EFFECTS OF THERMAL EFFLUENT 547 



Ulbricht, 1973; Wolfson, 1974; Adams and Price, 1974; Jennison, 

 1975; Brewer, 1976; Lockheed, 1977). Much can be learned about 

 the general biological effects of thermal effluent from well-designed 

 field sampling and experimentation, but laboratory simulation 

 studies are often necessary to provide detailed information. This is 

 particularly true for motile invertebrate species, which cannot be 

 followed easily in the field by sequential sampling to determine 

 survival, growth, and condition of individuals. 



This paper describes long-term simulation experiments to deter- 

 mine the effects of thermal effluent from a large electric generating 

 station on seven ecologically important species of motile, benthic 

 invertebrates. Combined effects of temperature and other water- 

 quality characteristics of the effluent were evaluated. The species 

 studied are the echinoid echmoderms Strongylocentrotus purpuratus 

 and S. franciscanus (grazers), the asteroid echinoderms Pisaster 

 ochraceus and P. giganteiis (carnivores), and the gastropod molluscs 

 Astraea iindosa (grazer), Kelletia kelletii (carnivore), and Roperia 

 poulsoni (carnivore). Representative juvenile and adult size groups of 

 each species were maintained in large tanks provided with flowing 

 seawater. The survival, growth, and condition of control groups 

 maintained both in generating-station intake water and ocean water 

 at ambient temperatures were used as standards against which to 

 compare characteristics of two treatment groups held in thermal- 

 effluent regimes. The treatment conditions simulated temperatures 

 and chemical conditions experienced by animals at two representa- 

 tive locations in the thermal plume. 



MATERIALS AIM D METHODS 



A detailed description of the primary laboratory at which these 

 studies were conducted is given by Ford et al. (1976). The laboratory 

 is located at a large, fossil-fueled generating station on the coast near 

 Los Angeles, Calif. Characteristics of operation and of the thermal- 

 effluent seawater dischcirged from this plant are similar to those of 

 other electrical generating stations along the southern California 

 coast (Adams, 1969). 



Separate laboratory supply systems provided thermal-effluent 

 seawater and seawater of ambient temperature from a cooling-water 

 intake of the generating station. Filtered water from these sources 

 was supplied to all parts of the laboratory through polyvinyl chloride 

 lines. 



One group of controls was maintained at ambient ocean 

 temperature in a laboratory at the Scripps Institution of Oceanog- 



