File:Comparison of zooplankton-mediated carbon cycles.jpg

English: Comparison of two zooplankton-mediated carbon cycles
The zooplankton-mediated carbon cycle in summer on the naturally iron-fertilized Kerguelen Plateau (a) compared to the high nutrient, low chlorophyll (HNLC) waters around the Southern Ocean Time Series (SOTS) site (b). On the Kerguelen Plateau, high iron levels lead to high chlorophyll a as a proxy for algae biomass at the surface. The diverse zooplankton community feeds on the sinking particle flux and acts as a “gate-keeper” to the deeper ocean by ingesting and fragmenting sinking particles and, consequently, significantly reducing the export flux out of the epipelagic. The main export particles are diatom resting spores, which bypass the intense grazing pressure, followed by fecal pellets. At SOTS, iron levels are lower and support a more diverse phytoplankton community, but with lower biomass, which, in turn, affects zooplankton community composition and biomass. The grazing pressure during summer is focused mostly on picoplankton, which leaves large particles for export. Grazing and fragmentation of particles at both sites increases nutrient recycling in the upper water column. Challenges and gaps in knowledge in aspects of the zooplankton-mediated carbon pump are highlighted.