' \ \ \ \ \ \ % % % % % % % % '^p'f','^c•t','t',•1p^'t^^'t'^<!^^^<^^<>x<>^^ <>;<>;<>; 



Fig. 13. Dendrogram resulting Trom the classification of annual subUdal collections at Millstone subtidal stations 

 September 1979 - June 1987. 



sedimentary changes at EF, we observed reduc- 

 tions in macrofaunal density and species number. 

 The reduced species richness ended the increasing 

 trend evident at this station since 1980. There 

 was also a trend for lowered abundances of 

 Poly cirrus eximius, Aricidea catherinae, 

 oligochaetes, Tellina agilis, Tharyx spp. and 

 Lumbrmeris tenuis. These deposit-feeding species 

 became abundant during 1984 and 1985 following 

 an increase in silt/clay due to construction of the 

 Unit 3 Intake structure and to the completion of 

 the Unit 3 discharge cut (NUSCO 1987). 



Power plant-related impacts were also evident 

 at JC after 3-unit start-up and were evidenced by 

 both sedimentary and infaunal community 



changes. Increased sUt/clay content was observed 

 at this station in September 1986, and was prob- 

 ably due to the transport and settling of sediments 

 scoured from area of the Unit 3 discharge cut. 

 Although the Unit 3 discharge cut was completed 

 in August 1984, the bottom area was not subjected 

 to scour until April 1986, when 3-unit operation 

 began. 



Concurrent with sediment changes at .IC, there 

 was a significant increase in the abundance of 

 Mediomastus ambiseta along with a decline in the 

 abundance of many polychaetes and oligochaetes. 

 Although higher densities of Mediomastus 

 ambiseta, were apparent at other stations during 

 the operational period, increased dominance by 



Benthic Infauna 



111 



