1. Helmholtz Centre for Environmental Research; Brueckstrasse 3a,; D-39114; Magdeburg; Germany
2. Department of Freshwater Conservation; Brandenburg University of Technology; D-03013; Cottbus; Germany
3. Institute of Environmental Physics; University of Heidelberg; D-69120; Heidelberg; Germany
4. Department of Limnology of Stratified Lakes; Leibniz Institute of Freshwater Ecology and Inland Fisheries; Neuglobsow,; D-16775; Stechlin; Germany