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| Titel |
Early-diagenetic processes in marine mangrove sediments from Guadeloupe, French West Indies |
| VerfasserIn |
Antoine Crémière, Mathieu Sebilo, Harald Strauss, Olivier Gros, Anniet M. Laverman |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250097960
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| Publikation (Nr.) |
 EGU/EGU2014-13590.pdf |
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| Zusammenfassung |
| Sediment and pore-water geochemistry were investigated in two short sediment cores from
the Manche-à-eau lagoon (Guadeloupe, French Caribbean island) surrounded by mangroves
trees. These sediments present high total organic carbon content, ranging between 10 to 18 %
wt, mainly originating from mangrove litter fall. Oxygen is depleted in the first few
millimetres of the sediment indicating active organic carbon degradation. Seawater sulphate
is entirely consumed within the first 20 cm of the sediments and total organic carbon content
decreases with depth pointing out that early-diagenetic degradation of organic matter occurs
with sulphate reduction. Sulphide produced as the results of sulphate reduction partly reacts
with detrital iron-bearing minerals and precipitates as pyrite which is consistent with high
amounts of sulphur in the sediments (4-5 % wt). The sulphur isotopic composition
(δ34S) of both dissolved sulphate and sulphide in pore-water increases with depth
displaying a large apparent isotopic fractionation (Δ34S) between both species of
65-80oas a result of bacterial sulphate reduction. Scanning electron microscopy
investigation reveals that a part of the carbonate alkalinity produced either by organic
matter oxidation or anaerobic methane oxidation leads to authigenic carbonates
precipitation. These results provide straightforward evidence that carbon and sulphur
biogeochemical cycles are intimately governed by sedimentary microbial activity. |
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