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| Titel |
Export fluxes in a naturally iron-fertilized area of the Southern Ocean – Part 2: Importance of diatom resting spores and faecal pellets for export |
| VerfasserIn |
M. Rembauville, S. Blain, L. Armand, B. Quéguiner, I. Salter |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 11 ; Nr. 12, no. 11 (2015-06-02), S.3171-3195 |
| Datensatznummer |
250117956
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| Publikation (Nr.) |
 copernicus.org/bg-12-3171-2015.pdf |
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| Zusammenfassung |
| The biological composition of the material exported to a moored sediment
trap located under the winter mixed layer of the naturally fertilized
Kerguelen Plateau in the Southern Ocean was studied over an annual cycle.
Despite iron availability in spring, the annual particulate organic carbon
(POC) export (98.2 mmol m−2) at 289 m was low, but annual biogenic
silica export was significant (114 mmol m−2). This feature was related
to the abundance of empty diatom cells and the ratio of full to empty cells
exerted a first-order control in BSi : POC export stoichiometry of the
biological pump. Chaetoceros Hyalochaete spp. and Thalassiosira antarctica
resting spores were responsible for more than 60% of the annual POC flux that occurred during two very short export
events of < 14 days in spring–summer. Relatively low diatom fluxes
were observed over the remainder of the year. Faecal pellet contribution to
annual carbon flux was lower (34%) and reached its seasonal maximum in
autumn and winter (> 80%). The seasonal progression of faecal
pellet types revealed a clear transition from small spherical shapes (small
copepods) in spring, to larger cylindrical and ellipsoid shapes in summer
(euphausiids and large copepods) and finally to large tabular shapes (salps) in
autumn and winter. We propose in this high-biomass, low-export (HBLE)
environment that small but highly silicified and fast-sinking resting
spores are able to bypass the intense grazing pressure and efficient carbon
transfer to higher trophic levels that are responsible for the low fluxes
observed the during the remainder of the year. More generally our study also
provides a statistical framework linking the ecological succession of diatom
and zooplankton communities to the seasonality of carbon and silicon export
within an iron-fertilized bloom region in the Southern Ocean. |
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