodetic Survey. The main features of the Gulf — the configura- tion of its bottom and the circulation of water and its emergence as the Gulf Stream — were the ob- jects of many investigations. The exploration of the Gulf Stream was commenced in 1844 by Davis (Report of the Superintendent, U. S. Coast Sur- vey, year ending November 1846) and was continued by Bache in 1846, who inaugurated a series of deep-sea investigations of the physical problems connected with the Gulf Stream (Bache 1852, 1859). This work was expanded by his successors in the United States Coast Survey, Benjamin Price, Carlile P. Patterson, and Julius E. Hilgard. The results of the Gulf Stream ex- plorations, including observations of distribution of water temperatures in the Florida Channel ' Copy of the chart of the cruise of the Vandaiia is in the Library of the American Geographical Society of New York. and Straits, were discussed by Bache in several articles (Bache 1854, 1860). In 1850, at the recjuest of the United States Coast Survey, Professor Louis Agassiz undertook an extended biological survey of Florida reefs and obtained valuable information concerning the topography of Florida, the mode of formation of reefs by cementation, and the origin of the Florida Keys (L. Agassiz 1880). Occasional references to bottom animals of the Gulf are found in French publications of Folin and Perier (1867-72), in which are described several new species of mollusks and ostracods from the bottom deposits collected near Veracruz and in Laguna de Terminos. Maury's (1858) classical book on the physical geography of the sea contains no specific reference to the Gulf of Mexico except a brief note con- cerning the corrosive action of Gulf waters, which were observed to be more destructive to copper sheeting of ships than the water from any other part of the world. Systematic deep-sea explorations carried out in 1867 and 1868 by Pourtales and Mitchel on the United States Coast Survey ships Corwin and Bihh consisted in dredging between Florida and Cuba, at some places at a depth of 850 fathoms. Many new types discovered in these collections and the finding of species of corals and echinoderms which were considered related to an antique fauna of the Cretaceous period, proved that a study of bottom organisms thriving along the course of the Gulf Stream is of great scientific interest (Pour- tales 1867; L. Agassiz 1852; A. Agassiz 1888, V. 1, p. 49; Peirce and Patterson 1881). Explorations along the west coast of Florida undertaken in 1872 by Commander Howell were continued in 1875-78 in other parts of the Gulf under the direction of Lieutenant Commander Sigsbee aboard the United States Coast Survey steamer Blake. In the following years the opera- tions were extended, under the command of Commander Bartlett, through the Caribbean Sea and the Straits of Florida. Alexander Agassiz, in charge of dredging operations of the Blake expedition, made a geological study of Florida reefs which had already attracted the attention of his father, Louis Agassiz, Le Conte, and Hunt (A. Agassiz 1888, v. 1, pp. 52-92).* < The geology of the Gulf of Mexico is discussed in an article by S. A. Lynch in this book, pp. 67-86. 26 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Three cruises of the Blake, from 1877 to 1880, represent an outstanding event in the history of scientific explorations of the Gulf of Mexico. The expeditions obtained a wealth of information re- garding the oceanography and biology of the Gulf, and the two volumes describing the work of the Blake written by A. Agassiz (1888) until the present day remain an important source of refer- ence concerning the bottom fauna, the structure and origin of coral reefs, and the distribution of invertebrates and fishes at depths extending to 2,000 fathoms. Collections obtained by the Blake served as material for many important publications on corals, antipatharians, crinoids, and Crustacea (Pourtales 1870, 1880) ; echinoderms (A. Agassiz 1863, 1869, 1878, 1883); hydroids (Clarke 1879); annelids (Ehlers 1879) ; mollusks (Dall 1880, 1886, 1889) , and many others. Numerous papers dealing with various taxonomic groups gathered by the expeditions can be found in the first 19 volumes of the Bulletin of the Museum of Comparative Zoology at Harvard College. A discussion of the deep-water fauna of the Gulf Stream was given by Pourtales (1863-69). The establishment, in 1871, of the United States Commission of Fish and Fisheries marked the beginning of the study of the important coastal and marine fisheries of the Gulf. With the building of the 1,000-ton steamer Albatross in 1883, the first Commissioner of Fisheries, Spencer F. Baird, initiated worldwide explorations of the sea fisheries. At the time of her completion, the Albatross was the best equipped dredger for deep- sea work in existence. One of her first details was to explore the bottoms of the Gulf of Mexico. The instructions given in 1883 by Spencer F. Baird to the commanding officer. Lieutenant Commander Z. L. Tanner, read in part as follows: "In returning (from the Caribbean) by way of Cape San Antonio it will be well to make a run into the Gulf of Mexico and spend a short time in making soundings and dredging therein, for the purpose of obtaining a general idea of the natural history and the fisheries of the Gulf, preliminary to a more lengthened visit to be made hereafter" (Tanner 1886). The instructions specified that in addition to the purely physical work, soundings, temperature, and observation of currents, the Albatross should secure "a fair representation of the shore fauna of the Caribbean Sea and its surroundings including shallow water, to collect parasites of the larger fish, birds, reptiles, fresh- water fish, and the various species of mammals as well as to obtain aboriginal relics in the way of articles of stone, pottery, etc." Large collections made by the Albatross and deposited in the Smithsonian Institution testify that the instruc- tions were faithfully carried out. During the first visit to the Gulf in 1884 the Albatross explored the bottoms around the west- ern tip of Cuba (fig. 10, open squares) but return- ing in the following j'ear made more detailed explorations around Cozumel Island, along the eastern edge of Campeche Bank, on red-snapper banks off Cape San Bias in the northeastern part of the Gulf, and occupied a few stations along the west coast of Florida and at Key West (fig. 10, black double circles). A brief but interesting account of the history of the Albatross is given by Hedgpeth (1945, 1947). Simultaneously with the oceanographical stud- ies the United States Fish Commission conducted an exploration of the fishery resources of the Gulf of Mexico. Accounts of this work with reference to red snappers, shore seine fishery, oysters, and sponges are given by Stearns (1884, 1887), Collins (1887), and Stearns and Jordan (1887). In 1880 the United States Commission of Fish and Fisheries built a steamer. Fish Hawk, for the purpose of assisting in fish-hatching operations and conducting surveys of fishing grounds. From November 1895 to 1896, under the command of Lieutenant Franklin Swift, the Fish Hawk sur- veyed oyster regions of St. Vincent Sound, Apala- chicola Bay, and St. George Sound, Fla. (Swift, 1897), the work which 20 years later was repeated with the same ship by Danglade (1917). In 1898 the Fish Hawk was used by the United States Coast and Geodetic Survey in hydrographic in- vestigations of the inshore waters of Alabama. In 1901 and 1902 the ship was engaged in sponge investigations along the west coast of Florida. The exploration in 1901 covered the grounds be- tween Anclote Anchorage, St. Marks, and Tampa Bay. In the following year the operations ex- tended along the western coast of Florida, to the depth of 10 fathoms, from Cedar Keys to Key West. In 1905 the Fish Hawk was detailed to survey the oyster bottoms and make hydro- graphic investigations in Matagorda Bay, Tex. (Moore 1907), in 1911 made a similar investiga- GULF OF MEXICO 27 28 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE tion in Mississippi Sound (Moore 1913a, 1913b), and in 1913 was used as the base for a survey of oyster bottoms in Lavaca Bay, Texas (Moore and Danglado 1915). The completion of the latter investigation by Moore marked the ending of the Fish Hawk activities in the Gulf. In 1917 the research ship Grampus of the United States Bureau of Fisheries cruised over the con- tinental shelf from Key West to Aransas Pass in a study of shrimp and fishery grounds (U. S. Bureau of Fisheries, 1919). The results of systematic hydrographic work conducted by the United States Coast and Geo- detic Survey and the Hydrographic Office of the United States Navy with the additional data accumulated by other explorations served as a source of material for a general discussion of the physiography of the Gulf. Forshey (1878) at- tempted to describe the configuration of the bot- tom of the Gulf, stressing particularly the deposi- tion of sediments brought in by the Mississippi River which he believed eventually will fill up the Gulf. Lindenkohl (1896) summarized tem- perature and salinity data taken primarily from the reports of the United States Coast and Geo- detic Survey. In order to obtain basic data on physical ocea- nography of the Gulf a plan was adopted in July 1905 by the Hydrographic Office of the United States Navy to supply all vessels crossing the Gulf with a form for daily use in giving ship's position, direction and force of the wind, direction and force of the current, and temperature and color of the water. The reports of hundreds of observers extending over a period of years, when plotted on the montlily charts, agreed remarkably. The data were summarized by Soley (1914) on a chart entitled, The Gulf Stream in the Gulf of Mexico (see Pilot Chart of the North Atlantic Ocean for June 1914), reproduced in figure 11. Soley's chart shows the basin of tidal equilibrium (Sigsbee Deep) more than 2,000 fathoms deep in the western part of the Gulf, the direction of the main current, and the Gul Stream which comes from the North and South Equatorial Current in the Yucatdn Channel. The Northwestern Branch of the Current leaves the main stream at the northeastern corner of Campeche Bank, while the Eastern Branch turns eastward from the Yucatdn Channel. The chart shows, also, the two counter- currents, the Cuban and the Western, and the position of the Central Sea, a circular body of dead water about 80 miles in diameter. From the time of the first publication of Soley's chart basic information given in it is being incorporated in monthly pilot charts regularly issued by the Hydrographic Office of the United States Navy with the additional data supplied by ships and provided by the United States Weather Bureau of the Department of Commerce (formerly a part of the U. S. Dept. of Agriculture). In January-March 1914 Bigelow (1915), work- ing on board the United States Coast and Geo- detic Survey steamer Bache, made observations in the Straits of Florida studying vertical distri- bution of temperature and salinity from the sur- face to the depth of 1,800 meters along the profiles drawn across the Straits from Key West to Havana, from Cape Florida to Gun Bay, and from Jupiter Inlet to the northern end of Little Bahamas Bank. He noticed the banking up of cold water against Florida as a result of upwelling from deep layers on the left side of the channel and concluded that the cold, comparatively fresh water next to Florida is largely true abyssal water from the Gulf of Mexico. In 1926 the oyster bottoms in the bays along the coast of Texas were surveyed by Galtsoff (1931) with special emphasis on salinity distribu- tion in these bodies of water. From 1936 to 1939 a detailed work on the hydrography of Texas tidal waters was carried out by Collier (Collier and Hedgpeth 1950). The natural history of redfish and other sciae- nids on the Texas coast was studied by Pearson (1929) who pointed out the scientific importance in a study of the biological relationship between the Gulf and its inland waters. Marked advance in the knowledge of the hydrog- raphy of the Gulf was made in 1932 by the Yale Oceanogi-aphic Expedition of the Mabel Taylor sponsored by the Bingham Oceanographie Founda- tion. One of the chief problems of the investi- gation, formulated by the leader of the expedition. Parr (1935), was to study "the relationship between the waters in the region of the Straits (i. e., the area southward between the Yucatdn Channel and the Straits of Florida) and in the Gulf of Mexico proper." Such a study became highly desirable in view of Nielsen's (1925) objections against the purely two-dimensional picture of surface movements of water in the Gulf GULF OF MEXICO 29 83 3 T3 J2 O 03 V 3 O 3 o 30 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE of Mexico given in Soley's chart. The expedition occupied 87 stations (fig. 10, triangles) at which temperature and sahnity of water were recorded at different levels from surface to a depth of 3,000 meters (1,640 fathoms).^ In 1934 the Atlantis of the Woods Hole Oceano- graphic Institution occupied, from January to March, a series of hydrographic stations in Yucatdn Channel and the Straits of Florida, and in January to May 1937, jointly with the Bingham Oceanographic Foundation, made observations in the Caribbean Sea and Gulf of Mexico (Parr 1937a, 1937b). During the cruise of 1947, sponsored jointly by the Woods Hole Oceano- graphic Institution and the Geological Society of America, the Atlantis occupied 551 stations in the western part of the Gulf between Sigsbee Deep and the coasts of Louisiana and Texas. In 1951 observations were made by this ship at 240 stations. As a result of this work, combined with the data obtained by the United States Coast and Geodetic Survey, a very detailed map of submarine topography on the northwest quarter of the Gulf was issued by the Institution in 1951. In 1951 the Fish and Wildlife Service of the United States Department of the Interior initiated a comprehensive research in oceanography and fishery resources of the Gulf of Mexico. This work is carried on bj^ the U. S. S. Alaska and the U. S. S. Oregon, the latter ship being primarily concerned with the explorations of new fishing grounds. Material dredged by the Oregon and deposited in the U. S. National Museum in Washington proved to be of exceeding interest to zoologists, for it comprised many rare species which heretofore were represented only by iso- lated specimens. A steady growth of interest in marine biology in the United States during the last half century is reflected in an increase in the number of labora- tories or stations devoted to marine biological research in general, or to a study of specific problems of utilization and management of fishery resources. One of the earliest institutions of that type in the Gulf was the Gulf Biologic Station established in 1902 by the State of Louisiana at the mouth of Calcasieu Pass in Cameron, La. In 1910, by an act of the General Assembly, the Gulf station was merged with the State Conser- • For the discussion of Parr's work see article by D. F. Leipper. Physical Oceanography of the Gulf of Mexico in this book, pp. 119-137. vation Commission, and about 2 years later the property consisting of 10 acres of land and the building in which the laboratories were located reverted to the original donor, Judge Henry, and the operation of the laboratory ceased. During its brief existence the Gulf Biologic Station was concerned primarily with the biology and cultivation of oysters, scallops, and clams in Louisiana waters and in studj-ing the distribution and biology of local marine and brackish-water plants and animals. The contributions of the laboratory were published in 15 issues of the Bulletin of the Gulf Biologic Station issued from 1902 to 1910 and in 3 small biennial reports of the director dated 1906, 1908, and 1910. « Brief data regarding the founding of this station and its policy are given by Foote (1942). In June 1904, the Carnegie Institution of Washington, D. C, established a marine labora- tory at Loggerhead Key, Dry Tortugas, 68 miles west of Key West, Fla. The site was chosen because of the purity of the ocean water surround- ing the group of seven, small, sandy islands, the proximity of the Gulf Stream with its abundant life, the presence of rich coral reefs in Florida, and the absence of local fisheries which could have affected the undisturbed life of the sea. Despite adverse conditions due to the difficulties of regular communication with the mainland, hurricanes which frequently swept the Keys, and the short season of its operation (restricted to 3 summer months), the station was very productive in scientific research. Its work inaugurated and conducted under the inspiring directorship of the late Dr. Alfred G. Mayer, covered a very broad field of research in marine biology and general physiology. The 33 volumes of the Papers from Tortugas Laboratorj' contain many fundamental works dealing with a great variety of problems such as biology of coral reefs by Mayer, the physiology of Valonia cells by Osterhout, the metamorphosis of ascidian larvae by Caswell Grave, observations on color, habits, and local distribution of the fishes of Tortugas by W. H. Longley, ecology and geologic role of mangroves by H. J. Davis. Many other papers of permanent scientific value came from the institution, which more than any other laboratory contributed to our knowledge of the marine life of the Gulf. • I am grateful to Joel W, Hedgpeth for supplying the data regarding the Oulf Biologic Station. GULF OF MEXICO 31 American scientists interested in marine research were grieved to learn from the report of the direc- tor of the Carnegie Institution for 1939 of the discontinuance of the laboratory due to the •'relatively high cost of its maintenance." At the time of this action the Laboratory was receiving a modest annual grant of $12,000 which constituted about 0.8 percent of the total budget of the Carnegie Institution of Washington for that year. Brief mention should be made of the attempt of the United States Bureau of Fisheries to establish a fishery laboratory at Key West in 1917. Owing to the lack of funds for salaries and equipment the station never became functional and was abandoned in 1928. A small laboratory is maintained by Louisiana State University on Grand Isle. The laboratory is used every summer from June to July for teach- ing. Despite modest equipment and lack of modern research facilities a number of valuable scientific papers resulted from its operations which have enhanced our knowledge of the Gulf fauna. From 1935 to 1937 the United States Bureau of Fisheries maintained a temporary laboratory at Indian Pass in Apalachicola Bay, Florida, for the purpose of studying the biology of the oyster leech iStylochu~s inimicus) and other enemies of the oyster. Upon completion of this work (Pearse and Wharton 1938) the laboratory was abandoned in 1937 and the equipment transferred to the fisheries laboratory near Pensacola, Fla. The latter laboratory, established in 1937 primarily for shellfish research, is located on a small island in Santa Rosa Sound about 7 miles from Pensacola. The laboratory, with several auxiliary buildings, occupies the site of the abandoned quarantine station. It is equipped with running sea water and outdoor cement tanks for experiments on shellfish. The current work consists in ecological and biological research on oysters in Florida, Alabama, Mississippi, and Louisiana waters. The Marine Laboratory of the LTniversity of Miami was established in 1942 at Coral Gables, Fla., for research and teaching in oceanography, marine biology, conservation, and management of fishery resources. Its operations extend over the waters of the West Indies and the Gulf of Mexico. The laboratory maintains a station at Apalachicola for oyster studies and, as circum- stances require, establishes temporary head- quarters along the west coast of Florida. Principal research projects, some of which are sponsored by the United States Navj', deal with the circulation of water in the Gulf (Smith, et al., 1951), seasonal changes in the composition of plankton of Biscayne Bay and adjacent oceanic waters, red tide, sponge disease and sponge culture, physiology of fouling organisms, and many others. Several of the articles by the members of the laboratory staff appeared in the newly established Bulletin of Ma- rine Science of the Gulf and Caribbean and in the Proceedings of the Gulf and Caribbean Fisheries Institute founded by the laboratory. The Gulf and Caribbean Fisheries Institute represents an effort to integrate the work of oceanographers, biologists, economists, fishermen, and admin- istrators. It seems appropriate to point out here that the idea of preparing a digest of the existing literature on the biology and oceanography of the Gulf of Mexico originated at the Second Annual Session of the Institute and has materialized through the efforts of several members of this organization (Walford 1950). Several other institutions devoted primarily to the study of Gulf problems, were established in recent years. The Institute of Marine Science of the University of Texas in Port Aransas was founded in 1948 with a grant from the General Education Board and with funds provided by the Texas Agricultural and Mechanical Research Foundation. The Texas Game, Fish, and Oyster Commission established, in 1949, a marine labora- tory at Rockport, Tex. The Fish and Wildlife Service of the United States Department of the Interior has maintained, since 1949, a temporary laboratory for red-tide studies at Sarasota, Fla., and in 1950 established headquarters with lab- oratory facilities at Galveston, Tex., for the con- duct of oceanographical and biological studies of the Gulf. The Oceanographic Institute of Florida State University was established in 1949 with two seaside stations, one at Alligator Harbor and another at the mouth of the St. Johns River about 12 miles east of Jacksonville at Mayport, Fla., on the Atlantic coast. Research facilities of these stations, engaged primarily in teaching, are limited. Since 1947 the State of Mississippi has main- tained the Gulf Coast Research Laboratory at Ocean Springs, Miss., for instruction in zoologj' and botan}^ Recent oil-development activities in the coastal 32 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE area of the Gulf provided an opportunity to make continuous observations from fixed platforms erected several miles off shore. Analyzing these records, Geyer (1950) discovered that the salinity of water of the Louisiana coast at a distance from 5 to 6 miles from the shore undergoes seasonal variations ranging from 15 to 35 parts per thousand at 10 feet below the surface. Extensive investiga- tions of the hydrography of the inshore waters and the effect of crude oil and brine on aquatic life have been recently sponsored by the oil com- panies. Unfortunately, the results of these studies are not available to the public. The outlook for scientific investigations of Gulf problems appears to be bright. There are at present many laboratory and field facilities available at various scientific institutions located along the Gulf coast. Furthermore, Federal and State organizations show great interest in the research problems and are in a position to conduct or sponsor various oceanogi'aphic and biological projects. It is therefore reasonable to expect that the progress in our knowledge of the Gulf of Mexico will be rapid and productive. BIBLIOGRAPHY Agassiz, Alexander. 1863-69. Preliminary report on the echini and star- fishes dredged in deep water between Cuba and the Florida Reef by L. F. de Pourtalfes. Bull. Mus. Comp. Zool. Harvard Coll. 1: 253-308. 1878. II. Report on the echini by A. Agassiz, crinoids and corals by L. F. de Pourtalfes, and ophiurans by Theodore Lyman preceded by a bibliographical notice of the publications relating to the deep-sea investigations carried out by the U. S. Coast Survey. In: Reports on the results of dredging . . . Bull. Mus. Comp. Zool. Harvard Coll. 5 (fl) : 181-252, 10 pis. 1883. I. Report on the echini. In: Reports on the results of dredging ... by the U. S. Coast Survey Steamer Blake. Mem. Mus. Comp. Zool. Harvard Coll. 10: 94 pp., 32 pis. 1888. A contribution to American thalassography. Three cruises of the United States Coast and Geodetic Survey steamer Blake . . . from 1877 to 1880. Houghton, Mifflin and Co. and Bull. Mus. Comp. Zool. Harvard Coll., vol. 14 and 15. .Agassiz, Louis. 1852. Extracts from the report of Professor Agassiz to the Superintendent of the Coast Survey on the examination of the Florida reefs, keys, and coast. In: Report of the Superintendent of the Coast Sur- vey . . . ending November 1851. 32d Cong., 1st Sess., Senate, Ex. Doc. No. 3, pp. 145-160. Wash- ington. 1880. Report on the Florida reefs. Mem. Mus. Comp. Zool. Harvard Coll. 7 (1): 61 pp., 23 pis. Bache, A. D. 1852. Annual report of the Superintendent of the Coast Survey showing the progre.ss of that work during the year ending November 1851. 32d Cong., Ist Sess., Ex. Doc. No. 26, 559 pp. Washington. 1854. Notes on the Gulf Stream. Reprinted from Blunt's American Coast Pilot, 1854, pp. 47-53, fold. chart, 5 curves. 17th edition. 1860. . . . Gulf Stream explorations. Third memoir. Distribution of temperature in the water of the Florida Channel and Straits. Am. Jour. Sci. and Arts, 29: 7 pp., March. Bancroft, Hubert Howe. 1883-89a. History of Mexico, 1516-1887. Vols. 1-4. The History Co., San Francisco. 1883-89b. North Mexican States. Vol. 1. A. L. Bancroft & Co., San Francisco. Bellin, Jacques Nicolas. 1749. Observations sur la carte du golphe du Mexique, et des isles de I'Amerique, dressers au d^pot des cartes, plans, et journaux de la marine, en 1749. 17 pp. Paris. 1755. Remarques sur la carte de I'Amerique Septen- trionale, comprise entre le 28' et le 72« d6gr6 de latitude, avec une description gdographique de ees parties. Paris. 1764. Le petit atlas maritime; recueil de cartes et plans des quatre parties du monde. 5 vols. Paris. BiGELOw, Henry B. 1915. Explorations of the United States Coast and Geodetic Survey steamer Bache in the western At- lantic, January-March 1914, under the direction of the United States Bureau of Fisheries. — Oceanog- raphy. Rep. U. S. Comm. Fish. 1915, App. 5, 62 pp., 53 text figs., 1 chart. (Doc. 833, issued May 9, 1917). Bremer, Lavillb. 1940. Amichel. A narrative history of the Gulf coast. Gulf coast history and guide. Book one. To the closing of the French period. (Lithographed at the plant of the Photo-Lith Co., New Orleans.) 93 pp., illus., 6 maps. British Museum. 1884. Catalogue of maps: Accessions. W. Clowes and Sons, London. 1885. Catalogue of the printed -maps, plans, and charts in the British Museum. 2 vols. London. Brower, J. W. 1893. The Mississippi River and its source. Minne- sota Hist. Coll., vol. 7, 360 pp. Bry, Theodore de. 1591. Brevis narratio eorumquas in Florida .\mericae Provincia Gallis acciderunt. Frankfurt a. Main. Carranza, Gonzales Domingo. 1740. A geographical description of the coasts, har- bours, and sea ports of the Spanish West Indies . . . London. (Printed for the editor, Caleb Smith, in- ventor of the new sea quadrant.) GULF OF MEXICO 33 Clarke, S. F. 1879. Report on the Hydroida collected during the ex- ploration of the Gulf Stream and the Gulf of Mexico by Alexander Agassiz, 1877-78. Bull. Mus. Comp. Zool. Harvard Coll. 5 (10): 239-252. Collier, Albert, and Joel Hedgpeth. 1950. An introduction to the hydrography of tidal waters of Texas. Pub. Inst. Mar. Sci. 1 (2) : 125-194. Collins, J. W. 1887. Report on the discovery and investigations of fishing grounds made by the Fish Commission steamer Albatross . . . with notes on the Gulf fisheries. U.S. Comm. Fish and Fisheries, Rept. of the Commissioner for 1885, App. B, 89 pp., 10 pis. Washington. Dall, W. H. 1880. General conclusions from a preliminary exam- ination of the mollusks. In: Reports on the results of dredging .... by the U. S. Coast Survey steamer Blake. Bull. Mus. Comp. Zool. Harvard Coll. 6 (3) : 85-92. 1886. Report on the Mollusca. Part I. Brachiopoda and Pelecypoda. In: Reports on the results of dredging ... by the U. S. Coast Survey steamer Blake. Bull. Mus. Comp. Zool. Harvard Coll. 12: 171-318, 9 pis. 1889. Rep ort on the Mollusca. Part II. Gastropoda and Scaphopoda. In: Reports on the results of dredging ... by the U. S. Coast Survey steamer Blake. Bull. Mus. Comp. Zool. Harvard Coll. 18: 1-492, 40 pis. Danglade, Ernest. 1917. Condition and extent of the natural oyster beds and barren bottoms in the vicinity of Apalachicola, Fla. Rept. U. S. Comm. Fish., 1916, App. V, 68 pp., 5 pis., fold. map. Washington. Dunn, William Edward. 1917. Spanish and Frejich rivalry in the Gulf region of the United States, 1678-1702; the beginnings of Texas and Pensacola. Univ. Texas Bull. 1705, 238 pp., 1 fold, map., Jan. 20. Austin, Tex. Ehlers, Ernst. 1879. Preliminary report on the worms. In: Reports on the results of dredging ... by the U. S. Coast Survey steamer Blake. Bull. Mus. Comp. Zool. Harvard Coll. 5 (12): 269-274. FiSKE, John. 1892. The discovery of America, with some account of ancient America and the Spanish conquest. 2 vols., illus., 7 maps. Houghton, Mifflin and Co., Boston and New Yorlj. FoLiN, L. DE, and L. Perier. 1867-81. Les fonds de la mer. 4 vols. Bordeaux. Foote, Lucy B. 1942. Bibliography of the official publications of Louisi- ana, 1803-1934. No. 19 of American Imprints Inventory, Hill Memorial Library, Louisiana State University. FORSHET, C. G. 1878. The physics of the Gulf of Mexico and its chief affluent, the Mississippi River. Salem. Proc. Am. Assoc. Advance. Sci., vol. 26, August 1877, Nash- ville meeting. Galtsokf, Paul S. 1931. Survey of oyster bottoms in Texas. U. S. Bur. Fish., Inve.stigational Rept. No. 6, 30 pp. Washington. 1952. Early explorations in the Gulf of Mexico. Proc. Gulf and Caribbean Institute, 4th Ann. Ses- sion: 129-134. Garc'ilaso, de la Vega, The Inca. 1605. The Florida of the Inca. A history of the Adelan- tado, Hernando de Soto . . . Translated and edited by J. G. Varner and J. J. Varner, 1951. 655 pp. University of Texas Press, Austin. Gauld, George. 1790. An account of the surveys of Florida ... to accompany Mr. Gauld's charts. 27 pp., 1 map. London. 1796. Observations on the Florida Keys, Reef and Gulf ... to accompany his charts. 28 pp. London. Geyer, R. A. 1950. The occurrence of pronounced periodic salinity variations in Louisiana coastal waters. Jour. Mar. Res. 9: 100-110. Greenhow, Robert. 1849. Early discoveries of the Mississippi . . . DeBow, J. D. B., Ed. The Commercial Review of the South and West 7: 319-321. New Orleans. 1849. Second visit of the Spaniards to the mouth of the Mississippi. DeBow, J. D. B., Ed. The Commercial Review of the South and West 7: 321-322. New Orleans. Gulf Biologic Station. 1902-10. Bulletin of the Gulf Biologic Station, Nos. 1-15. Louisiana. Hakluyt, Richard. 1850. Divers voyages touching the discovery of America and the islands adjacent. Collected and published by Richard Hakluyt ... in the year 1582. Ed. with notes and an introduction, by John Winter Jones. Printed for the Hakluyt Society, 3 p. 1, CXI, 171, 6 p. London. Hakluyt, Richard. 1907-13. The principal navigations, traffiques & discov- eries of the English nation, made by sea or overland to remote & farthest distant quarters of the earth at any time within the compasse of these 1600 yeares. 8 vols. London, Dent. Hakluyt Society, The. 1850. Divers voyages touching the discovery of .\merica and the islands adjacent. Collected and published by Richard Hakluyt, edited with notes and an introduc- tion by John Winter Jones. CXI. 171 pp, index 6 pp. London. 1847-1899. Works. Vols. 1-100. London. Harkisse, Henry. 1895. Americus Vespuccius; a critical and documentary review of two recent English books concerning that navigator. 72 pp. B. F. Stevens, London. 1900. Decouverte et evolution cartographique de terr- neuve et des pays circonvoisins 1497-1501-1769. Essais de Geographie historique et documentaire. 420 pp. Henry Stevens, Son & Stiles, London. H. Welter, Editeur, Paris. 34 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Hedgpeth, J. W. 1947. The steamer Albatross. Scientific Monthly 65: 17-22. Hedgpeth, J. W., and W. L. Schmitt. 1945. The United States Fish Commission steamer Albatross. Am. Neptune 5 (1): 5-26. Hehrera y Tokdesillas, a. de. 1601. Historia general de las hechos de las castillanos en las Islas y Tierra Firme del mar oceano. 1725-26. The general history of the vast continent and islands of America . . . Translated into English by Capt. John Stevens. 6 vols. Printed for J. Batley, London. 1728. Historia general de las Indias occidentalis . . . Nueva impression enriguecida con lindas figuras y re- tratos. Amberes, J. B. Verdussen. 4 vols., pis., fold, maps. Also 1720 edition in 5 vols. Madrid. HuLBERT, Archer Butler. 1904-8. The Crown collection of photographs of Amer- ican maps, selected and edited by Archer Butler Hul- bert. 5 vols. The A. H. Clark Company, Cleveland, Ohio. Humboldt, Alexander von. 1836-39. Examen critique de I'histoire de la geographie du nouveau continent, et des progr&s de I'astronomie nautique aux 15"* et 16°"" sifecles. 5 vols., 4 fold, maps. Paris. Kerhallet, Charles-Philippe de. 1853. Manuel de la navigation dans la Mer des Antilles et dans le Golfe du Mexique. 2 vols., 3 fold. maps. Paris. Kohl, J. G. 1857. A descriptive catalogue of those maps, charts, and surveys relating to America, which are mentioned in vol. Ill of Hakluyt's great work. Washington. Kohl, J. G. 1862. A popular history of the discovery of America from Columbus to Franklin. Trans, from the German by R. R. Noel, 2 vols. London. 1863. Aelteste Geschichte der Entdeckung und Erfor- schung des Golfs von Mexico und der ihn umgebenden Klisten durch die Spanier von 1492 bis 1543. Zeit- schrift fiir Allgemeine Erdkunde. Vol. 15, pp. 1-40 and 169-194. BerUn. 1868. Geschichte des Golfstroms und seiner Erforschung von den Altesten Zeiten bis auf den gros.sen Ameri- kanischen Btirgerkrieg; eine Monographic zur ge- schichte der Oceane und der geographischen Enteck- ungen. 224 pp. Bremen. 1885. History of discovery and exploration on the coasts of the United States. Report Supt. U. S. Coast and Geodetic Survey, 1884, App. 19, pp. 495-017. Wash- ington. Lelewel, Joachim. 1852. Geographie du Moyen Age. Vol. 2, pp. 135-140. Bruxelles. Le Moyne, Jacques. 1564. Narrative of Le Moyne, an artist who accom- panied French expedition to Florida under Laudon- nifere. Translated from the Latin of de Bry, Boston, 1875, 15 pp. with 42 hehotypes of the engravings taken from the artist's qriginal drawings. Lindenkohl, a. 1896. Resultate der Temperatur-und Dichtigkeitsbeo- bachtungen in den Gewassern des Golfstroms und des Golfs von Mexico. Durch das Bureau des U. S. Coast and Geod. Sur., Petermanns Geogr. Mitteilun- gen 42: 25-29, map. Lowery, Woodbury. 1912. Descriptive list of maps of the Spanish possessions within the present limits of the United States, 1502- 1820. Edited with notes by Philip Lee Phillips, F. R. G. S., Chief, Division of Maps and Charts. Li- brary of Congress. The Lowery Collection. 567 pp. U. S. Govt. Printing Office, Washington. Madrid, Museo Naval. 1945. Catdlogo guia. 9th ed., 248 pp. Madrid. Maury, Matthew Fontaine. 1858. The physical geography of the sea. XXIV, 25, 274 pp. incl. map, 3d ed. Harper & Bros., New York. Mitchell, John. 1755. A map of the British and French dominions in North America. London. 1757. The contest in America between Great Britain and France . . . 260 pp. London. MooRE, H. F. 1907. Survey of oyster bottoms in Matagorda Bay, Texas. U. S. Bur. Fish. Doc. 610, 86 pp., 13 pis., 1 map. Washington. MooRE, H. F. 1913a. Condition and extent of the natural oyster beds and barren bottoms of Mississippi east of Biloxi. U. S. Bur. Fish. Doc. 774, pp. 1-41, 6 pis., 1 map. 1913b. Condition and extent of the natural oyster beds and barren bottoms of Mississippi Sound, Alabama. U. S. Bur. Fish. Doc. 769, pp. 1-61,5 pis., 1 map. Moore, H. F., and Ernest Danglade. 1915. Condition and extent of the natural oyster beds and barren bottoms of Lavaca Bay, Texas. Rept. U. S. Comm. Fish., 1914, App. II, 45 pp., 5 pis., 1 map. Washington. MoRisoN, Samuel Eliot. 1940. Portuguese voyages to America in the fifteenth century. Harvard Hist. Monog. XIV, 151 pp. Harvard University Press, Cambridge. Navarrete, Martin Fernandez de. 1837-80. Colecci6n de los viajes y descumbrimientos que hicieron por mar los Espanoles desde fines del siglo XV, con varios documentos in^ditos con- cernientes a la historia de la marina castellana y de los establecimientos espaiioles en Indias, coordinata e illustrada. Imprenta uacional. 5 vols. Madrid. 1943. Coleccion de diarios y relaciones para la historia de los viajes y descubrimientos . . . Instituto his- torico de marina. 5 vols., ilhis., fold. maps. Madrid. Nielsen, J. N. 1925. Golfstrommen. Geografisk Tiddsskrift. 28 Bind. 1 Hefte. Copenhagen. Paris, Bibliotheque Nationale. 1892. Quatrieme ceutenaire de la d^couverte de I'Am^rique: Catalogue des documents g^ographiques exposes a la Section des cartes et plans de la Biblio- theque nationale. Paris, J. Maisonneuve. 77 pp. GULF OF MEXICO 35 Parr, Albert E. 1935. Report on hydrographic observations in the Gulf of Mexico and the adjacent straits made during the Yale Oceanographic Expedition on the Mabel Taylor in 1932. Bull. Bingham Oceanog. Coll. 5 (1): 1-93. New Haven. 1937a. A contribution to the hydrography of the Carib- bean and Cayman Seas. Bull. Bingham Oceanog. Coll., Peabody Mus. Nat. Hist. 5 (4): 1-110. New Haven. 1937b. Report on hydrographic observations at a series of anchor stations across the Straits of Florida. Bull. Bingham Oceanog. Coll., Peabody Mus. Nat. Hist., Art. 3, 6: 62 pp., 36 figs. New Haven. Pearse, A. S., and G. W. Wharton. 1938. The oyster "leech," Stylochus inimicus Palombi, associated with oysters on the coasts of Florida. Eeol. Monog. 8: 605-655. Pearson, John C. 1928. Natural history and conservation of the redflsh and other commercial sciaenids on the Texas coast. Bull. Bur. Fish. 44: 129-214. Peirce, Benjamin, and Carlile P. Patterson. 1881. List of the dredging stations occupied by the U. S. C. S. steamers Corwin, Bibb, Hassler and Blake for 1867-1879. Bull. Mus. Comp. Zool. Harvard Coll. 6: 1-16. Phillips, P. Lee. 1901. A list of maps of America in the Library of Congress, preceded by a list of works relating to cartography. 1137 pp. Government Printing Office, Washington. 1909-20, A list of geographical atlases in the Library of Congress, with bibliographical notes. 4 vols. Gov- ernment Printing OflSce, Washington. 1924. Notes on the life and works of Bernard Romans. The Florida State Historical Soc, 128 pp. Deland, Fla. PoURTALfes, L. F. DE. 1863-69. Contribution to the fauna of the Gulf Stream at great depths. Bull. Mus. Comp. Zool. Harvard Coll. 1: 121-142. 1870. Preliminary report on the Crustacea dredged in the Gulf Stream in the Straits of Florida. Part L Brachyura. Bull. Mus. Comp. Zool. Harvard Coll. 2: 109-160. 1880. VL Reports on the corals and antipatharia. In: Reports on the results of dredging ... by the U. S. Coast Survey steamer Blake. Bull. Mus. Comp. Zool. Harvard Coll. 6 (4): 95-118. PR:fivosT, Antoine Francois. 1746-89. Histoire g^nerale des voyages, ou nouvelle collection de toutes les relations de voyages par mer et par terre, etc. 20 vols. Paris, chez Didot. Pr^vost, Jean Francois de. 1780-1801. Abrdg6 de I'Histoire g^n^rale des voy- ages . . . par M. de la Harpe. 32 vols, and atlas of 74 maps. Paris. Romans, Bernard. 1776. A concise natural history of East and West Florida ... 342 pp. New York. 259534 0—54 4 Sanz, Manuel Serrano. 1933. Expedici6n de Hernando de Soto a la Florida. 87 pp. Madrid. ScAiFE, Walter Bell. 1892. America: its geographical history, 1492-1892. Six lectures delivered to graduate students of the Johns Hopkins University; with a supplement entitled: Was the Rio del Espiritu Santo of the Spanish geog- raphers the Mississippi? 176 pp. The Johns Hop- kins Press, Baltimore. Smith, F. G. Walton; H. Franco Medina; and A. F. Brooks Abella. 1951. Distribution of vertical water movement calcu- lated from surface drift vectors. Bull. Mar. Sci. Gulf and Caribbean 1(3): 187-195. SoLEY, John C. 1914. The Gulf Stream in the Gulf of Mexico, by Lieut. John C. Soley, U. S. N., in charge of the Branch Hydrographic Office at New Orleans, La. Reprinted from the Pilot Chart of the North Atlantic Ocean for June 1914. Washington. Stearns, S. 1884. On the position and character of the fishing grounds of the Gulf of Mexico. Bull. U. S. Fish Comm. 11: 289-290. 1887. The fishing grounds of the Gulf of Mexico belong- ing to the United States, 1887. In: The Fisheries and Fishery Industry of the United States by George Brown Goode. See. Ill, pp. 55-60. Washington. 1887. The red snapper fishery and the Havana market fishery of Key West, Florida. In: The Fisheries and Fishery Industries of the United States by George Brown Goode. Sec. V, 1, (10): 585-594. Washington. Stearns, S., and David Starr Jordan. 1887. Fisheries of the Gulf of Mexico. In: The Fish- eries and Fishery Industries of the United States by George Brown Goode, Sec. II, (15): 533-587. Washington. Stommel, Henry. 1950. The Gulf Stream. A brief history of the ideas concerning its cause. Scientific Monthly 70: 242-253. SwANTON, John R. 1946. The Indians of the Southeastern United States. Smithsonian Institution, Bur. Amer. Ethnology, Bull. (3) 943 pp., 107 pis. SwEiTZER, N. B., Jr. 1898. Origin of the Gulf Stream and circulation of waters in the Gulf of Mexico, with special reference to effect upon jetty construction. Trans. Am. Soc. Civil Engrs. 40: 86-98. Swift, Franklin. 1897. Report of a survey of the oyster regions of St. Vincent Sound, Apalachicola Bay, and St. George Sound, Florida. U. S. Comm. Fish and Fish., Rep. of the Comm. for 1896, App. 4, pp. 187-221, fold, map. Washington. Tanner, Z. L. 1886. Report on the work of the United States Fish Commission steamer Albatross for the year ending December 31, 1884. U. S. Comm. Fish and Fish., Rep. of the Comm. for 1884, App. A, 112 pp., 3 pis. Washington. 36 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Thacher, John Boyd. 1896. The continent of America: its discovery and its baptism. 270 pp., illus., pis., maps. W. E. Benja- min, New York. Torres Lanzas, Pedro. 1900. Relaci6n descriptiva de los mapas, pianos de Mexico y Floridas, existentes en el Archivo general de Indias. 2 vols. Sevilla, El Mercantil. United States Bureau of Fisheries. 1919. Report of the U. S. Commissioner of Fisheries for the fiscal year ending June 30, 1917. P. 80. Washington. United States Coast and Geodetic Survey. 1878-1953. Report of the Superintendent of the U. S. Coast and Geodetic Survey showing the progre.ss of the work during the fiscal year. Issued annually. Washington. United States Coast Survey. 1845-77. Reports of the Superintendent of the United States Coast Survey. Washington. United States de Soto Expedition Commission. 1939. Final report of the United States De Soto Ex- pedition Commission. 76th Cong., 1st Sess., House Doc. No. 71, XVI, 400 pp. incl. maps. GPO, Washington. United States Library of Congress. 1901. A list of maps of America in the Library of Con- gress, preceded by a list of works relating to cartog- raphy. By P. Lee Phillips, F. R. G. S., Chief of the Division of Maps and Charts. 1137 pp. GPO, Washington. 1909-20. A list of geographical atlases in the Library of Congress, with bibliographical notes. Comp. under the direction of Philip Lee Phillips, F. R. G. S., Chief, Division of Maps and Charts. Vols. 1-2 paged continuously. GPO, Washington. Uring, Nathaniel. 1928. The voyages and travels of Captain Nathaniel Uring (first published in 1726). The Seafarers Library, London, 253 pp. Varnhagen, F. A. DE. 1858. Vespuce et son premier voyage. 31 pp. Paris. Imp. de L. Martinet. 1865. Amerigo Vespucci, son caractfere, les Merits et sa vie. Lima, Peru. 1869a. Nouvelles recherches sur les derniers voyages du navigateur florentin. Vienna. 1869b. Le premier voyage de Amerigo Vespucci. Vienna. 1870. Nouvelles recherches sur les derniers voyages du navigateur florentin, et le rest« des documents et eclaireissement sur lui. 57 pp. Vienna. Vespucci, Amerigo. 1926. The letter of Amerigo Vespucci describing his four voyages to the New World, 1497-1504. 5 p. 1., 28 pp. The Book Club of California, San Francisco. 1893. The first four voyages of Amerigo Vespucci reprinted in facsimile and translated from the rare original edition (Florence, 1505-06). X., 32 p. facs. B. Quaritch, London Walford, Lionel A. 1950. A coordinated program of marine studies for the Gulf and Caribbean. Proc. Gulf and Caribbean Fish. Inst., Second Ann. Sess., p. 129. Miami, Florida. Walker, S. T. 1880. Report on the shell heaps of Tampa Bay, Florida. Ann. Rep. Bd. of Regents Smithsonian Inst, for 1879, pp. 413-422. Washington. 1883. The aborigines of Florida. Ann. Rep. Bd. of Regents Smithsonian Inst, for 1881. Pp. 677-680. Washington. 1885. Mounds and shell heaps on the west coast of Florida. Ann. Rep. Bd. of Regents Smithsonian Inst, for 1883, pp. 854-868. Washington. Willey, Gordon R. 1949. Archeology of the Florida Gulf coast. Smithso- nian Misc. Coll. 113: 599 pp., 60 pis. Washington. WiNSOR, Justin. 1884-89. Narrative and critical history of America. 8 vols. Houghton Mifflin and Company, Boston and New York. 1904. The Kohl Collection (now in the Library of Congress) of maps relating to America. A reprint of Bibliographical Contribution number 19 of the library of Harvard University. GPO, Washington. CHAPTER II GEOLOGY SHORELINES AND COASTS OF THE GULF OF MEXICO By W. ARMSTRONG PRICE,= Agricultural and Mechanical College of Texas INTRODUCTION The scientific study of shorelines is inextricably involved with that of the hinterland, the coastal zones, the adjacent inshore waters and the climate. This linkage brings together regional geology, geomorphology, sedimentation, oceanography of the inshore zone, meteorology, climatology, biol- ogy, chemistry, late geologic history and the ecology of some marine and coastal organisms. As the study of shorelines and their classification is in somewhat incomplete and controversial condition today, it is necessary to give a brief review of the subject before discussing the shore- line of a particular region, such as the Gulf of Mexico, where there are new types and where we have previously had few over-all geological oceanographic conceptions to guide us. STATUS OF STUDIES OF COASTS AND SHORELINES The geological study of shorelines and coasts has been intermittently' developed by numerous geologists and geographers. The principal dis- cussions of costal geomorphology that are readily available are Johnson's (1919) detailed treatise on shoreline development and his study of the New England- Acadian shoreline (1925), Shepard's (1937a, 1948) revision of Johnson's shoreline classification. Steers' (1946, 1952) analytical de- scription and history of the shoreline of England, Wales, and Scotland, and Russell's (1940) study of the development of variations in deltaic shore- lines in Louisiana. McCurdy's (1947) discus- sion of criteria for the delineation of shorelines from air photographs yields critical details of some types not found elsewhere. Fleming and Elliott (1950) have made a beginning of an over-all quantitative and qualitative oceanographic ap- proach to the study of shorelines which is here revised, enlarged and treated in greater detail, in ' Contribution from the Department of Oceanography of the Aericultural and Mechanical College of Te.xas, No. 15, April 1953. ' Professor of Geological Oceanography. Formerly, independent petroleum geologist of Corpus Christi, Texas. some of its aspects, for the Gulf of Mexico. Some of the oceanographic data treated by these workers have not been considered here. Among the greatest present needs in geomorphic coastal studies are a critical analysis and descrip- tion of the coastal plain shoreline and regional studies combining the geomorphic and ocean- ographic approaches. The research on which this paper is primarily based was a comprehensive survey of the shorelines of the Gulf from existing data, including results of the writer's 20-year study of the northwestern Gulf Coast. The survey was made by the writer in 1951-1953.' It has revealed a number of new types and re- lationships not yet critically discussed in publica- tion. Because of this situation, the writer is handicapped in attempting a discussion of the coasts of the Gulf of Mexico within as condensed a scope as that of the present paper. The application of quantitative oceanographic science to the analysis of the development of shore- lines is being slowly accomplished through the work of numerous scientists and engineers by isolated studies of beaches, cliffs, deltas and estuaries, but has only lately been attempted for whole regions. In the writer's current research, an attempt is being made to apply a quantitative regional approach to the study of the influence of oceanographic processes on shorelines and the associated coastal and shallow-water bottom con- ditions. Some of the results of this work are reflected in this paper. SHORELINE CLASSIFICATION Eduard Suess (1888) showed that regional or continental shorelines might be classed as con- cordant or discordant with the grain (dominant trend) of the geologic structures of a coastal region, but King (1942, p. 99) cautioned that marine activities subsequent to the drowning of a coast or the formation of its folds and faults mav have 3 Contains no references to the work of others after March 1, 1953. 39 40 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 67- -■,--, ^- Figure 12. — Shorelines of Gulf of Mexico, showing locations of major geographic features. (Contour lines off the Mississippi delta are drawn at 200-fathom intervals.) GULF OF MEXICO 41 altered the shoreline so that it may no longer con- form to a simple structural classification. Johnson (1919) assembled and extended previous ideas of coastal development and classification to pro- duce a detailed genetic-geomorphic system that has since been followed by most writers. How- ever, it seems not to have been applied by its users to the detailed mapping of the coasts of a large, diversified region such as the Gulf of Mexico, although Johnson (1925) applied it to the drowned and largely discordant shoreline of the New England-Acadian region of northeastern North America. Shepard (1937a, 1948) modified and extended Johnson's system, giving a tabulation in which shoreline and coastal types then described were inserted. His major divisions differ from John- son's and seem not to have been accepted by all of Johnson's followers, although the scarcity of papers on the classification of shorelines indicates that this may be due to inertia rather than to a working appraisal of the usefulness of Shepard 's revised system. Johnson's text is out of print and has not been supplemented by a similarly detailed work. Regional variations in the known physical oceanographic conditions in the "inshore" zone* of the coasts of the United States and Mexico were discussed by R. H. Fleming and F. E. Elliott (1950) in lectures. They regarded the scarcity of such information too great for elaboration of their method at that time. It, however, classifies coastal sectors into glacial, alluvial, young orogenic and biogenous types, with erosional and depositional sub-types for the first three. The continental coasts of the Gulf of Mexico were included in the maps and discussion. The Fleming-Elliott system has been modified and extended in some of its aspects for use in the present study as the geo- oceanographic classification system. Changes in their mapping of the Gulf coasts include the intro- duction here of young orogenic sectors and the relegation of biogenous coasts to a secondary condition imposed on a framework of regional geologic and geomorphic types. In the latter instance, the suggestion made by Shepard (1948, pp. 78-79) is followed that a regional classification could be made by using large subdivisions such as coasts with young mountains, old mountain ranges, * Shallow water or nearshore zone. Some writers use "inshore" for la- goonal and estuarine environments. broad coastal plains, glaciated coasts, and such specific but less common items as volcanic coasts and tableland coasts. Space does not permit including here an elabora- tion of the detailed genetic-geomorphic classifica- tion systems. As detailed knowledge of many coasts accumulates, including coastal plains such as those of the Gulf, the list of the distinctive small-unit features becomes encylopedic and the classification headings numerous, beyond the simplicity desired (Lucke 1938) for text-book and lecture purposes. Definitions. — The shoreline is the line where land and water meet. It moves back and forth over the shore or shore zone. The shore on a beach has been defined (Beach Erosion Board, Corps of Engineers, U. S. Army) as the zone between mean low tide (or lower low tide) and the inner edge of the wave-transported sand. The lagoonal shore is that of the tidal bays and lagoons. Estuaries are tidal stream courses. Their shores are not studied here except where they are em- bayed. On some coasts there are extensive, muddy shore-flats. Tidal flats are properly those within the range of normal gravitational tides. In some places winds blow the water across broad, gently sloping wind-tide flats * that extend inland from the ti-ue shore, hence, beyond the high tide limits for gravitational tides, and have been floored by deposits left by the water. The coast is a zone of indefinite width back of the shoreline that is affected by or closely affects offshore or shoreline processes and forms. The waters lying near the coast where the effect of a shallow bottom is felt may be called coastal waters. The continental shelf (fig. 13) is a submerged, gently sloping plain that extends the continent ocean- ward to varying depths ranging, generally, between 40 and 100 fathoms. The shelf is terminated sea- ward by the steeper shelf slope that descends, in places precipitously, to the depths. Additional definitions will be given in later paragraphs when the barrier island, the shelf and its equilibrium profile, and the mangrove coastal ridge are discussed. New and undescribed types. — New types recog- nized on the shorelines of the Gulf of Mexico which will be readily understood from previous geomor- phological knowledge are (1) the drowned karst (sub-aerial limestone solution topography) of parts *New term. 42 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE of Florida and the Yucatin Peninsula (fig. 12; fig. 14, sector 2.1); two minor forms: (2) sand dunes briefly drowned by exceptionally high tides; and (3) wind-tide flats, previously described. Other new types that form striking features on the coast of southern Florida and the Yucatan peninsula, are (1) the great mangrove barrier ridge (fig. 12; fig. 14, Sector 4.1); (2) the irregular mangrove coastal lagoon between the mainland and the ridge, (3) the drowned lacustrine plain of the Bay of Florida (fig. 14, Sector 4.1 north of Florida Keys and east of Cape Sable; fig. 15) as interpreted by the writer, with former lakes of marsh or swamp now invaded and enlarged by salt water, and (4) what the writer believes is the same type of coast slightly elevated (elevated lacustrine plain) to form the pocket harbors (Hayes, Vaughan, and Spencer, 1901) of northwestern Cuba (fig. 12; fig. 14, sector 3.1). The present paper does not offer an oppor- tunity for full critical discussion of these new types. Besides the distinctly new types of shoreline and coast, noted here, a number of fairly well known geomorphic forms were found which have not previously been included in shoreline classification lists. Prominent examples for the northwestern Gulf coast are the broadlj' to roundly embayed drowned-stream valley with shallow, pan-shaped depositional bottom previously described and in- vestigated by the writer (Price 1947) and the drowned deltaic topography (fig. 12, betweenBird- foot delta of Mississippi and Lake Pontchartrain) described by Russell (1936, figs. 6, 7; 1940). SOURCES OF INFORMATION Published articles include (1) the numerous detailed geological reports and maps on coastal land areas in the United States' with a few general- ized and regional reports on those of Mexico and Cuba, (2) shoreline and coastal studies of the United States Army Engineers, (3) a few ecolog- ical studies of coastal areas chiefly in Florida and Louisiana, (4) progress reports of the ocean- ographic survey of the Gulf of Mexico being conducted by the Department of Oceanography of the Agricultural and Mechanical College of Texas (Leipper, p. 125) and progress reports on investigations of sedimentation and other shallow water conditions of the northwestern Most complete for Florida and Louisiana. Gulf of Mexico by the American Petroleum Institute and similar commercial projects. Among scattered reports on previous oceanographic cruises yielding shoreline or shallow water data (5) is a study of foraminifera in bottom sediments by Phleger and Parker (1951). Much geographic and some geomorphic information is found in Tamayo's (1949) extensive text and atlas of the general geography of Mexico. Important raw data, some of which are listed in the following paragraph, include (7) topo- graphic maps and air photographs of the land, (8) original Federal hydrographic surveys, in- cluding some old surveys of the British Ad- miralty, (9) navigation and (10) aeronautical charts made from these sources, with (11) the coast pilot and sailing directions handbooks of these organizations, and (12) bottom-sediment charts of the shelf of the northern Gulf. Topo- graphic data are scarce outside the United States and of unequal detail and coverage for the dif- ferent States. For Mexico, air photography made by the United States and Mexican governments is available under restrictions. The Cuban hydro- graphic organization has issued a coast pilot (Derrotero) containing new coast charts. Charts and other aids in study of coasts. — For any detailed study of these shorelines it is necessary to have first, a set of nautical charts. Figure 12, a finding map for this study, is drawn on the base of the general chart for the Gulf. The less accurate and detailed these aids are for any coastal sector, the more they need to be supplemented by air photography, topographic maps and geologic reports. The following charts are recommended. U. S. Coast and Geodetic Survey Nautical Charts {U. S. Scores) .—General Charts, 1002, 1007, 1290: Sectional Charts 1113-1117; Coast Charts 1249-1280. For special details, some of the large-scale charts of islands, harbors and canals, and Chart A634. See catalog: Serial No. 665. Hydrographic Office, U. S. Navy, Nautical Charts (Mexico and Cuba). — General (coastal) Charts 1125BS, 1126, 1126BS, 2145, 2056, 0966, 5487. See catalog: Pub. I-N. Marina de Guerra, Departmento de Inspeccion, Officina Hidrograjica, Republica de Cuba. — Der- rotero de la Isla de Cuba (sailing directions). Parte Segunda, 1951, 173 pp. 21 figs, has coast GULF OF MEXICO 43 charts from recent surveys done on thin paper, bound in the book. Soundings and underwater contours are given to depths of from 30 to 60 brazos de agua (Cuban fathoms). World Aeronautical Charts, U. S. Air Force {Mexico and Cuba) .—Charts 522, 586-589, and 643-645. See: Aeronautical Chart Catalog, Coast and Geodetic Survey. Topographic Maps, Air Photographs and Geo- logical Reports. — The U. S. Geological Survey publishes a series of key maps for the United States, Alaska, and Insular possessions showing the status of topographic mapping and air (aerial) photography, including mosaic sheets and with some geologic mapping. State maps showing the areas covered by all published geological re- ports and articles are available for some States from this agency. The State geological surveys and bureaus also furnish lists of their publications. The Geologic Map of North America, Geological Society of America, 1946, and the American Geographical Society's Map of North America are useful regional aids, besides State geologic and topographic maps. Areal summaries of oceanographic data. — Since Vaughan's (1937) survey of information available in this field no general key maps have been published. Articles on geological oceanography of coastal areas are now listed in geological bibliographies. ACKNOWLEDGMENTS The writer is indebted to a large number of persons and organizations too numerous to list here. Valuable aid was received from the State geological surveys of Florida and Louisiana, and some former members of the latter; several mem- bers of the United States Geological Survey; officials of the Coast and Geodetic Survey, Hydro- graphic Office, photographic branches of the Arm}^ Navy, and Department of Agriculture, and the corps of Engineers; geologists of the Mexican federal geological survey and petroleum development agency, as well as numerous individ- ual geologists, biologists, ecologists, and other persons familiar with remote and little-known parts of the shorelines of Mexico, Florida, and Louisiana. To his colleagues in the Department of Oceanography of the Agricultural and Me- chanical College of Texas, the writer is deeply indebted for orientation and guidance in oceanog- raphy during the years of 1950-53, as well as for specific information and aid. The develop- ment of the research on which this condensed paper is based was followed closely by Warren C. Thompson and Charles C. Bates, while doing research in the Department, with whom many helpful discussions have been held. The impetus in the development of the geo-oceanographic classification here used, as has been said, came from the manuscript by E. H. Fleming and F. E. Elliott. STRUCTURAL AND REGIONAL GEO-OCEANOGRAPHIC APPROACH TO SHORELINE DESCRIPTION AND CLASSIFICATION FOR GULF OF MEXICO COASTS AND HINTERLAND The Gulf provides a good example of the well- recognized relation (Weaver 1950) of the topography of the hinterland to the width of coastal plains and continental shelves (fig. 13). ^ The geolog ic structure of any hinterland largely ' Taken from Price (1951 b). controls its topography and has a direct or indirect effect (Suess 1888) on the character and positions of shorelines. These factors are dominant in determining the drainage and hence, the transport of sediment from the land to coastal areas. 44 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Figure 13. — Major geologic structures exposing uplifted rock masses surrounding Gulf of Mexico. Cross-hatched, folded sedimentaries, granitic areas, volcanic belts. Stippled, uplifted arches or horsts. Stipple and dash, emerged parts of arches form limestone plateaus at south and east. Under-water contours, 100 and 1,900 fathoms, the former out-lining the continental shelf, the latter, the Mexican Basin (Sigsbee Deep) . Long broken lines, axes of arcuate Caribbean folding (axis of Gulf coast geosyncline, supposedly along northwest shore, not yet located. Scale: Hun- dreds of miles. REGIONAL COASTAL TYPES YOUNG OROGENIC COAST Where geologically young mountains (Tertiary to Quarternary) closely border the coast (Umb- grove 1947, pi. 5), as in Cuba and the south- western Gulf coast in Mexico (figs. 12, 13; fig. 14, Sector 3), coastal plains and the continental shelf are absent, narrow or of irregular width, and the shelf tends to be rocky with shoals and irregular elevations (Fleming and Elliott 1950) as well as somewhat steep (slope greater than about 5 feet per statute mile). Sand and mud* occur on the shelf and mud along the outer margin and in shelf deeps. The coast may have alternating narrower erosional and wider depositional sectors, the latter with smooth shorelines and bottoms, the former with uneven surfaces. These coasts and shelves are unstable and subject at any time to earthquakes, fracturing and warping of the crust. s Sediment terminology used is that of the coast charts. "Mud" is a field term implying no accurate knowledge of the clay fraction. GULF OF MEXICO 45 Young orogenic coasts have their shorelines dominantly parallel (concordant, Suess 1888) with the structural trends (folds and faults) of the mountains. The Gulf provides no ex- amples of coasts where the shoreline is more than very locally discordant with the structural trends on land.' This accounts to a large extent for the almost complete lack of islands in the Gulf other than sandy barriers close to shore, karst islets of Florida, some lava-rock islets in Sector 3 in Mexico, and coral and detrital reefs on shoals. From the meager data of the charts we conclude that, because the Mexican mountains are mostly not younger than Miocene, coastal sediments have built out around or otherwise protected most of their outpost hard rock folds from the Gulf. However, a large mountain range projects eastward under water some 50 miles off Tampico and two parallel mountain ridges trend northwestwardly from the edge of the continental shelf off the Rio Grande delta. The Tertiary mountains of Cuba (Palmer 1945) rise from a short distance back of the coast. The folded rocks come down to the coast or are overlain there by a thin cover of younger deposits. The island may be divided into several areas of different tectonic structure, but overthrust folds rising up to the south dominate some sectors, as in the extreme west. The Gulf bottom off the north coast descends at angles of 4° to 6° or more, a slope which conforms fairly well to some of the folds. A narrow shelf occurs only where fringing reefs have grown up with a rising sea level to form barrier reefs, so that the lagoon has been filled to a shallow depth with sediment and organic growths (3.2 Sectors, fig. 14). The drainage of northwestern Cuba is largely southward, so that only small streams enter the Gulf and the coralline lagoons. The sedimenta- tion along the northwest shore has, therefore, been negligible except where coral reefs and mangrove growth have trapped marine and land- derived materials. An erosional sector occurs between the barrier reefs east and west of Havana. The Sierra Madre Oriental, the eastern Cordil- lera of Mexico, slants southeastward toward the coast, one of the outpost folds in limestone rock making a minor protuberance at Punta Jerez (fig 13).'° The coastal plain becomes gradually narrower southward from the delta of Rio Grande. It is, however, as much as 60 or more miles wide in places. The Southern Volcanic Range of Mexico (Sierra Neo-Volcanica, Tamayo 1949), a zone of Tertiary-to-Recent volcanic peaks, runs from the Pacific coast due east through Mexico City to form the broadly protuberant Jalapa Salient north of Veracruz at 20° N. Lat. A similar salient south of the city, that of San Martin Tuxtla, separated from the range, may be geo- logically associated with it. The range includes some of the greatest peaks of Mexico, including at the east, in sight of the Gulf, Orizaba and Cofre de Perote, reaching elevations of 18,696 and 14,048 feet, respectively, above sea. Between and on each side of these salients are sedimentary embay- ments (fig. 14, 3.2) with fairly broad coastal plains. Only a narrow belt of low shoreline deposits seems to be present along the fronts of the vol- canic salients. These salients are composed of confluent and overlapping flows of volcanic rocks, some of which make small jutting points at the shoreline. Of these, Roca Partida and Punta Delgada have cliff ed faces reported to be 1,000 feet high, with islets of lava rock. There are several volcanic peaks in the San Martin salient, including San Martin Tuxtla, which has been active in historic time. On air photographs of this sector, the writer counted some 20 small cinder cones aligned in a zone about 10 miles wide and 40 miles long parallel with the coast. One of the cones stands in the intermountain Lake Catemaco with its crater invaded by the water. The continental shelf off the orogenic coast of Mexico is poorly mapped. It is narrow and, where mapped, the gradient is convex, becoming steep, like that near the outer edge of the shelf of Texas and Louisiana. The grain sizes of the sediments, so far as is revealed by the data on the charts, decrease more regularly outward than on some better-known orogenic coasts, as that of California where there are separate offshore sedimentary basins both on and off the shelf, each with its own sedimentary distributional pattern. The small size of the sub-aerial drainage basins where mountains stand near the coast has ' Discordant coasts are found today chiefly where old mountain areas, as from New England to Newfoundland, have been drowned by sinking of coasts under load of Pleistocene ice sheets. '0 The convexity here is exaggerated on O. O. Chart 2056 as compared with the later W. A. C. 689, made from a photographic base. 46 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Figure 14. — Regional geo-oceanographic classification, shorelines and coasts, Gulf of Mexico: 1, alluvial coasts; 2, drowned limestone plateaus; 3, young orogenic coasts; 4, biogenous (organic) development on various coasts. Sub-sectors: 1.1, deltaic coasts, with 1.11, unentrenched simple deltaic plain, and 1.12, entrenched and embayed compound deltaic plain. 1.2, terraced deltaic coastal plain; 2.1, unsimplified to little simplified drowned karst ; 2.2, limestone karst with beaches; 3.1, erosional, and 3.2, depositional, orogenic coasts; 4.1, broad shelf; 4.2 shelf absent to narrow; 4.3 lesser biogenous development (more extensive than shown). The two southerly Mexican 3.1 Sectors are volcanic salients. been shown to restrict coastal sedimentation. This is true here, in that the shelf is wide off the several sedimentary salients, but narrow in front of the coastal mountain salients. ALLUVIAL COASTS Where the closest mountains, usually old mountains, are located far or moderately far in- land (Umbgrove 1947, pi. 5), the runoff and sedi- ment load from the lands has been large and long continued, interior plains are succeeded by broad coastal plains and continental shelves, and the coast is of the deltaic (Fleming and Elliott 1950) or alluvial coastal plain type. On such a coast, after sufficiently long stillstand, shelf bottoms are smooth except toward their outer margins, organic reefs are inconspicuous, few or absent, and shorelines are smooth or irregularly deltaic (fig. 13, and No. 1 Sectors, fig. 14). .Sediments here ai-e generally of even distribution to somewhat spotty (Lynch, fig. 16). Sands extend from shore out to about 5 or 10 fathoms, followed by silt or sand and mud (charts), with mud further out to the edge of the continental shelf. Mud or silt GULF OF MEXICO 47 may come in very close to the mouth of a deltaic river that drains a large basin. Tiie chief excep- tions to the outward banding of sediments (Emery 1952) are any coai-se sediments of local organic or chemical origin, or, along the northwestern shelf of the Gulf, sediments on mounds believed to lie above buried intrusive salt dunes (Shepard 1937 b). The alluvial sectors of the Gulf of Mexico (Sec- tors Nos. 1.11, 1.12, and 1.2, fig. 14) have smooth shorelines with sandy beaches on the mainland, or on barrier islands (Price 1951 a). The beaches may be more or less interrupted by deltas of vary- ing degrees of protuberance and shoreline irregu- larity (Russell 1940; Bates 1953). Offshore, the alluvial sectors have broad, smooth continental shelves, 130 miles wide at the maximum, with relatively steep inshore shelf-bottom profiles (fig. 15, Sector VII) and a rather uniform gradation of sediment from sand (generally inside the 5- or 10- fathom depth contour) to sand-and-mud, with mud at the outer margins. The elevated mounds on some outer parts of the northwestern shelf have nodular algal limestone on their tops and possibly some coral. Subsectors, alluvial coast: terraced detaic plain. — Sector 1.2, Alabama, Mississippi, and western Florida (fig. 14), has a fairly steep coastal plain," with two Pleistocene-and-Recent deltas (Apala- chicola, Pascagoula, and Pearl), a minor amount of embayment of drowned stream valleys and a reported series of low, parallel elevated shoreline scarps (Carlston 1950). In places, the younger two of these have roughly parallel Pleistocene barrier islands and coastal lagoons (MacNeil 1950) in part entrenched by drainage and embayed. This coast is like that of the southern Atlantic coastal plain of the United States, with which it has a common geologic history. These similari- ties exist because of the position of the old (Pale- ozic), almost entirely quiescent Appalachian mountains fairly close (90 to 150 miles) to the coast hut not in a bordering position. Drainage basins extending from the mountain front across the coastal plain are small in relation to those of the deltaic 1.12 alluvial coast. The large cuspate Pleistocene-Recent Apalachicola delta and the long, broad, and shallow Mobile Bay are striking features of this coast • Eight feet per mile nenr the coast in some places. Broadly embayed deltaic coastal plain. — ^Sector 1.12 (fig. 14), the coast of Louisiana, Texas, and part of Tamaulipas, receives the drainage of some ten major rivers. Three major Recent deltas now reach the Gulf; the Mississippi-Red, Brazos- Colorado, and Rio Grande deltas. A very broad, gently sloping deltaic coastal plain (Barton 1930) has been built, forming a fully concordant coast (Suess 1888). Coastal plain deposits form a new structiu'al (monoclinal) trend in front of the abrupt southwestern ends of Appalachian folds once projected into the broad Mississippi embayment. Sector 1.12 (fig. 14) is deltaic except between arcuate delta fronts where the active barrier and the Pleistocene Ingleside barrier island (Price 1933) with their parallel, active and entrenched coastal lagoons form a diversified inner coast tran- sected by many broadly drowned and embayed stream valleys (Price 1947). There are, thus, intermittent terraced riverine plains between ad- jacent protuberant Recent deltas. Behind the terraced belt are continuously overlapping and coalescing Pleistocene deltas with their surfaces slightly up-warped inland. The great protuber- ant Mississippi-Red delta (Russell 1936; 1940; Bates 1953) dominates the eastern part of this sector both at the shoreline and on the shelf where large shoals seem to indicate submerged deltas. A minor feature of the deltaic coast is the saline marsh (paralic) environment described on a later page with the biogenous environments. Saline plain of Rio Grande delta. — A broad, treeless, saline plain, the Jackass Prairie of Cameron County, dominated in the native state by coarse, bunchy Spartina salt grass (sacahuista), stretches inland across the Recent delta north of the natural levees of the present Rio Grande course for a maximum distance of 10 miles. The Gulf ward edge of the plain is honeycombed by saline lagoons lined on their lee (N., NW., W., and SW.) sides by clay dunes (Coffey 1909, Price 1933, Huffman and Price 1949). The soil of the low deltaic plain is made heavily saline by wind- blown (cyclic) salt contained in clay pellets and dust blown from the saline tidal flats of the la- goons. These flats undergo strong deflation dur- ing the warm months. Sand-sized pellets of flocculated saline clay accumulate on lee shores to build the dunes, while saline dust passes over the 30-foot-high dunes under the strong steady hot winds of the warm months. 48 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE From detailed topographic data it is estimated that about one-fifth of the wind-blown clay ex- cavated from playa lake basins is caught on the dunes as sand-sized pellets and the remainder passes inland as dust. The saline plain is nar- rower in Willacy County to the north where the Recent delta and the zone of playas and dunes is narrower than to the south near the Rio Grande. Unentrenched deltaic sector. — Sector 1.11, the coast of Tabasco and parts of Veracruz and Cam- peche, Mexico (figs. 12, 14), is a simple deltaic coast with a tropical rain-forest and fairly wide tidal streams that are not embayed. The large Laguna de Terminos is a delta-margin depression, a feature which Bates (1953) thinks is normally a nondepositional basin. Sinking by compaction, former entrenchment and enlargement by wave and current scour are factors that aid in shaping some of the delta-margin basins. This sector has a broad, gentle deltaic plain, abundantlj' crossed by innumerable courses of the Tonala, Seco, Grijalva, Teapao, Usumacinta, San Pedro Y San Pablo, and Palizada Rivers. These courses are grouped into two main deltas; the Seco-Grijalva delta at the west, with a broadly and symmetrically bowed shorehne, and the asymmetrically bowed Grijalva-San Pedro Y San Pablo delta at the east. The latter has a small cuspate mouth. DROWNED LIMESTONE-PLATEAU COASTAL PLAINS Continental or insular shelves may exist off the above-water parts of oceanic shoals appearing as island groups or as peninsulas attached to coa- tinents. Very broad shelves, upwards of 100 miles wide, border the peninsulas of Florida and Yuca- tan in the Gulf (fig. 13 and No. 2 Sectors, fig. 14). These low peninsulas are great uplifted limestone shoals, now partly drowned limestone plateaus. Their origins have been discussed elsewhere (Price 1951b). The surfaces of these plateaus, both above and below water, show a young rolling karst topography of limestone solution with solution-basins and sinkholes. Surface drainage is locally absent and is supplemented by under- ground water circulation moving tlirough solution channels. The Florida limestone is abundantly fissured, at least at the northwest (Vernon 1951). The plateau peninsulas are terraced limestone coastal plains. They have delivered a minimum of land-derived detrital sediment to the shelves, so that, under tropical climates, these shelves in places abound and probably have long so abounded in great coral reefs (F. G. W. Smith, p. 291) and some reef-like bars and sand keys of shell detritus. The sinkhole topography of the limestone plateaus is of subaerial origin, now modified in a broad belt near the shoreline, both above and below water, by coastal deposits (Vernon 1951)'^ and an undetermined amount of solutional activ- ity (Fairbridge 1948). There are a few relatively narrow, submerged stream valleys. Submerged subaerial karst basins are, so far as known, only shallowly filled with a foot or two of sediment, yielding poor anchorage for ships. Offshore bot- tom slopes of the inner half or more of the conti- nental shelf are very gentle (fig. 15, curve 6) to moderately gentle (fig. 15, curve 4), ranging from about 1.5 to 2.5 feet per statute mile. For a few miles offshore, there are many, irregular, shifting bars of shelly sand. The limestone-plateau coasts have three types of subsectors: slightly elevated drowned karst salients of a low marshy coast (2.1), beach-bor- dered (2.2), and mangrove-ridge (4.1) shorelines. These show shoreline modification and smoothing ranging from a virtual zero modification through incipient planation to nearly completely smooth beach-bordered coasts. Coastal marsh and swamp of the limestone plateaus are abundantly chan- neled perpendicular to the shoreline by tidal scour. The tides are higher on the peninsula coast of Florida (range 2 to 4.5 feet) than on any other part of the Gulf shoreline. Inshore on the drowned karst coast, and offshore on it and on the other subsectors of the limestone plateaus, we have the so-called carbonate environment of the continental shelf (Trask 1937). DROWNED KARST SHORELINE SUBSECTOR Subsector 2.1 (fig. 14), along the northern coast of peninsular Florida north of Anclote Keys, near Tampa, has a new type, the drowned karst shore- line. Short convex areas have an intricate, cren- ulate shoreline with many small shoreline basins and archipelagoes of stony islets. Much of this karst shows, on the scale of the navigation charts, no modification by marine agencies. This entire subsector lacks embayed drowned stream valleys " Zones of submerged bars and their uplifted counterparts on elevated terraces. GULF OF MEXICO 49 and sandy beaches (Martens 1931) except short, elevated stormbeach ridges and sandy beaches on some of the Cedar Keys archipelago at 29° 10' N. Lat. These latter beaches (Martens 1931) are somewhat muddy and unlike those of glaringly white sand on the front of the Apalachicola delta, Sector 1.2, and westward from it in Florida. With this drowned karst coast of Sector 2.1, there are areas of transversely channeled marsh 2 to 3 miles wide occupied by grassy vegetation and forested swamp. This swamp is probably mostly saline. Patches of mangrove swamp occur in the southern part of this Sector. The scattered mangrove swamps with offshore oyster reefs to be described mark a minor exten- sion of the biogenous environment (Sector 4, fig. 14). The drowned karst coast is conspicuous for its many and unique marine oyster reefs, located along a shallow-water zone extending outward to a distance of a mile or two from shore. Crassos- trea virginica, the North American oyster of commerce, is notably lagoonal and estuarine, commonly being confined to brackish water en- vironments by its marine-water foes. Only along parts of the Gulf coast are living reefs of this species known in oceanic waters in North America. On Sector 2.1, the highly fractured and channeled limestones of Florida are filled inland with fresh water to a considerable height above sea level. The slope of the groundwater surface (piezomet- ric) toward the coast indicates a movement of underground water in that direction. Also, along much of the coast of Sector 2.1 there is an artesian groundwater head of about 10 feet near and at the shoreline (Cooper and Stringfield 1950, fig. 14). This pressure-head forms springs in the stream mouths and stream beds, as well as offshore. '^ The absence of land-derived sedi- ment in these streams during most of the year and the protected nature of the shelf waters leave the water of the Gulf brackish here. Off the mouth of Atchafalaya Baj', Louisiana, oj'ster reefs also grow in the Gulf out to a distance of 3 to 5 miles, with the fresh water of the river mixing with Gulf water to produce a brackish environment. Beach-bordered karst subsector. — Sector 2.2 (fig. 14) is represented both on the central coast of " Data on charts and reports of aviators via V. T. Stringfield, letter of 1862. peninsular Florida and on the coast of the Yucatiin Peninsula. On Florida, the sector has fairly continuous sandy barrier islands and barrier spits with some mainland beaches. This sector ex- tends from Anclotc Keys near Tampa at the north to Cape Romano at the south. The drowTied karst lies behind the beaches and the coastal lagoons of the sandy barriers. The lagoons are bordered by mangrove swamp and with the karst depressions more or less filled with sediment and marshy growths. The beaches of this sector (Martens 1931) have much shell material but also quartz sand. The quartz is derived from elevated sandy Pleistocene beach deposits of the elongated dome-shaped summit (300 feet or more) of the peninsula, which lies immediately inland, and from a sandy limestone formation that has been almost removed by embayment of several streams to form the broadly embayed harbors of Tampa Bay and Charlotte Harbor. These harbors are the only embayed, drowned, stream valleys of the Gulf coast of the peninsula, except the mod- erately widened tidal portion of Caloosahatchee River, nearby. The shelf-bottom slopes more steeply off this sector (2.2 feet per mile, fig. 15, curve 4) than it does farther north on Sector 2.1. Cape Sable (fig. 12) protrudes into the Gulf where Florida Bay extends eastward at the end of the mainland of the peninsula. This major shoreline bend produces a convergence zone for waves, swell and currents with the local wave attack necessary to develop a beach, keeping the shore free of mangroves. The beach plain has cuspate points and encloses narrow lagoons behind it. The beach sand is presumably mainly shelly. The oval area of plain behind the sandy beaches and the lagoons of the Cape is somewhat marshy. The origin of the broad, irregular lagoon known as Whitewater Bay, lying several miles inland from the beach is linked with the deliverj'^ of a concen- tration of drainage to a marsh. The bay is heavily fringed with mangrove swamp. The beach-bordered subsectors (2.2) on the Yucatdn Peninsula include the northern coast and the short Campeche-Champoton sector at the west. The northern coast has barrier islands and a number of slightly disconnected barrier spits which extend westward from moderate pro- jections of the shoreline. Pinnacles of limestone 50 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE several feet high protrude thi'ough the beach in places (Sapper 1937). Marshy, swampy, and partly mud-filled coastal lagoons lie behind the barriers. They are extensively occupied by man- grove swamp forest. These lagoons are called "rivers" on some maps. They were formerly thought to form a continuous inner waterway across the north end of the Peninsula. The short beach-bearing sector in the Campeche coast between the towns of Campeche and Champton (fig. 12), seems from air photographs and ground-elevation figures (20 feet to the north against 400 to 500 feet in the block) to be an uplifted fault block of limestone with entrenched stream valleys floored by narrow alluvial plains. The Gulf ends of these alluvial deposits have sandy-to-cobbly pocket beaches. Observers re- port seeing large blocks of limestone on some of them. One report, probably, erroneous, calls some of these blocks and a nearby outcrop "igneous" rock. BIOGENOUS ENVIRONMENT Where, on the coasts of the Gulf, land-derived sediments have been and are now scarce, sediments of organic origin with large marine organic struc- tures become conspicuous. Such a biogenous environment (fig. 14, Sector 4) (Fleming and Elliott 1950) may vary, here and there, from a brackish lagoonal and inshore enviroimient to a marine environment with waters of normal salinity or salinities somewhat above average (Trask 1937) . Where the water is now, or has lately been, warm, tropical and of at least normal marine salinity, coral reefs thrive. The physical limita- tions of this environment have been long and widely discussed. The biogenous environment is an oceano- graphic condition existing as an overlay on the basic geological coastal structures. It may occur on any type of shoreline where, and so long as, the requisite sedimentary and oceanographic conditions previously mentioned occur. The biog- enous environment includes the carbonate en- vironment, where MoUusca and corals are con- spicuous among the sedentary organisms, and the paralic or marine swamp and marsh environ- ments, such as those of the mangrove and salt- water grasses and reeds. It may be that, with further analysis, a funda- mental geological coastal type of biogenous nature may be recognized. Thus, the limestone peninsulas of Florida and Yucatdn may, from the historical point of view, be considered geologically biogenous, since the limestones have been built up for millions of years under dominantly cal- careous biogenous conditions. The Cuban coast, and the Gulf coast of Mexico west of the Yucatdn Peninsula, are today only superficially biogenous, as the organic growths and sediments form a mere patchwork skin on the rock folds. Limestone series several thousands of feet thick among the folded and faulted rocks of Cuba, however, show that the site of the island was biogenous for millions of years. Deposits of argillaceous (clayey) shales and the great earth-deforming (tectonic) events, were major interruptions in the carbonate type of biogenous environment in Cuba. The structural conditions of Cuba today overshadow, for geologists, the biogenous history. Carbonate subdivisional environment. — Subsec- tors of the biogenous coasts (Sectors 4) present a variety of structures and bottom types. Coral reefs and the carbonate environment in general occur on both broad (fig. 14, 4.1) and narrow (4.2) shelves. Large shelf areas have a conspicuous bottom-dwelling population. Among these, sponges are conspicuous. Actively growing coral reefs (Smith, p. 292) include fringing and barrier reefs on Cuba and a barrier reef along the outer side of the Florida Keys. This coral barrier runs along the edge of the shelf facing the Straits of Florida at the far southern end of the peninsula. Fringing reefs are also found here and there on other coastal sectors, as near the mouths of streams on the Mexican coast (Sectors 1.11, 3.1, 3.2) and on 4.1 on the Yucatan Peninsula. The great Colorados Barrier Reef of northwestern Cuba is fringing at its eastern end but encloses a 15-mile- wide lagoon to the west. Atolls and atoll-like coral reefs of more or less tabular form occur west of the Florida Keys (Dry Tortugas atoll) and others form a great, dis- continuous, barrier range along the northern and northwestern margins of the Yucatdn shelf, called the Campeche Banks (Smith, fig. 62, p. 292). The best known of these is the large Alacran atoll. The Marquesas detrital atoll off Florida (Vaughan 1914; Cooke 1939, fig. 31) is not known to have coralline growth, the reef being a group of sand keys of shell detritus formed on the shelf by the strong westward currents and winds. The Mar- GULF OF MEXICO 51 qiiesas is a great lunate key partly closed at the southwest by a series of smaller lunate keys curved oppositely to the major key and built by sec- ondary currents from the west-southwest. The living barrier reef of southern Florida in front of the main Florida Keys stands in about 5 to 7 fathoms of water. The Colorados Barrier Reef of western Cuba stands in about 5 to 6 fathoms. The barrier range off northern Yucatdn, however, stands in 20 to 30 fathoms, nearer to the edge of the shelf than to the mainland. The Florida Keys are partly coralline, partly of other origin (Cooke 1945, pi. 1, and 1939, pp. 