Quantifying nitrogen fixation by heterotrophic bacteria in sinking marine particles

Subhendu Chakraborty (), Ken H. Andersen, André W. Visser, Keisuke Inomura, Michael J. Follows and Lasse Riemann ()
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Subhendu Chakraborty: University of Copenhagen
Ken H. Andersen: Technical University of Denmark
André W. Visser: Technical University of Denmark
Keisuke Inomura: University of Rhode Island
Michael J. Follows: Atmospheric and Planetary Sciences, MIT
Lasse Riemann: University of Copenhagen

Nature Communications, 2021, vol. 12, issue 1, 1-14

Abstract: Abstract Nitrogen ( $${{\rm{N}}}_{2}$$ N 2 ) fixation by heterotrophic bacteria associated with sinking particles contributes to marine N cycling, but a mechanistic understanding of its regulation and significance are not available. Here we develop a mathematical model for unicellular heterotrophic bacteria growing on sinking marine particles. These bacteria can fix $${{\rm{N}}}_{2}$$ N 2 under suitable environmental conditions. We find that the interactive effects of polysaccharide and polypeptide concentrations, sinking speed of particles, and surrounding $${{\rm{O}}}_{2}$$ O 2 and $${{{\rm{NO}}}_{3}}^{-}$$ NO 3 − concentrations determine the $${{\rm{N}}}_{2}$$ N 2 fixation rate inside particles. $${{\rm{N}}}_{2}$$ N 2 fixation inside sinking particles is mainly fueled by $${{{\rm{SO}}}_{4}}^{2-}$$ SO 4 2 − respiration rather than $${{{\rm{NO}}}_{3}}^{-}$$ NO 3 − respiration. Our model suggests that anaerobic processes, including heterotrophic $${{\rm{N}}}_{2}$$ N 2 fixation, can take place in anoxic microenvironments inside sinking particles even in fully oxygenated marine waters. The modelled $${{\rm{N}}}_{2}$$ N 2 fixation rates are similar to bulk rates measured in the aphotic ocean, and our study consequently suggests that particle-associated heterotrophic $${{\rm{N}}}_{2}$$ N 2 fixation contributes significantly to oceanic $${{\rm{N}}}_{2}$$ N 2 fixation.

Date: 2021
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Persistent link: https://EconPapers.repec.org/RePEc:nat:natcom:v:12:y:2021:i:1:d:10.1038_s41467-021-23875-6

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DOI: 10.1038/s41467-021-23875-6

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