5. Fully developed gonads were found in 

 thread herring 140 to 165 mna. fork length 

 taken off St. Petersburg Beach in early April. 

 Spent gonads, indicative of spawning, were 

 found by late May when water temperature 

 was about 27° C. Gonad developnaent indicates 

 a spawning peak in June. 



6. The ratio of males to females in the 

 summer thread herring population off St. 

 Petersburg Beach was about 1 to 5 whereas 



that in the winter population off Fort Myers 

 was about 1 to 1 . 



7. Ripe thread herring were induced to 

 spawn in laboratory tanks, but the eggs did 

 not survive. 



8. The stomachs of ZOO mackerel taken by 

 conamercial fishermen in the Naples area 

 were examined, and no thread herring were 

 found. 



RED-TIDE PROGRAAA 



TOXIN RESEARCH 

 Dean F. Martin 



The University of South Florida completed 

 a contract with this Laboratory to isolate and 

 characterize the fish-killing toxin of red tide. 



Contract research demonstrated that there 

 are two chemically distinct toxins. Aprocedure 

 was developed to isolate and purify both sub- 

 stances from cultures and natural blooms. 

 One toxin is minor and can be isolated only in 

 trace quantities. The major substance is a 

 neurotoxin, and properties from samples 

 isolated from unialgal cultures and blooms of 

 Gymnodinium breve appear to be identical on 

 the basis of infrared data. 



The major toxin isolated is a light yellow, 

 low-melting solid. Qualitative elemental 

 analysis identified the presence of carbon, 

 hydrogen, and phosphorus. Sulphur, chlorine, 

 bromine, and nitrogen were absent. The sub- 

 stance was characterized by the absorption 

 spectra (ultraviolet and infrared), the nuclear 

 magnetic resonance spectrum, and optical 

 activity nneasurements. A molecular weight of 

 650 and the formula C90 H^gj "^17 ^ were 

 determined for the major toxic substance. 



ENCYSTMENT STAGE OF GYMNODINIUM 

 BREVE 



William N. Lindall, Jr. 



Studies on the encysted forms of G. breve 

 were completed through use of an electron 

 nriicroscope. By using standard fixation solu- 

 tions (gluteraldehyde and osmic acid) with 

 variations in fixing times and dehydration, 

 repeatable results were obtained. These re- 

 sults are not ideal because of difficulties in 

 preserving, dehydrating, and embedding such 

 a fragile organism, but the basic organelles 

 within the cell were photographed and identi- 

 fied. Trichocysts were found within the cells, 

 which to our knowledge have never been re- 

 ported in G. breve . 



The reason for labeling the results "not 

 ideal" is that the cytoplasnn is vacuolated and 

 appears to have been leached out during the 



harsh preparation that is required for electron 

 microscopy. This vacuolation may, however, 

 be characteristic of the cyst form, which is 

 rounded and smaller than the motile fornn. 

 The same techniques are being applied to the 

 motile cell in an attempt to compare the two 

 forms. 



PLANKTON ECOLOGY PROJECT 



J. Kneeland McNulty 



A study of primary productivity in Tampa 

 Bay continued in the past year. Its purpose 

 was to learn more about fundamental ecological 

 processes at work in the Bay, especially those 

 which relate directly to the production of 

 phytoplankton including Gymnodinium breve, 

 the causative agent of red tide. 



All fisheries depend directly or indirectly on 

 plant production. Even so, estimates of phyto- 

 plankton productivity are available for less than 

 10 inshore areas worldwide. The Tampa Bay 

 study may be the most extensive of its kind in 

 any estuary. It dates from September 1962, and 

 covers representative areas seasonally. 



The sequence of pertinent ecological events 

 in Tampa Bay in fiscal year 1968 is described 

 in this report to illustrate the seasonal inter- 

 relationships of environmental and biological 

 processes. The data are graphed as if they were 

 in chronological sequence despite the dis- 

 continuity between June 1968 and July 1967 

 (fig. 18). Moving averages of the order three 

 \vere used to smooth the data. 



Average annual solar radiation at Tampa is 

 one of the highest at a seacoast location in the 

 Nation. Seasonal variations during the past 

 year were typical. Solar radiation rose sharply 

 in March, peaked in late May, dropped to a 

 summer low in August because of summer 

 rains, reached a second peak from mid- August 

 to late September, then dropped steadily to the 

 winter minimum in mid- December. 



Primary productivity attained two peaks-- 

 one in April- May and the other in August- 

 September. Separate stimuli apparently trig- 

 gered the two peaks. The spring increase 

 began when water temperature reached about 

 22° C., 40 days after solar radiation began to 



22 



