Effects of water hardness and salinity on metal toxicity to Daphnia magna Strauss

The effect of salinity (0.3 - 0.45 and 2.45 g.L-1) and hardness (250 - 500 g.L-1 (CaCO3) on the toxicity of Al, Cu, Cd, Ni, Zn and Cr to Daphnia magna has been investigated in laboratory. The concentrations of metals from 0.0 1 to 25 mg.L-1 were examinated. The results obtained at 20 degreesC, show t hat the toxicity, measured at CI50-24 h and CI50-48 h of Cd, Cu, Zn and Al increases with an increase in salinity or hardness. On the other hand, the toxicity of Ni and Cr was affected by the increasing of the salinity. The i ncrease in hardness involves a reduction of chromium toxicity.