东海贝类养殖区贻贝累积脂溶性毒素的机制及其溯源研究

In recent years, phycotoxins contamination seriously threatens marine ecosystems and seafood safety because toxic algae blooms occur frequently in Chinese coastal areas. Historically, a number of lipophilic toxins such as OA, PTX, YTX, etc. have been detected in different aquaculture shellfish samples. Serious Diarrhetic Shellfish Poisoning (DSP) incidents occurred in Ningbo City, Zhejiang Province, and Ningde City, Fujian Province, in May, 2011. High content of DSP toxins, including OA, DTX1, and their esters, accompanied with PTX2, PTX2sa, and 7-epi-PTX2sa toxins, were detected in the mussels associated with the incidents. The current project proposal is submitted under this background. The following laboratory experiments will be carried out and analyzed: (a) feeding different shellfish with toxic Prorocentrum lima, (b) isolation culture and toxins of Dinophysis spp., and (c) characteristics of DSP toxins adsorption by resins. Periodical monitoring for shellfish, Dinophysis algae, and seawater samples in aquaculture areas of the East China Sea will be combined with the laboratory experiments. Data will be acquired in the research program will include: (a) the dynamic process of DSP toxins accumulation, transformation, and elimination in shellfish such as mussels, scallops, and oyster, etc.; (b) toxin producing ability of Dinophysis algae; and (c) influence of salt matrix in seawater on the DSP toxins adsorption by resins. The objectives of the proposal are to explain the accumulative mechanisms of DSP toxins in mussels and to determine the algal source of lipophilic toxins in the aquaculture areas of the East China Sea. Whilst the technical system for monitoring and forcasting lipophilic toxins will be developed in the study. The prospective achievements will supply original data and technical support for the monitoring work on toxic algae blooms and toxins in shellfish in Chinese coast, which are of great significance to protect public health and the marine environment, and to ensure sustainable development of aquaculture economy.

近年我国沿海有毒赤潮频繁暴发，藻毒素污染严重威胁海洋生态系统和贝类食用安全。诸多经济贝类中频繁检出腹泻性贝毒（DSP）及PTX、YTX等脂溶性毒素。2011年5月，浙江宁波和福建宁德等地暴发大规模DSP中毒事件，在肇事贻贝中检出高浓度OA、DTX1及其酯化物，及部分PTX组毒素。课题以此次中毒事件为背景，采用贝类摄食利玛原甲藻的食物链模拟、鳍藻的分离培养、树脂吸附毒素的过程模拟等实验手段，结合贝类、鳍藻和水体样品的定期野外监测；针对贻贝、扇贝、牡蛎等贝类累积、转化与排出DSP的动力学过程，有毒鳍藻的产毒组分与水平，及海水盐基质影响树脂吸附DSP的规律等内容开展研究。以期揭示贻贝累积高浓度DSP毒素的机制，确定东海贝类养殖区脂溶性毒素的来源，并建立相应的监测与预警技术体系。研究成果将为我国有毒赤潮和水产品贝毒的监测提供基础数据和技术支撑，对保护海洋环境和保障贝类养殖业的持续发展具有重要意义。

该项目以2011年5月份浙江宁波和福建宁德等地暴发的大规模腹泻性贝毒中毒事件为背景，选择浙江舟山近海枸杞岛贝类养殖区和福建福鼎晴川湾贝类养殖区为调查海区，采集单细胞鳍藻和贝类样品，分析其毒素组成特征和年际变化规律。研究结果表明，枸杞岛和晴川湾贝类养殖区分布的具尾鳍藻均只产生PTX2毒素，枸杞岛海区分布的未定种鳍藻样品只产生OA和DTX1毒素，而晴川湾分布的未定种鳍藻产生PTX2、OA、DTX1三种毒素，且仍以PTX2为主。晴川湾分布的具尾鳍藻单细胞毒素含量明显高于枸杞岛海区分布的具尾鳍藻。采集自枸杞岛贝类养殖区的31个批次的紫贻贝、厚壳贻贝样品和26个批次的牡蛎样品中检出多种脂溶性贝毒。GYM毒素在厚壳贻贝中检出率最高（90.3%），其次是牡蛎（57.7%）和紫贻贝（32.3%）样品，毒素含量均低于1 μg/kg。PTX2毒素在牡蛎中的检出率最高（26.9%），其次是紫贻贝（22.6%）和厚壳贻贝（19.4%）。OA、DTX1毒素在紫贻贝和厚壳贻贝中的检出频次均为16.1%，且伴随PTX2毒素检出，而牡蛎中只有一个批次的样品检出痕量的DTX1毒素。由此看来，紫贻贝和厚壳贻贝累积PTX2、OA、DTX1毒素的规律相似，但紫贻贝累积GYM毒素的频次明显降低。牡蛎样品中检出的PTX2阳性样品数量与紫贻贝、厚壳贻贝相似，但其几乎不累积OA、DTX1毒素。综合考虑鳍藻和贝类的毒素组成，我国东海贝类养殖区贝类沾染的PTX2、OA、DTX1毒素主要来源自具尾鳍藻和未定种的有毒鳍藻，同时浙江舟山近海面临GYM毒素的污染。尽管这些毒素在贝类中的含量均远低于欧盟推行的控制标准，但这些脂溶性毒素的生态风险仍应引起高度重视。建议加强我国东海贝类养殖区有毒鳍藻和GYM毒素产毒藻的生理、生态学研究，建立有效的监控预防体系，以保障海洋生态系统健康和海产品食用安全。