1. Institute of Water Studies, Department of Earth Sciences, University of the Western Cape, Bellville, South Africa
2. Department of Geography and Environmental Sciences, University of Venda, Thohoyandou, South Africa
3. Aquatic Systems Research Group, School of Biology and Environmental Sciences, University of Mpumalanga, Nelspruit, South Africa ;
4. South African Institute for Aquatic Biodiversity, Grahamstown, South Africa