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| Titel |
Efficiency of the silicate pump at a coastal oligotrophic site in the Mediterranean Sea |
| VerfasserIn |
K. Leblanc, B. Quéguiner, P. Raimbault, N. Garcia |
| 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 ; 2, no. 3 ; Nr. 2, no. 3 (2005-08-29), S.219-229 |
| Datensatznummer |
250000620
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| Publikation (Nr.) |
 copernicus.org/bg-2-219-2005.pdf |
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| Zusammenfassung |
| A one-year survey of the sedimenting particulate material was conducted at
the SOFi site located on the edge of the continental slope in the Gulf of
Lions (Northwestern Mediterranean) between September 1999 and December 2000.
The main focus of this paper was to establish an annual budget of biogenic
silica export, to describe the seasonnal pattern of Si fluxes in relation to
the organic and mineral C fluxes and to quantify the Si/C decoupling
processes during sedimentation. The pattern of the downward flux of BSi was
partly typical with increased daily sedimentation rates during spring
followed by smaller peaks during summer. However, an unusual sedimentation
event was recorded in the bottom trap in February before the spring thermal
stratification occurred, and represented 37% of the annual BSi mass
flux. The total annual BSi flux at the SOFi site was estimated from the
bottom trap and amounted to 86.8 mmol Si m-2 y-1, while the
organic carbon flux amounted to 154.9 mmol C m-2 y-1. The overall
efficiency of C export to depth compared to surface primary production
budgets was low (3%) and similar to values found for oligotrophic
regions of the Eastern Mediterranean. On the other hand, we documented a
very high efficiency of the Si export at the SOFi site, with 62% of the
Si produced in the surface layer exported to the bottom trap. The excellent
correlation between BSi and particulate organic C (POC) in the bottom trap
further indicates that the bulk of the organic matter is transferred to
depth in association with diatoms. However, the main fraction of the C
produced by phytoplankton is lost in the water column through oxidation or
metabolisation, while biogenic silica is more efficiently transferred to
depth. This strong Si/C decoupling with depth is likely to be the cause of
the spring depletion of silicic acid over the entire water column which was
observed by mid-April in a companion study (Leblanc et al., 2003) and may
cause a severe Si limitation of the diatom spring bloom in this oligotrophic
region of the Gulf of Lions. |
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