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PECK AND WARREN 



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JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC. JAN. 



1973 1974 



Fig. 3 Nitrate reductase activity at power-plant intake and at the 

 cut on various sampling dates from January 1973 to January 1974. 

 The power plant was not generating from the end of April to the 

 beginning of August 1973. 



DISCUSSIOIM 



Our data suggest that there is no immediate decrease in 

 phytoplankton population as a result of mechanical stresses of 

 entrainment through the power plant. There are indications that 

 phytoplankton are destroyed during passage through power-plant 

 cooling systems, however. Briand (1975) reported large reductions in 

 phytoplankton numbers and volumes at two southern California 

 coastal power plants. Morgan and Stross (1969) and Hamilton et al. 

 (1970) noted large decreases in the chlorophyll a content of cells 

 concomitant v^th decreased primary productivity after entrainment 

 with chlorination. Residual chlorine concentrations of 1.5 to 2.3 

 ppm killed Skeletonema costatum in laboratory cultures, and 

 sublethal chlorine concentrations adversely affected growth (Hira- 

 yama and Hirano, 1970). 



