ross covered i 



AM.r USC 86S Chart* 1249,1250 



Figure 36. Distribution of subenvironments in Florida Bay defined by 

 mollusks (adapted from Turney and Perkins 1972). 



Ginsburg (1956) divides the bay 

 into only two zones, an interior 

 zone unaffected by tides and an 

 outer, tidal ly influenced zone. The 

 latter's interior zone encompasses 

 Turney and Perkins' northern suben- 

 vironment starting from just east of 

 Flamingo, as well as their interior 

 subenvironment. The tidal ly influ- 

 enced zone roughly corresponds to 

 the Gulf and Atlantic subenviron- 

 ments as defined above. 



The four molluskan subenviron- 

 ments are a convenient classifica- 

 tion for hydrologic purposes as 

 well. The barely submerged northern 

 subenvironment lies within the zone 

 influenced by seasonal freshwater 



runoff. Salinities range from 



13-48 ppt, temperatures from 15 to 

 38°C (59 to 100°F). Only the west- 

 ern edge of this zone, from just 

 east of Flamingo to the gulf, is 

 subject to significant tidal flush- 

 ing. Even here hypersaline condi- 

 tions are commonly detected during 

 the dry season (Tabb et al. 1962). 



The interior subenvironment, 

 which contains the most lakes, is 

 characterized by widely fluctuating 

 salinities (22-52 ppt) and very 

 restricted circulation. Net season- 

 al deficits and excesses of runoff 

 and rainfall are strongly reflected 

 in this zone. Flushing is negli- 

 gible except for occasional wind 



84 



