Dynamics in the isotope hydrobiogeochemistry in a coastal peatland and associated surface waters at the southern Baltic Sea

Anna-Kathrina Jenner1, Julia Westphal1, Catia Milene Ehlert von Ahn1, Benjamin Rach1, Lucas Winski1, Christoph Malik1, Iris Schmiedinger1, Michael E. Böttcher1
1 Geochemie & Isotopen-Biogeochemie, Institut für Ostseeforschung

11.5 in Isotopenmethoden zur Analyse von Stoffumsatz und Fließprozessen

In the present study the temporal and spatial dynamics in the isotope hydrobiogeochemical composition of surface water in a rewetting coastal peatland at the southern Baltic Sea was investigated during different hydrological conditions. The peatland is located at the southern Baltic Sea and is under impact by rare storm-induced flooding events. The temporal changes in salinity and element concentrations have substantial consequences for the biogeochemical processes taking place in the organic-rich soils that are further be reflected by the composition of peatland surface waters. Using a multi-isotope (H, C, O, S) tracer approach in combination with redox-sensitive trace elements and nutrients, the aim of this study was the characterization of water mixing processes and sinks, sources and transformations in associated biogeochemical element cycles as reflected by the composition of connected surface waters of the southern Baltic Sea.

After a strong storm event in winter 2019 a large surface area of the peatland was flooded by brackish Baltic Sea surface water enhancing the salinity in the surface wates. The input from brackish seawater modified the stock of electron acceptors to foster microbial sulfate reduction. The peatland is draining via surface water flow into the Warnow river estuary and via submarine ground water flow directly into sediments of the coastal Baltic Sea. Therefore, seasonal sampling was also carried out in the Warnow river since year 2017. The upper part of the Warnow river reflects changes in seasonal meteorological and hydrological consitions in the catchment area that is under multiple anthropogenic impacts. The estuarine part of the Warnow river is further impacted by temporal mixing with Baltic Sea water.

Acknowledgement: This study is supported by the DFG research training group Baltic TRANSCOAST, DAAD, and the Leibniz IOW.