浅水湖泊沉积物脱氮的微生物作用机制

The accumulations of endogenous nitrogen in the lakes lead to the frequently occurring of eutrophication, while the input of exogenous nutrient is cut off. In-depth study of molecular ecology of nitrogen removal process in sediment in shallow lakes, with the aid of molecular biology techniques to identify the critically functional microbe in sediment, which plays an important role for removing nitrogen for controlling eutrophication in the Lake. This project will be proposed by in situ observation and simulation test, analyzing the process of nitrogen releasing and the law of removal in sediment, parsing the denitrification process involved in anaerobic ammonia oxidation and the dynamics function of microorganisms in the process of denitrification, using Real-time PCR technology for real-time quantitative research in nitrogen removal of key genes in sediments in shallow lakes, with the technology of 15N isotope tracer and membrane inlet mass spectrometry (MIMS) accurate determination of dissolved nitrogen and its isotopic abundance changes, figuring out the effect of different functional genes on sediment nitrogen removal, identifying the influence of the key ecological factors of anaerobic ammonia oxidation and denitrifying bacteria, establishing quantitatively responded relationship between the key factor and nitrogen removal of main functional genes, revealing the anaerobic ammonia oxidation and the denitrification molecular mechanism of action of ecological processes for nitrogen removal in molecular level in the sediments in lake ecosystems, providing theoretical basis for reducing endogenous nitrogen in shallow eutrophication lakes.

湖泊内源氮素的大量累积，导致外源营养物质的输入被切断后，水体富营养化现象依然频繁发生。深入研究浅水湖泊沉积物中氮去除的分子生态过程，借助分子生物学技术识别影响沉积物中氮去除的关键功能菌群，对湖泊富营养化控制有重要作用。本项目拟通过野外原位观测及模拟实验，分析沉积物氮素释放过程及去除规律，解析脱氮过程中涉及的厌氧氨氧化和反硝化过程中功能微生物的动态，运用Real-timePCR技术对浅水湖泊沉积物中氮去除关键基因进行实时定量研究，结合15N同位素示踪技术和膜接口质谱仪(MIMS)准确测定溶解态氮气及其同位素丰度的变化，研究不同功能基因对沉积物氮素去除的作用和效应，识别影响厌氧氨氧化和反硝化菌的关键生态因子，建立关键因子与氮去除主要功能基因的定量响应关系，从分子水平上揭示浅水湖泊沉积物中厌氧氨氧化和反硝化分子生态过程对氮素去除的作用机制，为浅水富营养化湖泊内源氮素的消减提供理论依据。

对表层沉积物及上覆水中不同形态氮和总氮及相关环境因子与细菌丰度存在显著的空间差异，细菌丰度与温度、溶解性有机碳（DOC）和Chl-a正相关，与透明度（SD）呈负相关；GAM的拟合曲线表明营养盐（TN、TP）对细菌丰度的变化也有很大的贡献；捕捉了特别环境过程（湖泛）水体TN、TP及其他理化因子溶解氧（DO）、透明度(SD)、pH值的变化过程；运用高通量测序技术，分析比较不同区域的细菌群落结构的差异结果表明变形菌门的α-、β- 和γ-纲(alpha-, beta-, and gamma-Proteobacteria)、拟杆菌门(Bacteriodetes)、放线菌门(Actinobacteria)、厚壁菌门（Firmicutes）等几种太湖主要的淡水菌群的比例都发生了显著变化；模拟实验结果表明河口底泥中的TN、TP明显高于其他两个湖区，并且有河口底泥的实验组加入藻浆的程度最严重，几种优势菌群的变化趋势和野外观测到的菌群变化趋势大体一致。拟杆菌门（Bacteroidetes）和厚壁菌门（Firmicutes）都呈现大幅度增加，而变形菌门（Proteobacteria）和放线菌门(Actinobacteria)的百分比都下降。 放线菌的数量变化明显，东太湖处理组中放线菌门(Actinobacteria)百分比增加的最多（22倍左右）。变形菌门（Proteobacteria）除东太湖和对照组恢复至于初始值大致相同，河口和湖心处理组依然还呈现下降趋势。拟杆菌门（Bacteroidetes）和厚壁菌门（Firmicutes）在各个处理组也都呈现不同变化趋势，其中拟杆菌门（Bacteroidetes）在东太湖处理组几乎回复到最初值。而东太湖处理组中厚壁菌门所占的百分比是初始值的近6倍。水体中不同细菌类群的影响是不同且细菌类群则难以在短期内恢复。