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| Titel |
Biogeochemical processes and microbial diversity of the Gullfaks and Tommeliten methane seeps (Northern North Sea) |
| VerfasserIn |
G. Wegener, M. Shovitri, K. Knittel, H. Niemann, M. Hovland, A. Boetius  |
| 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 ; 5, no. 4 ; Nr. 5, no. 4 (2008-08-18), S.1127-1144 |
| Datensatznummer |
250002683
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| Publikation (Nr.) |
 copernicus.org/bg-5-1127-2008.pdf |
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| Zusammenfassung |
| Fluid flow related seafloor structures and gas seeps were detected in the
North Sea in the 1970s and 1980s by acoustic sub-bottom profiling and oil
rig surveys. A variety of features like pockmarks, gas vents and authigenic
carbonate cements were found to be associated with sites of oil and gas
exploration, indicating a link between these surface structures and the
underlying, deep hydrocarbon reservoirs. In this study we performed acoustic
surveys and videographic observation at Gullfaks, Holene Trench, Tommeliten,
Witch's Hole and the giant pockmarks of the UK Block 15/25, to investigate
the occurrence and distribution of cold seep ecosystems in the Northern
North Sea. The most active gas seep sites, i.e. Gullfaks and Tommeliten,
were investigated in detail. At both sites, gas bubbles escaped continuously
from small holes in the seabed to the water column, reaching the upper mixed
surface layer. At Gullfaks a gas emitting, flat area of 0.1 km2 of
sandy seabed covered by filamentous sulfur-oxidizing bacteria was detected.
At Tommeliten, we found a patchy distribution of small bacterial mats
indicating sites of gas seepage. Below the patches the seafloor consisted of
sand from which gas emissions were observed. At both sites, the anaerobic
oxidation of methane (AOM) coupled to sulfate reduction (SR) was the major
source of sulfide. Molecular analyses targeting specific lipid biomarkers
and 16S rRNA gene sequences identified an active microbial community
dominated by sulfur-oxidizing and sulfate-reducing bacteria (SRB) as well
as methanotrophic bacteria and archaea. Stable carbon isotope values of
specific, microbial fatty acids and alcohols from both sites were highly
depleted in the heavy isotope 13C, indicating that the microbial
community incorporates methane or its metabolites. The microbial community
composition of both shallow seeps shows high similarities to the deep water
seeps associated with gas hydrates such as Hydrate Ridge or the Eel River
basin. |
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