BioGeoChemistry of Tidal Flats


J. Köster, H. Sass, E. Freese, J. Rullkötter

Pore water profiles in intertidal sediments from the German wadden sea

Most studies of intertidal sediments of the German Wadden Sea were restricted to near-surface layers. At present, there is little knowledge about deeper sediments and their composition and the dynamics of pore water therein. We investigated the lithology, organic matter, and pore water composition of sediment down to a depth of 5.5 m. Sediment cores were taken at different sites and at different seasons. The pore water shows complex profiles obviously resulting from the interaction of microbial processes and pore water dynamics. Dissolved organic carbon slightly increases in core intervals with higher mud and total organic carbon contents. The sulfate concentrations display two maxima separated by a zone of sulfate depletion and maximum ammonium concentrations. Variations with time suggest that pore water profiles shaped by microbiological processes were modified by lateral inflow of sea water as well as mixing with sulfate- and chloride-depleted water.