rapid in the high intertidal of an exposed station and slow in the low intertidal of a shcUered station. 

 Preliminary results from studies re-established during 3-unit operation corroborate those conclusions. 



Growth and mortality studies of Ascophyllum nodosum, a perennial brown alga sensitive to water temperature 

 change, were included in the rocky intertidal sampling program. Tip length analyses helped distinguish 

 between a stressed population at Fox Island and populations at two reference stations. Ascophyllum tip 

 length data, fit to a Gompertz growth function, shows a response to elevated water temperature. 



With the exception of the FE intertidal community, no significant changes to the benthic shore biota were 

 observed that could be attributed to MNPS operation. 



Benthic Infauna 



Intertidal and subtidal infaunal communities in the vicinity of MNPS were sampled during start-up of 

 Millstone Unit 3 and over the first operational year. Power plant-induced impacts were assessed by 

 characterizing communities in tenns of community structure and abundance and comparing these data 

 with those collected before Unit 3 start-up. 



Intertidal infaunal communities exhibited spatial patterns in community abundance and composition and 

 seasonal fluctuations in abundance that were consistent with those observed during the base-line period. 

 Higher infaunal abundances and number of species continued to occur at .lordan C'ove (.IC), while 

 communities at White Point (WP) and Giants Neck (CjN) generally included lower numbers of individuals 

 and species. At the population level, the .IC community continued to be dominated by oligochaetes while 

 Paraonis fulgens, Haploscoloplos fragilis and rhynchococis dominated the WP and GN communities. 



Although spatial patterns among intertidal stations were consistent between pre-operational and operational 

 periods, there were temporal changes in community abundance and species composition evident at all 

 sampling stations. Many of these differences appeared to be continuations of trends which were first 

 evident before Unit 3 operation commenced, suggesting that observed declines were a response to some 

 regional event. At JC, reductions in total abundance and species number were also evident, but they were 

 not as extensive as those at GN and WP. There were, however, unusually low densities of Scolecolepides 

 viridis and Hediste diversic.olor in .lune 1987. Low densities of Scolecolepides viridis were also evident at 

 GN in .lune 1987, indicating a possible area-wide decrease. Sampling intertidal communities during 1986-87 

 revealed no immediate changes to these communities which could be directly attributed to Unit 3 start-up 

 or to 3-unit operations at MNPS. Possible power plant impacts related to temperature could not be 

 assessed in this report, given the limited 3-unit operational period. 



At subtidal stations. Unit 3 start-up resulted in scouring of bottom sediments at Ivfflucnt (EF), located 

 immediately offshore from the discharge cut. Along with sedimentary changes, we observed reductions in 

 macrofaunal density and in particular, number of species. At the species level, lowered abundances of 

 Polycimis eximius, Aricidca c.atherinae, oligochaetes, Tcllina agilis, Tharyx spp. and Lwnhrineris tenuis 

 were recorded and attributed to a reduction in silt/clay content. Power plant-related impacts were also 

 evident at JC after 3-unit start-up and included a substantial increase in silt/clay attributed to the transport 

 and settling of sediments scoured from the area of the Unit 3 discharge cut. Concurrent with this sediment 

 change, there was a significant increase in the abundance of Mediomastus amhiseta along with a decline 

 in the abundance of some previously dominant polychactes Ahcidea catherinae and Polycimis eximius and 

 oligochaetes. The Intake (IN) area also exhibited changes in sediments and infaunal communities during 

 the operational period. Silt/clay values during 1987 were generally lower than those in recent years and 



Monitoring Studies, 1986-1987 



