The biological pump efficiency is set by the different processes controlling formation and export of biogenic material from the surface layer and also the processes consuming organic C deeper in the mesopelagic. We applied different proxy-approaches to evaluate the potential for C export (new production), C export production from the surface (234Th deficit) and remineralization of organic C at greater, mesopelagic depths (BaSO4 accumulation, bacterial activity) for different functional entities of the Southern Ocean. These include SAZ and PFZ systems differing in planktonic composition and functioning, as well as shelf and margin systems naturally supplied with Fe, studied during S.O. expeditions including KEOPS/2005 and SAZ-SENSE/2007. Production, export and mesopelagic remineralization rates are compared between these different provinces to investigate spatial variability of C sequestration efficiency. Our findings about efficiency of C export and remineralization highlight the importance of: -type of phytoplankton dominance, with diatoms dominated systems leading to shallower remineralization; -phytoplankton biomass and grazing, with evidence for relatively less mesopelagic remineralization under conditions of high biomass and high grazing pressure; -the important control of prokaryotes on organic carbon remineralization length scales; - the possible impact of Fe availability.
|AGU Chapman Conference on the Biological Carbon Pump of the Oceans Brockenhurst, Hampshire, England 1–4 September 2009
|Published - 2009