Preprints
https://doi.org/10.5194/bg-2022-117
https://doi.org/10.5194/bg-2022-117
 
24 May 2022
24 May 2022
Status: this preprint is currently under review for the journal BG.

Nutrient release and flux dynamics of CO2, CH4 and N2O in a coastal peatland driven by actively induced rewetting with brackish water from the Baltic Sea

Daniel Lars Pönisch1,, Anne Breznikar2,, Cordula Nina Gutekunst3, Gerald Jurasinski3, Gregor Rehder1, and Maren Voss2 Daniel Lars Pönisch et al.
  • 1Department of Marine Chemistry, Leibniz Institute for Baltic Sea Research Warnemünde (IOW), Rostock, Germany
  • 2Department of Biological Oceanography, Leibniz Institute for Baltic Sea Research Warnemünde (IOW), Rostock, Germany
  • 3Department of Landscape Ecology, Faculty of Agriculture and Environmental Sciences, University of Rostock, Germany
  • These authors contributed equally to this work.

Abstract. The rewetting of drained peatlands supports long-term nutrient removal in addition to reducing emissions of carbon dioxide (CO2) and nitrous oxide (N2O). However, rewetting may lead to short-term nutrient leaching into adjacent water and high methane (CH4) emissions. The consequences of rewetting with brackish water on nutrient and greenhouse gas (GHG) fluxes remain unclear, although beneficial effects such as lower CH4 emissions seem likely. Therefore, we studied the actively induced rewetting of a coastal peatland with brackish water, by comparing pre- and post-rewetting data from the peatland and the adjacent bay.

Both the potential transport of nutrients into adjacent coastal water and the shift of GHG fluxes (CO2, CH4, N2O) accompanying the change from drained to inundated conditions were analyzed based on measurements of the surface water concentrations of nutrients (dissolved inorganic nitrogen (DIN), phosphate (PO43-)), oxygen (O2), components of the CO2 system, CH4, and N2O together with manual closed-chamber measurements of GHG fluxes.

Our results revealed higher nutrient concentrations in the rewetted peatland than in the adjacent bay, indicating that nutrients leached out of the peat and were exported to the bay. A comparison of DIN concentrations of the bay with those of an unaffected reference station showed a significant increase after rewetting. The total nutrient export out of the peatland ranged between 12.5 and 36.5 t yr−1 for DIN-N and 0.2 ± 0.5 t yr−1 for PO4-P.

The peatland was also a source of GHG in the first year after rewetting. However, the spatial and temporal variability decreased and high CH4 emissions, as reported for freshwater rewetting, did not occur. CO2 fluxes decreased slightly from 0.29 ± 0.74 g m−2 h−1 (pre-rewetting) to 0.26 ± 0.29 g m−2 h−1 (post-rewetting). The availability of organic matter (OM) and dissolved nutrients were likely the most important drivers of continued CO2 production. Pre-rewetting CH4 fluxes ranged from 0.13 ± 1.01 mg m−2 h−1 (drained land site) to 11.4 ± 37.5 mg m−2 h−1 (ditch). After rewetting, CH4 fluxes on the formerly dry land increased by 1 order of magnitude (1.74 ± 7.59 mg m−2 h−1), whereas fluxes from the former ditch decreased to 8.5 ± 26.9 mg m−2 h−1. These comparatively low CH4 fluxes can likely be attributed to the suppression of methanogenesis by the available O2 and sulfate, which serve as alternative electron acceptors. The post-rewetting N2O flux was low, with an annual mean of 0.02 ± 0.07 mg m−2 h−1.

Our results suggest that rewetted coastal peatlands could account for high, currently unmonitored nutrient inputs into adjacent coastal water, at least on a short time scale such as a few years. However, rewetting with brackish water may decrease GHG emissions and might be favored over freshwater rewetting in order to reduce CH4 emissions.

Daniel Lars Pönisch et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2022-117', Anonymous Referee #1, 20 Jun 2022
  • RC2: 'Comment on bg-2022-117', Anonymous Referee #2, 07 Jul 2022

Daniel Lars Pönisch et al.

Data sets

Supplementary data of the discrete water sampling used in the publication "Nutrient release and flux dynamics of CO2, CH4, and N2O in a coastal peatland driven by actively induced rewetting with brackish water from the Baltic Sea" Pönisch, Daniel L., Breznikar, Anne http://doi.io-warnemuende.de/10.12754/data-2022-0003

Daniel Lars Pönisch et al.

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Short summary
Peatland rewetting is known to reduce dissolved nutrients and greenhouse gases, however, short-term nutrient leaching and high CH4 emissions shortly after rewetting are likely to occur. We investigated the rewetting of a coastal peatland with brackish water and its effects on nutrient release and greenhouse gas fluxes. Nutrient concentrations were higher in the peatland than in the adjacent bay, leading to an export. CH4 emissions did not increase, which is in contrast to freshwater rewetting.
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