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| Titel |
Temporal variability of carbon recycling in coastal sediments influenced by rivers: assessing the impact of flood inputs in the Rhône River prodelta |
| VerfasserIn |
C. Cathalot, C. Rabouille, L. Pastor, B. Deflandre, E. Viollier, R. Buscail, A. Grémare, C. Treignier, A. Pruski |
| 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 ; 7, no. 3 ; Nr. 7, no. 3 (2010-03-31), S.1187-1205 |
| Datensatznummer |
250004603
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| Publikation (Nr.) |
 copernicus.org/bg-7-1187-2010.pdf |
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| Zusammenfassung |
River deltas are particularly important in the marine carbon cycle as they
represent the transition between terrestrial and marine carbon: linked to
major burial zones, they are reprocessing zones where large carbon fluxes
can be mineralized. In order to estimate this mineralization, sediment
oxygen uptake rates were measured in continental shelf sediments and river
prodelta over different seasons near the outlet of the Rhône River in
the Mediterranean Sea. On a selected set of 10 stations in the river
prodelta and nearby continental shelf, in situ diffusive oxygen uptake (DOU)
and laboratory total oxygen uptake (TOU) measurements were performed in
early spring and summer 2007 and late spring and winter 2008. In and ex situ
DOU did not show any significant differences except for shallowest organic
rich stations. Sediment DOU rates show highest values concentrated close to
the river mouth (approx. 20 mmol O2 m−2 d−1) and decrease
offshore to values around 4.5 mmol O2 m−2 d−1 with lowest
gradients in a south west direction linked to the preferential transport of
the finest riverine material. Core incubation TOU showed the same spatial
pattern with an averaged TOU/DOU ratio of 1.2±0.4. Temporal
variations of sediment DOU over different sampling periods, spring summer
and late fall, were limited and benthic mineralization rates presented a
stable spatial pattern.
A flood of the Rhône River occurred in June 2008 and delivered up to
30 cm of new soft muddy deposit. Immediately after this flood, sediment DOU
rates close to the river mouth dropped from around 15–20 mmol O2 m−2 d−1
to values close to 10 mmol O2 m−2 d−1, in
response to the deposition near the river outlet of low reactivity organic
matter associated to fine material. Six months later, the oxygen
distribution had relaxed back to its initial stage: the initial spatial
distribution was found again underlining the active microbial degradation
rates involved and the role of further deposits. These results highlight the
immediate response of the sediment oxygen system to flood deposit and the
rapid relaxation of this system towards its initial state (6 months or less)
potentially linked to further deposits of reactive material. |
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