Arthur Coët (MIO Biogeochemistry) will submit his doctoral thesis on wednesday 18 march 2026 à 14h00, at l'Hexagone (Luminy, Marseille) on the following topic: Dynamics and architecture of diazotrophs particle colonization. You are warmly invited to attend the defence and the thesis reception that will follow.
Abstract
The ocean plays a central role in global carbon and nitrogen cycling, largely driven by microbial activity. Among these processes, nitrogen fixation converts inert N₂ into bioavailable forms that sustain marine food webs. While cyanobacterial diazotrophs have long been studied, non-cyanobacterial diazotrophs (NCDs) are now recognized as widespread and potentially major contributors to the marine nitrogen cycle.
This thesis investigates the hypothesis that NCDs exploit marine particles as microhabitats that protect nitrogenase from oxygen. Combining in situ chemotaxis assays in the Arctic Ocean, quantitative cell tracking, and high-resolution imaging of aggregates, this work reveals how microbial behavior, spatial organization, and metabolism interact.
Together, the results demonstrate that marine particles act as dynamic hotspots supporting non-cyanobacterial N₂ fixation in the ocean.
Composition of the jury
- Leila TIRICHINE - Nantes University, CNRS - Reviewer
- Josep Mª GASOL PIQUÉ - ICM, CSIC, Barcelona - Reviewer
- Lasse RIEMANN - University of Copenhagen - Examiner
- Hans-Peter GROSSART - IGB, Berlin - Examiner
- Jean-Christophe POGGIALE - MIO, CNRS, Marseille - Jury President
- Mar BENAVIDES - MIO, IRD, Marseille - Supervisor
- Pierre RONCERAY - CINaM, CNRS, Marseille - Co-supervisor
Zoom link
Meeting ID: 372 409 7500
