Evidence of limited N2 fixation in the Southern Ocean

Biological nitrogen fixation is an important source of new nitrogen, influencing ocean fertility and carbon uptake. While recently documented in Arctic waters, its role in the Southern Ocean remains uncertain. We measured nitrogen fixation along the Western Antarctic Peninsula and at Palmer Station over two austral summer months. Rates from 15N2 assay were below conservative detection limits but detectable under less stringent detection thresholds. Continuous acetylene reduction assay provided further support. nifH gene sequencing identified Gammaproteobacteria as the dominating identified diazotrophs, while Epsilonproteobacteria contributed disproportionally to nifH expression when putative nitrogen fixation was highest. Combined with environmental observations, we hypothesize that vertical water mixing resuspended sediments into the water column and contributed to the limited nitrogen fixation. Given the sporadic and low rates, further research is needed to determine whether nitrogen fixation plays a minor role or represents an overlooked process with biogeochemical significance in the Southern Ocean.

Full Text

FilePagesSizeAccess
Publisher's official version
92 Mo
Transparent Peer Review file
6304 Ko
Supplemental Information
3457 Ko
Description of Additional Supplementary Files
17 Ko
Supplementary Data 1
-230 Ko
Supplementary Data 2
-13 Ko
How to cite
Gu Shuai, Berthelot Hugo, Lin Yajuan, Tang Weiyi, Robidart Julie, Eren A. Murat, Ducklow Hugh W., Cassar Nicolas (2025). Evidence of limited N2 fixation in the Southern Ocean. Communications Earth & Environment. 6 (1). 264 (9p.). https://doi.org/10.1038/s43247-025-02225-0, https://archimer.ifremer.fr/doc/00947/105838/

Copy this text