312 HARRISON AND RICE 



concentrations in the waste at the point of discharge (before 

 dilution) and do not indicate the fraction that might have been in a 

 toxic form. A year-long survey at a single Pacific coastal power plant 

 showed copper values in the intake and discharge waters to vary from 

 0.1 to 5.8 jug Cu/Uter (Dorband et al., 1976). These values are in 

 contrast to the 1800 /.ig Cu/liter (before dilution) discharged in the 

 initial surge of water from the cooling system during startup at 

 another power plant (Warrick, Sharp, and Friedrich, 1975). Until 

 recently the California State Water Resources Control Board per- 

 mitted concentrations in discharges of 200 jug Cu/liter for half a 

 month and 300 /jg/liter for 10% of a month (California State Water 

 Resources Control Board, 1972). Based on an analysis of acute 

 toxicity, chronic toxicity, and reported seawater concentrations, the 

 board has proposed amendments to the water quality control plan 

 for ocean waters of California which have a water-quality objective 

 of 5 jug Cu/liter in the receiving water (Klapow, 1978). This objective 

 should adequately protect adult oysters because the estimated 

 incipient lethal concentration for adults is 230 /ig Cu/liter. 



Organism mortalities resulting from heavy metals may be caused 

 by (1) excessive amounts of a metal in tissues, (2) excessive rates of 

 influx into tissues, or (3) inhibition of a vital metabolic process. In 

 the first case, if the influx of copper into an organism is greater than 

 its efflux, increased levels result; lethal amounts may accumulate in 

 all tissues or in a special storage depot. We tested for the first 

 possibility by copper analyses on the experimental animals and for 

 the second possibility with ^"^Cu-uptake experiments. 



The results of copper analyses on test oysters show that the 

 highest concentrations of copper were in oysters at 230 idg Cu/liter 

 rather than at the higher concentrations in seawater. Also, levels of 

 copper in oysters held in water containing more than 230 [dg Cu/liter 

 did not increase with increasing concentrations in the water but were 

 relatively constant. The duration of exposure was not always the 

 same for oysters held at the same and at different concentrations, 

 however. For example, exposure for oysters in water containing 

 440 iUg Cu/liter ranged from 3.9 to 8.3 days. The concentrations in 

 this group of animals did not increase consistently with increased 

 exposure. The durations of exposure and the tissue concentrations 

 (Cu/g wet weight) were: 3.9 days, 37.4 /ig; 4.2 days, 48.8 jUg; 5.2 

 days, 92.1 and 86.5 Mg; 5.9 days, 82.5 Mg; 6.0 days, 77.6, 90.4, and 

 107 fxg; 6.5 days, 48 jug; and 8.3 days, 68.2 fig. At 230 fig Cu/liter, 

 the two animals that died at 8.8 and 9.4 days contained 60.0 and 

 96.0 /ig Cu/g wet weight, respectively. Copper may be lost from 

 animals near death as a result of permeability changes. The hearts of 



