河口潮滩湿地硝酸盐异化还原成铵过程及其影响机理研究

Nitrogen transformations in estuarine and intertidal environments have attracted many attentions and been identified as a hot scientific issue. However, dissimilatory nitrate reduction to ammonium (DNRA) and associated influencing mechanism in estuarine and intertidal environments remain unclear so far. Therefore, the Yangtze estuarine and intertidal wetland is selected as the study area. The objectives of this project are (1) to study the spatiotemporal distributions of DNRA in the estuarine and tidal environment with nitrogen stable isotopic techniques, (2) to study the diversities, compositions, abundances, and distributions of DNRA bacteria with molecular technology, (3) to quantify the coupled correlations between the DNRA rates and DNRA functional microbes, (4) to reveal the main environmental variables and potential mechanisms regulating DNRA process, and (5) to explore the contributions of DNRA to the dissimilatory nitrate reduction processes in the study area. This project is of significance to further understanding of nitrate transformation pathways and associated influencing mechanisms in the estuarine and intertidal ecosystems. Also, it can provide important guidance for protecting water resource and ecological governance in these environments.

河口潮滩环境中氮循环关键过程研究是当前广泛关注的热点科学问题。然而，河口潮滩环境的硝酸盐异化还原成铵（DNRA）过程及其影响机理至今仍不清楚。鉴于此，本项目拟以长江口潮滩作为典型研究区，运用氮稳定同位素示踪和分子生物学技术，研究河口潮滩环境中DNRA的空间变异与时间变化特征；分析DNRA功能菌多样性和丰度及其分布特征；定量剖析DNRA功能菌与DNRA速率之间的耦合关系；阐明影响DNRA过程的关键环境因子及其作用机理，并探讨河口潮滩DNRA在硝酸盐还原过程中的贡献。通过本项目的开展，不仅可深化对河口潮滩硝酸盐转化途径与影响机制的理论认识，而且可为河口地区水资源保护和生态治理提供重要的科学依据。

河口潮滩环境中氮循环关键过程研究是当前广泛关注的热点科学问题。然而，河口潮滩环境的硝酸盐异化还原成铵（DNRA）过程及其影响机理至今仍不清楚。本项目运用氮稳定同位素示踪和分子生物学技术，研究河口潮滩环境中DNRA的空间变异与时间变化特征；分析DNRA功能菌多样性和丰度及其分布特征；定量剖析DNRA功能菌与DNRA速率之间的耦合关系；阐明影响DNRA过程的关键环境因子及其作用机理。采用氮同位素研究了长江口崇明东滩湿地DNRA速率为0.17-0.71 nmol N g–1 h–1，呈现出由低潮潮滩向高潮滩先升高后降低的变化规律，土壤基质和营养盐的变化是影响DNRA率及其功能基因丰度的重要因素。然而，对处于中亚热带的闽江口进一步研究，发现DNRA速率为0.45-2.92 nmol N g–1 h–1，要高于长江口崇明东滩湿地，说明处于低纬度气温更高的河口环境，DNRA更加活跃，尤其原因是温度较高会增加土壤可溶性有机碳含量，进而促进了DNRA微生物的活性。因此，通过对纬度梯度下不同气候带进行深入研究，发现DNRA速率从温带到热带地区增加，年平均温度是影响DNRA的最重要的因素。上述研究结果深化了对河口潮滩DNRA过程及其影响机制的理论认识，也为河口水资源保护和生态治理提供重要的科学依据。