ABSTRACT
Cyanobacterial blooms and cyanotoxins present a special challenge to moni toring programmes because the requirements are different from well-recognised monitoring designs both for pathogenic bacteria and for toxic chemicals. Pathogen concentrations are highest close to sewage outfalls or the inflow of agricultural runoff polluted by livestock faeces and they are diluted with increasing distance from such sources. In contrast, cyanobacte ria multiply in the open water environment and scum-forming species are often dramatically concentrated by wind action. Furthermore, formation and dispersion of scums may change within days or even hours, making assess ment of the associated hazard difficult. Toxic chemicals are dissolved in the water or bound to sediments. In contrast, at least while the producer cells remain intact, cyanotoxins are chiefly contained within the cells. Therefore, they may shift position in the water body with the cells and accumulate to hazardous concentrations. Consequently, monitoring strategies must encom pass cell-bound toxins in addition to extracellular toxin pools.
