Lakes ST and WM show the highest TE concentrations of all studied lakes. This might be in correlation to the high amount of forest in their catchment areas. Tree canopies are known to gather particles and pollutants from air, thereby increasing the input to the underlying soil (forest filter effect; . The extraordinarily high Cu concentrations present in Lake ST since 1966 and declining since 1981 could be associated with the adjacent nuclear power plant (Kernkraftwerk Rheinsberg), that was operated between . It used water from the adjacent Lake Nehmitz as coolant. The warm waste water, however, was expelled into Lake ST (UBA 2004) leading to an increase in average water temperature and could have carried Cu from the external cooling system through which it was transferred.