Table 7, (Concluded. ) 



Phytoplankter 



9 10 



Dinophysis caudata 

 Dinophysis diagenesis (?) 

 Dinophysis tripos 



PHYLUM CHLOROPHYTA 



Pediastrum simplex 



Pediastrum duplex 



Pediastrum tetras var. tetraodon 



Scenedeslrius quadricauda 



Studies by R. L. Iverson and his 

 students indicate that phytoplankton 

 productivity is an important source of 

 organic matter in the Apalachicola 

 estuary. In general, phytoplankton growth 

 depends on temperature, light, and 

 avail able nutrients (nitrogen, ohosphorus) 

 (Figure 23). Temperature is the primary 

 limiting factor for phytoplankton 

 productivity in the estuary during the 

 winter months. Nutrient concentrations 

 and possibly predation pressure control 

 production from late soring 

 The usually low levels of 

 productivity during the 

 way to peaks in April, 

 are noted during summer 



phytoplankton 

 to the fall, 

 phytoplankton 

 winter give 

 Secondary peaks 

 and fall months. 



The average cA^ phytoplankton 

 productivity (Figure 23) ranged from fi3 to 

 1,694 mg C m"? dayl (Estabrook 1973; 

 Livingston et al. 1974). The relationship 

 of phytoplankton productivity and 

 predation pressure from zooplankton has 

 not been determined. However, since river 

 discharge is strongly associated with 

 nutrient concentrations in the estuary 

 (Livingston et al. 1<^74), such factors as 

 river flow and nutrients, together with 

 the general ecological conditions in the 

 estuary, combine to control the phvto- 

 olankton productivity of the bay system. 



Despite considerable spatial and 

 temporal variability of phytoplankton 

 productivity, Eastabrook (1973) estimated 

 an annual productivity value of 371 g C 



m-^ for the Apalachicola estuary. This 

 figure was taken from averaged data (five 

 bay stations) sampled monthly over a 

 12-month period. Based on these figures, 

 the phytoplankton productivity from the 

 bay system approximates 233, ?84 t C vr"l 

 (257,070 tons C yr-1); for the immediate 

 estuary (East Bay, Apalachicola Bay), this 

 figure is 103,080 t C yr-1 (113, S94 tons C 

 yr"l). When compared to production values 

 in other estuaries of the region (Table 

 8), the phytoplankton productivity and 

 chlorophyll _a levels in the Apalachicola 

 estuary are relatively high. 



b. Submerged vegetation . The 



relatively high levels of color, 

 turbidity, and sedimentation tend to limit 

 submerged macrophytes to the shallowest 

 portions of the Apalachicola estuary 

 (Livinqston 1980c, ia83c). Species 



composition and distribution of seagrass 

 beds are given by Livingston (l^SOc, 

 1983c). A major concentration of 



seagrasses occurs in eastern St. George 

 Sound, which remains outside of the 

 influence of river drainage (Table 1, 

 Figure 19). Such areas are dominated bv 

 turtle grass ( Thalassia testudinum ), shoal 

 grass ( Halodule wrighti i ), and manatee 

 grass ( Syrinqodium f il iforme ) . Seagrass 

 beds are also located in upper portions of 

 East Bay. Such assemblages are dominated 

 by tape weed ( Vail isneria americana ), 

 widgeon grass ( Ruppia maritima TJ and sago 

 pondweed ( Potamogeton sp. ) . Since the 

 early 1980's Eurasian watermil^oil 

 ( Myriophyllum spicatum ) has taken over 



35 



