Pfiesteria is a single-celled planktonic creature (neither a true animal or plant). Billions lie dormant on the sea bed. In response to a chemical released naturally by fish, the pfiesteria develop sperm-like tails and swim towards the fish, which they kill or stun by releasing toxins. Changing shape again, the plankton develop a straw-like device by which they attach themselves to the fish and suck up its flesh.
Pfiesteria for red tides, up to six kilometres long, killing millions of fish at a time. Fishermen have suffered memory loss and developed open sores by breathing near the plankton: one California laboratory researching its effects on humans had to be shut down when researchers developed mysterious illnesses. There is no cure for the effects of pfiesteria.
Red tides have been reported off the east coast of America, Tasmania, Taiwan, Guatemala, Korea, Hong Kong, Venezuela, Iceland, the UK, Papua New Guinea, Sabah, Brunei, the Philippines, Scandinavia, Germany and Italy.