EFFECTS OF SIMULATED ENTRAINMENT 



817 



10 11 

 INSTAR 



Fig. 2 Effect of food stress on reproduction of thermally stressed 

 (■) and control (•) Daphnia pulex. Small arrows refer to significant 

 differences among control and test organisms. Large arrow refers to 

 instar when healthy food was reintroduced. 



(Table 6). The reduction noted after combined stress was probably 

 caused by chlorine. 



No significant effects of individual stress on behavior were noted. 



DISCUSSION 



Mechanical stress had the greatest effect on cladoceran survival. 

 This response generally was not in agi'eement with studies of 

 copepods (Lanza et al., 1975, Davies, Hanson, and Jensen, 1976; 

 Heinle, 1976) but agreed with Bunting's (1974) observation that 

 entrainment "crops-off" cladoceran species susceptible to mechanical 

 damage. Fish eggs and larvae also were susceptible to mechanical 

 effects (Ulanowicz, 1975). Ulanowicz discussed the major mechani- 

 cal effects on survival, pressure changes, acceleration, shear stress, 

 and abrasion. All these factors, except pressure changes, would be 



