Small phytoplankton contribute greatly to CO2-fixation after the diatom bloom in the Southern Ocean

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