Benthic index values were calculated for the test data set by applying the appropriate weighting factors to the 

 individual components according to the methods outlined in Guideline 3, Table 3-2. The benthic index values 

 were then compared to the original classification of sites as degraded or undegraded. This comparison 

 indicated an overlap in classification of degraded and undegraded sites between benthic index values of 3.5 

 and 4.5. To be conservative, we extended the threshold values for determining site classification using the 

 benthic index such that index values < 3.0 represented degraded sites, index values > 5.0 represented 

 undegraded sites, and index values between 3 and 5 represented sites with marginal conditions (these sites 

 were misclassified by the original analysis). The distribution of benthic index values among the test sites 

 (Fig. 3-9) shows the overlap of classification as degraded or undegraded by the benthic index with the 

 symbols indicating the original classification of test sites using a priori criteria. 



1.1 

 1 



0.9 

 0.8 

 0.7 



fe 0.6 



o 



Q. 0.5 



0.4 



0.3 



0.2 



0.1 







Power Curves - Benthic Index 



.03 , 



8 9 



Years 



10 



11 



12 



Figure 3-8. Power curves for detecting annual trends of 1 % to 3% in the proportion of area with 

 degraded benthic communities based on EMAP-E Louisianian Province data from 

 1991-1994. 



3-23 



