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. 



