Abstract

Phytoplankton are key elements in the oceanic carbon cycle. They assist with roughly fifty percent of global productivity and enable carbon storage through the biological pump. This study shows phytoplankton carbon sequestration across spatially discrete oceanic zones: the coastal shelves, the oligotrophic open ocean, and the upwelling systems. To evaluate spatial-temporal variability during 2010-2020, satellite-derived chlorophyll-a concentrations (MODIS-AQUA), other datasets, and in-situ observations were integrated with a coupled physical-biogeochemical model. The analysis results display substantial variance in the biomass and productivity of phytoplankton owing to the change in their nutrient fluxes, light, SST, and mixed layer depth. The upwelling regions had higher primary production and carbon export efficiencies than the rest of the ocean, with increased flux of POC due to diatom-dominated communities. On the other hand, oligotrophic gyres were delimited by stagnant low biomass picophytoplankton, which diminished vertical carbon export. These results show a marked difference in the contributions of the oceanic provinces to carbon sequestration, indicating that changing climate conditions could impact biogeochemical processes. The research enhances understanding of the oceanic carbon sink and the need for spatially explicit carbon cycle models for climate mitigation.

Keywords: Phytoplankton, Carbon, Ocean, Picophytoplankton, Biomass, and Climate mitigation