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| Titel |
Microbial Methane Oxidation Rates in Guandu Wetland of northern Taiwan |
| VerfasserIn |
Zih-Huei Yu, Pei-Ling Wang, Li-Hung Lin |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250126774
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| Publikation (Nr.) |
 EGU/EGU2016-6549.pdf |
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| Zusammenfassung |
| Wetland is one of the major sources of atmospheric methane. The exact magnitude
of methane emission is essentially controlled by microbial processes. Besides of
methanogenesis, methanotrophy oxidizes methane with the reduction of various electron
acceptors under oxic or anoxic conditions. The interplay of these microbial activities
determines the final methane flux under different circumstances. In a tidal wetland, the cyclic
flooding and recession of tide render oxygen and sulfate the dominant electron acceptors for
methane oxidation. However, the details have not been fully examined, especially for the
linkage between potential methane oxidation rates and in situ condition. In this study, a
sub-tropical wetland in northern Taiwan, Guandu, was chosen to examine the tidal effect
on microbial methane regulation. Several sediment cores were retrieved during
high tide and low tide period and their geochemical profiles were characterized to
demonstrate in situ microbial activities. Incubation experiments were conducted to
estimate potential aerobic and anaerobic methane oxidation rates in surface and core
sediments.
Sediment cores collected in high tide and low tide period showed different geochemical
characteristics, owning to tidal inundation. Chloride and sulfate concentration were lower
during low tide period. A spike of enhanced sulfate at middle depth intervals was sandwiched
by two sulfate depleted zones above and underneath. Methane was accumulated significantly
with two methane depletion zones nearly mirroring the sulfate spike zone identified. During
the high tide period, sulfate decreased slightly with depth with methane production inhibited
at shallow depths. However, a methane consumption zone still occurred near the surface.
Potential aerobic methane oxidation rates were estimated between 0.7 to 1.1 μmole/g/d,
showing no difference between the samples collected at high tide or low tide period.
However, a lag phase was widely observed and the lag phase lasted over a longer period of
time for the samples collected in high tide period. It seems that aerobic methanotrophs
needed a longer period of time to recovery and/or had low activities, since they
had been suppressed by low oxygen concentration during high tide period. The
rates of anaerobic methane oxidation ranged between 1.5 and 4.0 nmole/g/d for
samples collected at high tide period, whereas lower rates ranging from 0.2 to 2.0
nmole/g/d were observed for samples at low tide period. The addition of basal salt
solution apparently stimulated methane consumption significantly. Based on the field
observation and laboratory incubations, our results indicated a dynamic shift of metabolic
zonation in tidally influenced wetlands. Aerobic methanotrophy appears to outpace
anaerobic methanotrophy by orders of magnitude regardless of tidal inundation. This
together with methanogenesis regulated by the availability of sulfate and organic
degradation plays a major role in controlling methane emission. While anaerobic
methanotrophy is relatively minor in methane cycling, its linkage with the sulfate availability
modulates the coupling of carbon and sulfur turnover under anoxic conditions. |
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