| The polychaete Nereis diversicolor is an ecologically keystone species of invertebrate thatlives in the mud of sea-land interface environment. In this work, eco-toxicological effects of singleand joint pollution of Cd,Cu and petroleum hydrocarbons on Nereis diversicolor were investigated,aimed to discuss toxic mechanisms from the point of the pollution eco-chemistry, to seek sensitivebiomarker to evaluate contamination of metals and petroleum hydrocarbons in estuarine ecosystems,and to provide theoretical references for water monitoring, pollution-ecological diagnoses andenvironmental management of aquatic ecosystems.In the exposure course of acute toxicity, potential toxic effects of Cd, Cu and petroleumhydrocarbons on Nereis diversicolor were explored and their toxicity could be in the sequencepetroleum hydrocarbons＞Cu＞Cd. Joint toxic effects of these three pollutants on Nereis diversicolorwere complicatedAChE activity was inhibited, exposed to Cd and Cu, but the rate of inhibition was less than50%. However, exposed to petroleum hydrocarbons, AChE activity of the animal was significantlyinhibited. The maximum rate of inhibition reached more than 90%, The changes in the activity ofAChE significantly related with the concentrations of petroleum hydrocarbons. Thus, the changes inthe activity of AChE can reflect the toxic effects of petroleum hydrocarbons on Nereis diversicolor.The metallothionein (MT) concentration in Nereis diversicolor changed significantly with theincrease of the metal concentration and the prolongation of exposure time (p＜0.05) whereas thereno marked changed in the control. Exposed to Cu (100, 200, 500, 1,000 and 4,000μg·l-1), the MTconcentration in Nereis diversicolor reached its maximum value at 12h, when the concentration ofCu in solution was equal to or lower than 500μg·l-1; however, the concentration of MT in Nereisdiversicolor reached its maximum value at 48h when the concentration of Cu in solution was 1,000and 4,000μg·l-1. The MT concentration inducted by Cd (200, 500, 1000, 5,000 and 20,000μg·l-1),reached its maximum value at 12h. Meanwhile the inductive ration of Cu and Cd onmetallothionein concentration was Cd＞Cu. The concentration of MTs in Nereis diversicolorincreased with the conceptrations of Cu and Cd in solution increased. Thus, MTs in Nereisdiversicolor can be used as a biomarker to assess the impact of metallicpollution on the environment and monitoring of metal contaminationUnder the tested condition, the accumulation of Cd and Cd were increased with raised Cu and Cdconcentrations. The accumulation of petroleum hydrocarbons was increased with raised petroleumhydrocarbons, but the change was not significant.
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