@article{KoebschWinkelLiebneretal.2019,
  author    = {Koebsch, Franziska and Winkel, Matthias and Liebner, Susanne and Liu, Bo and Westphal, Julia and Schmiedinger, Iris and Spitzy, Alejandro and Gehre, Matthias and Jurasinski, Gerald and K{\"o}hler, Stefan and Unger, Viktoria and Koch, Marian and Sachs, Torsten and B{\"o}ttcher, Michael E.},
  title     = {Sulfate deprivation triggers high methane production in a disturbed and rewetted coastal peatland},
  series = {Biogeosciences},
  volume    = {16},
  journal   = {Biogeosciences},
  number    = {9},
  publisher = {Copernicus},
  address   = {G{\"o}ttingen},
  issn      = {1726-4170},
  doi       = {10.5194/bg-16-1937-2019},
  pages     = {1937 -- 1953},
  year      = {2019},
  abstract  = {In natural coastal wetlands, high supplies of marine sulfate suppress methanogenesis. Coastal wetlands are, however, often subject to disturbance by diking and drainage for agricultural use and can turn to potent methane sources when rewetted for remediation. This suggests that preceding land use measures can suspend the sulfate-related methane suppressing mechanisms. Here, we unravel the hydrological relocation and biogeochemical S and C transformation processes that induced high methane emissions in a disturbed and rewetted peatland despite former brackish impact. The underlying processes were investigated along a transect of increasing distance to the coastline using a combination of concentration patterns, stable isotope partitioning, and analysis of the microbial community structure. We found that diking and freshwater rewetting caused a distinct freshening and an efficient depletion of the brackish sulfate reservoir by dissimilatory sulfate reduction (DSR). Despite some legacy effects of brackish impact expressed as high amounts of sedimentary S and elevated electrical conductivities, contemporary metabolic processes operated mainly under sulfate-limited conditions. This opened up favorable conditions for the establishment of a prospering methanogenic community in the top 30-40 cm of peat, the structure and physiology of which resemble those of terrestrial organic-rich environments. Locally, high amounts of sulfate persisted in deeper peat layers through the inhibition of DSR, probably by competitive electron acceptors of terrestrial origin, for example Fe(III). However, as sulfate occurred only in peat layers below 30-40 cm, it did not interfere with high methane emissions on an ecosystem scale. Our results indicate that the climate effect of disturbed and remediated coastal wetlands cannot simply be derived by analogy with their natural counterparts. From a greenhouse gas perspective, the re-exposure of diked wetlands to natural coastal dynamics would literally open up the floodgates for a replenishment of the marine sulfate pool and therefore constitute an efficient measure to reduce methane emissions.},
  language  = {en}
}
@article{WenUngerJurasinskietal.2018,
  author    = {Wen, Xi and Unger, Viktoria and Jurasinski, Gerald and Koebsch, Franziska and Horn, Fabian and Rehder, Gregor and Sachs, Torsten and Zak, Dominik and Lischeid, Gunnar and Knorr, Klaus-Holger and Boettcher, Michael E. and Winkel, Matthias and Bodelier, Paul L. E. and Liebner, Susanne},
  title     = {Predominance of methanogens over methanotrophs in rewetted fens characterized by high methane emissions},
  series = {Biogeosciences},
  volume    = {15},
  journal   = {Biogeosciences},
  number    = {21},
  publisher = {Copernicus},
  address   = {G{\"o}ttingen},
  issn      = {1726-4170},
  doi       = {10.5194/bg-15-6519-2018},
  pages     = {6519 -- 6536},
  year      = {2018},
  abstract  = {The rewetting of drained peatlands alters peat geochemistry and often leads to sustained elevated methane emission. Although this methane is produced entirely by microbial activity, the distribution and abundance of methane-cycling microbes in rewetted peatlands, especially in fens, is rarely described. In this study, we compare the community composition and abundance of methane-cycling microbes in relation to peat porewater geochemistry in two rewetted fens in northeastern Germany, a coastal brackish fen and a freshwater riparian fen, with known high methane fluxes. We utilized 16S rRNA high-throughput sequencing and quantitative polymerase chain reaction (qPCR) on 16S rRNA, mcrA, and pmoA genes to determine microbial community composition and the abundance of total bacteria, methanogens, and methanotrophs. Electrical conductivity (EC) was more than 3 times higher in the coastal fen than in the riparian fen, averaging 5.3 and 1.5 mS cm(-1), respectively. Porewater concentrations of terminal electron acceptors (TEAs) varied within and among the fens. This was also reflected in similarly high intra- and inter-site variations of microbial community composition. Despite these differences in environmental conditions and electron acceptor availability, we found a low abundance of methanotrophs and a high abundance of methanogens, represented in particular by Methanosaetaceae, in both fens. This suggests that rapid (re) establishment of methanogens and slow (re) establishment of methanotrophs contributes to prolonged increased methane emissions following rewetting.},
  language  = {en}
}