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

Other literature type, Article English OPEN
Sjøgaard, Kamilla S. ; Treusch, Alexander H. ; Valdemarsen, Thomas B. (2016)
  • Publisher: Copernicus Publications
  • Journal: (issn: 1726-4189, eissn: 1726-4189)
  • Related identifiers: doi: 10.5194/bg-2016-417, doi: 10.5194/bg-14-4375-2017
  • Subject: Ecology | QH540-549.5 | QE1-996.5 | QH501-531 | Geology | Life
    mesheuropmc: fungi | parasitic diseases | geographic locations

Climate change induced sea level rise is expected to continue for centuries and cause permanent flooding of low lying coastal areas. Furthermore, intentional flooding of coastal areas through ‘managed coastal realignment’, may also become a common solution to protect coastal areas. So far, the biogeochemical implications of flooding soils with seawater are not well investigated. In this study we conducted a 1-year mesocosm experiment to investigate microbial carbon degradation processes in soils flooded with seawater. The used soils were sampled at on Northern Fyn (Denmark), in an area (Gyldensteen Strand) that was planned to be flooded in a coastal realignment project. We found rapid carbon degradation almost immediately after flooding and microbial sulfate reduction rapidly established as the dominant 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. The refractory nature of the terrestrial organic carbon in combination with the anoxic conditions created in the soil after flooding caused significantly decreased organic carbon degradation after 6 months. During the experiment only 6–7 % of the initial organic carbon pools were degraded. On this basis we suggest that flooding of coastal soils through sea level rise or managed coastal realignment, will cause significant C-preservation and create a negative feedback on atmospheric carbon dioxide concentrations.
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