NITRATE REDUCTASE ACTIVITY 

 AND PRIMARY PRODUCTIVITY 

 OF PHYTOPLANKTON ENTRAINED 

 THROUGH A NUCLEAR POWER STATION 

 ON NORTHEASTERN LONG ISLAND SOUND 



BRADFORD B. PECK* and R. SCOTT WARREN 



Department of Botany, Connecticut College, New London, Connecticut 



ABSTRACT 



The effects of temperature and various concentrations of chlorine on nitrate 

 reductase activity and primary productivity of phytoplankton were studied at 

 the Millstone Nuclear Power Station on northeastern Long Island Sound. During 

 August the ambient temperature at the cooling water intake ranged from 19.5 to 

 20 C. Power generation during this period resulted in temperature increases of 

 11 and 14 C at the discharge and depressed phytoplanktonic nitrate reductase 

 activity by 88 to 89% and phytoplanktonic primary productivity by 42 to 52%. 

 The decrease occurred during the 6- to 9-hr transit through the cooling pond. 

 Nitrate reductase activity, maximally depressed after exposure to a mean 

 increase of 13 C above ambient temperature on seven days in August, did not 

 recover to intake control levels after 24 hr of incubation at ambient intake 

 temperature. In March and April, when the ambient temperature of Long Island 

 Sound water was 4.3 to 9.9 C, phytoplanktonic nitrate reductase activity was 

 stimulated 25% above that of controls after 6 to 9 hr of exposure at 11.5 to 

 18.1 C above ambient temperature. The productivity results are similar to 

 previous unpublished findings on temperature influence at this site. The nitrate 

 reductase activity findings support the hypothesis that nitrate reductase is a 

 heat-labile enzyme. Chlorine concentrations below and above those required to 

 eliminate fouling organisms (0.50 ppm) produced large decreases in the 

 photosynthetic rate of entrained phytoplankton. Previous work at this site 

 reported similar findings. Nitrate reductase activity decreased 15% at 1.0 ppm 

 and 1.2 ppm, the two highest chlorine dosages applied. 



♦Present address: Peaks Island, Maine. 



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