盐度对重金属镉的毒性影响:以太平洋牡蛎为例

Influence of Salinity on Toxicological Effects of Cadmium:A Case Study on Oyster Crassostrea gigas

渤海近岸、河口海域镉(cadmium,Cd)污染严重,且盐度低于正常海水盐度,因此,有必要研究低盐对Cd毒性效应的影响。本研究以太平洋牡蛎(Crassostrea gigas)为研究对象,在正常盐度(31.4 psu)和低盐度(15.7 psu)条件下驯化后,在不同浓度的Cd(5、20、80和240μg·L^(-1))海水环境中暴露7 d,通过检测牡蛎鳃中Cd和必需金属元素含量以及生物标志物,探究低盐对Cd毒性效应的影响。结果显示,Cd破坏了牡蛎鳃中钠(Na)和镁(Mg)离子平衡,而Cd和低盐复合胁迫对钾(K)含量变化存在显著交互作用。Cd和低盐均诱导牡蛎鳃氧化应激和能量代谢紊乱,低盐还影响了Cd的毒性效应,表现为Cd和低盐复合胁迫对丙二醛(malondialdehyde,MDA)含量和异柠檬酸脱氢酶(isocitrate dehydrogenase,IDH)活性的影响存在显著交互作用。综合生物标志物响应(integrated biomarker response,IBR)分析结果显示,Cd对牡蛎产生的压力随Cd暴露浓度升高不断加大;Cd和低盐复合胁迫对牡蛎产生的压力高于Cd单一胁迫,表明低盐加剧了Cd对牡蛎的毒性效应。因此,为了更全面地评估近岸海域痕量金属的环境风险,应充分考虑低盐这一环境因素对污染物毒性的影响。

Cadmium(Cd)contamination is a severe problem in the Bohai Sea(China),especially in the estuarine and coastal environments with low salinity.In this study,adult oysters Crassostrea gigas were exposed to 4 doses of Cd(5,20,80 and 240μg·L^(-1))at either normal(31.4 psu)or low(15.7 psu)salinity for 7 days.The potential impact of low salinity on the toxicological effects of Cd was investigated by measuring the variations of Cd and essential elements and biomarkers.After exposure to Cd,Na and Mg contents in the gills were significantly increased,and a significant interaction between Cd and low salinity on the change of K contents was identified.The increases in enzymes related to oxidative stress and energy metabolism were observed after exposure to the combined Cd and low salinity.What is more,the Cd-induced toxicological effects were affected by low salinity,manifested by the significant interactive effects on the malondialdehyde(MDA)contents and isocitrate dehydrogenase(IDH)activi-ties.Further integrated biomarker response(IBR)analysis showed that the adverse effect of Cd on oysters was ex-acerbated with the increase of exposure concentration.The combined effect of Cd and low salinity was much grea-ter than that of single Cd exposure,indicating that low salinity aggravated the toxicological effects of Cd on oys-ters.Therefore,the impact of low salinity on the toxicity of environmental contaminants should be fully considered to comprehensively evaluate their environmental risks in the coastal zones.