Table 21. Factor analysis of physico-chemical variables in the Apalachicola system 

 taken monthly from March 1972 to February 1976. Color (Pt-Co units), turbidity 

 (J.T.U.), Secchi readings (m), salinity (ppt), temperature C^C), and chlorophyll _a (mg 

 1"1) were noted at Station 1. Tidal data included stages of the tide on the day of 

 collection while the wind variable was represented by two vector components (speed, 

 direction) (from Meeter and Livingston 1978). 



benthic macroinvertebrates taken 

 (seasonally) in litter baskets at 

 different stations (3, 5A, IX) along a 

 salinity gradient (Figure 36) (F = 30.4, 

 r^ = 0.45, with S as the dependent 

 variable). Numbers of species taken 

 during a season vary directly with 

 salinity rather than with station-specific 

 characteristics. Similarity coefficients 

 of species composition at the sampled 

 stations are closest during fall periods 

 of high salinity. These results indicate 

 that quantitative and qualitative species 

 representation, regardless of location, 

 are closely related to salinity. 



Similar trends are found for phyto- 

 plankton (Estabrook 1*^73), zooplankton 

 (Edmisten 1979), infaunal 



macroinvertebrates (Livingston unpublished 

 data), and epibenthic fishes and 

 invertebrates (Livingston 1979). 

 Livingston (1979) showed that salinity is 

 directly related to species richness and 

 diversity of estuarine nekton. Stations 

 characterized by low salinity are 

 associated with high numbers of 

 individuals, high relative dominance, and 

 low species richness (Table 20). Outer 

 bay stations, with higher salinities, are 

 defined by relatively low dominance, high 

 species richness and low numerical 

 abundance. High densities of organisms 

 that use the bay as a nursery, such as 

 penaeid shrimp, blue crabs and various 

 finfishes are not usually found in areas 

 having stable patterns of relatively high 

 salinity (Livingston 1984a). 



il 



