stream channels and estuarine meanders. 

 The pH values ranqe from 4.^ to f^.6. 



Studies of the marshes above East Bay 

 (Coultas 1^80; Coultas and Gross 197^^) 

 indicate that the deltaic soils are 

 slightly acidic and become alkaline with 

 depth. The dense mats of roots and 

 rhizomes from the predominant sawgrass 

 ( Cladium .iamai cense ) and needlerush 

 ( Juncus roemerianus ) along the eastern 

 portions of the estuary tend to hold the 

 soils in place. The soils are composed of 

 thin organic deposits mixed with clay and 

 overlie loamy sands of fine-textured 

 materials. Considerable amounts of silt 

 occur in some soils, and most have poor 

 load-bearing capacity because of the high 

 organic content and high field moisture 

 levels. Vegetation differences are 

 attributed to soil salt content. Sawgrass 

 is dominant in areas most affected by 

 river flow (i.e., with low salinity), and 

 needlerush is predominant in tidal areas 

 (i.e., those with higher salinity) 

 (Coultas 1P80). 



Sediments in the estuary are 

 characterized bv mixtures of sand, silt, 

 and shell components (Livingston 1^78). 

 Present sediments are accumulating over 

 tertiary limestones and marls that outcrop 

 in the scoured central channels of West 

 Pass and Indian Pass. St. Vincent Sound 

 and northern portions of Apalachicola Bay 

 are silty areas that grade into sand/silt 

 and shell gravel toward St. George Island. 

 The thickness of these sediments (10-^0 m) 

 (Gorsline 1^63) may be the result of 

 erosion of older deltaic deposits during 

 periods of higher sea level. East Ray is 

 composed of silty sand and sandy shell. 

 Areas near the river mouth have varying 

 quantities of woody debris and leaf 

 matter, especially during winter and 

 spring months of heavy river flooding 

 (Livingston et al. 1976a). The floor of 

 the bay is thus formed largely of quartz 

 sand with a thin (but varying) cover of 

 silt, clay, and debris depending on the 

 proximity to land runoff. 



The estuarine sediments originated in 

 the southern Appalachians and have 

 undergone a complex history of deposition 

 and reworking in the coastal plain 

 deposits, coastal marshes, beaches, and 

 dunes. Fine sediments flow out of the bay 



into the Gulf of Mexico while sand is 

 moved by tidal currents within the bay and 

 at the mouths of the western inlets. The 

 cusp of the Aoalachicola Bay coastline has 

 been built by river sediments deposited 

 during Tertiary and Pleistocene times with 

 modification bv waves and long-shore 

 drift. Puri and Vernon (19fi4) and Clewell 

 (1978) have made a detailed review of the 

 geological formations and soil 

 distribution in the region. 



? . 1 . 3 . Watershed Characterization 



Numerous physiographic, geological, 

 and bioqeographic features contribute to 

 the biotic richness of the Apalachicola 

 drainage system (Clewell 1^77; Means 

 1977). While the Apalachicola basin 

 (Figure 7) lies entirely within the 

 Coastal Plain, it is subdivided into upper 

 and lower regions; the Marianna lowlands. 

 New Hope Ridge, Tallahassee Hills and 



MARIANNA 

 LOWLANDS 



WESTERN 

 RED HIL 



GRAND 

 RIDGE 



|><^PALACHICOLA 

 ' ^-RAVINES 



RIVER 

 BOTTOM 

 LANDS 



/ APALACHICOLA 

 LOWLANDS 



\ COASTAL 

 ^ ^ MARSHES 



OFFSHORE 

 AREAS 



Figure 7. Natural areas 



Apalachicola basin based 

 physiography, vegetation types, 

 geography, and distribution of 

 (after Means 1977). 



of the 

 on the 



regional 

 organisms 