68-72). The main eastern Key range is con- sidered to be a former barrier coral reef of the elevated Pleistocene Pamlico (25-foot) shoreline, now emerged and dead. Its highest present natural ground elevations are said to be about 18 feet above present mean sea level. This Key range ends to the southwest in the Boot, Mara- thon, and Vaca group of Keys. Westward along the line of the Keys, there is a large emergence of the Miami oolite limestone stratum to the present intertidal zone, somewhat built up, in places, by mangrove peat and marl. Marine carbonate and paralic deposits combine to form the Pine Island group of Keys. This low island mass has been broadly and abundantly channeled in a northwest- southeast direction by the strong tidal currents produced by the regularly recurring tidal differ- ence of 2 to 3 feet between the Gulf and Florida Straits. Key West is the western terminus of this group of channeled-shoal Keys. West of Key West and the Pine Islands lie the small Sand Keys (Davis 1942) where the main Miami oolite shoal lies below or mainly below low tide. These Sand Keys only sparingly fill the gap between the Pine Island Keys and the large Mar- quesas atoll. Scattered coral patches. — The scattered patches of coral growth mapped by various agencies and persons along the northern coast of the Gulf (fig. 14, Sector 4.3), far out on the shelf are not \vell known. These notations may refer to growths on the tops of small salt-dome-like seamounts found along the edge of the shelf here. Studies by H. C. Stetson show that nodular algal lime- stone balls are common on the tops of some of these small seamounts. Specimens of solitary corals, possibly from the sea areas, are found sparingly upon the beaches. Coral patches occur widely 259534 0—54 5 as bottom growths off the central peninsula coast of Florida. Paralic, or marine marsh and swamp subdivisional eninronment. — In the biogenous environment, as here defined, grassy to reedy marsh is dominant between the convex areas of drowned karst shore- line (fig. 14, Sector 2.1). It is also scattered among the mangrove swamps. The mangrove swamp forests (Davis 1940, 1942) form a conspicuous marginal coastal belt on the inshore sectors noted (4.1, fig. 14), and occur prominently in thelagoonal habitat on 4.1 and 4.2 Sectors. Fresh-water marsh (paludal environment) has some of its most extensive known developments on the broad, very gently sloping coastal plain of southern Florida inland from the marine man- grove shoreline. The paludal areas include the famous Everglades and the almost as well known Big Cypress Swamp. Marine marshes (paralic) are conspicuous in places in a relatively narrow zone along the coast of Louisiana in the deltaic alluvial environment. Here salt grasses {Spartina) and reeds have pioneered on deltaic and other shoals. Garden Island Bay, between two mouths of the Mis- sissippi's active bird-foot delta, is reported (Russell 1936) to have extended its shoreline materially by the aid of paralic vegetation. Here, again, extensive fresh-water marshes lie inland in a very gently sloping coast from the more notable saline marshes. On the steeper deltaic coast of the western Gulf, shore and coastal marsh are narrow and relatively inconspicuous. Mangrove swamp growth. — Charts of the near- tropical coast of Florida (4.1, fig. 14) south of Cape Romano (1113, 1253, 1254) and north of the Bay of Florida, and air photographs of a part of the west coast of the Yucatdn Peninsula (4.1), show a broad, belted disposition of saline man- grove swamp forest with an irregular brackish lagoon or line of lagoons landward from it. This arrangement seems to be unique for North America and for those parts of the Antilles which have been studied by the writer. It depends upon the presence of a broad, shoal continental shelf in a tropical or near-tropical sea. Lesser mangrove growths on lagoonal shores seem to be incomplete approaches to this disposition of the swamp. Mangrove swamp forests extend along the coasts of the biogenous sectors (4, fig. 14) with an extension on the drowned karst (2.1), and on the 52 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE southwestern Gulf coast (1.11 and 3). The swamps occur either in lagoons or on outer coasts that lack beaches or cliffs. It is along the beach- less and cliffless coasts, in quiet shallow waters, that the unique mangrove ridge and lagoon are found. Davis (1940) reports the growth on Florida as one of the greatest known. The tropical and near- tropical mangrove forests of the main biogenous environment are dominated by the red mangrove {Rhizophora mangle) and the white buttonwood or white mangrove (Laguncularia racemosa) . Inland from the widely flooded zone, the black or honey mangrove {Avicennia nitida) grows. The latter outruns the other mangroves into the marginal tropical regions north of the main biogenous environment. The black mangrove grows as far northwest as the Chandeleur Islands of Louisiana off the eastern part of Mississippi delta and in spots in the Laguna Madre near the mouth of Rio Grande. In the mangrove forests of southern Florida numerous other trees and plants grow with the mangroves (Davis 1940). The fact that red mangroves build out the shores on which they grow has long been known to geologists (Vaughan 1909). The abundant roots and the manner of seeding on shoals by the floating of well-sheathed seedlings aids these trees in occupying marginal marine and lagoonal areas in protected waters (Davis 1940). The black man- grove, however, seeds immediately under its branches, and tends to grow toward land from a shoreline fringe, rather than outward. The mangrove barrier ridge and coastal lagoon. — Chart 1113 shows an extremely irregular outer shoreline beginning at the north with the Ten Thousand Islands archipelago. This belt of islands starts at the northwest in the coastal lagoon behind the Cape Romano barrier spit. It then curves to the southeast to end at Lopez River. From Lopez River southeastward to Cape Sable the mangrove swamp of the outer coast is mapped as being much more compact than in the Ten Thousand Islands, and is smoother, but far from regular. It is broken by transverse marshy channels and has, in the northwestern part, an outer line of islets and small peninsulas. From 3 to 8 miles inland, there is a zone of highly irregular, more or less intercommunicating swampy lagoons and channels running roughly parallel with the outer coast. Between the inner lagoons and the outer coast, there is a broad belt of man- grove swamp which is the ridge. Davis shows that the height of the ridge should be a function of both tidal range and the slope of the bottom and adjacent land surface across which the man- grove belt originally spread. The entire coast southeast of Cape Romano (4.1) is composed of mangrove swamps and la- goons except for the sandy barrier islands, spits and beaches of the Cape Romano barrier at the northwest and of Cape Sable at the southeast. The delineation of shorelines for the mangrove forest is difficult (McCurdy 1947) because of the indefiniteness of shoreline position for a marine swamp, especially where the tidal range, as here, varies from about 2 to 4 feet. East of Cape Sable, there is a mangrove belt along the north side of Florida Bay. The mangrove peat rests on limestone rock, marl, or shell beds (Davis 1940). The peat sec- tion varies from about 5 to 14 feet. Except where it descends into depressions in the karst, Davis thinks that the general average thickness is about 7.5 feet below mean low water. This would place the base of the peat at an average of 8 feet, or slightly more, below mean sea level. The red mangrove seats itself in as much as 2 feet of water, the roots spreading outward somewhat. The seedlings float and ground in a few inches of water. There was in many cores taken by Davis through the peat, an alternation of peat and marl, with an upper marl bed a foot or two thick present in most of the area. The roots of the present swamp trees penetrate this upper marl but without peaty development in it as yet. Alternations of marl and peat in a core may or may not indicate a ver- tical oscillation of sea level, as they, certainly in some cases, have been due to compaction or minor horizontal shoreline changes under essential still- stand of the sea. The history of the formation of the mangrove barrier ridge and lagoon may be somewhat as follows: On a broad, well-protected tropical to subtropical shoal coast, especially, as m Florida, where the wind is dominantly offshore but swell and some on-shore wave movement is present, ad- vance of the mangrove forest is assured. The elongated, winged, pod-shaped seedlings ground and take root at any depth down to 6 to 8 inches of water. Root growth may extend as far offshore as a 2-foot depth at low tide (Davis 1940). The dense growth of roots, trunks, and associated veg- GULF OF MEXICO 53 etation, slowly advances seaward by the consoli- dation of peaty growth and by trapping fine- grained inorganic sediment (Vaughan 1909). Shells are added by the accumulation of small species of Mollusca on the roots (Davis 1940). It may be assumed that the maximum of accumula- tion of marl, clay, and silt takes place always somewhat forward, that is, gulfward, in the slowly advancing swamp. Storm waters and tidal os- cillations combine to permit the up-building of the accumulating swamp materials by those inor- ganic sediments which, in turn, may promote, at and above high tide levels, a denser undergrowth of the less aquatic plants. As the zone of maximum arrest and accumula- tion of inorganic sediment advances Gulfward, lack of accretion or a decrease in rate of accretion in the zone nearer the original mainland permits normal compaction of peat and marl to show in an invasion of groundwater and brackish marine waters. The swamp is abundantly penetrated all along the western peninsula coast by transverse tidal scour channels, permitting Gulf waters to enter the rear zone. If the foregoing processes and results depict the true history of the formation of the mangrove barrier ridge and lagoon on the western coast of peninsular Florida during the stillstand for the 3,000 to 5,000 years of Fisk's (1944) determin- ations, then the considerable width of 5 to 10 nautical miles of the mangrove belt is a product of the extended period of time during which ap- proximate stillstand has persisted. If minor oscillations have occurred during this period, then some of the alternations of peat and of peat marl and in the types of peat reported by Davis may have been related to changes of sea level. An end condition of seaward advance may be found where the bottom slopes too steeply, or the growth has finally reached a zone where the processes outlined no longer produce bottom offshore that I is sufficiently shoal to support mangroves. Under I this hypothesis, we may understand why the man- i grove growth on the southern part of the Gulf i shore of Florida is exceptionally wide, as the ! combination of conditions required for the full I formation of a mangrove ridge and lagoon are exceptional. Under this hypothesis the rate of Gulfward advance is the ratio between the width of the ridge, 30,000 to 50,000 feet, and the dura- tion of stillstand, 3,000 to 5,000 years. Using the figure 5,000 from Fisk's estimate, we find that the net outward advance of the mangrove forest has been between 6 and 10 feet per year. This is a measurable quantity- It has been said that Davis (1940) finds the present swamp forest to be resting on and rooted through a surficial zone of marl a few feet thick without appreciable peat deposition in it. Hence, his interpretation that the accumulation of the average of 7.5 feet of buried peat and marl took place mainly during a rise of sea level seems not to conflict with the present writer's hypothesis for forward growth during stillstand. Accumulating datings by the deterioration of radiocarbon may permit a rate of upward growth, less compaction, to be made, Davis having found no means of doing so. The mangrove barrier ridge and coastal lagoon are similar, in accomplishing appreciable shoreline prograding, to the other barriers known, the barrier island of sand, the barrier coraline reef and the rare barrier oyster reef, noted in the Gulf of Mexico where a large reef of Crassosfrea virginica forms a bay barrier 25 miles long across the mouth of Atchafalaya Bay. EMERGENT AND SUBMERGENT SHORELINES OF THE GULF USE OF TERMS Johnson (1919) laid much stress, in his shoreline studies, on the determination of whether the features of a shoreline were dominantly those of the relative submergence of a land surface or the relative emergence of a sea bottom. His interest centered in the immediate history of sea level and its effect on shorelines. Others have found it impracticable to discriminate entirely on many coasts between the exact form of the present shoreline and the topography of the coastal zone which has determined major features of both coast and shoreline (Shepard 1937a, Price 1939). This distinction involves the difficulty in deter- mining for each sector whether the several sub- mergences or emergences of the coasts during the Pleistocene have produced its dominant features. A major shortcoming of the Johnson classifica- tion or the way in which it came to be applied was its use of the common and widely developed barrier island as either a major criterion or a 54 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE positive indicator (Price 1939, Johnson 1938) of emergence. Later work, here discussed, seems to invahdate this criterion entirely as an indicator of sea-level movement except where it may be found wholly emerged or submerged. While not finding the concepts of submergence and emergence as valuable for shoreline classifica- tion as some others, we may well inquire what features plainly indicate such items of shoreline history. SUBMERGENT SHORELINE FEATURES Pleistocene entrenchment oj stream valleys. — It is well established that the accumulation of lai-ge amounts of ice in the arctic and circumarctic regions several times during the Pleistocene, or Great Ice Age, caused strong lowerings of sea level. The latest well-established major lowering occurred in the late Wisconsin or Wiirm glaciation and amounted to about 450 feet in the Gulf of Mexico (Fisk 1944, 1952) and the Gulf of Paria, south of Trinidad, Venezuela." In some regions the figure is set at between 240 and 350 feet (Flint 1947). Fisk (1944, 1948, 1952) has shown by borings cited in various reports of the Corps of Engineers that the northwestern Gulf coast had a large number of entrenched Pleistocene stream valleys that have now been filled with sediments. Configurations of branch estuaries show that entrenchment was general in the Gulf. Only on the hard shelf off peninsular Florida are such valleys found submerged and fairly well outlined by depressions. These valleys are marked by depths of as much as 10 to 15 feet on the coast charts off northern peninsular Florida. Embayed drowned valleys. — Incompletely filled drowned valleys in the Gulf take at least two forms, those in which the branching, dendritic pattern of drowned tributaries is still prominent (Baffin Bay in Texas) and those in which waves and currents have broadened the valley at shallow depth, producing oval, rounded or other equidi- mensional shapes. The writer (Price 1947) has shown that on the northwestern Gulf coast elon- gated drowned valleys tend to become segmented by spits and other obstructions, separately em- bayed by segments and the bay bottoms made flat under a dynamic equilibrium between erosion and deposition. This equilibrium of basin shape » Personal communication, T. H. Van Andel. is actually the result of the formation of equilib- rium bottom-profiles along most bay radii. Embayment of drowned streams is most prominent in the Gulf on the compound Pleisto- cene-to-Recent deltaic coast of Texas and south- western Louisiana. There, the rivers are large and the gradient of the Beaumont is not steep (1 to 3 feet per mile). On the steeper plain of Sector 1.2 (fig. 14), only one large, transverse valley bay (Mobile Bay) occurs. Where the plain is composed dominantly of active deltas or hard rocks or has only relatively minor streams, Sectors 1.11, 2.0 and 3.0, long broadly embayed stream valleys are absent. The writer has further considered local meteorological influences in the shaping of the bays of the northwestern coast (Price 1952). The harbor of Matanzas, Cuba, is thought to be a drowned valley cut in a structural depression or in a structurally weak zone. Submerged base of mangrove peat. — Davis' (1940) conclusion that the mangrove swamps and peat of Florida formed during a gradual, more or less uninterrupted rise of sea level from about —8 feet relative to mean sea level has been mentioned. Drowned lacustrine plain oj Florida Bay. — Anaylsis of this unusual type of marine area needs somewhat extended exposition. The entire water area (Trask 1939, pp. 292, 293) is a honeycomb of shallow, rimmed basins individually upwards of 10 miles wide and 11 feet deep, the bottoms bare with a cover of soft marl or shell sand. The narrow rims are of marl and mangrove peat (Davis 1940). The writer's interpretation is that a rising sea moving up and across a very gently sloping shoal surface carried with it a transgres- sive shoreline zone of mangrove swamp. This coastal swamp belt, the mangrove ridge, moved slowly north and northeastward and is now present along the north shore. This ridge is of irregular shape and the marsh and swamp back of it to the north are now and were probably at all times honeycombed with lakes. Such lakes tend to become enlarged by wind scour if the banks are not encroached on too strongly by marsh and swamp growth. The result is that some large lakes occur among the innumerable small ones. It is further postulated that, as the Gulf waters invaded the swamp, more and more deeply, vegetation was slowly killed, and the lakes gradually widened by drowning and wave erosion. p GULF OF MEXICO 55 The outlines of the lakes and rimmed basins of Florida Bay today show the characteristic coa- lescing of small basins with each other and with large ones, the intervening rims being removed. The lacustrine plain, the so-called bay, with its network of marl ridges prevents the development of appreciable tidal flow and scour in and be- tween basins except along the border of the bay at the south. Here tidal channels have been scoured through breaks in the line of the Florida Keys, locally deepening the rimmed basins. Statistical study of the relation between width and depth in the rimmed basins shows a rough approximation to the progressive deepening with increasing size characteristic of the bays of the northwestern Gulf (Price 1947). In the Bay of Florida this relation is modified on the southeast by the limiting depth of the hard Miami oolite and at the extreme west by an excess of sandy or marly deposition in the relatively large basins that there border the Gulf. Some of the western basins are completely filled with sediment. Partly submerged eolian sand plain of Rio Grande delta region. — Stretching inland across the Pleistocene plains of this delta in Tamaulipas and Texas to their inner erosional scarp is a plain of eolian sand, or erg, with scattered dune fields. All, except small blowout fans of bare sand (about 1 by 3 miles in size) and their fields of bare dunes, is stabilized by grassy vegetation, thorny brush and live oaks. The coastal lagoons now form traps for eolian sand blowing inland from the beaches of the barrier islands. Only in droughts is some of this sand able to cross to the maiidand over narrow flats that locally close the coastal lagoon. This immense sand plain must have come on shore before the barrier island was formed. The simplest explanation follows that of Daly (1934, pp. 197-201) that large amounts of sand probably blew on some shores when the sea level was low during one or more of the glacial periods. Other possible explanations are that the sand has come from the reworking of successive barrier island sands and other beach deposits or from sandy sediments in the walls and on the floors of entrenched valleys. EMERGENT SHORELINE FEATURES Pocket harbors (emergent rimmed basins) of Northwestern Cuba. — Several writers on Cuba (as Hayes, Vaughan, and Spencer 1901) have referred to the purse-shaped or pocket harbors of Cuba. Tliose of the sector from Havana to Bahia Honda (fig. 12) on tiie northwest coast are of an unusual, petal-shaped type. They lie in a plain from 3 to 5 feet above sea being upwards of 6 miles long. A small stream usually enters one or more of the several marginal indentations of the small rounded-to-oval basin, not always in the axial position. Other similar marginal indenta- tions have either no appreciable inflowing drainage or receive very slight drainage. Yet well-formed submerged channels converge from all these in- dentations toward a central channel of tidal type. This channel may be as deep as 8 fathoms. Such harbors do not seem to the writer to be explicable as normal embayments of drowned stream courses or of stream confluences, as some have suggested. If the coast of Cuba west of Bahia Honda (3.1, fig. 14) is examined on the navigation charts, basins similar to the pocket harbors and the rimmed basins of the Bay of Florida, lying in swampy terrain, will be seen here and there be- hind the Colorados Barrier Reef, mostly clustering toward the mainland shore. These basins have axial or radial tidal channels draining to the Gulf below sea through passes or breaches in the reef. These small, rounded and rimmed basins of the Colorados lagoon seem to be features of a present mangrove-lined shoreline like those along the north shore of Florida Bay. The writer inter- prets the pocket harbors of the Havana type, surrounded by a slightly elevated plain (Palmer 1945), as similar mangrove lakes scoured out at sea level in the midst of a saline swamp and then slightly elevated on the unstable young orogenic coast (Sector 3) of Cuba. Barrier Island not an indicator of long-period sea-level change. — Johnson (1919, 1925) thought that his offshore bar, called barrier island by the writer (Price 1951a, Shepard 1952), was a feature predominantly of an emergent shoreline. He be- lieved that the structure was formed by a semi- permanent sea level change, a slight worldwide lowering of sea level or an upwarping of the crust, along an offshore bar formed originally as a sub- marine feature. Fenneman (1938, p. 4), following some early writers, believed, however, that a barrier island was formed merely as an equilibrium structure produced on a shallow shelving coast by the balance between wave attack and bottom re- sistance regardless of any history of sea level 56 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE change. The writer's study of bottom profiles in the Gulf (fig. 15) indicates that barrier islands are (1) associated with well-developed equilibrium profiles, (2) on a shallow coast where the bottom is now at least 15 to 45 feet deep within one to two miles of shore and (3) thereafter slopes out- ward between about 2.0 and 5.0 feet per mile, (4) where sand, gravel or cobble are abundant along shore, and (5) where onshore wave attack is strong. These observations tend to confirm Fenneman's interpretation. Other observations, briefly stated, indicate that the barrier island does not require a worldwide or other semipermanent fall of sea level to bring it above sea, but that the only change in level needed is a local, short-period change be- tween storm levels and normal sea levels taking place during periods of a few hours or days. A series of aerial photographs taken at intervals of several years over the period 1934 to 1949 (Bates 1953) shows that a bar formed just below the intertidal zone off a new mouth of Brazos River remained submerged until a hurricane had occurred, after which it became a typical emergent barrier island of cuspate outline. A second bar then formed off a breach in this bar- rier, after which other hurricanes occurred before the second bar was, in turn, raised above sea to form a second line of emergent barriers. The inference is strong that, in each case, a pre-existing submarine bar was built higher during a hurricane, so that during the storm it bore the same height relation to the elevated storm sea level as it had formerly borne to the normal level of the Gulf. The bars emerged as barrier islands after the subsidence of the temporarily high sea levels. On October 3, 1948, a hurricane passed about 100 miles off the coast of southwestern Texas, causing a high sea level or storm tide of some 3 or 4 feet for two days or more along the barrier islands. A week later, the writer found that the summit of the beach, the beach ridge, in front of the shore dunes had been built up and remade by the storm and was slightly farther inland than its former alignment. The shift in position was evi- denced by erosion of dune faces. The convexly rounded beach ridge then rested where the front part of the dunes had been. The raising of the beach ridge, previously described, to an elevation above its position during normal times was shown by the rapid mass-wasting that had affected it in a single week. The beach ridge on this island formerly had, in places, a fairly well developed pavement of shell, but now the pavement had just begun to be formed on the newly made ridge. The pavement was formed from disseminated shell by the washing and blowing away of sand, according to a well-established process. It was evident that this ridge had lost some 6 inches of its height and would lose another foot or a foot-and-a-half before a pavement would be formed to protect it. The former paved beach ridges had evidently lost similar heights. Reports and illustrations of hmricane damage to New England beaches (Brown 1939, Howard 1939) show that the beach ridges were remade at higher levels, moved inland from their forvier positions and their axes rotated slightly by the « hurricane waters. These observations indicate clearly that the summit ridge of a barrier island functions briefly during storm tides as an underwater offshore bar and thereafter emerges as a barrier island. Evans (1942) found that waves operating at a steady sea level tend to modify the slopes and positions of underwater bars, but not to build them up above water. The great development of active barrier islands on the Gulf coast, dominating the shorelines of the alluvial sectors (1, fig. 14), does not then, in the writer's opinion, tell a story of permanent or semipermanent sea level change, or mark either a submergent or an emergent shoreline condition. The question of the source of the supply of material for the barrier, long thought to be a critical factor, is found to be secondary. Thus, barriers occur in the Gulf where longshore sedi- ment drift is prominent (Sectors 1.12, 1.2, fig. 14) the sand derived largely from rivers (Bullard 1942), also where a longshore drift from a land connec- tion (Chandeleur Islands, La.) is absent and where no land-derived sediment is present but onshore waves are strong and the barrier is built of broken shells from the adjacent bottoms, as on the north shore of Yucatan (2.2, fig. 14). Emergent shoreline terraces and notches. — The lowest well-established elevated shoreline is that of the Pamlico of the Atlantic coast and Florida, standing at about 25 feet above mean sea level. This shoreline is marked in many regions by a well-cut and well-preserved terrace or by a broad elevated lagoon flat with a barrier island. Less GULF OF MEXICO 57 well-developed and somewhat controversial shore- lines are reported from manj- places in the interval from about +3 to +10 feet. However, carefully selected, stable, protected, inner shoreline sectors on North Pacific Islands (Stearns 1941, 1945) and in Australia (Fairbridge 1948) exhibit shoreline cliffs in even-grained limestones with solution notches at about +3, +5 and +8 feet. These seem to represent worldwide stillstands of the sea (eustatic shorelines). Shorelines reported at + 16 and +20 feet (Daly 1934 and others), are not as yet substantiated by data of unquestioned accuracy. In places around the shores of the Gulf, there are definite indications of shoreline terraces that seem to indicate stillstands at about +5 and +8 feet. An elevated barrier island and coastal lagoon caught by the 10-foot contour has been mapped in Florida by MacNeil (1950) as the "Silver BluflF shoreline" (Parker and Cooke, 1944, pi. 4, fig. B). He did not follow it across southern Florida or on the west side of the peninsula. Low shoreline flats appear in many places around the Gulf, but have not been critically studied in the field. Such a low bench shows in air photo- graphs along the base of the high bluffs of the Champoton-Campeche limestone fault-block sali- ent (fig. 12; Sector 2.2, fig. 14). It seems to have a gray, sandy soil. A flat along the front of the elevated Ingleside shoreline between the Rio Grande and Brazos-Colorado deltas (fig. 12) lying at irom about 1 to about 5 feet above mean sea level has low, subdued spits and bars on its sur- face '* and seems to be an emergent marine plain. It is about 0.3 mile wide. This flat may be a nondeltaic part of the original Pleistocene surface in front of this barrier. Deltaic deposits appear along the Gulf side of this barrier east of Galveston Bay. Marsh borders the Pleistocene delta of Brazos River in Texas to an elevation of 2 to 3 feet above mean sea level. Just behind the marsh is a bench 1.0 to 1.5 mile wide at 3.0 to 4.5 feet with a low nip or wall between 4.0 and 6.5 feet above sea. This bench may be a low Silver Bluff representa- tive. At Buhler, a few miles northwest of Lake Charles, Louisiana, the Ingleside barrier and lagoon clays are well preserved. The top-of-clays, " Obscured by mima (pimple) mounds higher and wider than the spits (Price 1949). representing the approximate shoreline position, lies between 22 and 25 feet above sea. This shore- line and the associated features are well defined running at the same elevation from near Lake Charles west to Beaumont and thence southwest through Fannette, Jefferson County, Texas. Where the shoreline comes within about 10 miles of Anahauc, Chambers County, it is sloping down to the southwest at about 1.5 feet per mile and reaches sea level at Smith Point on the shore of Galveston Bay. Before the formation of the bay, it was formerly tied there to the Brazos delta. The Ingleside shoreline seems to correlate with the Pamlico through the emergent barrier of Gulfport and Biloxi, Mississippi. The deltaic plain lying south of the Ingleside in southwestern Louisiana and in Jefferson and Chambers counties, Texas, is of the same age as that immediately to the north of it, Prairie or Beaumont (Hayes and Kennedy 1903, pp. 27-38; Deussen 1924, p. 110). Along the shore of Jeffer- son and Chambers counties, it is a partly sub- merged deltaic plain. The Ingleside appears again south of the Brazos-Colorado delta along the coastal lagoon that opens from Matagorda Bay at its southeast extremity and runs from there to the north flank of Rio Grande delta, the shoreline (top of clay) being at approximate^ 5 to 10 feet above sea. The disagreements in the shoreline data for the northern Gulf coast would be removed if the coast from Florida to the Mississippi delta had been stable since Pamlico time, but a slight amount of gulfward downwarping had occurred between the vicinity of Galveston Bay and the coast of Mexico at some point north of Tampico. The post-Pleistocene gulfward downwarp of the Beaumont Pleistocene plain (Doering 1935) in- creases in amount from about 1 foot per mile in southeastern Texas to 2 feet per mile southwest of Matagorda Bay. This downwarp seems to mark the influence of the young orogenic coast of Mexico, which it is approaching.'^ This interpre- tation suggests that the emergent shoreline flat on the Gulfward flank of the Ingleside barrier may be either of Ingleside age, down warped some 15 feet, or a younger post- warping shoreline, possibly of Silver Bluff age. Against a Recent age for the low bench is the seeming absence of marine fossils '" Corpus Christi lies 175 miles east of folded Cretaceous rocks at the surface iu Meiico and 125 miles northwest of submerged mountains in the Gulf. 58 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE above present sea level in the much cored and studied post-Pleistocene alluvial fill of Mississippi River in the Atchafalaya river basin, Louisiana (Fisk 1952). No unquestionable evidence seems yet to have been offered that elevated, unwarped (eustatic) shorelines below +25 feet are of Recent or post- Glacial age, despite continued statements by many geologists that they "seem to be Recent." R. W. Fairbridge and E. D. Gill of Australia " think th at the materials of the shorelines of Australia below +10 feet are not sufficiently weathered and leached to have been formed before the last major sea level lowering. On Chesapeake Bay, G. F. Carter '* finds no post-Pleistocene deposits above a maturely developed soil, supposedly of post- Pleistocene age, which dips beneath bay sediments and has been cored into off-shore. We do not know that the shores of the Chesapeake have been down warped. The Pamlico terrace is reported as running level along this coast from Maryland to Florida. The only dated shoreline deposits above sea level that are thought to be of historical or earlier Recent Age of which the writer has been able to learn, come from young orogenic coasts, as that of Tripoli '° in Lebanon (Wetzel and Haller 1945) and on the Pacific coast of South America. These coasts must be suspected of having had crustal movements going on at any time, even in recent millenia. Thus, Jerico, 175 miles southwest of Tripoli, was once destroyed by an earthquake and 200 historical shocks are reported for the area of Israel (Ball and Ball, 1953). SHORELINE CHANGES AND PROCESSES SHORELINE SIMPLIFICATION Terminology.— Shep&rd (1937a; 1948, pp. 70-73) says that "as numerous coasts and shorelines have undergone little modification since the sea level and the land came to rest, it seemed logical to re- fer to these as Primary . . . and to . . . those which have been considerably modified by the waves and currents as Secondary ..." In his tables he calls "primary" shorelines youthful and "secondary" coasts mature. Following this con- cept, we find that mature marine coasts have in " Letters of 1952. " Letters of 1952. '• At 2 to 3 meters above sea 600 m. inland and possibly 3,000 to 4,000 years old. general become simplified in contour, with their irregularities reduced by erosion, solution or sedi- mentation, or a combination of processes. Hence, the end I'esult of marine action on most types of coasts is smoothing, though not always straighten- ing, as smooth coasts may be curved. Processes. — Simplification of a coast may con- sist of the reduction of projections by erosion, and the deposition of beach and other deposits in re- entrants. It may also be brought about by the formation offshore in shallow water of a barrier island or barrier spits (Price 1951a, Shepard 1952). Such inorganic barriers tend to follow along a bot- tom contour, crossing the sites of entrenched valleys on postentrenchment fill, while the main- land shoreline is deeply indented by the shallow embayments of the former valleys. Thus, the new marine shoreline is smooth and shorter than the mainland shoreline off which it is built. Examples. — Simplification of Gulf shorelines is shown by (1) extensive development of sandy bar- riers where there are or were irregularities of the mainland shoreline, chiefly between the convexities of deltas (Sector 1), (2) the gradual filling of coastal lagoons (as east of Galveston Bay, sector 1.2), (3) the incipient smoothing of projections along some sectors of the drowned karst coast (2.1), (4) seem- ingly some smoothing of the front of parts of the mangrove ridge (Sector 4.1) facing the Gulf, in contrast with a possibly irregular original con- figuration such as that of the Ten Thousand Is- lands or the north shore of the Bay of Florida, (5) smoothing of the karst irregularities of the elevated Champoton-Campeche fault-block (Sector 2.2, Yucatdn peninsula) so that only small cuspate points remain, (6) reduction by erosion of project- ing folded limestone rock (northern Sector 3.1) and of the ends of narrow tongues of lava solidified to rock extending into the Gulf from the active volcanic salients of the young orogenic coast of Mexico (southern Sector 3.1). Signijicance . — The several degrees of shoreline simplification evident in the preceding list, sug- gest a considerable quantitative range in the effective application of marine energy to shoreline modification during the 3,000 to 5,000 years of essential stillstand of the Gulf. Just as we find variation in simplification related to the hardness and resistance of the shoreline materials, rocks or soft sediments, so we may suspect that there have been differences in the amounts of energy available GULF OF MEXICO 59 for shoreline work. This supposition is justified by (1) the consideration that erosion at the shore- line has a vertical as well as a horizontal com- ponent, (2) comparison of variations in the form and offshore gradients of the bottom of the continental shelf on various sectors of tlie Gulf, and (3) inspection of the charts of resultant winds along: the shorelines of the Gulf (U. S. Weather Bureau, 1938). These factors indicate that it may be feasible, from the partly quantitative, partly qualitative data presented or referred to here, to set up a preliminary energy classification of the coasts and shorelines of the Gulf of Mexico. This is attempted in the tabulation. Extensive Marine Modification of Coasts of Gulf. — A summarj' of prominent shoreline condi- tions that indicate the degree of coastal modifica- tion is shown in tabular form below. The simpli- fied coasts (the secondary or mature coasts of Shepard) greatly dominate in linear distribution, indicating that the sea has been at about the same level for a substantial period of time in relation to the resistance of most of the coastal materials to shoreline modification. Percenfage Approximate of marine length in shoreline /-, ,r J . . statute miles length (juIi and major parts: Marine shoreline 3,000 100 Coastal plains 2,500 *3l Volcanic and other sectors 500 17J Secondary shorelines: Simplified (smooth) 2,250 75] Moderately smooth 250 SflOO Little modified 500 17] Sandy beach 1,553 52 Barrier islands and bay bar- riers 1,370 46 Inactive and elevated beach plains 810-1- 27 + Beach ridges, average of 10 (?) ridges per beach 20,000+ 667 + EQUILIBRIUM PROFILE OF CONTINENTAL SHELF BOTTOM Definitions. — Figure 15 shows bottom profiles for sectors of the continental shelf having different steepness of curvature. Only for the broad shelves off the alluvial and limestone plateau coasts (fig. 14, Sectors 1 and 2) of the Gulf of Mexico are there enough data for analysis. On the shelf sectors studied, the profile of the bottom is concave in the first mile or two, this section being the shoreface, an extension of the beach or other shore. The shoreface grades into a nearly smooth plain, here called the ramp, the gradient of which flattens slowly in an offshore direction for varj'ing dis- tances, commonly to 30 fathoms or more. The profiles drawn on this section of the shelf are math- ematically of the hyperbolic or asymptotic type, the so-called logarithmic or exponential curves. The ramp grades, usually far offshore, into a usually smooth convex section, here called the "camber," the gradient of which usually increases rapidly to the top of the irregular, steep, conti- nental shelf slope. The sparse soundings available for the shelf of the young orogenic coast of Mexico (3, fig. 14), suggest that, except where a beach or barrier is present, this coast may lack a ramp, the camber beginning at or near the base of whatever shore cliff or shoreface is present. The so-called shelf break (Dietz and Menard, 1951) should be the junction between ramp and camber. Data showing the locations and ramp slopes of the profiles (curves) of figure 15 and the sectors on which the curves are located are given in a tabulation following the illustration. Location of profiles in figure 15. — All profiles measured perpendicular to shoreline from naviga- tion charts U. S. Coast and Geodetic Survey. (1) Off old Corpus Christi Pass and Padre Island barrier island 27°35' N. Lat., 97°13' W. Long. Chart 1286, 1922 edition. A profile at same place from original survey sheet (1880) shows only minor irregularities and smoothly asymptotic curvature to 90-foot depth. Beach. Sand and clay bottom. (2) Off Padre Island at Baffin Bay mouth, 27°I8' and 97°20'. Chart 1286, beach sector: "Little Shell." Beach. Sand and clay bottom. (3) Off Matagorda Peninsula barrier island, off mouth Trespalacious Bay, 28°00', 96°10'. Chart 1284, 1945 edition. Beach. Sand and clay bottom. Fathogram off Galveston shows ramp as smooth as curves 1-3. (4) Off barrier island on Florida peninsula 10 miles north of Cape Romano, 26°03' and 81°48'. Chart 1254, 1931 edition. Beach. Sand inshore. Rock bottom (limestone) with some sand and shells. (5) Off Pine Islands-Key West shoals (Miami oolite with mangrove swamp deposits above), Florida, at Johnson Keys, 24°42', 81°36'. Chart 1251, 1940 edition. Profile begins at -8 feet. Add 8 to all depths for this curve in figure 15. 60 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 20 UJ 40 UJ 60 80 90 10 20 en t-ioo UJ 200 STATUTE MILES 4 6 8 10 12 ^ 1 1 5 THEORETICAL. SECTOR I ^ 1 7 6 ^i!:^i^ ^ ^ ^ 5 "'^^^'^--~^^:^ 5 5 ^ -^ 2 SECTOR "4~~ ^^^^==^t:r--^ SECTOR m~P' 3 ^ P=::^^r^^ 1 _ ^~-*-~^r^^ 1^^--- 2 20 40 60 80 90 STATUTE MILES 10 15 20 ^ ^^ -<.^ ^rrs^_ \ X THEORETICAL-" 7 ^ \ ~o - V 1 --,-._ ^ SECTOR I^^*^ \6 50 KILOMETERS IC )0 25 10 20 30 40 Figure 15. — Characteristic bottom profiles of inshore zone, continental shelf, north half, Gulf of Mexico. Steepening and progressive smoothing of bottom from profile to profile correlates with increasing energy of water, decreasing resistance of bottom, and increasing steepness of initial drowned surfaces. The theoretical low-energy, breakerless profile of Keulegan and Krumbein (curve 7) is compared with a beachless sector of drowned karst coast off Florida (curve 6). Profiles are listed on pages 59 and 60. Sectors are described in tabulation, pages 61 and 62. The shore- face extends 1 to 4 miles offshore. The ramp extends out from the shoreface as far as the profile continues to flatten. The outer parts of profiles 1 and 2 are averaged between the points shown. Bottom "hard," mostly oolite limestone. Little sand reported in region. Beachless. (6) Off rocky coast of Florida at Net Spread Key between Chassahowitzka and Weekiwachee Rivers, 28°38', 82°40'. Chart 1258, 1944 edition. Beachless. Hard bottom (limestone). Very few notes of sand in region. (7) Theoretical mathematical curve of Keulegan and Krumbein (1949) for the steepest bottom across which waves will move with the maximum height without breaking. A wave 3 m. high enters the shelf-sea on a bottom 4 m. deep 40 km. from shore. Depth equals the 4/7 power of the distance from shore. A hyperbolic curve. GULF OF MEXICO 61 Table 1. — Gradients of ramp shown in figure 15 Proaie Oradi- ent Statute miles from shore Depth in ^t Sector of Oulf 7 . 2.0 1.7 0.6 0.4 0.3 1.5 I.O 2.0 2.4 2.2 6.0 3.0 2.7 5.0 4.3 3.5 3.6 0. 1- 0. 6 .6- 2.2 2. 2- 7. 4 7. 4-15. 15. 0-25. 0-4.0 -13.0 13. 0-27. 0. 7-12. 0.9-11.0 1.0- 4.0 4. 0- 8. 5 4. 0-12. 1.8-12.2 4.4-12.2 1. 8-12. 2 3. 6-12. 2 0.5- 1.6 1.6-3.3 3. 3- 6. 6 6. 6- 9. 8 9. 8-13. 1.0-7.0 1.0-10.0 10. 0^0. 7. 0-21. 20.0-40.0 25.0-44.0 44. 0-57. 44.0-67.0 41.0-87.0 54.0-87.0 45. 0-83. 51.0-83.0 6 bottom profile, Kcu- legan and Krumbein. I 5 4 V 3 2 VII. VII 1 VII Sedimentation and the profiles. — The shoreface, ramp and camber of the normal coastal plain shelf, as exhibited on the Gulf of Mexico, seem to have specific characteristics as to sedimentation (map, fig. 16, p. 79) and erosion. From meager data, it seems that sand and shifting bars characterize the shoreface. Contemporary sands, relict deltas and barriers of former sea levels, with some contemp- orary clay deposition, characterize the ramp. Ex- cept when the entire profile is migrating landward, transportation probably dominates the ramp after any rehct elevations have been removed from the part under consideration. Fine-grained sedi- ments, mostly land-derived clays, and presumably the process of deposition, characterize the camber. Off the mouths of large deltas, little or no coarse sand reaches the Gulf and the charts show "mud" beginning near shore. Where sand is present it usually extends to 5 to 10 fathoms (Bates 1953; Lohse 1952). Dietz and Menard (1951) have lately advanced evidence and argument for the belief that, at the level of the passage of the shelf from the steep concavity into the gentler slope, in present ter- minology, where the shoreface joins the ramp, is found the depth of maximum wave action on the bottom. They term it the depth of maximum abrasion, replacing the older concept of "wave base." If the Gulf has remained essentially at the same level for the past 3,000 to 5,000 years, as pre- viously suggested, it is evident that, on bottoms closely approximating the hj^perbolic curve the shelf bottom must be in equilibrium. This should be true especially in coastal materials of slight resistance and where large amounts of marine energy have been effectively applied. That the topography of the bottom is a simple mathematical surface with a hyperbolic bottom profile, is be- lieved to indicate that the forces are in equilibrium. Wliere the bottoms are of hard rock and largely retain a subaerial topography, it may be concluded that the marine forces have inherited a surface produced under different conditions which they have been unable to destroy or to which they happen to be more or less adjusted. The equilibrium profile of the coastal plain shelf is in a state of dynamic, not static, equilibrium. In dynamic equilibrium, variations of temporary, short-term value are to be expected. Thus, heavy storm waves are known to shift offshore bars ^^ temporarily as much as a half-mile from their previous positions on the shoreface. Varia- tion of the equilibrium will be about the mean. Marked departures from the mean are caused only by forces external to those in equUibrium. The shift of a river mouth, the coming of a lava flow, or the warping of the earth's crust, would be external forces or conditions which might upset a previously existing equilibrium on the shelf. Usefulness of equilibrium profile. — Despite some pessimism (Kuenen 1950, p. 302) as to the value of the profile in geologic studies and much mis- conception on the part of writers as to the differ- ence between static and dynamic equilibria in nature, the present writer finds that the profile of equilibrium is a suitable index of the response of a continental shelf bottom to the application of marine energy for a significant period of time. If, as some think, there have been several oscilla- tions of sea level of as much as 10 to 20 feet during the past 4,000 years or so, a proposition that re- mains unproved, then the interpretation of the modification of the shorelines and shelf by marine energy is less clear than as here tentatively presented. Theoretical breakerless curve fits Florida. — Keu- legan and Krumbein (1949) made a theoretical study of the critical steepest bottom slope in shallow water on a shelf across which waves from deep oceanic waters may move but be constantly deformed and constantly lose energy so that they arrive at and near shore without enough height or energy to break or to develop shore structures, such as beaches or cliffs. The absence of such " The true underwater feature, not the barrier island. This occured at Galveston, Teias. 62 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE shore structure along much of the western shores of the limestone peninsulas of Florida and Yuca- tan, and the low gradients prevailing there off- shore, led the writer to investigate these regions for examples of the beachless and breakerless coasts. More information is available for Florida than for Yucatan. It was found that the requisite combination of (1) unmodified or little-modified shorelines, (2) gentle offshore slope and (3) essential absence of breakers (Corps of Engineers, U. S. Army 1940) exists on long stretches (Sectors 2 . 1 and 4 . 1 , fig. 14) of the Gulf shoreline of peninsular Florida.^' By analogy, similar conditions are believed to exist on more than half the lengths of the western peninsular coasts of Florida and Yucatan, where the bottom gradient is low and the shoreline and bottom essentially unmodified by marine forces. Comparison of the theoretical "breakerless bot- tom" curve of Keulegan and Krumbein (1949), described as profile 7 (p. 60 and fig. 15) with the actual rolHng bottom profile of the drowned karst shelf of peninsular Florida (profile 6, fig. 15), shows that the two curves closely superimpose and are identical in over-all gradient. But the drowned karst profile has not been fully smoothed by ero- sion and deposition and is not yet a marine profile or equilibrium, although slight modifications of it indicate that such a development is going on. DIRECTIONS OF LONGSHORE DRIFT In the northwestern Gulf of Mexico, where a strong longshore sediment drift occurs, and wherever a barrier spit terminates, the dominant drift of the year is in the direction of the elongated, pointed barrier ends." These criteria agree there with the known histories of inlet migration, although there is a weaker summer drift to the northeast. Using spit criteria, the dominant longshore drift is seen to be westward and south- westward, that is, counterclockwise,^ from Apa- lachicola delta, Florida, to the poorly mapped volcanic sectors (Sector 3, fig. 14). Where sandy beaches and barriers occur on peninsular Florida, " The data on waves and swell are being studied at the Agricultural and Mechanical College of Texas by Charles Bretschneider (Bretschneider and Reid 1953), w The so-called Gulliver's rule (Johnson 1919, p. 376) cannot be applied here successfully in all cases from chart data and is of doubtful validity in any case. See Bullard (1942) and Price (1952). ^ With reference to the center of the Gulf. longshore drift occurs. A northward drift exists for 20 nautical miles from the headland at Indian Rocks (27G°52' N. Lat.) to Anclote Keys. A much stronger south-southeastward drift exists from Indian Rocks to Cape Romano and its large underwater bars, a distance of 75 nautical miles. Southeastward drift again appears south of Cape Sable, where fine-grained sediments have been carried into the northwestern part of Florida Bay. Colorados barrier reef at the western end of Cuba diverges from the shoreline to the west, suggesting a clockwise drift. ^^ Split ends indicate a clockwise drift (to the west) on the north and northwest coasts of Yucatan to the Laguna de Terminos (Sector 1.11, fig. 14). The unmodified and slightly modified drowned karst and mangrove ridge shorelines do not show appreciable longshore drift, judging by their irregular shorelines and dominantly transverse tidal channels. Convergence areas exist at the cuspate delta of the Apalachicola and the cuspate foreland of Cape Sable, Florida. The cuspate foreland of Cabo Rojo (fig. 12; Sector 3, fig. 14), is asymmetrical, showing that the counterclockwise drift persists across it despite convergence. Bates (1953) shows from photographs and ocean- ographic data that there is a Coriolis effect ^' turning Mississippi River water westward along shore. This coincides in direction with a weak, westward-moving wind-powered drift. Together there is formed a dominant counterclockwise drift (to the right). Distribution of sediments along the delta front agrees well with this drift. Air photographs show that the Coriolis drift oc- curs also at the mouths of the other rivers of the northwestern Gulf coast. It is not operative, however, in equatorial and near-equatorial waters such as the southern Gulf of Mexico. REFERENCES Ball, M. W., and Douglas, Ball. 1953. Oil prospects of Israel. Bull. Am. Assn. Petrol. Geols. 37 (1): 1-113. Barton, D. C. 1930. Deltaic coastal plain of southeastern Texas. Bull. Geol. Soc. Am. 41 (3) : 359-382. " Observations of drift in this direction have been recorded. The drift seems to be powered by a clockwise eddy developing off the right flank of the Yucatin current (N. to NNE. through Yucatan Channel; Leipper p. 121, fig. 34). >* Relative right hand turning of flows because of the rotating coordinates of the revolving earth. The turn is to the left in the southern hemisphere. GULF OF MEXICO 63 Bates, C. C. 1953. Physical and Geological aspects of delta forma- tion. Dissertation for the Pli. D. degree, Dept. of Oceanography, Agric. and Moch. College of Texas, College Station, Texas. (Manuscript) 250 pp. Bretschneider, C. L. and R. O. Reid. 1953. Changes in wave height due to friction, percola- tion, and refraction. Trans. Amer. Geophys. Union. (In press.) Brown, C. W. 1939. Hurricanes and shoreline changes in Rhode Island. Geogr. Rev. 29 (3): 416-430. BULLARD, F. M. 1942. Source of beach and river sands on Gulf coast of Texas. Bull. Geol. Soc. Am. 53 (7): 1021-1043. Carlston, C. W. 1950. Pleistocene history of coastal Alabama. Bull. Geol. Soc. Am. 61 (10): 1119-1129. COFFET, G. N. 1909. Clay dunes. Jour. Geol. 17: 754-755. Cooke, C. W. 1939. Scenery of Florida interpreted by a geologist. Florida State Geol. Surv. Bull. No. 17, 118 pp. 1945. Geology of Florida. Florida State Geol. Surv. Bull. No. 29, 339 pp. Cooper, H. H., Jr., and V. T. Stringfield. 1950. Ground water in Florida. Inf. Circ. No. 3, Florida State Geol. Surv., 7 pp. Daly, R. A. 1934. The changing world of the Ice Age. xxi, 271 pp. Yale Univ. Press, New Haven, Conn. Davis, J. H., Jr. 1940. The ecology and geologic role of mangroves in Florida. Carnegie Inst. Washington Pub. No. 517, Papers Tortugas Lab. 32 (16): 303-412. 1942. The ecology of the vegetation and topography of the sand keys of Florida. Carnegie Inst, of Wash- inton Pub. No. 524, Papers Tortugas Lab. 33: 113- 195. Deussen, Alex. 1924. Geology of the coastal plain of Texas west of Brazos river. U. S. Geol. Surv. Prof. Paper 126, xii, 139 pp. DiETZ, R. S., and H. W. Menard. 1951. Origin of abrupt change in slope at continental shelf margin. Bull. Am. Assn. Petrol. Geols. 35 (9) : 1994-2016. DoERiNG, John. 1935. Post-Fleming surface formations of coastal south- east Texas and south Louisiana. Bull. Am. Assn. Petrol. Geols. 19 (5): 651-688. Emery, K. O. 1952. Continental shelf sediments of southern Cali- fornia. Bull. Geol. Soc. Am. 63 (11): 1105-1108. Evans, O. F. 1942. The origin of spits, bars and related structures. Jour. Geol. 50 (7): 846-865. Fairbridge, R. W. 1948. Problems of eustatism in Australia. Sixieme Rapport de la Commission pour I'^tude des Terrasses Pliocenes et Pleistocenes, Union Geog. Internat., Louvain. pp. 47-51. Fenneman, N. M. 1938. Physiography of eastern United States, xiii, 714 pp. McGraw-Hill Book Co., Now York. FiSK, II. N. 1944. Geological investigation of the alluvial valley of the lower Mississippi river. Mississippi River Comm., U. S. Army, Corps of Engrs. vi, 78 pp., atlas. 1948. Geology of lower Mermentau river basin. Def- inite Project Report, Mermentau River, Louisiana. U. S. Army, Corps of Engrs. (mimeo.), Appendix II, 32 pp. 1952. Geological investigation of the Atchafalaya basin and the problem of Mississippi river diversion. Mississippi River Comm., U. S. Army, Corps of Engrs., Vol. I (text), vi, 145 pp.. Vol. II (atlas), pis. A, 1-36. Fleming, R. H., and F. E. Elliott. 1950. Some physical aspects of the inshore environment of the coastal waters of the United States and Mexico. 12 pp. manuscript. Flint, R. F. 1947. Glacial geology and the Pleistocene epoch, xviii, 589 pp. John Wiley & Sons, Inc., New York; Chap- man and Hall, Ltd. London. Hayes, C. W., and Wm. Kennedy. 1903. Oil fields of the Texas-Louisiana Gulf coastal plain. U. S. Geol. Surv., Bull. 212, 174 pp. Hayes, C. W., T. W. Vaughan, and A. C. Spencer. 1901. Report on a geological reconnaissance of Cuba. 123 pp. (Havana?). Also in Civil Rept. of Brig. Gen. Leonard Wood, Military Governor of Cuba, for 1901, vol. I. Howard, A. D. 1939. Hurricane modification of the offshore bar of Long Island, New York. Geogr. Rev. 29 (3) : 400-415. Huffman, G. G., and W. A. Price. 1949. Clay dune formation near Corpus Christi, Tex. Jour. Sedim. Petrol. 19 (3): 118-127. Johnson, D. W. 1919. Shore processes and shoreline development, xvii, 584 pp. John Wiley & Sons, New York. 1925. The New England-Acadian shore line, xx, 608 pp. John Wiley & Sons, New York. 1938. Offshore bars and eustatic changes of sea level. Jour. Geomorphology 1 :273-274. Keulegan, G. H., and W. C. Krumbein. 1949. Stable configuration of bottom slope in a shallow sea and its bearing on geological processes. Trans. Am. Geophys. Union 30 (6): 855-861. King, L. C. 1942. South African scenery, xxiv, 340 pp. Oliver and Boyd, Ltd., London. Kuenen, Ph. H. 1950. Marine geology, x, 568 pp. John Wiley & Sons, New York. LoHSE, Alan. 1952. Shallow-marine sediments of the Rio Grande delta. Dis.sertation for the Ph.D. degree. Department of Geology, Univ. of Texas, Austin, Texas (manuscript, 113 pp.). 64 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE LUCKE, J. B. 1938. Marine shorelines reviewed. Jour. Geol. 46 (7) : 985-995. McCuRDT, P. G. 1947. Manual of coastal delineation from aerial photo- graphs. U. S. Navy, Hydrographic Office Pub. No. 592, iii, 143 pp. MacNeil, F. S. 1950. Pleistocene shorelines in Florida and Georgia. U. S. Geol. Surv. Prof. Paper 221-F, pp. i-iii, 95-107. Martens, J. H. C. 1931. Beaches of Florida. Florida State Geol. Surv. 21-22nd. Ann. Repts. 1928-30, pp. 67-119. Palmer, R. H. 1945. Outline of the geology of Cuba. Jour. Geol. 53 (1): 1-34. Parker, G. G., and C. W. Cooke. 1944. Late Cenozoic geology of southern Florida with a discussion of the ground water. Florida State Geol. Surv. Bull. No. 27, 119 pp. Phleger, F. B., and F. L. Parker. 1951. Ecology of foraminifera, northwest Gulf of Mexico. Part I, Foraminifera distribution by F. B. Phleger. pp. ix, 1-88. Mem. 46, Geol. Soc. Am. Price, W. A. 1933. R61e of diastrophism in topography of Corpus Christi area, south Texas. Bull. Am. Assn. Petrol. Geols. 17(8): 907-962; revised in Gulf coast oil fields. Am. Assn. Petrol. Geols., 1936, pp. 205-250. 1939. Offshore bars and eustatic changes of sea level, a reply. Jour. Geomorphology 2(4): 357-365. 1947. Equilibrium of form and forces in tidal basins of coast of Texas and Louisiana. Bull. Am. Assn. Petrol. Geols. 31(9): 1619-1663. Corrections 31(10): 1893. 1949. Pocket gophers as architects of mima (pimple) mounds of the western United States. Texas Jour. Sci. 1(1): 1-17. 1951a. Barrier island, not "offshore bar". Science 113(2937): 487-488. 1951b. Building of Gulf of Mexico: Secondary events in a regionally concordant basin. First Annual Meeting, Gulf Coast Assn. Geological Societies, New Orleans, Nov. 1951. pp. 7-39. 1952. Reduction of maintenance by proper orientation of ship channels through tidal inlets. Proc. Second Conf. on Coastal Engineering, Houston, Tex., Nov. 1951: 243-255. Edited by J. W. Johnson, Council on Wave Research, The Engineering Foundation, New York City. Russell, R. J. 1936. Physiography of lower Mississippi River Delta. Louisiana Dept. Conserv., Geol. Bull. No. 8: 3-199. 1940. Quarternary history of Louisiana. Bull. Geol. Soc. Am. 51(8): 1199-1233. Sapper, K. T. 1937. Mittelamerika. Handbiich der regionalen Geol- ogic. Steinmann and Wilckens, eds. Band 8, Abt. 4, Heft 29. 160 pp. Carl Winter, Heidelberg. Shepard, F. p. 1937a. Revised classification of marine shorelines. Jour. Geol. 45(6): 602-624. 1937b. "Salt" domes related to Mississippi submarine trough. Bull. Geol. Soc. Am., 48(9): 1349-1361. 1948. Submarine geology, xvi, 348 pp. Harper & Bros., New York. 1952. Revised nomenclature for depositional coastal features. Bull. Am. Assn. Petrol. Geols. 36(10): 1902-12. Steers, J. A. 1946. The coastline of England and Wales, xix, 644 pp. Univ. Press, Cambridge, England. 1952. The coastline of Scotland. Geogr. Jour. 118, pt. 2: 180-190. Stearns, H. T. 1941. Shore benches on North Pacific islands. Bull. Geol. Soc. Am. 52(6): 773-780. 1945. Eustatic shore lines in the Pacific. Bull. Geol. Soc. Am. 56(11): 1071-1078. SuEss, Eduard. 1888. Das Antlitz der Erde. Vol. 2, iv, 704 pp. Tempsky & Freytag, Leipzig. Tamato, J. L. 1949. Geografia general de Mexico (Geografia Fisica). Vol. I, viii, 628 pp. Vol. II, 583 pp. Publ. by Author (printer Talleres Graficos de la Nacion) ; Atlas, 24 maps. Trask, p. D. 1937. Relation of salinity to the calcium carbonate con- tent of marine sediments. U. S. Geol. Surv., Prof. Paper No. 186-(N): 273-299. 1939. Additional note (to) Florida and Bahama marine calcareous deposits, by E. M. Thorp, pp. 292-293, Recent Marine Sediments, Am. Assn. Petrol. Geols., 736 pp. Umbgrove, J. H. F. 1947. The pulse of the earth. Martinius NijhoflF, The Hague, 2d ed, xx, 358 pp. U. S. Army, Corps of Engineers. 1940. Report on survey of intracoastal waterway, Caloosahatchee River to Apalachicola Bay, Florida (Anclote River to St. Marks) and Barge Canal across Florida. U. S. Engr. Off., Jacksonville, Fla., Nov. 1940. U. S. Weather Bureaxj. 1938. Atlas of climatic charts of the oceans. Supp. Pub, No. 1247. Vaughan, T. W. 1909. The geologic work of mangroves in southern Florida. Smithsonian Misc. Coll, 52(5): 461-464. 1914. The building of the Marquesas and Tortugas atolls and a sketch of the geologic history of the Florida reef tract. Carnegie Inst. Washington, Pub. No. 182, Papers Tortugas Lab. 5: 55-67. GULF OF MEXICO 65 Vaughan, T. W., and Others. Weaver, P. 1937. International aspects of oceanography, oceano- 1950. Variations in history of continental shelves. graphic data and provisions for oceanographic re- Bull. Am. Assn. Petrol. Geols. 34(3): 351-360. search. Nat. Acad. Sci., Washington, xvii, 255 pp. Wetzel, Rene, and Jean Haller. Vernon, R. O. 1945. Le Quaternarie de la rdgion de Tripoli (Liban). 1951. Geology of Citrus and Levy counties, Florida. Delegation G6n6rale de France au Levant, Section Florida State Geol. Surv. Bull. No. 33. xii, 256 pp. Geologique. Notes et Memoirs. 4:1-48. Beyrouth. GEOLOGY OF THE GULF OF MEXICO By S. A. Lynch,^ Agricultural and Mechanical College of Texas The lower Gulf coast and the inner continental shelf of the Gulf of Mexico are the sites of oil fields in Veracruz, Tamaulipas, Texas, Louisiana, and Florida. Therefore, hundreds of geologists, geophysicists, and engineers are engaged in inves- tigations of the structure, geologic history, and sedimentology of the fringe of the Gulf of Mexico. Due to the economic necessity for research to discover new trends and new provinces of petro- leum accumulation and to the many data contin- uously being furnished by the drill and geophysics, great strides have been made in the knowledge of the continental shelf and the adjacent Coastal Plain of the United States. Even though these economic studies were of the coastal area and con- tinental shelf, they have encouraged thought con- cerning the origin and geologic history of the Gulf of Mexico. A modern study of the Gulf Stream was initi- ated by the United States Coast Survey in 1846, and some work in the Gulf of Mexico was started soon thereafter. During the last century, many capable students of geology have studied the geo- logical history of the Gulf of Mexico, but there is still much diversity of opinion concerning its origin and manner of development. EARLY CONCEPTS Early European writers initiated the idea of North and South America being tied together by a continuous mountain sj'stem, and this century- old concept is still popular in Europe. Suess (1885, pp. 283-285) described the Gulf of Mexico bottom as an elevated "plate" and considered this plate the foreland of the Antillean chain. He believed the present deep Gulf did not exist in Paleozoic time, but an old metamorphosed and deformed basement formed a somewhat flat platform that continued southward the low-lying ' Contribution from the Department of Geology of the Agricultural and Mechanical College of Texas, Oceanographic Series No. 18. ' Head, Department of Geology, Agricultural and Mechanical College of Texas, College Station, Texas. 259534 O— 54 6 central area of the United States. The present Gulf of Mexico was formed by the collapse of the plate during Cretaceous and later time, and the general outline of the Gulf was "not influenced by the course of the mountainfolds unless perhaps in the west by the approach of the Mexican ranges to the coast of Vera Cruz" (1885, p. 551). The plate of Suess has influenced geologic thought con- cerning the origin of the Gulf for the past three- score years. Spencer (1895, pp. 103-140) not only believed that the whole tract of the Caribbean Sea, the Antilles, and the Gulf of Mexico constituted an ancient continental region, but he attempted to restore the topography of the submerged conti- nent. Using available soundings, Spencer found drowned valleys which he considered of prime importance in establishing the existence of a continental region which ever since the Miocene had executed vertical fluctuations of an amplitude of many thousands of meters. In discussing the area, he stated, "the Gulf of Mexico appears to have been a plain, with the fjords and embayments reaching nearly to its greatest depths" (1895, p. 119). Thus, Spencer agreed with Suess, at least in part, and postulated a Gulf floor more than 12,000 feet above its present deepest position. Hill (1898, pp. 3-5) believed the Gulf of Mexico is more closely related to North America than to Central or South America. He declined to con- sider most of the Antilles as other than true oceanic formations and refused to believe that there is any connection between the northern Antilles and Barbados-Trinidad, the latter being by him assigned to the South American mainland. He saw that the Gulf is nearly surrounded by low plains composed of nearly horizontal, uncon- solidated sediments deposited in an enlarged Gulf of Mexico. This border of plains is in direct contrast to the Caribbean and its mountainous periphery. Willis (1929, p. 328) held that basins are per- manent, and he did not believe the Gulf of Mexico 67 68 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE was ever an area of shallow seas over a flat "plate." This is shown by his statement that The isostatic equilibrium of the Gulf is inconsistent with the conditions that should result if a continental mass had sunk ... I, myself, regard the Gulf as representing a mass of basalt which was erupted in Pre-Canibrian time, either before or soon after the eruptions of the granitic nuclei of North America. If so, it has been a basin ever since . . . The Caribbean, Yucatan Deep, and the Gulf of Mexico are, from the point of view of actual isostatic equilibrium, all of the same nature. They are, I think, all of them basins of great antiquity. Van der Gracht (1931, p. 121) discussed the origin of the Gulf of Mexico and the downbreaking of Llanoria. He believed the coastal plain "represents a sunken basin over old central chains" and that both the Caribbean Sea and the Gulf of Mexico were part of a great geosyncline and a "very complicated system of anticlinoria, ridges and chains . . . must now fill the original geosyn- cline, generated by its late-Paleozoic compression stage. Since then, complete abrasion and renewed sedimentation . . . have obscured the original structure." Fifty years after Suess, Schuchert (1935, p. 340) confirmed the conclusion of Suess as to the Gulf of Mexico "plate" and described it as extending from Tabasco northward so as to include part of Texas, Ai-kansas, the southern tip of Illinois, Alabama, the peninsula of Florida, and the northern Bahama Banks, as well as other Mis- sissippi embayment States. The Gulf of Mexico and the Caribbean were separated, according to Schuchert, by a Central American-Antillean anticlinorium until Jurassic time. By mid-Cretaceous, the Gulf of Mexico area responded to crustal movements in Mexico and the Antillean geanticline and began to sub- side; this downward movement continued until great depths were reached. Thus, the Gulf of Mexico was a shallow sea probably from Pro- terozoic to mid-Mesozoic time, and by late Cenozoic time the depth had changed from possibly less than 1,000 to over 12,000 feet. Schuchert believed the cause of the inbreaking of the "plate" and the subsequent subsidence was related to "the geologic structures of the Central American-Antillean region, those of northern South America, and those of the present Caribbean sea bottom" and that all were "due to subcrustal flowage, to the rising of plutonic masses into the various arches, and to the subsequent cooling of these masses." He also believed that — The present depth of 12,000 feet was surely exceeded during Cenozoic time, since in the course of this era sedi- ments thought to be many thousands of feet thick ac- cumulated upon it ... In the latitude of South Lou- isiana, the ancient Gulf bottom has subsided over 25,000 feet, about twice the depth of the present Mexican Basin (Sigsbee Deep). Therefore we may say that the greater part of the Gulf of Mexico has sunk since Middle Cretaceous time at least 20,000 feet. These are striking facts, in- dicating slow, but in the end enormous, loading and isostatic adjustment, accompanied by subcrustal move- ments and rock fiowage toward the rising geanticlines of Mexico and the Central American-Antillean arch, a move- ment that is not yet completed. GULF COAST GEOSYNCLINE Barton, Ritz, and Hickey (1933, pp. 1446- 1458) were among the first to publish concerning the Gulf coast geosyncline, and they presented both stratigraphic and geophysical evidence for the existence of a geosyncline in the Gulf coast of Texas and Louisiana. They showed geophysical calculations to indicate a horizontal increase in density of the basement rocks from the Sabine uplift to near the middle of the Gulf of Mexico, and they concluded that a geosyncline must occur in the basement surface with its trough axes slightly landward from the present coast line (op. cit., p. 1456). They also showed the great thickening of the Upper Cretaceous and Tertiary beds as they dip Gulf ward, with the Tertiary beds reaching a stratigraphic thickness of more than 25,000 feet near the coast. Knowing that the deepest part of the Gulf of Mexico is 12,500 feet and assuming that the thickness of the Upper Cretaceous-Tertiary sedimentary deposits in the great depths of the Gulf are 10 percent or less of their thickness in the Gidf coast, it was concluded that "the basement of the Upper Cretaceous- Tertiary beds must be down-warped 6,000 to 16,000 feet in reference to the depth of that basement under the Sigsbee Deep." The geosynclinal trough is a well-marked feature indicating considerable subsidence. Its westward limit is not definitely known, but some thinning of formations is noted in the longitude of Mata- gorda County, Texas. It is further complicated by transverse structures such as the Rio Grande syncline, the San Marcos arch, the Houston syncline, the Sabine uplift, and the Mississippi River syncline. GULF OF MEXICO 69 Howe (1936, p. 82) called attention to the great sinking in the rou;ion of the Mississippi Delta which he believed amounted to about 30,000 feet since the beginning of the Tertiary. He believed the Gulf coast is an active geosyncline resulting from the weight of the sediments brought down by the Mississippi River. Evidence of the sinking of the Mississippi Delta was also presented by Russell (1936, pp. 167-169) in his study of the physiography of the region. Russell and Fisk (1942, pp. 56-59) questioned the "strength" of the earth's crust and concluded that the crust appeared "weak" as it jnelded and subsided "at essentially the same rate that the deposits thickened." Meyer (1939, p. 206) did not subscribe to the sedimentary -load theory and among various ob- jections stated that the "epochs of reversal of movement in the geosyncline, indicated by un- conformities, shoreline migrations, entrenched streams, submarine canyons, and the elevated beach at Corpus Christi, are opposed to the basic tenets of the sedimentary-load theory." Meyer also used the argument that the ocean deeps, which are structural troughs, could not have been caused by the weight of accumulating sedi- ments. He suggested that the Mexican Basin and the Gulf coast geosyncline may be related structures and that the Gulf coast geosyncline was a "similar structural and topographic basin in early Tertiary time when the strand-line was far inland. After this basin had come into existence, it offered an opportunity for the accumulation of thousands of feet of sediments. The weight of the first several thousand feet of Tertiary deposits may have been sufficient to overcome the in- herent strength of the crust and to cause further sinking" (op. cit., p. 206). Storm (1945, p. 1330) considered the Gulf coast geosynclinal trough as a well-marked feature indicating considerable subsidence. He believed that, if subsidence continued at a fixed position and if sediment filled this trough and passed over it, there should be some sign of sinking inland and drainage should have caused deposition over the axis of the syncline. Such indications were lack- ing, and he therefore believed that the shape of the trough was a composite of past and present. He showed that sediments are accumulating prin- cipally on the seaward flank of the trough which pushes the bottom of the flank downward while the landward flank rises slightly. Thus, the trough tends to move seaward with continued sedimentation. Glaessner and Teichert (1947, p. 586) thoroughly reviewed the subject of gcosynclines and con- cluded that the origin of gcosynclines is still unknown. Observed facts are too often over- shadowed by an author's "attitude to one or the other of the current and mutually exclusive hypotheses of mountain building and of the origin of continents on which no finality has yet been reached. Concerning the actual mechanism of the formation of gcosynclines it would seem that the school of Gulf coast geologists has produced such weighty arguments in favor of subsidence under load that the operation of the factor can no longer be doubted. On the other hand, there is evidence for 'autonomous' uplift and subsidence of parts of the crust which would make it possible for sedimentary accumulations to be formed as a result of active subsidence and uplift rather than of passive depression under the load of shifting products of erosion." Bornhauser (1947, pp. 706-711) observed that, since the Tertiary transgressions affected the whole northern border of the Gulf of Mexico, diastrophic movements must have been the primary cause of the transgressions. He agreed that the subsidence of the Mississippi embayment and the Gulf coast geosyncline caused the Ter- tiary transgressions of those areas, and the sub- sidence was due to diastrophic movements. Bornhauser "has not found clear evidence to support the idea that the weight of the sedi- mentary column is the deciding factor for subsi- dence. On the contrary, all facts and evidences seem to point toward the conclusion that the formation of the Mississippi embayment is a tectonic incident closely related to the structural history of the Gulf of Mexico which underwent considerable epeirogenic movements during the Tertiary." The idea of a Gulf of Mexico neutral plate was introduced by Suess and substantiated by Schu- chert who considered it to be the foreland of the Antdles. Bornhauser accepted this neutral plate and suggested that the northern border of the plate may have formed the submarine plateau of southeast Mississippi, at least during earlier Ter- tiary. Deeper synclines separated this plateau 70 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE from the land masses on the northwest and north, particularly during Midway-Wilcox time. Bornhauser (op. cit., p. 709) stated: In order to explain the progressive enlargement of the southeast Mississippi plateau and the corresponding shifting toward the north and northwest of its frontal synclinal zones during the Eocene, the theory is advanced that this plateau, together with the Gulf of Mexico "plate," drifted in successive stages to the north as a result of Tertiary orogenic movements in the Antilles. A maximum penetration of the' plateau into the Missis- sippi embayment was reached at the close of the Eocene and early Oligocene periods, when it touched the northern land masses. A breakdown of the southern part of this plateau and a large part of the Gulf of Mexico followed during the Oligocene and Miocene, forming the present Gulf of Mexico. This downbreaking in connection with the emergence of the embayment probably caused a change in direction of the Gulf Coast geosyncline in south Loui- siana. During the Eocene, the axis of this syncline followed a southwest-northeast trend, with the Missis- sippi embayment syncline forming its northeastern extension. With the formation of the present Gulf of Mexico during Oligocene and Miocene time, this axis was diverted to a west-east trend. Trask, Phlcger, and Stetson (1947, pp. 460-461) obtained sediments from the northwestern part of the Gulf of Mexico during the 1946 expedition of the Atlantis. In the central part of the Gulf, where the depth of water exceeds 11,000 feet, two distinctly different layers of sediment were found. A thin top zone of globigerina was underlain, in most cores, abruptly, by alternating clay and very fine, well-sorted silt containing a cold water fauna. In other cores, from the same depth, ripple marks and crossbedding were found. Such conditions suggest shallow-water deposition; and, to get such conditions, it is necessary to assume either a rather recent great depressing of the Gulf floor or an equally great lowering of sea level. The other alternate is to assume sufficient currents at depth to cause sorting, ripple marks, and crossbedding. Lowman (1949, pp. 1986-1993) believed that the central part of the Gulf of Mexico might have been epicontinental in character during Eocene time. The evidence cited includes the wide extent of the Eocene into the transverse embayments, the gentle depositional slopes, the dominance of con- tinental shelf faunas, and the character of the sediments of the southeast Mississippi platform. In contrast to the Eocene, the Upper Tertiary is absent from the transverse embayments and has continental-slope facies on relatively steep deposi- tional slopes. Therefore, the Upper Tertiary sup- ports a deep hole in the central part of the Gulf of Mexico, as it is today, though not necessarily in the same location. Lowman did not believe the stratigraphic evi- dence was conclusive that the Mississippi River syncline subsided in response to load. He believed some workers have used facies criteria instead of planes of stratification in the isopach maps which find "maxima under the delta in the Quaternary and the Pliocene-Miocene" (op. cit., p. 1991). Weaver (1950, p. 359) studied the continental shelves of the Gulf of Mexico and decided that a significant tectonic zone is at the outer edge of the continental shelf. He concluded that the topo- graphic contours on the continental slope are really structural contours and that they exist in sufficient number to indicate active tectonic regional features. He proposed "the theory that the Gulf of Mexico as a deep sea is young, and that its present central great depth is due to downfaulting." The most intense faulting is indicated along the outer margin of the continental shelf west of Florida and near Yucatan, but even the more gentle continental slopes are considered fault zones. No definite time of faulting was given by Weaver. Moody (1950) favored a single salt mass as the source of the Gulf coast and Mexican domes and suggested that it may extend across the Gulf of Mexico into the Isthmus of Tehuantepec. If this is true, the Gulf of Mexico was shallow enough to allow salt deposition beyond the present continent during the time of the deposition of the Eagle Mills salt, which is Jurassic in the opinion of Moody, although some writers place it in the Triassic or Permian. He believed the Gulf of Mexico had some downwarping during Upper Cretaceous ; that it began to take shape at the end of the Laramide Revolution; and that it subsided, and maybe formed the Mexican Basin, in post-Reynosa (Pliocene) diastrophic movements. The finding of Reynosa gravels in Florida at an elevation of 360 feet suggests a great change in sea level to allow these gravels to be transported there. This means a great post-Reynosa diastrophic movement during which the west Florida shelf scarp and possibly the Mexican Basin came into existence. Eardley (1951b, p. 2236) stated that "the Gulf of Mexico came into existence after the Appa- lachian orogeny by subsidence. ' ' Much of the Gulf is surrounded by the belt of late Paleozoic orogenj^. GULF OF MEXICO 71 and sediments dating back to at least the Permian are found in its niar<;inal areas. Eardley believed that the margins of the Gulf have had a near balance between subsidence and deposition, while subsidence has exceeded deposition in the central Mexican Basin. King (1951, p. 175) stated his i)elief that the origin of the Gulf coast geosyncline was uncertain, but he believed "that the geosyncline represents an independent tectonic feature and perhaps a new mobile belt in its early stage of development." The theory of Weaver that fault scarps bound the present central great deep of the Gulf received additional support by Jordan (1951, p. 1991) who described the escarpment off the panliandle of Florida. This escarpment occurs in 700 to 900 fathoms of water, and the sea floor is offset 6,000 feet or more in some places. Comments on Jor- dan's paper by Stetson (1951, p. 1993) confirmed the findings of Jordan and noted that the escarp- ment maintains about the same height and slope southward along the west Florida shelf. Stetson further commented that "from the overall picture of the whole area, one gets the impression that the bottom of the Gulf has foundered and that at least this continental slope is due to a normal fault" (idem.). To date little exploration in the Gulf of Mexico has had as its objective the determination of major tectonic features. The cost of marine geo- physical surveying and the drilling of offshore wells are such that the tectonics of the Gulf must be approached indirectly by using soundings and bottom samples together with observations of the shore features. GEOMORPHOLOGY OF GULF OF MEXICO The topography of the Gulf of Mexico is too scantily mapped to show the degree of develop- ment of the different types of topography so far known there. As early as 1878 Agassiz (1878-79, p. 1) noted two of the striking topographic features of the Gulf, the great limestone banks: one west of Florida and the other northward from the penin- sula of Yucatdn. In both cases the 100-fathom line is somewhat parallel to the shore and forms the inner edge of the steep slopes descending to the Mexican Basin, which is another major fea- ture of the Gulf. The varying development of continental shelves and the irregular continental slope with its escarpments, basins, knobs, and trougiis are also striking features of the Gulf of Mexico. GENERAL CHARACTERISTICS The continental shelf forms an almost con- tinuous terrace around the margin of the Gulf of Mexico. The major breaks occur in the Straits of Florida and the Yucatdn Channel which form outlets from the Gulf to the Atlantic Ocean and Caribbean Sea, respectively. The shelf is not an expressionless plain lacking in interesting physiographic features as may be suggested by some maps with a contour interval too great to properly present the smaller features. This terrace or shelf has numerous depressions, troughs, ridges, minor knobs, coral heads, escarp- ments, and two known submarine canyons. The widest parts of the continental shelf in the Gulf of Mexico lie off Texas and the peninsulas of Yucatan and Florida. The shelf width varies from 8 to 117 miles in the northern Gulf, the maximum width being off western Florida. Other shelf widths include: 40 miles off the southern tip of Florida, 52 miles off the Isles of Dernieres, Louisiana, 110 miles off the Sabine River mouth, 40 miles off the Rio Grande outlet, and 135 miles off western and northern Yucatdn. The continental slope differs from place to place not only in width and steepness but also in physiographic features associated with it. The continental slope, in general, constitutes one of the great relief features of the earth. The edge of the continental shelf is only very roughly paral- lel to the shore line as is shown by the varying width of the shelf. The continental slope varies greatly in width with a minimum width west of Florida and west and northwest of the Yucatan Peninsula. ORIGIN OF MAJOR FEATURES The continental shelves of the Gulf of Mexico seem to have a close geologic and physiographic relationship with the adjacent land. Broad shelves lie in front of broad coastal plains, and narrow shelves lie between steep continental slopes and rugged near-shore terrain. There is no simple explanation of the origin of the shelves and slopes, or of some of the features of these provinces, that has gained wide accept- ance. 72 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE In discussing continental shelves, Pratt (1947, p. 661) observed that "modern investigations have also confirmed Nansen's pioneer observation that the inland portion of the continental shelf is a surface of degradation." Umbgrove (1946, p. 249) stated, "it appears that the history of the shelf was rather complicated. Sedimentation, abrasion, and denudation played their role. The area was subjected to changes of sea-level and movements of the bottom. Wind-waves and tidal currents acted upon the sediments of the shelf. The influence of each of these and still more factors in the building of the submerged part of the continental margin is still an open question." He also believed that the landward part of the shelf may have resulted from plana- tion when the sea was some 300 feet lower than at present. Many workers believed that the topography of the shelves resulted from subaerial erosion. Dana (1863, p. 441) stated this was accomplished by the elevating of the land. Long coast lines would have to be uniformly elevated to such heights that most geologists agree the hypothesis has too many difficulties to be acceptable. The lowering of sea level could also produce conditions for subaerial erosion. Shepard and Emery (1941, p. 154) found that the formation of Pleistocene ice could account for lowering sea level 2,200 feet; Veatch and Smith (1939, p. 41) believed sea level was lowered 12,000 feet and restored in the last 25,000 years; Fisk (1944, p. 68) found evidence for a drop of sea level of 400 to 450 feet; and Carsey (1950, p. 375) suggested that if sea level was lowered 420 to 480 feet "the origin of the shelves could be attributed' largely to wave planation." The irregularities of the bottom of the shelves and the great valley-like notches along the out- ward slopes of the shelves are also unsolved prob- lems. Umbgrove (1946, p. 249) believed "the phenomena of the continental margin are corre- lated with other periodic events occurring in the earth's crust and its substratum." Daly (1936, p. 401) introduced the idea of density currents or "bottom streams of sea water containing mud in suspension and therefore tem- porarily endowed with density greater than that normal to the clean water overlying the respective continental terraces. It is further supposed that the conditions for the formation of such bottom currents were specially developed at certain stages of the Glacial Period ..." This heavy mass of mud and water would naturally move into the depressions on the continental shelf, and in places it would flow over the margin of the shelf and down the continental slope with accelerated mo- tion and force. A new hypothesis for the origin of continental slopes and submarine canyons has been suggested by Emery (1950, pp. 102-104). He proposed that "thrusting along a shear plane at the con- tinental margins may result in a temporary up- bulging of the margins above sea level. During the time of exposure erosion by streams should have incised canyons which now, after isostatic readjustment of the margins, constitute the widely distributed submarine canyons. Known down- warped peneplains below the surface of con- tinental shelves may have been developed on the bulged margins by long-continued erosion. The margins may, thus, have served as sources of some sediments now found on land and believed to have been derived from a seaward direction." Kuenen (1950, p. 497) adhered to the beUef that "the action of turbidity currents, especially during the ice ages" cut the submarine canyons along the edge of the shelf and slope of the continents. An examination of the maps of the topography of the outer shelf and slope of the northern Gulf of Mexico shows many features which suggest an origin due to density currents and the deposition of the mass of mud. Also, continental shelf fauna dredged from the Mexican Basin may have been transported from the shelf by turbidity currents. Furthermore, these currents may have carried sediment to the central Gulf and, therefore, aided in developing the rather flat floor of the Mexican Basin. GEOMORPHOLOGY BY AREAS Soundings in only a few areas of the Gulf are adequate to permit the drawing of accurate maps of the surface of the continental slope. More information is available concerning the northern Gulf; therefore, this area is discussed in some detail starting with the Straits of Florida and progressing in a counterclockwise direction. GULF OF MEXICO 73 EASTERN GULF AREA The Florida Plateau includes not only the State of Florida but an equally great or greater area that lies submerged beneath water less than 50 fathoms deep and forms the Florida shelf (H. Gunter, 1929, p. 41). This plateau has been in existence since ancient time and is a part of the Gulf of Mexico "plate" of Suess and Schuchert. Its history includes submergence during Upper Cretaceous, part of Oligocene, and Upper Miocene. Since Miocene time uplift has continued, and erosion has removed much of the once continuous cover of Miocene sandy limestone. The Florida Peninsula now has very little relief. It has a wide continental shelf off its west coast, thus demonstrating the physiographic similarity be- tween the coastal plain and the adjacent con- tinental shelf. The 1947 expedition of the United States Coast and Geodetic Survey ship Hydrographer in the waters on the continental slope southwest of the Apalachicola River, Florida, has been reported, in part, by Jordan (1951, pp. 1978-1993). Many new and interesting data have been secured in the 25,000-square-mile area of this report. The greater part of the continental shelf west of the peninsula of Florida is covered by about 40 fathoms of water, and the slope out to the 100-fathom contour is for the most part gradual. The westward slope varies from 1° at the north to 5° at the south end of the shelf. In the 25- to 80-fathom depths, domes, ridges, and troughs were discovered; escarpments and knobs with a relief of more than 300 feet were found in the 70- to 90-fathom depths. Most of these features occur along the shelf margin. Within the 400- to 1,760-fathom zone the con- tinental slope contains a deep escarpment, faults, and the terminus of the De Soto Canyon, as well as domes and depressed areas. The continental slope escarpment is of special interest since it may materially aid in the ultimate solution of the origin of the Gulf of Mexico. Jordan (op. cit., p. 1991) noted a 35° gi-adient on a 4,000-foot drop, contrasting with 1° gradients or less above and below the escarpment. A ridge 30 miles long parallels the escarpment at 700 to 800 fathoms, and ridges and troughs with relief up to 600 feet occur along the bottom of the escarpment. The main escarpment undoubtedly represents faulting, and some of the minor troughs and ridges may have a like origin. There can be little doubt that the Florida Plateau has been faulted along its western edge, but the faulting is difficult to date. Schuchert believed this faulting was due to the inbreaking of the Gulf of Mexico "plate" and that it probably began in the Upper Cretaceous. However, Weaver (1950, p. 359) beheved "that the Gulf of Mexico as a deep sea is young" and therefore the faulting must have occurred at a much more recent date. MISSISSIPPI DELTA AREA The Mississippi River brings to its mouth a daily load of sediment in the order of 2 million tons. This material has permitted the Mississippi to build its delta out on the continental shelf with the overlapping delta reaching within some 10 miles of the landward edge of the continental slope. It might be expected that a deep trough would exist in the outer edge of the continental shelf in front of the Mississippi River, but such is not the case. An ancient, deeply buried channel is found about 30 miles southwest of the passes of the Mississippi River. Shepard (1948, p. 213) stated that this trough, which has a depth of 1,800 feet, is the only major indentation in the shelf margin in the Gulf of Mexico and that the trough-head penetrates the shelf for nearly 30 miles. The sides are steep, and the flat floor is filled with loosely consolidated sediments. The canyon has been traced out on the continental slope to a depth of 900 fathoms before it becomes merged in the irregularities of the slope. A second trough, called De Soto Canyon, has been discovered off the Apalachicola River of southwestern Florida. Shepard (1948, p. 179, fig. 65) reproduced a map of this trough or canyon as contoured by H. W. Murray of the United States Coast and Geodetic Survey. This map shows a series of depressions, some with relief exceeding 20 fathoms, along the bottom of the trough and a few depressions along the sides of the trough. This canyon is shown in Jordan's map (1951, p. 1982, fig. 2) of the continental slope. The canyon has a relief of about 600 feet, heads near the 240-fathom contour, and terminates near the 500-fathom contour. Stetson (1951, p. 1993) stated that cores of the steepest walls of the canyon showed sediment and no bed rock. 74 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Upwellings of clay, locally known as mud- lumps, occur near the mouths of the Mississippi River passes and have never been reported from any other delta. These mudlumps have been the subject of written discussion for more than a century, but only a few writers have attempted a scientific explanation of them. The most recent study has been made by Morgan (1951) in conjunction with the Corps of Engineers at New Orleans. Mudlumps and mudlump islands have at- tracted much attention since they may have mud cliiFs with a relief of up to 10 feet in an area where the average relief is usually 2 feet or less. Most mudlumps have central cores of fine- grained plastic clay surrounded and sometimes capped by irregularly stratified layers of clay and silt. The upwelling of the clay core usually produces fissures and faults with vertical dis- placements resulting in central grabens. The stratified layers dip away from the islands, often forming doubly plunging anticlinal structures. Local cones along the faults and fissures are formed by the discharge of mud, gas, and salt water. Morgan (ibid.) believed that the "formation of new lumps and rejuvenation of old lumps occurs as a direct result of excessive sedimentation at the river mouths" and "the deforming force which caused mudlump uplift is the static pressure of the sedimentary mass continually being dumped beyond the mouths of the passes." NORTHERN GULF OF MEXICO The continental shelf off Louisiana and Texas is somewhat uniform and has a gentle slope to about the 50-fathom contour. From this point the slope increases to the 70-fathom line where it has an increase in gradient to the 100-fathom depth. Some increase in slope is noted beyond the 100-fathom line, but the bottom becomes so irregular that the true slope becomes obscure. Probably the chief characteristic of the con- tinental slope of the northern Gulf is the hum- mocky topography. Shepard (1937, p. 1350) found 26 topographic features off the coast of Louisiana some of which had a relief of several hundred feet. Charts revealed that the belt of domes can be traced definitely for 180 miles west and southwest of the Mississippi submarine trough. More recent data show that some of the depressions are 2,000 feet deep, and some of the hills have a relief of at least 2,500 feet. Carsey (1950, p. 376) found 164 topographic features along the shelf off the coast of Louisiana and Texas. An area of apparent concentration of these features is shown in figure 16. However, it is probable that there are many somewhat similar features elsewhere on the continental shelf and slope. They seem to be most prevalent in the area between the 100- and 750-fathom con- tours. It is particularly interesting to note that no stream patterns have been found other than the troughs on the margins of the slope off the Mis- sissippi Delta and the Apalachicola River (Shepard 1948, p. 178). Price (1951, p. 32) observed that the "rugged topography of the northwestern shelf-margia or slope seems to contain dislocated segmeats of submarine canyons" which differ in late history from the canyons along the less rugged slope to the east. This suggests that the front edge of the shelf was faulted down in slices as it was built out into the Gulf. Available maps of the topography of the Gulf bottom vary widely in their representation of the physiographic features. The amount of time as well as the number of soundings available influence the choice of the contour interval. Thus, the Treadwell (1949) map of the continental slope of the northwestern Gulf of Mexico, contour interval of 50 fathoms, shows a great number of closed basins and knobs between 91° and 95° W. Long, and 27° to 28° N. Lat. Also, there are suggestions of drainage patterns that are not evident in the map by Shepard (1948, p. 178, fig. 64) with a con- tour interval of 100 fathoms. Some of these differences may be due to the contour interval, but some may also be the result of additional data and the choice of the cartographer when more than one interpretation of the data exists. All available maps of the continental slope of this region show the same general characteristics of the Gulf bottom: a very irregular, hummocky, knob and basin topography. Minor near-shore features of ridge and trough were noted by Kindle (1936, pp. 866-867) along the Louisiana coast. He waded across a 1,500- foot traverse and found ridges whose crests were 10 feet wide and separated by troughs from 60 to 90 feet wide. The same traverse was repeated GULF OF MEXICO 75 2 days later, and while the ridges were free of mud, the depressions were filled with several inches of mud. Therefore, the whole character of the local bottom was changed in 48 hours. This shows the futility of making sweeping conclusions from only a few data, especially in the shore zone. MEXICO Too few data are available on the topography adjacent to Mexico to make a detailed study of either the continental shelf or slope of this region. However, some generalizations may be made from the scanty sounding data and geological maps of the adjacent land. Mountain ranges, trending northeast-southwest, have been mapped 90 and 110 miles east of the mouth of the Rio Grande. The range nearer the coast has a known relief of 2,750 feet with a summit reached at a depth of 540 fathoms and the other range has a known relief of 3,810 feet with a summit at a depth of 839 fathoms. Due east of Tampico a mountain i-ange, with a bearing of N. 65°-70° E., extends some 40 miles and has a relief of 5,800 feet with a summit rising to within 33 feet of the surface. Along the extreme western edge of the Gulf of Mexico, south of Tampico, the continental shelf is narrow, and the adjacent coastal plain is also narrow, being locally practically absent. Tertiary and later igneous rocks occur in the Misantla- Japala area, northwest of Veracruz, and in the Alvarado-El Paso area, south of Veracruz. Some of the highest peaks of Mexico occur just northwest of Veracruz. Lava flows cover much of the near-shore land area and locally form 1,000-foot cliffs at or very near the shore. South of Vera- cruz other smaller cones are very near the coast. While local narrow beaches are formed and break the surface continuity of igneous rocks, undoubt- edly the offshore irregular topography is due to underwater outcropping of these igneous rocks. Practically all of the Yucatan Peninsula forms a broad coastal plain. This peninsula tilts north- westward and passes under the Gulf to form a continental shelf averaging over 125 miles in width. The shelf terminates abruptly to the west and north, and the topographic contours along its edge are undoubtedly also structural contours and represent faulting. MEXICAN BASIN There is within the Gulf of Mexico, but not centrally situated, a large triangular area with deeps exceeding 2,000 fathoms. It lies north- west of the Campeche Banks approximately between 22° and 25° N. Lat. and 89° and 95° W. Long. Regarding this area, Hilgard is quoted by Agassiz (1888, p. 101) as follows: "The large sub- marine plateau below the depth of 12,000 feet has received the name of the 'Sigsbee Deep', in honour of its discoverer." Since the "depth of the basin does not attain 3,000 fathoms, it is not a 'deep' in the Murray sense, but it is an enclosed, distinctive basin, for which Sigsbee's name may appropriately be retained" (Vaughan 1940, p. 66). More recently, however, the name "Sigsbee Deep" has been restricted to the deepest measure- ment in the basin, and the name "Mexican Basin" is used here for the broad, enclosed basin. The bottom of the Mexican Basin is very flat, especially when contrasted with the continental slope of the Gulf. The depths range from 2,000 to 2,070 fathoms over the deepest part of the basin. The bottom rises rather uniformly to the shore in the west in a distance of 180 miles, but the northern slope is more gentle and apparently more irregular in its distance of 300 miles. The slopes toward Florida and the Yucatdn Peninsula are broken by abrupt changes which undoubtedly represent faults in the bottom. One of the most prominent mounds in the Gulf is found in the northeast portion of the Mexican Basin. It has a relief exceeding 890 fathoms, a possible width of 60 miles, and its top is encoun- tered at a depth of 916 fathoms. SEDIMENTS OF GULF OF MEXICO SOURCE OF SEDIMENTS The near-shore sediments, at least, should be expected to be closely related to the sediments of the adjacent coastal plain except near the mouths of major rivers. Much study has been given samples obtained from wells and outcrops in the area surrounding the Gulf of Mexico. Such studies have shown that each formation varies widely in its composition as it curves around the Gulf from Florida to Mexico. 