Effects of enhanced drought on the diversity of methanogens in an acidic fen
O 1.5 in Ecosystem Function
15.04.2010, 09:30-09:45, H13
Acidic wetlands are sources of the greenhouse gas methane. Global warming might result in a temperature rise and might lead to more extreme weather phenomenons. Thus the methanogenic community of an acidic fen and its reaction to enhanced drought were investigated. Translated amino acid sequences of the structural gene marker mcrA (coding for the Alpha-subunit of the methyl coenzyme M reductase) grouped into 21 species-level operational taxonomic units (OTUs), displaying a high diversity of fen methanogens. Some OTUs were related to known Methanomicrobiales, Methanobacteriaceae, Methanosarcinaceae, and Methanocellaceae, while 10 OTUs were not closely related to known methanogens, indicating phylogenetic novelty of fen methanogens. An artificial watertable drawdown of up to 60 cm resulted in reduced methanogenic diversity based on the Shannon diversity index while rewetting restored diversity to the original level. Based on qPCR analysis of mcrA, methanogens were most abundant in the 20-30 cm soil layer while highest mcrA expression was found in the 0-20 cm soil layers. The relative mcrA copy numbers were not changed by the artificial drought, but the rewetting event increased relative mcrA copy numbers. The level of mcrA expression was not affected by artificial drought or rewetting. TRFLP analyses revealed high similarity in the methanogenic community structure during the course of the experiment, even though minor changes in community composition due to artificial drought were observed. The TRFLP profiles of expressed mcrA differed from those of the DNA profiles. Artificial drought had only small effects on the active methanogenic community. The collective data indicate that (i) a novel diversity of methanogens occurs in the acidic fen, (ii) the abundance of methanogens in the acidic fen is rather stable under extreme weather conditions, and (iii) artificial drought does not alter mcrA expression.
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