With the Shannon- Weaver index, an index above 3.0 generally reflects a healthy, unstressed 

 community while an index below 1.0 indicates a monospecific community under stress. An 

 index range of 1 .0-3.0 seems to indicate a community under some stress (Newell 1 976a). A low 

 diversity index indicates a largely monotypic community dominated by a few abundant 

 organisms. Often the total number of species is low, suggesting that degraded environmental 

 conditions exist which favor the proliferation of a few tolerant species and the removal of less 

 tolerant ones. A high diversity index indicates a heterogeneous community in which abundance 

 is distributed more evenly among a number of species and the total number of species is 

 generally high (Newell 1977). 



Theoretical maximum diversity (Dmax) exists if each individual belongs to a different species 

 and theoretical minimum diversity (Dmin) exists if all individuals belong to the same species. 

 The distribution of individuals among species lies between these extremes in most communities 

 ■§i and diversity is intermediate. Redundancy (R) is an expression of the dominance of one or more 



species and is inversely proportional to the wealth of species (Wilhm and Dorris 1968). 

 Redundancy is always between and 1 . The numerical value for diversity (D) lies between 

 Dmax and Dmin and shows the actual diversity of the aquatic community as compared to the 

 maximum and minimum diversities which could have occurred in the given sample. When 

 diversity is high, redundancy is low and vice verse (Spence 1975). 



Comparisons of bottom fauna diversity before and after dam failure using the Shannon-Weaver 

 diversity indices are shown in Table 4. The indices are based on pooling three one-square-foot 

 samples at Pop's Place in 1971 and 1972, four one-square-foot samples at Pop's Place in 1975 

 and three one-square-foot samples at Flesher in 1975. The 1971 data for Pop's Place are taken 

 fi-om Spence (1975), page A-86, since diversity indices had already been calculated. Diversity 

 indices had not been calculated by Spence (1975) for the October, 1971 samples at Flesher but 

 the data (See p. A-90) were used to calculate the indices after dam failure. The 1 972 Flesher 

 samples had not been identified when the Spence (1975) report was completed. These samples, 

 as well as the 1975 samples, were identified by Robert Newell after dam failure. Pooled data for 

 all the samples (except for 1971 at Pop's Place) are shown in Appendix C-1. 



Diversity indices for each one-square-foot sample collected before and after dam failure are 

 shown in Table 5 and Appendix C-2) 



11 



