There are an increasing number of cyanobacteria genera and species which have been found to produce a suite of biologically active compounds. Not surprisingly, many of these compounds have proven to be very toxic to a variety of organisms including humans. Some species of cyanobacteria are capable of producing a variety of toxic compounds although some toxins appear to be confined to specific cyanobacteria.
The cyanobacteria of concern are generally freshwater or brackish water species and are commonly found as 'blooms' in slow-flowing, nutrient-rich waters, usually in the warmer months of the year (when both temperature and sunlight are optimal). Blooms are often found in farm dams or ponds where very little mixing occurs, allowing warm water layers to form near the surface. As a result, highly toxic 'scum' material often forms on the water surface, creating a potential danger for livestock and, indeed, humans.
Below is a list of known cyanobacteria and the toxins they produce.