封闭性海湾海水养殖区微型鞭毛虫的多样性和群落结构研究

The enclosed bays, with good shelter conditions and wave dissipation capacity, are often the preferred sites for mariculture, but their ecosystems are also vulnerable due to natural conditions and frequent anthropogenic disturbances. As the microproducers and the main grazers of pico-sized plankton such as bacteria and cyanobacteria, nano-sized (2-20μm) flagellates are one of the key links to nutrient regeneration, mass transfer and energy flow in mariculture ecosystems. Different types of culture such as shellfish, algae or fish culture have different impacts on the community structures of nanoflagellates, which, however, may cause the reactions to the mariculture systems themselves. In this project, with the use of high-throughput sequencing technology, real-time quantitative PCR technology (qPCR) and fluorescence in situ hybridization (FISH) technology, and combined with conventional investigating approaches for nano-flagellates and their habitats, we attempt to explore the diversity, community structure and temporal and spatial distribution of nanoflagellates in different types of mariculture areas in Sansha Bay, a typical enclosed bay in Fujian Provence. We also attempt to find out the leading factor(s) that cause the differences in different habitats, and finally reveal the effects of mariculture on the community structure and diversity of nanoflagellates in the enclosed bay ecosystem. The findings will enrich our understanding of the importance of nanoflagellates in the mariculture system and help us to understand more comprehensively about the functions and regulatory mechanisms of the mariculture ecosystem, to predict the changes and to improve mariculture planning and management in natural sea area of enclosed bays.

封闭性海湾具有良好的避风条件和消浪能力，往往是海水养殖的首选地，但其生态系统也由于受到自然条件制约和剧烈人类活动干扰而十分脆弱。微型鞭毛虫作为微型生产者或细菌、聚球藻等微微型浮游生物的主要捕食者，是海湾养殖生态系统中物质循环、能量流动和营养盐再生的关键环节之一，其群落结构受到不同类型养殖生物和养殖模式的影响，并将反作用于养殖生态系统本身。本项目选择在福建省三沙湾这一典型封闭性海湾，应用高通量测序、荧光定量PCR、FISH等分子生物学技术，结合传统的鞭毛虫及生境调查研究方法，探究不同类型养殖区和非养殖区中微型鞭毛虫的多样性、群落结构及其时空分布特征，查明产生差异的主导因素，揭示水产养殖对微型鞭毛虫群落及其多样性的影响。研究结果将提高我们对微型鞭毛虫在海湾养殖生态系统中重要作用的认识，并有助于更好地认知内湾性养殖生态系统的功能与调控机制，预测其变化，从而服务于自然海区养殖规划与管理水平的提高。

海洋微型鞭毛虫种类多样，分布广泛，在海洋微食物网中扮演着生产者、消费者、分解者等多种生态角色。三沙湾是典型的封闭性海湾，受水产养殖等人类活动影响较大，为比较不同时空条件下微型鞭毛虫群落对自然与人为环境变化的响应提供了条件。在本研究中，我们利用高通量测序技术结合传统显微镜观测技术，调查和比较了不同季节中三沙湾微型鞭毛虫群落在大型海藻养殖区、网箱养殖区、混合养殖区、湾内及湾外非养殖区的丰度、多样性、群落结构和生物地理分布格局，并探讨了影响其群落构建的生态学机制。主要结果如下：（1）三沙湾的环境因子表现出显著的季节性变化，并且在养殖区与非养殖区之间差异明显；（2）受季节变动以及不同养殖环境的影响，三沙湾微型鞭毛虫的丰度、多样性和群落结构具有一定的时空分布特征，鞭毛虫各类群的物种相对丰富度和相对丰度有所差异，对环境条件的响应不同，代表了这些类群在海区中的生态位分化；（3）在总体样本中，环境因素主导的确定性过程对微型鞭毛虫群落构建起决定性作用；而空间因素主导的随机性过程在单季节样本的群落构建中更重要；（4）物种间的相互作用是影响微型鞭毛虫群落构建的重要生态过程，物种共现性网络表现出小世界和模块化特性，在春季和秋季具有更加复杂的网络结构，丝足虫、MALV-II、甲藻、硅藻等优势类群构成主要网络节点，其间明显的合作共生关系对维系三沙湾生态系统结构与功能至关重要。综上，本研究提供了对三沙湾养殖生态系统微型鞭毛虫多样性与群落结构的时空动态、群落构建与共现性模式的见解，加深了我们对海水养殖活动如何影响微型鞭毛虫群落的理解。研究结果对揭示人为干扰下微型真核生物的多样性和生物地理格局、了解海洋生态系统结构与功能有一定意义，同时为更合理地规划三沙湾养殖活动、促进海水养殖健康发展提供有益参考。