Species Per Station 



2 

 The number of species per station (0.1m ) ranged from 5 to 86 with 



a mean of 33.1 (Table 8). The offshore stations consistently had the 



highest numbers of species and moderate numbers are characteristic of 



lower Casco Bay. Less than 20 species were found at many of the 



finer -grained stations and in the wood chips of station 36. Indeed, 



stations 17, 32, 35, 36 and 43 were occupied by less than 10 species 



(Fig. 27). 



The number of species per station is very strongly correlated 

 (99.9% level) with increasing depth (Fig. 28). It is also negatively 

 correlated at the 99.9% level with mean grain size and organic carbon 

 (Figs. 29 and 30). Number of species is the only biological parameter 

 to be significantly correlated with salinity (98% level) . 



As with density and biomass, species per station is negatively 

 correlated with each of the metals. Two of these relationships, cadmium 

 and zinc, are significant at the 99% and 95% levels, respectively. 

 Other non-significant correlations and their significance levels are: 

 chromium 94%; nickel 93%; copper 82% and lead 75%. 



Diversity 



Informational diversity, as measured by the Shannon index, ranged 

 from 0.415 at station 32 to 4.347 at station 10 (Table 8). The overall 

 mean was 2.72. High values of H' diversity are found at some offshore 

 stations and generally throughout the Portland region including the 

 trace metal impacted, low density stations 18-20 (Fig. 31). An 

 explanation for this unusual result can be found in an examination of 

 evenness and species richness levels (Table 8). In general, the high 



