Swimming manatee (Photo credit unknown)

This humpback whale died from saxitoxin which accumulated in the mackerel it was eating. (G. Early)

A cow killed by Cyanobacteria (W. Carmichael)

An Anabaena bloom. (W. Carmichael)

A massive fish kill resulting from anoxia caused by Ceratium in South Africa. (Photo credit unknown)

An anoxic Ceratium bloom in South Africa killed 2000 tons of rock lobster and cost $50 million. (G. Pitcher)

Dead manatees on Sanibel Island, Florida, 1996. (Fish and Wildlife Research Institute (FWRI), Florida Fish and Wildlife Conservation Commission (FWC))

Dead fish from anoxia caused by Ceratium in South Africa. (G. Pitcher)

Dead fish from a Karenia brevis bloom in Texas. At high concentrations, toxins produced by this organism can cause massive fish kills. (Brazosports)

Dead fish and discolored water during a Florida red tide. (Fish and Wildlife Research Institute (FWRI), Florida Fish and Wildlife Conservation Commission (FWC)