Temporary freshwater rockpools as ecological islands

Abstract

Temporary freshwater pools are isolated, ephemeral lentic habitats. Pools form on outcrops of Upper Coralline limestone and Lower Coralline limestone in depressions formed by solution and pitting. These pools were studied throughout one wet season from September till April. Hydroperiod length varied considerably between pools. The surface area to volume ratio is the main determinant of the pool's ability to retain water. The length of hydroperiod varied according to the physical parameters of the pool. Pools with high sediment volumes tend to maintain water for longer periods. Floral communities of these pools are composed of terrestrial, amphibious and aquatic species. Hydroperiod length is a prime determinant of community structure as long periods of submersion prevent the establishment of terrestrial species. Hortonian overland flow limits the extent to which the freshwater pools can be considered as ecological islands. Surface area of a pool is not a good predictor of pool diversity as a number of small pools were observed to have greater species diversity than pools with larger surface areas.