Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 14, issue 18
Biogeosciences, 14, 4375–4389, 2017
https://doi.org/10.5194/bg-14-4375-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 14, 4375–4389, 2017
https://doi.org/10.5194/bg-14-4375-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 29 Sep 2017

Research article | 29 Sep 2017

Carbon degradation in agricultural soils flooded with seawater after managed coastal realignment

Kamilla S. Sjøgaard1, Alexander H. Treusch1, and Thomas B. Valdemarsen2 Kamilla S. Sjøgaard et al.
  • 1Nordcee, Department of Biology, University of Southern Denmark, Odense M, 5230, Denmark
  • 2Department of Biology, University of Southern Denmark, Odense M, 5230, Denmark

Abstract. Permanent flooding of low-lying coastal areas is a growing threat due to climate change and related sea-level rise. An increasingly common solution to protect coastal areas lying below sea level is intentional flooding by "managed coastal realignment". However, the biogeochemical implications of flooding agricultural soils with seawater are still not well understood. We conducted a 1-year mesocosm experiment to investigate microbial carbon degradation processes in soils flooded with seawater. Agricultural soils were sampled on the northern coast of the island Fyn (Denmark) at Gyldensteen Strand, an area that was subsequently flooded in a coastal realignment project. We found rapid carbon degradation to TCO2 1 day after experimental flooding and onwards and microbial sulfate reduction established quickly as an important mineralization pathway. Nevertheless, no free sulfide was observed as it precipitated as Fe–S compounds with Fe acting as a natural buffer, preventing toxic effects of free sulfide in soils flooded with seawater. Organic carbon degradation decreased significantly after 6 months, indicating that most of the soil organic carbon was refractory towards microbial degradation under the anoxic conditions created in the soil after flooding. During the experiment only 6–7 % of the initial soil organic carbon pools were degraded. On this basis we suggest that most of the organic carbon present in coastal soils exposed to flooding through sea-level rise or managed coastal realignment will be permanently preserved.

Publications Copernicus
Download
Short summary
Permanent flooding of low-lying coastal areas is a growing threat due to climate-change-related sea-level rise. To reduce coastal damage, buffer zones can be created by managed coastal realignment where existing dykes are breached and new dykes are built further inland. We studied the impacts on organic matter degradation in soils flooded with seawater by managed coastal realignment and suggest that most of the organic carbon present in coastal soils will be permanently preserved after flooding.
Permanent flooding of low-lying coastal areas is a growing threat due to climate-change-related...
Citation