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| Titel |
Regulation of anaerobic methane oxidation in sediments of the Black Sea |
| VerfasserIn |
N. J. Knab, B. A. Cragg, E. R. C. Hornibrook, L. Holmkvist, R. D. Pancost, C. Borowski, R. J. Parkes, B. B. Jørgensen |
| 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. 8 ; Nr. 6, no. 8 (2009-08-07), S.1505-1518 |
| Datensatznummer |
250003944
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| Publikation (Nr.) |
 copernicus.org/bg-6-1505-2009.pdf |
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| Zusammenfassung |
| Anaerobic oxidation of methane (AOM) and sulfate reduction (SRR) were
investigated in sediments of the western Black Sea, where upward methane
transport is controlled by diffusion. To understand the regulation and
dynamics of methane production and oxidation in the Black Sea, rates of
methanogenesis, AOM, and SRR were determined using radiotracers in
combination with pore water chemistry and stable isotopes. In the Danube
Canyon and the Dnjepr palaeo-delta AOM did not consume methane effectively
and upwards diffusing methane created an extended sulfate-methane transition
zone (SMTZ) that spread over more than 2.5 m and was located in brackish and
limnic sediment. Measurable AOM rates occurred mainly in the lower part of
the SMTZ, sometimes even at depths where sulfate seemed to be unavailable.
The inefficiency of methane oxidation appears to be linked to the
paleoceanographic history of the sediment, since in all cores methane was
completely oxidized at the transition from the formerly oxic brackish clays
to marine anoxic sediments. The upward tailing of methane was less
pronounced in a core from the deep sea in the area of the Dnjepr Canyon, the
only station with a SMTZ close to the marine deposits. Sub-surface sulfate
reduction rates were mostly extremely low, and in the SMTZ were even lower
than AOM rates. Rates of bicarbonate-based methanogenesis were below
detection limit in two of the cores, but δ13C values of methane
indicate a biogenic origin. The most δ13C- depleted isotopic
signal of methane was found in the SMTZ of the core from the deep sea, most
likely as a result of carbon recycling between AOM and methanogenesis. |
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