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| Titel |
Deep silicon maxima in the stratified oligotrophic Mediterranean Sea |
| VerfasserIn |
Y. Crombet, K. Leblanc, B. Quéguiner, T. Moutin, P. Rimmelin, J. Ras, H. Claustre, N. Leblond, L. Oriol, M. Pujo-Pay |
| 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. 2 ; Nr. 8, no. 2 (2011-02-17), S.459-475 |
| Datensatznummer |
250005452
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| Publikation (Nr.) |
 copernicus.org/bg-8-459-2011.pdf |
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| Zusammenfassung |
| The silicon biogeochemical cycle has been studied in the Mediterranean Sea
during late summer/early autumn 1999 and summer 2008. The distribution of
nutrients, particulate carbon and silicon, fucoxanthin (Fuco), and total
chlorophyll-a (TChl-a) were investigated along an eastward gradient of
oligotrophy during two cruises (PROSOPE and BOUM) encompassing the entire
Mediterranean Sea during the stratified period. At both seasons, surface
waters were depleted in nutrients and the nutriclines gradually deepened
towards the East, the phosphacline being the deepest in the easternmost
Levantine basin. Following the nutriclines, parallel deep maxima of biogenic
silica (DSM), fucoxanthin (DFM) and TChl-a (DCM) were evidenced during both
seasons with maximal concentrations of 0.45 μmol L−1 for BSi,
0.26 μg L−1 for Fuco, and 1.70 μg L−1 for TChl-a, all measured during summer. Contrary to the DCM which was a persistent
feature in the Mediterranean Sea, the DSM and DFMs were observed in discrete
areas of the Alboran Sea, the Algero-Provencal basin, the Ionian sea and the
Levantine basin, indicating that diatoms were able to grow at depth and
dominate the DCM under specific conditions. Diatom assemblages were
dominated by Chaetoceros spp., Leptocylindrus spp.,
Pseudonitzschia spp. and the association between large centric
diatoms (Hemiaulus hauckii and Rhizosolenia styliformis)
and the cyanobacterium Richelia intracellularis was observed at nearly all sites.
The diatom's ability to grow at depth is commonly observed in other oligotrophic
regions and could play a major role in ecosystem productivity and carbon
export to depth. Contrary to the common view that Si and siliceous
phytoplankton are not major components of the Mediterranean biogeochemistry,
we suggest here that diatoms, by persisting at depth during the stratified
period, could contribute to a large part of the marine primary production as
observed in other oligotrophic areas. |
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