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| Titel |
Carbon mineralization and carbonate preservation in modern cold-water coral reef sediments on the Norwegian shelf |
| VerfasserIn |
L. M. Wehrmann, N. J. Knab, H. Pirlet, V. Unnithan, C. Wild, T. G. Ferdelman |
| 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 ; 6, no. 4 ; Nr. 6, no. 4 (2009-04-27), S.663-680 |
| Datensatznummer |
250003646
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| Publikation (Nr.) |
 copernicus.org/bg-6-663-2009.pdf |
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| Zusammenfassung |
| Cold-water coral ecosystems are considered hot-spots of biodiversity and
biomass production and may be a regionally important contributor to carbonate
production. The impact of these ecosystems on biogeochemical processes and
carbonate preservation in associated sediments were studied at Røst Reef
and Traenadjupet Reef, two modern (post-glacial) cold-water coral reefs on
the Mid-Norwegian shelf. Sulfate and iron reduction as well as carbonate
dissolution and precipitation were investigated by combining pore-water
geochemical profiles, steady state modeling, as well as solid phase analyses
and sulfate reduction rate measurements on gravity cores of up to 3.25 m
length. Low extents of sulfate depletion and dissolved inorganic carbon (DIC)
production, combined with sulfate reduction rates not exceeding
3 nmol S cm−3 d−1, suggested that overall anaerobic carbon
mineralization in the sediments was low. These data showed that the coral
fragment-bearing siliciclastic sediments were effectively decoupled from the
productive pelagic ecosystem by the complex reef surface framework. Organic
matter being mineralized by sulfate reduction was calculated to consist of
57% carbon bound in CH2O groups and 43% carbon in -CH2- groups.
Methane concentrations were below 1 μM, and failed to support the
hypothesis of a linkage between the distribution of cold-water coral reefs
and the presence of hydrocarbon seepage. Reductive iron oxide dissolution
linked to microbial sulfate reduction buffered the pore-water carbonate
system and inhibited acid-driven coral skeleton dissolution. A large pool of
reactive iron was available leading to the formation of iron sulfide
minerals. Constant pore-water Ca2+, Mg2+ and Sr2+
concentrations in most cores and decreasing Ca2+ and Sr2+
concentrations with depth in core 23–18 GC indicated diagenetic carbonate
precipitation. This was consistent with the excellent preservation of buried
coral fragments. |
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