Preliminary photocell readings within the area 5 to 40 miles off- 

 shore indicate a broad photic zone, with increased light transmission in a 

 seaward direction. At stations 40 miles offshore, light values of 8-80 foot- 

 candles were recorded at depths of 126-129 feet from November I960 through 

 January 1961. In the extremely turbid waters of central and upper Tampa 

 Bay, light transmission diminished rapidly with depth during the same period. 

 In waters of 25-41 feet, foot-candle readings ranged from 0-9 while near sur- 

 face re'adings at the same stations ranged from 49-1, 800 foot-candles. No 

 relationship was noted between distribution of G. breve and the percentage of 

 light transnnission. The greatest numbers of Prorocentrum micans and 

 Ceratium furca were associated with the clearest water during the November 

 blooms in Tampa Bay. 



Vessel PvINGFISH used in study of Tampa Bay and vicinity. 



Observations on salinity, water temperature, and the distribution of G. breve 



Salinity and water temperature are two important factors in deter- 

 mining the distribution of G. breve. The complete absence of G. breve in 

 upper and central Tannpa Bay at salinities between 13.93%o and 30. 86''/oo indi- 

 cates that low salinities may serve as a barrier to this organism. The high- 

 est numbers of G. breve during blooms occurred at salinities from 31. 33%: 



62 



