Abstract:The acute and chronic toxicity of mercury, copper, cadmium andchromium to the survival, growth, reproduction and the intrinsic rate of increase(rm) of M. mongolica were studied. The 48 hr LC50 of Hg2+ Cu2+, Cd2+ andCr(6) was 0.0034, 0.0888, 3.89 and 4.24 mg/l respectively. The toxicity ofcombined different metals to the organism was also studied. The result reveals thatthe toxicity of mixtures of two metals was much stronger than the single one (ex-cept Hg/Cu). While the toxicity of three or four metals combination was lower thanthat of two metals.