6-56 



Speaies Density 



Abundance data on the 14 characteristic species identified in 

 Table 6-10 were evaluated for trends over the course of the study via 

 Spearman's coefficient of rank correlation (Conover, 1971). The cal- 

 culated correlation values and their significance levels are presented 

 in Table 5-10. Of the 14 characteristic species, nine show a statistically 

 significant tendency to increase in abundance over the course of the 

 study. 



Because 1977 was identified (see below) as a year of unusually 

 high abundances, the data were re-ranked and Spearman's coefficient 

 recalculated for the 12 collections from 1973 through 1976 only. Of the 

 nine species showing significant increases in density over the entire 

 study, six also showed significant increases from 1973 to 1976, indi- 

 cating that the overall increase in faunal density during 1977 was not 

 the only factor responsible for the trend toward greater densities among 

 ubiquitous species. 



Overall faunal density shows an increase from pre- to post- 

 operational periods. This was examined for significance by seasonally 

 paired t-tests conducted on the faunal density data for all possible 

 combinations of years before and after plant operation. "Years" in this 

 case refers to full years before or after operation and not calendar 

 years. The resulting matrices of t values are shown in Table 6-11. 

 Inspection of these results reveals that there has been no statistically 

 significant change in faunal density at inner harbor stations over the 

 course of the program, although the data do suggest a general increase 

 in density. The only significant change in faunal density involves the 

 Morris Cove data, where faunal densities were significantly higher in 

 1977 than in either 1974 or 1976. Densities were also greater than in 

 1975, although not significantly so. Increases in faunal density from 

 pre operational to operational years at Morris Cove and inner harbor 

 stations is not indicative of a positive Harbor Station impact on the 

 benthic infaunal community. The general harborwide nature of the increase 



