【作者】 王静凤；

【导师】 张学成；

【作者基本信息】 中国海洋大学 ， 海洋生物， 2004， 博士

【摘要】 海洋双壳类动物对重金属具有很高的累积能力，且能够可靠地反应周围环境的重金属水平，作为指示生物已成为全球海洋重金属污染监测的重要手段。环境因素和机体生理过程的改变在支配重金属的生物有效性方面起了重要作用。本研究以翡翠贻贝Perna viridis为实验材料，采用放射性示踪技术，研究了不同环境条件下翡翠贻贝对重金属的累积及转运方式，并对相关作用机制进行了探讨。 首次将呼吸计和放射性示踪技术相结合，同时测定同一翡翠贻贝个体在不同条件下的耗氧率和溶解态重金属吸收率。结果表明，在进行陸缺氧的条件下，翡翠贻贝对溶解态Cd和Se的吸收随着周围水环境中氧受限程度的增加而减少。在给定不同程度缺氧和无氧条件下（0-10kPa），翡翠贻贝对溶解态Cd和Se的吸收率随着氧分压的降低而减少，且与耗氧率之间存在着显著的相关性。在无氧条件下，翡翠贻贝对溶解态Cd和Se的吸收率分别比正常氧分压低3.7倍和7.5倍。将翡翠贻贝在空气中暴露24h或36h后，再重新入水，出现明显的O₂债现象，其对溶解态Cd和Zn的吸收与O₂债偿还紧密相关。五氯酚（Pentachlorophenol，PCP）能够导致机体氧化磷酸化过程脱偶联，即机体耗氧率提高，但ATP的产生量降低。当翡翠贻贝预暴露PCP后，对Cd的吸收率明显减少。在实验给定的温度范围内，翡翠贻贝的耗氧率和对溶解态Cd和Zn的吸收均呈温度依赖性关系，随温度的升高而增加；与暴露于30℃的固定温度相比较，当15℃的驯化贻贝个体直接暴露于30℃的海水中，溶解态Zn的吸收率显著提高，而Cd的吸收率却减少。除了载体介导的易化转运过程外，翡翠贻贝对溶解态Cd和Zn的吸收也与机体的能量代谢相关联，涉及到需要ATP供能的主动转运过程。温度急剧变化，使翡翠贻贝对溶解态Cd和Zn的累积出现了不同的累积结果，其机理尚需进一步研究。 Se和Hg间的相互作用在海洋无脊椎动物中至今缺少研究。使用不同形态硒(Se⁴⁺，s产和有机se（seleno^Lmethio八泊e，SeMe）)，通过预暴露和同时暴露途径，研究不同形态硒对翡翠贻贝累积无机汞（H广）和甲基汞伽曲ylinere切ry)MeHg)的影响，进一步探讨Se、Hg在海洋无脊椎动物体内相互作用的关系。实验结果表明，在实验设定的浓度范围内（<500滩.L-l），同时暴露，s犷和s产均不能显著影响翡翠贻贝刘榕解态和颗粒态H广和Me]Hg的累积。seMe育游显著抑制翡翠贻贝对溶解态MeHg的吸收，提高对溶解态H犷+的吸收，但不能影响翡翠贻贝对颗粒态Hg的同化效率;通过投喂载反少或女N贻的硅藻，对翡翠贻贝进行预暴露，组织Se的浓度随预暴露时间延长而增加。低含量组织硒，显著抑制溶解态无机汞和甲基汞的累积，促进颗粒态甲基汞的同化效率。高含量组织硒，对溶解态无机汞和甲基汞、颗粒态甲基汞的累积均没有影响，但能抑布颤粒态无机汞的同化效率。强调了Se和Hg之间的作用在海产贝类中具有形态、浓度和暴露途径特异性。 本研究对.于进一步了解重金属污染对海洋生态系统和生物资源的影响，为新海水水质标准的科学制定，和海洋生物体重金属污染评价标准的制定，加强海洋环境管理措施等提供科学依据。更多还原

【Abstract】 Marine bivalves have been employed extensively as biomonitors of coastal contamination largely because of their high bioaccumulation capacity and faithful responses to ambient bioavailable metal levels. The changes of environmental factors and physiological processes of organism play an important role in controlling the bioavailability of metal to marine bivalves. The bioaccumulation and transport pathway of heavy metal in green mussels Perna viridis were studied under different environmental conditions employed radiotracer techniques. The relative mechanisms of metal transport were also discussed.For the first time we coupled respirometric and radiotracer techniques to simultaneously measure the rates of oxygen and metal uptake in the green mussel under different environmental conditions. Under the progressive hypoxic conditions, the Cd and Se uptake decreased with an increasing degree of oxygen limitation. When the mussels were tested at constant hypoxic and anoxic conditions (0-10kPa) , Cd and Se uptake also decreased with decreasing PO2 Under anoxic conditions, Cd and Se uptake was 3.7 and 7.5 times lower than that under normoxia. There was a significant correlation between the 62 consumption rate and uptake rate of Cd and Se, respectively. With re-immersion of the mussels after aerial exposure, there was an apparent Q2 debt, and metal uptake was closely coupled with the Q2 debt repayment. Similarly, the quantified uptake rates of Cd and Zn were directly correlated with the O2 consumption rate in this experiment Although the O2uptake in mussels was enhanced by exposure to pentachlorophenl, an uncoupler of oxidative phosphorylation, the Cd uptake was significantly decreased due to the depression of ATP production. Both 62 consumption rate and Cd and Zn uptake rates were temperature-dependent and increased with increasing temperature. When the temperature oscillated from 15 to 30 , Zn uptake was further stimulated whereas Cd uptake was reduced as compared to the uptake measured at 30 癈 without oscillation. These experimental results suggested that Cd and Zn uptake was correlated with the energy metabolism, and may even be involved in an active transport, besides the facilitated transport. The mechanism of contrasting Cd and Zn accumulation induced by temperature oscillated sharply need to be further considered.The interaction of selenium (Se) and mercury (Hg) in marine invertebrates has been less well studied. In this study, we examined the influences of different species of Se (selenite, selenate, seleno-L-methionine) on the accumulation of inorganic Hg2 and methylmercury (MeHg) by the green mussels via the pathway of pre-exposure and concurrently exposure. The interaction of Se and Hg in marine invertebrates was further discussed. At the experimental concentrations tested (<500 u.g I/1), selenite and selenate did not significantly affect the accumulation of either mercury species by the green mussels. In contrast, selenomethionine significantly inhibited the uptake of MeHg and enhanced the uptake of Hgy the mussels, but it did not affect the assimilation from the ingested diatoms. We further examined the influence of tissue body burden of Se in the green mussels following pre-exposure to selenite and selenomethionine on the accumulation of Hg2 and MeHg from the dietary and aqueous phases. The results showed that tissue Se concentrations increased with increasing Se pre-exposure period. The accumulation of both mercury species in aqueous phase were significantly inhibited, whereas the dietary assimilation of MeHg were significantly enhanced at low concentration tissue Se. The influences on the aqueous uptake and dietary assimilation of both mercury species werealso variable at high concentration tissue Se. The study thus strongly highlights the specificity of the Se and Hg interaction in marine mussels for element species, concentration and exposure pathway.The study r esults c an provide us well understanding o f influences of heavy m etal contaminants on marine ecosystem and biologic resources, and更多还原