310 HARRISON AND RICE 



glands and stomachs of control animals (Table 3). The highest ^"^Cu 

 concentrations in tissue were in the digestive glands and stomachs of 

 control oysters and in the gills of oysters at 800 and 2400 jug 

 Cu/liter. Although ^'^Cu concentrations in the gills of control 

 animals and of those at 800 /jg Cu/liter were similar after the first 

 hour, concentrations in the digestive glands were more than 20 times 

 higher in the controls than in oysters at 800 /ig Cu/liter. These results 

 indicate that a much greater fraction of the ^ '^ Cu-labeled copper 

 reaching the gills is transported to the digestive glands and stomachs 

 of animals at low rather than high copper concentrations. However, 

 even though the influx of '''^Cu into digestive glands and stomachs is 

 greater in controls, the influx of stable copper is less. The specific 

 activity was 800 times greater in controls than in oysters at 800 fig 

 Cu/liter, whereas the ^"^Cu in digestive glands and stomachs was only 

 20 times greater in control animals than in those at 800 [dg Cu/liter. 

 The accumulation rates of *''*Cu in the soft tissues of oysters 

 decreased with increasing concentrations of copper in the water 

 (Table 3). The average and the maximum amounts of ^'^Cu increased 

 linearly for the first 10 hr at all three exposure concentrations. The 

 average rates of accumulation in the oysters in 1.0 (control), 800, 

 and 2400 ng Cu/liter were 390, 260, and 60 pCi g^' wet weight 

 hr~^, respectively. The maximum rates at all three con- 

 centrations were about 1.7 times the average rates. Since the initial 

 specific activity of the water was known, calculation of the 

 accumulation rates of stable copper was possible. The rates of 

 accumulation (jug Cu/hr) of a hypothetical oyster whose wet weight 

 was 50 g were 0.25 for the control, 32 at 800 jug Cu/Uter, and 23 at 

 2400 Mg Cu/liter. 



DISCUSSION 



The LCj that we obtained for C. gigas at 96 hr (430 jug Cu/liter) 

 is higher than that obtained for many other aquatic species (Becker 

 and Thatcher, 1973) and considerably lower than the 1900 ^g 

 Cu/liter for oysters reported by Fujiya (1960), but it is in the same 

 range as the 500 /^g/liter obtained by Okazaki (1976). Fujiya used a 

 static system and did not determine the final copper concentration in 

 the bioassay water. We found in our preliminary experiments that 

 oysters could remove a significant fraction of the copper from test 

 waters. When the flow rate was 1.5 liters/hr and the copper 

 concentration was <500 /jg/liter, the outflow concentration was 

 about half that of the inflow. When the copper concentration was 

 between 500 and 1200 /ig/liter, the outflow concentration was about 



