Nuisance organisms in drinking water
Toxic blue-green algae
Common blue-green algae produce toxins which can cause gastroenteritis and skin and eye irritations. Animals have died from drinking algal scum, and there are concerns that algae-produced liver toxins could promote live cancer in humans.
Because they are photosynthetic and aquatic, cyanobacteria are often called "blue-green algae". This name is convenient for talking about organisms in the water that make their own food, but does not reflect any relationship between the cyanobacteria and other organisms called algae. Cyanobacteria are relatives of the bacteria, not eukaryotes, and it is only the chloroplast in eukaryotic algae to which the cyanobacteria are related.