 |
| Titel |
Methane emission and consumption at a North Sea gas seep (Tommeliten area) |
| VerfasserIn |
H. Niemann, M. Elvert, M. Hovland, B. Orcutt, A. Judd, I. Suck, J. Gutt, S. Joye, E. Damm, K. Finster, A. Boetius  |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 2, no. 4 ; Nr. 2, no. 4 (2005-11-24), S.335-351 |
| Datensatznummer |
250000635
|
| Publikation (Nr.) |
 copernicus.org/bg-2-335-2005.pdf |
|
|
|
|
|
| Zusammenfassung |
| The Tommeliten seepage area is part of the Greater Ekofisk area, which is
situated above the Tommeliten Delta salt diapir in the central North Sea
(56°29.90' N, 2°59.80' E, Norwegian Block 1/9, 75 m water depth).
Here, cracks in a buried marl horizon allow methane to migrate into
overlying clay-silt and sandy sediments. Hydroacoustic sediment echosounding
showed several venting spots coinciding with the apex of marl domes where
methane is released into the water column and potentially to the atmosphere.
In the vicinity of the gas seeps, sea floor observations showed small mats
of giant sulphide-oxidizing bacteria above patches of black sediments as
well as carbonate crusts, which are exposed 10 to 50 cm above seafloor
forming small reefs. These Methane-Derived Authigenic Carbonates (MDACs)
contain 13C-depleted, archaeal lipids indicating previous gas seepage
and AOM activity. High amounts of sn2-hydroxyarchaeol relative to archaeol and
low abundances of biphytanes in the crusts give evidence that ANaerobic
MEthane-oxidising archaea (ANME) of the phylogenetic cluster ANME-2 were the
potential mediators of Anaerobic Oxidation of Methane (AOM) at the time of
carbonate formation. Small pieces of MDACs were also found subsurface at
about 1.7 m sediment depth, associated with the AOM zone. This zone is
characterized by elevated AOM and Sulphate Reduction (SR) rates, increased
concentrations of 13C-depleted tetraether derived biphytanes, and
specific bacterial Fatty Acids (FA). Further biomarker and 16S rDNA based
analyses of this horizon give evidence that AOM is mediated by archaea
belonging to the ANME-1b group and Sulphate Reducing Bacteria (SRB) most
likely belonging to the Seep-SRB1 cluster. The zone of active methane
consumption was restricted to a distinct horizon of about 20 cm.
Concentrations of 13C-depleted lipid biomarkers (e.g. 500 ng g-dw−1
biphythanes, 140 ng g-dw−1 fatty acid ai-C15:0), cell
numbers (1.5×108 cells cm−3), AOM and SR rates (3 nmol cm−3 d−1)
in the Tommeliten AOM zone are 2–3 orders of magnitude lower
compared to AOM zones of highly active deep water cold seeps such as Hydrate
Ridge or the Gulf of Mexico. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|