河流生态系统纵向梯度上反硝化潜力及其关键微生物过程研究

A river network can be viewed as an open ecosystem interlinked longitudinally, laterally, and vertically by hydrologic processes, and it also plays a very important role in denitrification under the global nitrogen cycle context. In fact, denitrification is a process that diverse microorganisms utilize nitrogen oxides as electron acceptor to produce energy, therefore microorganisms are important participants and regulators of denitrification processes. However, our understanding of the correlations between denitrification activity and denitrifying microbial functional gene abundances is limit. The research project will be built upon our previous studies on identification of nitrogen sources in the Jinshui River with a length of 87 km, located in the south aspect of the Qinling Mts (Shaanxi Province), and we will investigate the primary environmental factors and denitrification using isotope pairing technique in water columns and sediments along the longitudinal gradient (from headwater to mouth of the river network). Additionally, we will quantify microbial community composition by employing denaturing gradient gel electrophoresis (DGGE) and abundance of corresponding genes (narG/napA, nirK/nirS, norB, nosZ) involved in denitrification processes using real-time quantitative PCR (RT-PCR) techniques. Afterwards, we will analyze the mechanism of denitrification responsive to the environmental factors and microbial processes along the longitudinal gradient in the river system. The research results will provide new knowledge of denitrification processes and its associated environmental factors and microbial processes in river ecosystem along the longitudinal gradient.

河流是由水文过程在纵向、横向和垂直向相互连接形成的开放生态系统，其反硝化过程在全球氮循环中发挥着重要作用。反硝化是微生物以氮氧化物为电子受体产生能量的过程，因此微生物是生态系统反硝化过程的参与者及调控者。目前反硝化过程与反硝化微生物关键过程的关联已成为河流生态学和全球氮循环研究热点。本项目以秦岭南坡金水河（全长87 km）为研究对象，通过对河流生态系统从源头到河口纵向梯度上水体及表层沉积物主要生态环境因子的分析，利用同位素配对技术研究其反硝化速率，并结合运用变性梯度凝胶电泳（DGGE）及实时定量PCR（RT-PCR）技术，分析参与反硝化过程微生物的相应酶编码基因（narG/napA、nirK/nirS、norB、nosZ），进而探讨河流纵向梯度上主要生态环境因子、反硝化潜力、关键微生物过程的关联。本研究将加深我们对河流生态系统纵向梯度上反硝化潜力与环境因子及微生物关键过程的认识。

河流是由水文过程在纵向、横向和垂直向相互连接形成的开放生态系统，其反硝化过程在全球氮循环中发挥着重要作用。微生物是生态系统反硝化过程的参与者及调控者，目前反硝化过程与反硝化微生物关键过程的关联已成为河流生态学和全球氮循环研究热点。本项目以秦岭南坡金水河和淇河为研究对象，通过对河流生态系统从源头到河口纵向梯度上水体及表层沉积物主要生态环境因子的分析，利用同位素配对技术研究其反硝化速率，并结合运用变性梯度凝胶电泳及实时定量PCR技术，分析参与反硝化过程微生物的相应酶编码基因（narG/napA、nirK/nirS、norB、nosZ），进而探讨河流纵向梯度上主要生态环境因子、反硝化潜力、关键微生物过程的关联。本研究将加深我们对河流生态系统纵向梯度上反硝化潜力与环境因子及微生物关键过程的认识。.研究结果显示，金水河和淇河硝酸盐还原、亚硝酸盐还原及氮矿化的潜在功能较强。人为干扰强度高的区域参与硝酸盐还原的基因丰度较高，而人为干扰强度低的区域参与有机质降解与合成的基因丰度较高。温度、水体硝态氮及有机碳含量对氮循环影响较大。人为干扰强度高的区域具有更高的硝化、反硝化、厌氧氨氧化速率、N2O溶存浓度、N2O净增量及功能基因丰度。氮素转化速率与功能基因丰度相关性不显著。温度、硝态氮、铵态氮、C/N、铁离子是影响硝化及硝酸盐异化还原速率及功能基因丰度的重要因子。其中C/N在调控硝酸盐异化还原过程中起到了重要作用。高温、高浓度的硝态氮会抑制某些反硝化微生物群落结构多样性，而高的TOC会使某些反硝化微生物群落结构多样性升高。narG和nirS微生物群落多样性与反硝化速率呈负相关。碳源的增加使反硝化潜力与反硝化功能基因丰度显著提高，而氮源的增加以及低温处理对反硝化的影响不大。该研究将加深对河流生态系统氮循环及微生物关键过程的认识，并从微生物角度揭示人为干扰对氮元素地球化学循环的影响。