BIOASSAY - In 1981, continuous effluent toxicity testing of the discharge from MNPS began using 

 populations of sheepshead minnow {Cyprinodon variegatus) and mysid shrimp (Mysidopsis bahia) subjected 

 to undiluted effluent in quany waters and to Jordan Cove water (as a control), both adjusted to constant 

 temperature of about 20 "C. Both organisms have been extensively used in marine toxicity testing and 

 are among EPA recommended test organisms. Because the effluent is primarily condenser cooling water, 

 it has a low potential for toxicity. Potential toxicants that are present in the MNPS effluent include 

 chlorine, heavy metals and hydrazine. 



Sheepshead minnow embryo-larval tests were used to assess acute toxicity of the discharge because 

 the early life history stages of fish are most sensitive to toxicants. Sheepshead minnow life cycle tests were 

 also conducted to assess chronic toxicity by examining egg viability, larval mortality and growth. Parameters 

 examined during Mysidopsis bahia toxicity testing were population growth rates, and reproductive potential. 

 Comparisons were made between animals maintained in undiluted MNPS effluent and Jordan Cove water. 



Results of these studies to date indicate no chronic toxicity related to the MNPS effluent. No 

 differences were found between control and effluent treatments for egg viability, and development and 

 growth of larvae (NUSCo 1983f, 1986c). Effluent toxicity testing will continue during three unit operation. 



SHELLFISH SURVEY - During 1984 and 1985, the abundance and distribution of edible bivalves, 

 hard clams {Mercenaria mercenaria), soft-shell clams {Mya arenaria), eastern oysters (Crassostrea virginica), 

 and bay scallops {Argopectin irradians) was documented. These surveys were conducted in three steps at 

 intertidal and subtidal areas around MNPS to establish a data base for these commercially valuable bivalves 

 prior to three unit operations and to verify the distribution of bivalves in Jordan Cove previously reported 

 in the State of Connecticut Shellfish Concentration Area Maps (NUSCo in prep.). 



Survey results indicated that hard clams were the most abundant and valuable shellfish. In addition 

 to the target species assessed in these studies, the razor clam {Ensis directus) was collected and was the 

 second most abundant species, however, it is not a commercially or recreationally harvested species in the 

 Millstone Point area. Soft-shell clams occurred at lower densities and supported a marginal recreational 

 fishery in Jordan Cove. Only a single eastern oyster was found during the survey; no bay scallops were 

 found in the study area although an important scallop fishery occurs in the Niantic River (about 2 km 

 from MNPS). 



