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| Titel |
Vertical distribution of methane oxidation and methanotrophic response to elevated methane concentrations in stratified waters of the Arctic fjord Storfjorden (Svalbard, Norway) |
| VerfasserIn |
S. Mau, J. Blees, E. Helmke, H. Niemann, E. Damm |
| 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 ; 10, no. 10 ; Nr. 10, no. 10 (2013-10-07), S.6267-6278 |
| Datensatznummer |
250085349
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| Publikation (Nr.) |
 copernicus.org/bg-10-6267-2013.pdf |
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| Zusammenfassung |
| The bacterially mediated aerobic methane oxidation (MOx) is a key
mechanism in controlling methane (CH4) emissions from the world's oceans
to the atmosphere. In this study, we investigated MOx in the
Arctic fjord Storfjorden (Svalbard) by applying a combination of
radio-tracer-based incubation assays (3H-CH4 and
14C-CH4), stable C-CH4 isotope measurements, and molecular
tools (16S rRNA gene Denaturing Gradient Gel Electrophoresis (DGGE)
fingerprinting, pmoA- and mxaF gene analyses). Storfjorden
is stratified in the summertime with melt water (MW) in the upper 60 m of
the water column, Arctic water (ArW) between 60 and 100 m, and
brine-enriched shelf water (BSW) down to 140 m. CH4 concentrations were
supersaturated with respect to the atmospheric equilibrium (about 3–4 nM)
throughout the water column, increasing from ∼20 nM at the surface to
a maximum of 72 nM at 60 m and decreasing below. MOx rate
measurements at near in situ CH4 concentrations (here measured with
3H-CH4 raising the ambient CH4 pool by <2 nM) showed a
similar trend: low rates at the sea surface, increasing to a maximum of
∼2.3 nM day−1 at 60 m, followed by a decrease in the deeper
ArW/BSW. In contrast, rate measurements with 14C-CH4 (incubations
were spiked with ∼450 nM of 14C-CH4, providing an estimate
of the CH4 oxidation at elevated concentration) showed comparably low
turnover rates (<1 nM day−1) at 60 m, and peak rates were found
in ArW/BSW at ∼100 m water depth, concomitant with increasing
13C values in the residual CH4 pool. Our results indicate that the
MOx community in the surface MW is adapted to relatively low
CH4 concentrations. In contrast, the activity of the deep-water
MOx community is relatively low at the ambient, summertime
CH4 concentrations but has the potential to increase rapidly in response
to CH4 availability. A similar distinction between surface and
deep-water MOx is also suggested by our molecular analyses. The
DGGE banding patterns of 16S rRNA gene fragments of the surface MW and deep
water were clearly different. A DGGE band related to the known type I
MOx bacterium Methylosphaera was observed in deep BWS,
but absent in surface MW. Furthermore, the Polymerase Chain Reaction (PCR)
amplicons of the deep water with the two functional primers sets
pmoA and mxaF showed, in contrast to those of the surface
MW, additional products besides the expected one of 530 base pairs (bp).
Apparently, different MOx communities have developed in the
stratified water masses in Storfjorden, which is possibly related to the
spatiotemporal variability in CH4 supply to the distinct water masses. |
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