水陆交错带厌氧氨氧化反应热区的发生机理与关键驱动机制

厌氧氨氧化及反应热区在自然界的发现，显著改变了人们对氮循环的认识。海洋厌氧氨氧化热区发生于洋流交汇区，对氮气的贡献率超50%；在陆地系统，厌氧氨氧化反应热区发生于水陆交错带，氮气贡献率达37%。目前对厌氧氨氧化反应热区的研究局限于发现层面，对其发生机理还未见报道。.前期研究发现底物亚硝酸盐是厌氧氨氧化反应热区发生的限速因子。间歇性水位波动能促进好氧氨氧化过程，为厌氧氨氧化反应提供更多亚硝酸盐；底物氨氮不足时，硝酸盐异化还原成铵（DNRA）又将亚硝酸盐还原为氨氮，实现底物间的动态调配。因此，推测好氧氨氧化与DNRA的耦合作用很可能是水陆交错带厌氧氨氧化反应热区发生的关键驱动机制。.本项目拟采用新开发的同位素示踪方法分别精确测定不同氮循环过程的反应速率，同时采用高通量测序分析相应功能基因，深入剖析厌氧氨氧化反应热区的发生机理与关键微生物驱动机制。研究结果将对陆地氮循环模式和通量计算有重要意义。

The discovery of anaerobic ammonium oxidation (anammox) hotspot in nature has greatly changed our understanding of the traditional microbial nitrogen cycle. More than 50 percent of nitrogen gas (N2) produced in marine ecosystem can be attributed to the anammox hotspot occurring in intersection area of ocean currents. In terrestrial ecosystems, anammox hotspot occurred in riparian zone with the contribution up to 37 percent to N loss. However, the key driving mechanism and related microbial process of anaerobic ammonium oxidation hotspot are still not known. .Previous study of the project revealed that nitrite was the limiting factor of the activity in the anammox hotspot. The intermittent fluctuations of the water level in the riparian zone may provide substrate nitrite for anammox bacteria through aerobic ammonium oxidation. When the ammonium is insufficient, dissimilatory nitrate reduction to ammonium (DNRA) could also consume the toxic nitrite, and meanwhile provide ammonium for anammox. Thus, we speculate that aerobic ammonium oxidation coupled with DNRA may be the key driving microbial process for the occurrence of anammox hotspot in the riparian zone. .This project aims to explore the driving mechanism of anammox hotspot in the riparian zone. Isotope tracer technique will be used to detect the activities of various microbial N cycle process. The key functional gene of each N cycle microorganism will be analyzed through high-throughput sequencing techniques. Through the above methods, we aim to find out the key driving mechanism and related microbial process (aerobic ammonium oxidation and DNRA) of the anammox hospot. The results of this project would supplement and revise the theory system of nitrogen cycle in terrestrial ecosystem and provide theoretical basis for the calculation of global nitrogen cycle balance and flux.