76 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE The Tertiary outcrops in the Gulf Coastal Plain include thick continental sandy and lignitic deposits and thinner marine sands and clays. Down-dip from the outcrops, drilling has shown that the Tertiary continental deposits pass into brackish water and near-shore marine deposits. According to Lowman (1949, p. 1941), rapid transgressions and slow regressions produced cyclical effects in the sediments with most of the sediments deposited during the regressive phases of the cycles. Farther down-dip or seaward the sediments change to a succession of offshore marine clays. In general, the Gulf coastal area may be di- vided into intergrading depositional areas as fol- lows: Rio Grande Embayment, East Texas Basin, Mississippi Embayment, the Gulf coastal region of Alabama, Georgia, and North Florida, and South Florida. The amount of rainfall on the land area surrounding the ancient Gulf may have been the chief factor in determining the contem- poraneous deposition of many sedimentary de- posits ranging from anhydrite and salt to shales and limestones. Rolshausen (1947, p. 5) sug- gested that during pre-Eagle Ford Cretaceous time, west of the Appalachian Mountains, rivers entering the Gulf from the north and northeast supplied the major load of sediments. East of the mountains the rivers entered the Gulf from the northwest and west. After Eagle Ford time, rivers entering the Gulf from the west, and prob- ably draining the western part of the present Mississippi basin, were the chief source of sedi- ments. The Rio Grande may have been the major source of sediments from the late Cretaceous through early Miocene time with the Mississippi River contributing little sediment during that time. PLACE OF DEPOSITION The sediments brought to the Gulf of Mexico are probably not carried far from shore. Parr (1935, p. 62) showed that at a point only 70 miles out in front of the mouth of the Mississippi River the water has "transparency practically equal to the clearest ocean water known." It is a gen- erally accepted fact that water discharged from the Mississippi River is carried almost entirely to the west and that it stays relatively close to the shore. Clarke (1938, p. 91) found that measure- ments of transparency supported this conclusion. Geyer (1950b, p. 100) noted that the salinity of the offshore coastal waters of Louisiana west of the delta was largely controlled by the discharge of fresh water from the Mississippi River and the westward moving littoral current. The observa- tions of the writer between 1948 and 1951 confirm the westward movement of the fresh water enter- ing the Gulf from the Mississippi River. Cogen (1940, p. 2101) examined samples of sed- iments taken from the bottom of the Gulf near the mouth of the Rio Grande and concluded that the present bottom sediments of this region were carried into the Gulf by the Rio Grande. Bullard (1942, pp. 1021-1043) showed that each of the principal rivers carries a distinct suite of heavy minerals. The Rio Grande sand shows its primary source by the predominance of basaltic hornblende and pyroxene and only 30 percent of the stable minerals such as garnet, rutile, zircon, tourmaline, and staurolite in the heavy mineral residue. The Nueces, San Antonio, Brazos, Trinity, and Sabine Rivers, draining areas of sed- imentary rocks, have little hornblende and pyrox- ene and a high content of stable minerals. Since the Colorado River derives its load from both primary and secondary rocks, its suite of heavy minerals is over half green hornblende. North- ward from the Rio Grande the beach of Padre Island contains the Rio Grande suite of heavy minerals, but the influence of the other rivers is clearly shown by an increased ratio of more stable minerals in the samples farther north in Texas. The sediments of the Coastal Plain do not end at the shore but extend out under the sea, and "if the basement surface on which they rest con- tinues to slope uniformly, the mass of sediments must increase in thickness at least as far as the edge of the continental shelf, beyond which they should thin out rapidly as they merge into the oozes of the ocean depths" (Stephenson 1926, p. 463). Land derived sediments are not being moved in a "continuous sheet of detritus all the way from the beach to the continental slope" (Daly 1942, p. 100). If this were true, much of the con- tinental shelf would be some fathoms shallower than at present. With continuing deposition the sea would become more shallow, and wave and current action would push the sediments nearer the edge of the shelf. When the sediments reached the edge of the continental shelf and a profile of equilibrium was attained, the shelf sur- GULF OF MEXICO 77 face would have been raised several fathoms. Therefore, it appears that a profile of equilibrium does xiot exist on the outer part of broad Gulf of Mexico continental shelves. Sediments carried to the Gulf of Mexico largely remain in that body of water rather than being carried into the Atlantic. The Gulf of Mexico is of no importance to the deep-water circulation of the Atlantic Ocean (Kuenen 1950, p. 44). The unnamed current that becomes the Florida cur- rent is the major current of the Gulf, and "it is essentially a direct continuation of the current through the Yucatan Channel" (Sverdrup, John- son, and Fleming, 1942, p. 642). The waters of the Gulf mainly form independent eddies and are only to a small extent drawn into the Straits of Florida. These eddies appear to be semiper- manent features with their locations determined by the contours of the coast and the configuration of the bottom (idem., p. 641).' EARLY STUDIES OF SUBMARINE DEPOSITS The Coast Survey instituted a series of investi- gations on physical problems of the deep sea in 1846, with emphasis on the Gulf Stream. In 1850, L. Agassiz made an extended biological sur- vey of the Florida reefs, and in 1867, Pourtal6s and Mitchell began a more systematic deep-sea exploration. Dredging between Florida and Cuba in 1868 reached depths of 850 fathoms, and the bottom samples obtained showed a closer relation- ship to the cretaceous fauna rather than to or- ganisms of the adjacent shores. Commander Howell, U. S. N., began a system- atic exploration of the Gulf of Mexico in 1872, starting in the shallow waters along the west coast of Florida, and the work was continued by Lieutenant Commander Sigsbee in 1875-78, using the United States Coast Survey steamer Blake. The specimens of bottom deposits were sent to John Murray of the Challenger for examination, and he published the results in 1885 (Murray, pp. 51-61). Excerpts from his original description are as follows: In all the deeper deposits in the Gulf of Mexico and Strait of Florida, the crystalline mineral particles are very small, rarely exceeding one-tenth of a millimeter in diam- eter. They consist principally of small rounded grains of quartz, with fragments of felspars, mica, hornblende, ' For a detailed discussion of circulation of water in the Oulf of Mexico see article hy D. F. Leippcr, Physical Oceanography of the Gulf of Mexico, in this book. pp. 119-137. augite, magnetite, and rarely tourmaline. In a few places there were fragments of pumice, and glauconitic particles were occasionally noticed. The mineral particles and fine clayey matter appear to be almost wholly derived from North American rivers. The carbonate of lime in the deposits of these regions is mostly made up of the shells of pelagic Foraminifera and MoUusks. In depths greater than 2,000 fathoms the Pteropod and Heteropod shells appear to be nearly, if not quite, absent — the carbonate of lime then consisting of the shells of pelagic Foraminifera; in less depths the Ptero- pod and Heteropod shells are present, and in depths vary- ing from 200 to 500 fathoms they make up the bulk of the deposits in many places. In several of the deposits, where the percentage of carbonate of lime is very high, the whole has a very chalk-like appearance; it appears, indeed, as if it were in the process of transformation to true chalk. The siliceous organisms consist of Radiolarians and Sponge spicules, with a few Diatoms, but these seldom make up more than three or four percent of the whole deposit. A study of the United States Coast and Geo- detic Survey maps of the continental shelf ad- jacent to Louisiana shows many different mate- rials forming the Gulf bottom such as sands, muds, clays, shells, and local reefs. These represent the surface of the Gulf floor, and little is known about the material even immediately below the surface. Some borings have been made in the erection of the platforms required for petroleum exploration, but these platforms are all located approximately within the first 30 miles off shore. The wells drilled from these offshore structures have yielded no known information of the surface formations. Likewise, crews making geophysical surveys in the Gulf are not interested in the surface or near- surface formations (Willey 1948, p. 3). Trowbridge (1927, p. 148) stated that the United States Coast and Geodetic Survey obtained 600 bottom samples in 1921 and that their map of 1926 included the results of this work. RECENT STUDIES OF SUBMARINE DEPOSITS According to Trask, Phleger, and Stetson (1947, p. 460) sediments in the Gulf of Mexico have changed in relatively recent time. During the 1947 expedition of the Atlantis, more than 600 cores were taken along 19 lines perpendicular to the Texas and Louisiana coast, crossing both the continental platform and the continental slope and continuing into the depths of the Gulf. The complete results of this expedition have not been published to date, but some data were discussed by Phleger (1950). It was found 78 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE that sediments off shore were remarkably uni- form. Out to a distance of some 40 miles from shore a combination of fine sand and coarse silt with an average diameter of 100 microns was found; this material was extremely well sorted. On the outer shelf the sediments were much finer, the average diameter being about 1 micron, and they were poorly sorted. In water over 11,000 feet deep in the central part of the Gulf foramini- feral ooze at the surface was underlain, beginning at 2 feet depth, by alternating clay, silt, and sand, the silt and sand being extremely well sorted. A core taken in the Mexican Basin in 1947 is of unusual interest. Trask, Phleger, and Stetson (1947, p. 461) reported that: The upper foraminiferal zone, 50 cm. in thickness, is characterized by a subtropical planktonic fauna . . . Between depths of 50 and 68 cm. in a zone of red clay or red mud, the fauna is transitional between cold and warm water faunas. Between depths of 74 and 78.5 cm., at the top of the zone of banded clay and silt, the fauna is definitely sub-Arctic . . . Between 78.5 cm. and 125 cm., the fauna is cold-water in type but is warmer than that between 74 and 78.5 cm.; and from 125 to 128 cm., at the bottom of the core, the fauna is definitely sub- Arctic. Trask (1948, p. 683) mentioned that ice-age deposits showing crossbedding or ripple marks were found in the coarse elastics of two cores taken in the central Gulf of Mexico. In other cores "well-sorted sand zones, one and three feet, respectively, were encountered at depths of more than three feet beneath the surface of the sedi- ments. Such deposits, if hardened into rock and formed in a geosyncline, would be taken as compatible with the idea of shallow-water depo- sition. Yet they were encountered in 11,000 feet of water." The Fish and Wildlife Service of the United States Department of the Interior, cooperating with the Agricultural and Mechanical College of Texas, is making a systematic survey of the Gulf of Mexico. Much of the physical ocean- ography is being done by the Texas A. and M. Department of Oceanography, and the Depart- ment of Geology is cooperating in the study of Gulf problems of marine geology. Samples of sediments obtained early in 1952 are now being studied. SEDIMENTARY PROVINCES The major sedimentary provinces of the Gulf are shown on the map in figure 16. The basic data for this map were collected from many sources, including the publications of Agassiz, Carsey, Gunter, Kindle, Lowman, Murray, Phleg- er, Price, Shepard, .Stetson, Trask, and Weaver, and by personal communications from individuals principally W. A. Price, Department of Ocean- ography, Agricultural and Mechanical College of Texas. Unfortunately, the data resulting from some 600 cores taken from the Atlantis in 1946 are not yet available. Also, the systematic exploration of the Gulf now in progress will provide many bottom samples from the whole Gulf area, and these data will make possible more detailed sediment maps in the future. The recent sediments are divided into lithologi- cal units which form somewhat indefinite zones parallel to the coast and extending outward on the continental shelf. In general, sands and shales predominate from Florida west and south to Cabo Rojo, Mexico, while limestone forms a wide platform west and north of the Yucatdn Peninsula and west of Florida. EASTERN GULF Modern calcareous sediments were thought by Agassiz (1888, p. 286) to cover the continental shelf on the west side of Florida. The charts of this area show "sand and shells" and are therefore deceiving. Samples from this region that were examined by Shepard (1932, p. 1021) "were lacking in quartz-sand and the use of sand as a textural term seemed questionable." Little sediment goes to the Gulf in streams from the Florida Peninsula, and the shore deposits consist largely of calcium carbonate secreted by organisms. Even the Apalachicola River does not discharge an appre- ciable amount of clay and silt. However, some quartz sand is found relatively near shore from Mississippi eastward across Alabama and the panhandle and near shore along the northern part of the west coast of Florida. Also, recently, num- erous sand bars have been found on the northern part of the continental shelf west of the Florida Peninsula. The area off shore from Alabama and the pan- handle of Florida has detrital sediments which show the influence of the southern Appalachians. These sediments contain an abundance of ilmenite, staurolite, kyanite, zircon, tourmaline, and silli- manite, and only minor amounts of magnetite, GULF OF MEXICO 79 80 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE amphiboles, pyroxenes, leucoxene, and hematite (Goldstein 1942, p. 81). Most of the continental shelf west of the penin- sula of Florida is hard rock, chiefly limestone, but a thin veneer of detrital sediment is present in local areas and fills some of the shelf depressions. Stetson (1951, p. 1993) obtained two specimens of hard limestone and a specimen of soft, chalky limestone from this shelf by using a steel rock dredge after core tubes were damaged by the hard rock. The Florida Keys include a 200-mile chain of islands curving southwestward along the edge of the Florida Straits from Biscajme Key to Key West and the Dry Tortugas. The northeastern keys are old coral reefs, but the ones to the south- west are remnants of a former island. Vaughan (1910, p. 119) stated that silica, as sand, is abun- dant in Biscayne Bay but decreases to the south- west as calcium carbonate becomes more abundant near the living coral reefs. The calcium carbonate occurs "as a flocculent sediment or ooze over practically the entire region from the lower portion of Biscayne Bay to the gulf end of Florida Bay." However, Trask (1932, pp. 166-172) found that the basins in Florida Bay have coarser sediments than the compact marl rims. The basin sediments are "shell breccia embedded in a matrix of marl." The recent work of Lowman (1951, pp. 234-235) provided the basis of division of the limestone banks west of Florida. He found that the white sands of the Pensacola beaches extended seaward to the depth of 20 fathoms and that the sands were free of mud and were highly fossiliferous, with Mollusca and Foraminifera being the most common forms. A second zone, extending out to 40 fathoms, was found to contain many algae, forams, pelecypods, brachiopods, bryozoans, and cup corals. The Foraminifera showed a definite faunal break at about 75 fathoms which Lowman (idem., p. 235) suggested may be the result of changes in turbidity and light penetration in the clear water. In the more turbid waters west of the Mississippi Delta a faunal break was noted at 45 to 50 fathoms. Bush (1951, pp. 102, 106) reported on a rock specimen obtained by dredging in the Straits of Florida, south of the American Shoals, at a depth of 375 fathoms. This rock, apparently broken from the ocean floor, was very fossiliferous and was correlated with the Chipola formation (lower Miocene) of northern Florida. This suggests "the dip and continuance of the lower Miocene strata from the Florida Peninsula under the Straits of Florida toward Cuba" (idem., p. 106). Between the Florida Straits and Cuba and also west of the continental shelf the bottom sediments are calcareous muds, and westward they grade into blue mud and Globigerina ooze. MISSISSIPPI DELTA Most of the coarse sediment of the Mississippi River is deposited near its mouth, but Trowbridge (1930, p. 892) noted that outside the Southwest Pass of the river, coarser sediment occurred oa knolls in 30 fathoms of water. This coarser sedi- ment apparently was not derived from the present Mississippi River under present conditions. The concentration of coarse sediments may have resulted from the removal of the finer sediments by winnowing due to stronger currents over the knolls. Shaw (1916, p. 107) stated that fine sand, sUt, and clay were accumulating on the Gulf of Mexico floor immediately beyond the mouth of the Mis- sissippi River very near where they were dropped by the river. He contrasted this with conditions on the west Gulf coast where the sediments brought to the Gulf by streams were being re- worked by waves and currents yet not carried far from the mouths of the streams. Mud and sand are recorded on many maps on either side and adjacent to the Mississippi River, but sampling by the writer shows silt and "mud" to be greatly in excess of sand. Westward from the delta there is a clay-silt zone with some sand and shells. Dark gray to black "mud" is present in most of the lagoons. Kellogg (1905, p. 34) and many others, including the writer, have observed the hard crust that develops during the winter. This crust is only an inch or two thick and is underlain by soft silt and "mud." The clay and finest particles have probably been removed by winnowing during the winter when the Mississippi River is in a low stage and therefore carrying a minimum sediment load. The very high ratios of organic matter to chlorophyll which occur near the mouth of the Mississippi River "indicate large quantities of organic detritus. The ratios fall so rapidly as one proceeds out in the Gulf that it seems likely that practically all the organic detritus of fresh water origin is removed from the surface water GULF OF MEXICO 81 before it gets more than ten or fifteen miles from the mouth of the river" (Riley 1937, p. 91). It is noted in figure 16 that the blue mud province extends northward to near the mouths of the Mississippi River. Since the front of the delta overlaps the continental shelf nearly to its outer edge, the sediments of the deeper Gulf approach the tip of the delta. Likewise, the Globigerina zone lies close to the land at the delta. LOUISIANA SHELF The numerous submerged hills rising above the sea floor near the outer edge of the continental shelf materially influence the local sediments. Trask, PUeger, and Stetson (1947, p. 461) noted that the slopes of these hills are covered with "silty, calcareous sand, and the tops by round Lithothamnium balls and little or no sandy material . . . while the adjacent flat continental shelf is underlain by sandy silt." The Lithothamnium balls, diameters up to 10 cm., must have been moved by the water since they seemed to be alive on all sides. Corals, similar to those common in the West Indies, were dredged with the Litho- thamnium balls. These areas are included in figure 16 in the patches of coral lying along 28° N. lat. between 91° and 95° W. long. The dominant sediment on the continental shelf along the Louisiana coast west of the Mis- issippi Delta is mud and sand. Locally, near shore, sand predominates to form a sand beach and shore zone. The common, heavy minerals of these sediments are amphiboles, epidote, dolomite, pyroxene, ilmenite, and biotite. Near the outer edge of the shelf and particularly on the continental slope there are many topo- graphic features of considerable relief. Carsey (1950, pp. 377-379) noted 164 such topographic features along the Louisiana-Texas slope and made a study of their density distribution accord- ing to their degree of relief. This study showed that two-thirds of these features have a relief of less than 300 feet, while some rise 600 feet above the floor of the Gulf. The sediments on the tops and flanks of topo- graphic features, having a relief in hundreds of feet, may be greatly different from those on the ocean floor only a short horizontal distance away. Corals have been dredged from the tops of a few of these knobs or domes, but little is known con- cerning the deposits on the flanks. The finer sediments may have been washed from the tops of these knobs to settle on the Gulf floor around the base. More detailed sounding and dredging in this area are needed to adequately study the sedimentology of the area. Over a 50-year period numerous "oil spots" or "seeps" have been reported as having been ob- served in the northwest Gulf of Mexico. The locations of these seeps are noted on the map (fig. 16), and it is seen that they are concentrated between 91°-93° W. and 26°30'-27°30' N. Since several of these "oil spots" were said to be several scores of miles long, their origin, although un- known, is of interest. WESTERN GULF The rivers of Texas are not heavily laden with sediment, except during flood stages, and for this reason it can be assumed that the Recent alluvial deposits found on the continental shelf will not be of great thickness. Also, these streams have little velocity as they cross the wide coastal plain, and only fine-grained mechanical sediments are carried to the Gulf. This has been shown by Storm (1945, p. 1313) in a series of samples col- lected in the Gulf out from Corpus Christi, Texas. Beyond the near-shore fine material sands with 0.21 millimeter average diameter occurred in a narrow belt about 12 miles from shore. Twenty miles from shore the grain size had decreased to an average of 0.03 millimeter, while 30 miles from shore it had increased to an average of 0.18 milli- meter. From 30 to 40 miles off shore the grain size remained about the same, but beyond 40 miles it decreased again. These variations seem to be closely associated with the currents. In 1948 Mattison (p. 77-78) found a string of coral heads off the Brazos River mouth about 8 miles off shore. They occur in 6 to 8 fathoms of water and have a relief of 2 to 3 fathoms. They have been seen by fishermen who describe them as having the appearance of sunken icebergs but having sea fans and other marine growth forming solid coral or white limestone in an area of black mud. Coral heads occur approximately along the 40-fathom line in front of Corpus Christi, Texas, and Smith (1948, p. 82) noted that six of these heads were reached within a foot or two of 31 fathoms of water. Along most of the east coast of Mexico from Texas to the Gulf of Campeche the charts show 82 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE "sand" near shore and "mud" off shore, showing an outward gradation of sediments. Agassiz (1878, p. 1) found the fauna of the Yucatan Bank to be identical with that of the Florida Bank, being characterized by the same species of echinoderms, mollusks, crustaceans, corals, and fishes. From Tampico southward beyond Veracruz volcanic rocks are found near shore, and possibly igneous rocks will be found in the adjacent Gulf waters. Therefore, the sediments in this area should be somewhat different from those off southern coastal Texas and from those associated with the limestone of the Campeche Banks to the east. The coastal plain is exceedingly narrow locally, and the beach sands give way to near- shore patches of coral. In many places mud extends out on the shelf beyond the coral. YUCATAN PENINSULA The beach sands along the west and north shores of the Yucatan Peninsula do not spread far from shore except locally where sand and mud are found out to the edge of the shelf. To the southwest of the peninsula the sand becomes mixed with near-shore coral patches. Numerous local patches of coral occur over the Campeche Banks, and in other places the bottom is very similar to the Florida Bank. The hard limestone is locally covered with a thin veneer of detrital sediments. The Globigerina ooze prov- ince joins the Campeche Banks apparently with the blue mud absent between these calcareous sediments. CUBA Corals are common at the outer edge of the narrow shelf off the northern coast of Cuba. Beyond these corals the Florida Straits contain calcareous mud with the exception of a local area to the northwest of Cuba where pteropod ooze has been found. A bottom sample taken in 20 fathoms of water at 24°25' N. lat. and 82°26' W. long, was sub- jected to a chemical and spectrographic analysis. Also, use was made of electrolytic separation in a mercury cathode cell to concentrate the trace elements. No unusual trace elements were found, and the common elements were in approximately the same abundance as has been determined by others who analyzed the skeletal material of organisms which contribute to sediment formation. MEXICAN BASIN The upper surface of the floor in the deepest part of the Gulf consists of foraminiferal ooze. The few available cores show the underlying sedi- ment to be clay, silt, and sand, which is cross- bedded and ripple-marked in some cores. The origin of this detrital material is unknown as is also the origin of the basin forming the Gulf. Turbidity currents may have brought much sedi- ment to the central Gulf. Such an origin is further suggested by the presence of continental- shelf Foraminifera in the Mexican Basin sediments. Agassiz (1888, pp. 280-282) quoted Murray who observed that the globigerine and pteropod ooze found in the central Gulf of Mexico differed materially from that found in the oceanic basins. Diatoms, radiolarians, and sponge spicules com- prise the siliceous organisms but represent only a small percentage of the bottom deposits. Fish oto- liths were found at depths from 392 to 1,568 fath- oms. The globigerine ooze was found to extend northward to the Mississippi River slope where it was replaced by dark, rich muds containing "a number of interesting forms of annelids, mollusks, ophiurous and sea-urchins, characteristic of the continental Gulf slope, and typical of mud deposits" (idem., p. 282). CONCLUSIONS The Gulf of Mexico, with a surface area of 615,000 square miles, offers many rewards for research in geology, biology, and oceanography. Continued drilling at the extreme margins of the Gulf may produce new local data as greater depths are reached by the drill, but much of the search must be made far from shore. To date most of the geophysical prospecting has been in the very shoal areas where present methods of development may apply. The use of geophysics to study the tec- tonics of the Gulf largely lies in the future. Therefore, it seems that present aid in solving the many problems of the Gulf of Mexico must come from the oceanographer who can give other scientists new data from soundings, bottom samples, and the physical characteristics of the water. While the time and manner of the origin of the Gulf basin are still undetermined, present evidence favors the existence of a shallow Gulf, the "plate" of Suess and Schuchert. Assuming that Llanoria GULF OF MEXICO 83 extended into the Gulf, its submergence may have been completed by late Jurassic time, thus pro- viding for the uivasion by the Cretaceous seas. Post-Cretaceous downwarping tilted the Creta- ceous deposits Gulfward, but, in general, the Gulf remained a shallow sea during most of the early Tertiary. During late Tertiary the basin of the Gulf further subsided, possibly both by down- warping and faulting along the basin margins. The escarpment along the west edge of the Florida shelf (Jordan 1951, pp. 1978-1993) un- doubtedly has its origin in faulting, and similar conditions seem to e.xist at the outer edge of the Campeche Banks. Other areas along the con- tinental slope suggest fault scarps. The basin of the Gulf may well have been deeper than the present 12,425 feet, with post-mid-Tertiary sedi- ments filling the basin to its present depth. There is no reason to believe that the irregu- larities of the continental slope are confined to the local areas which have had detailed study, and further hydrographic work should produce data of great scientific value. Interest in the Gulf has been greatly accelerated in the past decade, and there is much evidence that this interest will continue, which should result in the eventual solution of many of the present riddles of the Gulf of Mexico. BIBLIOGRAPHY Agassiz, Alexander. 1878-J879. No. 1.— Letter No. 1 to C. P. Patterson, Superintendent United States Coast Survey, on the dredging operation.s of ttie United States Coast Survey steamer Blake. Bull. Mus. Comp. ZooL, Harvard Coll., 5: 1-9. No. 6.— Letter No. 2 to C. P. Patter- son . . . ibid., pp. 55-64. No. 14. — Letter No. 3 to C. P. Patterson . . . ibid., pp. 289-302. 1888. Three cruises of the United States Coast and Geodetic Survey steamer Blake in the Gulf of Me.\- ico . . . from 1877-1880. Bull. Mus. Comp. Zool., Harvard Coll., 14: 1-314. 1896. The Florida elevated reef. Bull. Mus. Comp. Zool., Harvard Coll., 28: 29-62. Barton, D. C, C. H. Ritz, and M. Hickey. 1933. Gulf coast geosyncline. Bull. Am. Assn. Petrol. Geols. 17 (12): 1446-1458. BoRNHAUSER, MaX. 1947. Marine sedimentary cycles of Tertiary in Mis- sissippi embayment and central Gulf coast area. Bull. Am. Assn. Petrol. Geols. 31 (4): 698-713. Bt'LLARD, F. M. 1942. Source of beach and river sands on Gulf coast of Texas. Bull. Geol. Soc. Am., Pt. 2, 53 (7) : 1021-1044. 259534 O— 54 7 Bush, James. 1951. Rock from Straits of Florida. Bull. Am. Assn. Petrol. Geols. 35 (1): 102-107. Carsey, J. B. 1950. Geology of Gulf coastal area and continental shelf. Bull. Am. .\ssn. Petrol. Geols. 34 (3): 361-386. Clarke, G. L. 1938. Light penetration in the Caribbean Sea and in the Gulf of Me.xico. Jour. Mar. Res. 1 (2): 85-94. COGBN, W. M. 1940. Heavy mineral zones of Louisiana and Texas Gulf coast sediments. Bull. Am. Assn. Petrol. Geols. 24 (12): 2069-2101. Daly, R. A. 1936. Origin of submarine canyons. Am. Jour. Sci., 5th Ser., 31:401-420. 1942. The floor of the ocean. 177 pp. University of North Carolina Press, Chapel Hill, N. C. Dana, J. D. 1863. Manual of geology. 1st ed., 798 pp. T. Bliss and Co., Philadelphia. 1883. The Tortugas and Florida reefs. Am. Jour. Sci., 3rd Ser., 26: 408-409. Darwin, C. R. 1914. The structure and distribution of coral reefs. 3rd ed., 355 pp. Appleton, N. Y. DiCKESON, M. W., and A. Brown. 1848. The sediments of the Mississippi. Proc. Am. Assn. Adv. Sci. 1 : 42-55. DOHM, C. F. 1936. Igneous, metamorphic and sedimentary pebbles from the Chandeleur Islands. Louisiana Dept. Conserv. Geol. Bull. 8: 397-402. Eardley, J. A. 1951a. Structural geology of North America. 624 pp. Harper and Bros., New York. 1951b. Tectonic divisions of North America. Bull. Am. Assn. Petrol. Geols. 35 (10): 2229-2237. Emery, K. O. 1950. A suggested origin of continental slopes and of submarine canyons. Geol. Mag. 87 (2): 102-104. FisK, H. N. 1944. Geological investigation of the alluvial valley of lower Mississippi River, Miss. River Comm., War Dept., Corps of Engrs., U. S. Army, 78 pp. Fli.vt, R. F. 1947. Glacial geology and the Pleistocene epoch. 589 pp. John Wiley, N. Y. Geyer, R. a. 1950a. Bibliography of Gulf of Mexico. Texas Jour. Sci. 2(1): 44-92." Geyer, R. A. 1950b. The occurrence of pronounced periodic salinity variations in Louisiana coastal waters. Jour. Mar. Res. 9 (2): 100-110. GlaessiNer, M. F., and C. Tei chert. 1947. Geosynclines : fundamental concept in geology. Am. Jour. Sci. 245: 465-482, 571-591. Goldstein, August, Jr. 1942. Sedimentary petrologic provinces of the northern Gulf of Mexico. Jour. Sed. Petrology 12 (2): 72-84. 84 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE GuNTER, Gordon. 1947. Catastrophism in the sea and its paleontological significance, with special reference to the Gulf of Mexico. Am. Jour. Sci. 245 (II): 669-676. GuNTER, Herman. 1929. Geology of Florida. Florida State Geol. Sur., Twentieth Ann. Rept., 1927-28. Haberle, F. R. 1951. Gulf coast geosyncline. Texas Jour. Sci. 3 (3): 368-375. Heilprin, a. 1891. Geological researches in Yucatan. Proc. Acad. Nat. Sci. Philadelphia 43: 136-158. HiLGARD, E. W. 1871. Geological history of the Gulf of Mexico. Am. Jour. Sci., 3rd Ser., 2: 391-404. HlLGARD, E. W. 1881. The later Tertiary of the Gulf of Mexico. Am. Jour. Sci., 3rd Ser., 22: 58-65. 1881. The basin of the Gulf of Mexico. Am. Jour. Sci., 3rd Ser., 21: 288-291. Hill, R. T. 1898. Cuba and Puerto Rico, with other islands of the West Indies. 429 pp. Century Co., New York. Houston Geological Society. 1951. Western Gulf coast. Bull. Am. Assn. Petrol. Geols. 35 (2) : 385-392. Howe, H. V. 1936. Stratigraphic evidence for Gulf coast geosyncline. Bull. Geol. Soc. Am., Proc. 1935, p. 82. Howe, H. V., R. J. Russell, and J. H. McGuirt. 1935. Physiography of coastal southwest Louisiana. In: Reports on the geology of Cameron and Vermilion Parishes. Louisiana Dept. Conserv. Geol. Bull. 6: 1-72. Jones, C. T., and S. L. Mason. 1948. Marine exploration in Gulf of Mexico. Bull. Am. Assn. Petrol. Geols. 32 (12): 2315-2316. Jordan, G. F. 1951. Continental slope off Apalachicola River, Florida. Bull. Am. Assn. Petrol. Geols. 35 (9): 1978-1993. Kellogg, J. L. 1905. Notes on marine food niollusks of Louisiana. Gulf Biologic Sta., Bull. 3: 34-36. Kindle, E. M. 1936. Notes on shallow- water sand structures. Jour. Geol. 44: 866-867. King, P. B. 1950. Tectonic framework of southeastern United States. Bull. Am. Assn. Petrol. Geols. 34 (4): 635- 671. 1951. The tectonics of middle North America. 203 pp. Princeton University Press, Princeton, N. J. KORNFELD, M. M. 1931. Recent Gulf coast Foraminifera of Texas and Louisiana. Bull. Geol. Soc. Am. 42 (1): 371. Krumbein, W. C. 1939. Tidal lagoon sediments on the Mississippi Delta. In: Recent marine sediments. 189 pp. Am. Assn. Petrol. Geols., Tulsa, Okla. Krumbein, W. C, and Esther Aberdeen. 1937. The sediments of Barataria Bay. Jour. Sed. Petrology 7 (1): 3-17. Krumbein, W. C, and L. T. Caldwell. 1939. Area variation of organic carbon content in Barataria Bay sediments, Louisiana. Bull. Am. Assn. Petrol. Geols. 23 (4) : 582-594. KUENEN, P. H. 1950. Marine geology. 568 pp. John Wiley, New York. Lawson, A. C. 1942. Mississippi Delta, a study in isostasy. Bull. Geol. Soc. Am. 53: 1231-1254. Lees, G. M. 1951. Nature of continental shelves. Bull. Am. Assn. Petrol. Geols. 35 (1): 108-109. LOWMAN, S. W. 1949. Sedimentary fades in Gulf coast. Bull. Am. Assn. Petrol. Geols. 33 (12): 1939-1997. 1951. The relationship of the biotic and lithic facies in the Recent Gulf coast sedimentation. Jour. Sed. Petrology 21 (4): 233-237. Marmer, H. a. 1949. Sea level changes along the coasts of the United States in recent years. Trans. Am. Geophys. Union 30 (2): 201-204. Mattison, G. C. 1948. Bottom configuration in the Gulf of Mexico. Jour. Coast and Geod. Surv., (1): pp. 76-82. Maury, C. J. 1920. Recent mollusks of the Gulf of Mexico and Pleistocene and Pliocene species from the Gulf States. Part I. Pelecypoda. Bull. Am. Paleontol. 8, 113 pp. Maury, C. J. 1922. Recent MoUusca of the Gulf of Mexico and Pleistocene and Pliocene species from the Gulf States. Part II. Scaphoda, Gastropoda, Amphineura, Ce- phalopoda. Bull. Am. Paleontol. 38, 142 pp. McGee, W. J. 1892. The Gulf of Mexico as a measure of isostasy. Am. Jour. Sci., 3rd Ser., 44: 177-192. Meyer, W. G. 1939. Stratigraphy of Gulf coastal plains. Bull. Am. Assn. Petrol. Geols. 23 (2): 145-211. Moody, C. L. 1931. Tertiary history of region of Sabine uplift, Louisiana. Bull. Am. Assn. Petrol. Geols. 15 (5): 531-553. 1950. Geologic history of the Gulf of Mexico. Lecture before Geology Club, Texas Agric. and Mech. College, March 28, 1950. Morgan, J. P. 1951. Mudlumps at the mouths of the Mississippi River. Dissertation, Louisiana State Univ., 1951. MuiR, J. M. 1936. Geology of the Tampico region, Mexico. 280 pp. Am. Assn. Petrol. Geols., Tulsa, Okla. GULF OF MEXICO 85 Murray, John. 1885. XXVII. Report on the specimens of bottom deposits. In: Reports on the results of dredging under the supervision of Alexander Agassiz . . . by the U. S. S. Blake. Bull. Mus. Comp. Zool., Har- vard Coll., 12: 37-Gl. Parr, A. E. 1935. Report on hydrographie observations in the Gulf of Mexico and the adjacent straits made during the Yale Oceanographic Expedition on the Mabel Taylor in 1932. Bull. Bingham Oceanog. Coll., Yale Univ., 5,(1) :93 pp. Phleger, F. B. 1939. Foraminifera cores from the continental slope. Bull. Geol. Soc. Am. 50: 1395. 1950. Offshore sedimentology, northwest Gulf of Mex- ico. Lecture before Houston (Texas) Geol. Soc, Feb. 13, 1950. Pratt, W. E. 1947. Petroleum on continental shelves. Bull. Am. Assn. Petrol. Geols. 31 (4): 657-672. Pratt, W. E., and Paul Weaver. 1950. Discussion of variations in history of continental shelves. Bull. Am. Assn. Petrol. Geols. 34 (7): 1589-1592. Price, W. A. 1947. Role of diastrophism in topography of Corpus Christi area, south Texas. Bull. Am. Assn. Petrol. Geols. 17: 907-962. 1951. Building of Gulf of Mexico. 1st Ann. Meet. Gulf Coast Assn. (3eol. Soc. (New Orleans), Shreve- port, La. Richardsg.m, C. B. 1945. Sedimentation of the Gulf coast (N. A.). Abst., Tulsa (Okla.) Geol. Soc. Digest, 1944-45, 13: 76. Riley, G. A. 1937. The significance of the Mississippi River drainage for biological conditions in the northern Gulf of Mexico. Jour. Mar. Res. 1: 60-74. ROLSHAUSEN, F. W. 1947. Report of the committee on a treatise on marine ecology and palecology, 1946-47. Natl. Res. Coun., Div. of Geol. and Geog., No. 7. RUS.SELL, R. J. 1936. Physiography of lower Mississippi Delta. In: Geology of Plaquemines and St. Bernard Parishes. Louisiana Dept. Conserv. Geol. Bull. 8: 3-193. 1937. Mineral composition of Mississippi River bed materials. Bull. Geol. Soc. Am. 48: 1307. 1940. Quaternary history of Louisiana. Bull. Geol. Soc. Am. 51: 1228. H. N. FisK. 1942. Isostatic effects of Mississippi River Delta sedimentation. Int. Assn. Geodesy, Washington As- semblage, Rept., App. 3, pp. 56-59. and R. D. Russell. 1939. Mississippi River Delta sedimentation. In: Re- cent marine sediments. Pp. 153-177. Am. Assn. Petrol. Geols. ScHUCHERT, Charles. 1929. Geological history of the Antillean region. Bull. Geol. Soc. Am. 40 (1): 340. 1935. Historical geology of the Antillean-Caribbean region or the lands bordering the Gulf of Mexico and the Caribbean Sea. 81 1 pp. John Wiley, New York. Sellards, E. H. 1919. Geology of Florida. Jour. Geol. 27 (4): 286-302. Shaw, E. W. 1916. Sedimentation along the Gulf coast of the United States. (Abstract) Bull. Geol. Soc. Am. 27: 71. Shepard, F. P. 1932. Sediments of continental shelves. Bull. Geol. Soc. Am. 43: 1021. 1937. Salt domes related to the Mississippi submarine trough. Bull. Geol. Soc. Am. 48: 1349-1361. 1948. Submarine geology. 337 pp. Harper & Bros., New York. — and K. O. Emery. 1941. Submarine topography off the California coast. Bull. Geol. Soc. Am. 31: 1-171. Smith, P. A. 1948. Comment. Bottom configuration in the Gulf of Mexico. Jour. Coast and Geod. Surv., (1): 76-82. Spencer, J. W. 1895. Reconstruction of the Antillean continent. Bull. Geol. Soc. Am. 6: 103-140. Staub, Walther. 1931. Zur entstehungsgeschichte des golfes von Mexico. Ecolog. Geol. Helvetiae 24: 61-81. Steinmatbr, R. a. 1931. Bottom sediments of Lake Pontchartrain, Louisi- ana. Bull. Am. Assn. Petrol. Geols. 23: 1-23. Stephenson, L. W. 1926. Major features in the geology of the Atlantic and Gulf Coastal Plain. Jour. Washington Acad. Sci. 16 (17): 460-480. Stetson, H. C. 1951. Comment on continental slope off Apalachicola River, Florida. Bull. Am. Assn. Petrol. Geols. 35 (9) : 1992-1993. Storm, L. W. 1945. Resume of facts and opinions on sedimentation in Gulf coast region of Texas and Louisiana. Bull. Am. Assn. Petrol. Geols. 29 (9) : 1304-1335. SuEss, Eduard. 1885. Das antlitz der erde (The face of the earth). Vols. 1 and 2 (Eng. trans, by Sallas and Sallas), Oxford (Clarendon Press). SvERDRUP, H. U., M. W. Johnson, and R. H. Fleming. 1942. The oceans. 1087 pp. Prentice-Hall, Inc., New Y'ork. T.^TUM, J. L. 1931. General geology of northeastern Mexico. Bull. Am. Assn. Petrol. Geols. 15: 867-893. Thorp, E. M. 1931. Description of deep-sea bottom samples from western North Atlantic and Caribbean Sea. Scripps Inst. Oceanog., Tech. Ser. 3 (1): 8. 86 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Trask, p. D. 1932. Origin and environment of source materials of petroleum. 323 pp. Gulf Publishing Co., Houston, Tex. 1948. Oceanography and geosynclines. Jour. Mar. Res. 7 (3) : 679-685. Trask, P. D., F. B. Phleger, Jr., and H. C. Stetson. 1947. Recent changes in .sedimentation in the Gulf of Me.xico. Science 106 (2759): 460-461. Treadwell, T. K. 1949. Submarine topography of continental slope of northwest Gulf of Mexico. Submarine Geol. Rept. No. 7, Scripps Inst. Oceanog., Univ. Calif., 7 pp. Trowbridge, A. C. 1927. Disposal of .sediments carried to the Gulf of Mexico by Southwest Pass, Mississippi River. (Ab- stract) Bull. Geol. Soc. Am. 38 (1): 148. 1930. Building of the Mississippi Delta. Bull. Am. Assn. Petrol. Geols. 14: 867-901. Turner, H. J. 1903. Examination of mud from the Gulf of Mexico. U. S. Geol. Surv. Bull. 212: 107-112. Umbgrove, J. H. F. 1946. Origin of continental shelves. Bull. Am. Assn. Petrol. Geols. 30 (2) : 249-253. 1947. The pulse of the earth. 358 pp. Nijhoff, The Hague. Van Der Gracht, W. A. J. v. W. 1931. The Permo-Carboniferous orogeny in the south- central United States. K. Akad. Wetens., Amster- dam, Verh., Afd. Natuurk., 2d Sect., 27 (3): 121. Vaughan, T. W. 1902. Evidence of recent elevation of the Gulf coast along the westward extension of Florida. Science, n. s., 16: 514. 1909. Geology of the Florida Keys and the marine bot- tom deposits and recent corals of southern Florida. Carnegie Inst. Washington Year Book 7, pp. 131-136. 1910. A contribution to the geologic history of the Floridian plateau. Carnegie Inst. Washington Pub. 133, pp. 99-185. Vaughan, T. W. 1914. The building of the Marquesas and Tortugas atolls and a sketch of the geologic history of the Florida reef tract. Carnegie Inst. Washington Pub. 182: 55-67. 1918. Geologic history of Central America and the West Indies during Cenozoic time. Bull. Geol. Soc. Am. 29: 615-620. 1940. The classification and nomenclature of the sub- marine features of the Gulf of Mexico and the Carib- bean Sea. D'Oceanographie Physique, Union Geo- desique et Geophysique Internationale, Pub. Scien- tifique No. 8. Vaughan, T. W., and E. W. Shaw. 1915. Geologic investigations of the Florida coral reef tract. Carnegie Inst. Washington Year Book 14: 232-238. Veatch, a. C, and Smith, P. A. 1939. Atlantic submarine valleys of the United States and the Congo submarine valley. Geol. Soc. Am., Spl. Paper No. 7, 101 pp. Weaver, Paul. 1950. Variations in history of continental shelves. Bull. Am. Assn. Petrol. Geols. 34 (3): 351-360. Willey, M. B 1948. Engineering characteristics of the Gulf coast con- tinental shelf (La.). Am. Inst. Min. Engrs., Tech. Pub. 2323, Petr. Tech. 11 (2): 1-11. Williams, H. F. 1950. The Gulf of Mexico adjacent to Texas. Texas Jour. Sci. 3 (2) : 237-250. Willis, B. T. 1929. Continental genesis. Bull. Geol. Soc. Am. 40: 281-336. WOLLARD, G. P. 1936. An Interpretation of gravity anomalies in terms of local and regional geologic structures. Trans. Am. Geophys. Union, Pt. 1, pp. 70-73. CHAPTER III MARINE METEOROLOGY OF THE GULF OF MEXICO MARINE METEOROLOGY OF THE GULF OF MEXICO, A BRIEF REVIEW By Dale F. Leipper, Department of Oceanography, Agricultural and Mechanical College of Texas The best general summary of the weather over the Gulf of Mexico in nontechnical langjuage is probably that prepared by the United States Weather Bureau for the United States Coast Pilot (1949). There are a number of articles on the general circulation of the atmosphere and on meteorological processes without specific reference to the Gulf of Mexico which, nevertheless, pertain to this region as well as to all similar regions. It will not be attempted to review such articles in the present summary. Two references of this type are Holmboe, Forsythe, and Gustin (1948), and Byers (1944). In addition, there are some publi- cations such as Riehl (1947) which deal with the general weather in the low latitudes and are helpful in understanding the Gulf of Mexico weather more completely. EXTRATROPICAL CYCLONES Saucier (1949) has analyzed the frequency and behavior of extratropical cyclones originating on or near the northwestern coast of the Gulf of Mexico over a 40-year period. These cyclones have marked effect upon the weather of the Gulf as well as upon that of much of the eastern United States. They occur on the average about 10 times per year with a maximum number of 19 occurring in 1899 and a minimum of 2 in 1916. The high frequency of these storms appears to result from the influence on the general circulation of the warm moist surface provided by the Gulf of Mexico, the cold continental air to the north, and the mountains to the west. It was found that the cyclones seldom occurred immediately after a deep cold air mass penetrated the entire Gulf of Mexico but were most common when it remained north of the Gulf coast. The storms may begin as early as October. The maximum number occurs in January. Very few occur later in the ' Contribution from the Department of Oceanography of the Agricultural and Mt'chanieal College of Texas, Oceanographic Series No. 20. Based in part upon work done under the sponsorship of the Office of Naval Research and the .\ir Force Cambridge Research Center. 2 References are listed at the end of the chapter. spring than April. The regions of formation, directions of motion, and the characteristics of the intensification of the 388 cyclones studied are discussed. THE GENERAL AIR CIRCULATION AND SOME OF ITS CONSEQUENCES The Bermuda atmospheric high pressure cell dominates the circulation over the Gulf, partic- ularly during the spring and summer months. In the late summer there is a general northward shift of the circulation and, as shown in figure 17, the Gulf comes under the more direct influence of the equatorial low pl-essure belt. The constancy of the Bermuda high tends to maintain steady circulation and to govern the climate during the summer. Summer conditions are illustrated in figure 18. No isotherms appear for average water temperature (sea surface temperature) since the waters are nearly uniform at about 84° F. as illustrated in the chapter on physical oceanog- raphy.' The air temperatures on the average are also quite uniform and high. The southerly posi- tion of the Bermuda cell brings about the south- east-northwest orientation of isobars across the Gulf and leads to a predominance of southeasterly winds, as shown by wind arrows. The winds tend to become more soullu>rly in the northern part of the Gulf. In this region there are prac- tically no northerly winds in summer and only a relatively few from the east or the west. In the more southern parts of the area the predomi- nance of the easterly and southeasterly flow is even more marked. With a typical summer circulation in the Gulf and the uniform average sea surface temperature, there would be expected only a minimum lunnber of local weather features over the water which are the type caused within the Gulf by air flow toward successively warmer or cooler water sur- faces. However, on a larger scale the relatively I See Physical Oceanography of the Gulf of Mexico, p. 119. 89 90 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Figure 17. — Normal sea level pressure, October. high temperature of the Gulf of Mexico waters compared to those of other water surfaces in the same latitudes brings about such a great warming and increase in the moisture content of the over- lying air masses that weather patterns of the area are markedly affected. (The mean annual sur- face temperature of the Gulf is 78° F., while that of a comparable region at the same latitude in the western Atlantic is 76°, in the eastern Atlantic 73°, and in the eastern Pacific 68°). Typical features of the winter circulation are shown in figure 19. Here the winds are more from the easterly directions with fewer southerlies but more northerlies. There are very few winds from the west or the southwest. The sea surface tem- perature pattern shows a variation from more than 75° F. in the southeastern portion to less than 65° in the northwest. Southeasterly winds bring warm, moist air from lower latitudes and carry it from warmer toward colder water in the Gulf. When this flow is slow and sustained, the cooling by the ocean surface leads to condensation and fog and stratus formation in the northern Gulf. A discussion of the upper air circulation for the Gulf and Caribbean area is given by Erna and Rudolf Penndorf (1944). AVERAGE CONDITIONS Average sea-level atmospheric pressures in the Gulf vary from 30.00 to 30.15 inches of mercury. There a>"e wide deviations from these averages in individual synoptic situations. Worthy of note is the diurnal pressure variation with a lesser early morning minimum followed by a greater late morning maximum and evening minimum and a lesser nocturnal maximum. The Atlas of Climatic Charts of the Oceans, published by the United States Weather Bureau, and the Pilot Chart of Central American Waters, published by the Hydrographic Office of the United States Navy, issued monthly, give further information about the winds, pressures, tempera- GULF OF MEXICO 91 tines, and other weathei- features of the Gulf of Mexieo, The average wind velocity varies fioni ti to 8 knots in the summer, with the stronj^er winds in the southeast portion, to 10 to 12 knots with considerable variability in the winter, the higher averages being in the northeastern portions. P^og is most frequent in midwinter when as high, as U) percent of all observations record light or dense fog in the north central part of the Gulf. In this season fogs occur less than 1 percent of the time in the soutiieastern portion. For the year-round the average cloud-cover over the Gulf is Yio to %o of the sky obscured. In winter and sjjring the areas most obscured are in the north and northwest, while in the summer and fall the southern and southwest portions have the highest average cloud cover. The most commonly reported low type clouds are cumulus . AVERAGE SEA LEVEL PRESSURt (INCHES) AVERAGE AIR TEMPERATURE CFl WIND: Arrows flv with the wind Lenoth of 4Rrow oivE9 percent of total observations to SIXTEEN points OF THE COMPASS. BARBS SHOW FORCE ON BEAUFORT SCALE. FlOuRE IN CEHTCR OF CIRCLE GIVES PERCENTAQE OF lIOHT, VARIABLE WINDS 10 20 30 40 50 60 TO BO 90 100 SCAUE OF WINO PERCENTASES Figure 18. — Average sea level pressure (inches) and average air temperature (°F.), July. 92 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE JANUARY AVERAGE SEA LEVEL PRESSURE (INCHES) AVERAGE AIR TEMPERATURE (" F) OVERAGE WATER TEMPERATURE CF) WIND; Arrows flt with tke wind Length of arrow aivES percent of total observations to sixteen POINTS OF THE COMPASS BarBS SHOW FORCE ON BEAUFORT SCALE. FlQURE IN CENTER OF CIRCLE GIVES percentage of light, variable winds. to 20 SO 40 50 60 70 80 90 lOO Scale of Wind Percentages Figure 19. — Average sea level pressure (inches), average air temperature (°F.), and average water temperature (°F.) January. which have the greatest frequency — greater than 30 percent of all observations — in the summer and fall in a band extending from the Yucatan Channel northwestward across the Gulf. Altostratus and altocumulus are common the year-round, their average frequency being from 10 to 20 percent throughout the Gulf. In the summer and fall cumulonimbi are observed about 10 percent of the time in the western and northwestern regions. The period of lowest occurrence of rainfall over the open water is in the spring when less than 5 percent of the observations show rain according to the Atlas of Climatic Charts of the Oceans. The remainder of the year the frequency is 5 to 10 percent over most of the Gulf except for an area around the Yucatln Peninsula where fre- quencies drop below 5 percent in the winter and summer. A study by Kloster reported in the GULF OF MEXICO 93 Coast Pilot shows rain in from 13 to 21 percent of the hourly observations available for the entire year between 22^2° to 27 K° N. latitude and 80° to 90° W. longitude. Rainfall was most fre- quently reported in the mid afternoon — 19 percent versus 15 to 17 percent at other times of the day. The average depression of the wet bulb is 3° F. for the fall quarter — September, October, and November. During the remainder of the year it is 2° for the western Gulf and 3° for the eastern. In the summertime the air and the sea surface differ in temperature by less than 1°, the sea temperature being higher according to the Atlas of Climatic Charts of the Oceans. In the fall and winter differences increase, with the sea temperature being as much as 5° higher than the air temperature in the area just west of the Florida Peninsula. This leads to heating from below on the average and explains the high fre- quency of cumulus-type clouds over the Gulf. Monthly average sea surface and air temperatures are tabulated in the chapter on physical ocean- ography (p. 119). WEATHER OBSERVING STATIONS It is the purpose of this summary to discuss weather over the water in the Gulf. Since the observations here are sparse, some of the conclu- sions are drawn from observations made on the surrounding land areas. The weather observing stations in these areas are shown in figure 20. Those on the coast are listed in table 1. A par- ticularly interesting feature of the Gulf is that Table 1. — Weather observing stations along the coast of the Gulf of Mexico I Station number Location Station number Location 201 Key West, Fla. (NAS). 642 - Nautla, Verarcuz. 2n Tampa. Fla. (Interna- 692 Veracruz, Veracruz. tional Airport). 741 Coatzacoalcos, Veracruz. 214 Tallahassee, Fla. (Dale 743_ Villa Hermosa. Tabasco . Mabry Field). 746 Ciudad GbreRon, Ta- 220 Apalachieola, Fla. basco. 222 Pensacola. Fla. 749 Ciudad del Carmen, 223 Mobile, Ala. Campeche. 231 New Orleans, La. 695 Campeche, Campeche. 232 Burrwood, La. 643. Merida. Yucat4n. 240 Lake Charles, La. 648 Cozumel, Quintana Roo. 241 Port Arthur. Tex. 7.')1 Chctumal, Quintana Roo. 242 Qalveston, Tex. 601 Swan Island, West Indies. 243 Houston, Tex. 395 Vemam Field, Jamaica. 255 Vietoria, Tex. 397 Kingston, Jamaica. 251 Corpus Christi. Tex. 325 Havana, Havana (Casa 250 Brownsville, Tex. Blanca). 491 Ciudad Victoria, Tamau- 244 Cienfuepos, Santa Clara. lipas. 355 Camaguey, Camaguey. 349 Ciudad Camargo, Tam- 367. Guantanamo, Oriente. aulipas. 265 Antilla, Oriente. 639 Tuxpan, Veracruz. although it covers some 700,000 square miles, it is more than 90 percent surrounded by land. The rather complete coverage of weather information around its perimeter makes it an unusual natural laboratory in which to study changes in the character of air masses as they pass across the large body of water. TYPICAL UPPER AIR SOUNDINGS A comparison of the upper air soundings from Swan Island, south of the Gulf, with those of New Orleans and Brownsville, on the north and northwestern coasts, illustrates the modifying effects of the water surface. Monthly average radiosonde observations for a summer month and a winter month at each of these stations are shown in figure 21. It will be noted that the an- nual change in structure at Swan Island, which is almost completely controlled by oceanic factors, is very small, the most noticeable change being the higher relative humidities in the summer. At Brownsville and New Orleans the sea surface is cooler in winter, but, also, the continental influence tends to make winter temperatures definitely lower than those in summer. A rather complete discussion of the tropical Gulf air mass is given by Willett (1943). He states that the uniformity of the water tempera- ture in the source regions of tropical maritime air masses has proved to be of more importance in fixing the properties of the masses at all levels than has the previous life history of the individual air masses. Evidence is given demonstrating that the structure of the lower stratum of the air mass results from the turbulent mixing of saturated air. The air masses are characterized by marked potential instability, implying that all convective or mechanical turbulence up to at least 5 kilo- meters elevation must effect an upward transport of latent heat. The high relative humidities indicate that active convection extending above this level can be initiated by very little vertical displacement. Summer thunderstorms are more likely along the eastern part of the northern Gulf coast than along the western. There are higher relative humidities in the eastern area. Using a series of atmospheric temperature and moisture soundings to 45 feet elevation made at 4-hour intervals in March 1949 from an oil platform in the northwestern Gulf, Gerhardt 94 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 05 O o 3 O c '> y reference to the above standard stations. The Coast aiid Geodetic Survey also issues, in looseleaf form, descriptions and elevations of the tidal bench marks it has established in various places along the United States coast of the Gulf. These describe the location of each bench mark and its elevation above mean low water. For each 118 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE locality there is given, in addition, a table listing the highest and lowest tides observed or inferred, and the heights of mean high water, half tide level, and mean low water. At the present time, there are in operation by the Coast and Geodetic Survey 10 primary tide stations located as follows: in Florida, at Key West, St. Petersburg, Cedar Keys, and Pensacola; in Louisiana, at New Orleans, Bayou Rigaud, and Eugene Island; in Texas, at Galveston, Rockport, and Port Isabel. Most of these stations have been in operation for a number of years, at Galveston, for example, since 1909. For each of these sta- tions there are available, in the files of the Coast and Geodetic Survey at Washington, tabulations giving the hourly heights of the tide and the times and heights of high and low waters. There are also available summaries giving the monthly and yearly heights of high water, low water, and sea level. Tide stations have also been operated in recent years by the governments of Mexico and Cuba. LITERATURE CITED Cline, Isaac M. 1920. Relation of changes in storm tides on the coast of the Gulf of Mexico to the center and movement of hurricanes. Monthly Weather Review, March, pp. 127-146. Courtier, A. 1938. Marees. Service Hydrographique de la Marine, Paris, p. 149. Grace, S. F. 1932. The principal constituent of the tidal motion in the Gulf of Mexico. Monthly Notices Roy. A.str. Soc. Geophysic. Sup., May, pp. 70-83. Mar.mer, H. a. 1949. Sea level changes along the coasts of the United States in recent years. Trans. Am. Geophys. U., 30 (2): 201-204. Schureman, Paul 1940. Manual of harmonic analysis and predictions of tides. Coast and Geodetic Survey Spec. Pub. 98, rev. ed. U. S. Coast and Geodetic Survey. 1952. Manual of harmonic constant reductions. Sp. Pub. 260. Van Der Stok, J. P. 1897. Wind, weather, currents, tides and tidal streams in the East Indian Archipelago. Batavia. PHYSICAL OCEANOGRAPHY OF THE GULF OF MEXICO By Dale F. Leipper, Agricultural and Mechanical College of Texas Oceanography may be defined as the study of the oceans in all their aspects, including the interrelationships betweea the seas and their boundaries — the atmosphere, the shoreline, and the sea bottom. Physical oceanography consists of the analysis of the physical properties of sea water, the study of motions in the oceans such as those associated with ocean waves, tides, and winds, and examinations of the various mecha- nisms for the transfer and interchange of energy. The nature of physical oceanography differs from that of the other aspects of the subject in that certain mvestigations may be conducted somewhat independently. The other generally recognized aspects of oceanography are the bio- logical, the chemical, the geological, and the meteor- ological. Investigations in these are usually dependent upon physical oceanography and upon each other. It is desirable that work in the physical aspect be planned jointly with that in the other aspects in order that maximum utilization may be made of results which are obtained. The physical oceanograplier must pay particular attention to the problems in the other branches of the work since one of the primary objectives of his own researches is the development of information needed for the solution of some of these problems. There are many unique opportunities in the study of physical oceanography in the Gulf of Mexico. There is an offshore oil industry facing many problems related to construction and opera- tion in the shallow waters over the wide conti- nental shelf, there is a huge chemical industry which has an output depending heavily upon the varying longshore currents which alter the salt content of the water at the position where it is taken into the plants, and there are many characteristic weather features such as hurricanes. ' Contribution from the Department of Oceanography of the Agricultural and Mechanical College of Texas, Oceanographic Series No. 16; based in part on investigations conducted for the Texas A. and M. Research Founda- tion, through the sponsorship of the U. S. Navy Office of Naval Research. squalls, and fog which result from effects of the oceans upon the atmosphere. Further, the large oyster and shrimp fisheries are markedly affected by currents, turbulence and the physical charac- teristics of the sea water. Also, in reduction of beach contamination, prevention of beach erosion, reduction of dredging costs in marine channels, increasing the efficiency of marine transportation, development of recreational areas on the beaches, and in providing oceanographic information critical to the defense of our coastline, physical oceanog- raphy plays a most important role in the Gulf of Mexico. The Gulf, being nearly enclosed, provides a model ocean in which much may be learned about processes operating in the larger oceans which are not so readily adaptable to comprehensive and systematic analysis. The presence of fixed plat- forms far from shore may make it possible for the first time to make such determinations as that of the effect of the wind in changing the slope of the sea surface in the open sea. Such information is needed for further development of the theories of wind stress upon the sea surface and for the more complete understanding of the manner in which the winds drive the ocean currents and set up ocean waves. Despite the need for physical information in the Gulf, relatively little has as yet been done to survey the region systematically and to provide information in a form which is generally available. Recently there have been increased efforts in this direction, and within the near future it may be expected that knowledge of this highly important oceanic region will be greatly increased. OCEAN CURRENTS The primary problem in the physical ocean- ography of any region is the determination of the ocean cuiTents. In the Gulf of Mexico it is par- ticularly difficult. To provide a background for a discussion of this problem it is well to consider 119 120 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE briefly the general nature of the currents which may be expected in such a region. The general nature of currents in the Gulf of Mexico Sverdrup (1942) ^ lists three different groups of currents each of which is represented in the Gulf of Mexico. These are: (1) currents that are related to the distribu- tion of density in the sea, (2) currents that are caused directly by the stress that the wind exerts on the sea surface, and i'.i) tidal currents and currents associated , with internal waves. Tidal currents ' are caused by the tide-producing forces. These forces result from differences between the constant centrifugal force which acts on any particle on the earth and the varying gravitational attractions between the earth, the moon, and the sun. These attractions are pro- portional to the masses of the bodies and inversely proportional to the squares of the distances between them. Because of its very short dis- tance from the earth the attraction of the moon is large. The sun, on the other hand, although it is at a much greater distance from the earth, is so large that a tide-producing force results which is as much as 46 percent of that of the moon. The direct result of tide-producing forces acting upon the rotating earth is to raise and lower peri- odically the level of the ocean's surface, i. e., to create tides. Water which is required to raise sea level at a particular location must be furnished by horizontal movements within the ocean. These are the tidal currents. Since the sun and moon change their position with respect to a given part of the earth's surface in a periodic fashion, the tides and tidal currents are periodic. Because the rotation of the earth affects movements of water the tidal currents do not oscillate back and forth on a straight Ime bu^ rotate. In the Northern Hemisphere this rotation usually is in a clockwise direction except where modified by other factors. At times, interference i)et\veen tidal waves or the influence of other forces is such that the rotation may be counterclockwise. Along the Gulf coast there are many bays and lagoons which have relatively restricted outlets to ' References are listed ;it the end of the chapter. 3 Tides in the (Julf of Mexico are discussed separately in the article by H. A. Marmer, pp. 101-118. the sea. If the water level in these bays is to be raised by tidal action, all of the water required for the change in level must flow into the bay through these restricted channels. Therefore, the tidal currents in such channels may be quite large, particularly at certain stages of the tide. The great width of the shallow continental shelf along the Gulf coast results in tidal current veloc- ities which are relatively high considering the small range of tide. This is because the change of water level of this large area over the shelf must be brought about by flow across the shallow shelf. Since the depth of the moving water is small, its velocity must be relatively great to provide the volume needed for change in sea level. The high velocities and the changing di- rection and speed of these tidal currents may lead to considerable turbulence and stirring in certain localities. Oscillating currents related to internal waves may be important in this region, but little infor- mation now is available on this subject. Currents caused by tiie stress of the wind upon the sea surface are particularly important on the Gulf coast. The most widely known phenom- enon which results from the action of such cur- rents is the storm tide or general rise in water level which precedes winds of hurricane velocities. Storm tides are discussed by Cline (1920) and Tannehill (1927). Some of their results are sum- marized in the chapter on meteorological phe- nomena. Wlien a wind starts to blow over the ocean it exerts a frictional force or drag upon the sea surface. If the wind persists the surface layers of the water start to move and they in turn act upon the deeper layers and set these in motion also. The two forces which are involved in setting up such cm-rents are the frictional force, and the Coriolis force which is the apparent force due to the rotation of the earth. If the wind blows long enough for a state of equilibrium to be reached, the surface waters away from tlie influence of the coast will be moving in a direction approximately 45° to the riglit of the wind direction in the North- ern Hemisphere. A north wind sets up a surface current toward the southwest. The surface veloc- ities may reach 1 to 2 percent of the wind velocity. Currents at greater deptlis will flow at greater angles to the wind and at speeds which decrease with depth. GULF OF MEXICO 121 Fku're 34. — Surface ocean currents in the Gulf of Mexico in June. Conclusions concerning currents sot up by the wind are mostly based upon theoretical consider- ations. A few observations have been made in landlocked bays to show the piling up of water by the wind. However, in the open ocean no sys- tematic data are available. The drilling plat- forms off the Gulf coast permit the accumulation of data which will make possible a practical analysis". The ciuTents related to the distribution of density are the major semipermanent currents of the oceans. Little is known about these currents in the Gulf of Mexico. The chief source of infor- mation is the pilot charts of the United States Navy Hydrographic Office (figs. 34 and 35) . These are based upon the navigation reconis of the ships sailing in the Gulf over many jears. 'i'hev do indicate the general drift in various regions, but the individual observations upon which they are based are subject to many errors. For example. the deviation of a ship from its course may be caused by the wind rather than by the current. Also, it is difficult to determine positions at sea accurately. A survey of the pilot charts for the Gulf indicates that these may not describe all of the cm-rents present. They show waters flowing into the western part of the area at all latitudes but no water flowing out. This situation cannot exist unless theic is a submarine return current of equal nuignitude,»which seems unlikely. In the deep waters, direct observation of current velocities has been almost impossible until recently because of difficulty in anchoring vessels. Ac- cordingly, few such observations have been made. Instead, oceanographers have developed a method based upon principles of [ihysics. By use of this method the ocean currents present may be inferred fnun the (listril)ution of density as deter- mined l)y relatively simple observations of tem- perature, salinity, and pressure. Two forces again 122 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 94° 92* 90* 88° 86° 84° 8 2° Figure 35. — Surface ocean currents in the Gulf of Mexico in December. 