Sublethal and lethal toxicity of aluminum industry effluents to early developmental stages of the Crassostrea gigas oyster

The toxicity of the effluent from an aluminum plant on Crassostrea gigas oyster embryogenesis (lethal effects) and larval growth (sublethal effects) was tested. Liquid and solid phases of the effluent were separately tested, and effects of mixing during exposure were also evaluated. 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 fraction was markedly more toxic than the liquid fraction. Mixing during exposure consistently increased both lethal and sublethal toxicity. Considering the trace metal content of the effluent, Hg is suspected to be primarily responsible for the toxicity, although synergistic effects of Al, Fe, and Cr cannot be discarded. Experimental evidence shows that bioavailable metal species were present not only in the liquid phase as soluble ions, but most importantly, bound to sediment particles. Based on the present data, uncontrolled disposal of aluminum plant effluent may be a major hazard to the environment, involving early life stages and recruitment in marine biota.