EFFECTS OF SIMULATED ENTRAINMENT 821 



TABLE 6 



EFFECTS OF ENTRAINMENT 



STRESSES ON THE ATP LEVELS OF 



ADULT Daphnia piilex 



*Significant difference at the 0.05 level. 



filtering rates of the cladocerans. Less food means less young will be 

 produced (Richman, 1958). Thermal stress may also have depressed 

 digestion, assimilation rates, and gonadal functions. Enzyme inacti- 

 vation may be a causal factor. 



Because of its daily intermittent presence in field situations, 

 chlorine was concluded to be less important than mechanical and 

 thermal stress. The effect of chlorine as a major factor in 

 entrainment mortality of zooplankton was varied (see, e.g., Heinle, 

 1976; Lanza et al., 1975; Davies and Jensen, 1975). In this 

 laboratory simulation higher concentrations of chlorine would have 

 been lethal, but concentrations <0.5 ppm were not. The effect of 

 chlorine dose exposure was dependent not only on time but also on 

 the availability of food after exposure. Chlorine significantly reduced 

 the level of ATP of surviving animals, and the mode of action may 

 have been inhibition of carbohydrate oxidation (Green and Stuiapf, 

 1946; Eaton et al., 1973). Chlorine retarded the growth of exposed 

 first instar Daphnia but not of adult animals. This effect may have a 



