Assessing Zooplankton Communities' Influence on Particulate Organic Carbon Concentration

Zooplankton play a key role in setting the particulate organic carbon (POC) distribution in the ocean, but this role remains poorly quantified on large scales due to the complexity of zooplankton ecosystems and the sparsity and variability of observations. We address this by applying boosted regression trees to a global in situ zooplankton image database from the Underwater Vision Profiler 5 and an Argo float and satellite-derived POC product. We compute taxonomic, morphological, and trophic community metrics, then identify three metrics—abundance, mean gray level, taxonomic evenness—that explain almost half of the spatial variability in the vertical concentration gradients of small POC (<100 μm). Partial dependence analysis and the consistency of the identified relationships with known zooplankton-mediated particle-processing pathways suggest mechanistically interpretable ecological linkages. These results advance quantification of zooplankton communities' influence on ocean carbon cycling and indicate carbon-cycle-relevant zooplankton community properties for improving ocean biogeochemical models.