Unveiling the contribution of particle-associated non-cyanobacterial diazotrophs to N2 fixation in the upper mesopelagic North Pacific Gyre

Reeder, Christian F. ORCID: https://orcid.org/0000-0003-0866-3987; Filella, Alba ORCID: https://orcid.org/0000-0001-9675-8884; Voznyuk, Anna ORCID: https://orcid.org/0009-0005-1675-9577; Coët, Arthur ORCID: https://orcid.org/0009-0008-4674-6349; James, Reece C.; Rohrer, Tully ORCID: https://orcid.org/0000-0003-4720-0678; White, Angelicque E.; Berline, Léo; Grosso, Olivier; van Dijken, Gert ORCID: https://orcid.org/0000-0002-9587-6317; Arrigo, Kevin R. ORCID: https://orcid.org/0000-0002-7364-876X; Mills, Matthew M. ORCID: https://orcid.org/0000-0002-9738-5589; Turk-Kubo, Kendra A. ORCID: https://orcid.org/0000-0002-9847-7514; Benavides, Mar ORCID: https://orcid.org/0000-0001-9502-108X. 2025 Unveiling the contribution of particle-associated non-cyanobacterial diazotrophs to N2 fixation in the upper mesopelagic North Pacific Gyre. Communications Biology, 8 (1). 10.1038/s42003-025-07542-w

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Abstract/Summary

Dinitrogen (N 2 ) fixation supports marine life through the supply of reactive nitrogen. Recent studies suggest that particle-associated non-cyanobacterial diazotrophs (NCDs) could contribute significantly to N 2 fixation contrary to the paradigm of diazotrophy as primarily driven by cyanobacterial genera. We examine the community composition of NCDs associated with suspended, slow, and fast-sinking particles in the North Pacific Subtropical Gyre. Suspended and slow-sinking particles showed a higher abundance of cyanobacterial diazotrophs than fast-sinking particles, while fast-sinking particles showed a higher diversity of NCDs including Marinobacter , Oceanobacter and Pseudomonas . Using single-cell mass spectrometry we find that Gammaproteobacteria N 2 fixation rates were higher on suspended and slow-sinking particles (up to 67 ± 48.54 fmol N cell⁻¹ d⁻¹), while putative NCDs’ rates were highest on fast-sinking particles (121 ± 22.02 fmol N cell⁻¹ d⁻¹). These rates are comparable to previous diazotrophic cyanobacteria observations, suggesting that particle-associated NCDs may be important contributors to pelagic N 2 fixation.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1038/s42003-025-07542-w
ISSN:	2399-3642
Date made live:	19 Mar 2025 13:43 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/539108

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