these smaller forms would suffer mortality during winter storms and 

 summer predation. 



More than half of the individuals in samples 10, 11, and 

 12 were the amphipod Ampelisca agassizi . The bivalve Nucula 

 annulata made up a similarly high proportion of individuals in 

 samples 1 and 2. The small polychaete Prionospio steenstrupi was 

 numerically important in habitats suitable for Aj_ agassizi . 



Most of the major taxonomic groups were well represented 

 in these samples. Polychaetes were dominant in number of species 

 (73) and also had the largest number of individuals. There were 19 

 species of amphipods and 16 species of bivalves, with one very 

 abundant species in each group. The number of species (3) and 

 individuals (14) of gastropods were relatively small. 



Inspection of counts for dominant and subdominant species 

 indicated that groups of species could be categorized according to 

 their association with other species and their abundance in a given 

 habitat type (Table 3-4) . Some species listed in Table 3-4 had 

 their highest density in one habitat. Most other relatively 

 abundant species were found in a combination of habitats; very few 

 were ubiquitous. 



The response of Ampelisca agassizi to historic disposal 

 activities is of special interest, because dense populations have 

 the potential to determine the makeup of the remaining community 

 and to modify sediment grain size distribution as well as the 

 boundary layer oxygen profile. The presence of large numbers of A. 

 agassizi on disposed sediment at stations 3 and 10 indicated that 

 this species can colonize dredged material which was physically 

 suitable (i.e., not silt or mobile sand). 



Several species with greatest density on silty bottom may 

 be indicators of disturbance. Capitella capitata and genus 

 Polydora species are known to be adapted to high levels of organic 

 matter and low oxygen and to be resistant to physical and chemical 

 stresses. Cossura longocirrata has been found on other offshore 

 disposal areas. 



With the exception of sample 7, all samples supported 

 large numbers of polychaetes, amphipods, and thin-shelled bivalves 

 which are eaten by fish, crabs, and lobsters. Most of the 

 polychaetes and ampeliscid amphipods present were of a size range 

 eaten by juvenile rather than adult fish. 



It appears that the unreplicated samples taken during 

 this survey provided a good description of the benthic community of 

 Rhode Island Sound in the vicinity of the historic disposal site. 

 Replication within stations would have given no more information 

 than was obtained; conditions can change on the scale of meters 

 between ripple marks on the disposal mound, as well as vary 



11 



