1. Department
of Surface Waters Research and Management Eawag−Swiss Federal Institute of Aquatic Science and Technology, Seestrasse 79, CH-6047 Kastanienbaum, Switzerland
2. Institute
of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Universitätsstrasse
16, CH-8092 Zürich, Switzerland
3. Faculty
of Geography and Earth Sciences, University of Latvia, Jelgavas iela 1, LV-1004, Riga, Latvia
4. Institute
of Biology, University of Latvia, Miera iela 3, LV-2169, Salaspils, Latvia
5. Department
of Inorganic and Analytical Chemistry, University of Geneva, Quai E.-Ansermet
30, 1211 Geneva, Switzerland