556 FORD, FOREMAN, GRUBBS, KROLL, AND WATTS 



Weekly means and ranges of water temperatures in the tank 

 systems, from continuous measurements read hourly, are shown for 

 each control and treatment group. These allow direct comparisons 

 between the temperature regime to which the test animals were 

 exposed and their mortality and survival. Temperature conditions of 

 the station 3 experiment were less severe than those of the station 2 

 experiment, particularly in the degree and range of temperature 

 fluctuations (Table 1). The temperature conditions reflect dif- 

 ferences in thermal plume characteristics and distances from the 

 discharge structure at stations 2 and 3. 



Statistical Evaluations 



Chi-square tests for homogeneity among control and treatment 

 groups were used as the standard method of evaluation. These tests 

 contrasted the total numbers of individuals of each species and size 

 group surviving in the two control systems with the numbers 

 surviving in each of the two effluent treatments at the start of a given 

 time interval (x). Inspection of the life table data and the process of 

 elimination were used to avoid multiple tests, and in almost all cases 

 only one test was applied to a given set of data. 



Separate series of chi-square tests were applied to survival data at 

 the midpoint of the station 2 and station 3 experiments on Sept. 19 

 and at the end of the 14-week experiments on Nov. 7, 1975. The 

 results of these evaluations are discussed in the following sections. 



Evaluation of Control Conditions 



Data shown in the life tables for the control groups suggest that 

 the controls were adequate and provided good conditions for survival 

 of all test species. In the Scripps control groups, percentages of 

 individuals surviving to the end of the experiments ranged from 58% 

 for the smallest size group of K. kelletii to 80 to 100% for all the 

 other species and size groups. The chi-square test comparisons and 

 the process of elimination were used to assess possible differences in 

 the numbers of individuals of each species and size group surviving at 

 the end of the experiments between the generating-station and 

 Scripps control groups. There was a significant difference in survival 

 (P < 0.05) between the two controls in only one case. Survival of the 

 smallest size group of K. kelletii was markedly lower (58%) in the 

 Scripps controls as a result of failure of a seawater system in the 

 Scripps tanks. Final survival values for most of the other species were 

 at least slightly higher for the Scripps controls than for controls in 

 higher temperature water at the generating-station laboratory 

 (Tables 1 to 4). 



