where n. = number of individuals of the 1 species, 



1 ^ 



N = total number of individuals for all species, 

 S = number of species. 

 The evenness component of diversity (J) was calculated as; 



J = H' 



Hmax, (Pielou 1977) 



where Hmax =log S and represents the theoretical maximum diversity when all 

 species are equally abundant. Evenness ranges from zero to one; J 

 approaches one as abundance becomes more even among species. 



Diversity calculations excluded oligochaetes and rhynchocoels since 

 they were not identified to species. Other individuals not identified to 

 species, either because they were juveniles or in poor physical condition, 

 were also excluded from this analysis. 



Biological Index Value 



At each station, the Biological Index Value (BIV) of McCloskey (1970) 

 was calculated for the 10 most abundant taxa. Each species was ranked 

 according to its total abundance in each sampling year and these ranks 

 summed for all years. The sum for each taxon was then expressed as a 

 percentage of a theoretical maximum sum, which would occur if a species 

 ranked first in abundance in each of four years. 



Numerical Classification and Cluster Analyses 



The Bray-Curtis similarity coefficient was used to classify stations 

 (normal analysis), based on transformed species counts (In (count + 1)). 

 The coefficient was calculated as: 



^ik " i 2 min (^Ij , ^ik) _ (Clifford and Stenhenson 1^75), 

 S (X. . + X., )'" 



where X.. = abundance of attribute i at entity i, 

 1.1 ^ " 



X., = abundance of attribute i at entity k. 

 ik 



Since Bray-Curtis similarities refer to only pair-wise comparisons, 

 clTister analyses were performed to illustrate relationships among three or 



5 



