Bertilsson, Stefan
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
Abstract
Due to climate change, sea ice more commonly retreats over the shelf breaks in the Arctic Ocean, impacting sea ice-pelagic-benthic coupling in the deeper basins. Nitrogen fixation (the reduction of dinitrogen gas to bioavailable ammonia by microorganisms called diazotrophs) is reported from Arctic shelf sediments but is unknown from the Arctic deep sea. We sampled five locations of deep-sea (900-1500 m) surface sediments in the central ice-covered Arctic Ocean to measure potential nitrogen fixation through long-term (> 280 days) stable-isotope (N-15(2)) incubations and to study diazotroph community composition through amplicon sequencing of the functional marker gene nifH. We measured low but detectable nitrogen fixation rates at the Lomonosov Ridge (0.6 pmol N g(-1) day(-1)) and the Morris Jessup Rise (0.4 pmol N g(-1) day(-1)). Nitrogen fixation was observed in sediments with the lowest organic matter content and bacterial abundance, and where sulphate-reducers like Desulfuromonadia and Desulfosporosinus sp. were prominent. Most nifH genes were distantly related to known diazotrophs. In this study, we show a potential for nitrogen fixation in Arctic bathypelagic sediments, considerably extending the known biome of marine nitrogen fixation. It raises the question of the significance of low but potentially widespread nitrogen fixation in deep-sea sediments.
Keywords
benthic diazotrophs; deep-sea; nifH; stable isotope-tracing; sulphate-reducing bacteria; sympagic-pelagic-benthic-coupling
Published in
Environmental Microbiology Reports
2025, volume: 17, number: 5, article number: e70173
Publisher: WILEY
SLU Authors
UKÄ Subject classification
Environmental Sciences
Publication identifier
- DOI: https://doi.org/10.1111/1758-2229.70173
Permanent link to this page (URI)
https://res.slu.se/id/publ/143764