Biogeochemical Characteristics of the Last Floating Coastal Bog Remnant in Europe, the Sehestedt Bog

With the current risks caused by sea level rise and increased extreme weather events, the study of natural coastal systems has never been more important. Erosion and anthropogenic forcing led to disappeared of the majority of coastal bogs in Europe. Here, we report on case study of a unique bog remnant still under influence by seawater which floats during storm floods. We investigated biogeochemical characteristics and discuss mechanisms that influence buoyancy, which is of vital importance for the conservation of the bog and can provide insights into the functioning of coastal bogs and potential consequences of future sea level rise. The studied area is characterized by a steep salinity gradient and marine clay deposits provide the ‘hinge’ that allows the upper peat layers to float. Our results show out that buoyancy is driven by a combination of factors: the density differences, desiccation along the edges and methane production. If the ability to float is reduced in coastal bogs, the impact of erosion and the sum of several other processes (i.e., peat decomposition, salt stress, clay sedimentation, internal eutrophication and reduced methanogenesis) can cause a shift in environmental conditions and lead to loss of this unique habitat and its characteristic species.