Denitrification, anaerobic ammonium oxidation and dissimilatory nitrate reduction to ammonium (DNRA) are important microbial processes determining the fate of nitrogen (N) in estuaries. This study examined these processes in sediments of the York River Estuary, a tributary of Chesapeake Bay, and investigated environmental and microbial drivers of the rates of denitrification and DNRA. Nitrate reduction followed a consistent pattern throughout the year and across the estuary with nitrogen removal, primarily through denitrification, decreasing from the head of the estuary to the mouth and nitrogen retention, through DNRA, following the opposite pattern. At the mouth of the estuary, nitrogen retention was consistently higher than nitrogen removal. Denitrification rates showed strong linear relationships with concentrations of organic matter, nitrate and chlorophyll a, and the abundance of the nirS gene. DNRA rates were best correlated with the relative abundance of three bacterial families, Anaerolineaceae,Ectothiorhodospiraceae and Prolixibacteraceae, which carry the nrfA gene. The controls responsible for retention or removal of N from an estuary are complex, involving both geochemical and microbial factors. The N retained within estuaries may support primary production and seasonal algae blooms and result in estuarine eutrophication.

中文翻译：

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约克河口微生物介导的氮去除和保留

反硝化、厌氧氨氧化和异化硝酸盐还原成铵 (DNRA) 是决定河口氮 (N) 归宿的重要微生物过程。本研究检查了切萨皮克湾支流约克河口沉积物中的这些过程，并调查了反硝化速率和 DNRA 的环境和微生物驱动因素。全年和整个河口的硝酸盐减少遵循一致的模式，主要通过反硝化作用去除氮，从河口的头部到嘴巴减少，氮保留通过 DNRA，遵循相反的模式。在河口，氮保留量始终高于脱氮量。反硝化速率与有机物浓度呈强线性关系，a，以及nirS基因的丰度。DNRA率最好的三个细菌科，相对丰度相关Anaerolineaceae，Ectothiorhodospiraceae和Prolixibacteraceae，其携带nrfA基因。负责从河口保留或去除 N 的控制是复杂的，涉及地球化学和微生物因素。河口内保留的氮可能支持初级生产和季节性藻类大量繁殖，并导致河口富营养化。