EFFECTS OF SIMULATED ENTRAINMENT 



811 



4 6 8 



TIME, min 



10 



12 



14 16 



Fig. 1 Time course for thermal, chlorine, and mechanical stresses 



applied to Daphnia pulex. Temperature, . Chlorine, . 



Pumping, O. 



exposed separately and in combination to temperature, chlorine, and 

 mechanical stresses. The Coutant model for time of exposure to 

 various stresses was as realistic a choice as any model designed for a 

 specific power plant would have been. Coutant (1970; 1974) said 

 that the details do vary among power plants. The effects of pressure 

 were not studied because Beck, Poje, and Waller (1975) demon- 

 strated that survival of larger crustaceans was not significantly 

 affected by pressure changes. After exposure, survival, oxygen 

 consumption, growth, molting, filtering rate, reproduction, adeno- 

 sine triphosphate (ATP), and behavior were monitored. Unless 

 otherwise noted, animals were held and studied at 20° C after 

 exposure. Although most studies were conducted with adult Dap /in /a 

 (8 day), some experiments were made with first instar organisms. 



With different temperature water baths, thermal stress (10 and 

 14°C above ambient, 20°C) was applied within 1 min and maintained 

 for 8 additional min (Fig. 1). After 9 min, the temperature was 

 cooled to ambient over a 3-min period. Total thermal exposure was 

 12 min. These thermal stresses were selected as realistic estimates of 

 the temperature changes that would occur for entrained summer 

 populations of cladocera. Maximum summer populations of most 

 cladocera occur at temperatures near 20° C. 



Chlorine, introduced as calcium hypochlorite, was monitored 

 with an Amperometer Titrator (Wallace & Tiernan Division, Pennwalt 