80° 78° are involved, one of these being the CorioHs force and the other the "pressure force" which is a force that depends upon the water density distribution in the earth's gravitational field. The pressure force tends to make water flow from a region of high pressure toward a region of low pressure just as water poured into less dense oil will flow outward from the point at which it is poured. When the movement related to the pressure gradient has begun, the Coriolis force acts toward the right of the movement in the Northern Hemisphere and the resulting equili- brium between the two forces is associated with a steady current flowing almost perpendicular to a line connecting the regions of high pressure and low pressure. This flow is such that in the Northern Hemisphere the more dense water is on the left of a person standing with his back to the current and the less dense water is on his right. Since temperature is one of the major factors influencing density, it may be inferred that the cold water is on the observer's left and the warm is on his right when he is standing as described above with relation to the current. Thus, he can tell something about the currents if he knows the distribution of temperature, or he can tell something about the temperature if he knows the distribution of currents. There are a number of difficulties which arise in applying the current computation method. These occur partly because the basic assumptions under- lying the theory are not always fulfilled. How- ever, despite these difficulties the method has been found to be the one which provides the most infoimation for a reasonable amount of work. It is not known how accurately the Gulf currents in deep water may be determined by this method, but there is reason to believe it to be the most GULF OF MEXICO 123 accurate of the methods now in use. Used in conjunction witli the geomagnetic electrokineto- graph, it probably provides the best complete picture of the current patterns in the open Gulf. Determination of the flow over the broad, shallow continental shelf remains a diflicult problem. vSome processes by which the distribution of density is caused to change are evaporation, conduction, and the movement of masses of water by the winds. Since the total transport of water due to the winds in this hemisphere is toward the right of the wind, and since this trans- port consists of waters in the surface layers which are warm and of low density, the low density waters are piled up at the right of the wind flow, which is in the center of anticyclones, regions of good clear weather. The warm waters are removed from the low pressure storm areas at the left by the wind action. These movements are called the wind-driven currents. Their primary effect is to pile up water of small density in areas of anticj'clonic winds and to leave waters of greater density in areas of cyclonic winds. This leads to a secondary effect, namely, the mainte- nance of a different ocean current related to this distribution of density. Since such currents flow nearly perpendicular to a line connecting the regions having the different water densities, the associated currents form a pattern quite similar to the pattern of the winds. This may readily be recognized on charts showing the distribution of ocean currents with prevailing winds super- imposed. Investigations of ocean currents in the Gulf of Mexico There is probably no part of the oceans of the world of comparable size to the Gulf of Mexico where there is such a wide difference of opinion concerning the specific current regime. This difference is brought out by Sweitzer (1898). He quotes Isaac Vassius who, writing about the year 1663, tells how the currents through the Yucatan Channel "turn obliquely" and pass through the Straits of Florida. The issue of the Encyclopedia Britannica available in 1898 states that "a portion of it (the current — DFL) passes directly to the northeast along the shore of Cuba; but by far the larger part sweeps around the Gulf." Sweitzer himself concludes that, at times "the channel of Yucatan pours its waters into the Gulf so that they spread out in all directions moving on its center," while at other times the currents flow "in a northeasterly direction around the extreme west coast of Cuba." These last results were based upon studies of the distribution of specific gravity of the surface waters. United States Coast and Geodetic Survey, Lindenkohl (1896), and upon modification of currents by the prevailing winds. Sweitzer also reported considerable agitation of the waters covering an area of about 100 square miles occurring off the coast of Texas about 40 miles south and 20 miles east of Aransas Pass which could only be accounted for by the meeting of two opposing currents. Other evidence of converging currents has since been found, and this area has become known as the graveyard of ships. Measurements made in the years 1885 to 1889 by the United States Coast and Geodetic Survey vessel Blake, commanded by Pillsbury (1889), determined the currents in the Straits of Florida. Since the ship was anchored, direct current ob- servations could be compared to computed values, and the comparison provided one of the best examples illustrating the validity of the method for computing relative currents which is now so widely used. Agassiz (1888) published temperature and salinity data collected by the Blake in 1878. These data, together with others collected by the Bache, Bigelow (1917), were used by Wvist to compute the transport of the water through the Florida Straits as 26 million m^second. As- sociated with this transport is a water level difference of 19 cm. between the southeastern Gulf and the Atlantic at St. Augustine, Florida, which is discussed by Montgomery (1938). A theory of piling up water in the "Bay of Mexico" was advocated by Benjamin Franklin about 1770. In 1922, the Dana made some observations in the Yucatan Channel and in the Florida Straits, as shown in figure 36. These observations, as well as those of the Mabel Taylor in 1932, were sum- marized by Parr (1935) who concluded that "evidence thus obtained from the Gulf itself, although directly opposed to some of his premises, nevertheless serves to confirm the theory already advanced by Nielsen on the basis of observations in the Straits alone, that the so-called Gulf Stream only takes the shortest possible path from its entrance through the Yucatan Channel to its 124 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE GULF OF MEXICO 125 exit through the Straits of Florida, without de- viating on the way, or dilTusing any to itself significant amount into the Gulf of Mexico |)roi)er, or receiving any predominant contribution from the Gulf in return." This statement on the one hand and the current pattern shown in figures 34 and 35 on the other hand summarize the present divergence of opinion. The Mahtl Taylor cruise was made without unprotected thermometers or other reliable means of determining depth of observations. Parr cautions that particularly in the Yucatan Channel and Florida Straits there is sufficient uncertainty of the depths of the Mabd Taylor operations "to make it seem inadvisable to subject them to a form of analysis and comparison in which depth is an essential consideration." Similarly, the Atlantis cruise of 1934, Parr (1937), lacks sub- surface data since the hydrographic cable was lost early in the survey. Thus, the oceanographic data available to Parr were meager. Dietrich (1939) reviewed the currents of the Gulf, and his conclusions, although based upon essentially the same data as used by Parr, show considerably more influence by the Gulf Stream upon the general circulation in the Gulf. He discussed the sill depths showing that the Gulf circulation cannot affect the deep water circulation of the Atlantic below about 800 meters. However, the Florida current, which is shallower than this, has considerable effect. In 1947 the Atlantis conducted a survey of the northwestern Gulf making 27 hydrographic sta- tions (fig. 36) and 473 bathythermograph observa- tions of temperature. These data have been analyzed by Fred B. Phleger (1951), now of the Scripps Institution of Oceanography of the Uni- versity of California, and have been published by the Geological Society of America. The first cruises of the Alaska, oceanographic research vessel of the Fish and Wildlife Service operating on a survey of the Gulf of Mexico with the cooperation of the Department of Oceanog- raphy of Te.xas Agricultural and Mechanical College and the United States Navy, Office of Naval Research, were completed in October 1951 (fig. 37). These provide the first complete coverage of the Gulf with information needed to compute the deep water currents. The data from these cruises have been distributed and prelimary anal- yses indicate that they support the main fea- tures of llie current pattern shown in figure 34, A i)rief description of the currents of the Gulf of Mexico is provided in the United States Coast Pilot (1949): Under noriual coiiditioii.s, at all seasons of the year, the great volume of water passing northward through Yucatdn Channel into the Gulf of Mexico, spreads out in various directions. Surface flows set westward across Cainpeche Bank, the (iulf of Canipeche, and the Sigsbee Deep; northwestward toward tlalveston and Port Arthur; north-northwestward toward the Mississippi Passes; and eastward into the Straits of Florida. A straight line drawn from Buenavista Key, Western Cuba, to the Mississippi Pas.ses forms an approximate boundary between movements having different directions. West of this line the drift is generally northward or west- ward, while east of it the drift is eastward or southeast- ward toward the Straits of Florida. There are northward flows along the west side of the Gulf between Tampico and Corpus Christi in the vicinity of the 100-fathom and 1,000-fathom curves, north of the Sigsbee Deep between the 2,000-fathom and the 100- fathom curves, and along the west coast of Florida. In general, the surface circulation is the same at all seasons. There is, however, some .seasonal change in velocity, the flow being generally stronger in spring and summer than in the autumn and winter. The current near the Florida Keys is variable and uncertain. This description is apparently taken from the Pilot Chart series of the Hydrographic Office (H. O. No. 3500, issued monthly). Another series, H. O. No. 10,690, 1 to 12, Current Charts of the Central American Waters, give resultant direction and velocity for each 1° quadrangle of latitude and longitude. This series has been used by Smith, et al. (1951), to show zones where seasonal convergence or divergence occur. Many of the references cited above contain bibliographies pertinent to the Gulf of xMexico. Also, Geyer (1950) lists many useful works. In summary, the currents of the Gulf of Mexico and their variations are not specifically known. Studies completed in the past indicate some unusual and interesting features and provide incentive and justification for continued intensive investigation. SEA SURFACE TEMPERATURES A large number of sea surface temperature ob- servations have been collected at shore stations. Some of these data from locations shown in figure 126 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE o OS - a ■0 c 03 fa ad o C a O GULF OF MEXICO 127 128 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE be 3 J3 be GULF OF MEXICO 129 130 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 38 have been made available through the Fish and Wildlife Service of the United States Department of the Interior and are on file in the Department of Oceanography at Texas Agricultural and Me- chanical College where a file-report has been pre- pared. The key in figure 38 shows the period of years in which observations were made and sent in from each station. The study of these shore station data is continuing, and references to addi- tional information of this kind are sought. It is hoped that they may provide a clue to general changes which are occurring offshore where ob- servations are not so readily obtainable. Studies of sea surface temperatures in the Gulf of Mexico have been based on some 200,000 ob- servations taken on ships in this area over a period of more than 50 years. The majority of these observations were made with the instruments carried as a regular part of each ship's equipment. Due to the possibility of error in the individual thermometers and to errors in reading, the results must be interpreted with care. However, with such a large number of observations the non- systematic errors tend to cancel each other, with resulting averages being not far from the true mean. The Weather Bureau of the United States De- partment of Commei'ce has computed average sea surface temperatures in the Gulf of Mexico using the above observations. Table 1 shows the aver- Table I. — Monthly average sea surface and air temperatures in the Gulf of Mexico (in degrees Fahrenheit) [Figures in italics are averages of dry bulb thermometer readings observed as a rule on the ship's bridge. Figures in roman are mean sea surface temperatures, obtained mainly from bucket sampling] Area 100-95 W30-2SN 95-90W 30-25N 90-85W 30-25N 85-80W 30-25N 100-95W 25-20N 95-90W 25-20N 90-85W 25-20N 85-80W 25-20N January 66.8 66.9 67.5 73. S 75.6 80.3 83.1 8S.9 81.8 77.2 77. « 69. S 67.7 68.3 68.8 72.6 76.3 80.6 82.6 83.3 83.3 80.2 76.3 70.7 63. 5 63.7 66.3 71.1 75.9 80. S 82.5 83.0 81.5 76. i 70. i 66. i 67.9 67.3 68.5 71.6 76.0 80.6 83.1 S.3.9 82.8 79.4 74.7 70.7 68. 1 68.3 69.8 73. S 77.3 80.8 82. i 82.9 81.8 77.8 72.8 69.8 72.5 72.1 72.6 74.6 77.7 81.0 82.9 83.7 82.9 80.3 76.7 74.2 69.3 69.2 70.9 710 77.5 80.6 82.3 82.6 81.9 78.5 710 70.9 73.2 72 7 73.2 75.2 77.9 80.8 82.6 83.4 82.9 80.7 77.5 75.0 70.7 70. i 72.7 75.1, 78.6 80.8 81.7 82.5 81.6 79.1 76.1 71.7 73.0 72 6 73.3 75.4 78.5 81.1 82.5 83.3 83.1 81.3 77.9 74.5 72.5 72.7 73.9 76.2 78.8 81.0 82.1 82. i 82.1 80.2 76.5 73.8 74.3 73.9 74.6 76.1 78.6 81.2 82.4 83.2 83.2 81.6 78.5 75.9 711 71 1 76. S 77.1 7.9. y, 81. i 82.2 82.5 82. 2 80.1 76.9 75.2 76.3 76.0 76.4 77.7 79.5 81.6 82.6 83.2 83, 1 81.8 79.5 77.7 71.9 7S.1 73.3 76.9 78.7 81.3 82.7 &10 82.3 79.6 75.8 7S. 3 . 75.0 74.7 75.3 April 76.8 May _. 79.0 June 81.5 July - 83.0 August 83.8 83.4 October 81.5 78.8 76.5 Note.— From Charts 115-126, Atlas of Climatic Charts of the Oceans, U. S. Department of Commerce, Weather Bureau. age sea surface and air temperatures for the 12 months of the year, the Gulf being divided into eight 5° quadrangles. This information was taken from charts 115 to 126 of the Weather Bureau's Atlas of Climatic Charts of the Oceans. Probably the most recently prepared charts showing average sea surface temperatures in the Gulf are those of Fuglister (1947). Isotherms reproduced from his work for the winter month of February and the summer month of August are shown in figures 39 and 40. The main feature of the average winter pattern is a gradual drop from approximately 75° F. in the south to 65° F. in the north in all parts of the Gulf, the gradient being larger in the east portion. In the summer- time the average temperatures are very nearly uniform at 84° F. throughout the region. Cruises of the Alaska indicate that considerable deviation from these average isotherms may occur at cer- tain times. The annual range of normal sea surface tem- perature varies from 15° to 20° F. in the northern portion of the Gulf, while m the central and southern portions the range is about 10° F. February is normally the coolest month of the year, though January is the coolest month for that portion of the Gulf adjacent to Texas and Mexico. Except for a few scattered areas, August is normally the warmest month of the year. In regard to diurnal variation of surface tem- perature in the Gulf, a study by Stommel and Woodcock (1951) presents some data and dis- cusses various methods of computation. It makes recommendations for future investigation of this problem. According to Storey (Gunter 1947), there were nine freezes along the west coast of Florida be- tween 1886 and 1936 which killed fishes in large numbers. Intense cold spells, sufficiently severe to kill large numbers of fishes, occurred along the Texas coast on an average of one every 14 years between 1856 and 1940, with less damaging spells coming at shorter intervals. Similar data for other parts of the Gulf coast are not available. GULF OF MEXICO 131 Slocum (1934-36) lias made a comparative study of sea surface temperatures for various regions of tlie Gulf in different years. This study is based on temperature observations taken from 1912 to 1933. The year-to-year changes are summarized in table 2 for the regions shown by Table 2. — Some variatiotis of mean annual sea surface temperatures for 1912-33 ' in various regions of the Gulf {° F.) [After SlocumJ Variation High Dif Mean Dif Low High-Low Dif.. (1) 25-26° N. 84-86° W. 79.5 78.4 76.8 1.1 1.6 2.7 (2) 27-29° N. 90-93° W. 77.0 75.5 73.9 1.5 1.6 3.1 (3) 26-28° N. 86-89° W. 78.7 77.8 76.6 0.9 1.2 2.1 (4) 21-25° N. 90-94° W. 79.7 78.5 77.6 1.2 0.9 2.1 (5) 23-24° N. 82-84° W. 1.0 2.1 3.1 (6) 21-22° N., 8.')-87° \V. 22-23° N.. 84-87° W. 81.1 80.3 79.3 0.8 1.0 1.8 I The number of observations varies from year to year. Few observations were made in 1917-19. In other years, the number ranged from 100 to over a thousand in each region. Locations are shown in figure 41. encircled numbers in figure 41. The mean tem- perature for each year has been computed. It is of interest to note that in one case the minimum mean yearly temperature for a given region for this period of years differed from the overall mean temperature for the region by 2.1° F. Moreover, the maximum and minimum mean yearly tem- peratures differ by 3.1° F. m two localities. For one of these extreme examples, in the region 27-29° N., 90-93° W., the lowest mean yearly temperature recorded was for the year 1915 which showed a mean temperature of 73.9° F. In 1922 and 1927, the highest mean temperatures were recorded here, being 77.0° F. For the other example, the low was 77.8° F., the high 80.9° F. Siocum's stud}' also iacluded consideration of the means for the different months of the year. SEA TEMPERATURE VARIATIONS WITH DEPTH The sea temperatures obtained by the Mabel Taylor below the surface have been -published by Parr (1935). Although the depths of these obser- vations are not known accurately, they do give considerable information about vertical tempera- ture distribution. An average temperature-salinity correlation in the Gulf of Mexico proper as woi'ked out by Parr for the months February-April is given as table 3. In the early 1940's the United States Navy developed the bathythermograph for making observations of sea temperature continuously from the surface to depths as great as 900 feet. To date, some 10,000 observations or bathy thermo- grams have been made in the Gulf. Copies of 259534 O— 54 10 these are now filed at the Woods Hole Oceano- graphic Institution where they are processed and in the Department of Oceanographv at Texas Agricultural and Mechanical College. Their dis- tribution b}' 1° quadrangles is shown in figure 42. Table 3. — An average temperature-salinity correlation for the Gulf of Mexico proper lAfter Parr] Average tem- Average Weighted aver- perature salinity age depth °C. °/» m. 24.74 36.19 5 23.06 36.06 15 21.03 36.14 58 19.25 36.28 94 17.09 36.22 125 14.85 35.95 192 13.00 35.68 237 10.89 35.35 321 9.60 35.16 380 8.57 35.04 432 7.42 34.93 562 6.39 34.88 647 Two bathy thermograms, one for summer and the other for winter, were chosen from each of four parts of the Gulf within the 1 ,000-fathom line. These locations are indicated by encircled crosses in figure 41. The bathythermograms were chosen as being typical after considering range of tempera- ture variation, general shape of temperature-depth curve, depth of thermoclinc, and other features. Unfortunately, due to the paucity of observations it was not possible at any one of the four positions to obtain "typical" summer and winter bathy- thermograms from the same year. However, by plotting a typical summer and a typical winter bathy thermogram for each position on the same coordinates it was possible to show in a general 132 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE ■a C9 e T3 3 01 & tn C o GULF OF MEXICO 133 134 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 24n47 xrF) -^ 25*26H93*44'W 75m 43 25'04'Na3*59'W bo a z 18 I 47 rrF)— 27*05'N,e9'40'W 27 68 70 72 74 ' 76 78 80 82 8 71014 •|8'n| D(H.) 40 80 120 160 200 • /■ .r 7 .iwu- / i / ' 7- / -a. J .'^ J 4^ f / / I y / / / 400 440 480 l|*43'W II I 45 l2Sm43 TCF)^ 24"0I'N,89*I7'W 24*0I'N,89*48'W P(,,) 70 7;2 74 ^ Ve 77 QO 8? 84^ ^6 , ^8 i" 40 T( F)— 24°08'N,85°59'W — ~ -- 76 ^- 25 Vm 45 24°I3'N,85°56'W 8,4 ^ 86 as Figure 43. — Typical summer and winter bathythermograms from different areas in the Gulf of Mexico. GULF OF MEXICO 135 way the seasonal difForences. These curves are presented in fio;ure 43 which gives the date and position of each observation. Typical curves properly selected are believed more representative of conditions than average ones, since certain characteristic features of temperature structure may be lost in the process of averaging. A report by Adams and Sorgnit (1951) gives similar infor- mation for each 1° quadrangle of the Gulf where data were available. It also shows the contours of the bottom of the mixed or isothermal layer in summer and winter insofar as can be determined. SALINITY Parr (1935) presents a chart of the distribution of average salinities in the upper 50 meters of the Gulf of Mexico. It shows the values to be typ- ically 36.00 parts per thousand over the entire central region. Water from the Mississippi River reaches to depths of 50 meters and extends beyond Mabel Taylor station 1106 (fig. 36), a distance of 150 miles, keeping salinities below 36.00 parts per thousand. Near stations 1201 and 1202 the river extends its influence on salinity only about 85 miles seaward. From the Yucatdn Channel a subsurface in- trusion of water having salinity over 36.50 parts per thousand extends north and bends westward to the central part of the Gulf. From February to April this tongue underwent a marked shift westward in position of some 120 miles according to the Mabel Taylor data. Above 50 meters waters of salinity greater than 36.25 parts per thousand are found over both the wide Campeche and Florida Banks indicating possible upwelling of the subsurface intrusion. Average variation of salinity with depth is shown in table 3. TEMPERATURE-SALINITY RELATIONSHIPS An average temperature-salinity relationship for the Gulf proper was shown in table 3. A single station tj'pical of what Parr defined as the Gulf Complex is Mabel Taylor station 705 (fig. 36). Another which he calls typical of the Caribbean Complex, divided from the Gulf Complex by a line extending from the northeast corner of Yuca- tan Bank to the southwest corner of the Florida Bank, is station 701 (fig. 36). Data for these sta- tions are listed in table 4. The primary difference l)etween these two distributions is that at temper- atures above 18° C. the Gulf Complex station has markedly lower salinities, being below 36.32 parts per thousand, while the Caribbean station has values as high as 36.73 parts per thousand. The T-S curves in the Yucatdn Channel do not seem to vary significantly from year to year, but those in the Straits of Florida are not so stable, particularly at temperatures above 20° C. Cruises in different years in the Straits have shown wide variations in the extent of Gulf water found in the upper 200 meters. Table 4. — Typical temperature and salinity data [After Parr) Qulf Complex Station 70\ Feb. 18, 27°42' N., 86'00' W. Caribbean Complex Station 701, Feb. 16, 23°28' N., 85°37' W. Depth Salinity Tempera- ture Depth Salinity Tempera- ture m. 30 100 150 200 300 500 700 900 1,200 1,500 2,000 2,500 3,000 °/oo 35.52 3B. 15 36.32 36.21 3.5.96 35.52 35.08 34.87 34.92 34.95 34.97 34.97 34.97 34.97 °C. 23.75 23.15 18.59 16.58 14.94 12, .■!0 7.88 5.91 4.94 4.21 4.21 4.16 4.22 4.24 m. 100 200 300 400 600 800 1,000 7oo 36.18 36. 32 36.73 36.44 35,94 35.08 34.86 °C. 25.34 25.28 21.88 18.21 14.96 9.12 6.86 5.15 Parr (1935) believes that since — The presence of Gulf waters in the Straits of Florida is ... identified with the location in which a counter- current running in the opposite direction of the Caribbean- Florida Current flow is usually indicated on the hydro- graphic charts. ... it seems reasonable to draw the tentative conclusion "the water masses of the Gulf of Me.xico proper should be considered part of the coastal water system of the North and Central American Atlantic seaboard and not as part of the oceanic- circulation system of the Caribbean and Florida Currents." Considerable further evidence is required to fully support this tentative conclusion. Below 800-1,200 meters depth observations of the Mabel Taylor showed hydrographic conditions in the Gulf so extremely uniform that it was not considered advisable to attempt to prepare verti- cal profiles for the deep layers. More accurate depth determinations on subsequent investigations may bring out significant variations at these depths. 136 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE OCEAN WIND WAVES AND SWELL A basic and easily obtainable reference for climatic data on waves in the Gulf is the Atlas of Sea and Swell Charts of the United States Navy Hydrographic Office (1943-50), Miscellaneous Publication No. 10,712, A through D. Certain uses of these data are discussed by Fleming and Bates (1951). Information concerning wave heights in some regions on certain specific days may be obtained by referring to wind data available through the United States Weather Bureau and applying a method of calculation described in United States Navy Hydrograpliic Office Publication No. 604, Techniques for Forecasting Wind Waves and Swell. The problem of wave action on structures is discussed by .\Iunk (1947). Considerable addi- tional research will be i-equired before knowledge of wave forces in the Gulf is complete. Such work has been underway at the University of California (La Jolla and Berkeley) and is being initiated at Texas Agricultural and .Mechanical College. SHALLOW WATER OCEANOGRAPHY Much of the marine interest on the Gulf coast tends to center on the shallow waters. There are many bays, lagoons, and inlets of gi'eat importance to fishing, navigation, recreation, oil recovery, and other activities. Each of these pri'sents its owTi peculiar problems, and extensive investiga- tions have been carried on in many of them. A recent publication indicating the nature of this work is that of Collier and Hfl Gulf Stream (16 to 20 miles olTshore) .067- ,047 East of Loggerhead Key ' .189-, 150 West end of Garden Key Cliannel 227- . 174 Clarke (1938) calculated the extinction coeffi- cients for a series of stations east of the Mississippi Delta. These values are indicated in table 1 as series 439 through 442. For security reasons, Hulburt's paper (1940) on transparency and visibility of submerged objects in the Key West sector has been classified. Bumpus and Clarke (1947) have connected equal points of known "K" values on a chart which includes the Gulf of Mexico. It must be remembered that these lines are based on very few observations, and considerable interpolation was necessary. The Special Scientific Reports, Fisheries No. 8, by Butler (1949), and \o. 14, by Butler and Engle (1950), of the United States Department of the Interior contain turbidity indices for selected points of the Mississippi Sound and Lake Pont- chartrain. Turbidity is expressed as the per- centage-transmission of light through the sample. No correlations with extinction coefficient values or (('(i to many mcmhers of llie stnfTs (if tlif \Vu(icls H.ilc ()c'('!Uii)ity of Miami Marine Ijaboraton , in particular to Dean F. Binnpiis and II. ]\. Moore for placing: tiicir files at my disposal. LITERATURE CITED UiMiMs, 1 1 K., and (i.arkk, G. L. H)47. Hydrography of tlir western Atlantic; trans- parency of the coastal and oceanic waters of the western Atlantic. Woods Hole Oceanographic Inst. Tech. Hept. No. 10. Submitted to the Oceanog. Div.. Hydrog. Off., under Contract \o. N6onr-277 with OtT. Xav. Res., Dec. HM7. BlTLER, I'niLIP A. 1949. An investigation of oyster producing areas in Louisiana and Mississippi damaged by flood wat<'rs in 1945. U. S. Dept. Int., Fish and Wildlife Service, Spec. Sci. Kept.: Fisheries 8: 1-29., App. I-VI. and E.NGLE, James H. 1950. The 1950 opening of the Bonnet Carre Spillway: its effect on oysters. V. S. Depl. Int., Fish and Wildlife Service, Spec. Sci. He[)f.: Fisheries 14: l-IO. ('l,.\HKi:, CiE<)R(;K I.. 19.S8. I.ighl penelration in the Caribbean Sea and in the Culf of .Me.\ico. Jonr. Mar. Hes. 1 (2): 85-93. 1941. Observations on transparency in the southwestern .section of the North Atlantic Ocean, .lour. .Mar. Res. 4 (.{): 221 2S0. HtLBERT, P. (). 1940. Tests at .s.-a in February 1940, in th" Key West area of visibility of submarines and transparency of navigable waters. Nav. Hes. I.al) Kept. NO. H-1598. (Classified.) Pooi,E, II. II., and Atkins. W , H. C. 1929. I'hoto-electric measurements of submarine il- lumination throughout the year. .lour. .Mar. Miol. Assn. I. K. Hi: 297-:i24. ScH.MIOT, .J. 1929, Introduction to the oceanographical reports in- cluding list of stations and hydrographical observa- tions. The Danish Dana i;x|)editions 1920-22 in the North .\tlaniic and (lulf of Panama, vol. 1, No. 1. T.WLOR, W .M. RaNUOI.I'H. 1928. The marine algae of Florida with special reference to the Dry Tortugas. Pap. Tortugas Lab., Carnegie lust. Washington 25: 1-219, M pis. DISTRIBUTION OF CHEMICAL CONSTITUENTS OF SEA WATER IN THE GULF OF MEXICO ' By ROBERT H. WILLIAMS, Marine Laboratory, University of Miami Earliest records of chemical analyses of Gulf of Mexico waters were published by biologists and biochemists who studied the sea water composi- tion as one ecological factor in the complex envi- ronment of the marine organisms with which they were concerned. Much of this early work was centered at the Carnegie Institution laboratory at the Dry Tortugas near the western end of the Florida Keys. First oceanographical studies of the chemistry of the water were confined to the system of currents flowing across the southeastern corner of the Gulf from the Yucatdn Channel to the Straits of Florida. Practically all analyses of offshore and subsurface waters of the Gulf were made in 1914, 1922, 1932, 1934-39, 1942, and since 1947. The chemical data are summarized here in order of the decreasing amount of published informa- tion: salinit}', oxygen, phosphorus, nitrate, nitrite, pH, alkalinity and carbon dioxide components, copper, and miscellaneous chemical constituents. SALINITY Salinity is defined as the total amount of dis- solved solid material in grams contained in 1 kilogram of sea water when all the carbonate has been converted to oxide, the bromine and iodine replaced by chlorine, and all organic matter com- pletely oxidized. In practice, it is calculated from the chlorinity which is determined by titra- tion with silver nitrate solution. Less accurate salinity values are calculated from densities determined with hydrometers. Both salinity and chlorinity are reported as parts per thousand by weight, using the symbol, "/co- in the shallow waters of the Dry Tortugas, in the years 1910 to 1913, Dole (1914) reported salinities ranging from 35.41°/oo to 36.11°/oo- Diurnal and tidal changes in salinity in the same ' Contribution No. 101, from the Marine Laboratory, University of Miami. area in 1919 indicated a wider range, 34.61 °/oo to 36.29°/oo (Wells 1922). In the bays along the coast of Texas the wide salinity variations cause recurring mass mortality of marine animals. This situation was reported by Johnson (1882), Rathbun (1895), and Higgins and Lord (1926). Results of detailed surveys of the salinity distribution in the Texas bays in 1926-27 were reported by Galtsoff (1931). Addi- tional studies of salinity along the Texas, Louisi- ana, and Mississippi coasts were published by Higgins (1931), Riley (1937), Lindner (1939, 1941), Gunter (1945, 1947, 1950), Wise, Winston, and Culli (1945), Price (1947), Geyer (1950), and Collier and Hedgpeth (1950). Alternating floods and droughts cause salinity changes from nearly fresh to 100°/oo, three times that of normal sea water. In connection with studies of the red tide along the west coast of Florida, salinity data were pub- lished by Galtsoff (1948), Gunter, WiUiams, Davis, and Smith (1948), and Ketchum and Keen (1948). In the open Gulf salinities ranged from 30.6°/oo to 37.0°/oo; in Estero Bay, 21.4°/oo; and near the mouth of the Caloosahatchee River, 12.2°/oo. In connection with plankton studies in 28 man- grove-bordered inland bodies of brackish water on the west and south coasts of Florida in 1947- 48, Davis and Williams (1950) reported salinities ranging from 0.6l7oo to 29.09°/oo. The present center of Florida's oyster industry, Apalachicola Bay in northwest Florida, was the subject of an 18-month survey of salinity (Ingle 1951; Ingle and Dawson 1951). Annual varia- tions ranged from fresh water to 42.5°/oo Daily, weekly, and tidal variations were considerable. Apparently the first published salinity records for offshore and subsurface Gulf of Mexico waters are those of Vaughan (1918) who reported salinity values for samples collected at five stations be- tween Havana and Key West from the surface to 143 144 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 1,700 meters by the United States Coast and Geodetic Survey steamer Bache in Marcii 1914. Salinities of two surface samples collected a little farther east in January and February 1919 were reported by Mayor (1922). Stations taken by the Danish research vessel Dana across the Hav'ana section in 1922 provided data for a salinity profile (Nielsen 1925; Schmidt 1929; Jacobsen 1929). Composition of two surface samples collected in July 1922 in the Gulf Stream south of the Dry Tortugas was reported by Lipman (1929). The Havana section was studied again in Feb- ruary 1932 on the Yale Oceanographic Expedition aboard the schooner Mabel Taylor (Parr 1935). Expeditions from the Woods Hole Oceanographic Institution aboard the research vessel Atlantis have made studies of the Havana section in March 1934 (Bulletin Hydrographique, 1935), February and April 1935 (Bulletin Hydrographique, 1936; Seiwell 1938), March 1938 (Montgomery 1941), and May 1939 (Riley 1939). The vertical distri- butions of salinities across the Havana sections in 1922, 1932, and 1934 were summarized in profiles by Parr (1935, pp. 42-44, 71). Below 100 meters the isohalines generally sloped downward toward the Cuban coast. In the middle of the Straits the salinity generally increased from 35.83°/oo at the surface to 36.68°/oo at 200 meters, then de- creased to a minimum of 34.87°/oo at 800 meters, and thereafter increased only slightly to 34.97°/oo at 1,600 meters. The next most thoroughly studied part of the Gulf of Mexico is the Yucatan Channel where the Caribbean Current enters the Gulf between west- ern Cuba and Mexico. This section was studied in 1922 from the Dana (Schmidt 1929; Jacobsen 1929), in February 1932 from the Mabel Taylor (Parr 1935), and from the Atlantis in May 1933 (Bulletin Hydrographique, 1934; Parr 1937; Rake- straw and Smith 1937) and March 1934 (Bulletin Hydrographique, 1935; Parr 1937). The vertical distributions of salinities across the Yucatan Channel in 1933 and 1934 were summarized in profiles by Parr (1937, pp. 42-43). Here, also, the isohalines generally sloped downward toward the Cuban coast. The vertical distribution of salinity was similar to that described above for the Havana section. Comparison of the average temperature-salinity correlation curves for the Yucatan Channel and the Havana section of the Straits of P'lorida led Parr (1935) to conclude'that the water mass entering the Straits of Florida is identical with that which passed through the Yucatan Channel except for a very small layer of "Gulf type" water at the surface on the left (Florida) side of the main current. Parr's (1935) report on the expedition of the Mabel Taylor, February to April 1932, included a map showing the locations of the 68 stations oc- cupied in the Gulf, complete temperature and salinity data, salinity profiles of 5 sections across the main parts of the Gulf, maps of salinity dis- tribution in upper 50 meters and at 200 meters, graphs of vertical distribution of salinity, and temperature-salinity correlation curves. The ex- pedition was not provided with unprotected re- versing thermometers and therefore had no means for accurate determination of the depths of observations. The highest salinities (above 36.25°/oo) in the upper 50 meters were found in the shallow waters off the west coast of Florida and the Campeche Bank. Most of the offshore water in this surface layer had salinities between 36.00°/oo and 36.25°/oo. Low salinities (below 33°/oo) were found along most of the northern regions of the Gulf, and very low (less than 24%©) salinities were found near the mouth of the Mississippi River and to the west from the delta region. At a typical station in the western Gulf (25°46' N., 92°3r W.) the salinity decreased slightly from 36.16°/oo at the surface to 36.12°/oo at 50 meters, then increased to the maximum of 36.31 °/oo at 100 meters, then decreased to the minimum of 34.87°/oo at 600 meters, then in- creased slightly to 34.92°/oo at 800 meters, below which it remained practically constant down to 3,000 meters. Dietrich (1939, p. 119) used the 1932 data from the Gulf of Mexico to prepare another map showing the distribution of the maximum salinities, regardless of depth. This showed a continuous layer of high salinity (above 36.7%o) water in most of the Caribbean Sea, the northern half of the Cayman Sea, and extending northward into the Guif to 26°0()' i\. and 89°20' W. The Atlantic occupied stations along several sections of the central and western Gulf in February to April 1935 (Bulletin Hydrograpliique, 1936). A map showing the locations of these stations was published by Vaughan (1937, p. 21). Vertical distribution of salinity at a typical station in April 1935 in the western Gulf (25°40' N., GULF OF MEXICO 145 94 °2:^' W.) was charted by Diotrich (1989, p. 117, fig. 33); it was similar to that describod above for the Mabel Taylor station about 100 miles farther east. The Atlantis occupied a series of nine stations in the northeast Gulf in March and .pril 1942 from which salinity data were publisi-ni (Bul- letin Hydrographique, 1950). The same vessel occupied a series of 24 stations in the north- western and central Gulf, January to March 1947 (Trask, Phleger. and Stetson, 1947).' The research vessel of the Fish and Wildlife Service laboratory at Sarasota, Florida, has occupied stations from Sarasota to Naples and to a distance of 120 miles off shore at appro.ximately monthly intervals since May 1949. Chemical analyses of the water were made for chlorinity, dissolved oxygen, inorganic phosphate, total phosphorus, nitrate, nitrite, and hydrogen ion concentration.^ The phosphorus data have been published (Graham, Amison, and Marvin, 1954). The other data will be published later. ^ The Fish and Wildlife Service research vessel Alaska began a series of occanographic cruises in the Gulf of Mexico in 1951, Salinities collected on these cruises are being determined at Texas Agricultural and Mechanical College. They shortly will be made available in a mimeographed form.* DISSOLVED OXYGEN The first available data on dissolved oxygen content of Gulf of Mexico water seem to be on the results of analyses of water collected at the Dry Tortugas and published by McClendon (1918), Oxygen determinations were reported when the Atlantis occupied stations across the Yucatan Channel in May 1933, March 1934, and February 1935; across the Havana section of the Florida Straits in March 1934, February and April 1935, August 1938, and May 1939; and in the main part of the Gulf in February to Apnl 1935, The oxy- gen and other data from most of these stations were published in the Bulletin Hydrographique ' Salinity data from tlifse stations were kindly supplied by Fred B. Phleger on August 15, 1950. They are also available from data cards on file at the Woods Hole Oceanographic Institution and will probably be published in the Bulletin Hydrographique. 3 Personal communication from L, A. Walford, December 5, 1950. ' Personal communication from Herbert W. Qraham, January 3, 1952. * Temperature-salinity relationships are discussed in the article of D. F. Leipper. Physical Oceanography of the Gulf of Mexico, in this book. pp. 119-135. in 1934, 1935, and 1936. A graph of the vertical distribution of dissolved oxygen in the center of the Yucatan Channel in 1933 was given by Rake- straw and Smith (1937, p. 9), and a map showing the locations of the stations was published by Vaughan (1937, pi. 11). Seiwell summarized the oxygen data from the 1933-1935 Atlantis stations in the eastern half of the Gulf with profiles across the Straits of Florida and the Yucatan Channel (Seiwell 1938, figs. 6, 15) and gave charts of the horizontal distribution of oxygen at 100, 250, 500, 750, 1,000, 1,500, and 2,500 meters (Seiwell 1938, figs. 7, 8, 11, 14, 16, 17, 20). Vertical distribution of oxygen at a typ- ical station in the western Gulf (25°40' N., 94°23' W.) was charted by Dietrich (1939, p. 117, fig. 33): from about 4.8 cubic centimeters per liter at the surface, it increased slightly to about 4.9 cubic centimeters at 25 meters, then decreased to a minimum of 2.35 cubic centimeters at 300 meters, then increased gradually to about 5.0 cubic cen- timeters at 2,400 meters, and thereafter remained constant to 3,400 meters. Dietrich (1939, p. 120, fig. 35) also presented a chart showing the dis- tribution of minimum oxygen concentration, re- gardless of depth, in all but the southwest part of the Gulf. The lowest oxygen concentrations (be- low 2.5 cc, per liter) were found in the northwest corner; values below 2.7 cc. per liter were ob- served north of the Campeche Bank and off the central west coast of Florida. Riley (1938, 1939) reported oxygen concentra- tions in surface and subsurface samples in the summer of 1938 at two stations in the Dry Tor- tugas in depths of 3 and 19 meters, one station in the Florida Straits in the depth of 166 meters, and from two stations in the Havana section of the Florida Straits in May 1939. In presenting a detaded summary of oxygen in the Atlantic Ocean he omitted the Gulf of Mexico (Riley 1951). Scattered records of oxygen analyses made in connection with studies of animal mortality in- cluding the red tide have been published by Gunter (1942), Galtsoff (1948), Gunter, WUliams, Davis, and Smith (1948), Connell and Cross (1950), PHOSPHORUS The earliest published record of phosphorus content of Gulf of Mexico water is that of Lipman 146 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE (1929) who reported results of analyses of two samples of water collected at the Dry Tortugas in July 1922: 1.00 and 4.80 parts phosphate per million parts of water (10.5 and 50 microgram- atoms phosphate-phosphorus per liter). Information on the vertical distribution of phosphorus in the Gulf of Mexico is very limited. Determinations of phosphate were made on the 16 samples (surface to 1,732 meters) collected at Atlantis station 1606 in the middle of the Yucatdn Channel in May 1933 (Bulletin Hydrographique, 1934, p. 103). Graphs of the vertical distribution of phosphorus at this station were published by Rakestraw (1936, p. 160, fig. 11) and Rakestraw and Smith (1937, p. 9, fig. 7).^ The phosphate- phosphorus" remained nearly constant at 0.15 /ig-atoms/L from the surface to 97 meters, then in- creased to a maximum of 2.47 at 736 meters, then decreased to 1.71 at 1,732 meters. These data for Yucatan Channel water were used in the charts of horizontal distribution of phosphate at various depths (Rakestraw and Smith, 1937, figs. 10-12). Horizontal and vertical distribution of phos- phate near the mouth of the Mississippi River in March 1937 was reported in tables and a map by Riley (1937, pp. 74, 63). He found about 0.58 ^g-atoms/L in the low salinity surface water at the station at the mouth of the river. Phos- phate decreased in all directions to an average of 0.14 /ig-atoms/L at the stations in the Gulf. Distribution of phosphate at the Dry Tortugas and in the Florida Straits was reported by Riley (1938, 1939) and Riley, Stommel, and Bumpus (1949, p. 16). Near Loggerhead Key where the depth was 3 meters, the phosphate ranged from 0.015 to 0.10 Mg-atoms/L from July 18 to August 2, 1938. At his station midway between Loggerhead and Garden Keys where the depth was 19 meters the phosphate at depths of 1, 5, 10, and 15 meters varied quite differently with depth on 4 days in July 1938 from 0.02 to 0.16 Mg-atoms/L. His data from other stations are summarized in table 1 . Riley (1951) presented a detailed summary of phosphorus distribution in the Atlantic Ocean Table 1. — Vertical distribution of phosphate (yig-atoms ID in the Florida Straits Station depth (meters) Date Levels below surface at which samples were taken (in meters) 1 ig 45 90 100 153 200 300 166 1,719 722 Aug. 6, 1938 May 15. 1939 May 11,1939 0.11 .03 .21 0.02 0.12 0.12 "6.07' .10 1.07 Midway between Havana and Key West. Station number 3491. 0.33 .51 0.68 but omitted the Gulf of Mexico, except for his discussion (p. 15) of the tendency for the products of regeneration (phosphate and nitrate) to ac- ciunulate in the deep water of the Caribbean-Gulf of Mexico basins because the outflow through the Straits of Florida is shallower than the maximum depth of the inflowing water. » There appears to be some confusion regarding units in the three publica- tions dealing with this phosphorus data. The raw data in the Bulletin Hydrographique are reported in milligrams phosphate per cubic meter. When these figures are divided by 95, the corresponding unit is milligram- atoms per cubic meter or microgram-atoms per liter. The scale for fig. 11, p. 160 of Rakestraw (1936) indicates phosphate from to 1.5 microgram-atoms per liter, but the scale for fig. 7, p. 9 of Rakestraw and Smith (1937) indicates phosphate from to 3 milligram-atoms per liter. It is believed that the units in the last paper should be either microgram-atoms per liter or milli- gram-atoms per cubic meter, which are numerically equal. Later papers report this same data in microgram-btoms per liter (Sverdrup, Johnson, and Fleming, 1942, p. 241) or milligram-atoms per cubic meter (Riley, Stommel, and Bumpus, 1949; Riley, 1951). ' Phosphate data reported in this section have been corrected lor salt error by multiplying any uncorrected values by 1.15 (Cooper 1938, p. 177; Robinson and Thompson 1948, p. 36). Results of phosphate analyses at various in- shore stations in the Tampa Bay area and near the southern tip of the Florida peninsula in 1946, reported by Williams (1947) and Smith (1949), are summarized in table 2. Table 2. — Phosphate {ng-aloms/ L) along Gulf coast of Florida in 1946 Area Location of sampling station Date Phosphate ;ig-atoms/L Tampa Bay Do Green Key, Hillsboro Bay do Jan. .30. June 4.. do.... 8.4 12.0 Do 1 mile west of Green Key 8.4 Do Terra Ceia Bay Jan. 29. June 3.. ...do.... Mar. 9. . .do.... May 6. .84 Do Terra Ceia Bay (center) 3.60 Do... Terra Ceia Bay (north side) Yi mile southwest of Catfish Key, Florida Bay. Conchie Channel. Florida Bay.. East River, east of Whitewater Bay. 4.80 Cape Sable Do Do .03 .03 .03 In connection with studies of the red tide along the Gulf coast of Florida in 1947 made during and' OULF OF MEXICO 147 after the blooming of Gymnodinium brevis, the concentrations of inorganic phosplionis were fonnd as high as 7.4 ^g-atoms/L and total phosphorus (particulate organic, dissolved organic, and in- organic) up to 20.4 Mg-atoms/L in the amber colored water (Ketchum and Keen 1948, p. 18; Gunter, Williams, Davis, and Smith, 1948, p. 319: Galtsoff 1948, p. 20; Smith 1949, p. 5). These unusually high phosphorus concentra- tions suggested the need for more detailed informa- tion on horizontal, vertical, and seasonal dis- tribution of phosphorus compounds to clarify the fundamental causes of the red tide. Ac- cordingly, when the research program of the Fish and Wildlife Service laboratory in Sarasota, Florida, was planned studies of the distribution of total, inorganic, and organic phosphorus were given primary attention. Results of a detailed survey at 13 stations in the rivers, along the middle Florida coast, and 120 miles west to the 100-fathom line from May 1949 to August 1950 have been published (Graham, Amison, and Marvin, 1954). They show a gradual decrease in phosphorus content of the surface water with increase in distance from shore. The phosphorus- rich waters discharged from the Peace River did not affect, however, the local Gulf waters to any measurable degree. Beyond 14 miles from shore the concentration of total phosphorus in the sur- face water was usually below 0.25 fig-atoms/L and inorganic phosphorus was usually below 0.10 Mg-atoms/L. Larger quantities of phos- phorus, mostly inorganic, were found at depths below 50 meters. Occasional upwelling did not seem to influence the phosphorus content of the eu photic zone. There was no evidence of the bottom sediments contributing any appreciable quantities of phosphorus to the water. Local concentrations of the planktonic blue-green alga, Trichodesmium, appeared to be associated with high concentrations of total phosphorus. NITRATE-NITROGEN Studies of nitrate distribution in the Gulf have generally paralleled those of phosphate reviewed above. Vertical distribution of nitrate in the middle of the Yucatin Channel in May 1933 (Bulletin Hydrographique, 1934, p. 103) was indicated in a graph by Rakestraw (1936, p. 160, fig. 11) and Rakestraw and Smith (1937, p. 9, 259534 0—54 11 fig. 7).' The nitrate decreased from 2.4 Mg- atoms/L at the surface to 1.4 ^g-atoms/L at 49 meters, then increased regularly to a maximum of 37.1 Mg-atoms/L at 736 meters, then decreased to 24.2 Aig-atoms/L at 1,732 meters. These data for Yucatdn Channel water were used in the charts of horizontal distribution of nitrate at various depths (Rakestraw and Smith, 1937, figs. 14-16). Although no nitrate determinations were made on Gulf waters near the mouth of the Mississippi, Riley (1937, p. 69) reported the following data (supphed by A. A. Hirsch of the New Orleans Sewerage and Water Board Company) which are 1935 average values for the Mississippi River water at New Orleans: Ammonia nitrogen 20 mg/m' Albuminoid nitrogen 350 mg/m' Nitrite nitrogen 5 mg/m' Nitrate nitrogen 200 mg/m' Nitrate data for two stations in the Florida Straits reported by Riley (1939, p. 161) are sum- marized in table 3. Table 3. — Vertical distribulion of nitrate-nitrogen {ixg-atomsl L) in the Florida Straits Location Station depth (meters) Date Levels below surface at which samples were taken (in meters) 1 100 200 300 Midway between Ha- vana and Key West. Station No. 3491 Off Matanias, Cuba, Station No. 3486 1,719 722 May 15,1939 May 11,1939 1.70 1.00 0.31 .60 0.93 2.21 14.3 Riley, Stommel, and Bumpus (1949, p. 16, fig. 6) used these surface values for southeastern Gulf water in their summary chart and discussed the origin of Caribbean water from the nutrient-poor Equatorial and Antilles Currents. They ex- plained, however, that the Caribbean "also re- ceives a substantial draught of Antarctic inter- mediate water, which is very rich, particularly in nitrate. The maximum concentration of this substance at a depth of about 800 meters in the Caribbean (and possibly the Gulf of Mexico) ex- ceeds the amount found anywhere else in the western North Atlantic." Some of this may be accumulated products of regeneration, as sug- gested for phosphate (Riley 1951). ' There appears to be a confusion of units for expre.ssine these nitrate data parallel to that discussed for phosphate in footnote 5. 148 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE NITRITE-NITROGEN Distribution of nitrite-nitrogen in the Gulf of Mexico is almost unknown except for a single station in the Yucatan Channel and a few analyses of surface water along the Florida west coast made in 1946-47 by Williams (1947) and Gunter, Williams, Davis, and Smith (1948), (table 4). Table 4. — Nitrite-nitrogen along Gulf coast of Florida, 1946-4? [Observations by Williams, Ounter, Davis, and Smith] Area Location Date Nitrite- nitrogen Mg-atoms/L Tampa Bay... Do Oreen Key. Hillsborough Bay. ...do - - Jan. 30.1946 June 4, 1946 do Jan. 29,1946 June 3, 1946 do Mar. 9,1946 ...do May 6,1946 Apr. 12,1947 do Do Do Do Do.. Cape Sable Do Do .- Key West Do 1 mile west of Green Key, Hillsboro Bay. Terra Ceia Bay Terra Ceia Bay (center) Terra Ceia Bay (north side)... M mile southwest of Catfish Key. Florida Bay. Conchie Chamiel, Florida Bay. East River, east of White- water Bay. 2^^ miles north of Content Keys. 2 miles north of Barracuda Keys. ^1 2 .2 Vertical distribution of nitrite at Atlantis station 1606 in the middle of the Yucatdn Channel May 4, 1933, depth 1,911 m., reported in the Bulletin Hydrographique (1936, p. 103) and by Rakestraw (1936, p. 149, table 9)* is summarized in table 5. Table 5. — Nitrite-nitrogen in the Yucatdn Channel Depth (meters) Nitrite- nitrogen Mg-atoms/L Depth (meters) Nitrite- nitrogen Mg-atoms/L 0.135 .01 .01 .11 .035 .03 300 0.02 28 400 .01 50 500 .01 100 600..-. .01 150 800 .01 200 HYDROGEN ION CONCENTRATION (pH) The hydrogen ion concentration of sea water at the Dry Tortugas from the surface to 35 meters varied between the pH values of 8.1 and 8.28 (McClendon, 1916a, 1916b, 1918; IVIayor, 1922). Published data on vertical distribution of pH in deeper waters of the Gulf are limited to those taken at Atlantic station 1606 in the middle of the Yucatan Channel May 4, 1933. They were re- ported in the Bulletin Hydrographique (1936, • The graph of this nitrite distribution (Rakestraw, 1936, p. 160, flp. II) docs not correspond to the figures in the tables. p. 103), corrected for depth to represent condi- tions in situ, and diagrammed by Rakestraw and Smith (1937, figs. 7, 18-20). The pH increased slightly from 8.14 at the surface to 8.17 at 24 meters, then decreased to a minimum of about 7.9 at 736 meters, then increased to about 8.03 at 1,537 meters. Measurements of the pH of shallow waters of Galveston Bay were made by Wise, Winston, and CuUi (1945). Detailed studies of pH distribution at 26 stations in the coastal bays between New Orleans and Biloxi were reported by Gunter (1950) ; the pH values ranged from 6.66 in Pearl River entering Lake Borgne, to 8.35 in American Bay, off Breton Sound. Determinations of pH on the sea water col- lected during and after the red tide (Galtsoff, 1948, pp. 23-24; Gunter, Williams, Davis, and Smith, 1948, p. 319, table 9) indicated no abnormal hydrogen ion concentrations. ALKALINITY AND CARBON DIOXIDE The alkalinity or buffer capacity and con- centrations of carbonic acid (including the free carbon dioxide), bicarbonate, and carbonate have been studied in Gulf of Mexico water in the Dry Tortugas by Dole (1914), McClendon (1918), Mayor (1922), Wells (1922), and Lipman (1929), and in the Yucatin Channel by Mitchell and Rakestraw (1933), and Rakestraw and Smith (1937, p. 2, table 1; p. 9, fig. 7). COPPER According to Riley (1937) soluble copper and copper adsorbed on plankton and detritus is distributed horizontally and vertically in all direc- tions from the mouth of the Mississippi River as far as the 1 ,000-f athom line. All samples analyzed by him showed the concentrations of soluble copper from 1 to 25 mg/m ' and that of adsorbed copper from 0.3 to 7.2 mg/m.' The high copper values in the surface samples were generally found in waters of low salinity. At the 1,000-fathom station, soluble copper increased from 5 mg/m ' at the surface to 9, 10, 10, and 12 mg/m ' at 100, 300, 600, and 1,800 meters depth, respectively. MISCELLANEOUS CHEMICAL CONSTITU- ENTS Bromine content of the Gulf of Mexico water has been studied in connection with the commercial GULF OF MEXICO 149 extraction of this material at the plant constructed in 1940 at Freeport, Texas. Calcitini ran^inK ^rom 427 to 535 mg/kg was reported by iiipman (1929) in two samples collected at the Dry Tortugas in July 1922. Calcium carbonate precipitation in the water in the Marquesas lajioon when the pH was 8.46 was observed by McClendon (1928, p. 258). The mechanism of this process was studied by various chemists and bacteriologists at the Dry Tortugas and elsewhere (McClendon 1918, pp. 252-258; Gee 1934; Gee and Feltham 1934). Hydrogen sulfide was indicated in West Galves- ton Bay by blackening of the white lead paint on boats at a time of animal mortality (Gunter 1942). Tests for hydrogen sulfide were made on the red tide water, but no clearly positive results were found (Gunter, Williams, Davis, and Smith, 1938, p. 320). Iron ranging from 0.12 to 1.50 mg/kg was re- ported by Lipman (1929) in two samples from the Dry Tortugas. Magnesium content of 1,300 mg/kg was reported by Shiglcy in this book in the Gulf water at Freeport, Texas, where plants were erected for the com- mercial extraction of this metal from sea water.' Various organic compounds have been reported present in Gulf waters. Gunter (1942) concluded that the mortality of marine organisms in an inshore area was caused by oxygen deficiency as- sociated with decay of organic materials and the accumulation of toxic products of anaerobic decomposition. Riley (1937) reported from 0.23 to 20.60 mg/L of organic matter in the Gulf water in the area near the mouth of the Mississippi River. Both plankton and organic detritus ad- sorbed significant amounts of copper. Woodcock (1948) studied an unidentified human respiratory irritant, probably a product of the blooming Gymnodinium brevis which was carried ashore in minute droplets of sea water. A carbohydrate which showed some of the chemical properties of arabinose was found in concentrations from 2 to 25 mg/L in the natural sea water supply at the U. S. Fisheries Station at Pensacola, Florida (Collier, Ray, and Magnitzky, 1950). Products of industrial and sewage pollution have been reported in Texas coastal waters (Burr 1945a, b; Wise, Winston, and Culli, 1945). Potassium concentrations of 404 and 435 mg/kg were reported in two samples of sea water from the Dry Tortugas (jjipman 1929). Silicon concentrations of 9.80 and 11.10 mg. SiOj per kilogram were reported in the same samples (Lipman 1929). Solids reported by Lipman (1929) from analyses of the two samples of Dry Tortugas water are summarized in table 6. Table 6. — Solids, mg/kg, in Dry Tortugas sea water Sample No.l Sample No. 6 35891 34018 1873 37750 Nonvolatile solids 34580 Volatile solids 3170 Distribution of dissolved solids was studied at 26 stations in the coastal bays from New Orleans to Biloxi by Gunter (1950) who reported values ranging from 92 to 29,164 parts per million or milligrams per kilogram. SUMMARY Salinity distribution in the Gulf of Mexico is fairly well known except for the general absence of data on seasonal variations in offshore waters.'" The same could be said of oxygen distribution. Phosphorus distribution is known only for four small areas: Florida Straits, Yucatdn Channel, central west coast of Florida, and the Mississippi Delta region. Nitrate, nitrite, pH, alkalinity, carbon dioxide distributions are known only in the Yucatdn Channel-Florida Straits corner of the Gulf and there for only one or two seasons of the year. Other chemical data are scarce, scattered, or absent. It is expected that considerable information will soon become available with the publication of results of studies sponsored by the chemical and oil companies and of those being conducted by the research vessels and in the shore laboratories of the Fish and Wildlife Service. ' The extraction of bromine and magnesium from sea water is discussed in an article by C. M. Shiglcy, The Recovery of Minerals from Sea Water, p. 153. ■0 Seasonal and local variations of chlorinity and salinity in offshore waters of a portion of the Oulf of Mexico are being studied by the American Petro- leum Institute (Project 61) through Scripps Institution of Oceanography ol the University of California and the Department of Oceanography of the Agricultural and Mechanical College of Texas. Salinity data can be found in the Progress Reports of the Department of Oceanography, Agricultural and Mechanical College of Texas, Project 34, for October 1 to December 31, 1951. and January 1 to March 31, 1952. 150 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE LITERATURE CITED Burr, J. G. 1945a. Ferric salt deposits vs. fish and oysters. Texas Game and Fish 3 (2): 16-17. 1945b. Ferric salt deposits in Galveston Bay in relation to fish and oysters. Trans. Texas Acad. Sci. 28: 223-224. Collier, Albert, and Hedgpeth, J. W. 1950. An introduction to the hydrography of the tidal waters of Texas. Pub. Inst. Mar. Sci., Univ. Texas, 1 (2): 121-194. Ray, S., and Magnitzky, W. 1950. A preliminary note on naturally occurring organic substances in sea water affecting the feeding of oysters. Science 111 (2876): 151-152. CoNNELL, Cecil H., and Cross, J. B. 1950. Mass mortality of fish associated w-ith the proto- zoan Gonyaulax in the Gulf of Mexico. Science 112 (2909): 359-363. CoNSEiL Permanent International Pour l'Explora- TioN de la Mer. 1933-36, 1950. Bulletin Hydrographique pour les annees 1932, 1933, 1934, 1935, 1940-46, avec appendice: Atlantique-Florida, 1936-39. Copenhagen. Cooper, L. H. N. 1938. Salt error in determinations of phosphate in sea water. Jour. Mar. Biol. Assoc. U. K. 23 (1) : 171-178. Davis, Charles C, and Williams, Robert H. 1950. Brackish water plankton of mangrove areas in southern Florida. Ecology 31 (4): 519-531. Dietrich, Gijnter. 1939. Da,s Amerikanische Mittelmeer. Ein meeres- kundlicher tJberblick. Zeitschr. d. Gesellsch. f. Erd- kunde zu Berlin, 1939, Nr. 3/4, pp. 108-130. Dole, Richard B. 1914. Some chemical characteristics of sea water at Tortugas and around Biscayne Bay, Florida. Pap. Tortugas Lab., Carnegie Inst. Washington Pub. No. 182, 5: 69-78. Galtsoff, Paul S. 1931. Survey of oyster bottoms in Texas. U. S. Bur. Fish., Inv. Rept. No. 6, 30 pp. 1948. Red tide. Progress report on the investigations of the cause of the mortality of fish . . . U. S. Dept. Interior, Fish and Wildlife Service, Spec. Sci. Rept. No. 46, 44 pp. Gee, Haldane. 1934. Lime deposition and the bacteria. I. Estimate of bacterial activity at the Florida Keys. Pap. Tortugas Lab., Carnegie Inst. Washington Pub. No. 435, 28: 67-82. and Feltham, C. B. 1934. Lime deposition and the bacteria. II. Charac- teristics of aerobic bacteria from the Florida Keys. Pap. Tortugas Lab., Carnegie Inst. Washington Pub. No. 435, 28: 83-91. Geyer, Richard A. 1950. The occurrence of pronounced salinity variations in Louisiana coastal water. Jour. Mar. Res. 9 (2) : 100-110. Graham, Herbert W.; Amison, J. M.; and Marvin, K. T. 1954. Phosphorus content of waters along the west coast of Florida. U. S. Dept. Int., Fish and Wildlife Service, Sp. Sci. Rept., No. 22: 1-43. GuNTER, Gordon. 1942. Offats Bayou, a locality with recurrent summer mortality of marine organisms. Am. Midi. Nat. 28 (3): 631-633. 1945. Studies on marine fishes of Texas. Pub. Inst. Mar. Sci., Univ. Texas, 1 (1): 1-190. 1947. Catastrophism in the sea and its paleontological significance, with special reference to the Gulf of Mexico. Am. Jour. Sci. 245: 669-676. 1950. Oyster mortality study. Appendix I. Results of water analysis, 1950 Bonnet Carr6 Spillway opera- tion. Rept. to Corps of Engrs., U. S. Army, Office of the Dist. Engr., New Orleans, La. GuNTER, Gordon; Williams, R. H.; Davis, C. C; and Smith, F. G. Walton. 1948. Catastrophic mass mortality of marine animals and coincident phytoplankton bloom on the west coast of Florida, November 1946 to August 1947. Ecol. Monogr. 18 (3): 309-324. HiGGiNs, Elmer. 1931. Progress in biological inquiries, 1929. Doc. 1096, App. XV, Rept. of U. S. Comm. Fish., 1930, pp. 1069-1121. and Lord, Russell. 1926. Preliminary report on the marine fisheries of Texas. Doc. 1009, App. IV, Rept. of U. S. Comm. Fish., 1925, pp. 167-199. Ingle, Robert M. 1951. Spawning and setting of oysters in relation to seasonal environmental changes. Bull. Mar. Sci. Gulf & Caribbean 1 (2): 111-135. and Dawson, Jr., C. E. 1951. Variation in salinity and its relation to the Florida oyster. Salinity variations in Apalachicola Bay. Proc. Third Ann. Sess. Gulf and Caribbean Fish. Inst., Miami Beach, 1950, pp. 35-42. Jacobsen, J. P. 1929. Contributions to the hydrography of the North Atlantic. Danish Dana Exped. 1920-22. Oceanogr. Rept. No. 3. Copenhagen. Johnson, S. H. 1882. Notes on the mortality among fishes of the Gulf of Mexico. Proc. U. S. Nat. Mus., 4: 205. Kbtchum, Bostwick H., and Keen, Jean. 1948. Unusual phosphorus concentrations in the Florida "red tide" sea water. Jour. Mar. Res. 7 (1): 17-21. Lindner, Milton J. 1939. The cooperative shrimp investigations. Louisi- ana Dept. Conser., 13th Biennial Rept., pp. 447-455. 1941. The Texas fisheries. (Mimeographed report). In: Baughman, J. L., An annotated bibliography for the student of Texas fish and fisheries with material on the Gulf of Mexico and the Caribbean Sea. (Un- dated), pp. 213-238. GULF OF MEXICO 151 Lll'MAN, C. B. 192!). The fheinical composition of sea-water. Pap. Tortugas Lab., Carnegie Inst. Washington Pub. No. 391, 26: 24<)-257. McClendon, J. F. 191(ia. The composition, especially the hydrogen ion concentration, of sea water in relation to marine organisms. Jour. Biol. Chom. 28: 135-152. 1916b. Hydrogen ion concentration of sea water, and the physiological effects of ions in sea water. Proc. Nat. Acad. Sci. 2: 689-692. — 1918. On changes in the sea and their relation to organ- isms. Pap. Tortugas Lab., Carnegie Inst. Washing- ton Pub. No. 252, 12: 213-258. Mayor, Alkreo G. 1922. Hydrogen-ion concentration and electrical con- ductivity of the surface water of the Atlantic and Pacific. Pap. Tortugas Lab., Carnegie Inst. Wash- ington Pub. No. 312, 18: 63-86. Mitchell, P. H., and Rakestraw, N. W. 1933. The buffer capacity of sea water. Biol. Bull. 65 (3): 437-451. Montgomery, R. B. 1941. Transport of the Florida Current off Habana. Jour. Mar. Res. 4 (3): 198-220. Nielsen, J. M. 1925. Golfstr0mmen. Geografisk Tidsskrift 28: 49-59. Parr, A. E. 1935. Report on hydrographie observations in the Gulf of Me.xico and the adjacent straits made during the Yale Oceanographic Expedition on the Mabel Taylor in 1932. Bull. Bingham Oceanog. Coll., vol. 5, art. 1, pp. 1-93. 1937. A contribution to the hydrography of the Carib- bean and Cayman Seas. Bull. Bingham Oceanog. Coll., 5, (4): 1-110. Price, W. Armstrong. 1947. Equilibrium of form and forces in tidal basins of coast of Texas and Louisiana. Bull. Am. Assoc. Petrol. Geol. 31 (9): 1619-1663. Rakestraw, N. W. 1936. The distribution and significance of nitrite in the sea. Biol. Bull. 71 (1): 133-167. and Smith, IJ. P. 1937. A contribution to the chemistry of the Caribbean and Cayman Seas. Bull. Bingham Oceanog. Coll., 6(1): 1-41. Rathbun, Richard. 1895. Report on the inquiry respecting food fishes and fishing grounds. Rept. of U. S. Comm. Fish. 19: 17-51. Riley, Gordon A. 1937. The significance of the Mississippi River drainage for the biological conditions in the northern Gulf of Mexico. Jour. Mar. Res. 1 (1): 60-74. 1938. Plankton studies. I. A preliminary investiga- tion of the plankton of the Tortugas region. Jour. Mar. Res. 1 (4): 335-352. Riley, Gordon A. — Continued 1939. Plankton studies. II. The western North At- lantic, May-June 1939. Jour. Mar. Res. 2 (2): 145-162. 1951. Oxygen, phosphate and nitrate in the Atlantic Ocean. Bull. Bingham Oceanog. Coll., 13(1): 1-126. Stommel, H.; and Bumpus, D. F. 1949. Quantitative ecology of the plankton of the western North Atlantic. Bull. Bingham Oceanog. Coll., 12(3): 1-169. Robinson, Rex J., and Thompson, Thomas G. 1948. The determination of phosphates in sea water. Jour. Mar. Res. 7 (1): 33-41. Schmidt, Johannes. 1929. Introduction to the oceanographical reports in- cluding list of the stations and hydrographical observations. The Danish Dana-Expeditions 1920- 22 in the North Atlantic and Gulf of Panama, Oceanog. Repts. edited by the Dana-Committee, No. 1, pp. 1-87. Seiwell, H. R. 1938. Application of the distribution of oxygen to the physical oceanography of the Caribbean Sea region. Pap. in Physical Oceanog. and Meteorol. 6 (1): 1-60. Smith, F. G. Walton. 1949. Probable fundamental causes of red tide off the west coast of Florida. Quart. Jour. Florida Acad. Sci. 11 (1): 1-6. SvERDRUP, H. U.; Johnson, M. W.; and Fleming, R. H. 1942. The oceans: their physics, chemistry, and general biology. 1087 pp. Prentice-Hall, Inc., New York. Trask, Parker D.; Phleger, Fred B., Jr.: and Stetson, Henry C. 1947. Recent changes in sedimentation in the Gulf of Mexico. Science 106 (2759): 460-461. Vaughan, Thomas Wayland. 1918. The temperature of the Florida coral reef tract. Pap. Tortugas Lab., Carnegie Inst. Washington Pub. No. 213, 9: 319-339. 1937. International aspects of oceanography. 225 pp. National Academy of Sciences, Washington, D. C. Wells, Roger C. 1922. Carbon dioxide content of sea water at Tortugas. Pap. Tortugas Lab., Carnegie Inst. Washington Pub. No. 312, 18: 87-93. Williams, Robert H. 1947. Relation of birds to plankton and fish in Tampa Bay. Paper read at Twelfth Annual Meeting of the Florida Academy of Sciences, Tallahassee, Fla. Wise, Robert I.; Winston, Joe B.; and Culli, George, Jr. 1945. Bacteriological studies of oyster beds. (Abstr.) Proc. Trans. Texas Acad. Sci. 28: 90-91. Woodcock, A. H. 1948. Note concerning human respiratory irritation as- sociated with high concentrations of plankton and mass mortality of marine organisms. Jour. Mar. Res. 7 (1): 56-62. THE RECOVERY OF MINERALS FROM SEA WATER By C. M. Shigley, The Dow Chemical Company Man's hope to develop power from the sea has not yet been reaHzed, but the prospect of recovery of minerals from that mighty storehouse has long since become real. It is the purpose of this writing to trace the history of the extraction of minerals from the seas, to describe recent large commercial projects for recovering elemental bromine and magnesium from sea water, and to briefly discuss a few of the economic factors in such sea water extraction operations. The total volume of the oceans is estimated to be 320 million cubic miles (Armstrong and Miall, 1946). Although the salinities of the several seas vary somewhat, the average is approximately 35,000 parts of dissolved salts per million, equiv- alent to 165 million short tons per cubic mile. The oceans of the world thus represent a store- house of about 50 million billion tons of dissolved materials. The chloride ion represents 54.8 per- cent of the total salts, the sodium ion 30.4 percent, sulphate 7.5 percent, magnesium 3.7 percent, calcium 1.2 percent, potassium 1.1 percent, carbonate 0.3 percent, and bromide 0.2 percent. Although the sea is believed to contain at least traces of every clement, these eight ions account for over 99 percent of the sea water salts; all other elements total less thaa 1 percent. Since the sodium and chloride ions represent sLx-sevenths of the dissolved salts and are the most easily extracted, it is not surprising that they seem to have been involved in the first recovery on record. Sodium chloride, common salt, was undoubtedly the first compound to be removed from sea water and used by man. It is believed that salt was used by cave men at least 5,000 years ago. Salt from sea water is mentioned in Chinese writings about 2200 B. C. Aristotle in his Meteorologica wrote of the origin and usefulness of the salts of sea water and described a method of "unsalting" sea water. The ancient Greeks, Romans, and Egyptians were familiar with produc- tion of salt by solar evaporation of sea water. Such salt recovery has been common in China, India, and Japan for many centuries, and still continues. Salt from sea water was produced on the Atlantic coast of North America about 1680 and on the Pacific coast in 1852. The Atlantic coast industry was short lived, but that on the Pacific coast has thrived to this time. The production of crude soda and potash from the ashes of seaweeds was accomplished in Scotland as early as 1720. Iodine was recovered from seaweeds for the first time early in the nineteenth century; magnesia was first prepared on the Mediterranean coast at the end of the century. The records do not indicate any additional progress until 1923 when magnesium cliloride and gypsum were produced from the bitterns from solar evap- oration of the sea water of San Francisco Bay (Seaton 1931). These bitterns were first treated with calcium chloride, precipitating the sea water sulfate as calcium sulfate, which was settled and filtered. Concentration of the filtrate, cooling and separa- tion of the residual magnesium sulfate, potash, and other salts by settling and centrifuging, gave a fairly pure magnesium chloride solution which was further concentrated to salable form by boil- ing. The calcium sulfate resulting from the calcium chloride treatment was washed, dried, and sold as gypsum. In 1926, the first sea water bromine was recov- ered on a small commercial scale by chlorinating the San Francisco Bay bitterns, steam stripping, condensing, and purifying the product. In 1931, the production of potassium chloride by evaporation of the waters of the Dead Sea was inaugurated; in 1932, bromine was recovered on a commercial scale from the residual liquors of the potassium plant using a process similar to that employed for San Francisco bitterns. Prior to 1933, the survival of the majority of the projects recovering material from sea water depended upon solar evaporation for initial con- 153 154 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE centration of the valuable sea salts. A few projects depended on adsorption or biochemical conceiitration as exemplified by the production of soda, potash, and iodine from seaweeds. Of the other likely methods of recovery, precipitation bj^ a specific reagent had been demonstrated in the commercial production of magnesia bj' liming sea water and in the experimental removal of bro- mine as the insoluble tribromoaniline. The latter process was developed in 1924 by the Ethyl Gaso- line Corporation and carried to large scale experi- mental work in the floatmg chemical laboratory, the S. S. Ethyl (Stine 1929). Separation by ion exchange processes or by selective volatUization of the material sought had not j^et been commer- cially exploited. In 1933, a sharp increase in the demand for ethylene dibromide as a constituent of gasoline anti-knock could not be readily met by increasing the output of bromine plants using subterranean brines. Based on experimental work done in anticipation of this need, a plant was constructed by the Ethyl-Dow Chemical Company on the Atlantic coast at Kure Beach, North Carolina, to remove bromine directly from sea water without the prior concentration which had been necessary for the earlier commercial recoveries. The sig- nificant feature of this operation was that the small amount of bromine was removed as a gas from the relatively large volume of water; past efforts had largely been directed toward removal of large amounts of water as vapor from the relatively small amounts of dissolved salts. The original Kure Beach plant was designed to extract 6 million pounds of bromine per year for the production of ethjdene dibromide. Through minor additions and process improvements the capacity was increased to nearly 9 million pounds per year. In 1937 the capacity of the plant was doubled, and in 1938, increased again, reaching an output of approximately 40 million pounds per year. In 1940 a further increase in bromine require- ments led to the erection of a plant at Freeport, Texas, to recover bromine from the waters of the Gulf of Mexico. This plant had an initial capacity of about 30 million pounds of bromine per year; a second imit of equal output was built in 1943. Another milestone in the recovery of minerals from sea water was passed in 1941 when at Free- port, Texas, the first magnesium metal was pro- duced from water of the Gulf of Mexico by the Dow Chemical Company. Although the pre- cipitation of magnesium hydroxide from sea water bitterns and brines and the method of making magnesium metal from magnesiimi chlo- ride were both well known prior to 1941, it was not until then that these methods were revised and integrated to give an economically feasible process for making metallic magnesium from sea water. The success of the first 18 mUlion pounds per year magnesium plant was shown by the erection of another plant of equal size 1 year later. In 1942, a 72 million pounds per year magnesium metal-from-sea-water plant was built by the United States Government at Velasco, Texas, as a part of the program planned to meet emergency war-time needs. The plant was designed and run by the Dow Magnesium Corporation. It operated at or above rated capacity for the duration of the war. That sea water represented no handicap as a source of raw material for the newly developed magnesium process was demonstrated by compar- ative costs published by the Defense Plant Corpo- ration, after cessation of hostilities (Klagsbrunn 1945). The Velasco plant of the Dow Magnesium Corporation bettered by nearly 30 percent the lowest cost achieved by other government plants using more concentrated magnesium sources. Unfortunately, both this government-owned magnesium project at Velasco and the privately owned bromine plant at Kiu-e Beach were among the war casualties when wartime production capacity encountered reduced peacetime demands. However, economic survival was largely in favor of the sea-water processes. Since World War II the entire United States production of virgin magnesium and an estimated four-fifths of the bromine have been derived from sea water. The processes which have been successfully used for bromine production at Kure Beach, North Carolina, and Freeport, Texas, and for magnesium at Freeport and Velasco, Texas, are chemically very simple. They have been de- scribed in detail in articles by vStewart (1934), KLrkpatrick (1941), Schambra (1945), and others but are worthy of brief review. There are two bromine extraction processes. Both can achieve recoveries of bromine from sea water approaching 90 percent. The first, called the "alkaline process," is the one which was used for the initial phases of the Kure Beach develop- GULF OF MEXICO 155 ment. Sea water, which contains 69 parts per milHon bromine, is carefully screened to remove debris, seaweed, and fish and is continuously pumped to the top of a "blowing out tower," a brick structure packed with wood grids. On its way to the top of the tower it receives chemical additives which convert the nonvolatile bromide of the water to relatively volatile free bromine. The first additive is dilute sulphuric acid which is automatically controlled to reduce the pH of the sea water from 7.8 to 3.5 and thus suppress the hydrolysis of the free halides. The second additive is chlorine gas. This is injected in an amount slightly in excess of the equivalent bro- mide, converting it to free bromine. At the top of the blowing out tower the treated brine is distributed evenly over the upper layers of wood packing and trickles downward through the pack- ing to outlet ports about 40 feet below. As it slowly moves down, a current of ah- is drawn into the bottom of the tower by fans at the end of the system; it passes up through openings in the grids and blows the free bromine out of the treated sea water. The latter now passes back to the ocean at some distance from the intake, little changed except for its bromine content. The bromine-laden air from the top of the blow- ing out tower next passes to the soda ash absorption tower. This consists of nine spray chambers in series, each chamber having its own separate recycle system for spraying alkaline absorption liquor. Here nozzles at the top of each chamber spray a dilute soda ash solution into the air stream. The sodium carbonate reacts with the bromine and puts it into solution as a mixture of sodium bromide and sodium bromate. Continued re- circulation of the alkaline solution builds up the concentration of bromide-bromate, and at regular intervals the solution of highest concentration from the chamber adjacent to the blowing out tower is pumped to a storage tank. The charges of partially brominated alkaline solution in the other chambers are eacii pumped forward one step, and when the solution in the weak end of the system has been forwarded the last chamber is recharged with a fresh 5 percent soda ash solution. By means of this batch-countercurrent recir- culation a solution is obtained which is nearly eight-hundred-fold more concentrated in bromine than the original sea water. Tli(> production of pure liquid bromine from the sodium bromitle-sodium bromate solution is ac- complished by a second operation. The solution, which has a slight residual alkalinity, is pumped over a brick-lined scrubber tower where it serves to absorb bromine from the condenser vents. A small amount of steam is added to the bottom of the tower to preheat the liquor for the stripping step. A controlled excess of 60° Be sulphuric acid is then mixed with the liquor, and the reaction between sodium bromide and sodium bromate in the acidic solution produces free bromine. The mixture passes to a continuous steam-stripping column of acidproof construction. The bromine is distilled off and together with excess steam is liquefied in ceramic or glass condensers. The immiscible water layer saturated with bromine is returned to the stripping column. The bromine is purified by distillation, yielding elemental liquid bromine having a purity of 99.7 percent plus. The slightly acid stripping column effluent is added to the incoming sea water to utilize its relatively small acid content. The second bromine process, known as the "acid process" or "SO2 process," was developed in 1937 and has been used in all bromine-from-sea- water plants built in the United States since that date. In this method the acidification, chlorina- tion, and blowing out of the sea water are carried out essentially the same as before. Into the bromine-laden air from the blowing out tower is injected a carefully controlled flow of dilute SO2 gas prepared by burning sulphur in a conventional type burner and cooling the 10-12 percent S02 so obtained. The two gas streams are thoroughly mixed by passing through a system of carefully designed baffles, whereupon the bromine reacts with the slight excess of SO2 in the presence of water vapor to give a mixture of hydrobromic and sulphuric acids in the form of a fine acid mist. Tlie acids are readily scrubbed from the air stream by fresh water in an absorption tower. The resultant acid solution has a bromide content of approximately 7 percent, or 70,000 parts per million. This step thus accomplishes a one- thousandfold concentration of the original bromine of the sea water. The bromine is removed from the strong acid solution by a method very similar to that em- ployed in the "alkaline process." The acid liquor is pumped over a packed column where it 156 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE scrubs bromine from the condenser vents. It is preheated in that tower by the addition of live steam. Chlorine equivalent to tliree-fourths of the hydrobromic acid is added with the steam. The liquid mixture then passes to a steam strip- ping column where the remainder of the equivalent chlorine is added and the free bromine is steam distilled out of the solution. The bromme- steam vapor from the top of the tower is con- densed as before, and purification of the liquid bromine so obtained yields a product of quality equal to that of the first described method. The hot effluent from the stripping column con- sists of a mixture of hydrochloric and sulphuric acids. It is added to the incoming sea water and under normal conditions supplies approximately two- thirds of the acid requirements of the blowing- out step. The factors which determine the competitive position of either or both of these sea water ex- traction processes differ only slightly from those encountered in the consideration of any economic enterprise. One must principally consider location of raw materials, efficiency of the process, materials of construction, and manpower. The proper location of a plant utilizing either bromine process is particularly important to the success of the project. A place is required where sea water of high and constant salinity is con- veniently available, free from organic contamina- tion, and undiluted by major fresh-water rivers. It must also possess favorable circumstances for disposing of the large quantities of processed water without mixing with the unprocessed water. Where shallow water and variable currents pre- vail, the intake and effluent systems should be widely separated. Deep water along shore and constantly favorable shore currents lessen the need for such separation. A plant site only slightly above sea level is preferable to reduce pumping costs. Since both processes depend on vaporization of bromine, and since the vapor pressure of bromine in sea water varies considerably with temperature, a location in a warm climate is highly desirable. Other things being equal, a blowing-out tower handling 25° C. sea water can operate at a higher rate and can produce approximately twice the amount of bromine as the same tower operating at 10° C. The absorption of the alkali process is also susceptible to temperature effects. Absorber losses are five- to fifteen-fold more at 10° C. than at 25° C, depending on the excess alkalinity of the absorbing solution. A location as near as possible to the source of economical raw materials and power and to the point of disposal of the finished product is desirable; but other factors are of secondary importance when compared with the need for favorable oceanographic and climatic conditions. Because of the relatively large quantities of raw materials which must be handled in order to obtain each pound of bromine, it is necessary that very close operational control be maintained at aU points. Since reliable indicators and automatic controls have made a large contribution to the success of the large scale recovery of bromine from sea water (Hart 1947), they must be regarded as integral parts of both processes. The manufacture of magnesium from sea water is quite different from bromine processes. Magne- sium is taken out of the sea water in an alkaline condition instead of acid and is removed by pre- cipitation rather than blowing out. The process is carried out in 10 well-defined steps. In the first step, sea water containing 1,300 parts per million magnesium is screened as in the bromine process and is continuously treated with an excess of milk of lime. The lime used in the present operation is prepared by calcining oyster shells at 1,200° to 1,400° C. to produce chemical lime of purity over 96 percent, slaking the lime hot, and settling the calcium hydroxide to a heavy slurry. An excess of 20 percent of the theoretical lime is necessary to keep boron compounds in solution. The boron of the sea water, if absorbed by the hydroxide and carried through the process, gives difficulty in the final electrolysis step. The limed sea water is delivered to standard Dorr settling tanks. There the precipitated magnesium hy- droxide settles to the bottom and is drawn off as a thin slurry having a composition of about 12 percent magnesium hydroxide by weight. The overflow from the Dorr tanks is discarded; it represents nearly 98 percent of the water and other materials with which the magnesium was originally associated. The next step consists of filtering the slurry on Moore batch-type leaf filters. In this step approxi- mately half of the remaining water and soluble materials are separated from the magnesium GULF OF MEXICO 157 hydroxide. Filter cake containing 25 percent of magnesium hydroxide by weight is obtained. The third step provides for neutralization of the alkaline filter cake. The cake is mixed with previously prepared magnesium chloride solution and agitated to make a slurry which caa be pumped. It is transferred to a neutralizing tank where an automatically controlled stream of hydrochloric acid is added to exactly neutralize the magnesium hydroxide. Thus, a 15 percent magnesium chloride solution is obtained. The fourth step consists of evaporation of the magnesium chloride solution to eliminate water and to reduce the solubility of salts picked up from the sea water. Evaporation is accomplished in either of two ways. In the earliest or direct fired method the magnesium chloride solution is sprayed into gas fired chambers. The more re- cent submerged combustion method accomplishes evaporation by burning a carburated mixture of natural gas and air below the surface of a pool of magnesium chloride solution. In either case, direct contact with the hot products of combus- tion concentrates the solution to 35 percent mag- nesium chloride by weight. Direct heating is necessary because of the scaling tendency of the solution. In the fifth step the unwanted calcium is pre- cipitated from the solution by the closely controlled addition of magnesium sulfate. The treated liquor is held for 24 hours in an agitated tank to encourage crystal growth of the salt and gypsum. The adjusted evaporator product is then fil- tered, first tlu"ough Moore filters identical to those used earlier for the magnesium hydroxide filtra- tion, and then through plate and frame presses for a final polish. The seventh step of the process is evaporation of the filtered 35 percent magnesium chloride solu- tion to a concentration of approximately 50 per- cent. Open top, brick-lined steel boiling kettles heated by alloy steam coils are used for this purpose. In the next stage, the concentrated magnesium chloride liquor at a temperature of 170° C. is transformed into a solid suitable for feeding the electrolytic cells. The hot liquid is sprayed on 6 to 10 times its weight of previously dried solid in a horizontal rotary mixer, producing a white granular material containing abt)ut 68 percent magnesium chloride. This is dried with hot re- circulated air in a multi-shelf drier, similar in design to a HerreghofT furnace, and becomes a free-flowing granular cell feed of approximate composition MgClj.l.SHzO. Part of the dry granular material is returned to the rotary mixer and part is conveyed to the magnesium cells. The ninth step is electrolysis of the cell feed (Hunter 1944). The electrolytic cells used for this operation are bathtub shaped steel pots of approximately 2,500 gallons capacity, filled with a fused salt mixture consisting of 25 percent MgCU, 15 per(;ent CaClj, and 60 percent NaCl at 700° C. Graphite electrodes suspended in the bath serve as anodes; the pots and their internal baffles act as cathodes. Passage of a high am- perage, direct current between the electrodes and the pot decomposes the magnesium chloride of the bath to elemental magnesium and chlorine gas. Cell feed is added continuously to maintain the proper bath composition and level. The hot gaseous products are collected under a tightly fitting refractory cell cover, cooled, and piped to the hydrochloric acid plant. The molten mag- nesium metal rises to the top of the bath where it is trapped by inverted troughs and conveyed to the storage wells in the front of each cell. The metal is hand dipped from the cells three times daily and cast into the familiar 18-pound notched ingots. Each cell, operating at 60,000 amperes, produces approximately 1,200 pounds of magnesium per day having a purity in excess of 99.8 percent. No other refinement is necessary to meet the specifications for commercially pure magnesium. The final step of the process consists of con- verting the chlorine from the cells to hydrogen chloride by high temperature reaction with steam and natural gas in a regenerative furnace. A small amount of unreacted clilorine is reduced by the controlled addition of SO2 supplied by con- ventional sulphur burners. The hydrogen chlo- ride and the small amount of H2S04 are absorbed in water, and the resulting acid solution is re- cycled to the neutralizers for the reaction with Mg(0H)2 previously mentioned. Since process losses are inevitable, it is necessary to replenish the recycled hydrochloric acid to the extent of about one-half pound per pound of mag- nesium produced. This may be added as chlorine 158 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE to the gas stream entering the furnace or as hydro- chloric acid at the neutraUzers. The properties and uses of magnesium are well- known but warrant brief comment. It is the lightest structural metal commercially available. It is about one-fourth as heavy as iron and two- thirds as heavy as aluminum. When alloyed with small amounts of other metals, such as aluminum, zinc, and manganese, it has a high strength to weight ratio, it is easily fabricated, and it has good corrosion resistance. These properties make it advantageous for use in light weight structures and equipment such as air- planes, truck and trailer bodies, portable tools, hand trucks, ladders, and others too numerous to mention. The high place held by magnesium in the electromotive series of metals makes it out- standing for sacrificial anodes — in other words, sources of current for the protection of buried or submerged metal surfaces against corrosion. One of the more recently developed uses of magnesium is in the field of ferrous metallurgy. Small amounts of magnesium properly added to cast iron prior to pouring give a so-called "nodular cast iron" which has strength and ductility prop- erties similar to those of steel. The economic factors involved in the mag- nesium-from-sea-water operation are somewhat different from those of bromine. From an ocean- ographic or climatic standpoint, the location is not so critical. The sea water which must be processed per pound of magnesium is only one- twentieth as much as is required per pound of bromine. The water temperature has little effect on the magnesium recovery. More important is a location favorable to the supply of raw materials and power. The convenient availability of lime and abundant and inexpensive fuel and power are obviously essential for competitive operation. The process can achieve a recovery of 85 to 90 percent of the magnesium in sea water. The performance of each step represents a compro- mise between high efficiency and high capital cost, and the justifiable recovery must be calcu- lated for the conditions of each plant. The process has the inherent advantage that the majority of the materials can be conveyed by pumping. Most of the steps are continuous and subject to the benefits of automatic control. The quantities of sea water and oyster shells used in the process are large. In the Freeport plant (following quoted from Schambra, 1945, pp. 4, 6): "Sea water flows by tidal surge from deep water in the Gulf of Mexico, through the 40 ft. deep channel dredged into the Freeport harbor. Stone jetties at the mouth of the harbor prevent the surf and shore currents from wash- ing sand into the channel. One mile inshore from the harbor mouth, the plant intake withdraws the raw sea water at a depth of 25 ft. A concrete curtain wall holds back the surface water so that the suction opening is actually between —20.0 ft. and —30.0 ft. elevation. In waters of this locality, stratification of high and low density water occurs, even in the range of specific gravity of 1.000 to 1.026, the difference between fresh water and full strength sea water. The use of a curtain wall permits withdrawal of 80% to 90% full strength sea water when the surface may be nearly fresh water. Due to rains and fresh water intrusion from the Brazos River, the sea water at the intake averages 85% of full strength. At the intake, trash, marine plants, and small fish are removed by a triple screening . . . Four Worthington submerged-propeller axial-flow type pumps, each delivering 70,000 g. p. m., rai.se the sea water from a varying .sea level to a constant head at elevation 9.0 ft. Each pump dis- charges directly into a unique rotating barrel [Monel] screen . . . made up in wood-framed trays which are bolted to the steel barrel framework. Each tray is care- fully insulated from the barrel by rubber gaskets to mini- mize bi-metal electrolytic corrosion. Following the screens, the sea water is chlorinated con- tinuously to a residual of 0.2 to 0.5 p. p. m. free halogen. Growth of marine plants, barnacles, and oysters is pre- vented in this manner . . . Shell [used for the production of lime] is purchased from two dredging companies now working the oyster shell reefs in Galveston bay. Accu- mulated shells of dead oysters lie in irregular reefs in 1 to 17 ft. of water, with the thickness of the beds varying from 1 to .30 ft. There are millions of tons of usable shell in Galveston and Matagorda Bays alone. Extensive reefs are found off shore in the Gulf. Newly dredged shell contains mud and sand which are removed by washing on the dredge with sea water. The dredge W. D. Haden has a capacity of 350 tons per hr. of washed shell. Loaded barges of 800 tons capacity are removed by Diesel tug to the Freeport plant . . . The washed shell is fed either to the storage pile or directly to the kiln feed hoppers . . . Each kiln produces 150 tons of lime per day.' In conclusion, the large-scale recoveries of bro- mine and magnesium from sea water must not be regarded as merely incidents in the record of scientific progress of the last three decades. They are indicative of a pronounced trend toward using the seas for more of life's needs. It is natural that this should be so. The seas, covering three-fourths of the earth's surface and ' Reproduced with the permission of the American Institute of Chemical Engineers from the Transactions of the A. I. Ch. E,, vol. 41, No. 1, pp. 4, 6. GULF OF MEXICO 159 bordering upon every continent, represent a global source of supply. They are practically inexhaust- ible, for the total quantities of availal)le salts reach astronomical fijiurcs and are unquestionably increasing with the daily contribution of the rivers, while other mineral resources are being depleted. The handling of sea water by pumping is unques- tionably easier and cheaper than the majority of mining methods. The sea water has relatively stable chemical and physical properties, contrib- uting to constancy of the finished product. All these things, and more, lead to the inevitable conclusion that the record of past achievements and the vision of man's increasing dependency on the oceans will combine to stimulate the research activities of all the nations toward a more complete utilization of the tremendous resources of the seas. LITERATURE CITED Armstrong, E. F., and Miall, L. M. 1946. Raw materials from the sea. Brooklyn, N. Y., Chem. Pub. Co., 196 pp. Hart, P. 1947. Sea water bromine process cliemical control systems. Jour. Instrument Soc. Am. 2 (10) : 956-958. Hunter, R. M. 1944. The electrochemistry of the Dow magnesium pro- cess. Trans. Electrochemical Soc. 86: 21-31. KlRKPATRICK, S. D. 1941. Magnesium from the sea. Chem. & Metallurgi- cal Eng. 48 (11): 76-84. Klagsbrunn, H. a. 1945. Wartime aluminum and magnesium. Industrial and Eng. Chem. 37 (7): 608-617. SCHAMBRA, W. P. 1945. The Dow magnesium process, at Freeport, Texas. Trans. Am. Inst. Chem. Eng. 41 (1): 35-51. Seaton, M. Y. 1931. Bromine and magnesium compounds drawn from western bays and hills. Chem. and Metallurgical Eng. 38: 638-641. Stewart, L. C. 1934. Commercial extraction of bromine from sea water. Industrial and Eng. Chem. 26 (4): 361-369. Stine, C. M. a. 1929. Recovery of bromine from sea water. Industrial and Eng. Chem. 21 (5): 434-442. CHAPTER V PLANT AND ANIMAL COMMUNITIES PHYTOPLANKTON OF THE GULF OF MEXICO By Charles C. Davis, Western Reserve University As late as 1944 Dr. B. F. Osorio Tafall, writing concerning the interesting (iistribution of Bid- dulphia siJiensis Greville, found it necessary to speak of "La carenzia absoluta do estudios sis- temjiticos del plancton en aiios anteriores en las aguas del Caribe y del Golfo de Mexico ..." It is true still that little has been done on tax- onomic studies of Gulf of Mexico phytoplankters, and even fewer ecological studies have been made. The earliest published observations on the phytoplanktbn of the Gulf of Mexico appear to be those of Alexander Agassiz (1888) who men- tioned, in very general terms, the occurrence of Coccolithophoridae in the central regions of the Gulf. He mentioned more specifically the occur- rence of large chains and patches "of dh-ty yellow color" of the filamentous blue-green alga he identified as "probably" the same as the Tri- chodesmium erythraeum that is so famous in the Red Sea. Dr. Drouet of the Chicago Natural History Museum has identified the most common filamentous blue-green alga from Florida and Texas marine waters as Skujaella [Trichodesmium] thiebauti (Davis, 1950), and probably this is the species referred to above. Agassiz also referred to the occurrence everywhere, but in small patches only, of a species of Sargassum. From the time of Agassiz' (op. cit.) early super- ficial report until 1937 there were no detailed reports on Gulf of Mexico phytoplankters other than individual species records such as that of Taylor (1928) who listed the occurrence of Skujaella [Trichodesmium] thiebauti and of two common pelagic species of Sargassum (S. natans and S. fludtans) near or at the Tortugas Labora- tory. In addition, there were certain other studies made at the Tortugas Laboratory which, however, appear not to have been reported in detail. Thus, Grave and Burkenroad (1928-29) reported diatoms among those plankters that were abundant or that occurred regularly, while Conger (1925-26, 1926-27, 1927-28, 1928-29, 1937-38, 1938-39) briefly summarized his work on diatoms, 259534 0—54 -12 some of them plaiiktonic. Conger (1926-27) found that the diatom flora of the Dry Tortugas was sti'ongly local in character and that it had its nearest affinities to the West Indian flora. His (Conger 1937-38) investigations showed that there was Tittle change of quantity or kinds of the planktonic diatoms during his 10-week (sum- mer) stay at the laboratory except that there was "some slight increase" in abundance after a period of heavy wind. He emphasized that the region of the Dry Tortugas is a silica-poor region and that Si is a limiting factor there in diatom pro- duction. For comparative purposes he (Conger 1927-28) also studied some samples from Tampa Bay and found the water rich with plankton. He stated that the "richness of this area in diatoms may account for the abundance of marinelife there." Riley (1937, 1938) studied phy to plankton pro- duction in Gulf waters, largely through the plant pigment method. In his former report (Riley 1937) he considered the influence of the Mis- sissippi River drainage upon the phytoplankton in the northern portion of the Gulf. A number of stations were established from Galveston to Mobile and south to the thousand-fathom line (fig. 44). Analyses were made of salinity, phos- phate, copper, plant pigments, and weight of organic matter. It was found that the water of the Mississippi River itself was very rich in phosphates and that this water spread over the surface of the northern Gulf both to the east and to the west but especially to the east in the direc- tion of Mobile (fig. 45). Plant pigments were highest in the waters richest in phosphates (fig. 46). Samples obtained from completely fresh river water contained higher values for plant pigments than elsewhere, but these values were not especially high for fresh waters. This in- dicated that the high turbidity of the river water was a deterrent to phytoplankton growth, for nutrient conditions were especially favorable for phytoplankton production. Analyses in the open Gulf showed typically low values. 