Duration of inundation and change in physical and chemical characteristics of small temporary pans in South Africa

The day-to-day fluctuations in water depth, water temperature, dissolved oxygen concentration, pH, conductivity and turbidity of six pans at Bain's Vlei, South Africa, were monitored during five successive inundations from September 1988 to April 1989. Mean duration of inundations was 13.9 days, daytime water temperatures ranged from 10.5 °C–33.1 °C, dissolved oxygen ranged from 30% to 142% saturation and conductivity ranged from 43–2630 µ S cm^–1. F-test multivariate analysis indicated that physical and chemical characteristics of all pans were similar during the first inundation but differed significantly during the subsequent inundations. The aquatic pan environment is ephemeral, fluctuating and unpredictable. The biological community should consequently feature adaptations to these conditions.