Toxicity of copper to cutthroat trout (Salmo clarki) under different conditions of alkalinity, pH, and hardness

Abstract

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: Cu/sup +2/, CuOH/sup +/, Cu(OH)/sub 2/, Cu/sub 2/(OH)/sub 2//sup +2/, CuHCO/sub 3//sup +/, CuCO/sub 3/, and Cu(CO/sub 3/)/sub 2//sup -2/. The acute toxicity of copper was inversely correlated with water hardness and alkalinity. At a given alkalinity, hardness 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, Cu/sup +2/, CuOH/sup +/, Cu(OH)/sub 2/ and Cu/sub 2/(CO/sub 3/)/sub 2//sup -2/ were not toxic. Results of 1196-h copper toxicity bioassays on 1- to 26-g rainbow trout (Salmo gairdneri) under uniform water chemistry conditions are also reported.