Understanding the spatial and seasonal dynamics of nitrogen (N)-cycle microbial communities is pivotal for the knowledge of N biogeochemistry. The present study addressed the spatial−temporal variability of nitrification (bacterial and archaeal amoA) and denitrification (nirS, nirK, and nosZI) key genes, as well as of non-denitrifying nitrous oxide (N2O) reducers (nosZII), coupled with key environmental variables, in an estuarine ecosystem (Douro, NW Portugal). Samples were collected on a monthly basis over 1 yr, key physical-chemical parameters were measured, and specific functional gene abundances were assayed. The results revealed a clear seasonality for nirS, nosZII, and bacterial and archaeal amoA abundance, with an increase during the winter/spring seasons. This period was especially characterized by high levels of dissolved oxygen, low temperature, low salinity, and increased turbidity. Indeed, turbidity emerged as the key factor controlling the distribution of nirS, nosZII bacterial, and archaeal amoA abundance. In contrast, the abundance of nosZI increased during the summer, while nirK abundance was enhanced from the fall to late spring. Additionally, the availability of dissolved inorganic nitrogen nutrients had no commensurable effect on N-cycle functional genes. This study of the annual variation of Ncycle functional genes in a temperate Atlantic estuary provides a major contribution to the understanding of how environmental factors potentially influence the distribution and abundance of Ncycle microbial communities.

中文翻译：

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温带大西洋河口 N 循环功能基因的时空动态（葡萄牙杜罗）

了解氮 (N) 循环微生物群落的空间和季节性动态对于氮生物地球化学知识至关重要。本研究解决了硝化（细菌和古菌 amoA）和反硝化（nirS、nirK 和 nosZI）关键基因以及非反硝化氧化亚氮 (N2O) 还原剂 (nosZII) 的时空变异性，以及关键基因河口生态系统中的环境变量（葡萄牙西北部杜罗）。在 1 年内每月收集样品，测量关键的理化参数，并分析特定的功能基因丰度。结果显示 nirS、nosZII 以及细菌和古菌 amoA 丰度具有明显的季节性，并且在冬季/春季季节有所增加。这一时期的特点是溶解氧含量高，低温、低盐度和增加的浊度。事实上，浊度成为控制 nirS、nosZII 细菌和古菌 amoA 丰度分布的关键因素。相比之下，nosZI 的丰度在夏季增加，而 nirK 丰度从秋季到晚春增加。此外，溶解无机氮养分的可用性对 N 循环功能基因没有可比的影响。这项对温带大西洋河口 Ncycle 功能基因年度变化的研究为了解环境因素如何潜在影响 Ncycle 微生物群落的分布和丰度做出了重大贡献。和古菌 amoA 丰富。相比之下，nosZI 的丰度在夏季增加，而 nirK 丰度从秋季到晚春增加。此外，溶解无机氮养分的可用性对 N 循环功能基因没有可比的影响。这项对温带大西洋河口 Ncycle 功能基因年度变化的研究为了解环境因素如何潜在影响 Ncycle 微生物群落的分布和丰度做出了重大贡献。和古菌 amoA 丰富。相比之下，nosZI 的丰度在夏季增加，而 nirK 丰度从秋季到晚春增加。此外，溶解无机氮养分的可用性对 N 循环功能基因没有可比性的影响。这项对温带大西洋河口 Ncycle 功能基因年度变化的研究为了解环境因素如何潜在影响 Ncycle 微生物群落的分布和丰度做出了重大贡献。