Table -i .- -Monthly and annual total precipitation in inches at selected locations along the west 



Florida coast (l95'i-57)^--Continued 



1956 



Compiled from U.S. Department of Commerce, Weather Bureau data, 

 means established by Weather Bureau. 



Numbers in parentheses are long-term 



SUMMARY 



During the 4- year observation period, G. 

 breve was present in nonbloom numbers 

 throughout the year in estuarine and neritic 

 waters from Tarpon Springs to the Florida 

 Evergaldes. The lethal concentration for fish 

 was considered about 250,000/1. In 1954 and 

 1957, concentrations as high as 7,500,000-100,- 

 000,000/1. were noted. The vertical distribu- 

 tion of the organism showed a higher concen- 

 tration near the surface than near the bottom, 

 during daylight. 



Red-tide outbreaks and accompanying fish 

 kills were most pronounced in the fall and 

 winter, usually after periods of heavy rainfall. 

 The highest numbers of G^. breve during 1954 

 were found from Venice south to the Florida 

 Everglades. In 1955, bloonns were confined to 

 the estuarine and neritic waters from Sanibel 

 Island to Cape Sable. No fish kills occurred 



during 1956. Concentrations of G. breve es- 

 sentially remained less than 1,000/1. during 

 1955 and 1956. The 1957 red-tide outbreak was 

 characterized by an initial buildup of the or- 

 ganism in the neritic waters off the major 

 drainage areas: Tampa Bay, Sarasota Bay, 

 Charlotte Harbor, San Carlos Bay, and the 

 Florida Everglades. The highest incidence and 

 numbers of G^. breve were recorded off Egnnont 

 Key and St. Petersburg Beach during Sep- 

 tennber and October 1957. 



G^. breve was not found in waters with salinity 

 lower than 21.0%o. Lethal concentrations oc- 

 curred at 21.0-36.9%o salinities and most 

 frequently at 31.0-34.9%o; it was completely 

 absent at salinities above 37.5%o. 



The observed temperature range for G. breve 

 was 10.3 -33.2 C. The majority of blooms 

 occurred from 14.0°- 25.9° C. Temperatures 

 below 14.0° C. and above 32.0° C. appear to 

 linnit the distribution of this organisnn. 



13 



