Production of N2 through anaerobic ammonium oxidation coupled to nitrate reduction in marine sediments
Production of N2 through anaerobic ammonium oxidation coupled to nitrate reduction in marine sediments
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DOI：
10.1128/aem.68.3.1312-1318.2002
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发表时间：
2002-03-01
影响因子：
4.4
通讯作者：
Dalsgaard, T
中科院分区：
文献类型：
--
作者：
Thamdrup, B;Dalsgaard, T
在全球氮循环中，细菌反硝化作用被认为是将固定氮转化为大气氮N-2的唯一定量重要过程，从而影响生态系统功能和全球生物地球化学的许多方面。然而，我们发现海洋氮循环的一个新过程，即氨的厌氧氧化与硝酸盐还原相结合，对海洋沉积物中N-2的产生有重要贡献。用n -15标记的硝酸盐或铵进行孵育表明，在该过程中，硝态氮和铵态氮一对一配对形成N-2，这明显将该过程与反硝化分离开来。亚硝酸盐是瞬时积累的，可能是铵的氧化剂，因此该过程类似于废水生物反应器中已知的厌氧氨氧化过程。厌氧氨氧化占两个典型陆架站点N-2总产量的24%和67%，而在富营养化海岸海湾中，厌氧氨氧化可检测到，但相对于反硝化作用不显著。然而，厌氧氨氧化速率在沿海沉积物中比在最深的地点更高，并且不同地点对N-2产生的相对贡献的变化与反硝化速率的巨大差异有关。因此，厌氧氨氧化和反硝化在N-2生产中的相对重要性似乎受到其还原底物的可用性的调节。通过将氮从氨直接分流到N-2，厌氧氨氧化促进了海洋中固定氮的去除。这一过程可以解释缺氧水体和沉积物中氨的缺乏，并可能对海洋氮收支有重要贡献。
In the global nitrogen cycle, bacterial denitrification is recognized as the only quantitatively important process that converts fixed nitrogen to atmospheric nitrogen gas, N-2, thereby influencing many aspects of ecosystem function and global biogeochemistry. However, we have found that a process novel to the marine nitrogen cycle, anaerobic oxidation of ammonium coupled to nitrate reduction, contributes substantially to N-2 production in marine sediments. Incubations with N-15-labeled nitrate or ammonium demonstrated that during this process, N-2 is formed through one-to-one pairing of nitrogen from nitrate and ammonium, which clearly separates the process from denitrification. Nitrite, which accumulated transiently, was likely the oxidant for ammonium, and the process is thus similar to the anammox process known from wastewater bioreactors. Anaerobic ammonium oxidation accounted for 24 and 67% of the total N-2 production at two typical continental shelf sites, whereas it was detectable but insignificant relative to denitrification in a eutrophic coastal bay. However, rates of anaerobic ammonium oxidation were higher in the coastal sediment than at the deepest site and the variability in the relative contribution to N-2 production between sites was related to large differences in rates of denitrification. Thus, the relative importance of anaerobic ammonium oxidation and denitrification in N-2 production appears to be regulated by the availability of their reduced substrates. By shunting nitrogen directly from ammonium to N-2, anaerobic ammonium oxidation promotes the removal of fixed nitrogen in the oceans. The process can explain ammonium deficiencies in anoxic waters and sediments, and it may contribute significantly to oceanic nitrogen budgets.