Water mass specific genes dominate the Southern Ocean microbiome
- Emile Faure
- Jolann Pommellec
- Cyril Noel
- Alexandre Cormier
- Lisa-Marie Delpech
- A. Murat Eren
- Antonio Fernandez-Guerra
- Chiara Vanni
- Marion Fourquez
- Marie-Noëlle Houssais
- Ulysse Guyet
- Corinne Da Silva
- Frederick Gavory
- Aude Perdereau
- Karine Labadie
- Patrick Wincker
- Julie Poulain
- Christel Hassler
- Yajuan Lin
- Nicolas Cassar
- Loïs Maignien
2026-03-09
The Southern Ocean (SO) plays a key role in regulating global biogeochemical cycles and climate, yet microbial genes sustaining its biological activity remain poorly characterized. We introduce a microbial genes collection from 218 metagenomes sampled during the Antarctic Circumnavigation Expedition, the majority of which are missing from functional databases. 38% even lack homologs in current reference marine gene catalogs, defining a singular genetic seascape. We show that SO gene assemblages exhibit a common polar signature with the Arctic Ocean while being structured by water masses at the SO-scale. We analyze genomic markers of diverse SO biomes, focusing on dimethylsulphoniopropionate (DMSP) cleavage by polar-adapted bacteria, organic matter consumption in the blooming Mertz polynya and adaptation to polar conditions in the ubiquitous bacteria Pelagibacter. Our work takes a step towards a comprehensive understanding of SO’s plankton ecology and evolution, capturing the current state of the unique microbial diversity in this rapidly changing Ocean.