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Modelling the silica pump in the Permanently Open Ocean Zone of the Southern Ocean
Pondaven, P.; Fravalo, C.; Ruiz Pino, D.; Tréguer, P.; Quéguiner, B.; Jeandel, C. (1998). Modelling the silica pump in the Permanently Open Ocean Zone of the Southern Ocean, in: Le Fèvre, J. et al. (Ed.) Carbon Fluxes and Dynamic Processes in the Southern Ocean: Present and Past. Selected papers from the International JGOFS Symposium, Brest, France, 28-31 August 1995. Journal of Marine Systems, 17(1-4): pp. 587-619. hdl.handle.net/10.1016/S0924-7963(98)00066-9
In: Le Fèvre, J.; Tréguer, P. (Ed.) (1998). Carbon Fluxes and Dynamic Processes in the Southern Ocean: Present and Past. Selected papers from the International JGOFS Symposium, Brest, France, 28-31 August 1995. Journal of Marine Systems, 17(1-4). Elsevier: Amsterdam. 1-619 pp., more
In: Journal of Marine Systems. Elsevier: Tokyo; Oxford; New York; Amsterdam. ISSN 0924-7963, more
Peer reviewed article  

Also published as
  • Pondaven, P.; Fravalo, C.; Ruiz Pino, D.; Tréguer, P.; Quéguiner, B.; Jeandel, C. (1998). Modelling the silica pump in the Permanently Open Ocean Zone of the Southern Ocean. J. Mar. Syst. 17(1-4): 587-619. hdl.handle.net/10.1016/S0924-7963(98)00066-9, more

Available in Authors 

Keywords
    Biogeochemical cycle; Chemical oceanography; Microorganisms; Modelling; Nannoplankton; Nitrogen cycle; Nutrient cycles; Pelagic environment; Physical oceanography; Phytoplankton; Primary production; Pumps; Silicon cycle; Simulation; Zooplankton; PSE, Antarctic Ocean [Marine Regions]; PSE, South Indian Ocean [Marine Regions]; Marine

Authors  Top 
  • Pondaven, P.
  • Fravalo, C.
  • Ruiz Pino, D.
  • Tréguer, P., more
  • Quéguiner, B.
  • Jeandel, C.

Abstract
    A coupled 1D physical–biogeochemical model has been built to simulate the cycles of silicon and of nitrogen in the Indian sector of the Permanently Open Ocean Zone of the Southern Ocean. Based on a simplified trophic network, that includes two size classes of phytoplankton and of zooplankton, and a microbial loop, it has been calibrated by reference to surface physical, chemical and biological data sets collected at the KERFIX time-series station (50°40'S–68°25'E). The model correctly reproduces the high nutrient low chlorophyll features typical of the studied area. In a region where the spring–summer mixed layer depth is usually deeper than 60 m, the maximum of chlorophyll never exceeds 1.5 mg m-3, and the annual primary production is only 68 g C m-2 year-1. In the surface layer nitrate is never exhausted (range 27–23.5 mmoles m-3) while silicic acid shows strong seasonal variations (range 5–20 mmoles m-3). On an annual basis 71% of the primary production sustained by nanophytoplankton is grazed by microzooplankton. Compared to North Atlantic, siliceous microphytoplankton is mainly prevented from blooming because of an unfavourable spring–summer light-mixing regime. Silicic acid limitation (high half saturation constant for Si uptake: 8 mmoles m-3) also plays a major role on diatom growth. Mesozooplankton grazing pressure excerpts its influence especially in late spring. The model illustrates the efficiency of the silica pump in the Southern Ocean: up to 63% of the biogenic silica that has been synthetized in the photic layer is exported towards the deep ocean, while only 11% of the particulate organic nitrogen escapes recycling in the surface layer.

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