珠江口牡蛎生物标志物对近海主要污染物的响应机制

The Pearl River Delta is one of the fastest growing and most urbanized regions in China, as well as a major global manufacturing base. The large population and rapid economic growth in the Pearl River watershed have greatly increased the discharges of various pollutants into the Pearl River Estuary (PRE), causing significant environmental deterioration over the last few decades. Nevertheless, the key pollutants have barely been evaluated systematically despite the tremendous efforts to quantify the concentrations of different environmental contaminants in the PRE over the past decades. Until now, whether these contaminants have caused any significant impacts on local marine organisms in PRE is mostly speculative. In this project, we propose to take advantages of a widespread euryhaline bivalve species, namely, the Hong Kong oysters Crassostrea hongkongensis, and quantify the biomarker responses at different physiological, biochemical and cellular levels (including antioxidant defense, physiological metabolism, detoxification, and cytological responses) in the oysters collected from different locations of the PRE. Coupled with simultaneous measurements of major chemicals of concerns (especially toxic metals and organic pollutants such as PAHs and pesticides) in the oysters, the biomarker measurements will reveal the specific chemicals of concern in the estuary that are potentially responsible for the observed biological impacts. Given the complex environments in the PRE, laboratory studies will further be supplemented to provide a more reliable interpretation of the biological responses to specific contaminants of concern and the interactions among ecosystem stressors and metal mixtures. It is expected that the proposed research will have a major impact both locally and internationally, as well as academically and socially.

近三十年间，珠江三角洲是我国经济发展和城镇化进程最快的地区之一，陆源污染物排放巨大，经长年累月，已成为华南地区污染物赋存最为富集的地区。大量过去的研究对珠江口不同污染物浓度进行了测定，但对污染物是否引起近海生物毒害作用这一关键的科学问题一直未有明确的解答。本项目拟采用近海常驻生物-香港牡蛎(Crassostrea hongkongensis)为预警监测种，在珠江口复杂环境下筛选出重金属、有机物、农药等主要污染物种类，分析牡蛎对这些污染物的生物累积量及在遗传-生化-生理-细胞等不同水平生物响应过程，通过野外毒效数据和实验室校正研究，排除季节、盐度等环境因子影响，量化珠江口近海主要污染物对牡蛎造成的胁迫作用机理，鉴定出导致生物效应的关键污染物，为合理评估珠江口污染物生态效应，揭示污染物生态毒理机制，海陆管理提供理论基础和数据支撑，在近海生态与居民食用安全领域具有重要的科学意义与经济价值。

本项研究选用双壳贝类生物为主要研究对象，特别针对珠江口近海潮中带-潮下带常驻物种香港牡蛎(Crassostrea hongkongensis)为监测种，系统研究了牡蛎生物标志物在种群水平、亚细胞水平、个体生化代谢、蛋白组、转录组及分子水平揭示珠江口金属Cu、Zn、Ni、Cr、Ag等主要污染物的生物响应机制，通过对比和筛选出特异性生物标志物，量化生物标志物-生物响应耦合鉴定；结果证实有 8 种蛋白质发生改变，银可能对粒体（OAT）和内质网（ERP29）中产生影响。在高Cd有25种独特的蛋白质，其中7种与遗传物质（DNA和RNA）有关，包括DNA 复制和转录受损，MCM亚单位和RPB2差异；这些差异表达暗示了镉的潜在遗传毒性，是镉污染的潜在标志物。剩下的37种蛋白质仅在高锌-铜-镍-铬牡蛎中观察到，可用于指示铜、锌、铬和镍的相对水平，如TEKT3和CEP135。过度积累的金属，尤其是铜和锌，会导致结构蛋白（即细胞骨架和染色体）的破坏。尽管如此，增强的tRNA生物合成和外显体相关的蛋白质丰度活性可能有助于解析高金武污染压力下牡蛎的响应机制和毒性机理。本研究提供了金属胁迫下牡蛎的分子变化，并进一步提出了一些可用于生态评估的潜在生物标志物。