Clara M Flintrop

Abstract The marine biological carbon pump is mainly driven by the interplay between aggregate sinking velocity and remineralization. Sinking velocity of natural marine aggregates is not routinely measured but often calculated using Stokes′ law, which does not consider size-dependent changes in porosity. We analyzed the flow fields around 81 in situ-formed aggregates using Particle Image Velocimetry (PIV) to determine the factors controlling aggregate settling.

Highlights • The southern Weddell Sea had low primary production and carbon export • FeMn input relieved FeMn co-limitation and changed species composition • This led to higher primary production and highly carbon-rich aggregates Summary Next to iron (Fe), recent phytoplankton-enrichment experiments identified manganese (Mn) to (co-)limit Southern Ocean phytoplankton biomass and species composition.

Abstract The marine biological carbon pump is driven by the interplay between particle sinking velocity and remineralisation. Despite its importance, sinking velocity of natural marine aggregates is not routinely measured, but often calculated from aggregate size and density using Stokes′ law.