population densities and difffrences in species composition, it exhibited 

 low similarity to other stations. The linkage of 1983 and 1982 resulted 

 from similarly low densities of Tellina agilis and Exogone hebes, and high 

 densities of Gammarus lawrencianus relative to collections made in 1980 and 

 1981. Within Group II (EF) , low abundances of Chaetozone spp. and 

 Polycirrus eximius , and higher densities of oligochaetes and Caulleriella 

 spp. resulted in the linkage of 1982 and 1983 collections. Lower densities 

 of Lumbrineris impatiens and high densities of Chaetozone spp. were 

 primarily responsible for the linkage of 1982 to 1983 JC collections (Group 

 III). The association among GN sample years was unlike that of all other 

 subtidal stations. Similar population densities in 1981 and 1982 resulted 

 in the coupling of these years, but the high densities observed in 19C0 and 

 the low densities of many species in 1983, caused these sampling years to 

 chain rather than cluster into the group. 



The cluster analysis illustrated high within-station similarity among 

 subtidal communities and the relatively high between- station similarity 

 (except IN). Since 1980, the dominant species comprising the IN community 

 have consistently been different from those found as dominants at other 

 subtidal stations. The remaining stations have consistently exhibited 

 relatively high similarity over the last several years; their separation in 

 1983 was primarily due to variations in the abundance of the few species 

 not to changes in species composition. 



DISCUSSION 



Infaunal communities in the Millstone area are monitored to identify 

 power plant-induced changes in the structure and composition of intertidal 

 and subtidal communities and to evaluate whether any observed changes would 

 significantly alter the local the marine communities. This can only be 

 accomplished if plant-induced changes can be distinguished from those 

 natural temporal and spatial environmental variation which occurs in the 

 Millstone Point area. These factors can strongly influence the structure 

 and composition of shallow water subtidal and intertidal communities 

 (Levings 1975; Maurer et al. 1979; Warwick and Uncles 1980). Given the 

 degree to which natural changes occur, long-term sampling is a necessary 



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