Dynamics of diazotroph particle colonization in the Arctic Ocean

Arctic warming is melting sea ice, releasing nutrients and boosting primary productivity, which increases nitrogen demand. Diazotrophs, microorganisms that convert atmospheric nitrogen into bioavailable forms, are essential for maintaining nitrogen levels. With rising nitrogen consumption, diazotroph nitrogen fixation will become critical for sustaining productivity in future nutrient-poor oceans. Unlike cyanobacterial diazotrophs that photosynthesize, non-cyanobacterial diazotrophs (NCDs) rely on organic matter. Although NCDs dominate many ecosystems, their interactions with Arctic marine particles remain poorly understood. This study investigates the chemotactic behavior and colonization dynamics of diazotrophs in the Arctic Ocean using an adapted In Situ Chemotaxis Assay with alginate and agarose artificial particles. Seawater from the Barents Sea was analyzed via nifH and 16S rRNA gene sequencing. Gammaproteobacteria rapidly colonized alginate, showing strong attraction to algal polysaccharides, abundant in the Arctic, while non-diazotrophic bacteria showed no preference. These results reveal niche partitioning within the microbial community and highlight the potential for increased N₂ fixation associated with algal particles. As the ice cover retreats, organic matter from algal blooms and glacial runoff is poised to expand habitats for particle-associated diazotrophs, potentially reshaping nutrient cycling and boosting primary production. Grasping these interactions is pivotal for predicting the Arctic Ocean's response to climate change.

Presentation Preference: Oral

Primary Presenter: Arthur Coët, Mediterranean Institute of Oceanography (arthur.coet@mio.osupytheas.fr)

Authors:

Arthur Coët, Aix-Marseille Université, Turing Center for Living Systems  (arthur.coet@mio.osupytheas.fr)

Cécile Carpaneto Bastos, Mediterranean Institute of Oceanography  (cecile.carpaneto-bastos@mio.osupytheas.fr)

Mathias Lechelon, Aix-Marseille Université  (mathias.LECHELON@univ-amu.fr)

Ruth Hawley, School of Ocean and Earth Science, University of Southampton  (rh3g22@soton.ac.uk)

Maeve C. Lohan, School of Ocean and Earth Science, University of Southampton  (M.Lohan@soton.ac.uk)

Pierre Ronceray, Centre interdisciplinaire de nanoscience de Marseille, Turing Center for Living Systems  (pierre.RONCERAY@univ-amu.fr)

Claire Mahaffey, School of Environmental Sciences, University of Liverpool  (mahaffey@liverpool.ac.uk)

Mar Benavides, National Oceanography Centre, European Way, Southampton, Turing Center for Living Systems  (Mar.Benavides@noc.ac.uk)