Thermal stratification and the stability of meromixis in the Pretoria Salt Pan, South Africa

The Pretoria Salt Pan, South Africa, a small (0.076 km super(2)), shallow (Z sub(max) = 2.85 m), hypersaline, maar lake, lies within a clearly-defined crater and is fed by a perennial, slightly saline (3 g/l) artesian spring. The lake has two distinct solar-heated peaks in its temperature profile, each of these peaks located in a highly turbid (> 80 JTU) layer below a steep chemocline. The upper thermal peak, located at a depth of 10 cm, was transient, with a distinct diel pattern of diurnal heating and nocturnal cooling. The lower thermal peak, located below a steep chemocline and centred at approximately 60 cm, was stable and showed a seasonal pattern of winter heating (maximum: 38.5 degree C) and summer cooling (minimum: 27.4 degree C).