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| Titel |
Integrated survey of elemental stoichiometry (C, N, P) from the western to eastern Mediterranean Sea |
| VerfasserIn |
M. Pujo-Pay, P. Conan, L. Oriol, V. Cornet-Barthaux, C. Falco, J.-F. Ghiglione, C. Goyet, T. Moutin, L. Prieur |
| 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 ; 8, no. 4 ; Nr. 8, no. 4 (2011-04-08), S.883-899 |
| Datensatznummer |
250005690
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| Publikation (Nr.) |
 copernicus.org/bg-8-883-2011.pdf |
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| Zusammenfassung |
| This paper provides an extensive vertical and longitudinal description of
the biogeochemistry along an East-West transect of 3000 km across the
Mediterranean Sea during summer 2008 (BOUM cruise). During this period of
strong stratification, the distribution of nutrients, particulate and
dissolved organic carbon (DOC), nitrogen (DON) and phosphorus (DOP) were
examined to produce a detailed spatial and vertically extended description
of the elemental stoichiometry of the Mediterranean Sea. Surface waters were
depleted in nutrients and the thickness of this depleted layer increased
towards the East from about 10 m in the Gulf of Lion to more than 100 m in
the Levantine basin, with the phosphacline deepening to a greater extent
than that for corresponding nitracline and thermocline depths. We used the
minimum oxygen concentration through the water column in combination with 2
fixed concentrations of dissolved oxygen to distinguish an intermediate
layer (Mineralization Layer; ML) from surface (Biogenic Layer; BL), and deep
layers (DL). Whilst each layer was represented by different water masses,
this approach allowed us to propose a schematic box-plot representation of
the biogeochemical functioning of the two Mediterranean basins. Despite the
increasing oligotrophic nature and the degree of P-depletion along the West
to East gradient strong similarities were encountered between eastern and
western ecosystems. Within the BL, the C:N:P ratios in all pools largely
exceeded the Redfield ratios, but surprisingly, the nitrate vs. phosphate
ratios in the ML and DL tended towards the canonical Redfield values in both
basins. A change in particulate matter composition has been identified by a
C increase relative to N and P along the whole water column in the western
basin and between BL and ML in the eastern one. Our data showed a noticeable
stability of the DOC:DON ratio (12–13) throughout the Mediterranean Sea.
This is in good agreement with a P-limitation of microbial activities but in
contradiction of the accepted concept that N is recycled faster than C. The
western and eastern basins had similar or close biological functioning.
Differences come from variability in the allochtonous nutrient sources in
terms of quantity and quality, and to the specific hydrodynamic features of
the Mediterranean basins. |
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