induced movement across the many 

 enclosing mud banks and mangrove 

 islands. Gorsline (1963) has de- 

 tected very weak counterclockwise 

 currents within some of the larger 

 lakes. 



The Atlantic subenvironment 

 experiences near normal salinities 

 (35-41 ppt) and more moderate tem- 

 peratures ranging from 17 to 32°C 

 (63 to 90°F). Beginning at the low 

 coral keys Florida Bay exchanges 

 waters with the Straits of Florida 

 through numerous channels between 

 islands. In addition, there are 



indications that some seepage occurs 

 across the porous Key Largo Lime- 

 stone. The inland extent of the 

 flushing tends to increase southward 

 toward the sluiceway and the Gulf of 

 Mexico influence. 



The Gulf subenvironment ex- 

 changes with gulf waters through 

 tidal flux and long shore currents. 

 The latter occur within what Marmer 

 (1954) refers to as a current shad- 

 ow, a sheltered section of the con- 

 tinental shelf. However, the lack 

 of sediment accumulation tends to 

 contradict this general hypothesis; 

 apparently current spinoffs do 

 traverse the area regularly forming 

 what Stockman et al. (1967) refers 

 to as the "sluiceway" across the low 

 coral keys between Long and Big Pine 

 Keys into the Florida Straits. 

 Salinities in this subenvironment 

 approach near-normal marine condi- 

 tions. 



The movement of water masses 

 within the interior zone is related 

 to: (1) mainland runoff; (2) sea- 

 sonal rise in sea level; and (3) 

 evaporation. The timing of the 



mainland runoff and sea level rise 

 results in the delayed flow of 

 freshwater into the central bay 

 until the winter months. Lloyd 



(1964), tracking salinity changes 



during the summer, fall, and winter 

 of 1958-59, demonstrates this post- 

 poned freshwater inflow effect as 

 illustrated in Figure 37(a-c). The 

 wet season. May through October (the 

 wetter months being August through 

 September and October), coincides 

 with the period when sea level in 

 this region rises (Marmer 1954) 

 (from August to December, peaking in 

 October). Figure 37a illustrates a 

 time (August) when the freshwater 

 runoff is pushing low salinity water 

 out along the bay's northern border 

 and extending a tongue of brackish 

 water into the central bay. Concur- 

 rently, seasonally high temperatures 

 and restricted circulation along the 

 southern and western bay accelerates 

 evaporation, creating a large region 

 with salinities in excess of 36 ppt 

 (shaded portion of Figure 37a). In 

 November, the annual sea level rise 

 acts to push the brackish, lower 

 salinity waters back up into the 

 northern edge of the bay (Figure 

 37b) resulting in near-marine salin- 

 ities for the remainder of the bay. 

 As the sea level falls (about 15 cm 

 or 6 in), the January-February iso- 

 halines reflect a movement of the 

 lower salinity waters of the main- 

 land swamps into a major portion of 

 the bay (Figure 37c). Ginsburg 

 (1956) reports similar seasonal pat- 

 terns. In addition to the seasonal 

 salinity variation, a 5 to 7 year 

 drought/flood cycle also affects the 

 magnitude of any one year's salinity 

 range (McCallum and Stockman 1964). 

 The effects of these variations may 

 be quite phenomenal on year to year 

 salinity regimes. For example, 



August salinities in central Florida 

 Bay may range from 15 ppt to 50 ppt 

 in succeeding years depending on 

 rainfall/runoff conditions. 



Although sediment chemistry is 

 fairly well studied in Florida Bay 

 (Taft and Harbaugh 1964, Scholl 

 1966), surface water chemistry is 



85 



