Introduction

Harmful algal blooms (HABs) occurring in freshwater, and the associated toxins they produce, are dangerous to animals and humans. HABs also reduce the recreational value of surface waters, thereby inuencing tourism and the quality of life for residents and visitors. A number of reports and studies have been carried out since the beginning of this century to elucidate the extent of the problem in freshwater systems, our current understanding, and future research needs [1-4]. Many organisms may produce freshwater HABs, including cyanobacteria (formerly known as blue-green algae), haptophytes, macroalgae, euglenophytes, dinoagellates, and others. Cyanobacteria are typically the taxa of greatest concern with respect to HABs in freshwater systems and include organisms such as Anabaena, Microcystis, Nodularia, Cylindrospermopsis, and others. Not all cyanobacteria are toxic. In some cases, species known to produce toxic metabolites do not do so. Research suggests, however, that the majority of cyanobacterial blooms observed are toxic in nature.