Biomes, Ecological Cycles, and Environmental Milestones

What is red tide and what causes it?

Red tide is a term used for a brownish or reddish discoloration occurring in ocean, river, or lake water. It is caused by the rapid reproduction of a variety of toxic organisms, especially the toxic red dinoflagellates, which are members of the genera Gymnodidium and Gonyaulax. Some red tides are harmless, but millions of fish may be killed during a “bloom,” as the buildup is called. Other red tides can poison shellfish and the birds or humans who eat the contaminated food. Scientists do not fully understand why the “bloom” occurs.


This is a web preview of the "The Handy Science Answer Book" app. Many features only work on your mobile device. If you like what you see, we hope you will consider buying. Get the App