Effects of calcium and magnesium hardness on acute copper toxicity to juvenile channel catfish, Ictalurus punctatus
1999
Perschbacher, P.W. | Wurts, W.A.
Two experiments were conducted to evaluate the effects of calcium or magnesium hardness on the acute toxicity of copper sulfate to juvenile channel catfish (Ictalurus punctatus) in low alkalinity environments. A preliminary bioassay determined the 48-h LC(50) of copper sulfate to be 1.25 mg l(-1) for juvenile catfish placed in water with calcium hardness and total alkalinity set at 20 mg l(-1) CaCO(3). In the first experiment, catfish were exposed to 1.25 mg l(-1) copper sulfate in environments where calcium hardness was varied from 10-400 mg l-(1) CaCO(3). Total alkalinity was 20 mg l(-1) CaCO(3). As calcium hardness increased, copper-induced catfish mortalities decreased significantly from 90% at 10 mg l(-1) CaCO(3) to 5% at 400 mg l(-1) CaCO(3). In the second experiment, catfish were exposed to 1.25 mg l(-1) copper sulfate in environments containing either calcium or magnesium hardness, 20 and 400 mg l(-1) CaCO(3), with total alkalinity set at 20 mg l(-1) CaCO(3). Survival rates in calcium hardness treatments were consistent with those in the first experiment. However, 100% mortality was observed in both treatments containing magnesium-based hardness. These data suggest a calcium-specific mechanism with respect to acute copper toxicity in channel catfish.
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