Abstract :
The toxicity of Hg2+ [HgCl2], Cr6+(1) [(NH4)2CrO4], Cr6+(2) [CrO3], Cd2+ [CdCl2 · 2,5H2O], Pb2+ [Pb(CH3COO)2 · 3H2O], and As5+ [Na2HAsO4 · 7H2O] on the sensitivity and survival of Daphnia magna and Tubifex tubifex has been studied. All test metals were dissolved and determined under standardized conditions (dilution water, Bringmann and Kühn, 1982) and 96 hr LC50 for T. tubifex and 48 hr LC50 for D. magna were compared in rank orders toxicity. For D. magna rank order toxicity was Hg2+>Cr6+(2)>Cd2+=Cr6+(1)>Pb2+>As5+ and for T. tubifex it was Hg2+>Cd2+>Cr6+(2)>Cr6(1)>Pb2+>As5+. D. magna was a more sensitive organism than T. tubifex and its LC50 values for all metals were several times lower than LC50 values for T. tubifex. Correlation between toxicity of various metals and biological subjects may be useful in predicting toxicity to various biologically important organisms connected with food chains.
