Discharge of ground water from Wadden Sea Sediments: Release of Nutrients and formation of sand boils
Submarine groundwater discharge was observed for different sedimentologicalsettings of coastal areas around the world. In several regions discharge of fluids from the seabed is associated with formation of pockmarks or other morphological features at the seafloor. Since sampling of fluids and sediments at e.g., pockmarks is rathercomplicate, the understanding of the flow field and the spatial distribution of chemical components around discharge sites is rather limited.Studies in the Wadden Sea of the Weser estuary showed that significant areas are affected by discharge of freshwater from below. In several cases high flow ratescause formation of "sand boils". Based on pore water studies and flow measurements discharge rates and chemical composition (e.g., nutrients, CH4) were determined. Flow rates of several liter per hour were observed. Small scale sampling allowed the determination of the flow field at the discharge sites. A budget for the release of nutrients for this part of the Wadden Sea is provided.