6-26 



5-2) were generally i^resent in low frequencies at Morris Cove stations 

 and, in the inner harbor, were only present in greater than 25% of the 

 samples from a small group of stations. Greatest frequency of occur- 

 rence for oligochaetes was at Station D, where they were present in 56% 

 of the samples. Gemma gemma reached frequencies of greater than 25% 

 only at four stations in the inner harbor, while Nassarius trivittatus 

 was present at low levels at both inner harbor and Morris Cove stations 

 (Figure 6-2) . Abundances and station occurrences of oligochaetes and 

 Gemma were variable over the study period. Nassarius was usually pres- 

 ent at low average densities, though at a variable number of stations 

 (Figure 6-4) . 



Species Richness 



The total number of species at a station is often one of the 

 more conservative characteristics of a community and, as such, varia- 

 tions from the norm may serve as an indicator of community stress. This 

 parameter, however, does not necessarily relate to community stability 

 (May, 1973) . The total number of species for each station over all 

 samplings is presented in Table 6-5. These values reflect total species 

 present at a station and are not the mean of the replicates. Direct 

 comparisons among data from the three levels of sampling intensity (R&M 

 pre-1975; R&M post-1975; and NAI) , are not legitimate. 



An interesting and somewhat perplexing phenomenon of the New 

 Haven benthic system is a precipitous drop in species richness and 

 faunal density at certain stations during the peak of the summer. The 

 "August effect" was tentatively first proposed by Rhoads and Michael 

 (1975) and subsequently developed and modified in following reports 

 (Rhoads and Michael, 1977, 1978). The occurrence of this phenomenon 

 is fairly well documented in the R&M data although it is apparently not 

 exhibited at some stations and the actual causes appear to be more 

 complex than first proposed. 



