Salp blooms drive strong increases in passive carbon export in the Southern Ocean

The Southern Ocean significantly contributes to the global biological carbon pump (BCP). Salps, particularly *Salpa thompsoni*, are crucial grazers producing large, fast-sinking fecal pellets. This study quantifies the impact of salp blooms on microbial dynamics and the BCP by comparing locations with and without salp blooms. Salp blooms occur alongside phytoplankton dominated by diatoms or prymnesiophytes, depending on water mass characteristics. Their grazing is comparable to microzooplankton during early blooms, decreasing primary production by ~1/3. Particle export is 2- to 8-fold higher in salp waters, exporting up to 46% of primary production out of the euphotic zone. BCP efficiency increases from 5 to 28% in salp areas, among the highest globally.

Moira Décima, Michael R. Stukel, Scott D. Nodder, Andrés Gutiérrez-Rodríguez, Karen E. Selph, Adriana Lopes dos Santos, Karl Safi, Thomas B. Kelly, Fenella Deans, Sergio E. Morales, Federico Baltar, Mikel Latasa, Maxim Y. Gorbunov, Matt Pinkerton