AN IN SITU STUDY OF CADMIUM STRESS 



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10 20 30 40 10 20 30 40 10 20 30 40 



CADMIUM, Aig/iiter 



Fig. 1 Effects of cadmium on rate of increase, r, of (a) cyclopoid 

 copepods, (b) calanoid copepods, (c) cladocerans, and (d) large 

 rotifers. 



The mean numbers of nauplii, several rotifer species, and one 

 large protozoan in the samples for experiment 5 are shown in 

 Table 2. The effect of added cadmium on the large rotifers is shown 

 in Fig. 1(d) by the linear regression equation and the corresponding 

 line fitted through the average rates of increase, r, for the large 

 rotifers in experiment 5. The apparent cadmium sensitivity of these 

 rotifers, as indicated by the slope of the line, is comparable to that 

 of calanoid copepods. Differences among mean numbers of Cera- 

 tium hirundinella in incubated controls and unincubated samples 

 indicated a pronounced effect of enclosure on this protozoan. The 

 mean numbers remaining in incubated samples containing different 

 levels of added cadmium were not significantly different from the 

 controls (Table 2). 



The effects of cadmium on structural attributes of the crustacean 

 zooplankton community are exemplified by decreases in total 

 abundance, relative abundance of the major groups, species diversity, 