163 164 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE _ 1 1 1 1 1 1 1 1 1 _ """ n vwt. / ^O^';:^^^^^''^^^^^'^^''^^ — "::^^^€iS:4. ' — 2^^ o<««* ^'^^ ' O >••' 9^»" Attn ^ 1 1 1 1 1 1 1 1 1 FiGUBE 44. — Stations established by Riley (1937) in the northern portion of the Gulf of Mexico. SURFACE PHOSPHATE CONTENTS MILLIGRAMS PER CUBIC METERS /^y J Figure 45. — Distribution of phosphates in the waters of the northern portion of the Gulf of Mexico. The later work by Riley (1938) was done in the Dry Tortugas at the end of the chain of the Florida Keys in the eastern part of the Gulf. Here the water was shallow and with no influence of land drainage of any consequence. Some samples were taken at the edge of the Gulf Stream, but most of them were taken at two regular stations between Loggerhead Key and Garden Key. Plankton samples were obtained by sieving 400 liters of water through a No. 20 silk net, and a second set of samples was obtained by filtering from 3 to 10 liters through a Whatman No. 2 filter paper. Part of each net sample was studied for number of animals present, for plankton weight, and for organic material weight, while the remainder was studied for the quantity of plant pigments. It was found that the plant pigments of the net plankton constituted less than 2 percent of that occurring in the filtered samples. Thus, the mean value for the net plank- ton was 17 Harvey units per m.^, while the average for the total plankton was 924 Harvey units per m.', indicating a very high proportion of nan- noplankton. The total quantitj' of plankton GULF OF MEXICO 165 SURFACE CHLOROPHYLL CONTENTS H»«Vi» ONUS nn tlTER Figure 46. — Distribution of plant pigments in the waters of the northern portion of the Gulf of Mexico. was much less than that to be found in most higher latitudes, the net plankton being ap- proximately 1 percent of the spring bloom con- ditions in the English Channel. The total chlorophyll at the station that lay closest to Loggerhead Key (it was the less productive of Riley's two main stations) was only about 4 percent of the summer crop determined by the same author in Long Island Sound by similar methods. Riley (1938) also attempted to study produc- tivity and limiting factors in productivity by means of oxygen determinations in sea water samples that had been confined in white and dark bottles. To some of these, nitrates and phos- phates had been added. He found that in the waters of the Tortugas region the nitrates were more important than the phosphates as limiting factors in phytoplankton production. Parr (1939) made a quantitative study of pelagic species of Sargassum in the western North Atlantic, the Caribbean Sea, Cayman Sea, and the Gulf of Mexico. Samples were obtained by dragging a special net at the surface of the water while the Atlantis was traveling from station to station on hydrographic cruises. For each sample, the catch was sorted as to species and weighed on board ship. Within the Gulf of Mexico proper, a total of 26 samples was obtained during the spring months (February 16 to April 12) of 1935. To obtain these samples, the net was dragged through the water for 1,230.5 miles. Sargassum was not uniformly distributed in the Gulf. The outer portions of the Gulf had a very sparse population of the weed, whereas, the concentration in the inner portion was second only to that of the Sargasso Sea itself. Parr (op. cit.) calculated that within the region of abundance, which he thought to occupy about 90,000 square miles, the crop of Sargassum amounted to approximately 1 ton per square mile. The Sargassum crop, at the time of sampling in the Gulf of Mexico, was in very poor physical condition, the plants being small and moribund. The occurrence of the maximum in the inner portion of the Gulf, completely isolated as it was from the primary maximum in the Sargasso Sea by a wide expanse of Sargassum-poor water, agrees with the results of hydrographic work published by Parr (1935) and reported on else- where in this book, to the effect that there ap- pears to be no great volume of surface water floating from the Gulf of Mexico to Florida Strait during the period of examination. The nearly complete isolation of the Gulf maximum from the maximum of the Sargasso Sea is also em- phasized by the fact that the epizoan fauna in the two regions is very different. From his ob- servations. Parr (1939) believes, however, that the Gulf community is not a self-sustaining com- munity in the same way that the Sargasso Sea community is. He based this belief on the com- 166 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE paratively poor quality of the plants in the Gulf. In his investigation, Parr (1939) found that the taxonomy of Sargassum is very confused and that there are many variations which, however, merge into one another. He found that in the Gulf the form he designated as S. natans (I) composed 87 percent of the specimens with approximately 6.5 percent each for S. natans (VIII) and S. fluitans (III). Small quantities of S. natans (II) and S. fluitans (X) were also observed. The next paper to appear on the phytoplankton of the Gulf was written by Osorio Tafall (1944) who dealt, however, only with a single species, namely, with the diatom, Biddulphia sinensis Greville. He found this species in samples ob- tained near Tampico, Tamaulipas, Mexico. The species has an interesting distribution in the oceans of the world, but on the Atlantic Coast of the New World it had previously been described only from off the coast of South America. Osorio Tafall discussed the manner in which B. sinensis may have reached the waters of the Gulf of Mexico but was unable to come to any definite conclusions because of a lack of previous investigations of the phytoplankton of the Gulf. He thought it might be a relic of a previous flora, or that it might have been carried to the Tampico region from the North Sea on the hulls of boats, or that it might have been carried there by currents from its center of distribution off the east coast of South America. He favored the last-mentioned hy- pothesis and pointed out that if the hypothesis were correct the species would be widespread along the coasts south of Tampico, a matter easily determined by further investigation. The disastrous "red tide" of the southwestern coast of Florida in 1946 and 1947 stimulated considerable interest in the phytoplankton of the whole Gulf. It became painfully evident that all investigations of the phytoplankton bloom that was associated with the catastrophe were greatly hampered by the lack of previous knowledge of conditions in the Gulf. Red tide is being dis- cussed elsewhere in the present book (p. 173), and only those aspects that could not be adequately dealt with at that place wUl be discussed here. Davis (1948a) mentioned cases in which Gym- nodinium brevis Davis occurred in the plankton in very large numbers, up to 60 million cells per liter. The same author (1951) pointed out that in two of the samples under discussion this species constituted 99.28 and 98.99 percent of the total organisms present. Most of the other organisms were diatoms. Gunter et al. (1948), in addition to discussing the red tide as such, discussed other associated phenomena in the plankton cycle. Color changes of the water, as deciphered by these authors, are described in the section on the red tide. Gunter et al. (op. cit.) described in some detail other plankters, both animal and plant, associated with these changes. They summarized the sequence as follows (pp. 318-319): There was first the appearance of numbers of Gymno- dinium brevis mixed in with other normal plankton types, mostly diatoms . . . Locally, or over large areas there then appeared a "bloom" of Gymnodinium, and in these areas the mortality occurred. This was then followed by the decomposition of many dead organisms, with the consequent release into the water of much nutrient material. Bacteria and/or phytoplankton utilized this nutrient material, and then were themselves utilized, especially by the Copepoda, which consequently increased enormously in the plankton . . . The Copepoda devoured all the suitable diatoms, and left only the species of Rhizosolenia, which would be very difficult for the copepods to handle . . . Davis (1948b) described a plankton tow taken in Long Lake, a brackish-water tributary to Florida Bay. He mentioned naviculoid diatoms and Ceratium Jurca as being present but not abun- dant, and as being far overshadowed by large numbers of copepods.' Davis and Williams (1950) described a more extensive series of samples obtained from 28 lakes, bays, and sounds in the mangrove areas of southern Florida. All samples were obtained from brackish bodies of water in- cluding Florida Bay and bodies tributary to Florida Bay or directly tributary to the Gulf of Mexico. They made few identifications of phy- toplankters to species. Such forms as Rhabdo- nema, Skeletonema, and Ceratium were confined to those bodies of water that were most saline, while Coscinodiscus was much more abundant in such localities. On the other hand, Chaetoceros was not so greatly limited by salt content, though it did not occur in localities with less than 3.06 parts per thousand salinity. They found that desmids were confined to the freshest bay and that green algae and blue-green algae (with the exception of Skujaella thiebauti) were found only in those lakes and bays with the lowest salinities. Gonyaulax ' See article on zooplankton by H. B. Moore, pp. U7-172. GULF OF MEXICO 167 spinifera (?) occurred in vast swarms in many localities on the south coast (parts of Florida Bay and some of its tributaries) and in salinities ranging from 8.60 parts per thousand in Seven Palm Lake to 25.12 parts per thousand in Upper Terrapin Bay. In addition, Davis (1950) has dealt with phy- toplankton and zooplankton from various Florida marine waters. Many of the samples analyzed were taken in tlie Gulf of Mexico (as far out as 60 miles west of Anclote Light) and its inland tidal waters. A large proportion of the inshore and inland-water plankters was obtained coincident to the study of the red tide, and they were reported in more detail than was possible in Gunter et al. (1948). Davis (op. cit.) stated that: ". . . the plankton appears to be richer on the west coast [than on the east coast of the peninsula], and a number of important species were confined to west coast waters." He listed, among the plants, the following that were confined to the west coast: Baccilaria sp., Cerataulina sp., Hemiaulus sp., Gymnodinium brevis, Striatella sp., and Noctiluca scintillans. Joseph King (1950) also discussed both phj^to- plankters and zooplankters collected during 1949 from the west coast of Florida. He established a series of stations extending off shore to the 100-fathom line in the Fort Myers region, and these were visited several times. In addition, samples were obtained one or more times from certain other locations near the coast (fig. 47). He found that the waters in question were poor in plankton. Greatest plankton volumes were obtained at the station established over a 5- fathom depth of water. He observed a sporadic bloom of the blue-green alga, Trichodesmium [Skujaella] erythraeum, which at the height of growth formed yellowish flocculent windrows on the surface. He found diatoms to be numerous, especially in the inshore waters, the most abun- dant being Coscinodiscus, Skelefonema, Navicvla, Nitzschia, Surirella, Chaetoceros, and Rhizosolenia. Fresh-water green algae, including desmids, were encountered at two of the stations located in estuaries. Dinoflagellates were abundant in his samples only on three occasions, all of them in inside waters (twice in Sarasota Bay and once in the estuary at Fort Myers). In each of these three cases there was a dense bloom of Gonyaulax, forming scattered streaks and patches of a reddish- brown film over the surface of the water. Mullet appeared to be feeding voraciously on this bloom. The species of Gonyaulax, or else the conditions in which it was living, may have beea very differ- ent from those described by Connell and Cross (1950) in Offatts Bayou near Galvestoa, Texas, for in the latter case the regularly occurring red water of the bloom of Gonyaulax was accompanied by fish mortality and foul odors. Gunter (1951), on the other hand, believes that the occurrence of Gonyaulax in Offatts Bayou is only incidental to the mortality and that the mortality was directly caused by a seasonal stagnation and putre- faction accompanied by oxygen depletion. This view also had been previously expressed by Gunter (1942). King (op. cit.) found that in the offshore waters of the open Gulf all forms of phytoplankton were very scarce. Several diatom genera were rep- resented: the most common were Chaetoceros, Rhizosolenia, and Thalassiothrix, but none oc- curred in any abundance. From the above it is fairly obvious that the greatest immediate need in the field of phyto- plankton research in the Gulf of Mexico is a thoroughgoing quantitative study of the seasonal distribution of the phytoplankton in all portions of the Gulf. True as this statement is for the net plankton, it is far more true for the nannoplank- ton which has hardly been considered at all except to a limited extent in the studies of Gymnodinium brevis and the red tide (Davis 1948a, 1951; King 1949). Also needed are (1) further production studies such as those attempted on a small scale by Riley (1938), (2) detailed studies of the phytoplankton- zooplankton interrelationships in the Gulf, a field practically untouched by previous investigators, (3) studies of the nutrient needs of the more abundant individual species, and (4) studies of the utilization of the Gulf phytoplankton by benthic and nektonic animals. 168 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 84» 63* 82" ei«» Figure 47. — Stations established by Joseph King in Florida west coast waters. GULF OF MEXICO 169 BIBLIOGRAPHY Agassiz, Alexander. 1888. Three cruises of the U. S. Coast and Geodetic Survey steamer Blake. Bull. Mus. Comp. Zool. Harvard College 14: 1-814. Conger, Paul S. 1925-26. Diatom investigations of the Tortugas during June, 1926. Carnegie Inst. Washington Yearbook 25: 240-241. 1926-27. Diatom research at the Tortugas Laboratory. Carnegie Inst. Washington Yearbook 26: 218. 1927-28. Diatom research at the Tortugas Laboratory, 1928. Carnegie Inst. Washington Yearbook 27: 271-272. 1928-29. Diatom research at the Tortugas Laboratory, 1929. Carnegie Inst. Washington Yearbook 28: 283. 1937-38. Diatom investigations. Carnegie Inst. Wash- ington Yearbook 37: 89. 1938-39. Diatom investigations. Carnegie Inst. Wash- ington Yearbook 38: 223. CoNNELL, C. H., and Cross, J. B. 1950. Mass mortality of fish associated with the pro- tozoan Gonyaulax in the Gulf of Mexico. Science 112 (2909): 359-363. Davis, Charles C. 1948a. Gymnodinium brevis sp. nov., a cause of dis- colored water and animal mortality in the Gulf of Mexico. Bot. Gaz. 109 (3) : 358-360. 1948b. Notes on the plankton of Long Lake, Dade County, Florida, with descriptions of two new cope- pods. Quar. Jour. Florida Acad. Sci. 10 (2-3) : 79-88. 1950. Observations of plankton taken in marine waters of Florida in 1947 and 1948. Quar. Jour. Florida Acad. Sci. 12 (2): 67-103. 1954. The marine and fresh-wat«r plankton. Michigan State College Press. (In press.) and Williams, R. H. 1950. Brackish wats of Mexico, 1920-26, and Flora of Yucatan, 1930. Pertaining to smaller areas but often con- taining much valuable information on the distribu- tion of maritime plants are: Small's Flora of the Florida Keys, 1913, Molir's Plant Life of Alabama, 1901, Lowe's Plants of Mississippi, 1921, Lloyd and Tracy's The Lisidar Flora of Mississippi and Louisiana, 1901, and Cory and Parks' Catalogue of the Flora of the State of Texas, 1938. Floristic and ecological treatments of still more limited areas are referred to imder the several plant communities. The marine and strand flowering plants of the Gulf are best considered in the natural groupings in which they usually grow. There are four such major plant communities: submarine meadow, mangrove swamp, salt marsh, and sand-strand vegetation. SUBMARINE MEADOW Least collected and studied of all the Gulf plants are the marine spermatophytes or sea-grasses. These aquatic flowering plants, members of the Hydrocharitaccae and Zannichelliaceae rather than true grasses, have received some attention in the waters around the Dry Tortugas. Bowman (1916, 1918) and Taylor (1925, 1928) have con- tributed original observations on the ecology and morphology of species in that area. For other parts of the Gulf information about them is scanty (Howe 1918; Davis 1940; Hotchkiss 1940; Ste- phenson and Stephenson 1950). Several authors (Ascherson 1906; Ostenfeld 1914, 1926-27; Setchell 1920, 1934a) have discussed their world distribu- tion, and Balfour (1878), Rydberg (1909), and Bowman (1916) have contributed papers on their morphology. The most thorough taxonomic treat- ments of the marine spermatophj'^tes are included in Ascherson and Graebner's (1907) monograph of the Potamogetonaceae in Das Pflanzenreich and Ascherson and Giirke's (1889) study of the Hydrocharitaccae in Die Naturalichen Pflanzen- familien. Descriptions and keys for the identifi- cation of Gulf species are available in Small (1933) and Muenscher (1944). More species of marine flowering plants are found in the Gulf of Mexico and Caribbean Sea than anywhere else in the Western Hemisphere. Li the waters around the Florida Keys grow five species belonging to two families: Diplanthera wriyhtii (Aschers.) Aschers. and Syringodium Jiliforme Kutz., manatee-grass, of the Zoster- aceae, Thalassia testudinum Konig, turtlegrass, 193 194 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Halophila baillonis Aschers. antl H. engeimannii Aschers. of the Hydrocharitaceae. Halophila aschersonii Ostenf., as well as the above, is found in the Caribbean and is reported as far south as Recife, Brazil. The widespread Ruppia maritima L., widgeongrass of the Potamogetinaceae and Zannichellia palustris L., horned-pondweed of the Zanichelliaceae, though usually not marine, are found in brackish waters along the Gulf coasts. Only two other genera of marine flowering plants are reported from the New World. Zostera marina L., eelgrass of the Zosteraceae is found in shallow, quiet waters of the Pacific and Atlantic coasts of North America, reaching as far south along the latter as North Carolina. Other species of this genus have been collected on the coasts of Chili and Uruguay (Setchell, 19.34b, 1935). Phyl- lospadir scouleri Hook, and P. torreyi Wats., also of the Zosteraceae, grow along the Pacific coast near low-tide mark where they are exposed to strong wave action. The Gulf and Caribbean sea-grasses are limited in habitat largely to soft marl, mud, or sand in warm, clear, shallow marine water. Thalassia, Diplanthera, and Syringodium form extensive sub- marine meadows or beds in shallow water of bays and lagoons, seldom being exposed except at the lowest tides. These plants extend also into deeper water, having been dredged in the Dry Tortugas area to 11 meters (Taylor 1928). Generally, the species of Halophila thrive on calcareous bottoms in much deeper water. H. baillonis has been dredged from 5.5 to 29.3 meters but more com- monly in 14 to 18 meters and H. engeimannii in still deeper water, 4.6 to 73.2 meters and one estimated depth of 91 meters (Taylor 1928). H. aschersonii was dredged with H. baillonis along the south shore of Puerto Rico from a depth of 18 meters (Howe 1915). These marine plants are usually associated in southern Florida waters with such marine algae as Acetabulum, Caulerpa, Gracilaria, Halimeda, Hypnea, Penicillus, Poly- siphonia, Sargassum, and Udotea. Thalassia espe- cially furnishes a good habitat for such algal epiphytes as Melohesia farinosa Lamouroux. Ruppia is often abundant in shallow water of enclosed bays, tidal estuaries, or other areas where the water is less saline. The distribution of sea-grasses in the Gulf is poorly known. All five Gulf species grow along the northwestern coast of Cuba and around the Florida Keys. All of these but H. baillonis have been collected in the Tampa Bay region by the writer and on the northern Gulf coast of Florida by others. Thalassia, Diplanthera, and Halophila engelmanii are present in the coastal waters of southern Texas. Several of the species must occur along the Mexican coast. The apparent rarity of marine spermatophytes except Ruppia on the northern Gulf coast between Bay County, Florida, and Aransas County, Texas, may be significant. Perhaps the silt and fresh water dumped into the Gulf by the Mississippi and other large rivers are involved. Outside the Gulf and Caribbean, Diplanthera has been collected on the coast of North Carolina and Diplanthera, Thalassia, Syringodium., and H. baillonis on Bermuda shores. Two species, Tha- lassia testudinum. and Diplanthera wrightii have been collected on both the Caribbean and Pacific coasts of the Isthmus of Panama, possibly indi- cating a former water connection across the isth- mus. Close relatives of species in each of the four Gulf genera are found in the Indo-Pacific region. In all, approximately 40 species of sea grasses are known, and the largest concentrations of these occur in tropical waters of the Indian Ocean, western Pacific Ocean, and the Red Sea. MANGROVE SWAMP Most conspicuous of the plant communities of the Gulf coast is mangrove swamp. There is much literature about this swamp-forest or swamp- thicket that is so characteristic of tropical coasts around the world. Davis (1940) has made a thorough study of mangroves in Florida with emphasis on their ecology and geologic role. Their importance as land-biulders in Florida has been emphasized, perhaps overemphasized, by several writers (Curtiss 1888; Sargent 1893; Pol- lard 1902; PhiUips 1903; Vaughan 1910; Harsh- berger 1914; Simpson 1920). The embryology of Rhizophora mangle L. has been studied by Cook (1907), the physiology by Bowman (1917), and the dispersal and establishment by Egler (1948). Dispersal of Rhizophora and other mangroves has been considered in some detail by Crossland (1903), Guppy (1906, 1917), Ridley (1930), and other biologists. In addition to some of the above papers good accounts of mangrove swamp on Gulf coasts have been written by Harper (1927) and Davis (1942, 1943). Publications describing GULF OF MEXICO 195 mangrove swamp in other regions are listed in tlie l)il)liography for Jamaica (Steers et al. 1940), tlie Virgin Islands (B0rgescn 1909; Raunkiaer 1934), Micronesia (Fosberg 1947), Indo-Malaya (Schimper 1891), and for the tropics in general (Schimper and Faber 1935) and (Warming 1909). The three widely distributed mangroves of Gulf shores are RMzophora mangh L., the red mangrove, Avicerinia nitida Jacq., the black or honej^ mangrove, and Laguncularia racemosa (L.) Gaertn. f., the white mangrove. These species grow mixed together or in distinct zones. All are noteworthy for their ability to withstand varying concentrations of salt in the sea water and soil solution in which their roots are buried. They are apparently facultative halophytes, for seed- lings of each have been grown in fresh soil and water for. at least 6 years (Davis 1943). Rhizo- phora may be readily identified by its peculiar system of branching prop-roots extending down- ward like stilts from the trunks and lower branches and by the less common flexible air roots dropping from the upper branches. It produces seeds which germinate while attached to the tree to form club-shaped hypocotyls commonly 30 centimeters long. These hang by the two cotyledons from the ovate fruit until they plummet into the water or mud below the tree. Avicennia produces an abundance of odd, pencil-like pneumatophores rising through the mud from the shallow hori- zontal roots. The flowers produce abundant nectar that is manufactured by bees into excel- lent honey. The fruit is ellipsoid, flattish, and 3 to 5 centimeters long. Laguncularia produces fewer and smaller pneumatophores than Avicen- nia. It may be recognized by its fleshy, elliptical leaves and small, ribbed fruit. In addition to the three mangroves several plants are characteristic of mangrove swamps. A relative of Laguncularia, Conocarpus erecta L., called the buttonwood or button mangrove be- cause of its small, button-like or alder-like clusters of flowers and fruit, grows inland from the other mangroves on harder ground that is usually not flooded by normal tides. Its trunks are loose- barked, twisted, and frequently prostrate. It is a common plant also in dune hammocks. Two vine-like shrubs of the Leguminosae, Caesalpinia crista L., nicker-bean, and Dalbergia ecastophyllum L., coin-vine, often sprawl over the mangrove 259534 O— 54 14 thickets on their landward margin. Both species are more shrub-like when growing on the dunes. Another vine, of the grape family', Cissus incisa (Nutt.) Desmoul., marine-ivy, climbs tlirough the crowns of tlie mangroves and sends down to the ground long, cord-like aerial roots. Batis maritima L., saltwort, a succulent-leaved, spread- ing or prostrate shrub, is frequently the only species accompanying the mangroves on wet mud. On sandy or marlj^ shores other succulent halo- phytes, such as Salicornia virginica L., glasswort, Sesuvium portulacastrum L., sea-purslane, and Suaeda linearis (Ell.) Moq., sea-blite, and several grasses may cover the groimd on the inner margin of the mangrove thickets. On drier ground landward from the mangrove thickets several shrubs and herbs associated with Conocarpus form an open thicket transitional to shore hammock or pineland. Some of the plants of this transitional zone, flooded by salt water only during spring and storm tides, are Borrichia frutescens (L.) DC, sea-oxeye, Lycium carolini- anum Walt., Christmasberry, Bumelia celastrina HBK., saffron-plum, Coccoloba uvifera (L.) Jacq., sea-grape, Maytenus phyllanthoides Benth., and Sophora tomentosa L., necklace-pod. In addition to these, all found m the Tampa Bay region of central Florida, several other tropical associates of Conocarpus in the mangrove-hammock transition zone are found m the more tropical part of southern Florida and the Florida Keys. These are Bor- richia arborescens (L.) DC, sea-oxeye, Rhab- dadenia biflora (Jacq.) Muell. Arg., rubbervine, Capparis flexuosa L., Achras emarginata (L.) Little, wild dilly, Jacquinia keyensis Mez., Joe- wood, Torrubia longifolia (Heimerl.) Britt., blolly, Erythalis fruticosa L., Acrostichum aureum L., leather fern, and several cacti, Acanthocereus floridanus Small, dildoe, Harrisia simpsonii Small, prickly-apple, and Opuntia dillenii (Ker) Haw, prickly-pear. The loose bark of Conocarpus fur- nishes a foothold to several epiphytes including Epidendrum tampense Lindl., an orchid, and various species of Tillandsia, the air-pines. Zonation in mangrove swamps appears to be correlated with water level and degree of salinity of the water and substrate and in some areas with tidal fluctuations. Each species, however, may be quite variable in relation to these factors. Rhizophora may form colonies well off shore on 196 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE shoals or may occur as scattered plants in brackish or even fresh water well inland from the coast. Generally, it grows on shores or low islands where the substrate is covered by tidal water even at low tide. The Avicennia zone which commonly includes Laguncularia and various salt-marsh plants is flooded, at least in its outer part, by salt or brackish water at high tide. When Lagun- cularia forms a distinct community, it is usually inland from Avicennia. Conocarpus and its asso- ciates of the transition zone are seldom flooded. The mangroves grow on peat, muck, marl, sand, and rock. They are killed by severe frosts. Economically they have been of little importance except in certain areas where they have been used for fuel, pilings, and a source of tannin. It is contended by some that mangrove swamps protect shorelines, build up soil levels along the coast, extend shorelines, and form new islands, but it is doubtful that the mangroves play a very large part in land building. Mangrove swamp in the Gulf region reaches its greatest development along the southwestern coast of Florida in the Ten Thousand Islands area. There mangroves of all three species, some more than 25 meters tall and 2 meters m circumference (Davis 1940), grow in the extensive strand and estuary swamps. Mangrove swamp to a depth of several miles covers the western and southern tip of peninsular Florida from Cape Romano to Cape Sable and thence eastward to Biscayne Bay. Mangroves also cover the numerous small keys in Florida Bay and fringe the larger Florida Keys south and west to the Marquesas. North- ward along both sides of Florida less well developed mangrove swamp, perhaps better described as mangrove thicket, extends to the Cedar Keys area on the Gulf coast and Cape Canaveral or farther north on the' Atlantic coast, mostly in lagoons, bays, and estuaries. As the mangroves become smaller and more scattered on the northern Gulf coast, salt marshes become more extensive. Killing frosts apparently are the deciding factor in the competition between the species comprising the two vegetation types. In Florida mangrove areas are estimated to total more than a thousand square miles (Davis 1940). The botanically less known Gulf coasts of Cuba and Mexico are fringed in the appropriate habitats with mangrove swamp. According to Leopold (1950), mangroves extend northward along the Mexican Gulf coast to southern Tamaulipas. Along the northern shores of the Gulf from Cedar Keys in Florida to southern Tamaulipas typical mangrove swamp is absent, and mangrove species are represented only by the more hardy Avicennia which gi'ows, where present, mostly as scattered shrubs with Batis and other salt-marsh associates. Mangrove swamp is found throughout the tropics along low-lying shores and estuaries that are protected from direct wave action. Although it is best developed on mud and marl, it is present also on sand and even rock wherever crevices permit the seedling mangroves to gain a foothold (Crossland 1903). Oriental mangrove swamps are similar to those of the American and West African shores except that there are many more species of Oriental mangroves. Although few in number the American mangroves are widely distributed. Rhizophora mangle, Avicennia nitida, and Laguncularia racemosa are all found on the tropical coasts of West Africa as well as on botl- Pacific and Atlantic shores of tropical America. The floating seedlings or fruits of all three remaui buoyant and alive in salt water for several months (Guppy 1917) and are thus well-adapted to long distance dispersal by ocean currents. Several of the plants associated with them on the Gulf coasts, such as Caesalpinia crista, Sophora tomen- tosa, and Acrostichum aureum, range even more widely in the tropics. SALT MARSH Salt marshes of temperate shores have received perhaps even more attention from botanists than mangrove swamps of tropical shores. Thos along the Gulf coast have not been neglected Penfound and Hathaway (1938) have made ? very thorough study of marshes in southern Louisiana. Other botanists who have publishe on salt marshes of the northern Gulf shores a)- Mohr (1901), Lloyd and Tracy (1901), Cock (1907), and Penfound and O'Neill (1934). Harsh- berger (1914), Harper (1927), and Davis (1940, 1943) have described salt marshes and salt flat;- along the Florida Gulf coast. The salt marshes along the Atlantic coast of North America arc similar in many respects, and have been weL described by Kearney (1900, 1901), Harshberger (1909), Johnson and York (1915), Conard (1935), and Chapman (1940a, 1940b). GULF OF MEXICO 197 Salt marshes are best dovoloped along the more protected, temperate shores of the northern part of the Gulf of Mexico. There extensive marshes of salt-tolei-atiiifr species of tlowerinj; plants cover the tidal shores of the estuaries, bays, and lagoons. According to Griffitts (1928) there are 5,600,000 acres of salt marshes in the South Atlantic and Gulf States, of which 3,381,500 are in Louisiana, 680,000 in Florida, 315,000 in Texas, 34,000 in Alabama, and 26.500 in Mississippi. Louisiana possesses almost one-half of the total salt-marsh acreage in the LInited States. The dominant species in these marshes are Spartina alterniflora Loisel., smooth cordgrass, and Juncus roemerianus Sclieele, black rush, each commonly forming extensive and exclusive col- onies. Several other grasses or grasslike plants, however, are often found in association with them. These are Distichlis spicata (L.) Greene, saltgrass, Spartina patens (Ait.) Muhl., salt-meadow cord- grass, Spartina spartinae (Trin.) Merr., Scirpus robusfu.s Pursh, salt-marsh bulrush, and Fim- bristylis castanea (Michx.j Vahl, a sedge. Showy- flowered plants like Limonium carolinianum. (Walt.) Britt., sea-rosemary, Solixiago semper- I'irens L. var. meiicana (L.) Fern., seaside golden- rod, Pluchea purpurascens (Sw.) DC, salt-marsh fleabane. Aster exilis EU., A. suhulatus Michx., and ^4. tenuijolius L., the salt-marsh asters, and Borrichia frutescens (L.) DC, sea-oxeye, give some color to the marshes though they are seldom abundant. On wet, saline flat areas which are near high tide-mark the vegetation is more open. There, sometimes with scattered and dwarfed specimens of Avicennia nitida L., black mangrove, and several plants, such as Distichlis, Borrichia, and Limonium, are found the peculiar halophytes with succulent stems or leaves, Batis marilima L., saltwort, Salicornia inrginica L. and S. bigelovii Torr., glassworts, Suaeda linearis (Ell.) Moq., sea-blite, Sesuvium portulacastrum L., sea-purslane Philoierus vermicularis (L.) R. Br., beach-carpet, and Bacopa monnieri (L.) Pennell, marsh-hyssop. With these grow a few species with showier flowers: Sabatia stellaris Pursh, sea-pink, Gerardia maritima Raf., false-foxglove, and two vines, Ipomoea sagittata Cav. and Cynanchum palustre (Pursh) Heller. On slightly higher ground these herbs or small shrubs give w&y to a thicket of taller shrubs consisting mostly of Iva frutescens L., marsh-elder, Baccharis halimifolia L. and B. anyustijoiia Michx., groundselbushes. Farther south along the Florida Gulf coast from Tampa Bay to Key West the salt maishes become much less extensive due to competition from the mangroves. Salt-marsh plants there generally form an understory in the Avicennia zone of the mangrove swamps or predominate in the transition zone between the mangroves and non-halophytic vegetation. Characteristic of this southern P'lorida coast, especially on Cape Sable, are the salt flats. These level expanses of hard- packed sand or marl or of limestone rock are flooded by high tides. Thej' support a sparse vegetation of species listed above for the open salt marsh with the addition of several other common plants like Monanthochloe littoralis En- gelm., key grass, Sporobolus virginicus (L.) Kunth, drop-seed, Borrichia arborescens (L.) DC, sea- oxeye, Flaveria linearis Lag., Conocarpus erecta L., button wood, and its other woody associates listed under mangrove swamps. In the marshlands of southeastern Louisiana Penfound and Hathaway (1938) found gradual changes in the flora from strictly salt-water to strictly fresh-water habitats. They noted that many marsh species have a wide range of toler- ance for the salt factor and are found in brackish marshes as well as in salt-water or fresh-water marshes. Most of the salt-marsh species listed previously occur also in brackish water, and many fresh-water marsh plants are found in slightly brackish water. Some of these plants of brackish marshes are Typha domingensis Pers. and T. latijolia L., cattails, Spartina cynosuroides (L.) Roth, salt-reed grass, Phragmites communis, Trin., common reed, Scirpus californicus (C A. Meyer) Britt. and S. chilensis Nees & Mey., bulrushes, Sagittaria lancifolia L., arrowhead, and Alternanthera philoxeroides (Mart.) Griseb., alli- gator-weed. The last-mentioned plant is often a pest in the bayous and ditches of southern Louisi- ana. Another bad pest of fresh waters, Eichornia crassipes (Mart.) Solms, water-hyacinth, although often floated downstream into salt water, will not tolerate salt, and soon dies in even slightly brackish water (Penfound and Earle 1948^. In southern Florida the transition from salt marsh or mangrove swamp to nonlialophytic types of vegetation is equally gradual or very abrupt. Where salt marsh is transitional between man- 198 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE grove swamp and fresh-water prairie the brackish marsh zone is very wide. Dwarfed and scattered specimens of Rhizophora mangle L. grow inland along the rivers running from the Everglades and in the wet prairies where the water has little or no salt content. There it may be associated with Cladium jamaicensis Crantz, sawgi-ass, Typha domingensis Pers., cattail, Sagiftaria lancifolia L., arrowhead, Acrostichum danaeae folium Langsd. & Fisch., leather fern, and Annona glabra L., custard- apple. Similarly, where large rivers flow into the Gulf there are along the estuaries wide areas of brackish marshes transitional between the coastal salt marshes and fresh-water marshes and swamps. Where salt marsh abuts upon pineland, as in the Tampa Bay region, a difference of 30 centimeters in ground level brings an abrupt change in the physiognomy of the vegetation. The narrow zone of transition is often marked by a thicket of Myrica cerifera L., waxmyrtle, several species of Baccharis, groundselbushes, and Sabal palmetto (Walt.) Todd., cabbage palm. There are no salt marshes on the Cuban Gulf coast. Many of the American salt-marsh species, however, grow mixed with tropical species in the mangrove swamps or on low-lying beaches. Al- though the coastal vegetation of Mexico is poorly known, the same relationship probably exists be- tween salt-marsh plants and mangroves from southern Tamaulipas to Yucatan as on the south- ern Gulf coast of Florida and Cuba. The Yucatan coast possesses such salt-marsh or salt-flat plants as Distichlis, Monanthochloe, Spartina, Sporobolim, Fimbristylis, Philoxerus, Salicornia, Suaeda, Batis, Sesuvium, Baccharis, and Borrichia, as well as the mangroves and many associated plants. Salt-marsh plants live under most difficult con- ditions: high salt content in the soil solution, poor aeration resulting from the poor drainage, recur- rent submersion and exposure, and full insolation. Only species with a wide range of tolerance to these conditions can survive. Marsh height, tidal submergence, and salinity of the soil solution appear to be the most important factors in pro- ducing zonation in salt marshes. Spartina alterni- flora Loisel. withstands the deepest flooding. It is also, with Distichlis spicata, Juncus roemerianus , Batis, Salicornia, and the other succulent halo- phytes, apparently the most salt-resistant. Uphof (1941) has reviewed the literature on halophytes. SAND-STRAND VEGETATION The flowering plants of sandy shores are not strictly aquatic, yet they are too conspicuous and too abundant along Gulf coasts to omit from this treatment. Most thoroughly studied and de- scribed are the Florida beaches. Webber (1898), MUlspaugh (1907), Harshberger (1914), Bowman (1918), Simpson (1920), Harper (1927), Davis (1940, 1942, 1943), and Kurz (1942) have de- scribed the beach vegetation of the Florida Gulf coast. Strand vegetation along the northern Gulf coast has been treated by Mohr (1901), Lloyd and Tracy (1901), Cocks (1907), Lowe (1921), and Fenfound and O'Neill (1934). Except for the addition of more tropical species and the dropping out of more temperate species, the strand flora of Yucatan, Cuba, and other West Indian islands is very similar to that of southern Florida. This similarity is readily apparent from the descriptions of the beach vegetation of Yucatan (Bequaert 1933; Lundell 1934), Cuba (Uphof 1924; Seifriz 1943), Puerto Rico (Cook and Gleason 1928), and the Virgin Islands (B0rgesen 1909; Raunkiaer, 1934). Beach and dune vegetation along the At- lantic Coast of North America is described by Kearney (1900, 1901), Harshberger (1900), and Conard (1935). General treatments of strand vegetation in other parts of the world can be found in Schimper (1891), Schimper and Faber (1935), and Warming (1909). Sandy shores of the Gulf coast show as definite a zonation as salt marshes and mangrove swamps. Costing (1945) attributes this zonation to the tolerance to salt spray of the various coastal dune plants. The community is definitely a halophytic one. Due to vigorous wave action few plants survive on the lower beach. The pioneers of wet or shifting saline sands are found on the upper beach and the fore dunes. In the Tampa Bay region of the Florida coast the most abundant strand species are Sesuvium portulacastrum L., sea-purslane, Sporobolus virginicus (L.) Kunth, drop-seed, Atriplex arenaria Nutt., beach orach, Cakile edentula (Bigel.) Hook., sea-rocket, Helio- tropium curassavicum L., seaside heliotrope, Phi- loxerus vermicularis (L.) R. Br., beach-carpet, Iva imbricata Walt., beach-elder, Uniola paniculata L., sea-oats, Euphorbia buxifolia Lam. and E. ammannioides HBK., spurges, Ipomoea pes- caprae (L.) Sweet and /. littoralis (L.) Boiss., GULF OF MEXICO 199 railroad vines, Scaevola plumieri Vahl, beach berry, Andropogon glomeratus (Walt.) BSP., bunehgrass, Cenchrtis pauciflorus Benth., sandbur, Croton punctafus Jaeq., silverleaf, Oenothera humi- fusa Nutt., seaside evening-primrose, and Helian- thv,ments and Slielford (1939). Since Mya is absent from Gulf waters and Macoma sparsely scattered, this terminology has little meaning. To think of oyster reefs as isolated patches in extensive clam beds is to overlook the influence of oysters in changing the bottom of the bays and the conditions of life for the clams. The clam beds, where they may occur, might better be considered as fragmented by the oyster reefs. The formation of oyster reefs was studied by Grave (1905) who proposed a theory of the forma- tion of oyster reefs transversely across bays. This theory still remains the best explanation for this characteristic placing of oyster reefs. See figure 52 for a sampling of typical examples, including some studied by Grave.' As may be seen from the figure, not all reefs are transverse; some are parallel to the main currents. The typical oyster reef on the Gulf coast is, in cross section, a low mound with a high center, or "hogback," which is occupied by loose dead shells with the live oysters on the sloping shoulders. These reefs occur on muddy bottoms widely dis- tributed in bays of lower salinities and more or less restricted to the upper ends of those bays which are subject to the invasion of higher salini- ties tlirough the passes from the Gulf during periods of low rainfall and decreased run-off. A natural reef is usually oval or spindle-shaped or is a narrow bar extending from the shore. Al- though reefs in Texas have been badly cut up in recent years by artificial channels and mudshell dredging so that the original pattern is now ob- scured, the usual location of the reefs is such that their long axes are at right angles to the prevailing currents of the bays. Many of these reefs can be studied in the various coastal charts, and details of the more important oyster reefs of the Gulf waters will be found in the old survey papers of Gary (1906), GaltsofT (1931), Moore (1899, 1907, 1913a, 1913b), Moore and Danglade (1915). Ecological accounts will be found in Pearse and Wharton (1938), Archer (1947, 1948a, 1948b), Puffer and Emerson (1953, pp. 164-173). ' The biology of the oyster of the Oulf coast and the oyster reefs of the Gulf of Mexico are discussed in detail in chapter XV of this book in articles by Philip A. Butler, p. 479, and W. Armstrong Price, p. 491. Gulf coast oyster communities differ from those of Chesapeake Bay and more northern waters in lacking predacious starfish, and the Atlantic oyster drill, Urosalpini, is replaced in the lower bays of the Gulf by Thais. Other than this, the communities are essentially like those of the Atlantic coast. One of the peculiarities of distri- bution within the oyster community or biocoenosis is the apparent absence of the commensal (or at times parasitic) crab. Pinnotheres ostreum, from the northeastern part of the Gulf, although it has been reported from Cameron, Louisiana, and is not rare in Matagorda and Mesquite Bays in Texas. There are some examples of marginal oyster communities which are worthy of notice. In parts of coastal Louisiana, especially in the vicinity of Atchafalaya Bay and Marsh Island, oj'ster reefs in the bays have been reduced by invasion of fresh water, and salinity conditions suitable for the development of reefs are found in the Gulf itself. At the other extreme, a small oyster community persists near Port Isabel where salinities are nearly oceanic most of the year, and the epifauna is characteristically marine (Hedgpeth 1953). Since the reefs south of Marsh Island were mapped in 1906 by Cary, there seems to have been little change in their extent, and they remain the only extensive oyster reefs known in the Gulf of Mexico proper. From time to time there have been rumors of large reefs in offshore waters, but these rumors seem to be kin to those of fabulous lost mines which can never be found. Clam beds have been reported for various places, but none have been studied. The low-salinity Rangia forms extensive beds in Louisiana and brackish lakes of Texas as far south as Green Lake. Extensive worm communities probably exist, in view of the great shrimp populations, but none have been studied in detail. We have only re- cently begun to learn which species of worms occur (Hartman 1951). Beds of Spiochaetopterus have been observed in Louisiana. The only study of clam beds is that of Spaulding (1906) who worked out the distribution of clams and scallops in the Chandeleur Islands (fig. 53). Investigations of bottom communities in Texas and Louisiana are now being conducted as part of a study of the nearshore Recent sediments. This project is sponsored by the American Petro- leum Institute (Shepard and Moody, 1952). The 208 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE M OBILE: B ay, ALA. 1 mile 2 11 X3 — 30° 1 15'N- ^ ID ' 10 IC \^: n •J IE ..V \ after &rave,1905 76%VW \ Figure 52. — Characteristic Gulf coast oyster reefs from various survey reports aa indicated, together with those of Newport River, North Carolina. GULF OF MEXICO 209 89°10' 89° 00 ■M ZLfWAS-^ l/enus rr)ercer)arici ^ SCALLOPS'-' Pec ten 2 rradians Ol23i5676 MILLS -29%5' — S9%5- ••■■.> + 89°00' — zrzo'- ATter Spauldinq, ,•1906 Figure 53. — Clam and scallop beds of the Chandeleur Islands in 1906. 210 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE preliminary results of the work east of the Mississippi delta (carried out by R. H. Parker) indicate that there is a density of 100 individual mollusks (mostly Mulinia lateralis) per orange peel bucket sample of 100 cu. in. capacity on some muddy bottom areas in this region. It would appear that we have here a community comparable to the Syndosmya {=Abra) community of "shallow and protected waters of an estuarine character" (Jones 1950). Such a community, composed of small, rapidly growing species, may have a rapid overturn and thus have a higher productivity in terms of harvestable crop than a community composed of larger, slower growing species. It would also be less stable. SERPULOID REEFS While the serpuloid reefs of Bermuda are fairly well-known to biologists, at least by hearsay, it is not generally realized that similar reefs occur in the Gulf of Mexico. There is a smaU area of scattered serpuloid reefs at the junction of Baffin Bay and the Laguna Madre, south of Corpus Christi, Texas, and a larger area near Veracruz, Mexico. Recent efforts to collect the worm that caused these growths in Baffin Bay have been un- successful, and there is some question as to whether this reef is still actively growing. Ac- cording to W. Armstrong Price, there is evidence that these reefs had been actively growing within the last 80 years. The only information of the reefs near Veracruz is the brief paper by Heilprin (1890). Two reefs are mentioned; one, near Punta Gorda, was, at the time, lying parallel to shore about }i mile from land, about /(e mile wide and about % mile in length. The other, off Punta de Hornos, was about the same size and in the same relative position to the shore line but about half as wide. A modern survey of these reefs should provide interesting information as to growth and ecology. The serpuloid reefs of Baffin Bay are of peculiar interest in view of the high salinities which occur in this region. Salinities as high as 80 parts per thousand have been recorded, and during the pe- riod from July 1946 to October 1948 the lowest recorded salinity was 41.6 parts per thousand. Samples of serpuloid rock from this region have yielded two species of polychaetes, two amphipods and a barnacle. All the species are well-known estuarine forms. THE JETTY COMMUNITY There are no naturally rocky shores in the eastern or northern Gulf of Mexico, hence, there are no extensive hard-bottom communities. A limited fauna and flora has become established on the various jetties along the Texas coast and also on the short jetties at Calcasieu Pass near Cam- eron, but the life of the jetties on the passes of the Mississippi Delta has not been studied. The biota of the Texas jetties has been discussed by Whitten, Rosene, and Hedgpeth (1950) who de- scribe the intertidal community of these jetties as consisting principally of three species of barnacles, a pulmonate limpet, a littorine, a species of Brachidontes , and various less numerous elements. Plants, an essential component of such communities, were not studied. This community was built up by colonization from nearby bottom habitats and possibly sargassum since construction of the jetties six or seven decades ago. Two motile artliropods, the isopod, Ligia exotica, and the al- most cosmopolitan crab, Pachygrapsus transversus, are among the most characteristic and obvious members of this community. Zonation is well-marked on the jetties, although the zones are narrow and vary somewhat with the season. At Port Aransas the average low-water line is marked by a belt of the brown algae, Padina vickersae, which extends down to extreme low water, 8 to 12 inches lower. Above the Padina belt is another narrow zone characteris- tically occupied by various red algae, especially Gelidium, Bryocladia, and the like, topped by a still narrower band of Ulva. In these algal zones are found such snails as Thais and Cantharus, and in the Padina zone are found the purple urchin, Arhacia punctulata, and the anemone, Bunodosoma cavernata. Between the top of the narrow Ulva belt and the maximum concentration of barnacles {Chthamalus fragilis) at about 2.5 to 3 feet above mean low water, there is a sparse scattering of barnacles. Above the barnacles are found the small, black littorine, Littorina ziczac, and the pulmonate limpet, Siphonaria pectinata. There are, in summary, three principal zones on the jetty rocks and walls: an upper zone, charac- terized by the littorines and barnacles, a middle algal zone occupied by greens and reds, and the lower Padina zone. This pattern is associated with the average tidal levels for most of the year. GULF OF MEXICO 211 Duriii<}: tho pcM-iods of lower mean soa level in January aiul February, the lowermost zone, below the brown algae, is exposed. This zone consists of hydroids, Bryozoa, and encrusting sponges. Inshore, near laud and on concrete pilings at Port Aransas, the middle zone is also occupied by oysters. Mussels do not occur at Port Aransas but are found at Frecport and Galveston on the jetties. Although not occurring in the Gulf of Mexico proper, the zonation in the Florida Keys and at Beaufort described bj' the Stephensons (1949, 1950, 1952) have aspects in common with that at Port Aransas. The most conspicuous difference is, the generally lower arrangement of the entire zonal pattern at Port Aransas in relation to tide zero, a phenomenon apparently associated with the pronounced seasonal differences in sea level on the Texas coast (fig. 54) and the higher level of the tide zero in relation to the tidal cycle. There is a tendency toward the formation of sub-zones in Texas and Florida which may be induced by irregular tidal cycles; this complex pattern seems much less developed at Beaufort, where the tidal cycle is more regular (Hedgpetli 1953, pp. 188-194). SAND BEACH COMMUNITIES The communities of the sand beaches are evi- dently similar to those of the Beaufort area which were studied by Pearse, Humm, and Wliarton (1942) since many of the same species, or closely related species, occur on the sandy beaches of Texas and Louisiana. LaFleur (1940) briefly described the biota of sand beaches of Grand Isle. Neither of these are studies of communities, in the strict sense of the term. The most notice- able bottom community of the sandy beach is that of Donax which occurs in large beds, moving up and down with the tides. Immediately offshore there are evidently large communities composed of such bivalves as Dinocardium robustum, Area and Anadara, Dosinia and Teliina, predaceous gastropods, and such echinoderms as Mellita and Astrojjecten. This assemblage appears to be a counterpart of the sandy-bottom Teliina commu- nity of European waters. The characteristic inhabitant of the sand beach is the ghost crab, Ocypode albicans, which seeks refuge during daylight hours in burrows well 25953-1 0—54 15 above high tide lines. Beyond this region, at Port Isabel and in southern Florida, there occurs the larger land crab, Cardisoma guanhumi. Occa- sional individuals are found at Port Aransas, but established colonies of them are uidinown north of Port Isabel except at Grand Isle (Behre 1950). Lower down on the beach, associated with the windrows of algae (sargassum in spring and sum- mer and various reds in winter) are the amphipods, Orchestia grillus, 0. platensis, and Talorchestia longicornis. Intensive study of the animal life of this most characteristic of Gulf coast environments has hardly begun. Caspers (1951), in a study of the arthropods of the Bulgarian coast, characterized the community of the sandy beaches as the "Orchestia variation of the Pachygrapsus bio- coenosis." From the vantage point of the Texas coast where Pachygrapsus seems most abundant on the jetties and the sand constitutes the major part of the environment, we might say that Pachygrapsus is a "variation" of the "Or- chestia (or Ocypode) biocoenosis." THE SHRIMP GROUND COMMUNITY Offshore in the muddy bottoms between the foot of the sandy beach and the 10- to 15-fathom line there occirrs a large community which we recognize principally as that from which white shrimp, Penaeus setijerus, are taken in commercial quantities. Several sedentary invertebrates are characteristic of these bottoms. The most con- spicuous of these is the sea pansy, Renilla miilleri, which must pave the bottom in some localities. A gorgonian, Leptogorgia setacea, also flourishes in this region. Other characteristic members of this shrimp ground community include tube building worms of the family Onuphidae, crabs of the genera Hepatus, Calappa, and Persephone, the anemone, Paranthus rapiformis, and certain gastropods, e.g.. Busy con, Murex, Dolium, and Fasciolaria. In the larger abandoned shells of these snails there occurs the large red hermit crab, Petrochirus bahamensis. UsuaUy the shells bear one or more anemones, Calliactis tricolor, and inside, living commensally with the hermit crab, is the porcelain crab, Por- cellana sayana. Also common, but perhaps oc- curring in irregular colonies, is the stomatopod, Squilla empusa. 212 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Port Aransas Texas 5- 4-- l jetty) Littorina V- 3->_ :&■- Chtharnalus 2- EHW West Summerland Key, Florida (se-awall) -5' 1.-. •^.:-.-*- -3* -«3- Littorma -z 1- Cs pflr be) I I 1- TiDE Oysters & Ulva /\ 0- ~~-.^ I 0- Red olqak ~~ }-• ^ -1 1- £/.;«' 2- Sponqes, bryo'^oa. g- ArbociQ. iiC Beaufort, No. Car. -3 ( BL A C K -2 1- -0. Chthamalus—tf A- ^•^ ^ I 0- -!■ Alqae I -1 £/-«^i- Corals -0 -1' •'■7 (jetty) -5' (BLACK) Uttorina -\ Cht)iamalus -j £HW Oysters 4 Ulva Mussels -z Aiptosia, Alqoe, Arbocm =*-^TIDE ZERO £/.V/ -r Figure 54. — Pattern of distribution of organisms on jetties and sea wall in Port Aransas, Texas, West Summerland Key, Florida, and Beaufort, North Carolina. The preceding description applies principally to the grounds frequented by the commercial shrimp, Fenaeus setiferus. The recent change in the shrimp fishery toward exploitation of the popula- tions of the brown or grooved shrimp, P. aztecus, has revealed some differences in the constitution of the bottom communities frequented by P. aztecus. Renilla is no longer charactpristic, but one of the Astropectens is abundant, and two bivalves, Pitaria cordata and Chione clenchi, are much more abundant than they are closer inshore on the P. setiferus grounds. The principal region occupied by the pink shrimp, P. duorarum, is near Key West across the Strait from Campeche Bank GULF OF MEXICO 213 (fig. 51), the fauna of which is predominantly tropical in character. The communities which support penaeid shrimp appear to have no counterpart in European waters, but similar communities evidently occur in waters of southeastern Asia and along the western coast of Central America. It is worthy of note that the commercial fishery of shrimp is one of the few major fisheries drawing upon an annual (or perhaps bieimial) production and is thus more dependent on the short term production of bottom fauna and short-term secular changes in the environment than are the fisheries which exploit organisms that have required several years to reach marketable size. THE CORAL AND SPONGE COMMUNITIES These are tropical, stenohaline communities, rich in number of species and difficult to charac- terize except in terms of their dominant members. The reef-building coral is a true community dom- inant, shaping the community and altermg the environment. The small reefs or patches along the Texas and Louisiana coast are peculiar north- ern fragments of the West Indian reefs. Their position is governed primarily by the occurrence of small elevations along the edge of the con- tinental shelf which rise to within 10 to 25 fathoms of the surface rather than by temperature or sedimentation conditions. These elevations may indicate dome structures. It can be inferred from the presence of these living reefs that the mean temperatures do not fall below 20° C. along the summits of these structures. There are rare rec- ords of tropical reef animals, especially decapod Crustacea, along the Texas coast indicating that these reefs have the usual West Indian tropical fauna and that a certain amount of straying, especially during the summer months, occurs. More information concerning the sponge and coral communities of western Florida will be found in other parts of this volume. LITERATURE CITED Allee, W. C, et al. 1949. Principles of animal ecology. 837 pp., 263 figs. Philadelphia: W. B. Saunders. Andree, K. 1920. Geologie des Meeresbodens. Vol. 2, Bodens- beschaffenheit, nutzbare Materialien am Meeres- boden. Pp. xx, 689. Leipzig. Archer, Allan F. 1947. A scientific study of effects of 1947 hurricane on oyster reefs in Alabama. Alabama Conserv. 19 (6): 7, 12, 2 figs. 1948a. Alabama's oyster reefs. Alabama Conserv. 19 (11): 8-9, 2 figs. 1948b. June oyster reef survey. Alabama Conserv. 20 (1): 5-29. Bartholomew, J. G.; Clarke, W. Eagle, and Grimshaw, Perct H. 1911. Atlas of zoogeography. 67 pp., 36 pis. Behre, Ellinor H. 1950. Annotated list of the fauna of the Grand Isle region 1926-1946. Occ. Pap. L. S. U. Mar. Lab. No. 6, 66 pp. Brotskaja, V. A., and Zenkevich, L. A. 1939. Quantitative evaluation of the bottom fauna of the Barents Sea. Summary. Trans. Inst. Mar. Fish. Oceanog. U. S. S. R. 4 (8): 99-126. Cart, L. R. 1906. The conditions for oyster culture in the waters of the parishes of Vermilion and Iberia, Louisiana. Bull. Gulf Biologic Sta 4: 1-27, chart. Caspers, H. 1951. Biozonotische Untersuchungen tiber die Strandar- thropoden im bulgarischen Ktistenbereich des Schwarzen Meeres (Untersuchungen iiber die bul- garische Kiistentierwelt 3). Hydrobiologica 3 (2): 131-193, 15 figs. Chambost, L. 1928. Essai sur la region littorale dans les environs de Salamrab6. Bull. Sta. Oceanog. Salammb6 8: 1-28, 7 figs., chart. Clements, F. E., and Shelford, V. E. 1939. Bio-ecology, vii, 425 pp., 85 figs. New York: John Wiley. Ekman, Sven. 1935. Tiergeographie des Meeres. Leipsig : Akad. Verlag xii, 542 pp. 1953. Zoogeography of the Sea. London: Sidgwick and Jackson xiv, 417 pp. Galtsoff, Paul S. 1931. Survey of oyster bottoms in Texas. Bur. Fisheries Inv. Rept. No. 6, 30 pp., 15 figs. Grave, Caswell. 1905. Investigations for the promotion of the oyster industry of North Carolina. Rept. U. S. Fish Comm. 1903: 247-341, 10 pis., 1 chart. Gunter, G. 1936. Studies of the destruction of marine fish by shrimp trawlers in Louisiana. Louisiana Conserv. Rev. 5: 18-24, 45-46. 1938a. The relative numbers of species of marine fish on the Louisiana coast. Am. Naturalist 72: 77-83. 1938b. Seasonal variations in abundance of certain estuarine and marine fishes in Louisiana, with par- ticular reference to life histories. Ecol. Monog. 8: 313-346. 1945. Studies on marine fishes of Texas. Pub. Inst. Mar. Sci. 1 (1): 1-190. 214 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE GuNTEB, G. — Continued 1947. Paleoecological import of certain relationships of marine animals to salinity. Jour. Paleont. 21 (1): 77-79. 1950. Seasonal population changes and distributions as related to salinity, of certain invertebrates of the Texas coast, including the commercial shrimp. Pub. Inst. Mar. Sci. 1 (2): 7-51. Hartman, Olga. 1951. The littoral marine annelids of the Gulf of Mexico. Pub. Inst. Mar. Sci. 2 (1): 7-124. Hedgpeth, Joel W. 1953. An introduction to the zoogeography of the northwestern Gulf of Mexico with reference to the invertebrate fauna. Pub. Inst. Mar. Sci. Texas. 3 (1) : 109-224, 46 figs. Heilprin, Angelo. 1890. The corals and coral reefs of the western waters of the Gulf of Mexico. Proc. Acad. Nat. Sci. Phila- delphia, 1890, 42: 303-816, pis. 6-7. Jones, N. S. 1950. Marine bottom communities. Biol. Rev. 25 (3): 283-313. Ladd, Harry S. 1953. Brackish-water and marine assemblages of the Texas coast, with special reference to mollusks. Pub. Inst. Mar. Sci. Texas. 2(1): 125-164, 2 figs., table. LaFleur, N. C. 1940. The beach fauna of Grand Isle, La. Bios 11 (2): 112-119. Lowman, S. W. 1949. Sedimentary facies in Gulf coast. Bull. Amer. Assn. Petr. Geol., 33 (12): 1939-1997, 35 figs. Moore, H. P. 1899. Report on the oyster beds of Louisiana. Rep. U. S. Fish Comm. 24: 45-100, 1 chart. Moore, H. F. 1907. Survey of oyster bottoms in Matagorda Bay, Texas. U. S. Bur. Fish. Doc. 610, 86 pp., 13 pis., 1 chart. 1913a. Conditions and extent of the natural oyster beds and barren bottoms of Mississippi Sound, Ala- bama. U. S. Bur. Fish. Doc. 769, 61 pp., 5 pis., I chart. 1913b. Condition and extent of the natural oyster beds and barren bottoms of Mississippi east of Biloxi. U. S. Bur. Fish. Doc. 774, 41 pp., 6 pis., 1 chart. and Danglade, Ernest. 1915. Condition and extent of the natural oyster beds and barren bottoms of Lavaca Bay, Texas. U. S. Bur. Fish. Doc. 809, 45 pp., 5 pis., 1 chart. NoRBis, Robert M. 1953. Buried oyster reefs in some Texas Bays. Jour. Paleo., 27 (4): 569-576, 5 figs. Ohveira, Lbjeune, p. H. de. 1948. Distribuigao geogrsifica da fauna e flora da Bala de Guanabara. Mem. Inst. Oswaldo Cruz 45 (3): 709-734, 4 figs., I pi. 1950. Levantamento biogeogrdfico da Bafa de Guana- bara. Mem. Inst. Oswaldo Cruz 48: 363-391, 19 figs. Orton, J. H. 1937. Oyster biology and oyster culture. 211 pp. London: Edward Arnold. Parker, Frances L., Phleger, Fred B., and Pierson, Jean F. 1953. Ecology of foraminifera from San Antonio Bay and environs, southwest Texas. Cushman Found- Foram. Res., Spec. Pub. 2, 75 pp., 48 figs., 7 tables, 4 pis. Pearse, a. S.; Humm, H. J.; and Wharton, G. W. 1942. Ecology of sand beaches at Beaufort, North Carolina. Ecol. Monogr. 12: 135-190, 24 figs. and Wharton, G. W. 1938. The oyster "leech" Stylochus inimicua Palombi, associated with oyster on the coasts of Florida. Ecol. Monogr. 8: 605-655, 37 figs. Puffer, Elton L. and Emerson, William K. 1953. The moUuscan community of the oyster reef biotope on the central Texas coast. Jour. Paleo., 27 (4) : 537-544, pi. 56, 1 fig. Shepard, Francis P. and Moody, Clarence L. 1952. API research project 51 — study of near-shore Recent sediments and their environments in the northern Gulf of Mexico. 33d aimual meeting. Amer. Petr. Inst., No., 1953. 14 pp., 10 figs. Spaulding, M. H. 1906. A preliminary report on the distribution of the scallops and clams in the Chandeleur Islands regions, Louisiana. Bull. Gulf Biologic Sta. 6: 29-43, 1 chart. Stephenson, T. A. and Anne. 1949. Life between tide-marks in North America. Endeavour 9 (33): 3 pp., 4 figs. 1950. Life between tide-marks in North America. I. The Florida Keys. Jour. Ecol. 38 (2): 354-402, 10 figs., pis. 9-15. 1952. Life between tide-marks in North America. II. Northern Florida and the Carolinas. Jour. Ecol. 40 (1): 1-49, 9 figs., pis. 1-6. Whitten, H.; Rosene, H. F.; and Hedgpeth, J. W. 1950. The invertebrate fauna of Texas coast jetties; a preliminary survey. Pub. Inst. Mar. Sci. 1 (2) : 53-87, 4 figs., 1 pi. Zenkevich, L. A. 1947. Fauna i biologicheskaia produktivnost moria. Tom. 2, Moria S. S. S. R., Leningrad, Sovetskaia Nauka, 688 pp., 327 figs. Zenkevitch, L., and Brotzky, V. 1939. Ecological depth-temperature areas of benthos mass-forms of the Barents Sea. Ecology 20 (4) : 569- 576, 2 figs. CHAPTER VI BACTERIA, FUNGI, AND UNICELLULAR ALGAE MARINE BACTERIA AND FUNGI IN THE GULF OF MEXICO ' By Claude E. ZoBell, Scripps Institution of Oceanography, University of California Although the marine environment around the West Indies was one of the first to be examined by a bacteriologist (Fischer 1886) and has since been quite extensively studied (Drew 1912; Bavendamm 1932), there are very few published reports on bacteria and fungi in the nearby Gulf of Mexico. The author has been actively inter- ested in the Gulf coast area since 1940, but the semiconfidential nature of the research projects has contraindicated the publication of the results. This paper summarizes personal observations in the region along with published reports that have a direct bearing upon microbiological conditions in the Gulf of Mexico where observations have been confined almost exclusively to regions near shore. The rather extensive but scattered liter- ature on marine microbiology has been reviewed by Issatchenko (1914), Bavendamm (1932), Benecke (1933), ZoBell and Upham (1944), and ZoBell (1946a, 1947). Also noteworthy is the comprehensive article by Williams (1951) on the occurrence, importance, and characteristics of bacteria in the sea. Waters of the littoral zone in the Gulf of Mexico are veritable bacterial gardens. At scat- tered stations from Tortugas to Aransas Pass, where water samples have been examined, bacterial populations ranging from thousands to many million per ml. have been observed. Large num- bers of living bacteria have also been found in bottom sediments. The methods employed by various investigators for collecting and analyzing samples of water and marine sediments for num- bers and kinds of bacteria have been summarized by ZoBell (1946a). The abundance of bacteria in shallow Gulf waters, which greatly exceeds the abundance of bacteria in the open ocean, is believed to be attributable primarily to the higher content in the former of organic matter and suspended solids, I Contribution from the Scripps Institution of Oceanography, New Series No. 661. This paper is a contribution from the American Petroleum Insti- tute Research Project 43A. both of which promote the growth of bacteria. The influx of fresh water with its load of organic nutrients from land drainage is also a contributing factor along the littoral zone. Here there is a com- mingling of both fresh-water and marine micro- organisms and numerous transitional stages of both kinds. The observations of Berkeley (1919), Korinek (1926), Lipman (1926), Burke and Baird (1931), ZoBell and Feltham (1933), Burke (1934), and others indicate that ordinarily bacteria from fresh-water or terrestrial sources do not survive very long in sea water, but if the transition to the salt-water environment is gradual, as in brackish water of increasing salinity, a good many fresh- water forms may become acclimated to the marine environment (ZoBell and Michener 1938). The bacterial flora of the Gulf coast region is characterized by exceptional biochemical versa- tility, cultures having been isolated that catalyze the transformation of virtually all types of organic matter and a good many Inorganic substances. In the latter category are autotrophic bacteria of various kinds that oxidize hydrogen sulfide either in darkness or under the influence of sunlight (van Niel 1931, 1944). Autotrophs which oxidize ammonia to nitrite appear to be more common in surface water and sediment than those which oxidize nitrite to nitrate (Carey 1938). Methane oxidizers (Hutton and ZoBell 1949) were found in the topmost portions of mud samples from the Gulf coast region, and sulfate-reducing bacteria which oxidize molecular hydrogen as the sole source of energy were found in numerous samples from considerable depth (Sisler and ZoBell 1950). Besides modifying inorganic substances, auto- trophic bacteria are primary producers of organic matter. While some obtain their energy from sunlight in the manner of other photosynthetic plants, most autotrophic bacteria obtain their energy for the reduction of carbon dioxide from the oxidation of substances such as hydrogen sulfide, hydrogen, methane, ammonia, or nitrite. 217 218 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Quantitative data on the relative amounts of organic matter synthesized by autotrophic bacteria are not available, but judging from the abundance of such bacteria and the quantities of ammonia, hydrogen, methane, or other substance believed to be oxidized, organic production from this source may be appreciable. The chief fimction, however, of bacteria in the marine environment is in the mineralization or modification of organic matter (Waksman 1934). Among the organic materials found to be attacked by marine micro-organisms are sugars, starches, celluloses (Bavendamm 1932; Waksman et al., 1933), pectins, glucosides, fatty acids (Thayer 1931), triglycerides, alcohols, sterols, proteins, amino acids, chitins (Hock 1940), lignins, agar (Stanier 1941; Humm 1946), and hydrocarbons (ZoBell 1950a). These organic substances are attacked by both aerobic and anaerobic bacteria. From Gulf of Mexico mud, Campbell and Williams (1951) isolated 20 strains of aerobic chitin-decomposing bacteria, including species of Achromobacter, Flavobacterimn, Micrococcus, and Pseudomonas. Several of the cultures were actively proteolytic and/or lipolytic. Mixed cultures from marine mud tend to de- compose the organic remains of plants and animals (Waksman 1934) in aerobic environments with the formation of carbon dioxide, ammonia, sulfate, phosphate, and other oxidation products at a rate which is primarily a function of the tem- perature. In the absence of free oxj-gen the rate at which organic matter is modified by bacteria may be much slower, and, while there may be much mineralization of organic substances, in anaerobic environments certain constituents may be reduced or hydrogenated to form the mother substance of petroleum (ZoBell 1950b). The action of heterotrophic bacteria is not confined to the decomposition of particulate or- ganic materials. Dissolved organic matter is also utilized, it having been shown by ZoBell and Grant (1943) that under static conditions bacteria may reduce the organic content of sea water to less than 0.1 mgm./L. According to Waksman and Carey (1935), roughly 60 percent of the organic carbon is oxidized by aerobes to carbon dioxide and the remaining 40 percent is assimilated for conversion into bacterial protoplasm. The latter, being particulate, becomes available as a source of food for protozoa, copepods, filter feeders, detritus feeders, and grazing animals in general. Ki-izencky and Podhradsky (1927) regard the conversion of dissolved organic matter into par- ticulate matter utilizable by animals as one of the most important functions of bacteria in aquatic environments. The importance of bacteria as food for animals has been emphasized by the work of Baier (1935), MacGinitie (1935), Voroschilova and Dianova (1937), Mare (1942), and ZoBell and Feltham (1938). The latter workers (1942) estimated that around 10 grams (dry weight) of bacterial organic matter is produced per day per cubic foot of mud in a shallow marine mud flat. In summarizing the ecological function of bacteria on sand beaches, Pearse et al. (1942) point out that besides serving as food for small animals, bacteria are important scavengers, and they pro- duce plant nutrients, including ammonia, nitrite, nitrate, and phosphate. From thousands to millions of living bacteria were found in beach sands at Beaufort, North Carolina. Large numbers of bacteria were found by Williams et al. (1952), to be associated with the bay shrimp, Penaeus setiferus, taken from Aransas Bay and from the Gulf in the region of Galveston. Species of Achromobacter, Bacillus, Micrococcus, Pseudomonas, Alcaligenes, and Flavo- bacterium predominated in the order named. Most of the attached bacteria were carried by the cephlothorax portion of the shrimp. The optimum temperature for the growth of the bacteria was around 25° C, but most of the 1,200 cultures examined grew slowly at 4° C. Neither coliforms nor enterococci were detected by Williams and Rees (1952) in the intestinal tract of shrimp, suggesting that such bacteria have sanitary significance. Another important function of bacteria is as sjonbionts in the alimentary canal of most marine animals where they aid m the digestion of chitin, cellulose, pectin, lignin, and other organic com- plexes. Similarly, certain shipworms and wood borers are believed to depend upon commensal bacteria which help to digest cellulose and lignin. On the other hand, a small percentage of the microbial flora is pathogenic for plants or animals. Fish, Crustacea, shellfish, and other marine ani- mals in nearly all stages of development may be susceptible to microbial infections; the pertinent GULF OF MEXICO 219 litorature on this subject has boon annotatod by ZoBoU (1946a). Seaweeds, diatoms, dinoHagjol- iates, ami otlier marine plants may be extonsivoly parasitized by pathogenic bacteria, actinomyces, yeasts, and mold fungi. The wasting disease of eelgrass, which threatened the extermination of Zostera marina along the Atlantic seacoast a few years ago, is believed to be due to infection by Labyrinthula species (Renn 1936), although Halo- pMoboluii species ma}- also be involved (Barghoorn and Linder, 1944). By vitiating the water in local environments or in the wake of periods of intense organic produc- tivity, bacteria may have far-reaching adverse effects on the plant and animal populations. Among the ways m which bacteria contribute to the vitiation of aquatic environments are by de- pleting dissolved oxygen, by producing hydrogen sulfide, by forming toxic amines, or bj' changing the pH of the water. So-called stagnant water basins are rendered uninhabitable primarily by the activities of bacteria, and extensive areas in the open ocean may become temporarily lethal for plants or animals. For example, Copenhagen (1934) described an area approximatelj' 25 by 200 miles in the Atlantic Ocean off Walvis Bay, South Africa, where hydrogen sulfide is liberated period- ically by bacterial activity in quantities sufficient to kill both flora and fauna. The bacterial vitia- tion of water is believed by the writer to be an important feature of the "red tide." Extensive populations of purple sulfur bacteria, observed by Gietzen (1931) growing associated with decom- posing algae along the Holstein coast, imparted a distinctly red coloration to the sea. Marine bacteria also contribute to the bio- fouling of man-made structures. The attach- ment and growth of barnacles, bryozoans, tuni- cates, mussels, clams, algae, and other fouling organisms on ships' bottoms or other submerged surfaces may be pi-omoted by bacteria in various waj-s (ZoBell and Allen 1935). Likewise, micro- organisms may contribute cither directly or in- directl}^ to the deterioration of pilings, planks, and other wooden structures in sea water. Lines, ropes, nets, semes, sailcloth, and other cordage or textile products readily rot in sea water unless they are treated to preserve them from microbial decomposition (Atkins and Warren 1941). Un- protected steel and iron structures are also sus- ceptible to attack by bacteria which oxidize fer- rous iron, produce acids, form hydrogen sulfide, create reducing conditions, or depolarize hydro- gen films resulting from the reaction between water and iron. Acid production in microspheres from the bacterial oxidation of organic matter or sulfur may result in the corrosion of concrete. Even rubber and bituminous coating materials may be attacked by marine micro-organisms (ZoBell 1950a). Bacteria are important chemical and geological agents in marine bottom deposits where they promote many processes involving organic com- pounds, inorganic constituents, and physicochem- ical conditions that affect the modification or diagenesis of sediments. One of the first geo- chemical processes to be studied by microbiologists was calcium carbonate precipitation which Drew (1911a, b) attributed to the activities of denitri- fying bacteria found in great abundance in shallow subtropical seas in the vicinity of Jamaica and Tortugas. He (1912) reported that marine mud near the Bahamas contained an average of 160 million bacteria per ml. with Bacilliis calcis pre- dominating. Working in the same region, Keller- man and Smith (1914) confirmed Drew's hypoth- esis on the precipitation of calcium carbonate by bacteria which raise the pH by reducing nitrate, by producing ammonia, or by utilizing organic acids. After finding rather sparse bacterial populations in the open sea around Tortugas, Lipman (1929) questioned whether bacteria contribute signifi- cantly to calcium carbonate precipitation. This view was rendered untenable, however, by the extensive observations in the Bahamas of Baven- damm (1932) who concluded that calcium carbon- ate precipitation in tropical seas is primarily a microbiological process. Similar conclusions were reached by Gee (1932) who investigated bacterial activity in the Florida Keys. Micro-organisms found there by Gee and Feltham (1932) promoted the precipitation of calcium carbonate by produc- ing ammonia and otherwise increasing the pH. The pH of marine sediments may be increased by micro-organisms which (1) form ammonia, (2) reduce nitrate or nitrite, (3) reduce sulfate, (4) oxidize or decarboxylate organic acids, or (5) utilize CO2. On the other hand, the (1) produc- tion of CO2 or organic acids, (2) oxidation of 220 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE hydrogen sulfide or sulfur, (3) formation of nitrate, (4) assimilation of ammonia, or (5) the liberation of phosphate from organic compounds are micro- bial processes that tend to decrease the pH of their environment. Reactions ranging from pH 6.8 to 8.7 in Gulf coast sediments are believed to be attributable, at least in part, to microbial activities. Similarly, bacteria and allied micro- organisms are believed to be the principal dynamic agencies that create conditions in marine sediments sometimes as reducing as En— 460 millivolts (ZoBe.U 1946b). The general tendency is for micro-organisms to mineralize the organic remains of plants and ani- mals in marine sediments. In highly reducing environments, however, the microbial decomposi- tion of organic matter may result in residues relatively richer in hydrogen and correspondingly poorer in oxygen, nitrogen, sulfur, and phosphorus. This results in the accumulation of organic com- plexes that are more petroleum-like than then- predecessors (ZoBell 1950b). The microbial for- mation of methane is a common property of recent marine sediments, and there is pretty good evi- dence that bacteria also produce higher hydro- carbons. Wliile there is no reason to believe that bacteria produce petroleum, they may contribute in many ways to its formation. The high organic productivity and rapid rate of sedimentation in Gulf coast waters suggest this region as a potential source bed of petroleum. Petroleum hydrocarbons may be modified in recent sediments by micro-organisms. Both aero- bic and anaerobic bacteria which attack petroleum hydrocarbons were detected in nearly all 1-gram samples of surface mud collected from shallow water along the coasts of Louisiana and Texas. From hundreds to millions of such micro-organisms per gram of mud were demonstrated by the minimum dilution method. Sulfate-reducing bacteria were also found in abundance, some at core depths exceeding a hundred feet. Sulfate reducers form hydrogen sulfide, and they may account for the formation of sulfur. The recovery of sulfate reducers liaving unique tolerance for temperature, salinity, and hydrostatic pressure from oil and sulfur wells suggests that they may be indigenous species in ancient marine sediments (ZoBell and Rittenberg 1948). A large percentage of the sulfate reducers isolated from Gulf coast sediments can utilize molecular hydrogen (Sisler and ZoBell 1950). Several other physiological types of bacteria, that may function as geochemical agents, have been found in marine sediments, but their impor- tance can be assessed only after they have been more thoroughly studied. Marine fungi, including yeasts and molds, are found almost exclusively in water and the topmost layers of sediment. Being heterotrophs, such fungi are closely associated with organic sub- stances. Both yeasts and molds commonly occur growing either saprophytically or parasitically on marine plants and animals. According to Sparrow (1936), who isolated 18 new species of mold fungi from the Woods Hole region, marine fungi have been even less completely studied than marine bacteria. Barghoorn and Linder (1944) were impressed by the diversity of fungi found in the sea. A good many of the fungi species isolated from the sea are quite unlike any known terrestrial species. They grew better in sea water than in corresponding fresh water media, and some species developed in media containing three times as much salt as normal sea water. LITERATURE CITED Atkins, W. R. G., and Warken, F. J. 1941. The preservation of fishing nets, trawl twines, and fiber ropes for use in sea water. Jour. Mar. Biol. A.SS0C. 25: 97-107. Baier, C. R. 1935. Studien zur Hydrobakteriologie stehender Binnen- gewasser. Arch. f. Hydrobiol. 