水体沉积物结合态镉对大型溞（Daphnia magna）的生物毒性研究

选择大型溞(Daphnia magna)作为受试生物,以大型溞体内金属积累量、金属硫蛋白含量和死亡率作为测试指标,考察了上覆水体系与水柱-沉积物共存体系中金属镉(Cd)的毒性状况,探讨了水体沉积物中重金属的生物毒性作用机制.结果表明:暴露于水柱-沉积物共存体系和上覆水体系中的大型溞体内的生物积累量均随沉积物Cd含量的升高而升高,且前者显著高于后者,说明沉积物中的Cd可通过食物吸收等途径对生物体致毒、致害;暴露于两种体系中的大型溞体内的MT含量在低浓度条件下随沉积物中Cd含量的升高而升高,当Cd含量高于800μg·g-1时MT含量大幅度下降,并且两体系之间无显著差别;暴露于两种体系中的大型溞幼溞死亡率无显著差别.上覆水中溶解态Cd和沉积物中可交换态Cd是对水生生物重要的毒性影响形态.

The Biotoxicity of Cadmium Associated with Fresh-Water Sediment to the Daphnia magna

In order to reflect the toxicity of cadmium(Cd)in the two different systems: overlying water system and watersediment coexistence system, the toxicological parameters such as metal body burden, MT and mortality in a freshwater cladoceran Daphnia magna after exposure were quantified. Results showed that, exposed to the two different systems, Cd accumulation in Daphnia magna both increased with the ambient increasing Cd concentrations in sediment, and in the water-sediment coexistence system the Cd bioaccumulation was significantly higher than that in the overlying water system, which illustrated that Cd in sediment could induce toxicity to Daphnia magna from ingested food. In the two different systems, when the Cd concentration in sediment was low the MT induction increased with the increasing Cd concentrations and when the Cd concentration was higher than 800μg·g -1 the MT induction significantly decreased, and there was no significant difference between the two systems. Exposed to the two systems, the mortality of juvenile Daphnia magna also had no significant difference. Overall, the dissolved Cd in overlying water and exchangeable Cd in sediment were two most important species impacted on aquatic toxicity.