In Grosser Arbersee, a cirque lake in the Bavarian Forest (Germany) the acidification chronology since the late-glacial period has been studied paleolimnologically, applying subfossil diatom assemblages. Distinct phases of acidification could be detected, both natural ones by post-glacial development of soils and vegetation in the catchment and anthropogenic ones by mineral acid depositions. Whereas the first phases were accompanied (and most probably caused as well) by increases in organic carbon contents, the recent phases are characterized by losses of organic carbon contents in the lake. In various sensitive lakes in Central Europe the fate of organic carbon (measured as loss on ignition) is documented for the anthropogenic acidification period. In lowland as well as in high alpine lakes this process is accompanied by loss of organic carbon. These losses are by no means uniform. On the contrary, they range between 10 and 90% per drop of one pH-unit, in each lake calculated from estimated preacidification pH-conditions. | In Grosser Arbersee, a cirque lake in the Bavarian Forest (Germany), the acidification chronology since the late-glacial period has been studied paleolimnologically applying subfossil diatom assemblages. Distinct phases of acidification could be detected, both natural ones by post-glacial development of soils and vegetation in the catchment and anthropogenic ones by mineral acid depositions. Whereas the first phases were accompanied (and most probably caused as well) by increases in organic carbon contents, the recent phases are characterized by losses of organic carbon contents in the lake. In various sensitive lakes in Central Europe the fate of organic carbon (measured as loss on ignition) is documented for the anthropogenic acidification period. In lowland as well as in high alpine lakes this process is accompanied by loss of organic carbon. These losses are by no means uniform. On the contrary, they range between 10 and 90% per drop of one pH-unit, in each lake calculated from estimated preacidification pH-conditions.