应急引水工程对巢湖微生态系统结构及稳定性的影响机制

As the emergency measures of alleviating cyanobacteria bloom and improving water quality, the large water diversion projects have been widely used in the eutrophication lakes restorations. However what kind of impact will the amounts of external water have on the original lake ecological environments? Until now, in large, eutrophic, shallow lakes, little is known about the response and feedback mechanisms of the lake ecosystem to the anthropogenic disturbances. In this project, bacteria, sensitive to limnic changes, is selected to be the bioindicator of aquatic organisms, and the emergency engineering of water diversion from Yangtze River to Chaohu Lake will be focused on. To provide insight into the effects of water diversion on the bacterial community structure, stability and ecological effects of Chao Lake, the 16S rRNA gene based high-throughput sequencing, multivariate statistical analysis and artificial neural network model will be conducted for revealing the effect of water diversion on the spatio-temporal patterns of bacterial communities and their coupling relationships by the field observation and indoor simulation experiments. The special attention will be concentrated on the responses of the microecosystem of Chaohu Lake to different flow velocity of water diversion, different water exchange cycle and the input of exogenous microbes. The impact mechanism of water diversion on the structure and stability of the lake ecosystem will be displayed, which will provide a benefit guide for the ecological restoration on eutrophic shallow lakes in the area of middle and lower reaches of Yangze River.

作为减轻蓝藻水华和改善水质的应急措施——大型引水工程常被广泛应用于富营养化湖泊的治理，但大量外来客水的输入会对受水湖泊生态系统产生什么样的影响？尤其是湖泊生态系统对这种人为环境干预的响应和反馈机制是什么？目前研究甚少。本研究拟以“引江济巢”应急工程为背景，选取对湖泊环境变化敏感的微生物——细菌作为指示生物，通过野外调查与室内模拟实验，利用高通量测序、多元统计分析、人工神经网络模型等手段，研究引水作用下巢湖水体、沉积物中细菌群落时空格局的变化特征，分析水文、理化因子与细菌群落演替间的耦联关系，探讨引水对巢湖细菌群落结构及稳定性的影响及其生态效应。重点通过研究巢湖微生态系统对不同引水流速、不同换水周期和外源微生物输入的响应，阐明引水对富营养化湖泊微生态系统结构及稳定性的影响机制，为我国长江中下游浅水富营养化湖泊的生态修复实践提供理论指导。

本研究以“引江济巢”应急工程为背景，通过野外定位监测探明引水作用下巢湖水体、沉积物中细菌群落时空格局的变化特征；利用高通量测序、多元统计分析和共生网络模型等手段分析引水对巢湖细菌群落共生关系及稳定性的影响及其生态效应。研究结果显示：（1）巢湖细菌的β多样性和群落结构存在显著的季节变化和不显著的空间变化；不同年份水体、沉积物样本中有10个门具有极显著差异（P <0.001），但相对丰度变化之间似乎没有规律性。两年间相同季节相比，一些优势细菌丰度显著减少，甚至消失。季节和年际的动态特征表明巢湖细菌演变和更替较快；（2）在不同污染类型的流入河流中观察到特定的优势属，表明环境诱导的物种选择对水体、沉积物细菌群落的组成有很大影响。此外，“引江济巢”兆河入湖口水体、沉积物样品中检测出的厚壁菌门只在春季样品中具有很高的丰度，而其它区域厚壁菌门的丰富度却普遍很高，这表明外源性污染和环境诱导强烈影响着巢湖沉积物中细菌群落的分布；（3）网络分析表明巢湖水体和沉积物中细菌群落具有复杂的共生模式和模块化结构，根据网络中心性，在两年水体、沉积物中各筛选出六个关键物种，它们在维持生态群落的结构和功能方面发挥关键作用；（4）模拟实验表明低流速为微生态系统带来了一定量的溶解氧和营养物质，使低流速处理组的物种多样性有明显提高，但随着流速的增大，物种多样性则又回落至原有水平甚至更低；而外源微生物的输入不仅增加了原有环境中的物种多样性还在一定程度上改变了原有的细菌群落结构分布。本研究结果有助于揭示引水对富营养化湖泊微生态系统结构及稳定性的影响机制，对维持巢湖湖泊生态系统健康具有重要价值和现实意义。