SUBLETHAL AND LETHAL TOXICITY OF ALUMINUM-INDUSTRY EFFLUENTS TO EARLYDEVELOPMENTAL STAGES OF THE CRASSOSTREA-GIGAS OYSTER

The toxicity of the effluent from an aluminum plant on Crassostrea gig as oyster embryogenesis (lethal effects) and larval growth (sublethal effects) was tested. Liquid and solid phases of the effluent were sepa rately tested, and effects of mixing during exposure were also evaluat ed. The effluent was highly toxic, causing abnormal embryogenesis at 0 .03 to 1 g 1(-1) and reduced growth at 0.01 to 0.3 g/l. The solid frac tion was markedly more toxic than the liquid fraction. Mixing during e xposure consistently increased both lethal and sublethal toxicity. Con sidering the trace metal content of the effluent, Hg is suspected to b e primarily responsible for the toxicity, although synergistic effects of Al, Fe, and Cr cannot be discarded. Experimental evidence shows th at bioavailable metal species were present not only in the liquid phas e as soluble ions, but most importantly, bound to sediment particles. Based on the present data, uncontrolled disposal of aluminum plant eff luent may be a major hazard to the environment, involving early life s tages and recruitment in marine biota.