558 FORD, FOREMAN, GRUBBS, KROLL, AND WATTS 



Gastropod Molluscs 



Conditions of the station 2 and station 3 experiments had no 

 evident effects on survival of K. kelletii. Results of chi-square tests 

 indicated there were no significant differences in survival (P > 0.05) 

 between control and treatment groups for any size group at the 

 midpoint or at the end of the experiment. Survival of the smallest 

 treatment size group was 84% at the end of the station 2 experiment, 

 and for all other treatment groups survival was 96 to 100%. 



TheiTnal effluent had no apparent effect on survival of 

 R. poulsoni in the station 3 experiment; final survival of the 

 treatment groups ranged from 92 to 100%. Results of chi-square tests 

 on these data indicated no significant differences (P > 0.05). In the 

 station 2 experiment, however, the largest size group had markedly 

 lower survival (52%) than did the controls at the end of the 

 experiment. Results of chi-square tests indicated that survival of this 

 group was significantly lower (P < 0.05) than that of either 

 corresponding control group at the end of the experiment but not at 

 the midpoint (P > 0.05). Survival of the smaller two size groups was 

 also moderately low (72 and 76%) in thermal effluent at the end of 

 the experiment, but the results of chi-square tests and the process of 

 elimination indicated that survival of these treatment groups was not 

 significantly different from that of either corresponding control 

 group (P> 0.05). 



Astraea undosa of all sizes exhibited high survival in both the 

 station 2 and station 3 experiments, with final values ranging from 

 88 to 100%. Results of chi-square tests at both the midpoint and the 

 end of these experiments indicated that there were no significant 

 differences in survival between the effluent-treatment and the 

 control groups (P > 0.05). 



Effects of Thermal Effluent on Growth and Condition 



Mean values of linear size, weight, volume, and a measure of 

 body condition for Scripps control and effluent-treatment groups at 

 the start and end of both simulation experiments are shown in 

 Table 5. The change between each of the initial and final mean values 

 (A) and the numbers of individuals on which the means were based 

 (N) are indicated. The ratio of wet body weight to linear size (W/L) 

 was used as a somewhat arbitrary but standard indication of body 

 condition, like the relationship W/L^^ used in fisheries studies. For 

 Pisaster, separate weight and volume determinations were used to 

 assess condition because no accurate, linear measurements could be 

 made. 



