This study investigated the contribution of different phytoplankton groups to CO2 fixation in the Southern Ocean, specifically around the Kerguelen plateau. After a diatom bloom, smaller phytoplankton (<20 µm), including prymnesiophytes, prasinophytes, and small diatoms, exhibited faster growth rates than larger diatoms. These smaller cells contributed significantly (41–70%) to overall CO2 fixation. Analysis of pigment vertical distribution suggested grazing as a potential mechanism for small phytoplankton export. The findings underscore the importance of small phytoplankton in Southern Ocean carbon cycling.

Solène Irion, Urania Christaki, Hugo Berthelot, Stéphane L’Helguen, Ludwig Jardillier