Keywords: 
• Neocaridina denticulate /
• Cu²⁺ /
• chlorpyrifos /
• toxicity response

Abstract: We investigated the response of aquatic organisms to heavy metals and organ-phosphoruspesticide in waters.We exposed Neocaridina denticulate to Cu²⁺,pure chlorpyrifos solution and a 1:1 compound toxicity solution.We evaluated the comprehensive toxicity using the additive index method.The single toxicity tests showed that chlorpyrifos had significantly higher toxicity to N.denticulate than Cu²⁺(p<0.01).The Cu²⁺concentrations for which we observed no effect on N.denticulate(no observed effect concentration,NOEC)and for which we observed the lowest effect(lowest observed effect concentration,LOEC) were 1.78 mg·L^-1,2.40 mg·L^-1,respectively.The LC₅₀ of 24 h,48 h,72 h and 96 h were 6.41 mg·L^-1,4.75 mg·L^-1,420 mg·L^-1 and 3.44 mg·L^-1,respectively.For chlorpyrifos,the NOEC and the LOEC were 0.04 μg·L^-1,0.07 μg·L^-1,respectively,the LC₅₀ of 24 h,48 h,72 h and 96 h were 035,0.17,0.11 and 0.06 μg·L^-1,respectively.According to fish toxicity grading standards,Cu²⁺ was highly toxic to N.denticulate while chlorpyrifos was virulent.The comprehensive toxicity tests showed that the joint toxicity of Cu²⁺and chlorpyrifos was synergistic when the toxicity was 1:1 at 24 h,48 h,72 h and 96 h,and the addition index(AI) were 0.02,0.45,1.86 and 223,respectively.This study provided a scientific basis for preventing water pollution and conserving aquatic diversity.