oblique tow (0.333-mm-mesh) is collected biweekly (September - March) to 

 weekly (April - August) . 



Zooplankton Program Evaluation 



The zooplankton studies conducted at Millstone have provided a long 

 time series of data on local zooplankton variability, and temporal and 

 spatial distributions. This information is important in assessing the 

 impact of Units 1 and 2 and serves as baseline data for Unit 3 impact 

 assessment. 



Entrainment data extends back to 1970, and has shown a recurring 

 annual pattern in species composition. Deevey (1956) described winter- 

 spring and summer-fall communities in Long Island Sound which are similar 

 to those found at Millstone. Winter-spring taxa include Acartia hudsonica , 

 Pseudocalanus minutus , Temora longicornis , gastropod eggs and veligers, 

 barnacle nauplii and cyprids, and polychaete nectochaete larvae. The 

 summer-fall community includes Acartia tonsa , Pseudodiaptomus corona tus , 

 and brachyuran and pagurid zoea and megalops. Quantitative estimates of 

 entrainment densities are comparable from 1976 to the present. However, 

 mid 1975 and earlier sample volume estimates are questionable due to 

 poor meter response in the low velocities at the Intake station and 

 quantitative comparisons are not possible (NUSCo 1976). 



The extensive offshore zooplankton program in the 1970's has explained 

 variation in entrainment densities. Some dominant taxa are entrained in 

 greater numbers at night than during daylight (amphipods and mysids) . 

 The day and night, surface and bottom offshore tows indicated an upward 

 migration pattern at night, causing greater entrainment of these organisms 



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