| Abstrakt: |
Nitrogen fixation is an important process connecting the vast atmospheric pool of di‐nitrogen gas to the biosphere. Nitrogen fixation is an energy intensive process, and it is historically thought to occur only to meet nitrogen demands. However, over the last two decades, research has demonstrated that sediment nitrogen fixation occurs in a variety of coastal environments, including those where reduced nitrogen is abundant. This can be met with skepticism when nitrogen fixation is viewed solely as a nitrogen limitation relief mechanism. Here, I propose that coastal sediments are actually ideal environments for nitrogen fixation and synthesize ideas on why this is the case. My goal is to help the community embrace a new paradigm for sediment nitrogen fixation and to see it as an important and even expected process. In doing so, I hope to motivate future research on the spatial and temporal rate dynamics of sediment nitrogen fixation as well as on the sediment nitrogen fixation community composition and activity. Plain Language Summary: Nitrogen fixation is a microbially driven process that transforms gaseous di‐nitrogen gas into a bioavailable form of nitrogen that can promote growth. Typically, this process is thought to take place to help organisms meet their nitrogen demands in nitrogen deplete environments. Thus, in coastal sediments that are often rich in ammonium, it is thought that nitrogen fixation should not occur given the energetic costs. However, advances in methods have demonstrated that nitrogen fixation does occur in coastal sediments. Understanding the how and why of coastal sediment nitrogen fixation will help us better understand nitrogen cycling in general. Key Points: Coastal sediments provide ideal conditions for nitrogen fixationSediment nitrogen fixation may take place for reasons unrelated to nitrogen limitation, such as allowing microbes to maintain intracellular redox balanceNiche partitioning and microbial community relationships may provide helpful lenses in which to understand sediment nitrogen fixation [ABSTRACT FROM AUTHOR] |
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