Cyanobacteria are common in fresh water throughout the world and are known to produce several types of toxins: microcystins which are heat-stable, cyclic heptapeptide hepatotoxins and also promote tumor growth and inhibit protein phosphatases; anatoxin, a neurotoxin, which inhibits acetylcholinesterase; and paralytic shellfish poisoning (PSP) toxins, such as saxitoxin, which are also neurotoxic.