Congruent changes in microbial community dynamics and ecosystem methane fluxes following natural drought in two restored fens

Unger, Viktoria; Liebner, Susanne; Koebsch, Franziska; Horn, Fabian; Sachs, Torsten; Kallmeyer, Jens; Knorr, Klaus‐Holger; Rehder, Gregor; Gottschalk, Pia; Jurasinski, Gerald

doi:10.1016/j.soilbio.2021.108348

Cited by 19 publications

(20 citation statements)

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“…Mean annual temperature at the study area (hereafter "Hütelmoor") was 9.6 • C, and mean annual rainfall was 635 mm (1991-2020, derived from the freely available grid product of the German Weather Service (DWD), for which 1 km gridded data are extrapolated from weather station data according to Müller-Westermeier, 1995). The Hütelmoor is a minerotrophic coastal paludification fen that was drained and used for agriculture between the 1970s and 1990s (Koch et al, 2014;Hahn et al, 2015;Unger et al, 2021a). Drainage led to water tables up to 1.60 m below surface (Glatzel et al, 2011) and to rapid peat decomposition (Koch et al, 2017).…”

Section: Site Descriptionmentioning

confidence: 99%

“…We conducted fieldwork at the same four locations (HC1, HC2, HC3 and HC4) discussed in Koebsch et al (2019) and Wen et al (2018), which cover different salinity regimes, especially in deeper layers of the peat. Details regarding field sampling protocols (peat biogeochemistry and microorganisms) and data analysis can be found in Wen et al (2018) and Unger et al (2021a). The microbial analysis was conducted in the same laboratory and strictly followed the same protocols regarding DNA and RNA extraction and regarding primer combinations during sequencing and qPCR.…”

Section: Field Data Collectionmentioning

confidence: 99%

“…Therefore, we refer to the geochemical, trace gas and microbial data from Wen et al (2018) as "Baseline2014" (and "base14" in the figures). Data from Unger et al (2021a) provided insights into the dynamics during the drought in 2018 at location HC2 and are referred to as "Drought2018" (and "drought18" in the figures).…”

Section: Field Data Collectionmentioning

confidence: 99%

“…Soil cores and pore water samples were also taken on 16 May 2019 ("Postinflow Spring2019") at one of our sampling locations (HC2; see Fig. 2) for better comparison with the previous drought study (Unger et al, 2021a) in order to increase the temporal resolution at this common location. We derived groundwater level data from a data logger and pressure transducer (Dipper PTEC, SEBA, Kaufbeuren, Germany) installed permanently near location HC2 at 0.49 m depth.…”

Section: Field Data Collectionmentioning

confidence: 99%

“…Amplification via polymerase chain reaction (PCR) of 16S rRNA genes of DNA and cDNA samples was performed using the universal primer combination Uni515-F/Uni806-R (Caporaso et al, 2011), for both bacteria and archaea, and primer combination S-D-Arch-0349-a-S-17/S-D-Arch-0786-a-A-20 (Takai and Horikoshi, 2000) for more precise archaea detection. Please note that Wen et al (2018) and Unger et al (2021a) used a specific bacterial primer combination (S-D-Bact-0341-b-S-17/S-DBact-0785-a-A-21) instead of the universal primer we used here. We decided on the universal primer because it has equal resolution for bacteria but covers both bacteria and archaea, providing some support for the qPCR data.…”

Section: Pcr Amplification and Sequencingmentioning

confidence: 99%

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Effects of brackish water inflow on methane-cycling microbial communities in a freshwater rewetted coastal fen

et al. 2022

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Abstract. Rewetted peatlands can be a significant source of methane (CH4), but in coastal ecosystems, input of sulfate-rich seawater could potentially mitigate these emissions. The presence of sulfate as an electron acceptor during organic matter decomposition is known to suppress methanogenesis by favoring the growth of sulfate reducers, which outcompete methanogens for substrate. We investigated the effects of a brackish water inflow on the microbial communities relative to CH4 production–consumption dynamics in a freshwater rewetted fen at the southern Baltic Sea coast after a storm surge in January 2019 and analyzed our data in context with the previous freshwater rewetted state (2014 serves as our baseline) and the conditions after a severe drought in 2018 (Fig. 1). We took peat cores at four previously sampled locations along a brackishness gradient to compare soil and pore water geochemistry as well as the microbial methane- and sulfate-cycling communities with the previous conditions. We used high-throughput sequencing and quantitative polymerase chain reaction (qPCR) to characterize pools of DNA and RNA targeting total and putatively active bacteria and archaea. Furthermore, we measured CH4 fluxes along the gradient and determined the concentrations and isotopic signatures of trace gases in the peat. We found that both the inflow effect of brackish water and the preceding drought increased the sulfate availability in the surface and pore water. Nevertheless, peat soil CH4 concentrations and the 13C compositions of CH4 and total dissolved inorganic carbon (DIC) indicated ongoing methanogenesis and little methane oxidation. Accordingly, we did not observe a decrease in absolute methanogenic archaea abundance or a substantial change in methanogenic community composition following the inflow but found that the methanogenic community had mainly changed during the preceding drought. In contrast, absolute abundances of aerobic methanotrophic bacteria decreased back to their pre-drought level after the inflow, while they had increased during the drought year. In line with the higher sulfate concentrations, the absolute abundances of sulfate-reducing bacteria (SRB) increased – as expected – by almost 3 orders of magnitude compared to the freshwater state and also exceeded abundances recorded during the drought by over 2 orders of magnitude. Against our expectations, methanotrophic archaea (ANME), capable of sulfate-mediated anaerobic methane oxidation, did not increase in abundance after the brackish water inflow. Altogether, we could find no microbial evidence for hampered methane production or increased methane consumption in the peat soil after the brackish water inflow. Because Koebsch et al. (2020) reported a new minimum in CH4 fluxes at this site since rewetting of the site in 2009, methane oxidation may, however, take place in the water column above the peat soil or in the loose organic litter on the ground. This highlights the importance of considering all compartments across the peat–water–atmosphere continuum to develop an in-depth understanding of inflow events in rewetted peatlands. We propose that the changes in microbial communities and greenhouse gas (GHG) fluxes relative to the previous freshwater rewetting state cannot be explained with the brackish water inflow alone but were potentially reinforced by a biogeochemical legacy effect of the preceding drought.

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Section: Site Descriptionmentioning

confidence: 99%