total water area (Table 1). Except for 

 certain areas alonq the eastern portions 

 of St. Georqe Sound, submerqed vegetation 

 in the Apalachicola estuary is light- 

 limited by hiqh turbidity and water color. 

 High sedimentation and resuspension of 

 sediments in the estuary may also affect 

 the seagrass bed distribution. Seagrasses 

 and algal associations are largely 

 confined to frinqes of the estuary at 

 depths of less than 1 m. The largest 

 concentration of these submerged grassbeds 

 is in eastern St. George Sound; such 

 seagrass beds also occur in upper East 

 Bay, inside St. George Island in 

 Apalachicola Bay, and in western St, 

 George Sound. In East Bay, freshwater and 

 brackish-water species ( Val 1 isneri a 

 americana , Ruppi a maritima , and 

 Potamogeton sp. ) are oredominant. Grass 

 beds along the mainland east of the river 

 are dominated by Halodule wrightii , 

 Syringodium fil i forme , and Thalassia 

 testudinum . The shallow lagoonal flats of 

 Alligator Point, Dog Island, and St. 

 George Island are populated by Halodule 

 wrighti i , Gracilaria spp., and Syringodium 

 fil i forme . Few if any grassbeds are found 

 in St. Vincent Sound. 



As a habitat, seagrass beds provide 

 organic matter and shelter for various 

 infaunal and epibenthic invertebrates and 

 fishes. 



?.S.3. Soft-Bottom Substrates 



Muddy, soft bottom substrates 

 comprise about 78% of the ooen water zone 

 of the Apalachicola Bay system and are 

 thus the dominant habitat form in the 

 area. The relative composition of the 

 sand, silt, clay and shell fractions of 

 the sediments depends on proximity to 

 land, runoff conditions, water currents, 

 and trends of biological productivity. 

 Sediment type and associated water-gual ity 

 conditions in the benthic habitat 

 determine the composition of infaunal and 

 epifaunal biological components. 

 Recruitment and community composition of 

 the benthic invertebrates (meio^auna and 

 macrofauna) may depend on the distribution 

 of flocculent resuspended sediments and 

 bedload transport. The unvegetated, soft- 

 bottom habitat in the Apalachicola Bay 

 system represents the basis for imoortant 

 food web relationships in the estuary. 



?.5.4. Oyster Bars 



The Apalachicola estuary is an ideal 

 environment for the growth and culture of 

 the oyster ( Crassostrea virqinica ) . The 

 oyster bars that cover about 1% of the 

 aquatic area of the bay system (Table 1) 

 are an important habitat for various 

 assemblages of estuarine organisms. Malor 

 oyster beds are located in St. Vincent 

 Sound, west St. Georqe Sound, and the East 

 Bay-Apalachicola Bay complex (Figure ?0). 

 New (constructed or artificial) oyster 

 reefs stq located in eastern portions of 

 St. Vincent Sound. The highly productive 

 natural oyster bars of St. Vincent Sound 

 and western St. George Sound represent the 

 primary concentrations of commercial 

 oysters in the estuary. The waters of 

 both areas are well circulated by the 

 prevailing currents and are characterized 

 by salinity conditions optimal for oyster 

 propaqatinn and qrowth (l.ivinqston 1983c, 

 d). The reefs near the seaward edqe of 

 the bay thrive when the river is high 

 while those near the river mouth do well 

 during conditions of low water. 



Whitfield and Beaumariage (1977) 

 estimate that about 40''^ of Apalachicola 

 Bay is suitable for growing oysters but 

 that substrate type is a major limiting 

 factor. Rapid oyster growth due to 

 favorable environmental conditions 

 accounts for the fact that over 90% of 

 Florida's oysters (8%-10% nationally) come 

 from the Apalachicola estuary. 



?.5.5. Nearshore Gulf Environment 



The shallow nearshore gulf is a 

 drowned alluvial plain grading into a 

 limestone plateau to the east and south 

 (McNulty et al. 1972). The eastern Gulf 

 of Mexico is characterized by moderately 

 high-enerqy sand beaches. The north qulf 

 coast sedimentary province contains relict 

 sand west of the Apalachicola delta. The 

 Miocene relict sands and clays off the 

 Apalachicola embayment qrade into quartz 

 sand and mud over limestone characteristic 

 of the extreme eastern gulf region. Much 

 of the water motion along the shallow West 

 Florida Shelf is due to tides, although 

 wind effects are evident, especially in 

 winter when cold fronts move through the 

 area. The high-salinity coastal waters 

 are well mixed except durinq warmer months 



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