as dominant species at both stations. The presence of sedentary 
deposit feeding polychaetes like Pista and Polycirrus at the NL-85 
station indicated that the substrate was relatively stable and that 
fine grained organic matter was available. 
Ampelisca vadorum dominated both stations in terms of 
numbers (Table 3-8), making up 47% and 91% of individuals at the 
NL-85 station and the Reference station, respectively (Tables 3-10 
and 3-11). Ampelisca dominated the Reference station physically; 
the fine sand substrate was covered with a continuous mat of 
amphipod tubes of all sizes. All co-occurring species must live 
on or under this mat and deal with the suspension feeding 
activities of the amphipods. The time of year contributed to this 
high density; as young adults and juveniles of the overwintering 
generation which were born during the late summer and early fall 
had not yet suffered losses from predation and winter storms. Most 
of the Ampelisca were 1-2mm long and 63% passed through a 1mm 
sieve. 
The total number of species recovered from both stations 
(112, Table 3-11) was large for the small number of samples taken. 
The total was increased by the fact that two contrasting habitats 
were sampled. Sixty-five species were recovered from a single 
sample at NL-85. The species number per sample was also high (mean 
of 55 at NL-85, 52 at Reference). This level is typical of shallow 
shelf waters, such as Rhode Island Sound and Massachusetts Bay, but 
is higher than the 25 or 30 species normally found in Southern New 
England estuaries. 
The benthic community was also characterized in sediment 
samples collected at the NL-85 disposal mound and the Reference 
station in July 1986. The sieve residues from the Reference 
station samples consisted of 1,500-2,200 cm? of coarse gray sand, 
pebbles, shells, and both large and small ampeliscid amphipod 
tubes. The shells were weathered and belonged to species normally 
found in offshore habitats. Sieve residue volume from the NL-85 
mound ranged from 250-380 cm? and contained coarse gray sand and 
many small ampeliscid amphipod tubes. These residues were quite 
visible in the sediment samples prior to sieving on the research 
vessel (Table 3-12). 
Following preservation and storage of the benthic 
samples, the shells of small individuals of several species of 
gastropods had dissolved in the preservative. In most cases, 
species were recognizable by comparison of soft parts and operculae 
with intact specimens. In several cases, very small or fragmented 
organisms were identified by reference to the archived 1985 
samples. 
The species at both the Reference and NL-85 mound 
stations were distributed relatively evenly among the major taxa. 
Individuals were distributed evenly among taxa at the Reference 
29 
