We are presenting a poster entitled "Influence of blooms of calcifying phytoplankton on carbon transfer in the mesopelagic ocean" (Griet Neukermans, Nathan Briggs, Louis Terrats, and Hervé Claustre).
Abstract: The gravitational sinking of biogenic carbon particles in the ocean are an essential component of the ocean carbon cycle. Biogenic carbon particles are generated by phytoplankton in the sunlit surface ocean and comprise Particulate Organic and Inorganic Carbon (POC and PIC). Here we compare and contrast the downward transfer of carbon particles associated with blooms of calcifying and non-calcifying phytoplankton, corresponding to high PIC and high POC concentrations, respectively. We merged ocean colour satellite observations of POC and PIC in the near-surface ocean with water column observations of sinking particles obtained from BioGeoChemical-Argo floats (BGC-Argo) operating in the productive North and South Atlantic Ocean. Our results indicate that calcifying phytoplankton blooms had a pronounced impact on the downward transfer of sinking particles compared to blooms of non-calcifying phytoplankton in both regions. In the South Atlantic where floats operated at high temporal resolution, we show that particles associated with a calcifying phytoplankton bloom sank twice as fast. In the North Atlantic, where floats operated at lower temporal resolution, the transfer of particles was deeper and more efficient than for blooms of non-calcifying phytoplankton whose particle flux was strongly attenuated in the upper mesopelagic ocean.