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| Titel |
Effects of inorganic electron acceptors on methanogenesis and methanotrophy and on the community structure of bacteria and archaea in sediments of a boreal lake |
| VerfasserIn |
Antti J. Rissanen, Anu Karvinen, Hannu Nykänen, Sari Peura, Marja Tiirola, Anita Mäki, Paula Kankaala |
| 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 |
250124309
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| Publikation (Nr.) |
 EGU/EGU2016-3726.pdf |
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| Zusammenfassung |
| Lake sediments are globally significant sources of CH4 to the atmosphere, but the factors
controlling the production and consumption of CH4 in these systems are understudied.
Increasing availability of electron acceptors (EA) (other than CO2) in sediments can
decrease or even suppress CH4 production by diverting the electron flow (from H2 and
organic substances) from methanogenic to other anaerobic respiration pathways.
However, whether these changes in microbial function extend down to changes in the
structure of microbial communities is not known. Also anaerobic oxidation of methane
(AOM) could be enhanced by increased availability of EAs (SO42−, NO3−, Fe3+ and
Mn4+), but information on the role of this process in lake sediments is scarce.
We studied the effects of inorganic EAs on the potential for CH4 production and
consumption and on the structure of microbial communities in sediments of a boreal
lake.
Anoxic slurries of sediment samples collected from two depths (0 – 10 cm; 10 – 30 cm)
of the profundal zone of a boreal, mesotrophic Lake Ätäskö, were amended with 1) CH4 or
with CH4 and either 2) 10 mM Mn4+, 3) 10 mM Fe3+, 4) O2 or 5) CH2F2 (inhibitor of
aerobic methane oxidation) and incubated at +10˚ C for up to 4 months. Furthermore,
slurries from the 10 – 30 cm layer were amended with CH4 and either 6) 2 mM NO3− or 7) 2
mM SO42− and incubated at +4 ˚ C for up to 14 months. The processes were measured using
13C-labelling and by concentration measurements of CH4 and CO2. Effects of treatments 1-3
on microbial communities were also analysed by next-generation sequencing of
16S rRNA, as well as methyl coenzyme-M reductase gene amplicons and mRNA
transcripts.
CH4 production (max. 83 nmol gdw−1d−1) took place in the anaerobic treatments
but was generally decreased by the addition of NO3−, SO42−, Fe3+ and Mn4+.
Although the structure of sediment archaeal community was resistant to Fe3+/Mn4+ -
additions, slight changes in the structure of bacterial community occurred. Besides
decreasing the availability of methanogenic substrates, the Mn4+/Fe3+ - induced
changes in the bacterial community also probably decreased the H2:acetate – ratio in
the substrate pool. This led to increase in the relative activity (mRNA level) of
some operational taxonomic units assigned to aceticlastic Methanosaetaceae and
decrease in the relative activity of hydrogenotrophic Methanoregulaceae in the
sediment. CH4 oxidation (0.02 - 0.30 nmol gdw−1d−1 in anaerobic and 18 - 73 nmol
gdw−1d−1in aerobic treatments) took place without EA additions and was enhanced
only by O2. This suggests decoupling of the process from the reduction of other
inorganic EAs. The results also indicate that Fe3+/Mn4+ - reduction did not increase
CH4 oxidation via increased availability of SO42− by cryptic sulfur cycle or via
increased availability of organic EAs. Furthermore, ANME – archaea were only ≤ 3%
of sediment archaeal community and their relative activity was decreased during
incubations. Thus, EA driving CH4 oxidation in the anoxic sediments of the lake
remains unknown or the process was methanogen-driven via trace methane oxidation. |
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