Contents of total carbon and nitrogen were measured by high-temperature catalytic oxidation using a LECO CHNS-932. Inorganic carbon concentrations were measured on a coulometer after acidification with 2M perchloric acid (UIC, USA). The organic carbon content was then calculated as the difference between total and inorganic carbon. Porosity was calculated according to Berner (1982) using the water content and the sediment density. Sedimentation rates were derived from water depth surveys, conducted by the hydropower company (BKW, Switzerland) in 1990 and 2004.