Quantifying nitrogen fixation by heterotrophic bacteria in sinking marine particles
Subhendu Chakraborty1,2,3, Ken H Andersen4, André W Visser4
1Department of Biology, Marine Biological Section, University of Copenhagen, Helsingør, Denmark. schakraborty@bio.ku.dk.
Nature Communications
|July 3, 2021
Summary
Heterotrophic bacteria on sinking particles fix nitrogen ([Formula: see text]) in the ocean. Their activity is regulated by particle composition, sinking speed, and surrounding nutrient levels, significantly impacting marine nitrogen cycling.
Area of Science:
- Marine microbial ecology
- Biogeochemical cycling
- Mathematical modeling
Background:
- Nitrogen ([Formula: see text]) fixation by heterotrophic bacteria on sinking particles is crucial for marine nitrogen cycling.
- A detailed understanding of the regulation and significance of this process is lacking.
Purpose of the Study:
- To develop a mathematical model for unicellular heterotrophic bacteria on sinking marine particles.
- To investigate the factors regulating nitrogen ([Formula: see text]) fixation in these environments.
- To assess the contribution of particle-associated nitrogen ([Formula: see text]) fixation to oceanic nitrogen ([Formula: see text]) fixation.
Main Methods:
- Development of a mathematical model simulating unicellular heterotrophic bacteria growth on sinking particles.
- Analysis of interactive effects of polysaccharide/polypeptide concentrations, particle sinking speed, and surrounding nutrient levels ([Formula: see text], [Formula: see text]).
- Modeling of nitrogen ([Formula: see text]) fixation rates and respiration pathways within particles.
Main Results:
- Nitrogen ([Formula: see text]) fixation rates are determined by particle composition, sinking speed, and ambient nutrient concentrations.
- Nitrogen ([Formula: see text]) fixation is primarily fueled by anaerobic respiration within particles.
- Anoxic microenvironments within sinking particles support heterotrophic nitrogen ([Formula: see text]) fixation even in oxygenated waters.
Conclusions:
- Particle-associated heterotrophic nitrogen ([Formula: see text]) fixation is a significant contributor to overall oceanic nitrogen ([Formula: see text]) fixation.
- The model provides mechanistic insights into nitrogen ([Formula: see text]) cycling associated with marine particles.
- Anaerobic processes, including nitrogen ([Formula: see text]) fixation, can occur within sinking particles in the ocean.
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