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| Titel |
Distributions and stoichiometry of dissolved nitrogen and phosphorus in the iron-fertilized region near Kerguelen (Southern Ocean) |
| VerfasserIn |
S. Blain, J. Capparos, A. Guéneugues, I. Obernosterer, L. Oriol |
| 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. 2 ; Nr. 12, no. 2 (2015-01-30), S.623-635 |
| Datensatznummer |
250117794
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| Publikation (Nr.) |
 copernicus.org/bg-12-623-2015.pdf |
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| Zusammenfassung |
| During KEOPS2 (Kerguelen Ocean and Plateau Compared Study 2), we determined
dissolved inorganic and organic nitrogen and phosphorus species in the
naturally fertilized region of Kerguelen Island (Southern Ocean). Above
150 m, stations were clearly separated by the polar front (PF), with
concentrations of NO3-, NO2- and PO43- overall lower
north of the PF than south. Though less pronounced, a similar trend was
detectable for dissolved organic nitrogen (DON) and dissolved organic
phosphorus (DOP). At all stations offshore and above the plateau, a
subsurface maximum of NH4+ was observed between 50 and 150 m. We
examined nutrient stoichiometry by calculating the linear combination
N* = [NO3-]-16 [PO43-]. The majority of stations and
depths revealed N* close to −3 μM; however, for surface waters
north of the PF, N* increased up to 6 μM. This suggests a
preferential uptake of PO43- versus NO3- by fast-growing
diatoms. Using the tracer TNxs = [TDN]-16[TDP] (TDN, total
dissolved nitrogen; TDP, total dissolved phosphorus) revealed that the
dissolved organic fraction significantly contributed to changes in
TNxs. TNxs values were negative for most stations and
depths, and relatively constant in the 0–500 m layer. As for N*, the
stations north of the PF had higher TNxs in the 0–100 m layer.
We discuss this stoichiometric anomaly with respect to possible external
sources and sinks of N and P. Additional data collected in February 2013 at
two sites revealed the occurrence of a subsurface minimum of N* located
just below the pycnocline, which denotes a layer where remineralization of
particulate organic matter with low N : P ratio P, possibly associated with
preferential remineralization of P versus N, persists throughout the season. |
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