Cyanobacterial blooms, mass developments of cyanobacteria floating at the surface of waterbodies, have become a recurrent and increasingly important phenomenon in freshwaters worldwide over recent decades. The formation of such blooms in surface waters is closely linked to water eutrophication (Chorus, 2001).

These nuisance blooms represent major potential hazards to human and animal health, and interfere in various negative ways with the sustainable use of surface waters for e.g. drinking water treatment, recreation, irrigation and fisheries. Between 25 and 70% of the blooms are toxic (Sivonen, 1996).

The cyanotoxins are mainly released in the water column during collapse of the blooms. The ingestion or contact with water containing cyanobacterial cells or toxins can cause health damage (Bell & Codd 1996; Carmichael et al. 2001; de Figueiredo et al., 2004; Codd et al., 2005; Dittmann & Wiegand, 2006).