1. Ecology Unit University of León Campus de Vegazana S/N 24071 León Spain
2. Freshwater Centre Finnish Environment Institute PO Box 413 FI‐90014 Oulu Finland
3. Geography Research Unit University of Oulu PO Box 3000 FI‐90014 Oulu Finland
4. Department of Earth Sciences University College London London WC1E 6BT UK
5. School of GeoSciences Grant Institute University of Edinburgh James Hutton Road Edinburgh EH9 3FE UK