Anammox bacteria drive fixed nitrogen loss in hadal trench sediments - pnas.org

Significance

Hadal trenches represent the deepest part of the oceans, apparently offering adverse conditions for life, given their high hydrostatic pressure and wide separation from the productive surface waters. However, focusing of reactive organic matter in trench axis sediments potentially promotes complex yet unexplored microbial communities and associated biogeochemical processes. We demonstrate that hadal sediments at depths reaching 10 km are hotbeds for anaerobic nitrogen transformations, dominated by the anammox process, extending the known depth range of this process by 6 km. The diversity and phylogeny of identified hadal anammox bacteria suggest that high hydrostatic pressure has not been a major evolutionary driver. Our results provide insights into hadal biogeochemistry and the ability of microbes to adapt to hydrostatic pressure.

Abstract

Benthic N₂ production by microbial denitrification and anammox is the largest sink for fixed nitrogen in the oceans. Most N₂ production occurs on the continental shelves, where a high flux of reactive organic matter fuels the depletion of nitrate close to the sediment surface. By contrast, N₂ production rates in abyssal sediments are low due to low inputs of reactive organics, and nitrogen transformations are dominated by aerobic nitrification and the release of nitrate to the bottom water. Here, we demonstrate that this trend is reversed in the deepest parts of the oceans, the hadal trenches, where focusing of reactive...

Your content is great. However, if any of the content contained herein violates any rights of yours, including those of copyright, please contact us immediately by e-mail at media[@]kissrpr.com.