TOXICITY OF COPPER TO CUTTHROAT TROUT (SALMO-CLARKI) UNDER DIFFERENT CONDITIONS OF ALKALINITY, PH, AND HARDNESS

Median lethal concentration (96-h LC50) values for acute copper toxicity to 3-10-g cutthroat trout (Salmo clarki) have been determined for nine different combinations of alkalinity, hardness, and pH. Equilibrium calculations were performed on the copper LC50 values; seven different soluble species of copper were considered: Cu2+, CuOH+, Cu(OH)20, Cu2- (OH)22+, CuHCO3+ CuCO30;, and Cu(CO3)22-. The acute toxicity of copper was inversely correlated with water hardness and alkalinity. At a given alkalinity, hardness determined the LC50; at a given hardness, alkalinity determined the LC50. At a given alkalinity and hardness, the concentrations of the copper species were determined by the pH of the water. Under the conditions tested, Cu2+, CuOH+, Cu(OH)20, and Cu2(OH)22+ were toxic forms of copper to cutthroat trout; CuHCO3+, CuCO30, and Cu(CO3)22- were not toxic. Results of 11 96-h copper toxicity bioassays on 1- to 26-g rainbow trout (Salmo gairdneri) under uniform water chemistry conditions are also reported. © 1979, American Chemical Society. All rights reserved.