566 FORD, FOREMAN, GRUBBS, KROLL, ANDWATTS 



This information suggests that both species would be good 

 thermal-indicator organisms for use in field studies. The fact that 

 they are both generally abundant and easily sampled in nearshore 

 areas also enhances their value as indicators. 



Survival of P. ochraceus and P. giganteus was affected very little 

 in simulations of the two thermal-effluent regimes. In contrast, there 

 were evident effects of both effluent regimes on growth and 

 condition of these species. 



Effects on the two sea urchin species were most pronounced 

 among large, adult individuals; this suggests metabolic limitations for 

 asteroid starfish of large size at high temperatures. Effects on 

 survival, growth, and condition also appeared to be somewhat more 

 severe for P. ochraceus than for P. giganteus. 



Survival of the three species of gastropod molluscs apparently 

 was not affected by the station 3 simulation experiment, and there 

 were no effects on A. undosa and K. kelletii of all sizes exposed to 

 the station 2 simulation. Survival of large R. poulsoni and, to a lesser 

 extent, of the two smaller size groups apparently was affected in the 

 effluent regime at station 2. 



Growth and condition of K. kelletii and R. poulsoni were not 

 affected by either thermal-effluent regime, but those of A. undosa 

 apparently were depressed in both simulations. The relatively slow 

 natural growth rates of these species and the short duration of the 

 experiments makes interpretation of these results difficult. 



All three gastropod species are warm— temperate forms abundant 

 in shallow water in southern California and Baja California, Mexico. 

 Roperia poulsoni and A. undosa also occur intertidally. Thus, it is 

 not surprising that they are relatively tolerant of the water 

 temperature conditions to which they were exposed in these 

 experiments. 



Laboratory studies of this kind are always open to question 

 because confinement stress and other artifacts of the experimental 

 system can produce results not representative of natural occurrences. 

 We attempted to duplicate important field conditions, such as water 

 quality, water circulation, space, and natural food supply. The high 

 survival and relatively normal growth and condition exhibited by 

 control animals suggest these aspects of the simulation experiments 

 were successful. The controller system duplicated effluent tempera- 

 tures accurately, exposing the animals to varying temperatures and 

 probably other water-quality conditions similar to those in shallow 

 water at stations 2 and 3. For these reasons, we believe that most of 

 the information obtained on survival, growth, and condition is 

 representative of what would occur at the two field locations we 



