Biodiversity in Motion: How Marine Diversity Shapes the Ocean’s Active Carbon Pump

Abstract

The biological carbon pump plays a central role in regulating atmospheric CO2 by transporting carbon from the surface ocean to depth. Although diel vertical migration and the Active Migrant Pump (AMP) are increasingly recognized as important components of carbon sequestration, previous reviews have focused primarily on carbon fluxes and individual migrant groups, with less attention to how taxonomic and functional biodiversity, community composition, biomass, and environmental forcing interact to shape active carbon transport. Here, we synthesize current knowledge on the biodiversity underlying the AMP and evaluate how organismal identity, functional traits, behavior, life history, and biomass influence the magnitude, pathways, and efficiency of active carbon export. We further examine major mechanisms of active carbon transport and their links to biodiversity across ocean basins, and assess how climate-driven changes in species composition, migratory behavior, and ecosystem structure may alter the AMP. The review identifies three major knowledge gaps: substantial uncertainty in the biomass of migrating organisms, insufficient taxonomic resolution of key migrant groups, and limited incorporation of biodiversity and functional traits into carbon-flux models. Active carbon transport is determined by interactions between biodiversity, biomass, organismal traits, migration behavior, and environmental factors. Explicit integration of these dimensions into biogeochemical models is therefore essential for improving estimates of the AMP and predicting its response to ocean change.