Max Planck Institute for Marine Microbiology, Bremen, Germany.
Center for Biotechnology, Bielefeld University, Bielefeld, Germany.
Environ Microbiol. 2018 Dec;20(12):4486-4502. doi: 10.1111/1462-2920.14385. Epub 2018 Oct 16.
Coastal oceans receive large amounts of anthropogenic fixed nitrogen (N), most of which is denitrified in the sediment before reaching the open ocean. Sandy sediments, which are common in coastal regions, seem to play an important role in catalysing this N-loss. Permeable sediments are characterized by advective porewater transport, which supplies high fluxes of organic matter into the sediment, but also leads to fluctuations in oxygen and nitrate concentrations. Little is known about how the denitrifying communities in these sediments are adapted to such fluctuations. Our combined results indicate that denitrification in eutrophied sandy sediments from the world's largest tidal flat system, the Wadden Sea, is carried out by different groups of microorganisms. This segregation leads to the formation of N O which is advectively transported to the overlying waters and thereby emitted to the atmosphere. At the same time, the production of N O within the sediment supports a subset of Flavobacteriia which appear to be specialized on N O reduction. If the mechanisms shown here are active in other coastal zones, then denitrification in eutrophied sandy sediments may substantially contribute to current marine N O emissions.
沿海海洋接收大量人为固定氮（N），其中大部分在到达开阔海域之前就在沉积物中被反硝化。在沿海地区很常见的沙质沉积物似乎在催化这种 N 损失方面起着重要作用。可渗透沉积物的特点是平流孔隙水输送，它将大量有机物供应到沉积物中，但也会导致氧气和硝酸盐浓度的波动。人们对这些沉积物中的反硝化群落如何适应这种波动知之甚少。我们的综合结果表明，来自世界上最大的潮汐平原系统——瓦登海的富营养化沙质沉积物中的反硝化作用是由不同的微生物群完成的。这种隔离导致形成了可被平流输送到上覆水体并因此排放到大气中的 N O。与此同时，沉积物内 N O 的产生支持了一部分似乎专门从事 N O 还原的黄杆菌。如果这里显示的机制在其他沿海地区活跃，那么富营养化沙质沉积物中的反硝化作用可能会大大增加当前海洋 N O 的排放。
