A Ceratium hirundinella (O.F. Müller) bloom in Hartbeespoort Dam, South Africa

During the late winter to early spring of 1999 Ceratium hirundinella was recorded for the first time in the Hartbeespoort Dam, South Africa, and in bloom forming conditions. The C. hirundinella bloom started in July 1999 after complete mixing occurred and a Microcystis aeruginosa bloom disappeared. C. hirundinella occurred in chlorophyll a concentrations up to 4243 mg/l. The clogging of filters at water care works and a fish kill were encountered during the same period, in the area. This paper discusses the extent of the bloom, the possible causes and the water characteristics found in the Hartbeespoort Dam during the development of the bloom. WaterSA Vol.27(2) 2001: 269-27