1. Swiss Federal Institute of Aquatic Science and Technology (Eawag), 8600 Dübendorf, Switzerland
2. Department of Biological and Environmental Sciences, University of Gothenburg, Carl Skottsbergs gata 22B, 41319 Gothenburg, Sweden
3. Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich, 8092 Zürich, Switzerland