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| Titel |
Iron budgets for three distinct biogeochemical sites around the Kerguelen Archipelago (Southern Ocean) during the natural fertilisation study, KEOPS-2 |
| VerfasserIn |
A. R. Bowie, P. van der Merwe, F. Quéroué, T. Trull, M. Fourquez, F. Planchon, G. Sarthou, F. Chever, A. T. Townsend, I. Obernosterer, J.-B. Sallée, S. Blain |
| 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. 14 ; Nr. 12, no. 14 (2015-07-29), S.4421-4445 |
| Datensatznummer |
250118038
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| Publikation (Nr.) |
 copernicus.org/bg-12-4421-2015.pdf |
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| Zusammenfassung |
| Iron availability in the Southern Ocean controls phytoplankton growth,
community composition and the uptake of atmospheric CO2 by the
biological pump. The KEOPS-2 (KErguelen Ocean and Plateau compared Study 2)
"process study", took place around the Kerguelen Plateau in the Indian
sector of the Southern Ocean. This is a region naturally fertilised with iron
on the scale of hundreds to thousands of square kilometres, producing a
mosaic of spring blooms which show distinct biological and biogeochemical
responses to fertilisation. This paper presents biogeochemical iron budgets
(incorporating vertical and lateral supply, internal cycling, and sinks) for
three contrasting sites: an upstream high-nutrient low-chlorophyll reference,
over the plateau and in the offshore plume east of the Kerguelen Islands.
These budgets show that distinct regional environments driven by complex
circulation and transport pathways are responsible for differences in the
mode and strength of iron supply, with vertical supply dominant on the
plateau and lateral supply dominant in the plume. Iron supply from "new"
sources (diffusion, upwelling, entrainment, lateral advection, atmospheric
dust) to the surface waters of the plume was double that above the plateau
and 20 times greater than at the reference site, whilst iron demand (measured
by cellular uptake) in the plume was similar to that above the plateau but 40
times greater than at the reference site. "Recycled" iron supply by
bacterial regeneration and zooplankton grazing was a relatively minor
component at all sites (< 8 % of new supply), in contrast to earlier
findings from other biogeochemical iron budgets in the Southern Ocean. Over
the plateau, a particulate iron dissolution term of 2.5 % was invoked to
balance the budget; this approximately doubled the standing stock of
dissolved iron in the mixed layer. The exchange of iron between dissolved,
biogenic particulate and lithogenic particulate pools was highly dynamic in
time and space, resulting in a decoupling of the iron supply and carbon
export and, importantly, controlling the efficiency of fertilisation. |
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