Over 40 years have passed since the anaerobic oxidation of ammonium with nitrite reduction was first proposed. Currently known to be a globally important marine N sink, anammox bacteria are found distributed among a diverse variety of soils and sediments. However, the use of techniques which enable the detection of anammox as well as other pathways are necessary to quantify the full extent of N removal in a system. Detection of anammox activity in sea ice suggests that this may be an active process in permafrost, where anammox bacteria have also been identified. In the context of current warming trends, a thorough characterization of the nitrogen cycle in permafrost soils is needed in order to quantify effects on organic matter mineralization and ultimately, carbon dioxide release as a positive feedback mechanism to global warming.
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