Heavy metal toxicity in Exosphaeroma gigas (Crustacea, Isopoda) from the coastal zone of Beagle Channel.

Acute toxicity of copper, cadmium, and zinc on isopod Exosphaeroma gigas was evaluated at 20 per thousand and 30 per thousand salinity. Six concentrations were assayed to estimate effective concentration of the toxicant that affects 50% of tested animal (EC50), while physiological responses and bioaccumulation were determined at 0.42 and 1.95 mg L(-1) of each metal. The following toxicity orders were obtained: Cd>or=Cu>Zn at 20 per thousand salinity and Cu>Zn>or=Cd at 30 per thousand salinity. Copper treatments showed a reduction in oxygen consumption at 30 per thousand salinity, while an opposite trend was observed at 20 per thousand salinity. Zinc caused dissimilar effects, while in cadmium significant reduction was only registered in 0.42(20 per thousand) mg L(-1). Ammonia excretion was generally higher in treatments than control at 20 per thousand salinity. At 30 per thousand salinity, excretion did not change in relation to control or diminished. In general terms, O:N atomic ratios indicated a preponderant protein metabolism. Bioaccumulation of assayed metals was higher at lowest salinity and increased with increasing toxic concentrations.