1. Department of Aquatic Ecology, Netherlands Institute of Ecology, Royal Netherlands Academy of Arts and Sciences (NIOO-KNAW), P.O. Box 50, 6700 AB Wageningen, The Netherlands
2. Department of Animal Ecology and Ecophysiology, Radboud University Nijmegen, Institute for Water and Wetland Research, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
3. Department of Aquatic Ecology and Environmental Biology, Radboud University Nijmegen, Institute for Water and Wetland Research, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
4. Netherlands Centre for Biodiversity Naturalis, P.O. Box 9517, 2300 RA Leiden, The Netherlands