浅水湖泊水体-沉积物中细菌种群交换的过程及机制

Bacterial community is an important component part of the microbial food web, and plays a key role in the transformation of complex organic matter and in the biogeochemical cycling of the primary elements in lake ecosystems. Frequent wind-induced wave disturbance is a common characteristic of many large shallow lakes that differs from deep lakes and oceans, and have a great influence on the ecological environments of shallow lakes. Until now, little is known about the effect of this disturbance on bacterial community structure, and the community stability after disturbance in large shallow lakes. In this study, the modern molecular biology technology were conducted to determine changes of abundance of activity bacteria, increase or decrease of bacterial quantity, succession of diversity and bacterial community structure of the water and sediment through field investigation and indoor simulation experiments, and sought to answer following two scientific questions: 1) The contribution of sediment bacteria to the structure change of water column bacterial community in a mixing large shallow lake. 2) The stability of bacterial community following frequent hydrodynamic disturbance. This result will help to better understand the hydrodynamic process influence transport and transform way, and efficiency of internal nutrient loading in large shallow lakes, and further provide a basis data for revealing the microbial circulation mechanism of lake nutrients and outbreak mechanism of cyanobacterial blooms.

细菌是湖泊生态系统中最重要的组成部分，在营养盐的生物地球化学过程中起着十分重要的作用。频繁的水动力扰动是大型浅水湖泊区别于深水湖泊和海洋的一个最显著的环境特征，对浅水湖泊的生态环境会产生很大的影响。然而目前，关于水动力扰动下大型浅水湖泊水体-沉积物中细菌种群交换的过程及机制的研究还远远不够。本研究拟以大型浅水湖泊—太湖为例，通过野外调查与室内模拟实验，运用现代分子生物学手段，研究水动力扰动下水体和沉积物中活性细菌丰度的变化、细菌数量的增减、多样性和群落结构的演替，并力图回答以下科学问题：1）在水动力扰动频繁的大型浅水湖泊，沉积物中细菌对水柱中细菌群落结构变化的贡献大小？2）在频繁的水动力扰动下，细菌群落具有怎样的稳定性？研究结果将有助于深刻认识水动力扰动影响浅水湖泊内源营养盐负荷的迁移转化的方式、途径及效率，为进一步揭示浅水湖泊营养盐的微生物循环机理、蓝藻水华暴发机制提供供基础理论资料。

频繁的水动力扰动是大型浅水湖泊区别于深水湖泊和海洋的一个最显著的环境特征，对浅水湖泊的生态环境会产生很大的影响。然而目前，关于水动力扰动下大型浅水湖泊水体-沉积物中细菌种群交换的过程及机制的研究还远远不够。本项目拟以大型浅水湖泊—太湖为例，通过野外调查与室内模拟实验，运用现代分子生物学手段，阐明了太湖梅梁湾水体中总细菌、活性细菌丰度的月变化及其主导环境因子，探讨了强烈水动力作用（台风过程）对太湖沉积物细菌群落结构的影响方式，探讨了细菌群落对水动力频繁扰动的响应方式，并对细菌群落的稳定性进行了阐释。研究结果表明，太湖梅梁湾水体中总细菌、活性细菌丰度具有显著的时间差异，总细菌、活性细菌丰度不同月份差异较大，夏季月份普遍较高；强烈水动力扰动，如台风过程，对沉积物细菌群落结构有一定的影响，在台风中期沉积物样品中有两种细菌：拟杆菌门（Bacteroidetes）和硝化螺旋菌门（Nitrospirae，亚硝酸盐氧化细菌）会突然大量地出现或激增，但这种影响是快速而短暂的；室内模拟3-5 m/s 和 >8 m/s 风速引起的水动力扰动对附着和浮游细菌群落结构具有明显的影响，细菌群落多样性会随着扰动加强而显著增加，而且后者引起的增加量显著地高于前者。两种扰动停止4天后，附着细菌群落结构并没有恢复，都和扰动前有一定程度的差异。这可能是细菌群落对恢复的响应需要更长的时间，但更可能的是扰动使细菌群落结构发生了本质的变化，已无法恢复。本研究结果将有助于深刻认识水动力扰动影响浅水湖泊内源营养盐负荷的迁移转化的方式、途径及效率，为进一步揭示浅水湖泊营养盐的微生物循环机理、蓝藻水华暴发机制提供供基础理论资料。