EFFECTS OF THERMAL EFFLUENT 

 ON BENTHIC MARINE INVERTEBRATES 

 DETERMINED FROM LONG-TERM 

 SIMULATION STUDIES 



RICHARD F. FORD, DALLAS G. FOREMAN, KENNETH J. GRUBBS, 



CHERYL D. KROLL, and DONALD G. WATTS 



Center for Marine Studies, San Diego State University, San Diego, California 



ABSTRACT 



Laboratory experiments of 14-weeks duration were conducted to determine the 

 effects of simulated thermal-effluent regimes on survival, grow^th, and body 

 condition of seven motile invertebrate species from shallovir, rocky habitats. 

 Treatment conditions reproduced dynamic temperature regimes measured in the 

 thermal plume of a large generating station in southern California 84 and 355 m 

 from the discharge structure. Cam patterns of field-temperature records w^ere 

 used with time-cycle controllers and pneumatic mixing valves supplied with 

 effluent and ambient-source water to control temperatures in groups of replicate 

 1100-liter tanks. High survival and normal growth and condition of control 

 animals indicated that laboratory conditions were satisfactory. Two sea urchin 

 species (Strongylocentrotiis purpuratiis and S. franciscanus) exhibited relatively 

 low survival and impaired growth and condition in the warmer effluent regime, 

 the effects being most pronounced among large adults. Growth and condition of 

 two asteroid starfish species {Pisaster ochraceus and P. giganteus) were adversely 

 affected by both effluent regimes. Two species of gastropod molluscs (Kelletia 

 kelletii and Roperia poiilsoni), both warm— temperate forms, were relatively 

 unaffected by either of the effluent regimes. Their survival, growth, and 

 condition were not significantly different from controls in most cases. Growth 

 and condition of a third gastropod (Astraea undosa) were adversely affected by 

 effluent conditions, but survival was not. 



Little specific information is available on temperature tolerances and 

 related responses of benthic marine animals affected by thermal 

 effluent on the Pacific Coast of the United States. A number of 

 studies have addressed problems of temperature tolerances, prefer- 

 ences, and effects in fishes and invertebrates (e.g., Norris, 1963; 

 DesVoigne, 1970; Hair, 1971; Vlaming, 1971; Wolcott, 1973; 



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