Ecotoxicology of metals related to freshwater benthos.

The toxicity of Cu, Mn, Mo, Ni, V, As, Pb, Cr, Hg and Sn on the behaviour and survival of benthic worms Tubifex tubifex was studied. All tested metals were dissolved and determined in tap water under standardized conditions. The adverse effects of the metals were evaluated as acute toxicological effects upon exposure expressed as LC50 value with 95% confidence interval. On the basis of the LC50 values, the toxicity of the metals after an incubation for 96 h was ranked as follows: Cu(II)> Cu(I) > V > Hg > or = Mn > Ni > Cd > Cr > Mo > Pb > Sn(IV) = Sn(II) > As. From this sequence it is evident that copper was the most toxic metal ion. In addition, differences were found between Cu(II) and Cu(I) ions toxicity, the former being 2.5 times more toxic. In contrast, no differences could be confirmed between acute toxic effects of Sn(II) and Sn(IV). Arsenic showed the weakest toxicity of the tested metals. The LC50 value for As was 10,000 times higher than those for both copper ions.