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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. 