29: 183-264. Barghoorn, E. S., and Linder, D. H. 1944. Marine fungi: their taxonomy and biology. Farlowia 1 : 395-467. Bavendamm, W. 1932. Die mikrobiologische Kalkfallung in der tropis- chen See. Arch. f. Mikrobiol. 3: 205-27G. Beneckb, W. 1933. Bakteriologie des Meeres. Abderhalden's Hand, d. biol. Arbeitsmethoden, IX Abt. 5: 717-854. Berkeley, C. 1919. A study of marine bacteria. Straits of Georgia, B. C. Trans. Roy. Soc. Canada, Ser. 3, Sec. 5, 13: 15-43. Burke, V. 1934. The interchange of bacteria between fresh water and the sea. Jour. Bact. 27: 201-205. Burke, V., and Baird, L. A. 1931. Fate of fresh-water bacteria in the sea. Jour. Bact. 21: 287-298. Campbell, L. L., and Williams, O. B. 1951. A study of chitin-decomposing micro-organisms of marine origin. Jour. Gen. Microbiol. 5: 894-905. GULF OF MEXICO 221 Carey, C. L. 1938. The occurrence and distribution of nitrifying bacteria in the sea. Jour. Mar. Res. 1: 291-304. Copenhagen, W. J. 1934. Occurrence of sulphides in certain areas of the sea bottom on the South African coast. Union S. Africa Fish Mar. Biol. Survey, Rept. No. 3, pp. 3-18. Drew, G. H. 1911a. Report of preliminary investigations on the marine denitrifying bacteria, made at Port Royal, Jamica, and at Tortugas. Carnegie Inst. Washington Yearbook 10: 136-141. 1911b. The action of some denitrifying bacteria in tropi- cal and temperate seas, and the bacterial precipitation of calcium carbonate in the sea. Jour. Mar. Biol. Assoc. 9: 142-155. 1912. Report of investigations on marine bacteria carried on at Andros Island, Bahamas, British West Indies, in May 1912. Carnegie Inst. Washington Yearbook U: 136-144. Fischer, B. 1886. Bacteriologische Untersuchungen auf einer Reise nach Westindien. Zeitschr. f. Hyg. 1: 421-464. Gee, H. 1932. Lime deposition and the bacteria. I. Estimate of bacterial activity at the Florida Keys. Carnegie Inst. Washington, Papers Tortugas Lab. 28 (435) : 67-82. and Feltham, Catharine B. 1932. Lime deposition and the bacteria. II. Charac- teristics of aerobic bacteria from the Florida Keys. Carnegie Inst. Washington, Papers Tortugas Lab. 28 (435): 83-91. GlETZEN, J. 1931. Untersuchungen iiber marine Thiorhodacean. Centralbl. f. Bakt., II Abt. 83: 183-218. Hock, C. W. 1940. Decomposition of chitin by marine bacteria. Biol. Bull. 79: 199-206. HUMM, H. J. 1946. Marine agar-digesting bacteria of the South At- lantic coast. Duke Univ. Marine Sta. Bull. 3: 45-75. Button, W. E., and ZoBell, C. E. 1949. The occurrence and characteristics of methane- oxidizing bacteria in marine sediments. Jour. Bact. 58: 463-473. Issatchenko, B. L. 1914. Investigations on the bacteria of the glacial Arctic Ocean. Monograph, Petrograd, 300 pp. Kbllerman, K. F., and Smith, N. R. 1914. Bacterial precipitation of calcium carbonate. Jour. Washington Acad. Sci. 4: 400-402. Korinek, J. 1926. Uber Stisswasserbakterien im Meere. Centralbl. f. Bakt., II Abt. 66: 500-505. Krizenckt, J., and Podhradskt. 1927. Studien Uber die Funktion der im Wasser gelosten Nahrsubstanzen im Stoffwechsel der Wassertiere. XI. 1st die Bakterienfiora der Vermittler Zwischen den Tieren und den aufgelosten Nahrsubstanzen? Zeitschr. vergl. Physiol. 6: 431-452. LiPMAN, C. B. 1926. The concentration of sea water as affecting its bacterial population. Jour. Bact. 12: 311-313. 1929. Further studies on marine bacteria with special reference to the Drew hypothesis on CaCOj precipi- tation in the sea. Carnegie Inst. Washington, Papers Tortugas Lab. 26: 231-248. MacGinitib, G. E. 1935. Ecological aspects of a California marine estuary. Am. Midland Naturalist 16: 629-765. Mare, Molly F. 1942. A study of a marine benthic community with special reference to the microorganisms. Jour. Mar. Biol. Assoc. 25: 517-554. Pbarse, a. S.; Humm, H. J.; and Wharton, G. W. 1942. Ecology of sand beaches at Beaufort, North Carolina. Ecol. Monogr. 12: 135-190. Renn, C. E. 1936. The wasting disease of Zostera marina. I. A phytological investigation of the diseased plant. Biol. Bull. 70: 148-158. SiSLER, F. D., and ZoBell, C. E. 1950. Hydrogen-utilizing, sulfate-reducing bacteria in marine sediments. Jour. Bact. 60: 747-756. Sparrow, F. K. 1936. Biological observations on the marine fungi of Woods Hole waters. Biol. Bull. 70: 236-263. Stanier, R. Y. 1941. Studies on marine agar-digesting bacteria. Jour. Bact. 42: 527-559. Thayer, L. A. 1931. Bacterial genesis of hydrocarbons from fatty acids. Bull. Am. Assoc. Petrol. Geol. 15: 441-453. Van Niel, C. B. 1931. On the morphology and physiology of the purple and green sulphur bacteria. Arch. f. Mikrobiol. 3: 1-112. 1944. The culture, general physiology, morphology, and classification of the nonsulfur purple and brown bacteria. Bact. Rev. 8: 1-118. VoROscHiLOVA, A., and Dianova, E. 1937. The role of plankton in the multiplication of bacteria in isolated samples of sea water. Mikro- biologiia, U. S. S. R. 6: 741-753. Waksman, S. a. 1934. The role of bacteria in the cycle of life in the sea. Scient. Monthly 38: 35-49. and Carey, C. L. 1935. Decomposition of organic matter in sea water by bacteria. II. Influence of addition of organic sub- stances upon bacterial activities. Jour. Bact. 29: 545-561. and Reuszer, H. W. 1933. Marine bacteria and their role in the cycle of life in the sea. I. Decomposition of marine plant and animal residues by bacteria. Biol. Bull. 65: 57-79. Williams, O. B. 1951. Marine microbiology. Texas Jour. Sci. 3: 69-75. and Rbes, H. B. 1952. The bacteriology of Gulf coast shrimp. III. The intestinal flora. Texas Jour. Sci. 4: 55-58. 222 nSHERY BULLETIN OF THE PISH AND WILDLIFE SERVICE Williams, O. B., Campbell, L. L., and Rees, H. B. 1952. The bacteriology of Gulf coast shrimp. II. Qualitative observations on the external flora. Texas Jour. Sci. 4: 53-54. , Rees, H. B. and Campbell, L. L. The bacteriology of Gulf coast shrimp. I. Experi- mental procedures and quantitative results. Texas Jour. Sci". 4: 49-52. ZoBell, C. E. 1946a. Marine microbiology. Chronica Botanica, Waltham, Mass., 240 pp. 1946b. Studies on redox potential of marine sediments. Bull. Am. Assoc. Petrol. Geol. 30: 477-513. 1947. Marine bacteriology. Ann. Rev. Biochem. 16: 565-586. 1950a. Assimilation of hydrocarbons by microorganisms. Advances in Enzymology 10: 443-486. 1950b. Bacterial activities and the origin of oil. World Oil 130 (7): 128-138. and Allen, Esther C. 1935. The significance of marine bacteria in the fouling of submerged surfaces. Jour, Bact. 29: 239-251. ZoBell, C. E., and Feltham, Catharine B. 1933. Are there specific marine bacteria. Proc. 5th Pacific Sci. Cong. 3: 2097-2100. 1938. Bacteria as food for certain marine invertebrates. Jour. Mar. Res. 1: 312-327. 1942. The bacterial flora of a marine mud flat as an ecological factor. Ecology 32: 69-78. and Grant, C. W. 1943. Bacterial utilization of low concentrations of organic matter. Jour. Bact. 45: 555-564. and Michener, H. D. 1938. A paradox in the adaptation of marine bacteria to hypotonic solutions. Science 87: 328-329. and RiTTENBERO, S. C. 1948. Sulfate reducing bacteria in marine sediments. Jour. Mar. Res. 7: 602-617. and Upham, H. C. 1944. A list of bacteria including descriptions of sixty new species. Bull. Scripps Inst, of Oceanog. 6: 239-292. DINOFLAGELLATES OF THE GULF OF MEXICO By Herbert W. Graham, United States Department of the Interior, Fish and Wildlife Service Dinoflagellates are important in the natural economy of the Gulf of Mexico as they are in all waters of the world. In marine phytoplankton thej' are usually outnumbered by diatoms, but they are second in importance to the diatoms as fundamental synthesizers of organic material in the sea. On the other hand, to the dinoflagellates belong most of the organisms which cause "red , water," mass mortalitj' of marine organisms, and paralytic shellfish poisoning. A thorough knowl- edge of the dinoflagellates is necessary to a clear understanding of the basic biology of the Gulf of Mexico. Despite the importance of these organisms, the Gulf of Mexico is almost a terra incognita in respect to our knowledge of the dinoflagellate plankton. Very few oceanographic expeditions have included the Gulf in their itinerary, and those that visited the Gulf have not reported on any dinoflagellate collections. Many species of dinoflagellates have a world- wide distribution, especially the offshore forms. Many of these can be expected in the Gulf. It is very likely that the pelagic species of the Gulf will be found to be similar to those of the tropical Atlantic, although the general composition of the flora may be different. The inshore, or neritic, plankton may well contain species peculiar to or at least characteristic of the Gulf of Mexico or of certain areas of the coast line. The dinoflagellate fauna of the open Gulf is very likely quite similar to that of the Caribbean and the tropical Atlantic. As far as the dinoflagellates are concerned, there are three general habitats in the Gulf of Mexico: the offshore waters, the neritic waters, and the sandy beaches. The offshore waters of the Gulf are clear and blue, characteristic of tropical waters the world over. Surface temperatures are high, the con- centration of nutrients is low, and the salinity high throughout the year. The quantity of plankton in these waters (the standing crop) is low (Riley 1938), but the number of species is probably relatively high. The temperature of this water drops markedly in the northern part of the Gulf for a few weeks during the winter, but as far as we know there is no seasonal change in the dinoflagellate fauna during this period. The neritic waters may be considered to include the shallow periphery of the open Gulf in which the water is often of very high temperature, with variable salinity and nutrient content and in which wind mixing creates high turbidity, par- ticularly in the winter when the density of the water is uniform from surface to bottom. The bays, bayous, and lagoons are also within this zone. These include mangrove swamps and other brackish \rater areas. Tidal effects are strong in the neritic zone, and the physical and chemical conditions of the water vary greatly tliroughout the year and, in some cases, within a daily tidal cycle. As a general rule, the species of dinoflagel- lates found in the neritic zone are distinct from those in open waters. However, the invasion of the coastal area with open Gulf water frequently obscures the zonation. Sandy beaches in the intertidal zone constitute the third type of environment for the Gulf dino- flagellates. Certain specialized species belonging chiefly to the genus Amphidinium thrive in this situation in some parts of the world (Herdman 1924) causing discoloration of the sand and lu- minescence. When they are abundant, each kick of the heel at night on a wet, sandy beach will cause a flash of light. There are apparently no reports of such "dinoflagellate sand" for the Gulf coast, but a careful investigation of this zone might reveal a rich fauna. Interest in the dinoflagellates of the Gulf, par- ticularly along the west coast of Florida, was stimulated by the disastrous outbreaks of red tide which occurred in that area in 1946 and 1947 (Galtsoff, 1948; Gunter et al., 1948; Gunter, Smith, and Williams, 1947; Smith 1949). This red water was caused by a previously undescribed species, Gymnodinium hrevis Davis (1948). The 223 224 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE study of the causes of these outbreaks was ham- pered by the lack of previous work in the area. As a consequence, the Marine Laboratory of the University of Miami and the Fish and WikUife Service of the United States Department of the Interior initiated a study of the local plankton in order to gain some information regarding the causes of such plankton blooms. In the course of these studies some insight was gained of the nor- mal dinoflagellate plankton along the west coast of Florida. Davis (1950) reported upon a number of plank- ton samples collected there in 1947 and 1948. He listed 15 species of dinoflagellates. He stated that the plankton of the west coast of Florida is markedly different from that of the east coast of Florida. Species found only on the west coast included the dinoflagellates, G. hrevis and Noctiluca scintillans Macartney, which were found both inshore and offshore. In addition, a number of plankters were found only in the open waters of the Gulf. These included Cerato- corys horrida Stein. Some species were found only in open waters but on both coasts. This group consisted of Ceratium candelabrum (Ehr.) Stein, Pyrocystis fu- sijormis W. Thomson, and P. noctiluca Murray. Occasionally, the open water species were found inshore. Davis interpreted this as indicating an admixture of open water with the inshore water. Davis and Williams (1950) listed seven species from brackish water in mangrove areas of southern Florida. King (1950) listed 19 species of dinoflagellates from the west coast of Florida in a series of samples extending from inshore bays to a distance of 120 miles offshore and collected over a period of 10 months in 1949. About 10 of these species were not listed by Davis or Davis and Williams. Additional species have been found by John Howell, biologist. Fish and Wildlife Service (un- published data), along the west coast of Florida. Ceratium pentagonum Gourret occurred only at stations more than 30 miles offshore. A species of Pyrocystis (Gymnodinium) was present only ofl^shore except in one sample. In a study of samples collected throughout the year Howell found the most commonly occurring species of dinoflagellates to be Ceratium furca (Ehr.) Dujar- din and C. tripos (O. F. Muller) Nitzsch. Next in order of occurrence were C. macroceros (Ehr.) Vanhoffen, C.Jusus (Ehr.) Dujardin, C. trichoceros (Ehr.) Kofoid, C. massilliense (Gour.) Jorgensen Peridinium depressum Bailey, and Dinophysis caudata Saville-Kent. All of these appear to occur inshore as well as in the offshore waters of the Gulf. However, a more intensive study of the distribution of dinoflagellates along the coast may bring out more zonation than is at present apparent. The situation is complicated by the fact that typical open Gulf water with high salin- ity, low nutrient content, etc., sometimes extends up to the beach and, indeed, is carried into the bays by tidal action. Howell found 11 species not reported by Davis or King. In addition to those listed above, there were 4 species of Ceratium: C. carriense Gourret, C. horridum Gran., C. Jalcatum (Kof.) Jorgensen, C. praelongum (Lem.) Kofoid. The last-named was found only once and is typical of a large number of very rare species which may be expected to be found occasionally in the open Gulf waters if any extensive investigation of these waters is made. Other rare species found by Howell were Pyro- cystis hamulus Cleve, Pyrophacus horologicum Stein, Amphisolenia sp., Goniodoma sp., and Ornithocercus quadratus Schiitt. In a laboratory culture of Florida west coast water Oxyrrhis marina Dujardin flourished, and a large population developed. Despite the richness of the dinoflagellate fauna in the Gulf, the actual concentration in terms of populations is normally very low. The con- centration of dinoflagellates in numbers of cells per liter of sea water is usually less than 50 in the waters along the west coast of Florida. Yet, under unusual conditions which are still not clearly understood, a particular species may increase to enormous concentrations and cause serious dis- ruption of the normal biological balance in the area involved. Thus, in the Florida red tide of 1946 and 1947 the concentrations of Gymnodinium hrevis Davis reached 60 million cells per liter (Davis 1948). These enormous concentrations cause the water to turn color, usually a brownish red, producing what is commonly called "red water" or "red tide." ' Such concentrations of dinoflaggeUates are frequently accompanied by the death of fish ' Red tide in the Gulf of Mexico waters is discussed in an article by R. Lasker and F. O. Walton Smith pp. 173-176. GULF OF MEXICO 225 and other marine animals. There is every reason to bcHevp that many species of dinoflagcllates elaborate an extremely potent toxin either nor- mally or under the conditions of population crowding. The two blooms cited above were associated with serious "fish kills" and death of much of the marine life in the area. The presence of even normal numbers of dino- flagellates in the water may cause shellfish to become unfit for human consumption. Thus, reg- ularly during the summer months the California sea mussel (Mytihis californianus) is likely to be lethal to humans when Gonyaulax catenella Whedon & Kofoid is abundant in the coastal water (Sommer et al., 1937), and the clams in certain areas of the Bay of Fundy are regularly toxic when Gonyaulax tamarensis Lebour occurs in the plankton (Medcof et al., 1947). Paralytic shellfish poisoning caused by eating such toxic shellfish has not been reported from the Gulf of Mexico. Connell and Cross (1950) found a dino- flagellate resembling Gonyaulax catenella associ- ated with the death of fish in Offatts Bayou, an inlet of Galveston Bay, in 1949. Unfortunately, no specific identification of this organism was made. There is also strong evidence that the fish kills which regularly occur in Offatts Bayou are generally caused by the production of hydrogen sulfide or to suffocation due to stagnant conditions at the inner end of the inlet (Gunter 1942, 1951) rather than by a dinoflagellate bloom. Toxic red water such as occurs regularly in the pearl oyster beds in Japan (Mitsukuri 1904) could be disastrous to the vast oyster industry in the Gulf, but apparently the Gulf oysters have been spared any such visitation so far. Reports of red water on Campeche Banks, off Yucatdn, are made occasionally by fishermen in that area, but to date it has not been possible to ascertain the causative agent. It is quite possible that a dinoflagellate is involved. One of the great difficulties in dinoflagellate research is the fragility of the naked forms. Many of these are almost impossible to preserve but must be studied alive under the microscope. This feature might not be serious if the organisms were easily cultured, but they are notoriously difficult to grow in the laboratory. The classical monograph of the unarmored dinoflagcllates by Kofoid and Swezy (1921) was based largely on examination of living specimens which regularly dissolved before the eyes of the workers as they stutiied them. The Florida red tide was caused by such a naked form, G. hrevii, which does not preserve in formalin. Special fixatives such as Bouin's solution and Schaudinn's solution do pre- serve some of these species but not without distortion. However, a rich fauna of unarmored forms is not normally present inshore at Sarasota, Florida, where the workers of the Fish and Wildlife Service laboratory in their search for G. hrevis have exam- ined living material for 2 years and failed to reveal any G. hrevis. They foimd only three other species of unarmored dinoflagcllates. More work in other areas must be conducted before this problem can be solved. The difficulty in making specific identification of dinoflagellates has lead to a paucity of records of these interesting and important organisms. Painstaking microscopic work on the part of a specialist is necessary for the differentiation of many species, even of the thecate forms which preserve well. In these species, an analysis of the plate pattern is necessary for identification. Few general plank- tologists have either the time or traming to pursue this kind of work which involves difficult micro- orientation and dissection. Concentrated study by a number of specialists for a considerable period of time will be necessary before the dinoflagellate plankton of the Gulf will be adequately revealed to science. Since most of the pelagic tropical species of dinoflagellates are worldwide in distribution, published works for other areas can be used for a study of the Gulf fauna. The most important of these are listed in the bibliography. Lebour's (1925) work is designed for northern seas but includes many tropical species. It is a very useful treatise, especially for a beginner who needs orientation. Kofoid and Swezy 's (1921) mono- graph is a classic on the naked forms but must be augmented by later papers. Kofoid and Skogs- berg's (1928) Dinophysoidae is another classic and covers that group in a comprehensive manner. The Heterodiniidae has been monographed by Kofoid and Adamson (1933). Most of the Peridiniidae are in need of monographic treatment. It is very difl[icult to identify the smaller species with present literature. For the Ceratia Jor- gensen's (1911) monograph and Graham and 226 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Bronikovsky's (1944) treatise on Carnegie Ceratia are' quite useful. The most comprehensive sys- tematic treatment of the dinoflagellates as a group is Schiller's Dinoflagellata in Rabenhorst's Cryptogamen-Flora (1931-37). The reports of the larger world expeditions complete the general literature on dinoflagellate taxonomy. Such ref- erences are included in the bibliography. BIBLIOGRAPHY Brongersma-Sanders, M. 1948. The importance of upwelling water to vertebrate paleontology and oil geology. Koii. Ned. Ak. Wet., Verh. Afd. Nat. (Tweede Sectie), Dl. XLV, No. 4, 112 pp. Amsterdam. CoNNELL, C. H., and Cross, J. B. 1950. Mass mortality of fish associated with the pro- tozoan Gonyaulax in the Gulf of Mexico. Science 112 (2902): 359-363. Davis, C. C. 1948. Gymnodinium brcvis sp. nov., a cause of discolored water and animal mortality in the Gulf of Mexico. Bot. Gaz. 109 (3): 358-360. 1950. Observations on plankton taken in marine waters of Florida in 1947 and 1948. Quart. Jour. Florida Acad. Sci. 12 (2): 67-103. and Williams, R. H. 1950. Brackish water plankton from mangrove areas in southern Florida. Ecology 31 (4): 519-531. Galtsoff, p. S. 1948. Red tide. A report on the investigations of the cause of the mortality along the west coast of Florida conducted by the United States Fish and Wildlife Service and cooperating organizations. U. S. Dept. Int., Fish and Wildlife Service Sp. Sci. Rept. 46: 1-39, 9 figs. Graham, H. W., and Bronikovsky, N. 1944. The genus Ceralium in the Pacific and North Atlantic oceans. Scientific results of cruise VII of the Carnegie during 1928-1929. Biology-V. Car- negie Inst. Washington Pub. 565, 209 pp. GUNTER, G. 1942. Offatts Bayou, a locality with recurrent summer mortality of marine organisms. Am. Mid. Nat. 28 (3): 631-633. 1951. Mass mortality and dinoflagellate blooms in the Gulf of Mexico. Science 113 (2931): 250-251. Smith, F. G. W.; and Williams, R. H. 1947. Mass mortality of marine animals on the lower west coast of Florida, November 1946-January 1947. Science 105 (2723): 257. -Williams, R.H.; Davis, C. C; and Smith, F. G. W. JORGBNSEN, E. 1911. Die Ceratien. Eine kurze Monographie der Gattung Ceralium Schrank. Inteinat. Rev. ges. Hydrobiol. u Hydrogr., 3, suppl., 124 pp., 10 pis. 1920. Mediterranean Ceratia. Rept. Dan. Oceanogr. Exped. 1908-1910 to the Mediterranean and adjacent seas 2 (1): 1-110, 94 text figs., 26 charts. Karsten, G. 1906. Das Phytoplankton des atlantischen Ozeans. Wissensch. Ergeb. Deut. Tiefsee Exped. 2: 137-219, pis. 20-34. King, J. E. 1950. A preliminary report on the plankton of the west coast of Florida. Quar. Jour. Florida Acad. Sci. 12 (2): 109-137. KoFOiD, C. A., and Adamson, A. M. 1933. XXXVI: The Dinoflagellata: The family Hetero- diniidae of the Peridiniodiae. In: Reports on the scientific results of the expedition, etc. Mem. Mus. Conip. Zool. 54 (1): 1-136, 22 pis. and Skogsberg, T. 1928. The Dinoflagellata. The Dinophysoidae. In: Scientific results of Albatross expedition, 1904-1905. Mem. Mus. Comp. Zool. 51: 1-766, 31 pis. and SwEZY, 0. 1948. Catastrophic mass mortality of marine animals and coincident phytoplankton bloom on 'the west coast of Florida, November 1946 to August 1947. Ecol. Monog. 18: 309-324. Herdman, C. E. 1924. Notes on dinoflagellates and other organisms causing discoloration of the sand at Port Erin, IV, Trans. Liverpool Biol. Soc. 38: 75-84. 1921. The free-living unarmored Dinoflagellata. Mem. Univ. California 5: 1-538. Lebour, M. V. 1925. The dinoflagellates of northern seas. Plymouth: Mar. Biol. Assn. U. K., 250 pp. Medcof, J. C; Leim, A. H.; Needler, A. B.; and Need- LEB, A. W. H. 1947. Paralytic shellfish poisoning on the Canadian Atlantic coast. Bull. Fish. Res. Bd. Canada 75: 1-32. MiTSUKURI, K. 1904. The cultivation of marine and freshwater animals in Japan. Bull. U. S. Bur. Fish. 24: 259-289. Riley, G. A. 1938. Plankton studies. I. A preliminary investiga- tion of the plankton of the Tortugas region. Jour. Mar. Res. 1 (4): 335-352, figs. 101-104, tabs. 4-7. Schiller, J. 1931-37. Dinoflagellata. In: L. Rabenhorst's Krypto- gamen-Flora. 10 (3): 1-617; zweiter Teil (Peri- dineae) : 1-589. ScHtJTT, F. 1895. Die Peridineen der Plankton Expedition. Parti: Studien iiber die Zellen der Peridineen. Ergebn. Plankton Exped., vol. 4, M, a., 170 pp., 27 pis. Smith, F. G. W. 1949. Probable fundamental causes of red tide off the west coast of Florida. Quar. Jour. Florida Acad. Sci. 11 (1): 1-6. Sommer, H.; Whedon, W. F.; Kofoid, C. A.; and Stohler, R. 1937. Relation of paralytic shell-fish poison to certain plankton organisms of the genus Gonyaulax. Arch. Path. 24: 537-559. PRESENT STATUS OF DIATOM STUDIES IN THE GULF OF MEXICO By Paul S. Conger, Smithsonian Institution Very little concerted work has been done on the diatoms of the Gulf of Mexico region to date. Considering its size and diversity of habitat, the Gulf is a virtually untouched area in this regard. The few studies made have been of a somewhat casual, quite limited, and localized nature leaving almost the entire shoreline and open water area of the Gulf completely unexplored. Previous records are confined mainly to the southwest corner of the Gulf (Campeche Bay), Mobile Bay on the north, the west coast of Flor- ida (Tampa and Pensacola Bays), the Dry Tor- tugas, and a few in the West Indies, with frag- mentary, unpublished records from a few other places. Few, or almost none of these (see bibli- ography), are well-defined floristic studies. A number of works on diatoms of Honduras and Caribbean waters, not within the Gulf region but closely allied to it in character of flora, add useful supplementary records. Most of the previous efl^orts have been con- cerned with mere identification of species with very little data as to precise location, date of occurrence, and habitat. Many of the early listings are included in Schmidt's Atlas der Dia- tomaceenkunde (1876) with references only to the locality but without any further information. Despite the dearth of published records and the very limited territory explored the writer was able to compile from several sources a list (un- published) comprising some 60 genera and about 500 species and varieties. The list is incomplete, however, and gives no assurance of what diatoms one may expect to find in the Gulf, because vir- tually no work has been done so far on the pelagic species, their succession and seasonal fluctuations. The diatom flora of many shallow water indenta- tions of the shoreline, of swamps and reefs will also require further studies. ' Published with the permission of the Secretary of the Smithsonian Institution 239534 0—54 16 LITERATURE In the appended bibliography are given only those papers which apply specifically to the Gulf or Caribbean waters and such few general works which include the forms found there. For re- liable description of the species concerned it is necessary to consult such useful works as A. Schmidt's Atlas der Diatomaceenkunde (1876), H. Van Heurck's Synopsis des Diatomees de Belgique (1880-85); and H. and M. Peragallo's Diatomees Marines de France (1897-1908). Many of the papers dealing specifically with Gulf dia- toms are merely lists of species or brief unillus- trated accounts which cannot be used for iden- tification. The distribution of many diatoms is so wide- spread that it is sometimes necessary, and quite satisfactory, to rely for their identification on literature pertaining to areas entirely remote from the one in question. This is true not only of the free-floating species, but also of many bottom-dwelling and attached forms, such as, for instance, Melosira sulcata and Actinoptychus undulatus, which, despite a sedentary existence, are widely dispersed. The standard plankton works of Gran, Nor- disches Plankton (1905), and Marie Lebour's Plankton Diatoms of Northern Seas (1930), will be found applicable to a goodly number of tropical forms, especially the Rhizosolenias and Chaetoceros species, and other typical plankton diatoms although there may be some species in the Gulf waters which will not be found in these publications. CAMPECHE BAY Mann (1925) called attention to the remarkable correspondence between the diatom flora of the Campeche Bay in the Gulf of Mexico to that of the waters around the Philippine Islands. The list included by him in the introduction to his paper contains 78 forms common to both places 227 228 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE including 28 not found elsewhere. Both floras are characterized also by a number of remarkable species of Campy Iodise xis. As an explanation, Mann implies the possibility of parallel develop- ment and discoimts the idea of transfer or dispersal between the two localities. Other workers take exceptions to the whole idea of attaching any significance to the common appearance of diatom species in the two widely separated areas. At least, it is an interesting observation and one not to be neglected. Among the Campeche Bay diatoms, mostly registered in Schmidt's Atlas (1876-) are many species and varieties bearing the name campe- chiana, such as Amphora crassa Greg. var. campe- chiana Grun., A. grevilleana Greg. var. campechiana Grun., Campylodiscus campechianus Deby, Coc- coneis campechiana Cleve, Cosinodiscus gemifer Ehr. var. campechianus Ratt., C. marginulatus Ratt. var. campechiana Grun., Endictya campe- chiana Grun., Glyphodesmis campechiana Boyer, Navicula campechiana Grun., Nitzchia campechiana Grun., Stephanopyxis campechiana Grun., Surirella campechiana Hust., Triceratium campechianum (Grun.?), and others, indicating a very diverse and novel flora. Yet we have little information as to the exact source and extent of the material from this sizeable area, and it is likely that more thorough and careful survey may add new findings to this apparently most interesting locality. If the great diversity of the Campeche Bay diatom flora and the yield of new forms is any indication of what might be expected from ex- amination of other places in the long stretches of unexplored shore line of the Gulf, interesting pros- pects are in order. It must be remembered, however, that the yield of new forms from Cam- peche Bay came mostly many years ago when fewer species were known from other places. MOBILE BAY Probably one of the more intensivel}' studied areas of the Gulf coast thus far is Mobile Bay. A list of diatoms from this area published by Cunningham (1889), one of the few diatom stu- dents local to the Gulf area, includes 37 genera and 137 species, but is probably far from complete. Cox (1901) who identified the diatoms in Cunning- ham's collection, furnished a useful but clearly incomplete list of 29 genera and 62 species. This material obtained from George H. Taylor, Wm. McNeil, and his own collecting, includes typically fresh water, brackish, and marine forms. Since Cox specifically says that all the specimens are from Mobile Bay it is obvious that fresh water species in this collection were brought in by streams. This list is also correlated with records of George H. Taylor from Tampa Bay. One form from salt marshes at Mobile found in Cunningham's material and named by Grunow is sufficiently remarkable and well known to deserve particular mention. It is Terpsinoe intermedia Grun., a diatom of abnormal structure with quite symmetrical adjutment on the central, valve face (see Schmidt's Atlas, 1876, plates 198- 200). The species is closely related to T. musica Ehr., typical of the Gulf coast. It is evidently plentiful in its original locality near Mobile. TORTUGAS AND WEST COAST OF FLORIDA Extensive collections made by the writer at Tortugas and around Tampa Bay are in process of study, and some observations based on them are included in this summary. George H. Taylor made records from Tampa Bay as above cited. Mann prepared a list of diatoms of Pensacola Bay. The writer's report (unpublished) on plankton diatoms of the west Florida coast, off Tampa and Fort Myers, to E. Lowe Pierce of the Univer- sity of Florida, includes 35 genera and 82 species and varieties. Some species of Chaetoceros and Hemidiscus included in this list were found in heavy concentrations, a fact which indicates that Gulf coastal waters are, at times, very productive. From the studies mentioned above an inference may be drawn that mixed calcareous and organic muds of the west coast of Florida provide favorable environment and adequate supply of nutrients to support a generally rich and varied diatom flora which includes, conspicuously, forms like Terpsinoe musica, Biddulphia rhombus, Isthmia capensis, Auliscus, Aulacodiscus, Navicula, and others. OTHER RECORDS Diatom records made in connection with oil- pollution investigations conducted in Louisania by the biologists engaged by oil companies and by persons representing various conservation and fishery interests have not been published and are not generally available. They are probably rather limited since these investigators have not been GULF OF MEXICO 229 prepared to give consistent attention to the studies of diatoms and were primarily concerned with other problems. Mention may be made here of the observation by Willis Hewatt of Texas Christian University (personal communication) that Biddulphia mobilensis periodically produces very heavy concentrations off the Louisiana coast near Grand Isle. This area, and probably also the coasts of Alabama to Texas, would seem to be optimum environment for this species. DIATOM FLORAS OF GULF AND ADJACENT WATERS At the present state of our Imowledge there is no basis for correlating diatom floras of the Gulf and adjacent areas or for discussing theii- mutual effects. Currents that swing into the Gulf from the Caribbean on the southeast and out through the Florida Straits on the northeast must, of course, carry their complement of plankton dia- toms; but, until more is known of both the Gulf diatom flora and that of the adjacent waters outside, no definite information can be given regarding the effect of one on the other. As has been said, practically nothing is known specifically of the Gulf diatom plankton or, for that matter, of that in adjacent tropical waters. The mere presence of similar population con- stituents in the adjacent areas does not necessarily imply any direct relationship between them. It is quite possible that the greater sweep of the Gulf Stream tends to some extent to isolate the Gulf of Mexico from the adjacent seas despite the movement of some of the Atlantic and Caribbean waters through the Gulf. With the bottom-living and attached species seemingly not so readily subject to dispersion, there is not enough difference of conditions, say, on the east and west coasts of Florida or the envu'ons of Cuba, and there is so much correspond- ence in certain conspicuous species, such as Terpsinoe musica, T. americana, Nitzschia para- doxa, Grammatophora marina, Biddulphia penta- crinus, Baphonevt surirella, Surirella reniformis, and members of the genera Coscinodiscus, Cam- pylodiscus, Biddulphia, Navicula, that in our present state of limited knowledge it is not feasible to give any general statements of significant relationship. It would seem that a very large variety of species find the waters both inside and outside the Gulf a suitable habitat, but it will take a great deal of more detailed collecting and comprehensive study to disclose any significant floristic differences or migrational influences within these areas. ECOLOGY The literature on the diatoms of the Gulf area contains practically nothing concerning their ecology and economic importance. The designa- tion of species as fresh water, brackish, or marine is about the extent of ecological data. Yet, both subjects should be of great interest. One may expect that careful studies of many diverse habi- tats represented along the shorelines of the Gulf, and in its open waters could give valuable data regarding habitat characteristics, optimal range of the different species, and their seasonal occur- rences. The effects of the discharge of particulate matter by the Mississippi and other large rivers on the distribution and productivity of diatoms in the open waters constitutes another important problem. Relation of the diatoms as a vital chain in the marme food cycle is also of great interest because of the extensive shi'imp. oyster, and fishery industries of the area. Such ecological studies of the diatoms correlated with theu- floristic survey may well contribute to general knowledge of the Gulf and will be helpful in understanding its specific problems. PRODUCTIVITY It has long been held that productivity of plank- ton diatoms in tropical and subtropical waters is in general lower than in colder regions. This, in the writer's experience, appears to be generally true, but the statement should be taken with some qualifications for there are instances in which, owing to a particular combination of local conditions, it does not hold. Even in tropical waters certain areas may contain heavy concen- trations of diatoms. There is for instance evi- dence of occasional unaccoinitable surges of cer- tain species, as Hemidiscus. Biddulphia mobilensis and Isthmia capenms about Tortugas and in othei' places for which the causative factors are not known. Because of the presence of very delicate, transparent and minute forms that pass through the meshes of the plankton net, the Gulf plankton may at times contain a greater number of indi- vidual diatoms and be more productive than 230 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE meets the eye of the casual observer. Examples of such occurrences are given in the next section on silica relations. Although a phytoplankton tow in the very clear subtropical Gulf water will usually disillusion and disappoint the investigator used to northern collecting, he must be alert both in observation and method not to miss or lose the delicate and minute forms present. The first adequate quantitative studies of diatom plankton productivity in the Gulf were made at Tortugas by Riley (1938). His work, based on Harvey's method of extraction of plank- ton pigments, and on measurements of oxygen changes in suspended clear and dark bottles (method of Marshall and Orr), gives indices of reliable value. It might be added that, espe- cially with the phantom-like diatom plankton, these methods are dependable, while errors and uncertainties of sampling with quantitative plank- ton net and of cell counts would give deceptive results. Comparing plankton productivity at Tortugas with that of Long Island Sound, Riley found that the amount of total plant pigment from Tortugas plankton was only one twenty-fifth that of the Long Island area. On the other hand, oxygen production in suspended bottles was one- third to one-half as much in the former as in the latter area. It would seem evident, he says, "that actual productivity is much greater than the standing crop would indicate." The results are subject to qualification with respect to a number of altering factors which are discussed in Riley's report. The limited period covered by Riley's observa- tions may or may not have been a favorable one for comparison, and further investigations of this character extended to other places in the Gulf and other times of the year, are clearly needed. Another problem about which information to date is both meager and vague concerns the rate of turnover and renewal of the population, espe- cially of the small diatom species such as members of the genera Nitzschia, Synedra, Dimmerogramma, Grammatophora, Amphora, Raphoneu. The esti- mation of the so-called "standing crop" of phy- toplankton growth is a standard and fairly satis- factory practice, but an adequate evaluation of the amount of transformation of organic sub- stance over a specified period of time is fraught with a complication due to the constant break- down and renewal of population elements, in which the reproductive rate is rapid and the life span is short. Especially is this true where the plankton is very poor as it is frequently in the Gulf waters. Knowledge of the general occurrence and suc- cession of the Gulf flora is too meager to make any reliable statements as to the relative impor- tance of the various diatoms for there are very many of the species mentioned, and perhaps others, that occur at times in large numbers. Just a few, however, that are definitely typical of the region, though by no means restricted to it might be cited: Biddulphia mohiliensis (Bail.) Grun., Terpsinoe musica Elu-., and Hemidiscus hardmannianus (Grev.) Mann. Further study will certainly add many others that periodically occur in abundance in different parts of the area. SILICA RELATIONSHIPS In the waters of tropical seas, poor in silica and other nutrients, the diatoms of wide or cosmopoli- tan distribution are smaller and have frailer shells than are to be found in the same species from waters of temperate and northern latitudes. The variety of species is not less in the tropics, nor is there necessarily a smaller number of individuals, but the size and robustness of their cells is dimin- ished. Although this observation is applicable, in general, to species found both m tropical and in temperate seas, certain forms may be cited as notable examples, namely, Synedra undulata (trop- ical form often half the length of its northern counterpart), Biddulphia pulchella and B. penta- criniis, Surirella reniformis, Grammatophora ma- rina, Isthmia sp., and others. On the contrary, some typically warmer water forms, like Raphoneis surirella do not appear to grow larger, heavier shells in richer waters of northerly latitudes. The plankton diatoms of the waters containing minimum amount of dissolved silica are diapha- nous, as for example, the Chaetoceros, large-celled Hemidiscus and Coscinodiscus species found in the Gulf plankton. These latter, and similar forms, may be both large and numerous, but their bodies are so watery and their shells so lightly silicified that they are very transparent and are easy to overlook. Numerous minute-celled forms such as small Nitzschia, Cocconeis, Dimmerogramma, Synedra, Grammatophora, and Amphora species, common in GULF OF MEXICO 231 the Gulf frequently are found in silica poor waters, while larger heavy-shelled forms {/ihizosolenia, Coscinodiscus, Biddulphia sp.) sometimes found in cooler, northern waters, are not present in the tropical or subtropical plankton unless reduced in size or weight of then- silica shells. These obser- vations are general and at present not based on extensive quantitative measurements whidi, how- ever, are being planned by the author. Further observations by the wi-iter, although not quantitative, stronglj' suggest that wherever there is a substantial influent of silica-bearing water, the diatom growth is both more abundant, and the cells (and their shells) are of a more robust character. Such a condition was noticed, for in- stance, at Tortugas in close proximity to the crumbling walls of siliceous brick of old Fort Jefferson, washed on all sides by the shallow cal- careous water. In the moat and in semicnclosed pools adjacent to these walls a very heavy growth of Tropidoneis lepidoptera and other diatoms was noted. The more extensive result of such rela- tions, however, is to be seen in areas influenced by the discharge of river systems that drain argil- laceous soils, or in the inshore waters affected by the run-off from steeper siliceous terrain, such as found around the coast of Cuba, the west coast of Florida and the coast of Alabama. Waters of such constitution support heavy growths of robust shelled diatoms as Terpsinoe musica, Biddulphia pulchella, Hydrosera triquetra, Lithodesmium, and others. The contrast of the rich diatom flora produced in such an envu-onment with the frail and delicate plankton forms of the silica-poor calcareous waters about Tortugas, for example, appears to be a demonstration of a point long suspected by the writer that a plentiful supply of silica greatly enliances the growth of diatoms. Evidence from other regions and types of habitat, in the writer's experience, supports this contention. Where richer waters with a higher silica content occur in tropical i-egions owing to cold currents, upwelling, or run-off from siliceous soils, a heavy diatom productivity, with oftentimes more robust individuals is the result. The relation of diatom growth to silica content of sea water is imdoubtedly significant but not too well understood. The varied conditions of the Gulf of Mexico afford good opportunity for such study. The effects of phosphates, nitrates, and other nutritive elements should be examined coor- dinately although it does not appear from the present observations that they could be confused with the role of silica as a limiting factor. BIBLIOGRAPHY Bailey, J. W. 1844. Review of Ehreriberg's Verbreitung und Einfluss der mikroskopischcii LebeiKS in SUd- und Nord- Amerika. Am. .Jour. Sci. and Arts 46: 297-3 IH. BOYER, C. S. 1926. Synopsis of North American Diatomaceae, Part I. Coscinodiscatae, Rhizosolenatae, Biddulphiatae, Fragilariatae. Proe. Acad. Nat. Sci. Philadelphia 78 (Supp.): 1-228. 1927. Synopsis of North American Diatomaceae, Part II. Xaviculatae, Surirellatae. Proc. Acad. Nat. Sci. Philadelphia 79 (Supp.) : 229-583. Cleve, p. T. 1878. Diatoms from the West Indian Archipelago. Bihang. Kongl. Svenska Vetenskaps-Akad. Handl. 5 (8): 1-22, pis. 1-5. (Translated into French, with plates, by J. Pelletan in: Jour, de Micrographie, 1879.) Cox, J. D. 1901. .\lgae. In: C. Mohr, Plant Life of .Alabama. Contr. U. S. Nat. Herb. 6: 142-148. Cunningham, K. M. 1889. The diatoms of Mobile, Alabama. The Micro- scope 9 (4): 10,5-108. Ehrenbebg, C. G. 1841 (1843). Verbreitung und einfluss der mikroskopi- schen lebens Slid- und Nord-Amerika. (On the ex- tent and influence of microscopic life in South and North America. With a list of the diatoms.) Abhandl. Konigl. Akad. der Wissenschaften zu Berlin, March 25 & June 10, 1841: 291-446, pis. 1-4 (colored). (Reviewed with extracts, by J. W. Bailey: Am. .lour. Sci. and Arts 46: 297-313. 1844.) 1842. On the extent and influence of microscopic life in South and North America. (With a list of the diatoms.) Microsc. Jour, and Struct. Record 2: 24-. (From: .\bhandl. Konigl. Akad. der Wis.senschaften zu BerUn, 1841.) Greenleaf, R. C. 1866. On the diatoms and other microscopic objects found in soundings from the Gulf of Mexico, between Sand Key and Elmoro, made by Henry Mitchell of U. S. Coast Survey. Proc. Boston Soc. Nat. Hist. 11: 79. Greville, R. K. 1857. Description of some new diatomaceous forms from the West Indies. Quar. Jour. Microsc. Sci., 5: 7-12, pi. 3. 1866. Descriptions of new and rare diatoms from the tropics and Southern Hemisphere. Trans. Bot. Soc. Edinburgh 8: 436-441, pi. 6. Edinburgh New Philosophical Jour., 1866. 232 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Mann, Albert. 1925. Marine diatoms of the Philippine Islands. U. S. Nat. Mus. Smithsonian Inst. Bull. 100, Vol. 6, Pt. 1, pp. 1-182, 39 pis. (Diatoms of Campeche Bay, Gulf of Mexico, in the introduction, pp. 5-8.) 1936. Diatoms in bottom deposits from the Bahamas and the Florida Keys. Carnegie Inst, of Washington, Pub. 452. Pap. from Tort. Lab. 29:121-128. OsoRio Tafall, B. F. 1943. Hallazgo de la diatomea Biddulphia sinensis Greville en aguas del Golfo de Mexico. Ciencia 4 (8-10) : 225-230, figs. 1-8, 2 maps. Pelletan, J. 1878-79. Diatomdes de I'archipel des Indes occidentales par P. T. Cleve. (French translation with the original plates.) Jour, de Micrographie, Vol. 2 & 3. Riley, G. A. 1938. Study of the plankton in tropical waters. Ann. Rep. Tortugas Lab., Carnegie Inst. Washington, Yearbook No. 37 (1937-1938, p. 98). Riley, G. A. — Continued 1938. Plankton studies. I. A preliminary investigation of the plankton of the Tortugas region. Sears Foun- dation: Jour. Mar. Research 1 (4): 335-352, figs. 101-104, tabs. 4-7. Schmidt, A. 1876. Atlas der Diatomaceenkunde. 460 pis. (folio). Leipzig, Germany. Stodder, Chas. 1883. Notes sur les diatomdes de Tampa Bay, Florida. Jour, de Micrographie, Vol. 7. Tempere, J., and Peragallo, H. 1894. 1915. Diatom^es du Monde entier. Text*. Tables. Collection of Tempere and Peragallo. First Ed., 1894, 350 pp. Second Ed., 1915, 2 Vols., 480 and 68 pp. Wolle, Francis. 1890. Diatomaceae of North America. 112 pis., 2,300 figs. Bethlehem, Pa. CHAPTER VII PROTOZOA GULF OF MEXICO FORAMINIFERA By Fred B. Phleger and Frances L. Parker,' The Scripps Institution of Oceanography, University of California Foraminifera are relatively large, marine Pro- tozoa having either a calcareous or an arenaceous test; they are both benthonic and planktonic in habitat. Their tests contribute a large percentage of the material in marine sediments. Study of Foraminifera has been mostly confined to the occvu-rencc of empty tests m marine sediments, and all identifications are based upon test morphology. Little is known of Gulf of Mexico Foraminifera except from the Dry Tortugas and from the north- west area. Phleger (1951) and Phleger and Parker (1951) have studied living and dead assemblages from plankton tows and cores taken off shore between Point Isabel and Atchafalaya Bay, and the present report is largely a summary of the per- tinent features of that work. These samples were collected from 551 stations spaced in 12 traverses extending fi-om the 10-fathom curve to the center of the Sigsbee Deep. Flint (1899) and Cushman (1918-31) have described material collected by the United States Bureau of Fisheries ship. Albatross, from the northern part of the Gulf of Mexico east of the Mississippi Delta. Kornfeld (1931) de- scribed some shallow-water and littoral Fora- minifera from a few stations between the Missis- sippi Delta and the International Boundary. Cushman and Bermudez (1945) reported a new species of Rotalia from the mouth of the Rio Grande. Cushman (1922) has described numer- ous species from the shallow-water areas of the Tortugas. BENTHONIC FORAMINIFERA The area investigated in the northwest Gulf of Mexico between the Mississippi Delta and the International Boundary is one of clastic sediments. Clastic sediments also occur east of the delta as far as Mobile Bay and along the coast of Mexico. ' Contribution from the Seripps Institution of Oceanography, New Series No. 660, Contribution No. 16, Marine Foraminifera Laboratory. Work done on Office of Naval Research Project NR 081 060. The continental shelf bordering Louisiana and Texas has numerous isolated calcareous reefs. The principal calcareous areas in the region are along the coasts of Florida and Yucatan. The Foraminifera assemblages in these two sedi- mentary environments are quite distinctive and are treated separately in the following summary. The most extensive sampling and study has been done in the clastic sediments. Clastic areas. — Figures 55 through 58 list the principal benthonic species found in the northwest Gulf of Mexico; this figure is reproduced from Phleger (1951). The depth range shown for each species is a generalization based upon distributions from samples in all 12 traverses taken. This assemblage is related to the Atlantic assemblage but contains some elements reported only from the Gulf of Mexico. The benthonic faunas in the northwest Gulf may be grouped into six depth biofacies with boundaries at the following approximate depths: 100 m., 200 m., 600 m., 1,000 m., and 2,000 m. In addition, there are three subfacies in the upper 100 m. of water depth. The boundaries between these biofacies are not sharp but vary through about 10-20 percent of the depth involved. Figure 59 summarizes the depth of biofacies and gives depth ranges of representative species as an illustration of the basis for distinguishing the facies. The most striking depth biofacies boundary in this area is at about 100 m. This coincides with the depth of the water layer which is affected by changing seasons and therefore shows seasonal temperature ranges, in which the greatest organic production occurs, and which is turbulent, at least in part. Deeper biofacies boundaries may be correlated with the temperature ranges if they occur in the permanent thermocline. The bound- ary at about 2,000 m. is believed to be due to some environmental factor other than temperature, since there is no significant temperature change 235 236 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE DEPTH IN METERS 100 200 300 400 500 1000 2000 3000 obaculites cf . foliaceus (H. B. Brady) Angulogerina bella Phleger and Parke Asterigerina carinata d'Orbigny Bifarina advena (Cushinan) rrogularis Phleger and Parke albatrossi Cushrnan B. barbata Phleger and Parke B. fragilis Phleger and Parker B. goesii Cushman B. hastata Phlegtr and Parke B. lov/mani Phleger and Parke B. minima Phleger and Parke B. pulchella (d'Crbigny) var. primitiv Cushman npUx Phleger and Parker B. striatula Cushman var. spinata Cushman B. subaenariensis Cushman va subspinescens Cushman B. translucens PhUger and Parke L aculeata d'Orbigny aLazanensis Cushman marginata d'Orbigny spicata Phleger and Parke striata d'Orbigny var. mexica Cushman B. tenuis Phleger and Parke Buliminella cf. bassendorfensis Cushman B. elegantissima (d'Orbigny) Cancris oblonga {Williamson) Cassidulina crassa d'Crbigny C. curvata Phleger and Parke C. laevigata d'Orbigny var. carinata d'Crbigny rossi australis Phleger and Parker C. subglobosa H. B. Brady H h H h -\ h H h H h J L. Figure 55. — Generalized depth ranges of beithonic Foraminifera in the Gulf of Mexico. Solid lines indicate relatively greater abundance than dashed lines. GULF OF MEXICO DEPTH 100 200 300 237 IN M ETERS 400 900 1000 2000 3000 I r 1 r Chiloslomclld colina Schuag Cibicidcs conc-ntncus (Cushman) C. dcprimus Phleger and Park^- C. aff. floridanus (Cushman) C. io (Cushman) C. mollis Phleger and Parker C. robertsonianus (H. B. Brady) C. robustus Phleger and Parke C. umbonatus Phleger and Parke C. sp. 1 Cyclammina canceliata H. B. Brady Discarbvs bertheloti (d'Orbigny) D. candeiana (d'Crbigny) D. floridana Cushn Egger^la br^dyi (Cushman) Shrenbergina trigona Goe Elphidium discoidale (d'Orbigny) E. cf. [jmbriatulum (Cushman) E. gunteri Cole var. galveston ense ~Kornfeld ~* E, incertum (Williamson) var. KornUld Eponides antillarum (d'Crbigny) Phleger and Parker regularis phleger and Pjrke E. tumidulus (H. B. Brady) E. turgidus Phleger and Parlter nbon.itus (Reuss) Gaudryina cf. aequa Ciishman G. (F Si' ado gaudryina ) atlanticn (Bailey) Glomospir^ charoidcs {Jones a.nd Parker) Gyroidina orbicularis d'Orbigny G. saldanii d'Crbigny var. altitor: R. E. and K. C. Stewart * ~" HaplophragmoidiS bradyi (Robsrlson) H. glomeratum (H. B. Brod^:) H — h H — h H h H h -\ 1- H f- H h -l—f -I-+ H — h H — h H — h Figure 56. — Generalized depth ranges of benthonic Foraminifera in the Gulf of Mexico. Solid lines indicate relatively greater abundance than dashed lines. 238 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE D EPT H IN M ETERS 100 I r 200 "T" 300 400 500 1000 2000 n n T" 3000 HSglundina elegaDs (d'Orbigny) Karrerielld bradyi (Cushman) Labrospira sp. L^aticariniaa pauperata (Parker and Jones) LenlicuUna peregrina (Schwager) MargmuUna marginolinoides (Goes) M. planata Phleger and Parker L pyrula d'Orbigny N. sublineata H. B. Brady Nonion depressula (Walker and Jacob) ^ matagordana Kornfeld N. grateloupi d'Crbigny N. pompilioides (Fichtel and Moll) Nonionella atlantica Cushrr N. cl. opima Cushrr Parrella cuUur (Parker and Jones) Plauorbulina mediterranensis d'Orbigny Planulina ariminensis d'Crbigny rna Phleger and Parker P. foveolata (H. B. BraJy) ellerstorfi (Schwager) Proteonina comprima Phleger and Parke P. difflugiformis (H. B. Brady) Pseudoclavuhna mexicana (Cushman) Pseudoglandulina comatula (Cushman) Pseudoparrella ( ? ) decorata Phleger and Parker :igua [H. B. Brady) P. X 'M rugosa Phleger and Parker Pullenia buUoides (d'Orbigny) P. quinqueloba (Reuss) Pyrgo murrhma (Sch* P. cE. nasutus Cushrr Quinqueloculina bi cos lata d'Crbigny Q. compta Cushman -I 1 1 1 h -i h H 1- H h H 1 h H 1 f- H h H h H h H h H h H h H h H h H \- H h H h H h H h H h -\ 1 1 1 h H 1 1 1 h H h j- FiGURE 57. — Generalized depth ranges of benthonic Foraminifera in the Gulf of Mexico. Solid lines indicate relatively greater abundance than dashed lines. GULF OF MEXICO DEPTH 100 200 300 239 IN M ETE RS 400 500 1000 2000 3000 Quinqueloculina horrida Cushman Q. lamarckiana d'Orbigny Reophax dentaliniformis H. B. Brady R. scorpiurus Montfort Reussella atlantica Cushman Rotalia beccarn (Linne) var. parkinso (d'Orbigny) R. beccarii (L.inne) var. tepida Cushn R. pauciloculata Phleger and Parker R. rolshauseni Phleger and t^arker R. translucens Phleger and Parker Sigmoilina distorta Phleger and Parker S, schlumbergen Silvestri Siphonina bradyana Cushntan S. pulchra Cushnian Texttilaria foliacea Heron-Allen and Earland %'ar. occidentalis Cushtnan T. mayori Cushman T. mexicana Cushman Triiarina bradyi Cushman Trochammina advena Cushman T. ap. Uvigenna auberiana d'Orbigny var. laevis Goes U. flintii Cushn U. bispido-costata Cushman and Todd U, peregrina Cushman IJ, peregrina Cushman var. parvula Cushrr Valvulineria laevigata Phleger and Parke Virgxilina complanata Egger ana Cushman V, pontoni Cushman V. sptnicostala Phleger and Parker V. tessellata Phleger and Parke H h H h H 1 1 h H h H h H h H h H h H h -\ H H h H h H h H h H h H 1 h H h Figure 58. — Generalized depth ranges of benthonic Foramihifera in the Gulf of Mexico. Solid lines indicate relatively greater abundance than dashed lines. 240 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE DEPTH IN METERS 400 M 500 M 1000 M FtCIES I I FACIES 2 FAUNAL DEPTH FACIES 3 FACIES RQTALIA ROLSHAUSENI MARGINULINA PLANATA 1 h BIGENERINA IRREGULARIS CIBICIDES 10 ELPHIDIJM DISCOIDALE I I REUSSELLA ATLANTICA LX J L ELPHIDIUM MEXICA NUM \ - A ^ PLANULINA FOVEOLATA VALVULINERiA LAEVIGATA CYCLAMMINA CANCEL|.ATA | PARRELLA CULTUR PARRELLA CASSIDULINA CARINATA BULIMINA SPICATA i h PSEUDOPARRELLA DECORATA PLANULIN A WUELLERStIjRFI BOLIVINA LOWMANI H h + 500 M 1000 M BOTTOM WATER Figure 59. — Generalized chart showing depth biofacies of benthonic Foraminifera in the Gulf of Mexico and correlation between depth biofacies and temperature. Depth range lines are of benthonic Foraminifera used to illustrate types of depth distributions found. below the bottom of the permanent thermochne at about 800-1,000 m. Living specimens have been collected of 78 benthonic species. The greatest number of living specimens were found of the following species, all of which are characteristic of the facies above 100 m.: Bifarina advena (Cushman). Bolivina lowmani Phleger and Parker. B. strialula Cushman var. spinata Cushman. Butiminella cf. bassendorfensis Cushman and Parker. Cancris oblonga (Williamson). Cibicides concentricus (Cushman). Elphidium discoidale (d'Orbigny). Nonionella atlantica Cushman. Proleonina comprima Phleger and Parker. Rolalia beccarii (Liim6). Virgutina pontoni Cushman. The highest production rate of benthonic Foraminifera is in the upper facies, although the largest population of accumulated empty tests in bottom sediments usually is at intermediate depths. Calcareous areas. — The Foraminifera fauna of the calcareous areas is quite distinctive from that of the clastic areas and is dominated by Amphiste- gina lessonii d'Orbigny, a typical calcareous species. Cushman (1922) described the Foraminifera from several environments of the Dry Tortugas area off the southwest coast of Florida. The sampling was too scattered to give dependable results of the distribution in these environments, some being represented by only one or two sta- tions. For this reason, the following description GULF OF MEXICO 241 includes only tlie outstanding characteristics of the area. The area sampled is in shallow water with a maximum depth of 33 m. but chiefly 20 m. or less. The bottom sediment at the majority of stations is described as "fine white sand" or "sand" ; this is calcareous sand. The fauna closely resembles that of the general West Indies region which, in turn, is similar to the warm, shallow faunas of the Indo-Pacific. Cushman described about 150 species from the area. The following list incUules many of the most widely distributed and common species described: Amphistegina lessonii d'Orbigny. Archaias angulatus (Fichtel and Moll). A. compressus (d'Orbigny). Asterigerina carinala d'Orbigny. Bigenerina irregularis Cushman and Parker. Botivina piilchella (d'Orbigny). Cymbalopora squammosa (d'Orbigny). Discorbis candeiana (Cushman). D. mira Cushman. D. subaraucana Cushman. Elphidium discoidale (d'Orbigny). E. poeyanum (d'Orbigny). Trilociilinella circiilaris (Bornemann). Nonion grateloupi (d'Orbigny). Pyrgo siibsphaerica (d'Orbigny). Quinquelocidina agglulinans d'Orbigny. Q. lamarckiana d'Orbigny. Q. laevigata d'Orbigny. Rolalia rosea (d'Orbigny). Spiroloculina anlillarum d'Orbigny. Teitularia agglulinans d' Orbigny. T. candeiana d' Orbigny. Triloculina rotunda d'Orbigny. Virgulina punctata d'Orbigny. The Amphistegina fauna also is reported from an isolated calcareous reef area in the northwest Gulf of Mexico. PLANKTONIC FORAMINIFERA Planktonic Foraminifera are abundant in oft'- shore areas of the northwest Gulf of Mexico ofT the continental shelf both as accumulations of tests in the sediments and as living members of the planktonic population. Occasional concen- trations of planktonic specimens are found in shallow water. The planktonic fauna is domi- nated by great abundance of Globigerinoides rubra (d'Orbigny) and contains the following additional species in the surface bottom sediments: Candeina nitida d'Orbigny. Globigerina bulloides d'Orbigny. G. eggeri Rhumbler. G. inflala d'Orbigny. Glohigerinella acquilateratis (H. B. Brady). Globigerinoides conylobata (II. B. Brady). G. sacculifera (H. B. Brady). Globorotalia menardii (d'Orbigny). G. punetulata (d'Orbigny). G. scitula (H. B. Brady) G. truncalulinoides (d'Orbigny). G. tumida (H. B. Brady). Orbulina universa d'Orbigny. Putleniatina obliquiloculata (Parksr and Jones) Sphaeroidina bulloides d'Orbigny. Sphaeroidinella dehiscens (Parker and Jones). Living specimens of all but 6 of these species have been found in serial plankton tows taken from various depths of water at 27 stations occu- pied during February and March 1947. The average living planktonic Foraminifera popula- tion from these samples is about 5-6 specimens a cu. m. of water at 25-50 m. water depth, and much larger shallow-water populations are found in certain localities. Living specimens were col- lected at all depths of water sampled down to about 1400 m., but the largest population is in the upper layers at most stations. At a few sta- tions there was a larger population collected at considerable depth than from near the surface. Nine specimens of planktonic Foraminifera, com- prising six species, were found living on the surface of the bottom sediments. LITERATURE CITED Cushman, J. A. 1918-31. The Foraminifera of the Atlantic Ocean. U. S. Nat. Mus. Bull. 104, pts. 1-8. 1922. Shallow water Foraminifera of the Tortugas region. Carnegie Inst. Washington Pub. 311, 17: 1-8.5, pis. 1-14. and Bermudez, P. J. 1946. A new genus of Cribropyrgo and a new species of Rotalia. Contr. Cushman Lab. Foram. Res., pt. 4, 22: 119-120. Flint, J. M. 1899. Recent Foraminifera. Ann. Rep. U. S. Nat. Mus., 1897, pp. 249-349. KORNFELD, M. M. 1931. Recent littoral Foraminifera from Texas and Louisiana, Contr. Dept. Geol. Stanford Univ., no. 3, 1: 77-101. Phleoer, F. B. Ecology of Foraminifera, northwest Gulf of Mexico, Pt. 1, Foraminifera distribution. Geol. Soc. Amer. Mem. 46: 1-88. and Parker, F. L. Ecology of Foraminifera, northwest Gulf of Mexico, Pt. 2, Foraminifera species. Geol. Soc. .\mer. Mem. In press. PROTOZOA By Victor Sprague, Lake Chatugue Biological Laboratory The Protozoa considered here inchide all the orders recognized by Pearse (1949) excepting Dinoflagellata and Forminifera,^ these two groups being so abundantly represented in the Gulf of Mexico and relatively so well-known that they are given separate treatment. Nothing which is said below, therefore, is to be construed as apply- ing to those orders excepting when they are spe- cifically mentioned. An attempt has been made to list in this paper every protozoan which has been reported from the Gulf. Although it is believed that most of the important papers have been reviewed, it is quite possible that some of them have been overlooked. The number of species in any particular order which have been recorded in the literature per- taining to the Gulf does not by any means give an indication of the extent to which that order is actually represented there, since relatively only a very few studies on Protozoa of the Gulf of Mexico have been conducted. When each order is con- sidered below, therefore, not only are the reported species (if any) listed but a statement is usually made to indicate whether or not an investigator would expect to find numerous representatives of that group living under the conditions existing in the Gulf. For instance, one would not expect to find in the marine habitats many representatives of Euglenoidina or Heliozoa, which are predomi- nantly fresh water forms, or members of Hyper- mastigina, which are exclusively inhabitants of the alimentary canal of certain land dwelling insects. On the other hand, such orders as Radiolaria, which are exclusively marine, and Microsporidia, which are common parasites of invertebrates and lower vertebrates living in almost any conceivable habitat, are probably very ' The writer is indebted to Paul S. Oaltsort and Harold W. Harry for invaluable aid in obtaining pertinent literature and to Sewell H. Hopkins for criticism of one portion of the manuscript. > See articles by H. W. Oraham, Dinoflagellates of the Gulf of Mexico, pp. 223-226 of this book, and by F. B. Phleger and F. L. Parker. Gulf of Mexico Foraminifera, pp. 235-241. 259534 O— 54- -17 abundantly represented both in variety of species and numbers of individuals. To anyone interested in Protozoa of the Gulf of Mexico there is a striking contrast between the apparently limitless variety of species there and the very scant attention which protozoologists have given them. The semitropical climate and the great diversity of habitats found in the Gulf proper and its contiguous waters undoubtedly provide suitable environments wherein a corre- sponding diversity of species of free-living pro- tozoan fauna not only are able to live but can reproduce rapidly and flourish. The same favor- able conditions give rise, also, to a great abundance and variety of other invertebrates and fishes which serve as hosts of protozoan parasites. Numerous species of the parasitic Protozoa not only find suitable hosts, but the relatively high temperatures of the southern waters are accompanied by rapid multiplication of these parasites and, consequently, theu- occurrence in great abimdance. Although several of the species of Protozoa reported to occur in the Gulf were previously known ones, the over- whelming majority have been new. This fact alone suggests that any serious investigator would be riclily rewarded for his efforts by many dis- coveries. The Protozoa of the Gulf of Mexico, both free-living and parasitic, constitute one of the great American frontiers in protozoology. A few individuals have probed its fringes, but its thorough exploration is a task for future investi- gators to undertake. SURVEY OF THE LITERATURE The known Protozoa of the Gulf of Mexico (exclusive of Dinoflagellata and Foraminifera) are mostly free-living amoebae, ciliates (both free- living and parasitic), and Sporozoa. The first two groups have been studied chiefly along the Florida coast and the third along the coasts of Texas, Louisiana, and Mississippi, especially at Louisiana State University Marine Laboratory loc^ited on 243 244 FISHKRY BULLETIN OF THE FISH AND WILDLIFE SERVICE Grand Isle, La. Jacobs (1912) made physiological studies on four unidentified species of cOiates in- festing sea urchins in the vicinity of the former Biological Laboratory of Carnegie Institution at Dry Tortugas, a group of islands located approx- imately 60 miles west of Key West, Fla. Powers (1933 and 1935) studied about 13 species of ciliates (including those observed by Jacobs) at Tortugas, describing and naming 6 new ones. He described, also, one new flagellate. More recently, Wichter- man (1940, 1942, and 1942a) described 3 new cUi- ates from an oligochaete and 1 on coral, all at Tortugas. He observed in the same oligochaete host an unidentified gregarine. BuUington (1931, 1935, 1939, 1939a, and 1940) made a series of studies on 15 free-living ciliates at Tortugas, a dozen of which were new species, and observed many unidentified ones as well. Noland (1937) studied 18 species of free-living ciliates, 6 of which were new, at Bass Biological Laboratory, Engle- wood, Fla. Schaeffer (1926) has been the chief student of the amoebae. He made a series of studies which culminated in a lengthy paper on taxonomy of the amoebae with description of 23 (?) new species from Tortugas and Key West, Fla. Hopkins (1931) made life history studies on 2 of the same amoebae at Tortugas and 1 myce- tozoan. Apparently, Prytherch (1938, 1940) made the first noteworthy observations on a sporozoan of the Gulf of Mexico. He observed Nematopsis in oysters from Lake Barre and vicinity in Louisi- ana to Mobjack Bay, Va., and described the first member of the genus known in American waters. Later, Sprague (1949, 1950, 1950d, and this paper) studied 7 sporozoan parasites, 6 of them new, of mollusks and decapod Crustacea along the Louisi- ana coast. Mackin et al. (1950) described a sporozoan (?) parasite, Dermocystidium marinum,^ of widespread occurrence in oysters along the Gulf coast. Most of the other Protozoa consid- ered here have been mentioned only casually in the literature or called to the attention of the writer in personal correspondence. DISTRIBUTION OF PROTOZOA Most of the known Protozoa of the Gulf of Mexico have been reported as new species. 3 Taxonomic posirion of Dermocytifidium was rather uncertain. In 1952 Ray found that this microorganism is a fungus (Ray, Samray M., 1952, A Culture Technique for the Diagnosis of Infections with Dermocyslidiuin mnrinum Mackin, Owen and Collier, in Oysters, Science lir>- 360-3C1). These and the previously known ones have usually been reported only from particular localities. Not much about their general distribution, there- fore, seems to be known. We may reasonably suppose, however, that certain generalizations about distribution of free-living Protozoa else- where in the world may give us some idea about the expected distribution of those known in the Gulf since particular species generally tend to occur wherever the particular conditions favoring their life processes e.xist. Pertinent remarks on distribution of free-living forms can be found in Calkins' (1933, pp. 25-26) book on biology of Protozoa. The distribution of parasitic Protozoa is neces- sarily limited to that of their hosts. The hosts themselves are not generally so widely distributed as are the free-living Protozoa, one reason being, perhaps, that the means of dispersal available to them are somewhat more limited. Furthermore, distribution of parasitic Protozoa is not neces- sarily so extensive as that of their hosts, since environmental conditions tolerated by the latter may be unfavorable to the former. Protozoa with alternation of hosts (such as many of the Sporozoa) are further limited in distribution, since the definitive and intermediate hosts, both necessary for survival of the parasite, may not have the same range of adaptability to different habitats. While the host species living in geo- graphical isolation have been undergoing evolu- tionary divergence their parasites have likewise diverged to give rise to separate varieties and species. In view of these considerations, the parasitic Protozoa occurring in the Gulf of Mexico are less likely to be identical with species found in similar habitats elsewhere than are the free-living ones. To phrase the same idea in positive terms, one would expect, a priori, to find that many of the parasitic Protozoa in the Gulf of Mexico are new ones. The limited information we have about them, in fact, tends to support that con- clusion, since the overwhelming majority of them have been previously unrecorded species. The noteworthy exceptions were some of the ciliates observed by Powers (1935) in sea urchins; about half of them had previously been described at Bermuda and Beaufort, North Carolina. With one or two exceptions, as far as the writer knows, each of the parasitic species known in the Gulf of Mexico has been observed only in one or few GULF OF MEXICO 245 localities, and little attempt has been made to determine the extent of distribution. The excep- tions are Nematopsis ostrearum and Dermocy- stidium marinum (see footnote, p. 244), both para- sites of the oyster Crassostrea nrginica. Although much information accumulated by numerous in- vestigators relative to these two parasites re- mains unpublished, a comprehensive report by Landau and Galtsoff (1951) on the Distribution of Nematopsis has recently appeared. Since little can be said positively about the distribution of parasitic Protozoa in general, and those in the Gulf of Mexico in particular, this is a subject full of promise for future study. It would be of particular interest, from the economic point of view, to add to our meager information more data on the distribution of the protozoan parasites of such commercially important seafood animals as the shrimp, crabs, and oysters. Subphylum 1 PLASMODROMA Doflein 1901 Class 1 Mastigophora Diesing 1865 Subclass 1 Phytomastigina Doflein 1916 The Phytomastigina include those flagellates in which the plant characteristics are either pre- dominant or clearly marked. Of the six orders, two (Phytomonadina and Euglenoidina) are pre- dominantly freshwater forms commonly consid- ered to be Algae as well as Protozoa, one (Chloro- monadina) consists of rare and little known flagellates, another (Dinoflagellata) is so promi- nently represented in the Gulf that it is given separate treatment, and the other two (Cliryso- monadina and Cryptomonadina) are commonly represented in salt water, but the writer knows of practically no reports on them from the Gulf. The Phytomastigina are, therefore, given very little consideration here. Order 1 CHRYSOMONADINA Stein 1878 Although the Silicoflagellidae are exclusively marine plankton, and the Coccolithidae are mostly marine, the writer is not familiar with reports of members of this order from the Gulf of Mexico. Order 2 CRYPTOMONADINA Stein 1878 "The Cryptomonadina occur in fresh or sea water, living also often as symbionts in marine organisms." (Kudo, 1946, p. 213). Suborder 1 Eucryptomonadina Pascher 1913 Family CRYPTOMONADIDAE Stein 1. Chilomonas (?). This organism was observed by Pearse (1932) in a bracki.sh water pool (Pool 5) at Garden Key, Tortugas. Order 3 PHYTOMONADINA Blochmann 1895 These are mostly fresh water Algae. Order 4 EUGLENOIDINA Biitschli 1884 Members of this order are likewise mostly fresh water Algae. Order 5 CHLOROMONADINA Klebs 1892 "The chloromonads are of rare occurrence and consequently not well known." (Kudo, 1946, p. 243.) Order 6 DINOFLAGELLATA Butschli 1885 The dinoflagellates, which include many well- known planktonic forms in the Gulf, are treated separately (pp. 223-226). Subclass 2 Zoomastigina Doflein 1916 The majority of this subclass are either parasitic in land dwelling or fresh water animals or free living in fresh water. Order 1 RHIZOMASTIGINA Butschli 1883 Although some members of this group occur in salt water, the writer is not aware of reports of any of them from the Gulf of Mexico. Order 2 PROTOMONADINA Blochmann 1895 Organisms belonging definitely to this order seem not to have been reported from the Gulf. However, certain trypanosomelike organisms (now generally regarded as spirochaetes) very commonly occur in the intestinal tracts, especially in the crystalline styles, of various lamellibranch mollusks in many parts of the world. It is com- mon knowledge among oyster biologists that they occur in oysters of the Gulf, although no one seems to have recorded the fact. Those organisms are mentioned here for lack of a better place to con- sider them. Dimitroff (1926) made an intensive study of the spirochaetes of Baltimore market oysters. He gave a complete review of the litera- ture and listed 11 species or varieties which he found. He assigned 4 of the types to Saprospira Gross, 1910, and 7 to Cristispira Gross, 1910. Possibly the spirochaetes of Gulf coast oysters, 246 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE when identified, will be found to be similar to those studied by DimitrofF. Order 3 POLYMASTIGINA Blochmann 1895 Suborder 1 Monomonadena Kudo 1939 Family CHILOMASTIGIDAE Wenyon 1. Chilomaslix echinonim Powers, 1935. In intestinal ceca of the sea urchin, Tripneusles esculentus. Discovered by Powers (1935) in the vicinity of Bird Key, Tortugas. Class 2 Sarcodina Hertwig and Lesser 1874 Subclass 1 Rhizopoda von Siebold 1845 Order 1 PROTEOMYXA Lankester 1885 The wTiter is not familiar with reports of rep- resentatives of this group in the Gulf. Order 2 MYCETOZOA de Bary 1859 1. A mycetozoan. Hopkins (1931) made ob- servations on an unidentified mycetozoan at Tortugas. Order 3 AMOEBINA Ehrenberg 1830 The principal report on the amoebae of the Gulf which has come to the attention of the writer is Schaeffer's (1926) lengthy paper on taxonomy of the amoebae. He described a number of new species from Key West and Tortugas and pro- posed an extensive revision of the nomenclature of the free-living amoebae. As Hyman (1940) has pointed out, SchaefTer's terminology has not been generally accepted. Nevertheless, the no- menclature of this group has remained unsettled and has given rise to a considerable body of literature which was recently reviewed briefly by King and Jahn (1948). For the sake of conveni- ence, Schaeffer's terminology is followed here in listing the species he reported. This is not in- tended to imply that the writer holds any opinion concerning the taxonomy of the group. Family CHAIDAE Poche 1. Trichamoeba sphaerarum SchaefFar, 1926. Schaeffer (1926) observed this amoeba in towings and upon floating seaweed. He found it to be a common species in the vicinity of Tortugas. 2. Trichamoeba pallida Schaeffer, 1926. Schaeffer (1926) easily obtained this organism in Tor- tugas by letting a small stream of sea water filter through a small wad of cotton for a few days. 3. Melachaos fulvum Seha,efSeT, 1926. Found by Schaeffer (1926) in irrigated cultures in Tortugas. Family MAYORELLIDAE Schaeffer 4. Flabellula mira Schaeffer, 1926. According to Schaeffer (1926, p. 48), found in Key West, Tortugas, and Cold Spring Harbor, Long Island, among blue-green algae. Hopkins (1931) studied the life history of this amoeba at Tortugas. 5. Flabellula citata Schaeffer, 1926. Schaeffer (1926) saw this amoeba in salt water at Tor- tugas, at Cold Spring Harbor, and at Casco Bay, Maine. Hopkins (1931) studied, also, the life history of this amoeba at Tortugas. 6. Flabellula crassa Schaeffer, 1926. Discovered by Schaeffer (1926) in irrigated sea water cultures in the laboratory at Tortugas. 7. Flabellula pellucida Schaeffer, 1926. In describing this species Schaeffer (1926, p. 54) stated that this marine amoeba was found with blue-green algae from Key West harbor, Florida. His tabulation of species (p. 22) indicates that it was found at Tortugas. 8. Mayorella conipes Schaeffer, 1926. Found by Schaeffer (1926) at Tortugas and at Long Island Sound and Great South Bay, Long Island. 9. Mayorella gemmifera Schaeffer, 1926. According to Schaeffer's (1926) description (p. 50), this organism was observed both at Tortugas and Cold Spring Harbor. His tabulation (p. 22), however, indicates that it was found only at Tortugas where it was collected by running sea water through cotton. 10. Mayorella cryslallus Schaeffer, 1926. Discovered by Schaeffer (1926) in salt water aquaria in the laboratory at Tortugas. 11. Vexillifera aurea Schaeffer, 1926. Found by Schaeffer (1926) in salt water aquaria at the laboratory at Tortugas and also at Cold Spring Harbor. 12. Strio'atus tardus Schaeffer, 1926. Schaeffer (1926) stated (p. 26) that this amoeba was col- lected with blue-green algae in shallow water near a dock at Key West harbor. His table (p. 22) indicates that it was found at Tortugas. 13. Dactylosphaerium acuum Schaeffer, 1926. Found by Schaeffer (1926) among blue-green algae in very shallow water at Key West harbor and also in salt water aquaria in the laboratory at Tortugas. 14. Pontifex maxirnus Schaeffer, 1926. Schaeffer (1926) discovered this species in cultures from Casco Bay, Maine, and observed it, also (p. 22) in Tortugas. Family THECAMOEBIDAE Schaeffer 15. Rugipes vivax Schaeffer, 1926. Schaeffer (1926) collected this species at Tortugas and in tidal pools at Cold Spring Harbor. 16. Thecamoeba orbis Schaeffer, 1926. This amoeba was discovered by Schaeffer (1926) on floating seaweeds in the vicinity of Tortugas, and it was also seen at Cold Spring Harbor. GULF OF MEXICO 247 17. Thecamoeba munda Sehaeffer, 1926. Found by Sehaeffer (192G) among blue-green algae in Key We.xt harbor and in cultures of seaweeds from Tortugas. 18. Thecamoeba hitla Sehaeffer, 1920. Found by Sehaeffer (1920) in cultures in the laboratory at Tortugas and in Cold Spring Harbor. 19. Thecamoeba rugosa Sehaeffer, 1926. Found by Sehaeffer (1926) among blue-green algae at Key We.«t harbor, in a salt water tank in the laboratory at Tortugas, and at Cold Spring Harbor. Family HYALODISCIDAE Poche 20. Undo maris Sehaeffer, 1920. Sehaeffer (1926) discovered this amoeba in the salt water tank in the laboratory at Tortugas. 21. Gnbodiscus gemma Sehaeffer, 1926. Found by Sehaeffer (1926) in the salt water tank of the laboratory at Tortugas. 22. Flamella magnifica Sehaeffer, 1926. Sehaeffer (1926) discovered this amoeba among blue- green algae in cultures from Key West and Tortugas. 23. Cochliopodium gulosum Sehaeffer, 1926. In his description of the species Sehaeffer (1926) gave the localities (p. 106) as Cold Spring Harbor and Great South Bay, Long Island, where the organism was found on eelgrass and other seaweed. His table (p. 22) indicates that it was also observed at Tortugas. Order 4 TESTACEA Schultze 1854 Most of the Testacea are fresh-water forms. The writer knows of none reported from the Gulf of Mexico. Order 5 FORAMINIFERA D'Orbigny 1826 This large group, with many representatives in the Gulf of Me.xico, is treated separately. "* Subclass 2 Actinopoda Calkins 1909 Order 1 HELIOZOA Haeckel 1866 Most of these organisms are inhabitants of fresh water. The writer does not know of any which have been reported from the Gulf of Mexico. Order 2 RADIOLARIA J. Miiller 1858 The Radiolaria, a verj- large order, are exclu- sively marine and are widely distributed in the warmer waters of the seas. Although they may occur in the Gulf of Mexico, the wTiter is not familiar with studies on them there. Class 3 Sporozoa Leukart 1879 Our knowledge of the Sporozoa of the Gulf of Mexico is practically limited to the information which has growni out of investigations into ' See article by F. B. Phlegcr and F. L. Parker, pp. 235-241 of this book. causes of oyster mortality, especially those recently conducted by the Texas Agricultural and Me- chanical Research Founilation along the coasts of Louisiana, Texas, and Mississippi. Although the Sporozoa studied in investigations were pri- marily those parasitic in oysters, several were observed, also, in various decapod Crustacea, and very limited observations were made on forms in annelids. Sporozoa are common parasites in essentially all the major groups of animals, and the few studies on forms from the Gulf give promise that intensive search for members of this neglected group would reveal a great wealth of new and known species there. With one or two exceptions, which are considered below, nothing is known about the general distribution of most species. Subclass 1 Telosporidia Schaudinn 1900 Order 1 GREGARINIDA Lankester 1866 Suborder 1 Eugregarinaria Dofle in 1901 Tribe 1 Haplocyta Lankester 1885 Family MONOCYSTIDAE Stein 1. An "acephaline gregarine" Wichterman, 1942. Host: Pontodrilus bermudensis Beddard, a littoral oligochaete. Organs involved: Intestine and seminal vesicles. Locality: Observed at Loggerhead Key, Tortu- gas. Remarks: Wichterman's (1942) figures 18-20 suggest that this gregarine may be one of the Monocystidae. Hence, it is placed provisionally in this family. Tribe 2 Septata Lankester 1885 Family POROSPORIDAE Labb6 2. Nematopsis ostrearum Prytherch, 1938 (partim) .Sprague, 1949. Hosts: Molluscan host the oyster Crassostrea virginica (Gmelin) ; decapodan hosts the mud crabs Panopeus herbstii Milne Edwards, Eurypano- peus depressus (Smith) and Eurytium limosum (Say). Organs involved: The intestinal tract of the crab and almost all the organs (especially mantle) of the oyster. The gamontocj^sts attached to the rectum of the crab occur oiJy in the extreme posterior portion of the organ. Widely distributed along the Gulf and Atlantic coasts. Landau ami Galtsoflf (1951) found Nema- 248 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE topsis spores, probably this species, in Delaware Bay and as far north as Great South Bay, New- York. The northern limit of the known range is based on Prytherch's (1938, 1940) observation of Nematopsis spores in oysters as far north as Mobjack Bay, Virginia.' Although N. ostrearum, as originally described, contained two species, it is believed that only the one considered at this time extends as far north as Virginia. (See A'^. prytherchi below.) 3. Nematopsis prytherchi Sprague, 1949. Hosts: Molluscan host the oyster Crassostrea virginica (Gmelin) , decapodan host the stone crab Menippe mercenaria (Say). Organs involved: The intestinal tract of the crab and the gills (principally) of the oyster. The gamontocysts are distributed along the entire rectum of the crab. Distribution: Widely distributed along the Gulf coast and probably to North Carolina on the Atlantic coast. North Carolina is presumed to be the northern limit of the range of this species since its only known decapodan host, according to Rathbun (1930), occurs only that far north. Remarks: This species was separated from Nematopsis ostrearum Prytherch, 1938, in a pre- liminary note by Sprague in 1949 and described in detail later (1950), with an account of extensive infection experiments, in an unpublished report submitted to Texas Agricultural and Mechanical Research Foundation. 4. Nematopsis penaeus n. sp.