IDENTIFICATION OF THE TOXIC AGENT IN METAL-CONTAMINATED SEDIMENTS FROM MANITOUWADGE LAKE, ONTARIO, USING TOXICITY-ACCUMULATION RELATIONSHIPS IN HYALELLA-AZTECA

Toxicity of sediments from Manitouwadge Lake, Ontario, to Hyalella cor related closely with bioaccumulation of zinc but not copper. Bioaccumu lation in 1-week exposures was sufficient to infer chronic zinc toxici ty. Close similarity between toxicity-accumulation relationships from Manitouwadge Lake and those obtained from zinc-spiked Hamilton Harbour sediments indicate that toxicity is due to zinc itself and not some o ther chemical that correlates with zinc in sediments. Sediment concent rations of zinc, on the other hand, are unreliable indicators of effec ts; toxicity was not highest in sediments from the most contaminated s ite. Copper accumulation was insufficient to cause short-term (1-week) toxicity. Chronic copper toxicity cannot be predicted from bioaccumul ation, but the absence of a significant growth reduction, which is spe cific to copper, strongly suggests that the contribution of copper to chronic toxicity was minimal. Body concentrations of zinc and copper i n wild animals from contaminated lakes (in contrast to laboratory anim als exposed to sediments from those lakes) are not reliable indicators of metal toxicity, either because these amphipods have adapted to con taminated conditions or because they survive in selected microhabitats with reduced metal availability.