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Biogeosciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/bg-2017-414
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
10 Oct 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).
The role of diatom resting spores for pelagic-benthic coupling in the Southern Ocean
Mathieu Rembauville1, Stéphane Blain1, Clara Manno3, Geraint Tarling3, Anu Thompson4, George Wolff4, and Ian Salter1,2 1Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire d'Océanographie Microbienne (LOMIC), Observatoire Océanologique, 66650, Banyuls/mer, France
2Alfred-Wegener-Institute for Polar and Marine research, Bremerhaven, Germany
3British Antarctic Survey, Natural Environmental Research Council, High Cross, Madingley Road, Cambridge, CB3 0ET, UK
4School of Environmental Sciences, 4 Brownlow Street, University of Liverpool, Liverpool, L69 3GP, UK
Abstract. Natural iron fertilization downstream of Southern Ocean island plateaus support large phytoplankton blooms and promote carbon export from the mixed layer. In addition to sequestering atmospheric CO2, the biological carbon pump also supplies organic matter (OM) to deep-ocean ecosystems. Although the total flux of OM arriving at the seafloor sets the energy input to the system, the chemical nature of OM is also of significance. However, a quantitative framework linking ecological flux vectors to OM composition is currently lacking. In the present study we report the lipid composition of export fluxes collected by five-moored sediment traps deployed in contrasting productivity regimes of Southern Ocean island systems (Kerguelen, Crozet and South Georgia) and compile them with quantitative data on diatom and fecal pellet fluxes. At the three naturally iron fertilized sites, the relative contribution of labile lipids (mono- and polyunsaturated fatty acids, unsaturated fatty alcohols) is 2–4 times higher than at low productivity sites. There is a strong attenuation of labile components as a function of depth, irrespective of productivity. The three island systems also display regional characteristics in lipid export. The diversity of sterols is greater in the relatively warm waters of the Polar Frontal Zone when compared to the Antarctic zone, reflecting the transition from mixed phytoplankton communities to principally diatom-derived OM. An enrichment of zooplankton dietary sterols, such as C27Δ5, at South Georgia is consistent with high zooplankton and krill biomass in the region and the importance of fecal pellets to POC flux. There is a strong association of diatom resting spore fluxes that dominate productive flux regimes with energy rich unsaturated fatty acids. At the Kerguelen Plateau we provide a statistical framework to link seasonal variation in ecological flux vectors and lipid composition over a complete annual cycle. Our analyses demonstrate that ecological processes in the upper ocean, e.g. resting spore formation and grazing, not only impact the magnitude and stoichiometry of the Southern Ocean biological pump, but also regulate the composition of exported OM and the nature of pelagic-benthic coupling.

Citation: Rembauville, M., Blain, S., Manno, C., Tarling, G., Thompson, A., Wolff, G., and Salter, I.: The role of diatom resting spores for pelagic-benthic coupling in the Southern Ocean, Biogeosciences Discuss., https://doi.org/10.5194/bg-2017-414, in review, 2017.
Mathieu Rembauville et al.
Mathieu Rembauville et al.
Mathieu Rembauville et al.

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Short summary
Sinking phytoplankton from the surface ocean provide the principal energy source to deep-ocean ecosystems. Our aim was to understand how different phytoplankton communities impact the chemical nature of this sinking material. We show certain types of phytoplankton can preferentially export energy-rich storage compounds to the seafloor. Any climate-driven effects on phytoplankton community structure could thus impact remote deep-ocean ecosystems thousands of kilometres beneath the surface.
Sinking phytoplankton from the surface ocean provide the principal energy source to deep-ocean...
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