Burrowing deeper into benthic nitrogen cycling: the impact of bioturbation on nitrogen fixation coupled to sulfate reduction
Benthic environments are thought to be characterized by an overall loss of dinitrogen, mainly via denitrification, while N2-fixation is considered to be significant only in localized habitats such as phototrophic microbial mats or rhizospheres. However, many sulfate-reducing bacteria, which are abundant in marine sediments, possess the genetic capacity to fix N2. Bertics and colleagues demonstrate that sub-surface N2-fixation in sediments bioturbated by the ghost shrimp Neotrypaea californiensis occurs at high rates, leading to an input of new nitrogen into the system. Given the ubiquity of bioturbation, subsurface N2-fixation may play an important role in marine nitrogen and carbon cycles.
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