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| Titel |
Stable carbon isotope discrimination and microbiology of methane formation in tropical anoxic lake sediments |
| VerfasserIn |
R. Conrad, M. Noll, P. Claus, M. Klose, W. R. Bastos, A. Enrich-Prast |
| 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 ; 8, no. 3 ; Nr. 8, no. 3 (2011-03-25), S.795-814 |
| Datensatznummer |
250005579
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| Publikation (Nr.) |
 copernicus.org/bg-8-795-2011.pdf |
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| Zusammenfassung |
| Methane is an important end product of degradation of organic matter in
anoxic lake sediments. Methane is mainly produced by either reduction of
CO2 or cleavage of acetate involving different methanogenic archaea.
The contribution of the different methanogenic paths and of the diverse
bacteria and archaea involved in CH4 production exhibits a large
variability that is not well understood. Lakes in tropical areas, e.g. in
Brazil, are wetlands with high potential impact on the global CH4
budget. However, they have hardly been studied with respect to
methanogenesis. Therefore, we used samples from 16 different lake sediments
in the Pantanal and Amazon region of Brazil to measure production of
CH4, CO2, analyze the content of 13C in the products and in
intermediately formed acetate, determine the abundance of bacterial and
archaeal microorgansisms and their community composition and diversity by
targeting the genes of bacterial and archaeal ribosomal RNA and of methyl
coenzyme M reductase, the key enzyme of methanogenic archaea. These
experiments were done in the presence and absence of methyl fluoride, an
inhibitor of acetoclastic methanogenesis. While production rates of CH4
and CO2 were correlated to the content of organic matter and the
abundance of archaea in the sediment, values of 13C in acetate,
CO2, and CH4 were related to the 13C content of organic
matter and to the path of CH4 production with its intrinsic carbon
isotope fractionation. Isotope fractionation was small (average 10‰) for
conversion of Corg to acetate-methyl, which was hardly further
fractionated during CH4 production. However, fractionation was strong
for CO2 conversion to CH4 (average 75‰), which generally accounted
for >50% of total CH4 production. Canonical correspondence
analysis did not reveal an effect of microbial community composition,
despite the fact that it exhibited a pronounced variability among the
different sediments. |
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