海洋硅藻胞外聚合物在HOCs的生物富集和毒性中的作用研究

Hydrophobic organic contaminants (HOCs) could combine with natural organic matter which ultimately affected their environmental behavior and toxicity. In the marine ecosystem, extracellular polymeric substances (EPS), a protective net-like structure outside the cell, are secreted by planktonic diatom to be an important source of natural organic matter, and its role cannot ignore when considering the distribution, fate and bio-toxicity of HOCs. However, in regard to diatom EPS, recent studies remain to focus on the structure observation and content detection, and the effect of diatom EPS on environmental behavior and ecological risk of HOCs is unknown. Hence, based on our former studies, we choose non-ionic and ionic HOCs as tested pollutants, and this project intends 1) to disclose the role of EPS on the bio-availability and toxicity of HOCs on the rotifer by analyzing the correlation between EPS concentrations and the HOCs-enrichment capability in rotifer as well as the reproductive damage degree; 2) to discover the effect mechanism of diatom EPS on the bio-availability and toxicity of HOCs from the view of the binding process with HOCs. We could expand the understanding about the role of EPS secreted by diatom involved in interactions between plankton and HOCs. Our goal is to provide some theoretical basis and guiding principle to the ecological risk assessments of HOCs.

疏水性有机污染物（HOCs）能够与水体中的天然有机质结合而改变自身环境行为和生物毒性。海洋生态系统中，浮游硅藻分泌的胞外聚合物（extracellular polymeric substances，EPS）是天然有机质的重要来源。因此，探讨HOCs在海洋环境中的归趋和毒性时，考虑浮游硅藻EPS的影响尤为重要。目前硅藻EPS研究停留在形态观察和含量检测层面，有关其与HOCs生态效应的关系知之甚少。基于前期研究，本项目以常见海洋浮游硅藻EPS和典型HOCs为代表，在实验生态条件下：1）以轮虫为受试生物，解析轮虫HOCs富集能力和生殖损伤程度与EPS含量关联性，阐明硅藻EPS影响HOCs生态效应的一般规律；2）基于EPS与HOCs的结合原理，探讨硅藻EPS干扰HOCs生态效应的作用机制。本项目旨在揭示浮游硅藻EPS在HOCs迁移转化及毒性中的作用，为HOCs污染的环境风险评价和防控工作提供参考。

疏水性有机污染物（HOCs）的形态和生物有效性是当前环境领域研究的重点和热点之一。作为重要的影响因素，水体中的溶解性有机质通过络合、共吸附、共代谢等生物化学途径影响水体中有机污染物的形态、迁移及降解等环境行为。在海洋中，藻类尤其是硅藻代谢所释放的大量胞外产物（EPS），是海水溶解性有机质的重要组成部分。但目前硅藻胞外产物与海洋环境中疏水性有机污染物的相互作用研究有限。本研究以常见硅藻和典型HOCs-四溴联苯醚（BDE-47）为代表，研究了二者之间的交互作用特征和微观机制，揭示了硅藻胞外产物对四溴联苯醚生物有效性的影响规律。获得了一系列研究结果：1）进入稳定期后，硅藻细胞分泌EPS中多糖所占含量约为4.42%-6.94%，蛋白质约为16.2%-17.44%；基于三维荧光光谱发现，蛋白质的内源荧光来自色氨酸和酪氨酸/色氨酸蛋白物质；EPS含量受到CO2等环境因子调控；2）硅藻EPS能够抑制HOCs-BDE-47在轮虫体内富集，缓解HOCs引起轮虫的形态损伤、生殖毒性和氧化损伤；3）EPS能够与BDE-47形成非荧光性的EPS-BDE-47络合物，引起静态淬灭；EPS中的含氧基团（多糖里的-OH、C-O-C，蛋白里的C=O）等官能团参与络合作用；这是海水中BDE-47浓度降低的直接原因，此外，EPS也可作为架桥促进BDE-47在轮虫表面的吸附；4）吸附动力学实验表明，硅藻EPS促进了硅藻细胞对BDE-47的生物吸附，这一过程受静电引力和疏水作用驱动。本项目明确由硅藻分泌的胞外聚合物能够影响疏水性有机污染物的环境行为和生态风险，为理解海洋多溴联苯醚类污染物的归趋提供理论基础，对保障海洋生态的可持续发展和人类的健康具有重要意义。