= Nematopsis (?) sp. Sprague, 1950. Hosts: Penaeus aztecus Ives, one of the common commercial shrimp, is here designated as the host, although the parasite seems to be identical with one in P. setiferus (Linn.). No intermediate host is known. The oyster, Crassostrea virginica (Gmelin), has been eliminated, by means of infection experiments, as a possible host. Organs involved: Intestinal tract of the decapod. Vegetative stages: Similar to those of weU- known species of Nematopsis. Early stages are small spherical bodies intracellular in the intestinal epithelium. Epimerite spherical. Young greg- arines early become associated in chains of two or more individuals in linear or bifurcated syzygy. ' Reported also from Delaware Bay and Great .South Bay. New York, by n. Landau and P. S. Galtsofl (1951, Texas Jour. Sci., vol. 3). The posterior extremity in older associations often appears somewhat more truncate than in the described species of Nematopsis. Gamontocysts: Spherical; 132-260 microns in diameter, the mean diameter being 177 microns (based on measurements of 35 cysts from 2 host specimens) ; attached to the chitinous lining of the rectum and distributed along its entire length. Note: "Gamontocyst" is used here in accordance with the new terminology recently proposed by Fihpponi (1949). Gymnospores: Smooth, spherical aggregates of cells when mature. They are among the largest known, being comparable in size with only those of A'^. prytherchi. (Unfortunately, measurements on living gymnospores are not on hand, and measurements of stained ones are of little value for comparing with living gymnospores of other species.) Distribution: Barataria Bay, Louisiana, is here designated as the type locality. The organism, however, is probably widely distributed along the Gulf and Atlantic coasts, since it has been found in every one of hundreds of slirimp examined from the Louisiana coast when the examination was made soon after the shrimp were collected. Comparison and affinities: The vegetative stages are similar to those of known species of Nematopsis. Gynuiospores are very large, only those of N. prytherchi being comparable in size. Gamonto- cysts are about the same size as those of A^. maraisi (Leger and Duboscq, 1911) in the crab Portunus depurator and are exceeded in size only by those of Porospora gigantea (Van Beneden 1869) ; in being distributed along the entire rectum of the host they are like P. gigantea in the European lobster and different from any known species of Nematopsis excepting A^. pyrtherchi in the stone crab. To summarize, A^. penaeus resembles A''. maraisi in size of gamontocyst but is distinctly different in having a larger gymnospore; it re- sembles A^^. prytherchi in size of gymnospore and distribution of gamontocyst but has a larger gamontocyst and different host specificity; it resembles Porospora gigantea also in distribution of the gamontocysts in the rectum of the host and by being an inhabitant of one of the macroura but has a distinctly larger gymnospore and is strikingly different in the vegetative stages. The writer's attention was first called to this gregarine, the third member of the Porosporidae GULF OF MEXICO 249 described from American waters, by Prytlierch (personal communication, 1946). Although the known stages of the parasite are indistinguishable from corresponding stages of Nematopsis (some of them tlifferent from corresponding stages of Porospora, the only other genus which it resem- bles), it cannot be assigned to Nematopsis with confidence until its life history is completely known. Since it has gynniosporcs it can be placed in Porosporidae (members of which are unique among grcgarines in having gymnospores and alternation of hosts), but there is not the slightest clue as to what the intermediate host (if anj-) may be. Since generic characters of the two genera now in the family are based upon stages in the intermediate host, definite generic determi- nation caimot now be made. Sprague (1950) concluded, primarily on the basis of infection experiments, that the oyster is not the intermediate host of this gregarine. If Nematopsis penaeus has an intermediate host one would expect the latter to be an organism (possibly a small mollusk or a worm) which constitutes the chief or a very prominent item in the diet of shrimp. The last statement is based upon the belief that the host must acquire a new infestation almost every day in order to maintain, at all times, a large gregarine population consisting of individ- uals representing essentially eveiy stage of devel- opment. The problem of discovering the possible intermediate host is complicated by the remarkable fact that, as Burkenroad has pointed out in a personal communication, we are almost completely ignorant of the feeding habits of the very familiar decapodan host. The possibility that the shrimp become directly reinfested by ingesting the gymno- spores which pass from their intestines requires further consideration, although experimental data by Sprague (1950) suggest that such studies would give negative results. Slii-imp maintained in the laboratory and fed upon oysters (containing Nema- topsis spores) and fish became entirely free of gregarines in less than a week. The tentative conclusion from those data is that the shrimp neither reinfest themselves nor become infested by eating oysters (although Nematopsis spores from oysters readily germinate in slirimp), but that they acquire the gregarines by feeding almost daily upon some specific but unknown organism common in their natural habitat. Since these gregarines are intracellular in the intestinal epithelium of the host during their early development, and since the host seems to acquire great numbers of tliem almost daily, the intestinal epithelium is sul)ject to appreciable damage by the parasites. In view of the great economic importance of shrimp, the host-parasite relation of these two organisms is of more than academic interest and deserves intensive investigation. 5. "Gregarine cysts" were reported by Pearse (1932a) in the calico crab, Eriphia gonagra (Fabricus) in Tortugas. Although Pearse (1932a) merely mentioned gregarine cysts seen on the walls of the rectum of the crab, it is quite probable that they were Nematopsis. Not only are Nematopsis cysts at- tached to the rectum in many species of crabs very common, but A^^. legeri (de Beauchamp, 1910), one of the best known species, occiu-s in a species of Eriphia, E. spinijrons Herbst, on the coast of France. UNIDENTIFIED SPECIES OF NEMATOPSIS As in Europe, several species of moUusks in American waters have been found to harbor Nematopsis spores of undetermined species. Al- though some of those spores may represent stages of well-laiown species of Nematopsis, it is quite probable that others represent undescribed species. A list of those mollusks is given in the table below. Table 1. — American mollusks in which spores of undeter- mined species of Nematopsis have been observed Host species Organs in- volved Locality Author From Gulf of Mexico: Ostrea cristata.. Modiolus demissua.. Mytilus recurvus Ensia minor.. From southern waters, possibly including the Gulf of Mexico; Pecten gibossus Anomia simplex Ostrea equesiris ' Modiolus demissus.. Venus ziczac Marte.tia cuneiform- is Urosalpinx cinerea.. From Pacific Coast: (?) Mantle and gill. (?)... Port Aransas. Tex. Grand Lsle, La.. Barataria Bay. La. do (?) 8. H. Hopkins (unpublished). Sprague (un- published). Do. Mantle -. (?) Do. Prytherch (7) (?) (1940). Do. (7)-- (?) (?) Do. (?) Do. (?) (?) Do (?) (?) Do. (?) (?) Do. (7) Gulf of Panama. Landau and GaltsoB, 1951. • Hopkins, S. H., has called attention to the fact that this should bo 0. cristata since O. equesiris occurs not in North America but in South America. Unidentified gregarines were foimd in Barataria Bay, Louisiana, by Hopkins (personal communi- 250 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE cation, 1950) in a common tube-dwelling annelid, Spirochaetoptems sp., and in the intestines of Polydora wehsUri (Hartman), a common poly- chaete infesting the shells of oysters. Order 2 COCCIDIA Leuckart 1879 The writer knows of no members of tliis order which have been reported from the Gulf of Mexico. It is possible, however, that they may be present in some of the numerous species of vertebrates there. Order 3 HAEMOSPORIDIA Danilewsky 1886 Excepting Plasmodium, which occurs in the vicinity of the Gulf but which does not seem to fall within the scope of this paper, the author knows of no Haemosporidia reported from the area. Subclass 2 Acnidosporidia Cepede 1911 Order 1 SARCOSPORIDIA Balbiani 1882 The Sarcosporidia, being chiefly parasitic m the muscle tissues of mammals, seem not to have been reported from the Gulf. Order 2 HAPLOSPORIDIA Gaullery and Mesnil 1899 It is customary to place in this order any organism which seems to have sporozoan affinities but does not belong to any other order. Conse- quently, Haplosporidia includes a heterogeneous assemblage of unrelated organisms. Some of them should probably be assigned to new orders, and some others may be more closely related to fungi than to Sporozoa. The one common char- acteristic is the lack of polar filaments in the spores. Although there are many types of spores represented in this order, some of them have a striking superficial resemblance to those of Micro- sporidia. Only one species (previously unre- corded) which can unquestionably be properly assigned to Haplosporidia seems to be known from the Gidf. Two others are provisionally included here pending further information. 1. Haplosporidium sp. Observed by Sprague in January 1948 in the vicinity of Grand Isle, Louisiana, in only one of many specimens of the common mud crab, Panopeus herbstii Milne Edwards (kindly identified by F. A. Chace, Jr., of the United States National Museum). The intestine, covered on the outside with the spores, has a conspicuous dark brown appearance. 2. "A haplosporidian (microsporidian?)". In Gymnophallas .sp. (metacercariae). A trematode parasite of the clam Donax sp. from Port Aransas, Te.xas, was reported by Hopkins (1950) in a personal communication to the author. 3. DermocijMidium marinum Mackin, Owen and Collier, 1950. Found to be widely distributed in Crassostrea virginica (Gmelin), the commercial oyster, along the Gulf coast. It infects any of the host tissues, especially the intestinal epithelium, adductor muscle, gills, mantle, and heart. Although there is great uncertainty about the taxonomic position of the genus Dermocystidiuni, it is usually placed in the Haplosporidia (see footnote, p. 244). According to Mackin et al. (1950), the parasite has been found asso- ciated "with dead or dying oysters under certain environ- mental conditions, the limits of which can be reasonably well-defined. The chief controlling factors appear to be temperature and salinity, low temperature and low salinity evidently retarding the development of the infestation" (p. 329). Subclass 2 Cnidosporidia Doflein 1901 Order 1 MYXOSPORIDIA Butschli 1881 The writer knows of no Myxosporidia which have been reported from the Gulf of Mexico, although there is no reason to doubt that they occur there. As Kudo (1946) has pointed out, these organisms are exclusively parasites of lower vertebrates, especially fish. Davis (1917) and others have described numerous species found in various fish of the Atlantic coast. The fact that many of the same species of fish occur also in the Gulf of Mexico is reason to suspect that many of the known Myxosporidia also occur there. Doubtless, a search for these neglected forms would be rewarded by the discovery of many new and known species. Order 2 ACTINOMYXIDIA Stolg 1899 This order contains but few known species, all occurring in fresh or salt-water annelids, and none apparently having been reported from the Gulf. In view of the great variety and numbers of annelids in the Gulf, however, it is quite possible that species of Actinomyxidia occur there. Order 3 MICROSPORIDIA Balbiani 1883 The Microsporidia, being typically parasites of artliropods and fish (although they are repre- sented in several animal phyla), are probably common parasites in animals of the Gulf. The GULF OF MEXICO 251 Crustacea, in particular, arc very susceptible hosts and are abunilantly represented in the Gulf. Nevertheless, Microsporidia occurring in the Gulf, even in economically very important animals, seem to have been almost completely neglected. The writer knows of only three species which have been definitely identified as Microsporidia, al- though others have probably been observed in the Gulf. Family NOSEMATIDAE Labb§ 1. Nosema nelsoni Sprague, 1950. In the muscles of Penaeus aztecus Ives, one of the common commercial shrimp, was reported from Barataria Bay, Louisiana, but apparently is widely distributed along the Gulf and Atlantic coasts. Burkenroad (personal communication) believes that he has seen the parasite also in P. setiferus (Linn.). It is remarkable that this very common parasite which causes a conspicuous discoloration of the host and an appreciable economic loss to the shrimp industry seems never to have been the subject of serious investigation. 2. Thelohania penaei Sprague, 1950. In se.x organs of Penaeus setiferus (Linn.), a common commercial shrimp, was reported from the vicinity of Grand Isle, Louisiana, but probably is widely distributed. After Sprague (1950a) described the polar filament of this parasite as being unique in its structure he learned that Jirovec (1937) described a very similar polar filament in a new species of Plistophora, P. schafernai, which he found in Daphnia pulex. The author is pleased to take this opportunity to correct his error. Burkenroad (personal communication) thinks he has seen this parasite also in Penaeus aztecus Ives. Since species of Thelohania in the sex organs of certain other decapods allegedly cause parasitic castration, the possible role of T. penaei m the fluctuation of shrimp populations is a matter of considerable economic interest and should be thoroughly investigated. In this connection, Viosca (1943) has made some interesting observa- tions. He stated (p. 276), "Some years ago (1919) about 90 percent of the salt water shrimp, Penaeus setiferus, existing in the waters along the Louisiana coast were infected with a protozoan disease which destroyed their reproductive organs. Yet during the following two years, 1920 and 1921, the shrimp crops were the largest then known and were greater than for several succeeding years. Thus, 10 percent of the adult shrimp population produced a larger succeeding crop than 10 times their number did the preceding year, while the large 1921 crop again produced a smaller number. This evidence shows that with a prolific species, the food supply and other ecological factors are far more important than the actual number of eggs laid." 3. Thelohania sp. Sprague, 1950. In all the muscles of Petrolisthes armatwi (Gibbes), a small flat crab very common on oyster reefs. Known only from a particular shell reef near Grand Terre Island in Barataria Bay, Louisiana. Pending further information on the affinities of this parasite, it was not named at the time it was reported. It is now definitely believed to be dis- tinct from previously recorded species. Order 4 HELICOSPORIDIA Kudo 1931 This order contains only one species, and there is no reason to suspect that any occiu-s in the Gulf of Mexico. Subphylum 2 CILIOPHORA Doflein 1901 Class 1 CiLIATA Perty 1852 Subclass 1 Protociliata Metcalf 1918 Most of the Protociliata inhabit the colon of Salientia, rarely marine fish or other vertebrates. Probably none has been observed in vertebrates of the Gulf of Mexico. Subclass 2 Euciliata Metcalf 1918 Although more than half of the ciliates re- ported from the Gulf of Mexico have been new species, there is no doubt that numerous pre- viously known ones are represented there. Since the free-living ciliates are essentially cosmopolitan, it is not surprising when one finds a particular form in any locality where there is a favorable habitat. BuUington (1940), and undoubtedly many other persons as well, saw many ciliates which he did not have an opportunity to identify. 252 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Order 1 HOLOTRICHA Stein 1859 Suborder 1 Astomata Schwiakoif 1896 Family ANOPLOPHRYIDAE C^pede 1. Anoptophrya macronucleata Wichterman, 1942. In the intestine of PontodrUus bermudensis Beddard, a littoral oligochaete. Discovered by Wichterman (1942) in the vicinity of Loggerhead Key, Tortugas. 2. "A ciliate resembling Rhizocaryum." Was found by S. H. Hopkins (personal communication, 1950) in the intestines of Polydora websteri (Hartman). Very common in Barataria Bay, Louisiana. Family INTOSHELLINIDAE Cepede 3. Maupasella leplas Wichterman, 1942. In the intestine of PontodrUus bermudensis Beddard, a littoral oligochaete. Discovered by Wichterman (1942) in the vicinity of Loggerhead Key, Tortugas. Suborder 2 Gymnostomata Biitschli 1889 Tribe 1 Prostomata Scliewiaicoff Family SPATHIDIIDAE Kalil 4. Paraspathidium trichostomum Noland, 1937 Noland (1937) found a few individuals of this species near Englewood, Florida, and created a new genus to contain the .species. Family DIDINIIDAE Poche 5. Mesodinium pulei (Claparfede and Lachnian, 1858). Noland (1937) found this species frequently in marine cultures at Ba.ss Biological Laboratory, Englewood, Florida. 6. Mesodinium acarus Stein, 1862. Observed in cultures at Bass Biological Laboratory, Engleivood, Florida, by Noland (1937) who stated that he was familiar with the .same species in fresh water. Family COLEPIDAE Clapargde and Lachmann 7. Coleps spiralis Noland, 1937. Noland (1937) discovered this ciliate at Bass Biological Laboratory, Englewood, Florida. 8. Coleps tesselatus Kahl, 1930. Noland (1937) observed this ciliate in the vicinity of Englewood, Florida. 9. Coleps heteracanthus Noland, 1937. Discovered by Noland (1937) in the vicinity of Engle- wood, Florida. 10. Coleps pulcher Kahl. Observed by Noland (1937) in a salt spring near Engle- wood, Florida. 11. Coleps up. Bullington, 1931. Bullington (1931) observed two undetermined species of Coleps at Tortugas. Family HOLOPHRYIDAE Schouteden 12. Plagiocampa marina Kahl. Reported by Noland (1937) from the vicinity of Engle- wood, Florida. 13. Placus socialis (Fabre-Domergue, 1889). Reported by Noland (1937) from the vicinity of Engle- wood, Florida. 14. Trachelocera dracontoides Bullington, 1940. Discovered by Bullington (1940) in 1930, exact locality unrecorded, and in 1939 in cultures from moat at Fort Jefferson, Garden Key, Tortugas. 15. Trachelocera subviridis Sauerbrey,' 1928. Observed by Noland (1937) in a salt spring near Engle- wood, Florida. 16. Trachelocera sp. Observed by Pearse (1932) in Pond 1 on Long Key, Tortugas. Tribe 2 Pleurostomata SchewiakofT Family AMPHILEPTIDAE Schouteden 17. Kentrophorus fasciolatum SnueTbrey, 1928. Noland (1937) observed this ciliate in sediment over a sandy bottom in sea water near Englewood, Florida. Tribe 3 Hypostomata Scliewiakoff Family NASSULIDAE Scliouteden 18. Nassula gigantea Bullington, 1940. Found by Bullington (1940) several times on algae in the bottom of the moat on the south side of Fort Jefferson, Garden Key, Tortugas. 19. Paranassida microstoma (Claparfede and Lachmann, 1858). Noland (1937, p. 166) found several specimens in "a shallow marine estuary just inside the beach ridge from the Gulf of Mexico, and connected indirectly through a pass with the Gulf." Suborder 3 Trichostomata Biitschli 1889 Family ENTORHIPIDIIDAE Madsen 20. Enlodiscus sabulonis Powers, 1935. Found by Powers (1935) in the intestines of sea urchins, Clypeaster rosaceus and C. subdepressns, in shallow water at Tortugas. 21. "Form L" Powers, 1935. Powers (1935) considered this unidentified ciliate infest- ing Clypeaster subdepressus in Tortugas to be either a variety of E. sabulonis or a closely related species. 22. Biggaria bermudensis (Biggar, 1932). According to Powers (1933, p. 279), "While this species may be found in any echinoid host, it seems to prefer Lytechinus variegatus or Tripneusles esculentus," infesting their intestines. The species is considered by Powers (1933, 1935) as identical with form "D" which Jacobs (1911) discovered at Tortugas and indicated that it has been observed also at Bermuda and Beaufort, North Carolina. 23. Anophrys elongata Biggar, 1932. According to Powers (1935) this ciliate is identical with form "C" of Jacobs (1911). It was found at Bermuda and Tortugas in all the species of sea urchins e.xamined. Biggar GULF OF MEXICO 253 fl932) found it in Lylechinus variegaliis and Erhinometrus lacunter. 24. Anophrys aglycus Powers, 1935. Powers (1935) found this ciliate present in the intestines of all species of sea urchins living near the tide line in Tortugas though not abundant in any of them. Trip- neustes exculentun collected near the reef was the best e.xample of infestation with this form. 25. "Form M" Powers, 1935. In the intestines of the sea urchins Trypneustes e.inilenius and Lytechiniis variegaliis in Tortugas. Powers (1935) noted that this form was similar both to Cohnilembus caeci Powers, 1935 (see below), and Anophrys vermiformis Powers, 1933, the latter common to Lylechinus variegatus at Beaufort, North Carolina. It is listed provisionally here with the Entorhipidiidae simply for the sake of con- venience; there is no implication that the writer holds an opinion as to its ta.xonomic position. Suborder 4 Hymenostomata Hickson 1903 Family FRONTONIIDAE Kahl 26. Frontonia schaefferi Bullington, 1939. Discovered by Bullington (1939a, 1940) in a pool at East Key, Tortugas. 27. Frontonia ocularis Bullington, 1939. In Tortugas. 28. Uronema marina Dujardin. Observed by Pearse (1932) in Pool 5 on Garden Key, Tortugas. 29. Uronema pleuricaudatum Noland, 1937. Discovered by Noland (1937) in cultures at Bass Biological Laboratory, Englewood, Florida. Family OPHRYOGLENIDAE Kent 30. Ophryogtena frontonia Bullington, 1940. Found by Bullington (1930) in a pool on East Key and later (1939) in cultures from the moat around Fort Jefferson on Garden Key, Tortugas. 31. Pteuronema setigerum Calkins, 1902. Originally discovered at Woods Hole, Massachusetts, this species was found by Noland (1937) in the vicinity of Englewood, Florida. 32. Pteuronema coronatum Kent. Observed by Noland (1937) in the vicinity of Engle- wood, Florida. 33. Pteuronema marinum Dujardin, 1841. Observed by Noland (1937) in the vicinity of Engle- wood, Florida. 34. Cyclidium rhabdotectum Powers, 1935. In Tortugas found in the sea urchins Centrechinus antiltarum, Echinometra tucunter, Tripneustes esculentus and Ctypeaster rosaceus, being rare in the last host species. Powers (1935) considered it quite likely that this species is the one which Jacobs (1912) designated as form "A." 35. Histobalantidium semisetatnm Noland, 1937. Discovered by Noland (1937) in the vicinity of Engle- wood, Florida. Family COHNILEMBIDAE Kahl 36. Cohnitembus caeci Powers, 1935. Powers (1935) who discovered the species at Tortugas remarked that C. caeci, commonly found in any of the littoral echinoids, has a marked predilection for Trip- neustes esculentus. Suborder 5 Thigmotricha Chatton and Lwoff 1926 Family HYSTEROCINETIDAE Diesing 37. Hyslerocinela pontodrilus Wichterman, 1942. In intestines of Pontodrilus bermudensis Beddard, a littoral oligochaete in the vicitiity of Loggerhead Key, Tortugas (Wichterman 1942). Order 2 SPIROTRICHA Biitschli 1889 Suborder 1 Heterotricha Stein 1859 Family METOPIDAE Kahl 1. Metopus brevicristatus Powers, 1935. Limited to the intestines of the sea urchin Clypeaster rosaceus in Tortugas. This ciliate seems to be the one designated by Powers (1933) in a preliminary note as form "G." 2. Metopus histophagus Powers, 1935. Observed only in intestines of the sea urchin, Clypeaster subdepressus, in Tortugas. 3. Metopus rotundus Lucas, 1934. Known only from the intestines of the sea urchin, Centrechinus antillarum. Originally described from Ber- muda, this ciliate was reported from Tortugas by Powers (1935). According to Powers (1935, p. 302), "Lucas (1934) re- ports this form as the sole infestant of three specimens of Centrechinus antillarum from Bermuda. At Tortugas, M. rotundas was always found in company with other ciliates." In a preliminary note by Powers (1933) this ciliate ap- parently was designated as form "J." 4. Metopus circumlabens Biggar, 1932. This species has been found in the intestines of various sea urchins in Bermuda and Tortugas. Observed in Cen- trechinus antillarum and Echinometra tucunter by Jacobs (1912), Biggar (1932), Lucas (1934), and Powers (1935); in Lytechinus variegatus by both Jacobs and Powers; in Tripneustes esculentus by Powers (1935); rarely in Cly- peaster rosaceus and C. siibdeprcssus by Powers. Family SPIROSTOMIDAE Kent 5. Gruberia lanceolatum (Gruber 1884). This free-living ciliate is widely distributed, having been observed by Bullington (1940) not only at Tortugas but also at Cold Spring Harbor, Long Island, and Beaufort, North Carolina. 254 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 6. "A form related to Gruberia calkinsi" was observed by Anigstein (personal communication 1950) on the northeast shore of Galveston Island in Galveston Channel, Texas. Family CONDYLOSTOMIDAE Kahl 7. Condylosloma granulostim Bullington, 1940. Bullington (1940) found this ciliate in pools on Bush Key, Tortugas, and in brackish water ponds at Cold Spring Harbor. 8. Condylosloma mintituin Bullington, 1940. Discovered by Bullington (1940) at Tortugas, exact locality unrecorded. 9. Condylosloma magnum Spiegel, 1926. Observed by Bullington (1940) in pools on Bush Key Reef, Tortugas, at extreme low tide. 10. Unidentified species of Condylosloma. This species was observed by Pearse (1932) in Pond 1 on Long Key, Tortugas. Family STENTORIDAE Carus 11. Stentor auriculaUts Kahl, 1932. Found by Bullington (1940) in old cultures in the labora- tory at Tortugas. 12. Unidentified species of Slentor. Observed by Pearse (1932) in Pond 1 on Long Key, Tortugas. Family FOLLICULINIDAE Dons 13. A ciliate resembling Folliculina moebiusi Kahl. This specimen was called to the attention of the writer in the summer of 1938 by J. H. Roberts of Louisiana State University. The organism was in a sample of sediment from the bottom of Barataria Bay, Louisiana. Family PERITROMIDAE Stein 14. Peritromus iortugensis Bullington, 1940. Discovered by Bullington (1940, p. 195) "in algal cultures from near the tip of Long Key at very low tide," Tortugas. Suborder 2 Oligotricha Biitschli 1887 Family HALTERIIDAE Claparede and Lachmann 15. Halleria. Pearse (1932) observed an unidentified species in Pond 1 on Long Key, Tortugas. 16. Slrombidiiim alveolare Bullington, 1940. Discovered by Bullington (1940) in floating material at the dock at Fort Jefferson, Garden Key, Tortugas. Suborder 4 Hypotricha Stein 1859 Family OXYTRICHIDAE Kent 17. Oxylricha. Bullington (1935) mentioned having observed Oxylricha at Tortugas. 18. Holosticha rubra (Ehrenberg 1838). Found by Bullington (1940) at various localities at Tortugas and at Beaufort, North Carolina. 19. Epidinles caudatus Bullington, 1940. Discovered by Bullington (1940), exact locality un- recorded, at Tortugas. 20. Slylonychia sp. .\nigstein, 1950. Anigstein (personal communication 1950) ob.served an unidentified species of Slylonychia on the northeast shore of Galveston Island in Galveston Channel, Texas. 21. Stylonichia. Pearse (1932) observed an unidentified species of Slylonychia in Pond 2 on Long Key, Tortugas. 22. Strongylidium. Pearse (1932) observed an unidentified species of Slrongylidium in Pond 2 on Long Key, Tortugas. 23. Uncinala giganlea Bullington, 1940. Bullington (1940) discovered this ciliate, for which he created a new genus, at Tortugas. He believed it came from Long Key but was not certain. Although Bullington did not assign the new genus to a family, it apparently belongs to the Oxytrichidae. 24. Unidentified sp. Anigstein (1949) made physiological studies on an undetermined member of the Oxytrichidae collected along the northeast shore of Galveston Island, Texas. Family EUPLOTIDAE Glaus 25. Euploles charon (Miiller). Observed by Anigstein (personal communication 1950) along the northeast shore of Galveston Island in Galveston Channel, Texas. 26. Euplotidium agilalum Noland, 1937. Discovered by Noland (1937) in two samples from Lemon Bay near Bass Biological Laboratory and (p. 170) "in squeezings from half-dead sponges brought up by sponge fishermen from about 25 feet of water 10 miles out in the Gulf of Mexico off Tarpon Springs, Florida." Noland created a new genus to contain the species. 27. Uronychia hcinrolhi Buddenbrock, 1920. Observed by Bullington (1940) in various localities at Tortugas. Family PARAEUPLOTIDAE Wichterman 28. Paraeuploles Iortugensis Wichterman, 1942. Wichterman (1940, 1942) found this ciliate, for which he created a new family and a new genus, in abundance on the coral, Eunicea crassa, at Tortugas. FAMILY UNKNOWN 29. Unidentified sp. Pearse (1932) observed unidentified hypotrichous infusorians in Pond 1 on Long Key and Pool 5 on Garden Key, Tortugas. 30. Gaslrocirrhus slentoreus Bullington, 1940. Discovered by Bullington from an unrecorded locality believed to have been Long Key, Tortugas. Bullington (1940) stated that this species is similar to G. intermedius Lepsi, 1928, for which the genus was GULF OF MEXICO 255 creatod, in having characters of botli hotcrotrichs and hypotrichs. Ho further stated that Kahl (li)3r)) was unable to classify Lepsi's species. Order 3 CHONOTRICHA Wallengren 1895 The writer does not know of any member of tills order which has been reported from the Gulf of Mexico. Order 4 PERITRICHA Stein 1859 Suborder 1 Sessalia Kahl 1935 Tribe 1 Aloricata Kahl Family EPISTYLIDAE Kent 1. Epistylis. Pearse (1932a) found undetermined sjjecies of Epistylis on the gills of the following crabs at Tortugas: Coenobita ctypeastus (Herbst) from Garden Key and Long Key, Geograpsus lividus (Milne Edwards) from Bird Key Reef, and Pachy/irapsus transversus (Gibljes) from Long Key. He also found Epistylis on the abdominal appendages of the isopod, Ligyda exotica (Roux) from the walls of the moat at Fort Jefferson on Garden Key. Family VORTICELLIDAE Fromental 2. Vorticella marina GreeflF, 1870. Observed by Pearse (1932) in Pond 2 on Long Key, Tortugas. Noland and Finley (1931, p. 97) held the opinion that "V. marina Greeff, 1870, is possibly identical with V. nebulifera O. F. M., which was originally described from salt water. Further study of the marine Vorticel'ae is necessary before synonymy of the marine species can be definitely settled." Class SucTORiA Claparede and Lach- mann 1858 Although it is probable that members of this group are common in the Gulf of Mexico, the writer is not familiar with reports of their occurrence there. LITERATURE CITED Anigstein, R. 1949. Acclimatization of a marine free-living ciliate (Oxytrichidae) to lower osmotic pressure. Texas Jour. Sci. 1 (3): 71-76. Beauchamp, p. de 1910. Sur une GrSgarine nouvelle du genere Porospora. C. R. Acad. Sci. 151: 997-999. Beneden, E. Van 1869. Sur une nouvelle espfece de Gr^garina d6sign6e sous le nom de Gregarina gigantea. Bull. Ac. Roy. Belg., ser. 2, 28: 444-456. Bigg A R, R. B. 1932. Studies on ciliates from Bermuda sea urchins. Jour. Parasitol. 18: 252-257. (Cited from Powers, 1935.) Bui.I.I.NGTON, W. E. 1931, Variation in the distribution of ciliates at Tortu- gas 1930-1931. Yearbook Carnegie Inst. Washington 30: 378-379. 1935. Morphology and taxonomy of Ciliata. Yearbook Carnegie Inst. Washington 34: 77-78. 1939. A preliminary report on some ciliates of the Tortugas region. Yearbook Carnegie Inst. Wash- ington 38, p. 221. 1939a. A study of spiraling in the ciliate Frontonia, with a review of the genus and a description of two new species, .\rchiv f. Protistenk. 92 (1): 9-66. (Cited from Zoological Record.) 1940. Some ciliates from Tortugas. Papers Tortugas Lab. Carnegie Inst. Washington 32: 179-221. Calkins, G. N. 1933. Biology of the Protozoa. Philadelphia. Davis, H. S. 1917. The Myxosporidia of the Beaufort region, a systematic and biologic study. Bull. Bur. Fisheries 35: 201-243. DiMITBOFF, V. T. 1926. Spirochaetes in Baltimore market oysters. Jour. Bact. 12: 135-177. Fii.iproNi, A. 1949. Gregarine policistidee parassite di Laemostenus algerinus con considerazioni sulla nomenclatura nelle gregarine. Revista di Parassitologia 10 (4) : 245-263. HoPKi.Ns, D. L. 1931. Study of the life-histories of two marine amoebae and a mycetozoan. Yearbook Carnegie Inst. Wash- ington 30: 383-384. Hyman, L. H. 1940. The invertebrates: Protozoa through Ctenophora. McGraw-Hill Book Co., New York. Jacobs, M. H. 1912. Physiological studies on the protozoan parasites of Diadema setosum. Yearbook Carnegie Inst. Washington 10: 131-133. JfROVEC, O. 1937. Zur Kenntiiis einiger Cladocercnparasiten. I. Zool. Anz. 118 (11/12): 307-314. King, R. L., and Jahn, T. L. 1948. Concerning the genera of amoebas. Science 107: 293-294. Kudo, R. R. 1940. Protozoology. Springfield. Landau, H., and Galtsoff, P. S. 1951. Distribution of Nematopsis infection on the oyster grounds of the Chesapeake Bay and in other waters of the Atlantic and Gulf States. Texas Jour. Sci. 3 (1): 115-130. 256 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Leger, L., and Duboscq, 0. 1911. Deux nouvelles espfeces de grSgarines appartenant au genere Porospora. Ann. Univ. Grenoble 23: 401-404. Lucas, M. S. 1934. Ciliates from Bermuda sea urchins. I. Metopus. Jour. Roy. Micros. Soc. 44: 79-93. (Cited from Powers, 1935.) Mackin, J. G.; Owen, H. M.; and Collier, A. 1950. Preliminary note on the occurrence of a new protistan parasite, Dermocysiidium marinum n. sp., in Crassostrea virginica (Gmelin). Science 111: 328-329. NOLAND, L. E. 1937. Observations on marine ciliates of the gulf coast of Florida. Trans. Am. Micros. Soc. 56 (2): 160-171. -, and FiNLET, H. E. 1931. Studies on the taxonomy of the genus Vorticelta. Trans. Am. Micros. Soc. 50 (2): 81-123. Pearsb, a. S. 1932. Animals in brackish water ponds and pools at Dry Tortugas. Papers Tortugas Lab. Carnegie Inst. Washington 28: 125-141. 1932a. Observations on the parasites and commensals found associated with crustaceans and fishes at Dry Tortugas. Papers Tortugas Lab. Carnegie Inst. Wash. 28: 103-115. 1949. Zoological names, a list of phyla, classes and orders. 4th Ed. Durham, N. C. Powers, P. B. A. 1933. Studies on the ciliates from Tortugas echinoids. Yearbook Carnegie Inst. Washington 32: 278-280. 1935. Studies on the ciliates of sea urchins, a general survey of the infestations occurring in Tortugas echinoids. Papers Tortugas Lab. Carnegie Inst. Washington 29: 293-326. Prytherch, H. F. 1938. Life-cycle of a sporozoan parasite of the oyster. Science 88: 451-452. 1940. The life cycle and morphology of Nematopsis ostrenrum, sp. nov., a gregarine parasite of the mud crab and oyster. Jour. Morph. 66 (1): 39-65. Rathbun, M. J. 1930. The cancroid crabs of America. U. S. Nat. Mus. Bull. 152: 1-609. Schaeffer, a. a. 1926. Taxonomy of the amebas with descriptions of thirty-nine new marine and freshwater species. Carnegie Inst. Washington Pub. 345: 1-116. Sprague, V. 1949. Species of Nematopsis in Oslrea virginica. Jour. Parasit. 35 (6-2), page 42. 1950. Studies on Nematopsis prytherchi Sprague and N. ostrearum, emended. Mimeographed for private distribution by Texas A and M Re.search Foundation. Pp. 1-59. 1950a. Notes on three microsporidian parasites of decapod Crustacea of Louisiana coastal waters. Occasional Pap. Marine Lab. Louisiana State Univ. 5: 1-8. ViOSCA, p. 1943. A critical analysis of practices in the management of warm-water fish with a view to greater food produc- tion. Trans. Am. Fisheries Soc. 73: 274-283. Wichterman, R. 1940. A new ciliate from a coral of Tortugas. Jour. Parasit. 26 (Suppl.) : 25-26. 1942. Cytological studies on the structure and division of three new ciliates from the littoral earthworm of Tortugas. Papers Tortugas Lab. Carnegie Inst. Washington Pub. 524: 83-103. 1942a. A new ciliate from a coral of Tortugas and its symbiotic zooxanthellae. Papers Tortugas Lab. Carnegie Inst. Washington Pub. 524: 105-111. CHAPTER VIII SPONGES, COELENTERATES, AND CTENOPHORES THE PORIFERA OF THE GULF OF MEXICO By J. 0- TiERNEY, Marine Laboratory, University of Miami Sponges are one of the dominant sessile inverte- brate groups in the Gulf of Mexico: they extend from the intertidal zone down to the deepest parts of the basin, and almost all of the firm or rocky sections of the bottom provide attachment for them. Members of the class Hyalospongea (Hexacti- nellidea) are, almost without exception, limited to the deeper waters of the Gulf beyond the 100- fathoni curve. These sponges possess siliceous spicules in which (typically) six rays radiate from a central point; frequently, the spicules are fused together forming a basket-like skeleton. Spongin is never present in this group. In contrast to the Hyalospongea, representa- tives of the class Calcispongea are seldom, if ever, found in deep water. These sponges, unique in having spicules of calcareous material, are usu- alh' restricted to shallow water. They are not conspicuous; typically, they are encrusting forms or tubiform in shape but only a few centimeters in height. The major sponge group in the Gulf of Mexico, both from number of genera and from the range of distribution, is the class Demospongea. Pos- sessing more or less spongin, and when spicules are present having unfused spicules of siliceous material, these sponges occur throughout the Gulf extending from the shallow coastal waters down to the deepest ofF-shore sections of the basin. The sponge bars or reefs of the eastern Gulf are quite typical of the habitat and ecology of the sponges in shallow to moderate depths. These so-called reefs are sections of rocky outcroppings that are elevated a few inches to a few feet above the general bottom profile. They are more or less densely covered with commercial and non-com- mercial sponges, coral (usually Oculina), and Alcyonaria. The other bottom-dwelling marine groups (such as mollusks, annelids, Crustacea, ascidians) are associated with the dominant • Contribution No. lO.'i. Marine Laboratory, University of Miami. 259534 O— 54 18 groups. The floor of the Gulf between the bars is sparsely populated. The majority of the ani- mals and plants are concentrated on the rocky ledges and outcroppings. The most abundant sponges on these reefs are of several genera representing most of the orders of the class Demospongea. Several species of Ircinia are quite common as are Verongia, Sphecio- spongia, and several Axinellid and Ancorinid sponges; Cliona is very abundant, boring into molhiscan shells, coral, and the rock itself. The sponge population is rich both in variety and in number of individuals; for this reason no attempt is made to discuss it in taxonomic detail in this resume. Some of the sponges of the Gulf are of world- wide distribution, i. e., Dysidea fragilis, while others are typically West Indian, and a few are probably restricted to the Gulf. The West Indian sponge fauna may be a single regional population with only minor locational differences. Water currents of the Caribbean, the Gulf, and the southern portion of the western Atlantic off Florida and the Bahama Islands have been shown to to carry a sponge disease from one point to many others in this region; it is therefore permissible to suggest that the same currents would be equally effective in distributing sponge larvae. The commercial sponges of Florida, the Ba- hamas, Cuba, and British Honduras are all quite similar: the sheepswool sponge, Hippiospongia lachne, is the most valuable sponge now available for the market. Reef, glove, yellow, and grass sponges, all members of the genus Spongia, are of less value and are therefore less eagerly sought by the sponge fishermen. Two methods, in general, are used in the West Indian region for the collection of commercial sponges. Hooking is practiced in waters of less than 7 or 8 fathoms throughout the entire zone, and light-weight, full diving rigs are used in the Gulf of Mexico in depths of less than 20 fathoms. 259 260 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE In addition to these two major methods a few native islander fishermen skin-dive for sponges in shallow water, and a few Florida sponge fishermen have begun in the past few years to drag tines and other types of dredges in order to obtain more sponges with less work. As a result of the constantly decreasing supply of natural sponges there have been repeated attempts in the past half century to establish sponge farms in the shallow coastal waters of Florida and the other Caribbean sponge producing areas. Practical as they now are from a biological point of view, these farms have always failed because of economic difficulties. It is now entirely possible, however, to produce artificially propa- gated sponges as a sound commercial venture. In addition to the biological studies on the dis- tribution and growth of the Gulf of Mexico porifera, there have been biochemical studies car- lied out on the lipids, the carbohydrates, and the general chemical constitution of several of the more common marine sponges of this region. BIBLIOGRAPHY Agassiz, Alexander 1888. Characteristic deep sea types. Sponges. (Prepared from the memoirs of O. Schmidt on Atlantic and Caribbean sponges.) Bull. Mus. Comp. Zool., 15: 170-179, 25 figs. Bartsch, p. 1936. Sponge cultivation. Science, 83 (2164): 597. Bergmann, Werner 1949. Comparative biochemical studies on the lipids of marine invertebrates, with special reference to the sterols. Sears Foundation Jour. Mar. Res., 8 (2) : 137-176, figs. 1-2. Brown, H. H.; Galtsoff, P. S.; Smith, L. C; and Smith, F. G. W. 1939. Sponge mortality in the Bahamas. Nature, 143 (3628): 807-808. Carter, H. J. 1884. Catalogue of marine sponges, collected by Mr. Jos. Willcox, on the west coast of Florida. Proc. Acad. Nat. Sci. of Philadelphia 36: 202-209. Cobb, J. N. 1903. The sponge fishery of Florida in 1900. Rept. U. S. Fish Comm. 1902. Crawshay, L. R. 1939. Studies in the market sponges. I. Growth from the planted cutting. J. M. B. A. United Kingdom 23 (2) : 553-574, 1 fig. De Laubenfels, M. W. 1932. Physiology and morphology of Porifera exempli- fied by lotrochota birotulata Higgin. Carnegie Inst. Washington Pub. 435, Pap. Tortugas Lab. 28: 39-66, 2 pis., 6 figs. De Laubenfels, M. W. — Continued 1934. New sponges from the Puerto Rican Deep. Smithsonian Misc. Coll. 91 (17): 1-28. 1936a. A discussion of the sponge fauna of the Dry Tortugas in particular and the West Indies in gen- eral with material for a revision of the families and orders of the Porifera. Carnegie Inst. Washington Pub. 467, Papers Tortugas Lab. 3: 1-225, pis. 1-22, text figs. 1936b. A comparison of the shallow water sponges near the Pacific end of the Panama Canal with those at the Caribbean end. Proc. U. S. Nat. Mus. 83 (2993) : 441-466, 6 figs. 1939. Sponges collected on the presidential cruise of 1938. Smithisonian Misc. Coll. 98 (15): 1-7, 1 fig. 1948. The order Keratosa of the phylum Porifera, a monographic study. Allan Hancock Found. Occ. Paper 3, pp. 1-217, pis. 1-30, text figs. 1-31. 1949. Sponges of the western Bahamas. Am. Mus. Novitates 1431, pp. 1-25, illus. Duchassaing, de Fonbressin p., and Michelotti, G. 1864. Spongiaires de la Mer Caraibe. Memoire public par la Society hoUandaise des Sciences ^ Haarlem. Natuurk. Verh. Mij. Haarlem, 21: 1-124, pis. 1-25. Galtsoff, P. S. 1940. Wasting disease causing mortality of sponges in the West Indies and Gulf of Mexico. Proc. Eighth Scientific Congress 3: 411-421, 2 pis., 2 text figs. 1946. Sponges. U. S. Fish and Wildlife Service, Fishery Leaflet 4, pp. 1-7. HiGGIN, T. 1875. On a new sponge of the genus Luffaria, from Yucatdn, in the Liverpool Free Museum. With re- marks by H. J. Carter. Ann. and Mag. Nat. Hist. Ser. 4, 16: 223-227, pi. 6. Hyatt, A. 1875. Revision of the North American Poriferae; with remarks upon foreign species. Part I. Mem. Boston Soc. Nat. Hist. 2: 399-408, pi. 13. 1877. Revision of the North American Poriferae; with remarks upon foreign species. Part II. Mem. Boston Soc. Nat. Hist., 2: 481-554, pis. 15-17. Kent, W. S. 1883. Report on the sponges of the Bahama Islands. Aubert's Steam Printing Works. Pp. 1-18. Moore, H. F. 1908a. Commercial sponges and the sponges fisheries. Bull. Bur. Fish. 28: 399-512, pis. 28-66. Moore, H. F. 1908b. A practical method of sponge culture. Bull. Bur. Fish. 28: 545-586, pis. 67-76. Old, M. C. 1941. The taxonomy and distribution of the boring sponges (Clionidae) along the Atlantic coast of North America. Chesapeake Biol. Lab. Contr. 44, pp. 1-30, 1 fig., pis. 1-10. Osorio-Tafali-, B. F., and Cardenas, Mauro 1945. Sobre las esponjas comerciales de Quintana Roo y una enfermedad que las destruye. Ciencia 6 (1): 25-31, 2 figs. GULF OF MEXICO 261 Pearse, a. S. 1932. Inhabitants of certain sponges at Dry Tortugas. Tortugas Lab. Papers 28, Carnegie Inst. Washington Pub. 435, 28: 117-124, 2 pis., 1 text fig. RoiG, Mario Sanchez 1945. Sponge riches of Cuba. Rev. Agric. (Havana) 28 (1): 25-32. Schmidt, Oscar 1879. Reports on the dredging, under the supervision of Alexander Agassiz, in the Gulf of Mexico. Die spongien des meerbusen von Mexico. Erstes Heft., 32 pp., pis. 1-4, Gustav Fischer, Jena. 1879. Die Fortsetzung meiner "Spongien des Meerbusens" von Mexico. Zool. Anz. 2, 379-380. 1880. Reports on the dredging, under the supervision of Alexander Agassiz, in the Gulf of Mexico. Die spon- gien des meerbusen von Mexico (and des Caraibischen meeres). Zweites Heft., pp. 33-90, pis. 5-10. Gustav Fischer, Jena. Smith, F. G. Walton 1941. Sponge disease in British Honduras and its transmission by water currents. Ecology 22: 415-421, figs. 1-3. 1949. Report on a survey of the sponge grounds north of Anclote Light. Mimeographed. Florida State Board of Conservation, pp. 1-29, figs. 1-4. Smith, Hugh M. 1899. Notes on the Florida sponge fishery in 1899. Bull. Bur. Fish. 19: 149-151. Smith, Huoh M. — Continued 1899. Tiie Florida commercial sponges. Bull. Fish. Comm. 17: 225-240, pis. 12-31. Stuart, A. H. 1948. World trade in sponges. U. S. Dept. Comm. Indust. Ser. 82, pp. 1-95, figs. 1-6, pis. 1-20. TiERNBT, J. Q. 1949. The sponge industry of Florida. Florida State Bd. of Conserv., Ed. Ser. 2, pp. 1-19, figs. 1-4. 1951. A report on the sponges collected during the University of Miami Marine Laboratory Gulf of Mexico 1947-48 sponge investigation. Univ. Miami Marine Lab. Pub. In press. Von Lendenfeld, R. 1889. A monograph of the horny sponges. Truebner and Company, London. 936 pp., pis. 1-50. VOSMAER, G. C. J. 1887. Porifera. In: Bronn, H. G., Die Klassen und ordnungen des Thier-reichs-Zweiter Band. Pp. 369-496, pis. 26-34. 1933. The sponges of the Bay of Naples. Martinus Nijhoff, The Hague. Vol. 1 and vol. 2, pp. 1-828. Vol. 3, pis. 1-71. Wilson, H. V. 1902. The sponges collected in Porto Rico in 1899 by the U. S. Fish. Comm. Bull, for 1900, 2: 375-411. 1925. Studies on dissociated sponge cells. Carnegie Inst. Yearbook No. 24, 1925, pp. 242-246. BIOLOGY OF THE COMMERCIAL SPONGES' By F. G. Walton Smith, Marine Laboratory, University of Miami All commercial sponges of the Gulf of Mexico belong to the family Spongiidae. They are char- acterized bj' a lack of spicules and by the presence of a skeleton consisting of a network of anastomo- sing spongin fibers. The canal system is of the leucon type. Subdermal cavities which act as vestibules to either the incurrent or excurrent canal systems, or both, are present to a varying degree and are particularly noticeable in the velvet sponge, Hippiospongia gossypina. The external form is roughly subspherical in the case of sheepswool sponge, Hippiospongia lachne, the yellow sponge, Spongia zimocca ss. harhara, hard head, Spongia officinalis ss. dura, and the velvet sponge. The grass sponge, Spongia graminea, may be in the form of an up- right cylinder, somewhat wider and slightly con- cave in the upper surface. Large sponges of this type in the Gulf of Mexico waters, however, are usually cup-shaped. Other sponges sometimes found are the reef sponge, Spongia officinalis ss. ohliqua. These are small sponges somewhat cylindrical in general shape but with lobes ter- minated by oscula on the upper surface. The glove sponge, assigned to Spongia graminea, is stoutly columnar with fluted sides. The shape and appearance varies considerably according to the environment. Detailed descriptions of the various forms are given by Moore (1910). The outer surface is covered with a thin but tough skin which is usually dense black in color. Portions of the sponge buried in mud and the basal portions are more or less deficient in pig- ment. The flagellated chambers of all commer- cial sponges are small in size and are pyriform or subspherical in shape with a diameter of no more than 0.03 mm. The choanocA'tes are approxi- mately 4 microns in cross section. Spongin fiber has been auahzed by Block and Boiling (1939). It is composed of keratin, an in- ert product related to the collogens. Keratin ' Contribution No. 109 from the Marine Laboratory, University of Miami. contains iodine and the amino acids Ij'sine, argi- nine, cystine, phenylalanine, and glycine. Very small amounts of histidine and tyrosine are also present. Sexual reproduction takes place at all times of the year but most intensively during April, May, and June, and in November and December, ac- cording to observations made by the author in the Bahamas Islands. Eggs are found in sponges as small as 2 inches in diameter. They are im- bedded in the tissues between the flagellated chambers and are about 0.25 cm. in diameter. In their early stages of development they are white but become a dark olive green as the embryo develops. Whereas eggs are easily visible to the naked eye when a sponge is sliced open, the spermatozoa are not recognizable except under the microscope. No information is available as to whether spermatozoa and eggs are produced by the same sponge at different times. Since they have not been observed in the same sponge at the same time, it is possible that commercial sponges are dioecious. Toward the end of embryonic development the embryo develops a circle of cilia at the anterior, less strongly pigmented end. The larva then escapes into the excurrent canal system and thence to the exterior. Further development has not been observed in detail in commercial sponges. There is little definite evidence as to the food of sponges. Ingestion of carmine particles by the choanocytes has been observed by Bidder (1896) and subsequent authors, in the non-commercial sponges. According to Bidder, the flagellated cells of Sycon raphanus, which are 5 microns in width, contain rod-shaped bodies similar to bacilli between 1 and 2 microns long. Pourbaix (1931) describes the transference of carmine grains from choanocytes to adjacent amoebocytes. PourbaLx (1931) also states that after feeding with carmine, granules of this appeared in the amoebocytes of the Tunisian commercial sponge. 263 264 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE It seems fairly certain that any solid food used by the sponge must be very small in size and that it is carried into the flagellated chambers by the internal water circulation. The large quantities of bacteria found in the calcareous muds of the Bahamas in the vicinity of commercial sponges suggests that these organisms may be an impor- tant constituent of the food of these sponges. It has been suggested, however, that sponges may also be able to absorb dissolved organic nutrients. Very little is known about the physiology of commercial sponges. Bidder (1923), Parker (1914), and others have studied the water cur- rents. These are set up by movements of the flagella of the choanocytes. These appear to operate independently of each other. The enor- mous number of flagellated chambers provides the energy whereby a considerable volume of water is pumped through the sponge. In noncommer- cial species, such as Spinosella, it has been shown that although the volume of water is great, the pressure does not amount to more than 5 mm. in height of water. The jet stream leaving the osculum may be detected at several inches dis- tance and is sufficient so that on a calm day a distinct disturbance of the water surface may be seen above commercial sponges which are near to the surface. The oscula may be closed by muscular action when stimulated locally. Bergmann (1949) and his associates have de- scribed in a series of papers the extraction of sterols from sponges. There is a considerable degree of specificity in the type of sterol found in various sponges, and this bears a close relation to taxonomic classification. Although the com- mercial sponges-'so far investigated have a high fat content, the sterol content of the unsaponifi- able matter is lower than the average. The sterols of commercial sponges have not yet been ana- lyzed in detail. Commercial sponges are typically found asso- ciated with muddy bottom sediments, particu- larly where rocky outcrops or reefs provide a suitable substrate upon which the larva can settle without being destroyed by silt. They are some- times found growing attached to dead corals or gorgonians and may occasionallj' grow upon living green algae, such as Penicillus. Under these con- ditions the alga may eventually become com- pletely imbedded in the sponge except for the lower portion of its stalk. Commercial sponges appear to flourish where there is a good flow of water but not under very exposed conditions. They are rarely found upon bottoms consisting entirely of rock or, of course, sediments. In the Gulf of Mexico they are found down to a depth of at least 150 feet and in water close to low tide mark. They are not tolerant to reduced salinity except for short periods. They appear to be more resistant to temperature changes, however. A considerable number of other organisms are associated with sponges. The surface is frequently covered with encrusting Bryozoa and colonial tunicates. All species of the piling fauna normally found in the vicinity may be epizoic upon com- merical sponges. The green alga, Batophora oerstedi, and species of Acetabularia also become attached to the sponge surface. The starfish, Echinaster, is sometimes observed upon sponges which have lesions of the outer skin, but it is not certain to what extent the damage is caused by this animal. Nudibranchs are sometimes found in small pits or irregularities of the surface, and it is possible that they may feed upon the sponge tissue. Larger holes may be mhabited by various species of small crabs. Dromia is often a perma- nent inhabitant of such places. The green alga, Dictyosphaeriafavulosa, grows in convenient niches and may become almost enclosed by the subse- quent growth of the sponge. A number of the smaller and commoner gastropods are also found inhabiting cavities of the sponge surface which may have been caused by local necrosis, the activities of carnivores or overgrowth of the sponge around sedentary organisms. The barna- cle, Balanus dedivis, which is more commonly found in noncommercial species of sponges, is occasionally seen imbedded in the surface of commercial tj'pes. A considerable fauna inhabits the larger passages of the canal S3'stem. Pearse (1934) lists a large ninnber of organisms inhabiting a reef sponge at Dry Tortugas. The most commonly found in all commercial sponges are the snapping shrimp, Syvalpheus brooksi. and the polychaete worm, Leodice spongicola. Other species of polychaetes are also found, particularly syllids and occasionally Amphitrite. Among other Crustacea occurring here are the pontonid shrimp, Coralliocaris pearsei, and num- erous amphipods of the genera, Leucothoe and GULF OF MEXICO 265 Colomaestir. The stomatopod, Gonodacfylus oer- stedi, and small crabs may inhabit the larger passages. Ophiuroids, particularly Ophiacth samgny, are found both in surface depressions and in the larger portions of the canal system. The anemone, Aiptasia, appears to form depressions in the surface of sponges into which it is able to retreat. The most destructive organism is apparently a species of fungus which caused widespread and intensive mortality among the Gulf of Mexico and Caribbean sponges in 1939. GaltsoflF (1940) ten- tatively identifies the organism as Spongiophaga communis which was first observed to be parasitic upon sponges by Carter (1878). Since it was not possible to culture the organism, it cannot defi- nitely be assigned to any particular group of fungi. Further accounts of this sponge disease are also given bj^ Walton Smith (1941) and by Osorio-Tafall (1945). A number of observations have been made by Galtsoff, Wilson, and others, upon the ability of disassociated sponge cells to re-aggregate. This earlier work is also referred to by de Laubenfels (1934) in experiments upon the regeneration of lotrochota. The growth rate of sponges has been measured by Crawshay (1939) who measured the increase in size of small cuttings sliced from commercial sponges. He found that the velvet sponge grows at such a rate as to approximately double or treble its volume in the period of a year. Extensive unpublished series of measurements by the present author have shown that the growth expressed as a percentage of size diminishes with increasing size in the case of both sheepswool and velvet sponges. When these sponges reach approximately 12 inches in diameter the central portion of the upper surface begins to undergo local necrosis so that the larger sizes become somewhat doughnut- shaped. This is apparently due to the loss of effi- ciency in respiratory, excretory, and nutritive exchanges related to a diminution in the sur- face/volume ratio. The increase in percentage growth rate with decreasing size makes it possible to cultivate sponges by cutting them into small pieces and by planting each piece upon a stone or cement base. Regeneration of the cut surfaces takes place rapidly, and the sponge quickly attaches itself to the stony surface. Other methods used in sponge cultivation are described by Smith (1949), Moore (1910b), Crawshay (1939), and Cahn (1948). BIBLIOGRAPHY Bbrgmann, Werner. 1949. Comparative biochemical studies on the lipids of marine invertebrates, with special reference to the sterols. Jour. Mar. Res. 8 (2): 137-176. Bidder, G. P. 1896. The collar-cells of Heterocoela. Quart. Jour. Micro. Sci., N. S., 38: 9-42. 1923. The relation of the form of a sponge to its cur- rents. Quart. Jour. Micro. Sci., N. S., 67 (2); 293-323. Block, R. J., and Bolling, D. 1939. The amino acid composition of keratins. Jour. Biol. Chem., Vol. 127. Cahn, A. R. 1948. Japanese sponge culture experiments in the South Pacific Islands. U. S. Fish and Wildlife Serv- ice, Fish. Leaflet 309, 9 pp. Carter, H. J. 1878. Parasites of the Spongida. Ann. Mag. Nat. Hist., Ser. 5, 2: 165-169. Crawshay, L. R. 1939. Studies in the market sponges. I. Growth from the planted cutting. Jour. Mar. Biol. Assn., U. K., 23 (2) : 533-574. Galtsoff, P. S. 1929. Heteroagglutination of dissociated sponge cells. Biol. Bull. 57 (5) : 250-260. 1940. Wasting disease causing mortality of sponges in the West Indies and Gulf of Mexico. Proc. Eighth Am. Sci. Cong. 3: 411-421. Hyman, L. H. 1940. The invertebrates: Protozoa through Ctenophora. Vol. 1, pp. 284-364, McGraw-Hill Book Co., New York. Laubenfels, M. W., de 1934. Physiology and morphology of Porifera exem- plified by lotrochota birotulata Higgin. Carnegie Inst. Washington Pub. 435, Papers Tortugas Lab. 28 (2): 37-66, 2 pis., 6 text-figs. 1936. A discussion of the sponge fauna of the Dry Tortugas . . . Carnegie Inst. Washington Pub. 467, Papers Tortugas Lab. 30: 1-225. 1948. The order Keratosa of the phylum Porifera. A monographic study. Allan Hancock Found. Occas. Papers, vol. 3: 1-217, pis. 1-30, figs. 1-31. Lendenfeld, R., Von 1889. A monograph of the horny sponges. 936 pp., 50 pis. Triibner Co., London. Lindner, M. J. 1948. Mexican sponge fishery. Sponge Inst. Trade Rept. 64. Moore, H. F. 1910a. The commercial sponges and the sponge fish- eries. Bull. U. S. Bur. Fish., 1908, 28: 399-511, pis. 28-66. 266 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Moore, H. F. 1910b. A practical method of sponge culture. Bull. U. S. Bur. Fish.. 1908, 28: 545-586. Osorio-Tafall, B. F. 1945. Sobre lase sponjas commerciales de Quintana Roc y una enfermedad que las destruye. Ciencia 6 (1): 25-31, 2 figs. Parker, G. H. 1914. On the strength and volume of the water currents produced by sponges. Jour. Exp. Zool. 16 (3): 443-446. Pearse, a. S. 1934. Inhabitants of certain sponges at Dry Tortugas. Carnegie Inst. Washington Pub. 435, Papers Tor- tugas Lab. 28: 117-124. POURBAIX, N. 1931. Notes sur Hippiospongia equina au voyage d'6tude h, Adjim-Djerba. Stat. Oceanog. Salammbd, Bull. 22. Smith, F. G. Walton. 1941. Sponge disease in British Honduras and its transmission by water currents. Ecology 22 (4) : 415-421. 1949. Sponge cultivation. Mar. Lab., Univ. of Miami, Spec. Serv. Bull. No. 3. (Mimeo.) TiERNEY, J. Q. 1949. The sponge industry of Florida. State of Florida, Bd. of Conserv., Mar. Lab., Univ. Miami Pub., Educ. Ser. No. 2, pp. 1-19, figs. 1-4. HYDROIDS OF THE GULF OF MEXK^O By Edward S. Deevey, Jr., Osborn Zoological Laboratory, Yale University The life cycle of hydroids "typically" alternates between a sessile, asexually reproducing polyp or hydroid stage and a free-swimming sexual medusa stage. One generation or the other may be re- duced, however, or even suppressed entirely. Because of this fact and because hydroids are obtained by shore collectors or bj^ dredging, whereas medusae form part of the plankton and are studied by different zoologists, the ta.xonomy of the group, is in an unhappy state. Closely related types may differ in a respect that at first sight would appear fundamental: the polyp may produce free-living medusae, or the medusa may remain permanently attached to the polyp, even degenerating completely except for its sex products, which then appear to be the sex products of the polyp. This distinction, far from being of subordinal rank, may split a genus down the middle or, at most, may divide closely related genera from each other, according to one's view of what constitutes a generic character. That is, unless the structural characters of the hydroid are to be given no weight whatever, the mode of reproduction cannot provide the basis for erecting taxonomic categories higher than the genus. Thus, the hjxlrozoan systematist faces a real dilemma, and he is not helped by the fact that many typically reproducing species have received different names as medusae and as polyps and must continue to bear them until proof of their identity is obtained. The writer is not a student of medusae, and in fact his knowledge of hydroids is largely confined to specimens preserved in alco- hol. He is in no position to do anything abouc the fact that even the families are differently constituted in hydroid and medusa systematics, and the task of fusing the two systems awaits an abler zoologist. This chapter deals exclusively with hydroids. The hydroid fauna of the Gulf of Mexico is little known, and the chief purpose of this account is to document this fact. A treatise on the Gulf of Mexico is a peculiarly appropriate setting for such a catalog of ignorance, for what we do not know about GuF hydroids should be especially obvious against the massive backdrop of what we know about the biology of the Gulf. COLLECTING Hydroid collect uig in the Gulf of Mexico has been chiefly undertaken in the Tortugas and the Florida Keys, but if we except the work of Mayer (1910) as dealing almost entirely with medusae, the only paper sp' ifically discussing the Tortugas fauna is that of Wallace (1909). Gulf of Mexico records are scattered through many papers (Fraser 1943, 1945; Jaderholm 1896, 1903, 1920; Leloup 1935, 1937; Perkins 1908; Pourtales 1869; Stechow 1912, 1919, 1923, 1926) and through the mono- graphs of Nutting (1900, 1904, 1915), but system- atic dredging in the region has not been under- taken since the days of the Corwin and the Blake. The collections of h. de Pourtales on the former vessel were reported by Allman (1877), and those of A. Agassiz on the latter were published by Clarke (1879) and Fewkes (1881). The monograph of Fraser (1944) recapitulates all the earlier records and adds many more, for Fraser xamined the large collections in the U. S. National Museum and the Museum of Comparative Zoology whither most of the Amer- ican hydroids collected in the nineteenth century eventually made their way. It is possible to extract from Fraser's book an essentially com- plete picture of the hydroid fauna of the Gulf as far as it is known. In fact, this procedure is the basis of the present account. Fraser's list has been expanded in only one noteworthy respect. The survey of fouling on navigation buoys, conduct 1 by the Woods Hole Oceanographic Institution during World War II, yielded several hur !red records of hydroids from the Bahamas,- both coasts of Florida, and Texas. Most of these are still unpublished, but those that are new 267 268 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE records from the Gulf proper are starred in the check list. The Texas records are of exceptional interest, however, as only three hydroids had previously been recorded from those waters; they were included in the writer's account of the hydroids of Louisiana and Texas (Deevey 1950), a zoogeographic discussion that was founded primarily on a small collection made by J. W. Hedgpeth. ZOOGEOGRAPHY The list of 183 species looks impressive, but it would be idle to pretend that the hydroids of the Gulf are well-known. Tropical regions gen- erally have a wealth of species, but hydroid habitats are probably no more extensive in the tropics than elsewhere. The rarity of the rarest species is correspondingly greater, and it is un- likely that more than half the hydroids living in the Gulf have yet been found there. Partly because of inadequate collecting and partly be- cause shallow water hydroids are always under suspicion as fouling organisms, little can be said about the meaning of their geographic distribution. Of the total of 183 hydroid species known from the Gulf of Mexico, 95 are also found in the Caribbean and another 18, though not yet re- corded from the Caribbean, are known from the eastern tropical Pacific. The remaining 70 species include some of the most interesting. Some of the 70, of course, are known only from the Gulf, but while a few true endemics are to be expected it is too early to say which ones they are; at any rate, no common species is known to be endemic. The interesting members of the group of 70 are those whose main range is otherwise boreal. The boreal species among the hydroids of Texas and Louisiana have already been dis- cussed (Deevey 1950). They include several, such as Podocoryne carnea, that are unknown in the warmer parts of the Gulf, and at least one, Tubularia crocea, whose ecology is well enough understood to indicate that it could not flourish in southern Florida. To the list of supposed relicts of a glacial age of the Pleistocene given in the earlier paper may be added the name of Cladocarpus jiexilis, a moderately deep water species taken at three stations off Mobile but not otherwise known south of Cape May. In several other cases we have the familiar phenomenon of a shallow water boreal species occurring at consid- erable depths in the Gulf (and Caribbean): Eudendrium tenellum, Lafoea dumosa, L. gracillima. Another way of looking at the facts is this: of 156 species known from the Caribbean, 61 are not known from the Gulf; 29 of them, at least, are common enough in the Caribbean to have been taken at more than one station. Hydroid sta- tistics are scarcely necessary to prove the point, but it is obvious that the Gulf is not a strictly tropical body of water. Low winter temperatures and low and variable salinity, particularly along the northwestern shore, are only some of the fac- tors that must be responsible for maintaining a different "fauna" in the Gulf of Mexico. The 95 species that are common to the Gulf and the Caribbean present different problems. Most of them are definitely warm water types, although a high proportion belong to the tropical flotsam (especially sargassum) fauna and so may not be true residents of the Gulf. Seventy of the Gulf hydroids and 59 of the 156 Caribbean species are represented in the much larger list of 312 species recorded from the eastern tropical Pacific. The richness of the Pacific fauna, which is known almost exclusively from the Allan Hancock collec- tion (Fraser 1948), is another indication that the Caribbean hydroids have been inadequately col- lected; it is surely correct to suppose that the 18 species common to the Gulf and the eastern trop- ical Pacific will appear in the Caribbean, along with many others. Wliat is surprising is that nearly half of the tropical Atlantic hydroids cross the Isthmus of Panama without undergoing specific differentiation. If one cares for statis- tical statements, the "strength of the relation- ship" between the Gulf and Pacific faunas is nearly as great (38 percent) as is that between the Gulf and Caribbean faunas (52 percent). The Isthmus of Panama is not very old, and many biogeographers have supposed that it is younger than most of the species of marine organ- isms (Schuchert 1935). The problem is related to that of Tethyan distributions; pan-tropical species (more usually genera) are supposed to have had their ranges established in the Tethys Sea, of Cretaceous and early Tertiary age, only to have them sundered by the rise of central Asia (see Ekman 1934, 1935, for review). If disjunct distributions in the Mediterranean and the GULF OF MEXICO 269 Indian western Pacific regions have liad this origin, there is no reason to doubt that the Isthmus of Panama was crossed about the same time by the same species, or some of them. The species that are perhaps most likely to have spread so widely and to have crossed modern land bar- riers so freely are now truly pan-tropical species, but the evidence they provide, according to the conventional canons of biogeography, is ruled invalid by the possibility that they are spreading today. Unhappily, if one chooses to follow the rules and exclude the pan-tropical species, it can only be said that the remaining species prove nothing, at least as far as hydroids are concerned. The reason is not so much biogeographic as taxonomic. The number of hydroids common to the two sides of Central America is large, but an even larger number is common to th^ two coasts of North America taken as a whole. According to Eraser's tabulation (1944), 123 species are known from east and west coasts of the Americas, and by no means all of these are circumpolar. Neither are the tropical species all pan-tropical. The "American" distribution pattern is far too com- mon to be accidental, but its commonness raises doubts about the taxonomy. Fraser was a sound, careful worker with a "good eye" for specific differences. However, his experience, though enormous, was largely confined to the Americas. When one remembers that the hydroids of the East Indies are poorly known (only tlrree families of the Siboga hydroids having beea reported by Billard before his death), one cannot escape the suspicion that many species apparently endemic to the American tropics are still to be collected, or are already known under other names, from other parts of the world. Apart from this tax- onomic difficulty, inadequate knowledge of the hydroids of the western Pacific and Indian Oceans imposes another limitation on the case for Tethyan paleogeography, for western Atlantic-western Pacific disjunctions have often been used (however unwisely) in building such a case, and we know of no certain examples among hydroids. Until the hydroids of the world have been given much more study and some monographic revision, then, it is unsafe to use them for many zooge- ographic purposes. CHECK LIST OF GULF OF MEXICO HYDROIDS Geographic distribution is indicated by the following symbols: K, Florida Keys, including Cay Sal Bank and southern Florida as far east as Miami, but not the Bahamas. T, Tortugas. C, Cuba. Y, Yucatan. NW, northwestern Gulf (Texas, Louisiana). NE, northeastern Gulf (including Tampa Bay). Ca, Caribbean Sea. EP, eastern tropical Pacific Ocean, south of United States-Mexico boundary, and including the oceanic islands. *, starred names are new records for the Gulf of Mexico, found in the Woods Hole Oceanographic Institution fouling collection. Suborder Gymnoblastea (Anthomedusae), athecate hydroids Cordylophora lacustris Allman, 1844. NW; Ca. Turritopsis fascicularis FT&seT, 1943. K. *Turritopsis nulricula McCrady, 1856. K; Ca, EP. Syncoryne eximia ' (Allman, 1859). NW. Syncoryne mirabilis L. (Agassiz), 1862. K; EP. Zanclea costala Gegenbaur, 1856. T, NW; Ca, EP. Zanclea gemmosa McCrady, 1858. T; EP. Bimeria franciscana Torrey, 1902. NW; B. Bimeria humilis Allman, 1877. T, NW; Ca. BougainvUlia carolinensis (McCrady, 1858). T, NW. Bougainvillia inaequalis Fraser, 1944. NW. BougainvUlia rugosa Clarke, 1882. NW; Ca. Eudendrium album Nutting, 1898. K; EP. Eudendrium allenualum Allman 1877. T; EP. Eudendrium carneum Clarke, 1882. T; Ca, EP. Eudendrium distichum Clarke, 1879. K. Eudendrium eiiguum Allman, 1877. K; Ca, EP. Eudendrium eiimium Allman, 1877. K, NE; EP. Eudendrium fruticosutti A\lma,n, 1877. K. Eudendrium gracile ■\llman, 1877. K. Eudendrium hargitti Congdon, 1906. T. Eudendrium laxum Allman, 1877. K; Ca. Eudendrium speciosum Fraser, 1945. NE. Eudendrium tenellum Allman, 1877. K; Ca, EP. Eudendrium tenue A. Agassiz, 1865. NW?; Ca, EP. H ydraclinia echinala Fleming, 1828. K, NW. Podocoryne carnea Sars, 1846. NW. Pennaria liarella (Ayres, 1854). K, T, C; Ca, EP. ' N. J. Berrill, in a letter to the author, has given good reasons for suspect- ing that the species reported under this name from Texas and from western Florida (Deevey 1950), is an undescribed species. 270 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Eclopleura grandis Fraser, 1944. K, NW. Tubularia crocea (L. Agassiz, 1862). NW; EP. Cladonema mayeri Perkins, 1906. T. Suborder Calyptoblastea (Leptomedusae), thecate hydroids Family CAMPANULARIDAE Campanularia amphora (L. Agassiz, 1862). T? Campanularia (?) brevicaulis Nutting, 1915. Y. Campanularia flexitosa (Hincks, 1861). T? * Campanularia (?) hummelincki (Leloup, 1935). K; Ca. Campanularia (?) macroscypha Allman, 1877. K, T, Y. Campanularia marginata (Allman, 1877). K, T, C; Ca. Clytia coronata (Clarke, 1879). K, NW; Ca, EP. Clytia cylindrica L. Agassiz, 1862. K, NW; Ca, EP. Clytia fragilis Congdon, 1907. T, NW; Ca. Clytia johnsloni (Alder, 1856). K, T; EP. Clytia longicyatha (Allman, 1877). K, T, NW; Ca, EP. Clytia macrotheca (Perkins, 1908). K, T; Ca. Clytia mimda (Nutting, 1901). T? Clytia noliformis (McCrady, 1858). T, NW; Ca, EP. *Clytia raridentata (Alder, 1862). K; Ca, EP. Gonothyraea gracilis (Sars, 1851). K, NW; Ca, EP. Obelia bicuspidata Clark, 1876. K, NW, NE; Ca. Obelia commissuralis McCrady, 1858. T?; EP. Obelia dichotoma (Linnaeus, 1758). K, T, C, NW, NE; EP. Obelia equilateralis Fraser, 1938. NW; Ca, EP. Obelia geniculata (Linnaeus, 1758). NW; Ca, EP. Obelia hyalina Clarke, 1879. K, C; Ca, EP. Obelia obtusidens (Jaderholm, 1904). NW; EP. Family CAMPANULINIDAE *Cuspidella costata Hincks, 1868. K. Cuspidella humilis (Alder, 1862). NW; EP. Eucuspidetla pedunculata (Allman, 1877). T. *Lafoeina tenuis Sars, 1873. K, NE. Oplorhiza parvula Allman, 1877. K. Stegopoma fastiginta (Alder, 1860). T. Thyroscyphus ramosus Allman, 1877. K, T; Ca. Family HALECIDAE Halecium bermudense Congdon, 1907. K, T, NE; Ca, EP. Halecium dyssymetrum ^ Billard, 1929. K, T. Halecium filicula Allman, 1877. K. Halecium gracile Verrill, 1874. K; EP. Halecium macrocephalum Allman, 1877. K, T; EP. Halecium nanum Alder, 1859. K, T, NW; Ca, EP. Halecium tenellum Hincks, 1861. T, NE; Ca, EP. Family HEBELLIDAE Hebella calcarata (A. Agassiz, 1865). NE; Ca, EP. Scandia mutabilis (Ritchie, 1907). T; Ca, EP. ' Preliminary study of this species in the Woods Hole Oceanographic In- stitution fouling collection indicates that it is probably the //. dtjssrjmetrum of Leloup (1935) but not of Billard, and that it needs a new name. Family LAFOEIDAE Acryptolaria abies (Allman, 1877). K; Ca. Acryptolaria conferta (Allman, 1877). T, C; Ca, EP. Acryptolaria elegans (Allman, 1877). K, T; Ca. Acryptolaria longitheca (Allman, 1877). K, T; Ca. Acryptolaria pulckella (Allman, 1888). K; EP. Eucryptolaria pinnata Fraser, 1938. C; Ca, EP. Filellum serpens (Hassall, 1852). T, NW; Ca, EP. Filellum serralum (Clarke, 1879). C; Ca. Lafoea coalescens Allman, 1877. K. Lafoea dumosa (Fleming, 1828). T; Ca, EP. Lafoea gracillima (Alder, 1857). T; Ca, EP. Lafoea tenellula Allman, 1877. K; Ca. Lafoea venusta Allman, 1877. K, T, C; Ca. Lictorella convallaria (Allman), 1877. K, T, C; Ca, EP. Zygophylax rigida (Fraser, 1940). Y. Family SYNTHECIDAE Synthecium ? gracile Fraser, 1937. T; Ca, EP. Synthecium ? marginatum (Allman, 1877). K; Ca. Synthecium ? nanum Fraser, 1943. T; Ca. 'Synthecium ? rectum Nutting, 1904. C. Synthecium tubithecum (Allman), 1877. K, T, C; Ca. Family SERTULARIDAE Diphasia digitalis (Busk, 1852). K, T, C; Ca. Pasya quadridentata (Ellis and Solander, 1786) . T, NW; Ca, EP. Sertularella amphorifera Allman, 1877. K, T, C, Y; Ca, EP. Sertularella areyi Nutting, 1904. C. Sertularella conica Allman, 1877. K, T, NW, NE; Ca, EP. Sertularella dislans (Allman, 1877). T, C, Y; Ca. Sertularella formosa Fewkes, 1881. C; Ca, EP. Sertularella gayi (Lamouroux, 1821). K, C, Y, NW; Ca. Sertularella humilis Fraser, 1943. K. Sertularella megastoma Nutting, 1904. Y; Ca. Sertularella pinnigera Hartlaub, 1900. K; Ca. Sertularella quadrala Nutting, 1904. C; Ca. Sertularella sieboldi Kirchenpauer, 1884. C. Sertularella speciosa Congdon, 1907. K; Ca. Sertularella tenella (Alder, 1856). C; Ca, EP. Serlularia cornicina (McCrady, 1858). K?, Y; Ca, EP. Serlularia dalmasi (Versluys, 1899). T, NW, NE; Ca, EP. Serlularia exigua Allman, 1877. K; Ca, EP. Serlularia flowersi Nutting, 1904. C. Serlularia inftata (Versluys, 1899). K, T, NW, NE; Ca, EP. Serlularia mayeri Nutting, 1904. K, T; Ca, EP. Serlularia pourtalesi Nutting, 1904. K, T; Ca, EP. Sertularia stookeyi Nutting, 1904. K; EP. Serlularia lumida Allman, 1877. T. Sertularia turbinata (Lamouroux, 1816). K, T; Ca. Thuiaria crisioides (Lamouroux, 1824). K; Ca, EP. Thuiaria tropica (Stechow, 1926). T. Idiella pristis (Lamouroux, 1816). K, T; Ca. GULF OF MEXICO 271 Family PLUMULARIDAE Aglaopheiiia allmani Nutting, 1900. K, T; Ca. Aglaophenia aperla Nutting, 1900. C, NE. Aglaophenia hiconuila Nutting, 1900. C. Aglaophenia ? constricta Allman, 1877. K. Aglaophenia cristifrons Nutting, 1900. C, NW. ? Aglaophenia dichotoma Kirclienpauer, 1872. NE. Aglaophenia duhia Nutting, 1900. K, T, C; Ca, EP. Aglaophenia elongata Menegliini, 1845. NE. Aglaophenia flowersi Nutting, 1900. K; Ca. Aglaophenia late-carinata Allman, 1877. K, T, NW; Ca. Aglaophenia longiramosa Eraser, 1945. NE. Aglaophenia lophocarpa Allman, 1877. K, T, C, NE; Ca, EP. Aglaophenia ? mercatoris Leloup, 1937. NE. Aglaophenia perpusilla Allman, 1877. K, T, NW; Ca. Aglaophenia raridentala Eraser, 1944. K. Aglaophenia rhynchocarpa Allman, 1877. K, T, C; Ca. Aglaophenia rigida Allman, 1877. K, NW; Ca, EP. Aglaophenia Iridentata Versluys, 1899. K, T; Ca. Aglaophenoides mamniiUala (Nutting, 1900). T. Aglaophenopsis hirsuia Fewkes, 1881. K. Antennella gracilis Allman, 1877. K, C; Ca, EP. Antennella quadriaiirita Ritchie, 1909. K, C. Antennella secundaria (Gmelin, 1788). T; Ca. Antennopsis distans Nutting, 1900. C. Antennopsis hippuris Allman, 1877. K. Antennopsis longicnrna Nutting, 1900. C. Antennopsis nigra Nutting, 1900. C. Antennularia simplex Allman, 1877. K, C. Cladocarpns carinatus Nutting, 1900. T. Cladocarpus dolicholheca Allman, 1877. K, T. Cladocarpus flexilis Verrill, 1885. NE. Cladocarpus flexuosus Nutting, 1900. NE. Cladocarpus longipinna Eraser, 1945. NE. Cladocarpus ohliquus Nutting, 1900. C. Cladocarpus paradisea Allman, 1877. K. Cladocarpus sigma (Allman, 1877). K, C. Cladocarpus tenuis Clarke, 1879. T; Ca. Cladocarpus ventricosus Allman, 1877. K. Diplopteron longipinna Nutting, 1900. K. Diplopieron quadricorne Nutting, 1900. C; Ca. Halicornaria sinuosa Eraser, 1925. K, NE. Halicornaria speciosa Allman, 1877. K; Ca. Halopteris carinala Allman, 1877. K, T; Ca. Lytocarpus clarkei Nutting, 1900. C, Y; Ca. Lytocarpus grandis (Clarke, 1879). K; Ca. Lytocarpus philippinus (Kirchenpauer, 1872). K, T; Ca, EP. Monostaechas quadridens (McCradv, 1858). K, T, Y; NW, NE; Ca, EP. Plumularia atlenuata Allman, 1877. K; Ca, EP. Pluntularia clarkei Nutting, 1900. C. Plumularia diaphana (Heller, 1868). K, T, NW; Ca, EP. Plumularia filicula Allman, 1877. K; EP. Plumularia floridana Nutting, 1900. K, T, NW; EP. Plumularia geminata Allman, 1877. K; Ca. Plumularia inermis Nutting, 1900. T; Ca, EP. Plumularia macrolheca Allman, 1877. C. Plumularia margaretta (Nutting, 1900). K, T; Ca, EP. Plumularia megalocephala .\llrnan, 1877. K, C; Ca, EP. Plumularia paucinoda Nutting, 1900. C. Plumularia setacea (Ellis, 1755). R, T, NW, NE; EP. Plumularia setaceoides Bale, 1882. K, Ca. Plumularia strictocarpa Pictet, 1893. K; Ca. Schizotricha dichotoma Nutting, 1900. K. Schizolricha tenella (Verrill, 1874). NW?; Ca, EP. Thecocarpus bispinosus (Allman, 1877). K. Thecocarpus distans (Allman, 1877). K, T. SUMMARY A total of 183 species of hydroids, 31 athecate and 152 thecate, are known from the Gulf of Mexico, mostly from the Tortugas and the Florida Keys. Medusae are not considered. The Gulf and the Caribbean have 95 species in common, but 61 Caribbean species are unknown in the Gulf. Seventy Gulf species also occur in the eastern tropical Pacific, including 18 not yet known from the Caribbean. Taxonomic difficulties, as well as inadequate collecting, make hydroid geography an unsatisfactory subject, and it is uncertain how far the apparently common "American" distribution pattern should be taken seriously. Wliat is espe- cially interesting is the occurrence in the Gulf of a significant number of boreal species, some of them seemingly disjunct in the northwestern Gulf. LITERATURE CITED Allman, G. J. 1877. Report on the Hydroida collected during the exploration of the Gulf Stream by L. F. de Pourtales, Assistant United States Coast Survey. Mem. Mus. Comp. Zool., Harvard College 5 (2): 1-66, 34 pis. Clarke, S. F. 1879. Report on the Hydroida collected during the exploration of the Gulf Stream and Gulf of Mexico by Alexander Agassiz, 1877-78. Bull. Mus. Comp. Zool., Harvard College 5 (10): 239-252, 5 pis. Deevey, E. S. 1950. Hydroids from Louisiana and Texas, with remarks on the Pleistocene biogeography of the western Gulf of Mexico. Ecology 31: 334-367. Ekman, Sve.\. 1934. Indo-Westpazifik und Atlanto-Ostpazifik, eine tiergeographische Studie. Zoogeographica 2: 320- 374. 1935. Tiergeographie des Meeres. Leipzig: Akade- mische Verlagsges. xii + 542 pp. 272 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Fewkes, J. W. 1881. Reports on the results of drodging under the supervision of Alexander Agassiz ... by the U. S. Coast Survey steamer Blake. XI. Report on the Acalephae. Bull. Mus. Comp. Zool., Harvard Col- lege, 8: 127-140. Phaser, C. McL. 1943. Distribution records of some hydroids in the col- lection of the Museum of Comparative Zoology at Harvard College, with description of new genera and new species. Proc. New England Zool. Club 22: 75- 98, pis. 15-20. 1944. Hydroids of the Atlantic coast of North America. 451 pp., 94 pis. Toronto: Univ. Toronto Press. 1945. Notes on some recently collected hydroids in the United States National Museum, with descriptions of three new species. Jour. Washington Acad. Sci. 35: 21-23. 1948. Hydroids of the Allan Hancock Pacific Expedi- tions since March, 1938. Allan Hancock Pacific Exped. 4 (5) : 179-334. Jaderholm, Elof. 1896. Ueber aussereuropaische Hydroiden des Zoologi- schen Museums der Universitat Upsala. K. Svensk. Vet.-Akad., Handl., Bihang, 21, Aft. IV, No. 6: 1-20. 1903. Aussereuropaische Hydroiden im schwedischen Reichsmuseum. Ark. Zool. 1: 259-312. 1920. On some exotic hydroids in the Swedish Zoological State Museum. Ark. Zool. 13 (3): 1-11. Leloup, Eugene. 1935. Hydraires calyptoblastiques des Indes Occiden- tales. Mem. Mus. Roy. d'Hist. Nat. Belg., ser. 2, fasc. 2, 73 pp. 1937. Rfeultats scientifiques des croisieres du Navire- Ecole Beige Mercalor, Vol. 1, No. VI. Hydroidea, Siphonophora, Ceriantharia. Mem. Mus. Roy. d'Hist. Nat. Belg., ser. 2, fasc. 9: 91-127. Mayer, A. G. 1910. Medusae of the world. Carnegie Inst. Washing- ton Pub. 109, 3 vols. NtTTTING, C. C. 1900. American hydroids. Part I. The Plumularidae. Smithsonian Inst., U. S. Nat. Mus., Spec. Bull., 142 pp., 34 pis. 1904. American hydroids, Part II. The Sertularidae. Smithsonian Inst., U. S. Nat. Mus., Spec. Bull., 151 pp., 41 pis. 1915. American hydroids. Part III. The Campanulari- dae and the Bonneviellidae. Smithsonian Inst., U. S. Nat. Mus., Spec. Bull., 118 pp., 27 pis. Perkins, H. F. 1908. Notes on medusae of the western Atlantic. Carne- gie Inst. Washington, Pap. Tortugas Lab. 1 (8) : 133-156, pis. 1-4. De PoURTALfcs, L. F. 1869. Contributions to the fauna of the Gulf Stream at great depths. Bull. Mus. Comp. Zool., Harvard College, 1 (6): 103-120. ScHucHERT, Charles. 1935. Historical geology of the Antillean-Caribbean region or the lands bordering the Gulf of Mexico and the Caribbean Sea. John Wiley, New York: 811pp. Stechow, E. 1912. Hydroiden der Munchener Zoologischen Staats- sammlung. Zool. Jahrb., Abt. Syst. 32: 333-378, pis. 12, 13. 1919. Zur Kenntnis der Hydroidenfauna des Mittel- meeres, Amerikas, und anderer Gebiete. I. Zool. Jahrb., Abt. Syst. 42: 1-172. 1923. Zur Keiintnis der Hydroidenfauna des Mittel- meeres, Amerikas, und anderer Gebiete. II. Zool. Jahrb., Abt. Syst. 47: 1-270. 1926. Einigs neue Hydroiden aus verschledenen Meeres- gebieten. Zool. Anz. 68: 96-108. Wallace, W. S. 1909. A collection of hydroids made at the Tortugas, during May, June, and July, 1908. Carnegie Inst. Washington Yearbook 7 (1908): 136-138. HYDROMEDUSAE OF THE GULF OF MEXICO By Mary Sears, Woods Hole Oceanographic Institution So few plankton collections have been made in the Gulf of Mexico and so few of these have been studied by hydromedusae specialists that it is necessary to rely almost entirely on Mayer's (1900, 1904, 1910) reports from the Tortugas. It is to be noted that most names listed in Mayer's first (1900) paper were reduced to the synonomy of other species in his monograph of 1910. Sub- sequent writers, expecially Bigelow (1913, 1918, 1919, 1938, 1940), Kramp (1919, 1920, 1926, 1930, 1932, 1933, 1939, 1942, 1947, 1948), and Ranson (1936) have also made certain revisions resulting in a slight reduction in the number of species originally enumerated by Mayer in his monograph (1910). In comparing the resulting list with that in the section on the hydroids it is striking to note that few species (i. e., Turritopsis nutricula McCrady, Zanclea costata Gegenbaur, Bougain- villia carolinensis McCrady, Pennaria tiarella McCrady, and Cladonema mayeri Perkins among the Anthomedusae) appear on both lists. In large part this is due to the fact that many hydroids do not liberate free-swimming medusae, and that many medusae have very much reduced hydroid stages. Indeed, in many instances the hydroid stage is completely unknown, if it exists. Insofar as it has been possible to determine only about 70 species have been recorded (30 Anthomedusae, 34 Leptomedusae, 5 Trachy- medusae, and 3 Narcomedusae) from the Gulf of Mexico region. Some of these, not already mentioned above, are good species also known elsewhere: Corymorpha nutans Hartlaub; Hybocodon forbesii Mayer; Sarsia mirabilis L. Agassiz; Eclopleura minerva Mayer; Dipurena ophiogaster Haeckel; Zancleopsis dichotoma Mayer; Amphinema dinema P6ron et LeSueur; A. octaedra Haeckel; A. rugosa Mayer; A. lurrida Mayer; Merga violacea Agassiz and Mayer; Podocoryne minula Trinci; Lymnorea alexandri Mayer; Bougainvillia niobe Mayer; Kollikerina elegans Mayer; Proboscidactyla ornala Mc- Crady, among the Anthomedusae; Laodicea cruiciala Forsk&l; Phalidium discoida Mayer; Phialucium carolinae Mayer; Exicheilola ventricularis McCrady; E. duodecimalis A. Agassiz; Eutima mira McCrady; E. elephas Haeckel; Euiimalphes coerulea L. Agassiz; Phortis pyramidalis L. Agassiz; P. lactea Mayer; Aequorea floridana Mayer, among the Leptomedusae; Geryonia proboscidalis Forsk&l; Liriope telraphylla Chamisso and Eysenhardt; Olindias phosphorica tenuis Fewkes; Rhopalonema velatum Gegen- baur, among the Trachy medusae; and Aeginura grimaldii Maas; Cunoctantha octonaria McCrady; Solmundella bitentaculata Quoy and Gaimard (using the names which appear to conform with present usage). A goodly number of species, however, do not ap- pear to have been subject to critical review in recent years, so that it is uncertain whether they are good species or merely synonyms of others. Hence, they are not listed at this time. LITERATURE CITED Bigelow, H. B. 1913. Medusae and Siphonophorae collected by the U. S. Fisheries steamer Albatross in the northwestern Pacific, 1906. Proc. U. S. Nat. Mus. 44 (1946): 1-119, 6 pis., 2 text figs. 1918. Some Medusae and Siphonophorae from the west- ern Atlantic. Bull. Mus. Comp. Zool., Harvard Col- lege, 62 (8) : 365-442, 8 pis. 1919. Hydromedusae, siphonophores, and ctenophores of the Albatross Philippine Expedition. Bull. 100, U. S. Nat. Mus. 1 (5) : 279-362, pis. 39-43. 1938. Plankton of the Bermuda Oceanographic Expedi- tions. VIII. Medusae taken during the years 1929 and 1930. Zoologica, New York, 23 (2) : 99-189, 23 text figs. 1940. Eastern Pacific Expeditions of the New York Zoological Society XX. Medusae of the Templeton Crocker and Eastern Pacific Zaca Expeditions, 1936- 1938. Zoologica, New York, 25 (3): 281-321, text figs. 1-20. Khamp, P. L. 1919. Medusae. Pt. 1. Leptomedusae. Danish In- golf Expedition 5 (8): 111 pp., 5 pis., 14 charts, 17, text figs. 1920. Anthomedusae and Leptomedusae. Rept. Sci. Res. Michael Sars Exped., 1910, Zool. 3 (2): 13 pp., 1 pi., 6 text figs. 273 274 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Kramp, p. L. — Continued 1926. Medusae. Pt. 2. Anthomedusae. Danish In- golf Exped. 5 (10): 102 pp., 2 pis. 1930. Hydromedusae collected in the southwestern part of the North Sea and in the eastern part of the channel in 1903-1914. Mem. Mas. Roy. d'Hist. Nat. Belgi- que No. 45: 55 pp. 1932. A revision of the medusae belonging to the family Mitrocomidae. Vidensk. Medd. Dansk. Naturh. Forening 92: 305-383, pi. 10, 52 text figs. 1933. Craspedote Medusen. Teil 3. Leptomedusen. Nordisches Plankton Zool. 6, Coelenterata: 541-602, text figs. 1-68. 1939. Occasional notes on Coelenterata. III. A. On the systematical position of the Williidae. B. Genus Koellikerina nom. nov. C. Tentacles on the manu- brium of Sarsia. D. On two new species of hydroids from the Kara Sea. Vidensk. Medd. Dansk. Naturh. Forening 103: 503-516, 9 text figs. 1942. The Godthaab Expedition 1920. Medusae. Medd. om Gr0nland 81 (1): 1-168, 27 maps, 11 text Kramp, P. L. — Continued 1947. Medusae. Pt. III. Trachylina and Scyphozoa with geographical remarks on all the medusae of the northern Atlantic. Danish Ingolf Exped. 