1. Aquatic Ecology and Water Quality Management Group, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands
2. Department of Biology, University of Namur, Rue de Bruxelles 61, 5000 Namur, Belgium
3. Wageningen Environmental Research, P.O. Box 47, 6700 AA Wageningen, The Netherlands
4. Safety and Environmental Assurance Centre, Unilever, Colworth Science Park, Sharnbrook MK441LQ, United Kingdom