BioGeoChemistry of Tidal Flats


S. Jansen, E. Walpersdorf, U. Werner, M. Billerbeck, D. de Beer

Dynamics of oxygen and sulfide in intertidal sediments

Intertidal sediments can be regarded as giant biocatalytic filters, in which various processes such as photosynthesis, sulfate reduction and sulfide oxidation take place at high areal rates. The purpose of an ongoing project at the Janssand, an intertidal sandplate south of the German Wadden sea island Spiekeroog, is to characterize these processes and determine their dependency on spatial and temporal variables. Due to differences in altitude, high concentrations of reduced products seep out at the lower points. The use of microsensor measurements enables highly resolved mapping of the dynamic processes at these sites over several tidal cycles. Previous data show strong dynamics of oxygen and sulfide as influenced by seasons, tides and day/night cycling. These dynamics are most clearly visible at the seeps. New, more detailed experiments further quantify these processes. Biological sulfide oxidation is also shown to be important. Future experiments will address, amongst others, benthic photosynthesis and various methods of determining the oxygen uptake.