5 (14): 66 pp., 6 pis., 20 text figs. 1948. Trachymedusae and Narcomedusae from the Michael Sars North Atlantic Deep-Sea Expedition with additions on Anthomedusae, Leptomedusae, and Scyphomedusae. Rept. Sci. Res. Michael Sars North Atlantic Deep-Sea Exped., 1910, 5 (1): 23 pp., 1 pi., 7 maps. Mater, A. G. 1900. Some medusae from the Tortugas, Florida. Bull Mus. Comp. Zool., Harvard College, 37 (2): 82 pp., 44 pis. 1904. Medusae of the Bahamas. Mus. Brooklyn Inst. Arts and Sci., Mem. Nat. Sci. 1 (1): 1-33, 7 pis. 1910. Medusae of the world. Carnegie Inst Washing- ton Pub. 109, 3 vols., 735 pp., 76 pis., 428 text figs. Ranson, G. 1936. Meduses provenant des campagnes du Prince Albert 1 " de Monaco. R6s. Camp. Sci., Monaco 92: 248 pp., 2 pis. SIPHONOPHORES IN THE GULF OF MEXICO By Mary Sears, Woods Hole Oceanographic Institution The siphonophores most often recorded from the Gulf of Mexico are the two large conspicuous species with floats above the surface of the water, Physalia physalis L. and Veltlla velella L. Pos- sibly Porpita umbella O. F. MuUer ' should also be included with these (Whitten, Rosene, and Hedgpeth, 1950). As early as 1886, Fewkes wi'ote, "I have many new localities for this medusa [i. e., Velella] in the Gulf of Mexico." The Atlantis in the winter of 1951 sailed through swarms of Physalia together with large quantities of Velella some miles in extent (Stetson, personal communication) out in the Gulf off the northwest coast of Florida, and newspapers give frequent account of the contamination of west Florida bathing beaches. The smaller, more common species, however, have scarcely been noted in the Gulf except at a few localities around its periphery, chief!}' at the Tortugas (Mayer 1900) and in adjacent bodies of water such as the Straits of Florida (Bigelow 1918) , the Caribbean (Fewkes 1889), and the Gulf Stream proper (Bigelow 1918; Fewkes, 1882, 1886, 1889). These records are indicative that about 25 of the better known species in all probability occur in the Gulf of Mexico proper: Abyla carina Haeckel; Abi/Iopsis Idragona Otto; A. eschscholtzii Huxley; Agalma okeni Eschscholtz; Amphicaryon acaule Chun; Bassia bassensis Quoy and Gaimard; Ceratocymba sagiitata Quoy and Gaimard; Chelophyes appendiculata Eschscholtz; Diphyes bojani Chun; Diphyes dispar Chamisso and Ey.senhardt; Enneagonum hyalinum Quoy and Gaimard; Eudoxoides spiralis Bigelow; Galetta auslralis Quoy and Gaimard; Hippopodius hip- popus Forsk&l; Lensia fowleri Bigelow; Rhizophysa eysenhardti Gegenbaur; Rhizophysa filijormis Forsk&l; Sphaeronecles truncata Will; Stephanomia rubra Vogt; Sulculeotaria monoica Chun; Suicide- olaria quadrideniala Quoy and Gaimard; Voglia glabra Bigelow; Voglia pentacantha Kolliker (as they are now named). ^ ' See Bigelow and Sears (1937J for use of this name. 2 References which are especially helpful and readily accessible in establish- ing the accepted names are: Bigelow. 1911a, 1911b, 1913, 1918, 1919, 1931; Bigelow and Sears, 1937; Sears, in press; Totton, 1932, 1941, in press. 2595.'H O— 54- 19 In the Gulf of Mexico, one might expect to find possibly 50 other species of Calycophorae, which have been taken in the tropical Atlantic and per- haps as many more among the Physophorae, Rhizophysaliae, and Chondrophorae combined. Most of these species have been taken at one time or another in the tropical Atlantic and might be expected to be carried by the currents into the Gulf of Mexico. The depth of the sill at the entrances to the Caribbean and Gulf of Mexico is sufficiently great to permit entry of even the species that live at considerable depths, a factor which, for example, apparently prevents some siphonophore species from entering the Mediter- ranean (Bigelow and Sears 1937). In short, it would not be surprising to find any one of the 140 or more siphonophore species, now known, in the Gulf of Mexico. LITERATURE CITED Bigelow. H. B. 1911a. Biscayan plankton collected during a cruise of H. M. S. Research, 1900. XIII. The Siphonophora. Trans. Linn. Soc, Londoli, Ser. 2, Zool., 10 (10): 337-358, pi. 28. 1911b. Reports on the scientific results of the Expedi- tion to the Eastern Tropical Pacific, 1901-1905. XXIII. The Siphonophorae. Mem. Mus. Comp. Zool., Harvard College, 38: 171-402, 32 pis. 1913. Medusae and Siphonophorae collected by the U. S. Fisheries Steamer Albatross in tlie Northwestern Pacific, 1906. Proc. U. S. Nat. Mus. 44: 1-119, pis. 1-6. 1918. Some Medusae and Siphonophorae from the Western Atlantic. Bull. Mus. Comp. Zool., Harvard College, 62 (8): 365-442, 8 pis. 1919. Hydromedusae, siphonophores, and ctenophores of the Albatross Philippine Expedition. Bull. U. S. Nat. Mus., No. 100, 1 (5): 279-362, pis. 39-43. 1931. Siphonophorae from the Arcturus Oceanographic Expedition. Zoologica, N. Y., 8 (11): 525-592, text figs. 185-220. Bigelow, H. B., and M. Sears. 1937. H. 2. Siphonophorae. Rept. Danish Ocean. Exped., 1908-10, to the Mediterranean and adjacent seas, Biol. 2: 1-144, 83 text figs. 275 276 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Fewkes, J. W. 1882. No. 7. Explorations of the surface fauna of the Gulf Stream, under the auspices of the U. S. Coast Survey ... 1. Notes on acalephs from the Tortugas, with a description of new genera and species. Bull. Mus. Comp. Zool., Harvard College, 9: 251-289, 7 pis. 1886. Report on the medusae collected by U. S. Fish Commission Steamer Albatross in the region of the Gulf Stream in 1883-84. Ann. Rept. Comm. Fish and Fish, for 1884: 927-980, 10 pis. 1889. Report on the medusae collected by the U. S. Fish Commission Steamer Albatross in the region of the Gulf Stream in 1885 and 1886. Ann. Rept. Coram. Fish and Fish, for 1886: 513-536, 1 pi. Mater, A. G. 1900. Some medusae from the Tortugas, Florida. Bull. Mus. Comp. Zool., Harvard College, 37 (2): 82 pp., 44 pis. Sears, Mary 1953. Notes on siphonophores. 2. A revision of the Abylinae. Bull. Mus. Comp. Zool., Harvard College, 109 (1): 1-119, 29 text figs. TOTTON, A. K. 1932. Siphonophora. Brit. Mus. (N. H.) Great Bar- rier Reef Expedition 1928-29, Sci. Repts. 4 (10): 317- 374, 36 text figs. 1941. New species of the siphonophoran genus Lensia Totton, 1932. Ann. Mag. Nat. Hist.^ Ser. 11. 8: 145-168, 29 text figs. Whitten, H. L., Rosbne, H. F., and Hedgpeth, J. W. 1950. The invertebrate fauna of Texas coast jetties: a preliminary survey. Pub. Inst. Mar. Sci. 1 (2): 53-86, 1 pi., 4 text figs. SCYPHOZOA By Joel W. Hedgpeth, Scripps Institution of Oceanography With the exception of Mayer's studies at Tor- tugas nearly 50 years ago there has been no serious attempt to study the medusae of the Gulf of Mexico. While there are a few scattered records of medusae along the coast, little is available on the occurrence of jellyfish in the pelagic regions of the Gulf or of the deep-water forms. There are a few large medusae which charac- teristically occur in the neritic waters of the Gulf of Mexico from Florida to the Rio Grande. Fore- most of these is Stomolophus meleagris, the cab- bagehead. This rhizostome often occurs in vast numbers in lower bays and around passes at the end of the summer. Such swarms were observed at Port Aransas, Texas, on August 4-5, 1947, and September 20, 1948. The latter swarm was esti- mated to be drifting through the channel on an incoming tide at the rate of 2 million an hour. The bobbing white domes of these jellyfish seemed to be packed almost solidly across the 800-yard width of the channel. Occasionally, Stomolophus is caught by the ton in shrimp trawls, and there has been some speculation about a possible eco- nomic use for these animals. Mayer mentions several oriental species which are pickled, but such a specialty delicatessen use would hardly cat into the unwanted surplus. With the possible excep- tion of a few hypersensitive individuals, Stomolo- phus is not a dangerous species to bathers and may be handled with impunity. It is a fine animal for physiological experimentation. Another rhizostome, Rhopilema verrilli, may be more common than suspected. Specimens have been taken from Mobile Bay, and one was col- lected at Port Aransas. This is a much larger medusa than Stomolophus, and Mayer suggested that it is a southern form which occasionally extends as far north as Long Island. Burkenroad (personal communication) considers it common in Chandeleur Sound. One of the most common jellj^sh in the bays, especially during the summer months, is Dacty- lometra quinquecirrha, a semaeostome medusa" This medusa may cause a mild rash or unpleasant sting,' but severe cases of jell3^sh poisoning by this species are rarely reported (Hedgpeth 1945). An occasional denizen of bay waters is the moon jelly, Aurellia aurita. While it is usually more a frequenter of the lower bays and gulf waters, it at times outnumbers Dactylometra in the bays. Another large Medusa in Gulf waters is the lion's mane, Cyanaea capillata var. versicolor. Mayer gives the southern limit of this variety as Cape Canaveral, Florida, and did not find it at Tortugas. R. O. Christenson, of Alabama Poly- technic Institute, identified this medusa from Mobile Bay, on February 20, 1938. A large, reddish, striped medusa was observed on an out- going tide at Port Aransas, Texas, on March 16, 1948, which appeared to be this species. It is of interest to note that both these records are to- ward the end of the Gulf coast winter. Burken- road (personal communication) considers it com- mon in Louisiana waters. According to Mayer, some 75 species of medu- sae occur at Tortugas. Nine of these are scypho- zoans, and the great majority are hydromedusae, more properly considered under hydroids (p. 267). There are probably more species to be found in the Gulf. Following is a list of the Scyphomedu- sae known to occur in the Gulf of Mexico, prin- cipally at Tortugas. This list includes the 9 species discussed by Mayer and the 2 species whose occurrence in the Gulf was not known to him: ^ Carybdaea aurifera Mayer, pp. 510, fig. 328. A rare form taken only twice at Tortugas. I The Portuguele Man-of-War, Physalia, is more dangerous and probably causes some distress to unwary bathers every season. This siphonophore is often washed up on the outer beaches in great numbers, and its stranded pneumatophores are heard popping under the wheels by motorists driving on the beach. Two smaller siphonophores, Porpila linneana and Velella velieia, are often stranded on the beach, ' All page and figure numbers given after the name of the species refer to Mayer's publication. 1910. 277 278 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Nausithoe punctata KoUiker, pp. 554-556, pi. 60, figs. 4-5, text fig. 352.' This medusae is noteworthy for the peculiar, branched scyphistoma which lives commensally in sponges. Found in all tropical and warm seas. Linuche unguiculala Eschscholtz, pp. 558-559, pi. 59, figs. 1-10. A West Indian species. Forms vast swarms in spring in the Florida-Bahama region according to Mayer. Dartylonetra quinquecirrha L. Agassiz, pp. 585-588, pis. 62-64a, text figs. 370-372. Widely distributed from New England to the tropics; possibly also Pacific. Abundant in Tampa Bay in August (p. 586). Cyanaea capillata var. versicolor L. Agassiz, pp. 600-601, pi. 65, figs. 1-2. Western Atlantic and Gulf, south of Cape Hatteras. Aurellia aurita Lamarck, pp. 623-626, pi. 67, figs. 1-4, fig. 4; 68. In east American waters, common from Greenland to West Indies. World wide. Cassiopea xamachana R. P. Bigelow, pp. 641-646, pis. 69-72. C. frondosa Lamarck. Pp. 647-648, pi. 69 and 72. These interesting medusae are the subject of several papers in the Tortugas Laboratory series. The first is known from Tortugas and Jamaica; the second is more widely distributed throughout the West Indies. Rhopilema verrillii (Fewkes), pp. 707-709, pi. 7, fig. 1, text fig. 424. From New Haven to Port Aransas, but not (?) Tortugas. Slomolophus meleagris L. Agassiz, pp. 710-711, pis. 75-76. Abundant along southern Atlantic and Gulf of Mexico (not north of Chesapeake Bay), and West Indies. Also on Pacific side of Isthmus, and north at least to San Diego. LITERATURE CITED Hedgpeth, Joel W. 1945. Reexamination of the adventure of the Lion's Mane. Sci. Monthly 60: 227-232. Mayer, A. G. 1910. Medusae of the world. Carnegie Inst. Washing- ton Pub. 109, 3: 499-735. I See footnote 2, page 277. ANTHOZOA: ALCYONARIA By Frederick M. Bayer, U. S. National Museum The Alcyonaria of the Gulf of Mexico ^ are little known. No systematic work treats them in detail, and the preparation of such an account must await more extensive collections from the entire region. Even papers mentioning occasional Gulf species are few and, with perhaps two or three exceptions, deal only witli those found in the extreme southeastern part (i. e., the Straits of Florida, the Florida Keys, and Dry Tortugas). Notable among these is the series of reports by Bielschowsky (1929), Kukenthal (1916), Kunze (1916), Riess (1929), and Toeplitz (1929), pub- lished imder the general title, Die Gorgonarien Westindiens in the supplement volumes 11 and 16 of the Zoologische Jahrbucher. Professor A. E. Verrill (1864. 1869, 1883) early recorded the presence, mostly in the lower Gulf, of a few alcyo- narians ; and some later work by Stiasny, especially the two Siboga supplements (1935, 1937), adds to the list of species known from the Tortugas area. Explorations in the Gulf of Mexico have not been extensive, and collections are correspondingly inadequate. The exploratory vessels, Albatross, Fish Hawk, Pelican, Blake, Bibb, and Bache have all made dredge hauls in the Gulf, but the records of only the last three have been published, these in the classic monograph on the alcyonarians of the western Atlantic by Dr. Elisabeth Deichmann (1936). Exploratory trawling is currently being carried on by the U. S. Fish and Wildlife Service M/V Oregon, but very few alcyonarians have so far been seen. Present knowledge of the alcyonarians of the Gulf of Mexico is summarized in the accompanying table (table 1), which also indicates the distribu- tion outside of the Gulf of the species concerned. Table 1. — Geographical dislribulion of alcyonarians known from the Gulf of Mexico A. Arctic to Cape Cod. B. C. Cod to C. Hatteras. C. C. Hatteras to C. Canaveral. D. Bermuda. E. C. Carnaveral to Sombrero Key. a. Low water to 10 fathoms. b. 10-99 fathoms. 1. Bayer 1949. 2. Bayer 19.52. 3. Bielschowsky 1929. 4. Carv 1906. 5. Cary 1918. 6. Deichmann 1936. 7. Oordon 1925. 8. Heilprin 1890. 9. Kiikenthal 191fi. F Sombrero Key to Tortugas Bank; Straits of I. Galveston to Veracruz. Florida; N. W. coast of Cuba. .1. Vera Cruz to C. Catoche U. C. Sable to Apalachee Bay. K. Central Qulf Basin. u Apalachee Bay to Galveston. L. West Indies. c. 100-499 fathoms. M. Caribbean Sea. d. 500-999 fathoms. N. Brazil. 10, Kukenthal 1919. e. 1000 fathoms and deeper. 11. Kiikenthal 1924. X. No deptll given. 12. Kunze 1916. 20. Stiasnv 1941c. 13. Moser 1921. 21. Stiasnv 1941d. 14. de Pourtales 1868. 22. Thomson 1927. 15. Riess 1929. 23. Toeplitz 1929. IB. Stiasny 19.35. 24. Verrill 1864. 17. Stiasny 1937. 25. Verrill 1869. IS. Stiasny 19413. 26. Verrill 1883. 19. stiasny 1941b. 27. Verrill 1907. Species Arctic to Sombrero Key Gulf of Mexico West Indies to Brazil A B c D E F H I J K L M N Order TELESTACEA telestidae Tclestoflavula, 2,6 b b b c c c b b Telesto sanguinea, 2, 6 b b b Obdeb ALCYONACEA alcyoniidae N'idalia occidentalis, 2, 6 b c b NEFHTHYIDAE Euncphthya nigra, 2, 6, 14.. Neospongodes agassizii, 6 b, c b, Neospongodes portoricensis, 2, 6 • Published with the permission of the Secretary of the Smithsonian Insti- tution. ' For the purposes of this summary, the geographical boundaries of the Gulf of Mexico will be taken to include, in addition to the usual land masses. a line drawn from Cape Sable, Fla., due south to the coast of Cuba, and another from Cape San Antonio, Cuba, to Cape Catoche, Yucatdn. This delimitation is purely arbitrary and does not coincide with faunistic bound- aries 279 280 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 1. — Geographical distribution of alcyonarians known from the Gulf of Mexico — Continued Species Arctic to Sombrero Key Oulf of Mexico West Indies to Brazil A B C D E F G H I J K L M N Order OORQONACEA Suborder Scleraxonia briareidae Briareum asbestinum, 5, 6 b a b b a b c c c b b a a b b a a DiodoRorgia nodulifera, 2, 6 b b Iciligorgia schramrai, 2, 6, 18 .__ Solenopodium polyanthes, 6, 17 , b d Suborder Holaxonia A CANTHOnORnnDAE b,c b,c b,c b,c muriceidae Bebryce grandis, 2, 6 , b c a X a,b c X a Muricea penduJa, 2, 6, 24 . a b b a c b c c a a b Placogorgia mirabilis, 2, 6 Placogorgia tenuis, 6, 26. . b,c b,c d b Scleraeis petrosa, 6 _-___ . _-, Swiftia casta, 2, 6, 14, 26 .. c b b b c b c b Swiftia koreni, 2, 6 d b b b c c b,c a a a a a a a Thesea citrma, 6. Thesea grandiflora, 6._ b Thesea plana, 2, 6. b b Thesea soUtaria, 6, 14 c b b,e a a a a c X plexauridae Eunicea asperula, 12 . _ Eunicea calyculata. 12 a a a a a a a a a a a a a a a a Plexaura dubia, 2, 11 a a a a Plexaura flexuosa, 6, 8. 16, 20, 27 a a a a X a Plexaurella dichotoma, 11, 12, 16, 27 a a a a X Plexaurella dubrovskyi, 16 X a a OOROOmiDAE X a a a a a a a b a a X a A. acerosa elastica, 3, 21 b a a,b a a a a ? a b b b a Eugorpia stheno, 2 b a a a a a b b a Leptogorgia hebes, 2, 6, 25 a b b a Leptogorgia setacea, 6, 20 a a a a a a b,c b,c b,o Pterogorgia anceps 2, 5 8 11 24 a a, b a a a c c b b c c d X b a a a c Scirpearia barbadensis 6 b b Scirpearia grandis 6 23 27 b CHRTSOr.ORr.IIDAE Chrysogorgia dcsbonni 6 26 b,c c,d c c Trichogorgia viola, 6. _. GULF OF MEXICO Table 1. — Geographical distribution of alcyonarians known from the Gulf of Mexico — Continued 281 Species Arctic to Sombrero Key OuK of Mexico West Indies to Brazil A B C D E F a H I J K L M N Suborder Holaxonia— Continued PRIHNOIDAE c c c c d d b,c c Caligorgia verticillata, 6, 14 b . c Plumarella pourtalesii, 6, 26 c b X d c w Thouareila aurea, 6 , . _ ThouareUa go^si, 6 c c,d ISIDIDAE Annnpllft phnrnpA, 9, R, 9fi ^ d a a c c c,d Order PENNATULACEA RBNILLTOAE ReniUa rpniformis, 4, 24 . __. X a a c,d a yUNICUUNIDAE c c d e PROTOPTILIDAE Protoptilum sp. cf. thonisoni, 2 c UMBEllULIDAE e d,e e e d e Umbellula lindahlii, 6 X a This table has been compiled from the literature and from collections in the U. S. National Museum, including unpublished records from the Albatross, Fish Hawk, and Pelican expeditions. Published locality records within the Gulf of Mexico as defined above have been located for 72 species; records of only 9 species from Gulf localities exclu- sive of the lower Florida Keys and Tortugas have been found. Another 19 species have been added by records m the collections of the U. S. National Museum, bringing the total number of species to 91. These species represent 18 families in 4 of the 6 known orders. Although little is known of the physiology of the alcyonarians, it is clear that bottom condi- tions, temperature, salinity, available oxygen, and sedimentation play important parts in limit- ing their distribution. Limits of tolerance are apparently quite narrow but not equally so for all factors. A solid substrate providing satisfactory conditions for the attachment of larvae is almost universally required among all alcyonarian groups excepting the pennatulids. A very few gorgona- cean species are able to live unattached, and a number, especially of the families Chrysogorgi- idae and Isididae, can adapt themselves to live on either hard or soft bottom. The few gorgonian species which have been investigated in regard to temperature tolerance (L. R. Cary, Papers from the Dept. of Marine Biology, Carnegie Institu- tion of Washington, v. 12, No. 9, 1918) can with- stand from 5° to 9° C. (approximately) above the average maximum surface temperature of the area (at the Tortugas, about 29° C), but it is unlikely that colonies would establish or thrive outside of a rather limited temperature range. In the absence of experimental evidence, it is impossible to state the limits of the salinity and oxygen variation which the alcyonarians can tolerate. A few species can live in situations where the salinity is occasionallj' somewhat reduced, but most, including the West Indian reef-dwelling forms, are never found where appreciable dilution regularly occurs. Certain species are limited to outer reef situations, and oxygen may be the critical factor in such cases. As a rule, alcy- onarians are not found in continuously muddy waters, but some can tolerate very muddy con- ditions for short periods. The reef areas of the Tortugas and lower Florida Keys support a typically West Indian gorgonian assemblage. The predominant families are the 282 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Plexauridae and the Gorgoniidae; while not all of the known West Indian members of these families have been recorded from this area, most are to be expected. This community does not extend northward undiminished for any appreciable dis- tance, although a few of the hardier species range about halfway up the Florida west coast. The scarcity of suitable reef-like situations along this coast seems to account in part for their reduction in numbers, and temperature may be of equal importance in limiting the northward distribution of shallow-water gorgonians. Antillogorgia acer- osa, A. americana, and Pterogorgia anceps are characteristic reef forms which extend some dis- tance up the west coast of Florida, and they probably occur wherever there is solid bottom suitable for attachment and permanent support. The predominant West Indian genera of reef- dwelling gorgonians, Plexaurella, Eunicea, Antil- logorgia, Gorgonia, Pterogorgia, and Phyllogorgia, are restricted to the warm western Atlantic, while a few, such as Pacifigorgia and Muricea, are most numerous on the Pacific coast of the middle Americas, and at least one, Leptogorgia, is found also in the eastern Atlantic, the Mediter- ranean, east Africa, and the East Indies. The alcyonarian fauna of the lower west coast of Florida is thus a decimated West Indian as- semblage. To the northward it merges with and soon, perhaps near Tampa, is replaced by a dis- tinctly temperate fauna the predominant gorgo- nians of which are Leptogorgia virgulata and L. setacea (both of which are referable (Bayer 1952) to Verrill's genus Eugorgia), and Muricea pendula. These species are especially abundant along the coast of the Carolinas and south perhaps to north- ern Florida; L. virgulata extends north to New York in moderately deep water, but all three seem to be lacking from the lower east coast of Florida. The short-stemmed sea pansy, Renilla mulleri, is common in the northern Gulf and extends south- ward to Brazil ; it likewise occurs along the Pacific Coast from Central America to Chile. It has not been recorded from the Atlantic coast of North America where the only species appears to be Renilla reniformis, the common long-stemmed sea pansy. The latter species occurs also in the Gulf of Mexico with a variety extending south to the Straits of Magellan and another in California. The shallow-water gorgonian fauna of the northern Gulf of Mexico is clearly identical with but discontinuous from that of the Carolina coast. This interrupted distribution pattern has been pointed out by Deevey (Ecology, vol. 31, No. 3, pp. 334-367, 1950) for some hydroids and other invertebrates and is described for fishes in this volume (Rivas, p. 503). Deevey suggests that re- duced temperature during periods of glaciation permitted continuity of the cool-water fauna around south Florida, but it would seem fully as plausible that this continuity existed when Flor- ida was submerged and that subsequent dispersal around the peninsula has been prevented by a thermal barrier. Since apparently favorable situ- ations exist all along the east coast of Florida, the southward dispersal of these discontinuously distributed gorgonians is probably not limited by bottom conditions but by some other environ- mental factor of which temperature seems to be the most likely. In any event, it can hardly be doubted that the present-day distribution re- flects a former continuity of the Gulf and Caro- lina faunas, but a satisfactory explanation must await the study of some group with an extensive fossil record. Although its southern limit is not known, the shallow water temperate assemblage is probably present along most of the Texas coast, somewhere along the coast of Mexico mingling with and giving way to the hardier elements of the West Indian fauna which encroach upon it from the south. At least one gorgonacean, Leptogorgia setacea, ex- tends as far south as the Guianas and Trinidad. The presence of actively growing coral reefs at Veracruz and along the coast of Yucatan has long been recognized, but the composition of their fauna is little known. Heilprin (1890) reports only one species of gorgonian from the Veracruz reefs and remarks that the vast gorgonian sea gardens so tj'pical of the Bermudas are lacking. The single species that he records, Plexaura flexuosa, belongs to the West Indian fauna, and it seems hkely that other West Indian species occur there. Heilprin notes further that Xiphi- gorgia (now Pterogorgia) anceps was found at Progreso, Yucatdn, another record indicative of the West Indian fauna. The occurrence of the West Indian reef species Gorgonia flabellum on GULF OF MEXICO 283 the Texas coast (one unpublished record in the U. S. National Museum) needs to be verified. In the deeper waters (10-500 fathoms) of the southeastern Gulf, practically all of the alcyo- narians are West Indian species belonging to genera of wide distribution. The Gorgonellidae, Chrysogorgiidac, Primnoidae, and Muriceidae re- place in predominance the plexaurids and gor- goniids of very shallow water. Most of the species are widespread throughout the Antilles and prob- ably also in the Caribbean. From the occurrence of such characteristic forms as Bebryce grandis and Scleracis guadalupensis in the extreme north- ern Gulf, it is probably safe to assume that a good proportion of the West Indian species are present throughout the Gulf of Mexico wherever bottom conditions permit. There is -no evidence as to the composition of the alcyonarian fauna of this bathymetric range in the western part of the Gulf, and intensive collecting should be done in that region to clarify the distribution patterns of the West Indian species as they enter the Gulf of Mexico. The limited deep-sea dredging which has been done in the Gulf of Mexico has resulted in very few alcyonarian records. The isidid gorgonian, AcaneUa eburnea, which was taken in depths ranging from less than 200 to above 950 fathoms in the Gulf of Mexico, is also known from the northwestern Atlantic, the West Indies and Car- ibbean, the coast of Brazil, and the eastern Atlan- tic, always at considerable depths. Beyond the 1,000-fathom contour, three pennatulid species have been dredged: Umbellula giintheri, U. lin- dahlii, and Funiculina quad ran gularis , all of which also occur at extreme depths in the northern and eastern Atlantic. There seems to be no truly endemic element in the alcyonarian fauna of the Gulf of Mexico. The strictly shallow-water forms of the northern half are also the predominant species along the Carolina-Georgia coast, while those of the south- ern part are typically West Indian. The species of moderate depths throughout the Gulf are West Indian, and a northern element does not appear to be present. Finally, the character- istically deep-sea forms thus far known from the Gulf are of wide distribution at similar depths throughout the Atlantic and are possibly even cosmopolitan. BIBLIOGRAPHY Bayer, Frederick M. 1949. Chalcogorgiinac, a new subfamily of Chrysogor- giidae (Coelenterata: Alcyoiiaria), and a description of Chalcogorgia petlucida, new genus and new species, from the Straits of P'lorida. Jour. Washington Acad. Sci. 39 (7) : 237-240, 1 fig. 1952. New western Atlantic records of octocorals (Coelenterata: Anthozoa), with descriptions of three new species. Jour. Washington Acad. Sci. 42 (6) : BlELSCHOWSKY, EvA. 1929. Die Gorgonarien Westindiens. Kap. 6: Die Familie Gorgoniidae. Zool. Jahrb. Supp. 16 (1): 63-234, figs. 1-40, pis. 2-5. i Gary, Lewis R. 1906. A contribution to the fauna of the coast of Loui- siana. Gulf Biol. Sta., Cameron, La. (Louisiana State Bd. of Agric. and Immig.), Bull. 6: 50-59. 1918. The Gorgonaceae as a factor in the formation of coral reefs. Carnegie Inst. Washington Pub. 213: 341-362, pis. 100-105. Deichmann, Elisabeth. 1936. The Alcyonaria of the western part of the At- lantic Ocean. Mem. Mus. Comp. Zool. Harvard 53: 1-317, pis. 1-37. Gordon, Isabella. 1925. Gorgonids from Curapao Island. Het Koninklijk Zool. Genootschab Leyden. Bijdragen tot de Dier- kunde 24: 15-24, pis. 3-4. Heilprin, Angelo. 1890. The corals and coral reefs of the western waters of the Gulf of Mexico. Proc. Acad. Nat. Sci. Phila- delphia 1890, 42: 303-316. Kukenthal, Willy. 1916. Die Gorgonarien Westindiens. Kap. 1, Die Scleraxonier; Kap. 2, Uber den Venu.sfacher; Kap. 3, Die Gattung Xiphigorgia H. M. Edw. Zool. Jahrb. Supp. 11 (4): 444-503, 26 figs., pi. 23. 1919. Gorgonaria. Wissenscahftliche Ergebnisse der deutschen Tiefsee-Exped. auf dem Dampfer Valdivia 1898-99, 13 (2): 1-946, 318 figs., pis. 30-89. 1924. Gorgonaria. Das Tierreich 47: xxviii + 478, 209 figs. Berlin u. Leipzig. Kunze, G. 1916. Die Gorgonarien Westindiens. Kap. 4. — Die Gattung Eunicea Lamouroux; Kap. 5. — Die Gattung Plexaurella. Zool. Jahrb. Supp. 11 (4): 505-586, 55 figs., pis. 24-28. MosER, Johannes. 1921. Ergebnisse einer Revision der Gattung Plexaura Lamouroux. Zool. .\nzeiger 53 (5/6): 110-118. PoURTALis, L. F., DE 1863-1869. Contributions to the fauna of the Gulf Stream at great depths (2d series). Bull. Mus. Comp. Zool. Harvard College 1 (6): 10.3-120, 1867; 1 (7): 121-142, 1868. RiEss, Marqot. 1929. Die Gorgonarien Westindiens. Kap. 8. — Die Familie Muriceidae. Zool. Jahrb. Supp. 16 (2): 377-420, 4 figs., pi. 8. 284 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Stiasny, Gustav. 1935. Die Gorgonacea der iSifcopa-Expedition. Supple- ment 1, Revision der Plexauridae. Siboga-Exped. Monog. 13b': vi+106, 27 figs., pis. 1-7. 1937. Die Gorgonacea der St'iogo-Expedition. Supple- ment 2, Revision der Scleraxonia mit Ausschluss der Melitodidae und Coralliidae. Siboga-Exped. Monog. 13b8: vi+138, 38 figs., pis. 1-8. 1941a. Studien iiber Alcyonaria und Gorgonaria, II. Zool. Anzeiger 134(3/4)": 53-71, 8 figs. 1941b. Studien iiber Alcyonaria und Gorgonaria, III. Zool. Anzeiger 134(11/12): 254-268, 11 figs. 1941c. Studien iiber Alcyonaria und Gorgonaria, IV. Zool. Anzeiger 135(1/2): 13-25, 10 figs. 194 Id. Gorgonaria von Venezuela (Inseln Blanquilla und Los Frailes). Arch. N^erl. de Zool. 6 (1): 101- 116, figs. 1-4, pis. 1-2. Thomson, J. Arthur. 1927. Alcyonaires provenant des campagnes scientifiques du Prince Albert I"' de Monaco. R6s. Camp. Scient. Albert de Monaco 73: 1-77, pis. 1-6. ToEPLiTZ, Charlotte M. 1929. Die Gorgonarien Westindiens. Kap. 7. — Die Familie Gorgonellidae, zugleich eine Revision. Zool. Jahrb. Supp. 16 (2): 235-376, 26 figs., pis. 6-7. Verrill, Addison Emery. 1864. List of the polyps and corals sent by the Museum of Comparative Zoology to other institutions in ex- change, with annotations. Bull. Mus. Comp. Zool., Harvard College 1 (3) : 29-60. 1869. Critical remarks on the halcyonoid polyps with descriptions of new species in the museum of Yale College, No. 4. Am. Jour. Sei. (2) 48: 419-429. 1883. Report on the Anthozoa, and on some additional species dredged by the Blake in 1877-79, and by the U. S. Fish Commission steamer Fish Hawk in 1880-82. Bull. Mus. Comp. Zool., Harvard College 11 (1): 1-72, pis. 1-8. 1904-1907. The Bermuda Islands. Part 5.— Charac- teristic life of the Bermuda coral reefs. Trans. Con- necticut Acad. Sci. 12: 160-304, 28 pis.; index and errata, pp. 311-316. ANTHOZOA: THE ANEMONES By Joel W. Hedgpeth, Scripps Institution of Oceanography, University of California There is as yet no systematic study of the anemones of the entire Gulf of Mexico incUidinf; the Tortugas region. The papers of McMurrich, especially 1889, and Watzl (1922) on Bahamas actinians, together with Duerden's (1902) report on Porto Rican species, are useful aids to the study of the Tortugas anemone fauna which apparently is about the same as that of the Bahamas. For the Gulf of Mexico proper there is only the rpcent paper by Carlgren and Hedgpeth (1952) on species from Texas and Louisiana. The collections reported in this work indicate a mixture of tropical, West Indian forms and species of the Midille Atlantic coast. Of particular interest is the finding of Aiptasiomorphia luciae at Port Aransas, adding yet another locality for that ubiquitous species. The accompanying table, (table 1), compiled principalh- from the literature, indicates the affinities of the common species found at Bahamas and Tortugas. This is sup- plemented by brief notes on some of the more interesting forms. Table 1. — Synopsis and known distribution of anemones in Bahamas, Tortugas, and the Gulf of Mexico ICompiled from the literature; synonymy (in parentheses), after Carlgren, 1949] Woods Hole Beau- fort Ber- muda Baha- mas West Indies Oulf of Mexico Depth Species Tortu- gas (or Keys) Loui- siana Texas Remarks Order CORALLIMORPHARIA COEALUMORPHIDAE Corynactis bahamensU Watzl X X X X X Shore RicoTdea fiorida Duch, et Mich (•) (•) . do.- (Meter arithua floriim) AcrmoDisciDAE Paradiscosoma neglecta (Duch. ct Mich.) . do •St. Thomas, Haiti, Ja- Paradiscosoma cartgreni (Watzl) do maica. (Rhodactis carlgteni) Rhodactis sancti thomae (Duch. et Mich.). X (•) .. do (AcHnothriz sancti thomae) Order ACTINIARIA; Suborder Endocoelantheae Halcukiidae Halcurias pUaiui McMurrich X X 100 fathoms Shore Suborder Nynantheae Alicudae Lebrunia danae (Duch. et Mich.) X X X X X X (•) (•) •Curafao, St. Thomas, (i. 7uglecta:Cradacti3 variabilis) Actiniidae Adinia bermudensis (McMurrich) Jamaica. (Diplactis bermudensis) Actinia grobbeni Wall] . . lAnemonia elegans Verrill X Anemonia sargassensis Hargitt X X X X X Pelagic, on sar- gassum. Bunodosoma caver nata (Bosc) X x' X Leipsiceras pollens (McMurrich) -f-lOO fathoms {Bolocera pollens) Antkopleura krebsi (Duch. et Mich.) (•) X Anthopleura varioarmata Watzl X X X do Condylactis gigantea (Weiland)... X X X (•) X (C. passi flora) Bunodactis slelloides (McMmrich) . .. (Autadinia stelloides) 285 286 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 1. — Synopsis and known distribution of anemones in Bahamas, Tortugas, and the Gulf of Mexico — Continued Woods Hole Beau- tort Ber- muda Baha- mas West Indies Gulf of Mexico Depth Species Tortu- gas (or Keys) Loui- siana Texas Remarks Order CORALLIMORPHARIA— Con. AcTiNiiDAE— Continued X X (•) X X X X St. Thomas. {Asteractis flosculifera: Oulactis fascicu- lata McM.) (Asteractis eipansa Duerden) MlNYADIDAE X X X Pelagic --- Stoichactiidae Stoichactis helianthus (Ellis) X X X X (Discosoma anemone) Phymanthidae ACTINOSTOLIDAE Paranihus rapiformis (LeSueur) {Ammophilactis rapiformis) Subtr. Acontiarla I30PHELLIDAK New Haven X X X Shallow water + 10faths.7 X iPltelUa roseni) HoRMATHnDAE X X X X X X X 100-250 faths Shore-10/20fatlis.. lOU faths Calliactis tricolor (Le Sueur) X Stephenauge spongicola (Verrill) (Sagartia spongicola) AlPTASIIDAE X X 9 X X X X X X X X (•) X Curasao, Jamaica. X {Aiptnsia anmdata: Carlgrenidta TO- brutfa Walzl) Heteradis lucida (Duch. et Mich.) (.Aiptasia lucida) AIPTA3I0M0RPHIDAE X X X X X (•) St. Thomas, Jamaica. X {Sagartia, Diadumene, luciae) DiADUMENIDAE Shore _ Shallow water to about 10 faths. 10-14 faths. {Sagartia Itucolena) Order CERIANTHIARIA 7 Ceria-nthTOmorphe brasiliensi^ (Carlgren).. Brazil, New Mexico NOTE : The following species, so far known only from the northwestern Gulf of Mexico, have recently been described by Carlgren and Htdgpoth (1952) : Andwakiidae, Andwakia isabellae; Actiniidae, Bunodactis texaensis: Aiptasiomorphidae. Aiptasimorpha texnensis; Sagartiidae?, Botryon tuberculatas; Zoan- tharia, Zoanthidae, Palyttioa texaensis. Of all the animals living in the sea the anemones are at the same time among the most beautiful and most difficult to study.. A sound basis for the study of anemones is a detailed series of notes on the living animals including color sketches or photographs, measurements, and descriptions of the nematocj'sts, and a set of well-prepared slides of various parts of each species. Each marine laboratory or station should compile a set of color photographs, camera lucida drawings of the nematocysts (under oil immersion) making up the cnidom, and serial sections for each species in its fauna. A collection of huddled lumps of coelenterate flesh is almost useless to all but the GULF OF MEXICO 287 most thorough-going spociaHst in this group, aiul in the absence of satisfactory material our knowl- edge of Gulf coast actinians will remain in its present fragmentary state. NOTES ON COMMON SPECIES Lubrunia danae (Duchassalng and Michelotti). This anemone is conspicuous for the large, branched outgrowths ("pseudotentacles" or "fronds") at the top of the column just below the tentacles. The animal is brownish and lives in hollows m coral rock. It is common at Tortugas and was described from there by Hargitt (1911) as Cradactis variabilis. McClendon (1911), in a paper on habits of several invertebrates, provides a color plate. Anemonia sargassensis Hargitt. A well characterized anemone both in habit and appearance. Originally described from sargassum drifting mto Woods Hole, it is found on that plant as it drifts ashore along the Texas coast and is recorded from Beaufort by Field (1949). It is a small, rather squat, velvet-brown species.' The tentacles may be tinted green and are occasionally branched (fig. 60). Bunodosotna cavernata (Bosc). The common jetty form of the Texas coast, especially at Port Aransas and Port Isabel. Cary (1906) found it common on the Cameron jetties. It was originally described from the Carolina coast and is a characteristic member of the Beaufort fauna. It is a muddy to dull brown colored anem- one with pearl gray vesicles on the column, with reddish to brownish or bluish tentacles, but usually witii a red stripe on the back of the larger tentacles (fig. 60). Some specimens are entirely cherry red. The West Indian B. granuUfera is considered to be a synonym of this species (Carlgren 1952). Anthopleura krebsi (Duchassalng and Michelotti). Previously known from St. Thomas and Ja- maica, a colony of small individuals occurs on the Port Isabel jetties. The column and tentacles are white, with rows of bright red verrucae which are larger and more regular toward the top of the column (fig. 60). ' M. D, Biirkenroad contends (in litteris) that there is another common species on Oulf Sargassum, smaller than Anemonia, and reproducing com- monly by longitudinal fission. Carlgren (in litteris) thinks it possible that this may be a Buvdeopsis. This problem cannot be clarified until the anemones of the Atlantic Sargassum are critically studied. Bunodactis texaensis Carlgren and Hedgpeth. A conspicuous gray anemone, sii])erficially resembling Bunodosoma cavernata, but with ver- rucae instead of vesicles on the column and a pattern of darker gray or greenish to light brown splotches on the disc (see color plate, Calgren and Hedgpeth). It occurs on the jetties at Calveston and offshore near Port Aransas. Minyas olivacea (LeSueur.) A pelagic antillean species which occasionally drifts ashore on the coasts of Texas and Louisiana, sometimes in considerable numbers. The animal is an olive brown color, with the tentacles ap- parently reduced to knoblike processes. The animal remains at the surface by means of a float in the pedal disc. According to observations of M. D. Burkeiu-oad, Minyas will shed its float in an aquarium, but does not produce a new one under these conditions. It may be that the mature Minyas (as yet unknown) is a sessile form. Condylactis gigantea (Weinland). The "passion flower" anemone is common at Tortugas, the Bahamas, Miami, and various places in the West Indies. The color of the column varies from bright scarlet to brownish, the tentacles are brownish or paler than the column and usually tipped with scarlet. Stoichactis helianthus (Ellis). The "sun ilower" anemone is a characteristic West Indian species common in the Bahamas and at Tortugas. It is easily identified by the broad, incompletely retractile disc with its large number of short, stubby tentacles. The disc is greenish or with green patches, and the peristome is usually bright yellow. The tentacles are greenish to yellow. Paranthus rapiformis (LeSueur). A characteristic member of the shallow water bottom assemblage along the Texas coast. Cary found it washed ashore along the Cameron beach. It is found off Beaufort and along the coast north- ward to New Haven. Although this species has a moderately well developed basal disc, it is a buiTowing form. The column is whitish, the disc green with faint salmon markings (fig. 60). Speci- mens brought on deck in a trawl or dredge con- tract to a spherical shape resembling peeled onions. Calliactis tricolor (LeSueur). Common on the shells of the gastropod Rehderia off the southern Atlantic coast and sometimes 288 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Figure 60. — Anemones from the northern coast of the Gulf of Mexico. GULF OF MEXICO 289 Calliactis tricolor iof] Hejoatus ephehticus ) Aiptasiomorpha. luciae Mptasia pallida. Figure 61. — Anemones from the northern coast of the Gulf of Mexico. abundant on hermit crab shells and oxystome crab carapaces (fig. 61) in comparatively shallow water along the Texas coast. Occasionally, a specimen is found living in shallow water attached to some immobile substrate. The column is whitish, cream colored or brownish with darker vertical stripes and darker brown spots marking the cinclides at the base of the column; the acontia are bright orange; the tentacles are pinkish to red with darker bandings. The directives are often more deeply colored than the other tentacles. This is a common West Indian species. Aiptasia pallida (Verrill). According to Gary, this species (fig. 61) was common on the jetties at Cameron in 1906; I have not seen it on Texas jetties but found it 290 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE commonly on oysters near Port Isabel. It is usually rich brown with darker stripes. The tentacles may be solid brown, or whitish. The brown color is due mainly to zooxanthellae. Off- shore, in about 10 fathoms, there is a pale powder blue phase found in old Pinna shells. The species is known from the Carolina coast, especially at Beaufort, where it occurs in large colonies (Carl- gren 1952). Bartholomea annulata (LeSueur). The tentacles appear to be ringed because of the annular swellings or incomplete bands of nemato- cyst batteries. The column is whitish at the base, darkening to brown near the top. The tentacles are brown. The species is found in Bermuda, Bahamas, and the West Indies, and a specimen has been collected at Port Isabel, Texas. Aiptasiomorpha luciae (Verrill). Easily identifiable by its olive green column with orange vertical stripes (when not m a color- less phase), this little anemone (fig. 60) is almost cosmopolitan. It was first observed by Verrill at Woods Hole but may have spread originally from Japan. It is found on the Pacific coast of North America, at various places in Europe, and now from the Texas coast (Port Aransas). Aiptasimorpha texaensis Carlgren and Hedgpeth. A small, salmon pink to whitish species locally common in bays of Texas and Louisiana. It has been recorded from salinities as low as 9 parts per thousand, and seems to be an estuarine species. It is usually found on oysters and piling. Ceriantheomorphe brasiliensis Carlgren. This cerianthid has been collected near the coast of Texas and northeastern Mexico, and was originally described from San Sebastian, Brazil. Gary reported a colony of cerianthids from the Chandeleur Islands, which may be this species, or possibly Cerianthiopsis americanus, which occurs at Beaufort. Tliesc large burrowing anemones are difficult to collect, and no specimen from the Chandeleurs has come to notice. BIBLIOGRAPHY Carlgren, Oskar 1949. A survey of the Ptychodactiaria, Corallimorpharia and Actiniaria. K. sven ka vetensk. Handl. (4), 1 (1), 121 pp., 4 pis. 1952. Actinaria from North America. Arkiv for Zool., 3 (30) : 373-390, 10 figs. , and Hedgpeth, Joel W. 19.52. Actinaria, Zoantharia and Ceriantharia from shallow water in the northwestern Gulf of Mexico. Pub. Inst. Mar. Sci. Texas, 2 (2): 143-172, 9 figs., 4 color plates. Gary, L. R. 1906. A contribution to the fauna of the coast of Louisi- ana. Gulf Biologic Sta. Bull. 6: 50-59. (p. 51). GoNKLiN, Edwin G. 1908. Two peculiar actinian larvae from Tortugas, Florida. Papers Tortugas Lab. 2: 171-186, 4 pis., 5 figs. DUERDEN, J. E. 1902. Report on the actinians of Porto Rico. U. S. Fish. Comm. Bull. 20 (2): 321-374, 12 pis. Field, Louise Randall 1949. Sea anemones and corals of Beaufort, North Caro- lina. Duke Univ. Marine Sta. Bull. 5 : 1-39., 94 figs. [Caution: The corrections made by Carlgren (1952) and Carlgren and Hedgpeth (1952) concern only the anemone section.] Haroitt, Charles W. 1911. Cradactis variabilis: an apparently new Tortugas actinian. Papers Tortugas Lab. 3: 51-53, 1 pi. McClendon, J. F. 1911. On adaptations in structure and habits of some marine animals of Tortugas, Florida. Papers Tortu- gas Lab. 3: 55-62, 2 pis. McMuRRICH, J. Playkair 1889. The actiniaria of the Bahama Islands, W. I. Jour. Morph. 3 (1), 80 pp., 4 pis. 1896. Notes on some actinians from the Bahama Islands, collected by the late Dr. J. I. Northrup. Annals New York Acad. Sci. 9: 181-194. 1898. Report on the actiniaria collected by the Bahama Expedition of the State University of Iowa, 4: 225- 249, 3 pis. Watzl, Otto 1922. Die Actiniarien der Bahamainseln. Auf Grund der Sammlung des Hern Dr. N. Ros6n (1908-09). Arkiv for Zool. 14 (24), 89 pp., 1 pi., 10 text figs. GULF OF MEXICO MADREPORARIA' By F. G. Walton Smith, Marine Laboratory, University of Miami By reason of the ^reat differenee in llieir normal habitat corals fall into two very distinct groups. The hermatypic or reef corals are usually, but not always, largo and massive or branching in form. They are usually associated with other corals in building considerable masses of living coral reef. The deep-water or ahermatypic corals, on the other hand, are usually small and solitarj' though sometimes branching in form. Hermatypic corals grow in water up to 50 fath- oms in depth but are only active in reef building in depths to 25 fathoms. Most reef growth occurs in less than 15 fathoms. Ahermatypic corals are found mostly in deeper water from the edge of the continental slope to the neighborhood of 3,000 fathoms. The majority live between 90 and 300 fathoms. The temperature range for reef corals is approximately 19° C. to 36° C. (63° F. to 97° F.) with an average minimum, however, of 22° C. (72° F.). Ahermatypic corals live best within a range from about 8° C. to 21° C. in the West Indian region. The distribution of reef corals in the Gulf of Mexico and the relation of the coral fauna of this area to those of neighboring areas is dependent upon the physiological requirements of corals. These have been studied in detail and are dis- cussed by Vaughan in a series of papers describing experiments carried out at Dry Tortugas. The average optimum salinity for reef corals is 36 parts per thousand, although a range of 27 to 40 parts per thousand may be tolerated. Expo- sure to air is also tolerated to a variable extent. Species with more porous skeletons are consider- ably more resistant to exposure. Strong light is essential to vigorous growth. This is apparently the result of the zooxanthellae which are normally present in the tissues of reef corals. Corals are carnivorous in habit. Reef corals do not, as a rule, withstand any great amount of sediment and are accordingly ' Contribution No. 106 from the Marine Laboratory, University of Miami. 259534 O— 5-I 20 found where vigorous water circulation exists Tiie branching corals grow more readily in com- paratively still water than do the massive types. A few species such as Porites furcata and Manicina areolata may be found on muddy bottoms. Growth rates of corals at Dry Tortugas have been measured by Vaughan. Non-porous species grew at an average rate of 9.0 mm. in diameter and 5.00 mm. in height per year. Porous species increased at an annual rate of 40 mm. in diameter and 25.0 mm. in height. Montastrea annularis, a massive type, showed an annual increment in weight of 54.8 percent, whereas, a branching coral, Acropora palmata, increased 194.9 percent in weight per annum. Both specimens were approxi- mately 100 grams at the beginning of the experi- ment. Growth of corals is greater at higher temperatures. Since temperatures in the Gulf of Mexico are generally close to the lower limit of the range, reef growth is accordingly slower than in the warmer seas. Larvae of species found in the Gulf of Mexico have a planktonic life of be- tween 1 and 3 weeks. Winter temperatures in the Gulf of Mexico are close to the lower limit for vigorous reef growth. There are therefore no strongly developed reefs except for those of the Dry Tortugas, the Florida Keys, and the Alacran and other reefs of the Campechc Bank. Less vigorous reef develop- ment is found at Veracruz and at a few other places within the warmer, more souther!}' waters of the Gulf (fig. 62). Scattered coral heads which fail to form true reef structures are found elsewhere in the Gulf of Mexico, particularly off the west coast of Florida. Because of the amount of sediment present, they are rarely found close inshore but usually at some distance from the coast in more than 5 fathoms of water. Scattered heads are also found in deeper water in a line running from south of New Orleans toward the Texas coast and in another line run- ning southward parallel to the Texas coast. Sur- 291 292 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 30°H Coral reefs GULF OF MEXICO JAmARY ISOTHERMS AND CORAL DISTRIBUTION Fig. 62 — January isotherms and distribution of corals in the Gulf of Mexico prisingly few published records exist regarding the presence of reef corals in the Gulf of Mexico. The Alacran reef, described by Agassiz (1878, 1888), the Veracruz reef, described by Heilprin (1890), and the Dry Tortugas and Florida Keys reefs, described by Agassiz (1888), Vaughan, and others complete the list. From these, and various unpublished sources, Joubin (1912) prepared a map of coral reefs of this area. Data concerning patches of scattered coral heads are also shown on the U. S. Hydrographic Office Bottom Sediment Charts 1125 BS and 1126 BS published in 1943. All available records to date are indicated m the accompanying chart which shows approximate locations only. Except for reefs of the Florida Keys an (^Vera- cruz, published accounts of Gulf reefs are insuffi- cient to give an adequate list of species. The fauna is nevertheless typically West Indian. Forty-two of the 51 species known to the West Indies have been recorded from Florida. Only 11 of these are reported from Veracruz (Heilprin 1890). The Caribbean reef fauna consists of about 26 genera and 51 species (table 1). The species listed here include a number which are undoubt- edly varieties or growth forms, such as Acropora ■prolifera and certain species of Porites. They are included here, however, since they are recognizably different, and such a list is convenient to field workers who are more concerned with accurate and speedy identification rather than the some- times debatable questions of taxonomy. For purposes of identification, the handbook of At- lantic reef corals by Smith (1948) is most useful since it contains complete keys and descriptions and is well illustrated. For an authoritative monograph on coral taxonomy, reference should be made to Vaughan and Wells (1943) who pro- vide an extensive bibliography. GULF OF MEXICO 293 Table 1. — Western Atlantic hermatypic species of corals (F indicates recorded trom Florida; V indicates recorded from Veracrui] SUBOJlDER ASTROCOENIIDA Family Astro coeniidae 1. .ls(rocof?iio pectinata Pourtales F 2. Slephanocoenitt michelini Edwards and Haime Seriatoporidae 3. Madrach decactis (Lyman) F ACROPOBIDAE 4. Acropora cenncoruis (Lamarck) - F 5. A. pal mat a (Lamarck) FV 6. A. prolifera (Lamarck) FV Suborder FUNOIIDA Agariciidae 7. Agaricia agaricites (Linnaeus) F 8. A.fragilh Dana - - F 9. A. tiobitis Verrill F Siderastreidae 10. Siderastrea radians (Pallas) _ F n. S. aiderta (Ellis and Solander) FV 12. S. atellala Verrill PORITiriAE 13. Poriles astreoides Lamarck. FV 14. P. branneri Rathbun... 15. P. divarkata LeSueur F 16. P.furcata Lamarck FV 17. P. poriles (Pallas) F 18. P. verrilli Rehberg Suborder FAVIIDA Favudae 19. Fnvia con/erta Verrill 20. F. /rajiim (Esper) F 21. F. gravida Verrill 22. F. kptophylla Verrill 23. Diploria divosa (Ellis and Solander). F 24. D. labyrinthifoTmis (Linnaeus) FV 25. D. singosa (Dana) FV 26. ColpophyUia amarauthus (Muller) F 27. C Nalans (Muller) F 28. Majiicina areotata (Linnaeus) F 29. M. mayori Wells F 30. Ctadocora arftuscula LeSueur FV 31. Solenastrea bournoni Edwards and Haime.. F 32. .S. hyades (Dana) F 33. Montastrea annularis (Ellis and Solander).. FV 34. A/, braziliana (Verrill).. .- 35. M. cavernosa (Linnaeus) FV Astranghdae 36. Astrangia solilarja (LeSueur) F OCt'LINIDAE 37. Oculina diffusa Lamarck __ FV 38. O. valenciennesi Edwards and Haime 39. O. varicosa LeSueur F Trochosmiuidae 40. Meandrina m«aHdri/w (Linnaeus) F 41. M. brasiliensis (Edwards and Haime) F 42. i)icAococ/)ja sfokf^ii Edwards and Haime F 43. Dendrogyra cylindrus Ehrenberg... F Mussidae 44. Mussismilia brasiliensis (Verrill) 45. .\/. harm (Verrill) 46. Mussa angulosa (Pallas).. F 47. Isophyllastrea rigida (Dana) F 48. A/j/ce/opAy/^ia Zamarcfcana (Edwards and Haime) F 49. Isophyllia sinuosa (Ellis and Solander) F 50. /. mutti/iora Verrill... F Suborder CARYOPHYLLIIDA Cartophtluidae 51. Eusmilia fastigiata (Pallas)... _ F The West Indian fauna includes species belong- ing to the Astrocoeniidae, Acroporidae, Agariciidae Siderastreidae, Poritidae, Faviidae, Oculinidae, Trochosmiliidac, Mussidae, and Caryopiiylliidae. None of the Fungiidae are represented and onlj' Madracis among the Seriatoporidae. Montipora, Atttreopora, Goniopora, and TrachyphyUia, all of which e.xist as fossils of the Caribbean iXeogene, are now absent. Genera known only to the West Indian fauna are Colpophyllia, Dendrogyra, Mean- drina, Aluasa, Mycetophyllia, Alanicina, Iso- phyllia, hophyllastrea, Eusmilia, Dichocoenia, and Agaricia. All of the West Indian genera occur on the Florida reefs. Their absence from other parts of the Gulf of Mexico must be ascribed to the existence of unfavorable temperature conditions which permit only the more hardy to live there since their presence on the Florida reefs, their known length of larval life, and the existence of favorable currents are sufficient for dispersal throughout the area. The ahermatypic corals are much less restricted by geographical boundaries than the hermatypic forms since the required conditions for their existence are widespread throughout the deeper waters of the ocean. The extent of distribution of any species depends partly upon the depth range inasmuch as the deeper the normal habitat, the greater the continuity of suitable environ- ments. On account of the generalized distribution of ahermatypic corals and the lack of adequate surveys of the greater part of the deeper waters of the Gulf of Mexico, it has seemed more useful to provide a list of ahermatypic corals known from the West Indies together with their tempera- ture and depth ranges. It is reasonable to expect that where the proper temperature, depth, and bottom conditions exist in the Gulf, the ap- propriate West Indian species may be found eventually. Existing accounts of Gulf of Mexico corals are mainly confined to those of Pourtales dealing with the deep-water fauna of the Florida Keys and between Dry Tortugas and the Campeche Bank. Descriptions of West Indian ahermatypic species are to be found in Agassiz (1888), Pourtales (1868, 1871, 1874, 1879, 1880), and Verrill (1883, 1908). A key to Western Atlantic genera is given in Smith (1948). A list of West Indian genera with temperature and depth ranges is given in table 2, compiled from data in Vaughan and Wells (1943). 294 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Table 2. — Ahermatypic genera of corals found in West Indies and Gulf of Mexico with approximate temperature and depth ranges Suborder ASTROCOENIIDA Seriatopobidae Madracis Milne Edwards and Haime 0-800 meters; 10-27° C. Suborder FUNOIIDA funoiidae Fungiacyathus Sars 60-6.000 meters; 1-21° C. Suborder FAVIIDA astranohdae A9tTangia Milne Edwards and Haime 0-110 meters; 8-28° C. Pkyllangia Milne Edwards and Haimo 0-90 meters; 23-28° C. Colangia Pourtales 0-580 meters; 6-27° C. OCULINIDAE Madrepora Linnaeus 60-1.400 meters; 4-16° C. Trochosmilhdae Dasmosmilia Pom'tales 100-!50 meters; 15-22° C. ANTHEMIPHYLLnDAE Antkemiphyllia Pourtales 170-730 meters; 8-17° C. Suborder CARYOPHTLLnDA Caryophyluidae Caryophyllia Lamarck O-2.800 meters; 2-27° C. Coenocyathus Milne Edwards and Haime 0-6,800 meters; 9-26° C. Cyatfioceras Moseley 70-1,100 meters; 3-27° C. Oiysmilia Duchassainp 75-300 meters; 10-20° C. Batliycyalhua Milne Edwards and Haime 56-14.5 meters; 10-13° C. TTOchocgathus Milne Edwards and Haime 15-1,500 meters; 4-27° C. Peponocyathus Gravier 100-1,100 meters; 7-21° C. Tethocyathus Kuhn 65-1,100 meters; 3-12° C. Dellocyathus Milne Edwards and Haime 1,5-4,300 meters; 4-28° C. Ceralotrochiis Milne Edwards and Haime 55-700 meters; 5-17° C. Sl€ phanocycthus Sequenza 360-2,200 meters; 3-12° C. Turbinolia Lamarck ss BatotTOchus Wells 180-570 meters; 11-21° C. Sphenolrochus Milne Edwards and Haime 22-275 meters; 9-26° C. Desmophyllum Ehrenberg 35-2.000 meters; 3-23° C. Parasmilia Milne Edwards and Haime 310-370 meters; 8-12° C. Coenosmilia Pourtales 145-450 meters; 13-23° C. l-inomocora Studer 90-820 meters; 4-17° C. Aslerosmilia Duncan 80-200 meters; 13-15° C. GUYNHDAE Ouynia Duncan 170-650 meters; 7-12° C. Stenocyathus Pourtales 80-820 meters; 7-14° C. Sctiizocyatlius Pourtales 100-1,500 meters; 10-18° C. Flabellidae Flabdium Lesson 0-3.200 meters; 2-27° C. lifonomyces Ehrenberg O-l.OOO meters; 6-28° C. OaTdineria Vaughan 70-600 meters; 6-18° C. Suborder DENDROPHYLIIDA DENDROPlIYLLnDAE Balanopkyllia Wood 0-1,10(1 meters; 7-28° C. Deitdrophyllia 10-500 meters; 11-27° C. Tuhastrea Lesson O-40O meters; 15-28° C. Trochopsammia Pourtales 500-1,500 meters; 5-7° C. Eiialtopsammia Michelotti 270-2,i»0 meters; 3-15° C. Tttecopsammia Pourtales 150-1,000 meters; 0-14° C, Bathypsammia vonMarenzeller 220-330 meters; insufficient data for temperature range. In shallow water the only ahermatypic corals are 3 or 4 species of Astrangia, Madracis, and Phyllangia. Most species are found in deeper water from the edge of the continental slope down- ward. A total of 84 species is known. According to Vaughan and Wells (1943), 13 of these are identical with living species of the northern and eastern Atlantic; 59 are endemic. Cosmopolitan species are Caryophyllia communis, Deltocyathus italicus, Desmophyllum cristagalli, Fungiacyathus symmetricus, Lophelia prolifera, Madrepora oculata, and Stephanocyathus nobilis. Table 3. — West Indian fossil genera found living elsewhere. SUBORDER ASTROCOENIIDA ASTROCOENIIDAE Stylocoen iella Yobe and Sugiyama Eocene-Oligocene; Recent-Japan, Mauritius Seriatoporidae SlyhptioTa Schweigger Eocene-Miocene; Recent-Red Sea, Indo-Pacific Suborder FUNGIIDA aoariciidae Pavona Lamarck Oligocene-Miocene; Recent-Indo-Pacific Leptoseris Milne Edwards and Haine Oligocene-Miocene, Recent-Indo-Pacific Thamnasteridae Psammocora Dana Miocene; Recent-Indo-Pacific Agathiphylliidae Diploastrea Matthai Cretaceous-Oligocene; Recent-Indo-Pacific PORITIDAE Qoniopora de Blainville Cretaceous-Miocene; Recent-Indo-Pacific Suborder FAVIIDA FAVnDAE Faiites Link Eocene-Miocene. Recent-Indo-Pacific, Red Sea Goniastrea Milne Edwards and Haine Eocene-OIigocene, Recent-Indo-Pacific, Red Sea BIBLIOGRAPHY Agas.=;iz, Alexander. 1888. Three cruises of the Blake. Houghton, Mifflin and Co., Boston and New York. Also: Bull. Mus. Comp. Zool , Harvard College, vols. 14 and 15. and De Pourtales, L. F. 1874. No. 8. The zoological results of the Hassler Expedition. I. Echini, crinoids, and corals. Mem. Mus. Comp. Zool., Harvard College, 4: 1-50, 15 cuts, 10 pis. GULF OF MEXICO 295 DUERDEN, J. E. 1902. West Indian niadreporarian polyps. Nat. Acad. Sci. Mem. (Washington), Vol. 7. FlELDEN, H. W. 1803. Transportation of coral by the Gulf Stream. The Zoologist (.3), 17: 352-353. Grecory, J. W. 1900. On the West Indian species of Madrepora. Auu. Mag. Nat. Hist. (7) 6: 20-31. Hkili'RIN, a. 1891. The corals and coral reef of the western waters of the Gulf of Mexico. Acad. Sci. Philadelphia Proc. 42: 303-316. JOUBIN, M. L. 1912. Carte des bancs et des recifs de Coranx (Madre- pores). Ann. de I'lnst. Oceanog. (Old Ser.), vol. 4, No. 2. De PouRT.\i,fes, L. F. 1863-69. Contributions to the fauna of the Gulf Stream at great depths. Bull. Mus. Conip. Zool., Harvard College, 1 (6): 103-120; 1 (7): 121-142. 1871. Deep-sea corals. lUus. cat. Bull. Mus. Comp. Zool., Harvard College, 4: 1-93. 1878. Reports on the results of dredging, ... in the Gulf of Mexico, by the U. S. Coast Survey Steamer Blake. II. Crinoids and corals. Bull. Mus. Comp. Zool., Harvard College, 5 (9): 197-216, 2 pis. 1880. Reports on the results of dredging, ... in the Gulf of Mexico, by the U. S. Coast Survey Steamer Blake. VI. Report on the corals and Antipatharia. Bull. Mus. Comp. Zool., Harvard College, 6: 95-120. 1883. Report on the Anthozoa and some additional species dredged by the Blake, 1873-79; and Fish Hawk, 1880-82. Bull. Mus. Comp. Zool., Harvard College, 11: 1-72. Smith, F. G. W. 1948. Atlantic reef corals. University of Miami Press. U. S. Navy Hydrographic Office and Division of War Research of the University of California. 1943. Bottom conditions. Bottom Sediment Chart 1943. H. O. Chart Nos. 1125 BS, 1126 BS. Vaiiohan, T. W. 1901. The stony corals of Puerto Rican waters. Bull U. S. Fish. Comm, 1900, 2- 289-320. 1911. Recent Madreporaria of southern Florida. Car- negie Inst. Washington Yearbook 9: 135-144. 1912. Madreporaria and marine bottom deposits of Florida. Carnegie Inst. Washington Yearbook 10: 147-156. 1913. Studies of the geology and of tlie Madreporaria of the Bahamas and of southern Florida. Carnegie Inst. Washington Yearbook 11: 153-162. 1914. The reef corals of southern Florida. Carnegie Inst. Washington Yearbook 12: 181-183. 1915a. Reef corals of the Bahamas and southern Florida. Carnegie Inst. Washington Yearbook 13: 222-226. 1915b. The geological significance of the growth-rate of the Floridian and Bahamian shoahvater corals. Washington Acad. Sci. Jour. 5: 591-600. 1916a. Results of investigations of the ecology of the Floridian and Bahamian shoal-water corals. Nat. Acad. Sci. Proc. 2: 95-100. 1916b. On recent Madreporaria of Florida, the Bahamas and the West Indies, and on collections from Murray Island, Australia. Carnegie Inst. Washington Year- book 14: 220-231. and Wells, John West. 1943. Revision of the suborders, families and genera of the Scleractinia. Geol. Soc. Am., Spec. Pap. 44. Verrill, a. E. 1902a. Variations and nomenclature of Bermudian, West Indian and Brazilian reef corals, with notes on various Indo-Pacific corals. Trans. Connecticut Acad. Arts & Sci. 11: 63-168. 1902b. Comparisons of the Bermudian, West Indian and Brazilian coral fauna. Trans. Conn. Acad. Arts & Sci. 11: 170-206. Wells, J. W. 1932. Study of the reef corals of the./Tortugas. Tortugas Lab. Ann. Rept., Carnegie Inst. Washington Year- book 31: 290-291. CTENOPHORES IN THE GULF OF MEXICO By Mary Sears, Woods Hole Oceanographic Institution Ctenophores are so fragile that they are not readily preserved or, if they are, certain diagnostic characters may become obscured. Thus, many records of their occurrence are somewhat un- certain. Equally uncertain are their names be- cause about 40 years ago four important papers appeared almost simultaneously (Bigelow 1912; Mayer 1912; Mortensen 1912; Moser 1912), and insofar as I can ascertain, nobody has reviewed the group critically since that time. It is probable, however, that the ctenophore fauna of the Gulf of Mexico is as well known as that of any neigh- boring area due to Mayer's (1900, 1912) and Fewkes' (1882) observations at the Tortugas. Nevertheless, only about a dozen species have been recorded with any certainty in the Gulf: Beroe ovata Bosc; Bolinojpsis vitrea L. Agassiz; Cestum veneris LeSueur; Eurhamphaea vexilligera Gegen- baur; Folio parellela Fol; Hormiphora hormiphora Gegenbaur; Leucothoe ochracea ' Mayer; Mne- miopsis mccradyi Mayer; Ocyropsis crystallina Rang; Ocyropsis maculata Rang; Tinerfe beehleri Mayer; Tinerfe lactea Mayer (using the names that appear to be acceptable today). This is a slight reduction in the number originally described because a number proved to be identical with species which had been described earlier. This list also includes most of the species that have ' Fewkes' (1882) record of Euchar.s muUicornit Quoy and Oaimard is con- dered by Mayer (1912, p. 35) to have been his new species, Leucothoe ochracea. been reported from neighboring parts of the Atlantic. Whether other species will be found in this area seems problematical. At any rate, although ctenophore species are more numerous in the Gulf, they apparently do not occur in dense swarms as is so characteristic of them in more northern waters. LITERATURE CITED Bigelow, H. B. 1912. Reports on the scientific results of the expedition to the eastern Tropical Pacific . . . XXVI. The ctenophores. Bull. Mus. Comp. Zool., Harvard College, 54 (12): 369-404, 2 pis. Fewkes, J. W. 1882. No. 7. Explorations of the surface fauna of the Gulf Stream, under the auspices of the U. S. Coast Survey by Alexander Agassiz. 1. Notes on acalephs from the Tortugas with a description of new genera and species. Bull. Mus. Comp. Zool., Harvard College, 9: 251-289, 7 pis. Mayeh, a. G. 1900. Some medusae from the Tortugas, Florida. Bull. Mus. Comp. Zool., Harvard College, 37 (2): 13-82, 44 pis. 1912. Ctenophores of the Atlantic coast of North Amer- ica. Carnegie Inst. Washington Pub. No. 162: 58 pp., 17 pis. Mortensen, Th. 1912. Ctenophora. Danish Ingol} Exped. 5 (2): 95 pp., 10 pis. Moser, F. 1912. Die Ctenophoren der Deutschen Sudpolar Ex- pedition 1901-1903. Deutsche Sudpolar Exped. 11 (Zool. 3): 117-192, 1 text fig., pis. 20-22. 297 CHAPTER IX FREE-LIVING FLATWORMS, NEMERTEANS, NEMATODES, TARDIGRADES, AND CHAETOGNATHS FREE-LIVING FLATWORMS (TURBELLARIA) OF THE GULF OF MEXICO By L. H. Hyman, American Museum of Natural History, New York City Very little information is available concerning the free-living flatworms of the Gulf of Mexico. Nothing at all has been done with the smaller and microscopic forms so that available material is limited to the polyclads (order Polycladida), and these have been studied only for the Gulf coast of the United States. To the writer's knowledge, no study has ever been made of the turbellarian fauna of the Mexican coast of the Gulf. The most extensive work on the littoral poly- clads of the Gulf of Mexico was done by Pearse (1938) during a stay in the region of Apalachicola Bay near the Alabama border of Florida. This publicatioa, unfortunately, contains some errors. The writer revised Pearse's work in 1940, and the names considered valid are those employed in that article. The most common littoral polyclads of the Gulf coast, distributed from Florida to Texas, are Sty- lochiLs frontalis Verrill {=Sty. inimicus Palombi, 1931), Stylochus ellipticus (Girard) 1850 {^Eusty- lochus meridionalis Pearse, 19S8) , Hoploplana in- quilina (Wheeler) 1894, and Gnesioeeros floridana (Pearse) 1938 {=Stylochoplana floridana Pearse, 1938) . Illustrations and descriptions of these spe- cies will be found in Pearse (1938) and Hyman (1939a, 1940). Stylochus frontalis is an oval, gray worm up to 50 mm. in length with nuchal tentacles and a band of eyes around the entire body margin. It lives in association with oysters on which it feeds and to which it may become quite destructive, hence being of some economic importance. The ecology of this polyclad has been treated at some length by Pearse and Wharton (1938). Stylochus ellipticus is an oval, gray, olive, cream, or brownish worm with nuchal tentacles and with marginal band of eyes extending only along the anterior part of the body. It, also, is often associated with oysters but is a general littoral species. Hoploplana inquilina is a small, oval, rather transparent worm that inhabits the mantle cavity of Busycon and Thais, possibly other gastropods. Pearse (1938) attempted to separate the form living in Thais from that in Busycon as a distinct species thaisana, but the writer failed to find any good grounds for this distinction and considers thaisana to be, at best, a geographical variant. Schechter (1943) found H. inquilina living in Thais floridana at Barataria Bay, La. Gnesioeeros floridana, a small, somewhat transparent worm of cuneate form, with nuchal tentacles but without any marginal eyes, is of common occurrence along the Gulf coast. A number of specimens of this species were sent to the writer by Joel W. Hedg- peth who collected them at Port Aransas, Tex., and many were recorded by Pearse from the west coast of Florida. In an Annotated List of the Fauna of the Grand Isle Region 1928-1941, pub- lished by the marine laboratory of Grand Isle, La., there is mentioned Gnesioeeros sargassicola lata; this is presumably a misidentification of Gnesio- eeros floridana. Other polyclads described by Pearse from the Apalachicola Bay, Fla., region are: Coronadena mutabilis (Verrill) 1873 { = Discocelis grisea Fe&rse, 1938); Latocestus whartoni (Pearse) 1938 ( = Oculo- plana whartoni Pearse, 1938); Stylochus oeuliferus (Girard) 1853 (=^Stylochu^ floridanus Pearse, 1938); Zygantroplana angusta (Verrill) 1893 {=Stylochoplana angusta (Verrill) Hyman, 1939); Euplana gracilis (Girard) 1850 {^Conjuguterus parvus Pearse, 1938); Enantia pellucida (Pearse) 1938 {^Acerotisa pellucida Pearse, 1938); a species of Thysanozoon possibly brocchi (Risso) 1818; Pseudoceros maculosus Pearse, 1938; Oli- goclado floridanus Pearse, 1938 { = Hymania pry- therchi Pearse and Littler, 1938); and Prosthiosto- mum lohatum Pearse, 1938. None of these species have been found in other parts of the Gulf of Mexico except Florida, but some of them extend up the Atlantic coast to the Carolinas. Descrip- tions and figures of these species are given in the articles by Pearse (1938), Pearse and Littler 301 302 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE (1938), and Hyman (1939, 1940). In addition, there should probably be mentioned Phaenocelis purpurea (Schmarda) 1859 {= Comprostatum in- sularis Hyman, 1944), common in the Florida Keys. There remains to be mentioned the turbellarian fauna of the floating Sargassum. This includes acoels, rhabdocoels, and polyclads and has been discussed by the writer in a previous publication (1939b). There are two common Sargassum poly- clads, Gnesioceros sargassicola (Mertens) 1833 and Hoploplana grubei (Graflf) 1892. The former is very similar in appearance to Gnesioceros floridana, and there is some suspicion in the writer's mind that the latter may be only a littoral variant of the former. H. grubei is a small, oval worm with a white reticulation on a brown ground. Large numbers of both species of polyclads were taken from the Sargassum in the Gulf of Mexico by the Bingham Oceanographic Foundation at Yale Uni- versity. There are no records of the occurrence of smaller Turbellaria on the Sargassum in the Gulf of Mexico, but presumably some are present there. LITERATURE CITED Hyman, L. H. 1939a. Some polyclads of the New England coa.st, espe- cially of the Woods Hole region. Biol. Bull. 76: 127-152. 1939b. Acoel and polyclad Turbellaria from Bermuda and the Sargassum. Bull. Bingham Oceanogr. Coll. 7, Art. 1, 26 pp. 1940. The polyclad flatworms of the Atlantic coast of the United States and Canada. Proc. U. S. Nat. Mus. 89: 449-495. 1944. Marine Turbellaria from the Atlantic coast of. North America. Am. Mus. Novitates, No. 1266, 15 pp. PEAR.SB, A. S. 1938. Polyclads of the east coast of North America. Proc. U. S. Nat. Mus. 86: 67-98. and Littler, J. W. 1938. Polyclads of Beaufort, N. C. Jour. Elisha Mitchell Sci. Soc. 54: 235-244. Pearse, a. S., and Wharton, G. W. 1938. The oyster "leech," Stylochus inimicus Palombi, associated with oysters on the coasts of Florida. Ecol. Monogr. 8: 605-655. SCHBCHTER, V. 1943. Two flatworms from the oyster-drilling snail, Thais floridana haysae Clench. Jour. Para.sit. 29: 362 THE NEMERTEAN FAUNA OF THE GULF OF MEXICO By Wesley R. Coe, Professor Emeritus, Yale University Nemerteans are found along all the seacoasts of the world and off the shores to depths of hun- dreds of meters. Some of the species are circum- polar, extending southward along the Atlantic coasts as far as Madeira or South Africa on the east and to southern New England or Florida or the Gulf of Mexico on the west, and in the Pacific to California or Mexico on the east and to Japan on the west. A few species live in both the North- ern and Southern Hemispheres and a few others in fresh-water streams and lakes. Some are limited to the polar seas and others to the tropics, but many have a wide geographical range and survive under a great variety of environmental conditions. Some of the bathypelagic species live at depths of 1,000 to 2,000 meters or more, and the populations may be carried for thousands of miles by the deep ocean curreats, reproducing generation after generation in their endless circuits throughout the great oceans. With the exception of the species mentioned in a few local lists of invertebrates, and two papers by Coe (1951, 1951a) no reports of the nemerteans ot the Gulf have been published previ- ously. The following account is compiled from the records of the collections sent to the writer from various localities between Apalachicola, Fla., and Port Aransas, Tex., during the past years. No in- formation is yet available for all that portion of the Gulf coast south of the Mexican border, although there are several reports on the species found at various West Indian islands. Several of these species have been found on the Atlantic coast of southern Florida and presumably occur also on the Gulf coast (Coe 1951a). In the area covered by this report only 17 species are at present known, presumably for the reason that only sporadic efforts have been made toward a complete survey of the littoral fauna of that region. On the Atlantic coast of North America there are 53 known species of nemerteans (Coe 1943) and on the Pacific coast 95 species (Coe 1940). Hence, it seems probable that less than half of all the species now actually living in the Gulf can be included in this report. Even on the Atlantic coast the nemerteans have been studied extensively only as far south as New Jersey, and our knowledge of the species living between that State and Florida is based on collections made at widely separated localities. It may therefore be assumed that some, perhaps many, additional species remain to be discovered. GEOGRAPHICAL DISTRIBUTION All except two of the species known from the northern shores of the Gulf are also found on the Atlantic coast. Therefore, it may be assumed that the nemertean faima of this part of the Gulf coast is, or has in the geologically recent past been, a continuation of that of the Atlantic coast. It seems quite possible that it is now a separate fauna which was isolated in Pleistocene times by the Florida peninsula. To determine whether the species of the two areas are at present continuous, it is essential to obtain additional collections on both sides of the southern half of that peninsula. It is already known that the species found at Pensacola, on the Gulf side, are similar to those found by the writer personally at St. Augustine, on the Atlantic side. It is also known that these two nemertean faunas are separated by an area in which other species predominate (Coe 1951, 1951a). Because of the great differences in the environmental conditions between the coasts of northern and southern Florida, however, a more or less complete separation would seem probable. In other groups of invertebrates, likewise, the species found in southern Florida are commonly identical with those of the West Indies and northern South America. The nemerteans evidently represent a conserva- tive group and many of the species have a wide geographical distribution. Of the 17 species at present known from the Gulf of Mexico, all except 303 304 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE Paranemertes bioceUata, Amphiporus texanus, and Cerebratulus ater are widely distributed on the Atlantic coast, and 4 of them, namely, Tubulanus pellucidus, Zygeupolia rubens, Zygonemerfes vires- cens, and Amphiporus crv^ntatus occur also on the Pacific coast but not in Europe; 2 others, Car- cinonemertes carcinophila and Tetrastfmma vermi- culus are found on European coasts but not in the Pacific; Oerstedia dorsalis, Tetrastemma candi- dum, and Malacobdella grossa are circumpolar, inhabiting European shores as well as both the Atlantic and Pacific coasts of North America, while the remaining 5 species, Carinoma trema- phoros, Lineus socialis, Micrura leidyi, Cerebra- tulus lacteus, and Amphiporus ochraceus are known only from the Atlantic and Gulf coasts. Para- nemertes bioceUata and Cerebratulus texanus have been found only on the northern Gulf coast, while Cerebratulus ater is reported from off the Cape of Florida and at Curasao. For comparison, it may be noted that 11 of the 53 species found on the Atlantic coast are identical with species in European waters, while 12 of the Atlantic coast species occur also on the Pacific coast, and 2 of these extend also to Japan. No less than 18 of the species found on the Pacific coast are thought to be identical with well-known European species, and others are closely similar (Coe 1943). The nemertean fauna of Bermuda resembles more closely that of Europe and Madeira than that of the American coast in spite of the proximity of the latter. As a general rule, the invertebrates in the Gulf are much smaller when mature than are the mem- bers of the same species in more northern an4 colder localities. This applies likewise to the nemerteans. To anyone familiar with the species on the New England coast the representatives of the same species in the Gulf appear to be dwarfs. Species living among Bryozoa, algae, and other growths in the intertidal zone farther north are more commonly found beyond the low-tide level in the Gulf. REPRODUCTION AND REGENERATION If ripe individuals of both sexes are available, nearly all the species, but especially Cerebratulus lacteus, are suitable for the study of embryological development. From a large ripe female of C. lacteus many thousand eggs may be obtained, and these usually develop rapidly into pilidium larvae after artificial insemination. Most of the species restore by regeneration the posterior end of the body after injury or removal. Lineus socialis provides an example of asexual reproduction by fragmentation and is unexcelled for the study of the complete regeneration of minute fragments of the body. Almost any small piece of the body, provided it contains a portion of one of the nerve cords, will regenerate into a minute replica of the original worm (Coe, 1929-34). ECOLOGY Most of the species on the Gulf coast are found biu-rowing in the sand or mud in the low intertidal zone and below to areas where the depth of water is 10 meters or more. Others live beneath stones or among dead shells, while many of the smaller species occur among Bryozoa, algae, and other growths in the intertidal zone and below. FOOD Nemerteans are usually carnivorous, feeding on a great variety of worms, crustaceans, mollusks, and other small, soft-bodied animals. To secure their prey they are furnished with highly special- ized sense organs and most of them with a long, eversible proboscis. This organ is a formidable weapon, provided in some species with one or more acutely pointed stylets which puncture dnd paralyze the prey, allowing the soft parts to be sucked into the mouth. In species without stylets the proboscis, which is covered with a tenacious secretion, can be coiled about the prey, thereby holding it tightly until it can be drawn into the mouth. Only one of the species, Mala- cobdella grossa at present known from the Gulf is commensal living in the mantle cavity of clams. Another species, Carcinon.emertes carcinophila, sucks the blood in the gills and the substance of the eggs of various species of crabs and is therefore truly parasitic. GULF OF MEXICO 305 KEY TO THE SPECIES AT PRESENT KNOWN FROM THE GULF OF MEXICO Based Mainly on Easily Recognizable External Characteristics With suction disk at posterior end of body; commensal in bivalve moUusks - M alacobdella grossa Without suction disk; not commensal in bivalves 2 Mouth posterior to brain; proboscis not armed with stylets 3 Mouth anterior to brain; proboscis with central stylet and usually with two or more pouches of accessory stylets.. 9 Head without lateral longitudinal grooves 4 Head with lateral longitudinal grooves 6 Posterior end without slender caudal cirrus 5 Posterior end with long caudal cirrus; head acutely pointed Zygeupolia rubens Body small, white; posterior end slender Tubulanus pellucidus Body when mature usually 30-150 mm. long; red or yellowish red; posterior end broad and flattened . Carinoma tremaphoros Body slender, rounded; head with two to eight pairs small ocelli Lineus socialis Body flattened in intestinal region ; head without ocelli 7 Lateral margins rounded in intestinal region; not adapted for swimming; color red or rosy Micrura leidyi Lateral margins in intestinal region thin; adapted for swimming; color either pale or black 8 Color whitish, pale yellow, or rosy Cerebratulus lacleus Color black Cerebratulus ater Proboscis with central stylet only and no accessory stylets; parasitic on crabs Carcinonemeries carcinophila With two or more pouches of accessory stylets; not parasitic 10 Proboscis with four or eight pouches of accessory stylets; only one pair of ocelli Paranemerles biocellata Proboscis with two pouches of accessory stylets ; head with more than one pair of ocelli 11 Ocelli numerous, extending posteriorly beyond head Zygonemertes virescens Ocelli limited to head 12 More than two pairs of ocelli 13 Only two pairs of ocelli 15 Ocelli in a single row on each side of head ; blood corpuscles red A mphiporus cruentatus Ocelli in several groups or irregular rows; blood nearly colorless 14 14. Central stylet of proboscis rounded at both ends and slightly constricted in the middle Amphiporus ochraceus 14. Central stylet truncated at both ends; not constricted in the middle Amphiporus texanus Yellowish, without spots of dark pigment Tetrastemma candidum Body small, cylindrical ; color variable ; irregularly spotted with brown 16 Body short and firm; ocelli large, those of the same side not coimected by band of pigment Oerstedia dorsalis Body soft, yellowish; the two ocelli of same side connected by band of dark pigment Tetrastemma vermiculus 1. 1. 2. 2. 3. 3. 4. 4. 5. 5. 6. 6. 7. 7. 8. 8. 9. 9. 10. 10. 11. 11. 12. 12. 13. 13. 15. 15. 16. 16. SYSTEMATIC DESCRIPTION OF SPECIES The following pages contain abbreviated de- scriptioos of the species at present known from the Gulf, based mainly on easily recognizable external characteristics. The geographic range, as given, indicates the limits of the species insofar as at present known and should not be interpreted as implying that the species will not later be found elsewhere. Outline drawings of each of the species have been published by Coe (1951a). Order 1 PALEONEMERTEA Family TUBULANIDAE Tubulanus pellucidus Coe, 1940, 1943 Carinella petlucida Coe, 1895. The minute worms belonging to this species may be recognized by their slender, white bodies and by the absence of both ocelli and longitudinal grooves on the head. Length when mature 10 to 25 mm., width 1 mm. or less. The worms live in delicate, cellophane-like tubes among algae and other growths in the intertidal zone and below to a depth of at least 20 meters. Recorded from southern New England to northern Florida, also Pensacola, Fla., and presumably occur elsewhere along the Gulf coast. Found also from Monterey Bay to San Diego, Calif. Family CARINOMIDAE Carinoma tremaphoros Thompson, 1900; Coe, 1943 Body pale reddish or yellowish, with broadened posterior end which is without caudal cirrus. Head broad, without ocelli or longitudinal grooves. Length when mature 30 to 150 mm., width 2 to 5 mm. The worms burrow in mud, sandy mud and clay, or live beneath stones in the intertidal zone 306 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE and below from Cape Cod to northern Florida and on the Gulf coast at least as far west as Louisiana. Order 2 HETERONEMERTEA Family LINEIDAE Zygeupolia rubens Goe, 1905, 1940, 1943 Valencinia rubens Coe, 1895; Zygeupolia Hloralis Thompson, 1900. The worms of this species may be identified by the red or rosy color and sharply pointed head which is devoid of ocelli or longitudinal grooves, as well as by the long caudal cirrus. Length 40 to 80 mm. when mature; width 2 to 5 mm. Found in sand or beneath stones in the inter- tidal zone and below from southern New England to northern Florida and on the Gulf coast westward to Copano Bay, Tex.; also from Monterey Bay, Calif., to Mexico. Lineus socialis Verrill, 1892; Coe, 1943 Nemerles socialis Leidy, 1855. Recognized by the very slender body with a row of two to eight small ocelli on each side of head and by the tendency of the worms to coil in spiral when disturbed. Length when mature 30 to 150 mm., width 1 to 3 mm. Color variable, often pale olive green, greenish brown, or reddish brown ; frontal margin and lateral borders of head whitish; brain region deep red; body sometimes encircled with 6 to 20 or more narrow and inconspciuous rings of lighter color. Lives beneath stones and among mussels and other growths in the intertidal zone from Bay of Fundy to northern Florida and on the Gulf coast westward to Texas. Locally common and often gregarious. Differs from all other species on this coast by its capacity for asexual reproduction by fragmen- tation (Coe 1930). If the body is cut into many small pieces each fragment will ordinarily regen- erate into a minute replica of the original worm. For complete regeneration the fragment must con- tain a portion of one of the nerve cords. This is excellent material for such studies, since the worms or their fragments may live for a year or more in jars of sea water with pebbles in the bottom pro- vided the water is changed occasionally (Coe, 1929-34). A period of asexual reproduction may be followed by dioecious sexual reproduction in which the sexes mate and the eggs are deposited in a thick mucous sheath. Micrura leidyi Coe, 1943 Meckelia rosea Leidy, 1851; Cerehraiulus leidyi Verrill, 1892. One of the most common of the species of ribbon worms in the Gulf and along the east coast of the United States. The body is rather slender, cylindrical in anterior portion, and much flattened in intestinal region; very fragile; head slender, without ocelli; caudal cirrus small; color deep red or purplish red, lighter anteriorly; anterior border of head and mouth region whitish; length 20 to 300 mm., width 1 to 6 mm. Lives in sand and under stones in the intertidal zone and in shallow water from Massachusetts Bay to the coast of northern Florida and in the Gulf west to Texas. Individuals of this species are among the most fragile of all nemerteans and usually break into many pieces when lifted from the sand. The numerous eggs, which are excellent for embryological studies, are shed into the water from July to October on the coast of southern New England, but the season of reproduction in the Gulf is not at present known. The larvae can be reared to the pilidium stage without difficulty. The adult worms have the capacity for the rapid posterior regeneration of fragments from the anterior part of the body, but if the head is removed it is seldom, if ever, regenerated. Cerebratulus ater Verrill, 1895; Coe, 1943 Meckelia atra Girard, 1851. This species is known from a single specimen dredged in deep water off the Cape of Florida, together with two headless fragments which pre- sumably belonged to the same species from near Curasao. The body is uniformly black in color except for the pale anterior extremity. Cerebratulus lacteus Verrill, 1892; Coe, 1943 Mecklia lactea Leidy, 1851; M. ingens Verrill, 1873. The body is long and ribbonlike, with flattened intestinal region and thin lateral margins; well adapted for swimming. Ocelli absent; caudal cirrus slender. Mature individuals are larger than any of the other nemerteans found on the Gulf coast, often exceeding a meter in length. Color variable; whitish, pale yellow, flesh color, pale red or salmon. Young individuals are usually translucent white, with pale yellow or brown intestinal diverticula. This is a common species, burrowing in the mud or sand in the intertidal zone from Maine to GULF OF MEXICO 307 northern Florida and along the Gulf coast to Port Aransas, Tex. Each large female produces each season several to many thousand translucent ova which are fertilized in the water and develop rapidly into pilidium larvae. The eggs of this species have been widely used in experimental studies and for class demonstrations. Posterior regeneration takes place readily, but anterior regeneration is limited to the head anterior to the brain, although head- less fragments, which can take no food, may live for several months. With occasional changes of the sea water and low temperature, a worm of this species may live for a year or more without food, the body meanwhile being reduced to a small fraction of its original size. Order 3 HOPLONEMERTEA Family EMPLECTONEMERTIDAE Paranemertes biocellata Coe, 1944 This species may be recognized by the slender, pale greenish body with sharp