EFFECTS OF SIMULATED ENTRAPMENT 

 ON THE BIOLOGY OF A FRESHWATER 

 CLADOCERAN 



ARTHUR L. BUIKEMA, JR., SARA R. SHERBERGER, 



GREGORY W. KNAUER, LINDA A. NEWBERN, 



JEFFREY T. READING, and JOHN CAIRNS, JR. 



Biology Department and Center for Environmental Studies, Virginia 



Polytechnic Institute and State University, Blacksburg, Virginia 



ABSTRACT 



Under simulated entrainment conditions Daphnia pulex were exposed separately 

 and in combination to temperature (10 and 14^C above 20"C ambient), chlorine 

 (0.35 to 0.50 ppm), and mechanical stress (4 liters/min through a 12.5-mm 

 tube). In a 12-min period, maximum exposure occun-ed for less than 2 min, 

 followed by dilution and/or cooling. After exposure the animals were monitored 

 for mortality, adenosine triphosphate (ATP), metabolism, feeding, growth, 

 molting, reproduction, and behavior. Chlorine and combined stress significantly 

 reduced the levels of ATP. A 14 C stress significantly depressed metabolism. 

 Mechanical stress significantly increased metabolism, and the combined stress 

 had no significant effect on metabolism. Stresses of 10 and 14 C caused a 

 decrease in feeding. Mechanical stress accounted for 30 to 80% acute mortality. 

 Survivors of stress were observed for latent effects. Chlorine reduced growth 

 rates. No significant effects on reproduction were observed when the animals 

 were fed high-quality food. Poor food quality caused a significant reduction in 

 the number and vitality of young produced by females exposed to 10 C stress or 

 to combined stress. There were no significant effects of entrainment on molting, 

 behavior, or long-term survival. 



Electric power generating facilities may use large quantities of water 

 for cooling purposes. During passage through a cooling system, 

 zooplankton populations may be exposed to various combinations of 

 thermal, chlorine, and mechanical stress. The few studies available on 

 entrained zooplankton suggest that the factors affecting zooplankton 

 populations are site specific (e.g., Coutant and Talmadge, 1977). 



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