EFFECTS OF THERMAL EFFLUENT 557 



Echinoderms 



Results of the chi-square tests for all size groups of S. purpuratus 

 indicated that survival was significantly lower (P < 0.05) in the 

 station 2 treatment group than in either of the controls (Tables 1 and 

 2). Uniform results were obtained for both the midpoint and the end 

 of the experiment. In contrast, the results of chi-square evaluations 

 for S. purpuratus of all sizes in the station 3 experiment (Tables 1 

 and 2) showed no significant differences in survival between 

 treatment and control groups (P > 0.05) at either the midpoint or 

 the end of the experiment. These differences in survival are reflected 

 clearly in the life tables. Apparently temperatures in the station 3 

 experiment were mild enough to have little effect on the survival of 

 any of the three size groups; there was 92 to 96% survival at the end 

 of the experiment. In contrast, survival of the largest size group of 

 S. purpuratus at the end of the station 2 experiment was only 30% 

 and of the smallest and intermediate size groups, 40% and 60%, 

 respectively. 



Strongylocentrotus franciscanus in the station 2 experiment 

 showed even poorer survival, ranging from 20% for the largest 

 (Table 3) to 44% for the smallest size group at the end of the 

 experiment. Results of chi-square tests for S. franciscanus of all sizes 

 in this experiment indicated that survival was significantly lower 

 (P < 0.05) in the treatment group than in either of the controls. 

 There were no significant differences in survival between the control 

 and treatment groups in the station 3 experiment (P > 0.05). 



Pisaster ochraceus and P. giganteus of all sizes showed relatively 

 high survival in both effluent-treatment groups. Results of all 

 chi-square tests comparing both species in both experiments showed 

 no significant differences (P > 0.05) among the effluent-treatment 

 groups and either of the control groups. These results were the same 

 for the midpoint and the end of both experiments. The largest size 

 group of P. ochraceus (525 to 825 g body weight) was omitted from 

 the station 3 experiment because few individuals of that size could 

 be found in the study area during the period of stocking. 



Survival of P. ochraceus (Table 4) was only slightly lower in the 

 station 2 treatment groups (80 to 88% at the end of the experiment) 

 than in station 3 treatment groups (84 to 92%). Survival of 

 P. giganteus in the station 2 treatment groups ranged from 92 to 

 100%, and that of the station 3 treatment groups ranged from 96 to 

 100%. This suggests that survival of all size categories of both species 

 was at most only slightly affected, with P. ochraceus showing 

 somewhat greater evidence of possible adverse effects. 



