Gelatinous zooplankton-mediated carbon flows in the global oceans: A data-driven modeling study

Abstract

Among marine organisms, gelatinous zooplankton (GZ; cnidarians, ctenophores, and pelagic tunicates) are unique in their energetic efficiency, as the gelatinous body plan allows them to process and assimilate high proportions of oceanic carbon. Upon death, their body shape facilitates rapid sinking through the water column, resulting in carcass depositions on the seafloor (“jelly-falls”). GZ are thought to be important components of the biological pump, but their overall contribution to global carbon fluxes remains unknown. Using a data-driven, 3-dimensional, carbon-cycle model resolved to a 1° global grid, with a Monte Carlo uncertainty analysis, we estimate that GZ consumed 7.9-13 Pg C y-1 in phytoplankton and zooplankton, resulting in a net production of 3.9-5.8 Pg C y-1 in the upper ocean (top 200 m), with the largest fluxes from pelagic tunicates. Non-predation mortality (carcasses) comprised 25% of GZ-production, and combined with the much greater fecal matter flux, total GZ particulate organic carbon (POC) export at 100 m was 1.6-5.2 Pg C y-1, equivalent to 32-40% of the global POC export. The fast sinking GZ export resulted in a high transfer efficiency (Teff) of 38-62% to 1000 m, and 25-40% to the seafloor. Finally, jelly-falls at depths > 50 m are likely unaccounted for in current POC flux estimates and could increase benthic POC flux by 8-35%. The significant magnitude of and distinct sinking properties of GZ fluxes support a critical yet under-recognized role of GZ carcasses and fecal matter to the biological pump and air-sea carbon balance.