The influence of pool size on species diversity and water chemistry in temporary rock pools on Domboshawa Mountain, northern Zimbabwe

The effect of pool size (area and depth) on species diversity and physicochemical characteristics of rock pool habitats on Domboshawa Mountain, northern Zimbabwe, was studied from December 2006 to May 2007. Pools were categorised based on maximum depth. Pool duration was a key factor structuring pool communities, driving their species diversity and nutrient content. Active predatory insects (Coleoptera, Odonata, Hemiptera) and zooplankton (Cladocera, Copepoda, Rotifera species) were associated with long- lived pools. As pool duration increased, early phytoplankton communities dominated by short-residence green algae were replaced by blue-green algae. The number of species present increased as pool area increased. Using depth as a proxy for disturbance, species composition in rock pools was influenced by the duration of inundation. A unique rock pool community with a filter-feeding component dominated by Cladocera, and from which large branchiopods were absent, is described. Nutrient status and community diversity in rock pools are determined by pool size, and pool depth, a proxy for habitat duration, is a major structuring factor in these temporary aquatic habitats.