变化径流下输水型河流沉积物微生物群落特征及其对氮转化的作用机制

Surface runoff changes caused by the operation of inter-basin water diversion projects will have an inevitable effect on the environment and microbial ecosystem of water-conveying rivers. To protect river ecological systems and guarantee the water quality, it is crucial to have a systematic analysis of the effects of water diversion projects on microorganism characteristics and their impacts on nitrogen transformation in sediments of water-conveying rivers under the condition of changing surface runoff. However, the microorganism characteristics of sediments in water-conveying rivers and their impacts on nitrogen transformation are still unclear so far. In this project, microorganisms in sediments of typical water-conveying rivers along the east route of the South-to-North Water Transfer Project are taken as the research objects. The spatial and temporal distribution and construction mechanism of microbial communities in sediments of water-conveying rivers under different runoff modes in dry, normal river flow and flood periods will be analyzed by field observation, indoor simulation and mechanism analysis. The response mechanisms of microbial community structure and function to environmental factors in sediments under bidirectional pulsating flow conditions in water-conveying rivers will also be clarified. At the same time, our study will also reveal the dynamic interaction among nitrogen-transforming microorganism, relevant enzyme activity, key functional genes and nitrogen-microbial transformation rates, and finally make a clarification on the mechanism of nitrogen-transforming microorganism in nitrogen transformation process in sediments of water-conveying rivers. Our study will provide scientific support for the comprehensive assessment of ecological impact of water transfer projects and the water quality guarantee of water transfer.

跨流域调水工程的运行调度产生的地表径流变化会对沿线输水型河流环境与微生物生态系统产生不可避免的影响。系统解析变化径流驱动下输水型河流沉积物中微生物特性和生源氮素的微生物转化过程对于河流生态保护和输水水质保障具有重要现实意义，而目前输水型河流沉积物微生物群落特征及其对氮转化的作用机制仍不清楚。本课题拟以南水北调东线典型输水型河流沉积物中微生物为研究对象，通过野外观测、室内模拟和机理分析等方法，解析输水型河流在枯水期、丰水期和平水期的不同径流模式下沉积物微生物群落时空分布规律与物种构建特征，阐明变化径流下河流沉积物微生物群落的环境响应机制，探讨输水型河流特殊双向脉动水流条件下氮转化菌群、胞外酶活、关键基因变化与不同形态氮素转化速率之间的动态交互关系，阐明输水型河流沉积物中生源氮素的微生物转化机制，为全面评估调水工程生态影响和保障调水水质安全提供科学依据。

跨流域调水工程的运行调度产生的地表径流变化会对沿线输水型河流环境与微生物生态系统产生不可避免的影响。系统解析变化径流下输水型河流沉积物微生物群落结构、多样性、环境驱动机制、功能基因、物种构建机制对于河流生态保护和输水水质保障具有重要现实意义。本课题通过在南水北调东线输水河流区域对水体与沉积物进行分水情、多点位和多频次的取样与分析，掌握了调水工程影响下输水河流环境特征及微生物群落结构与多样性分布规律，解析了输水河流沉积物微生物群落分布与变化环境相关性及其功能特性，探究了输水河流微生物群落地理空间结构差异的生态学机制，阐明了洪水径流影响下输水河段人工运河沉积物真核微生物群落时空分布规律及群落构建机制。研究发现，南水北调东线源头输水河流沉积物样品中优势菌门依次为变形菌（Proteobacteria）、厚壁菌（Firmicutes）、放线菌（Actinobacteria）、拟杆菌（Bacteroidetes）和蓝藻（Cyanobacteria）。微生物群落分布主要受氨氮、总氮、电导率、总磷等环境因子的影响，其中氨氮浓度是驱动输水河流微生物群落分布变化最主要的环境因素。氨氧化菌、脱卤菌、硫酸盐还原菌、亚硝酸盐还原菌、硫化物氧化菌等是沉积物样品中的主要功能菌群。其中，氨氧化菌、亚硝酸盐还原菌和固氮菌均都是生物氮循环的重要驱动力，表明输水河流中的氮转化过程可能较为活跃。微生物物种组合的嵌套性和空间转换共同导致了南水北调东线输水河流微生物群落的空间结构变迁，且物种组合的空间转换则是其最主要的生态学机制。此外，洪水径流会影响输水河段的真核微生物群落特性，洪水后河流沉积物样品的微生物丰富度与多样性高于洪水前河流沉积物样品的微生物丰富度与多样性。洪水后的输水河流具有潜在的健康与环境风险，Lepocinclis, Synurale, Hibberdiales等对人类健康及河流生态具有健康风险的“危险菌群”在洪水后被检出。本研究为评估调水工程生态影响和保障调水水质安全提供了科学依据。