Program

The oceanic biological pump drives photosynthetically produced organic matter from the surface layer to depth sequestration via sinking particles which main composed of phytoplankton pellets and organic aggregates. However, the proportions of the estimated overall particulate organic carbon (POC) flux contributed by phytoplankton and zooplankton fecal pellets are highly variable with different temporal and spatial scales. Here, we report their contributions to POC flux in coast of the East China Sea (ECS) during a spring bloom and in continental shelf of the northern South China Sea (SCS) during summer. We measured phytoplankton abundance, sinking rates and zooplankton fecal pellets density, sinking, grazing and egestion rates. And then POC fluxes from phytoplankton and zooplankton fecal pellets were estimated. In addition, floating sediment traps were deployed more than 70 hours at two continental shelf sites in the northern SCS. The results show that phytoplankton sinking rates (up to about 10 m.day^-1) was 10 times than control sites (non-bloom station) due to the aggregation during the dinoflagellate blooms. Therefore, estimated by sinking rates and carbon density shows that phytoplankton flux was the most importance contribution in bloom sites. Conversely, data from sediment trap show that fecal pellets sinking flux was higher than those of phytoplankton and other particles in the continental shelf of SCS. The phytoplankton POC flux in bloom sites (23952 was significantly higher than those in control sites (256 mg.C.m^-2.day^-1) in the ECS and in the SCS continental shelf (45 mg.C.m^-2.day^-1). These results reveal that community structure and ecological events (e.g. blooms) play a critical role of the POC export flux as well as carbon burial in the marginal sea.