EFFECTS OF POWER-PLANT OPERATION ON ZOOPLANKTON 



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ASONDJ FMAMJJASONDJFMA 

 YEAR 5 YEAR 6 



(b) 



J J 



Fig. 2 (a) Monthly mean inlet and outlet temperatures, and 

 (b) monthly mean pumping rate and days of each month that power 

 plant was not generating electricity (bar graph), for the Belews Creek 

 Steam Station during the period of study. 



1973 to June 1974) was the first 12-month period that the lake 

 existed at full-pool level. The first unit of the Belews Creek Steam 

 Station commenced operation in year 5 (July 1974 to June 1975), 

 and the second unit went on line in year 6 (July 1975 to June 1976). 

 Zooplankton studies began in year 4. This study compares year 4 

 (control) data with data from years 5 and 6. The year 4 to year 6 

 comparisons give the strongest indication of power-plant effects. 



The discussion in this paper focuses primarily on euphotic-zone 

 data. These data were the most complete and encompass that zone of 

 the lake which is the most important in terms of limnetic trophic 

 level interactions and heat effects. Collections were also taken from 

 the entire water column or the depths below the euphotic zone to 

 ensure that an important component of the zooplankton was not 

 missed because of migration or depth preferences that were deeper 

 than the euphotic zone. This occurred for one species and is 

 mentioned in the text. 



