562 FORD, FOREMAN, GRUBBS, KROLL, AND WATTS 



for normal growth of the three gastropod species. The short 

 experimental period probably accounted for the relatively small 

 increases in weight and length observed, particularly among large 

 individuals. 



Echinoderms 



That growth and condition of both Strongylocentrotus species 

 were adversely affected by conditions in both simulation experi- 

 ments is indicated by comparisons of growth increments of control 

 £ind treatment groups (Table 5). Effects were evident for all size 

 groups of S. franciscanus, which exhibited marked decreases in mean 

 test diameter in both thermal-effluent experiments. Such "negative" 

 growth has been observed in natural populations of sea urchins 

 (Ebert, 1967). Results of analyses of covariance and multiple range 

 tests indicated that growth rates for all size groups of the two 

 Strongylocentrotus species were significantly lower in both effluent 

 regimes than in the Scripps and generating-station controls 

 (P < 0.05). The depressive effect on growth of the smallest size 

 group of S. purpuratus in the station 2 experiment is indicated 

 clearly by the growth plots in Fig. 1. Loss of spines and failure to 

 hold the spines erect were common among individuals of the larger 

 size groups of both species exposed to effluent. These effects were 

 also observed among large individuals of both species near station 2 

 in the field during the period of warmest water in late summer and 

 early fall. None of the individuals in the Scripps and generating- 

 station controls exhibited these effects. 



There was similar evidence of effects on growth and condition of 

 the two Pisaster species. Mean weights and volumes of the largest size 

 group of P. ochraceiis declined under both station 2 and station 3 

 effluent conditions (Table 5). In contrast, weights and volumes for 

 all three size categories of P. giganteus increased under both 

 treatment conditions. Results of analyses of covariance and multiple 

 range tests indicated that increases in weight for all Pisaster size 

 groups were significantly lower in both simulated effluent regimes 

 than in Scripps and generating-station controls (P 0.05). The 

 adverse effects appeared to be somewhat more severe for 

 P. ochraceiis than for P. giganteus. 



Gastropod Molluscs 



Data for all size groups of K. kelletii indicate that their growth 

 and condition were not adversely affected by either simulation 

 experiment (Table 5). Weight and W/L values for all three size groups 



