The high carbon burial rate in conjunction withmodest mineralisation rates (range 59-208gC m-2yr-1) results in very high OC burial efficiencies in Lake Wohlen (85-92%). Lake Wohlen is a run-of-the-river reservoir, receiving high particle loads from an erosion-prone high-altitude Alpine region (~ 4,000 m above sea level). The high sedimentation rates in turn result in very short oxygen exposure time (range 4-50 days) of the deposited sediment. For comparison, oxygen exposure times in lakes with oxygenated bottom water are usually in the range of months to years (Maerki, 2007; Sobek et al.,
inpreparation). Wohlen’s extreme burial efficiency is probably from the result of transport dynamics and rapid sediment accumulation. In shallow water (6to 13 m depth at the study sites) with a short residence time (~2 days), OC is protected from oxidation by quick accumulation under a thick layer of fresh sediment.