CSIR-National Institute of Oceanography, Dona Paula, Goa, 403 004, India.
Max-Planck Institute for Marine Microbiology, Celsiusstrasse 1, D-28359, Bremen, Germany.
Nat Commun. 2018 Mar 28;9(1):1265. doi: 10.1038/s41467-018-03607-z.
The fate of the enormous amount of reactive nitrogen released to the environment by human activities in India is unknown. Here we show occurrence of seasonal stratification and generally low concentrations of dissolved inorganic combined nitrogen, and high molecular nitrogen (N) to argon ratio, thus suggesting seasonal loss to N in anoxic hypolimnia of several dam-reservoirs. However, N-experiments yielded low rates of denitrification, anaerobic ammonium oxidation and dissimilatory nitrate reduction to ammonium-except in the presence of methane (CH) that caused ~12-fold increase in denitrification. While nitrite-dependent anaerobic methanotrophs belonging to the NC10 phylum were present, previously considered aerobic methanotrophs were far more abundant (up to 13.9%) in anoxic hypolimnion. Methane accumulation in anoxic freshwater systems seems to facilitate rapid loss of reactive nitrogen, with generally low production of nitrous oxide (NO), through widespread coupling between methanotrophy and denitrification, potentially mitigating eutrophication and emissions of CH and NO to the atmosphere.
人类活动向印度环境中释放了大量的活性氮，其归宿尚不清楚。本研究表明，在几个水坝水库缺氧的下中层水体中，活性氮季节性消失，导致溶解无机结合氮和高氮（N）与氩（Ar）比值通常较低。然而，N 实验的反硝化、厌氧氨氧化和硝酸盐异化还原为铵的速率较低，除了甲烷（CH）的存在会导致反硝化作用增加约 12 倍。尽管存在属于 NC10 门的亚硝酸盐依赖型厌氧甲烷氧化菌，但先前被认为是好氧甲烷氧化菌的数量在缺氧的下中层水体中要丰富得多（高达 13.9%）。在缺氧的淡水系统中，甲烷的积累似乎通过甲烷氧化作用和反硝化作用的广泛偶联，促进了活性氮的快速损失，通常会产生较少的氧化亚氮（NO），从而减轻富营养化以及 CH 和 NO 向大气的排放。
