Of all subtidal conununities sampled, that of IN was most unique, with four 

 of its top ten numerical dominants were abundant only at this station. 



Generally, the dominant organisms during 1983 were the same as those 

 observed in past years; at all stations, over 50% of the dominant taxa in 

 1983 were among the overall top ten from 1980-82 (7 of 10 at EF, 6 of 10 at 

 GN and IN, and 9 of 10 at JC) . In nearly all cases, species that were 

 added or replaced as dominant in 1983 were of low abundance relative to 

 organisms consistently found as dominants. 



The major change in the taxa dominating subtidal communities was the 

 appearance of Polydora caulleryi among the top ten at EF, GN , and JC. At EF 

 and GN, this taxon was not among the top ten in any of the previous three 

 years. At JC, densities of this species averaged 1/core from 1980-82, but 

 increased to 21/core in 1983. Other compositional changes in 1983 included 

 lower densities of Chaetozone spp. at EF and GN, lower densities of 

 Polycirrus eximius at EF and lower densities of oligochaetes at GN. At IN, 

 Ampelisca verrilli was unusually abundant in 1983, relative to the previous 

 three years. A notable reduction in the abundance of Mediomastus ambiseta 

 occurred at JC, where it averaged 5/core in 1983 compared to 26/core over 

 the last three years. The three year BIV of 56.3% reflected the typical 

 year-to-year fluctuations in density of this species of the the last three 

 years . 



Trophic Structure 



Feeding types of the dominant subtidal organisms were examined to 

 evaluate any observed differences in subtidal community composition between 

 stations and years reflected changing food resources. In 1983, the top 

 three dominant organisms at EF', GN, and JC were surface deposit-feeders 

 while at IN, a suspension feeder was most abundant (Table 8). This 

 type of trophic structure, and the differences among stations were 

 consistent with observations made during the last six years. Bottom 

 deposit -feeding species have charactertically more abundant at JC, 

 suspension feeders at EF and particularly IN, and omnivores at GN . The 

 relative constancy in trophic structure reflects the general stability in 

 species composition of the Millstone subtidal communities and no major 

 shifts have occurred at any subtidal station the last six years. 



35 



