samples were collected periodically to check 

 for the occurrence of G. breve . 



Analysis of regular sannpling data, when 

 completed, should provide a picture of the 

 annual phytoplankton cycle in Florida west 

 coast waters. Important diatoms encountered 

 in regular samples were: Skeletonema 

 costatum , Asterionella japonica , Chaetoceros 

 spp., Nitzschia spp., Leptoc ylindrus spp., 

 Rhizosolenia spp., and Thalassionema nitz- 

 schioides . 



A red tide in July and August in the offshore 

 water of Apalachee Bay was studied by mem- 

 bers of the Marine Laboratory. Counts of 

 diatoms and number of species were low in 

 these samples. Prevalent diatoms were: 

 Rhizosolenia stolterfothii , Lauderia bore- 

 alis (?), Hemiaulus sp,, Chaetoceros spp., 

 and several species of Nitzschia . Tricho- 

 desmium , a blue- green alga, was comnnon 

 also in these samples. 



The Florida Marine Laboratory's Dino- 

 flagellate Project was briefly described. 



A morphological variant of G. breve that 

 had been observed during a red-tide outbreak 

 in Apalachee Bay (July and August 1964) was 

 discussed. A report "Observations on Gym- 

 nodinium breve Davis and other dinoflagel- 

 lates," is in press (Fla. Bd. Conserv. Mar. 

 Lab. Prof. Pap. Ser. 7, Part I). 



Studies in southwest Florida (November 

 1963 to Novennber 1964) were nnentioned but 

 not discussed in detail. As of March 1965, 25 

 genera of dinoflagellates had been recorded 

 from the Gulf of Mexico and adjacent waters. 

 The interpretation of these studies is in 

 progress and will be published in Fla. Bd. 

 Conserv. Mar. Lab. Prof. Pap, Ser. 7 as 

 Part II. 



CURRENT FIELD STUDIES OF THE 

 BUREAU OF COMMERCIAL FISHERIES 



By Alexander Dragovich 



Bureau of Commercial Fisheries Biological 

 Laboratory, St. Petersburg Beach, Fla. 



Tampa Bay, Charlotte Harbor, and the ad- 

 jacent Gulf to 20 miles offshore now constitute 

 the study area of the St. Petersburg Station. 

 The area of about 1,500 square miles is the 

 site of many past red-tide outbreaks. Seven 

 major rivers flowing into the Gulf also are 

 included in the area. 



We have reviewed past studies, eliminated 

 measurements found to be unrelated to red- 

 tide blooms, and added new observations where 

 applicable. Our past research included several 

 hydrological measurements and counts of 

 G. breve . Of the hydrological determinations, 

 we retained temperature, salinity, and in- 



organic phosphate phosphorus; dissolved 

 oxygen and iron were added. An intensive qual- 

 itative and quantitative study of phytoplankton 

 associated with G. breve , and chlorophyll 

 determinations, also were added to our bio- 

 logical program in February. 



The relation of planktonic successions to 

 physical, chemical, and biotic factors was 

 reviewed. 



The preliminary examination of samples 

 collected during the first 8 months of this 

 study showed that phytoplankton consisted 

 principally of diatoms, dinoflagellates, tin- 

 tinnids, and occasionally blue-green algae. 

 Sceletonema costatum was the most numerous 

 organism in the bays. The concentrations of 

 S. costatum decreased seaward from the heads 

 of Tampa Bay and Charlotte Harbor; this alga 

 was uncomnnon 10 and 20 miles offshore. The 

 most intense blooms were during late winter 

 and early spring. During September S. costatum 

 was usually associated with Asterionella 

 japonica. The spring bloonn was a mixture of 

 species of diatoms and dinoflagellates. Gon- 

 yaulax diegensis , Ceratium furca , and Poly- 

 krikos Hartmanii Zimmermann were respon- 

 sible for the spring and fall blooms of 

 dinoflagellates. In the areas with the most 

 intense blooms of C. furca (14.29 x 10° cells 

 per liter), the water was discolored blood-red. 

 No mortality of fish or of other organisms 

 was observed in the field. C. furca was not 

 toxic to a few species of resident fish when 

 tested in laboratory experiments. An April 

 increase in populations of diatoms in Tampa 

 Bay was attributable to Melosira nummuloides , 

 Biddulphia sinensis , Rhizosolenia stolterfothii , 

 and a few species of Chaetoceros . G. breve was 

 not found in samples collected during the study. 



Phytoplankton collections from the bays sug- 

 gested seasonal changes in species composi- 

 tion. The dinoflagellates bloomed during spring 

 and fall; blooms of different species of diatoms 

 occurred throughout the period. The appearance 

 and disappearance of certain species may be 

 determined by water temperature. Upon com- 

 pletion of the study we may be able to dis- 

 tinguish "warm-water" and "cold-water" 

 species. 



The offshore plankton was donninated by 

 diatoms throughout the period. The diversity 

 of species was greater in the offshore waters 

 than in the bays. The phytoplankton density 

 was greatest in the upper portion of Tampa 

 Bay, however, in an area enriched by river 

 inflow. Extensive surface concentrations of a 

 blue-green alga, Skujaella thiebauti , were 

 present in the offshore waters from February 

 through July. This alga forms a fine, rusty- 

 beige dust or film on the sea surface and is 

 often mistaken by commercial airline pilots 

 for red tide. Dense concentrations of this 

 organism sometimes cover several square 

 miles of the sea; it undoubtedly produces tons 

 of organic matter in the offshore waters. Little 



