6-15 



limited stress in an otherwise similar estuary, crustaciians are> well 

 repreuenteci. 



Based upon the raw frequency-of-occurrence data and the spe- 

 cies groups generated by the classification analysis, a group of species 

 considered to be characteristic of the benthic infauna of New Haven 

 Harbor was developed (Table 6-4) . In order to qualify for inclusion, a 

 species had to be either ubiquitous or dominant. A ubiquitous species 

 was considered to be any species present at 20 or more of the 26 sta- 

 tions at some time over the four years of the combined programs. Dom- 

 inant species were those which were among the top five at a station in 

 terms of frequency of occurrence. 



In most cases, species which were ubiquitous were also domi- 

 nant at one or more stations. Every species which was important to the 

 determination of station groupings also qualified as ubiquitous. This 

 indicates that, in this study, the abundance data of the particular 

 component species were critical to the identification of station clus- 

 ters: presence/absence data would not have allowed detection of the 

 clusters. The fact that only 14 species qualified as either ubiquitous 

 or dominant is further support for how unrepresentative most of the spe- 

 cies were. 



Frequencies of occurrence based on all samples from a particu- 

 lar station are plotted on charts of New Haven Harbor for 10 of the 4 

 ubiquitous species identified above (Figures 6-2 and 6-3) . Crangon 

 septemspinosa , and Neomysis americana, Nucula proxima and Pagurus longi- 

 carpus are not shown because of their consistently low frequency of 

 occurrence. Several distinct distribution patterns in the harbor can be 

 seen from these time-averaged distributions. Among the polychaetes, the 

 dominant and widespread group in all areas of the harbor. Nereis succinea 

 and Streblospio benedicti were most ubiquitous (Figure 6-2) . Nereis was 

 most common at inner harbor stations 6 and 10, where it occurred in 69% 

 and 81% of all samples, respectively, and was also abundant in the 

 coarser-grained Morris Cove samples where it was present in more than 



(Text continued on page 6-21) 



