Red tide in Texas: an explanation of the phenomenon.




Texas A&M University, Sea Grant Program.

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Texas A&M University Sea Grant College Program.


Red tide is a natural phenomenon caused by tiny, single-celled marine organisms called dinoflagellates. Red tides have been around for millions of years. There seems to be a red tide recorded in the Bible. Of the more than 60 species of dinoflagellates, only 30 species produce a toxin. High concentrations of these toxins kill fish. The red tide-causing organisms are usually at rest on the ocean bottom; however, when conditions are right, the organisms suddenly bloom. Red tides can appear in small patches or long streamers. Red tide usually appears several miles off the coast at first, then tides and winds carry it into the beach and bay areas. Red tide kills large numbers of fish, rays, eels, and more. Shrimp and crabs are not affected as strongly as oysters, clams, and mussels. There is no major health concern for humans, as long as people do not eat oysters, clams, and mussels contaminated by the toxin. Various people in the Texas economy are hurt by red tides. Not enough is known about red tides to predict when one will occur or how to prevent one. Chemicals which kill red tide organisms are not dumped on the organisms because of the unknown impact on other marine life.


3 pages; available for download at the link below.


red tides, gonyaulax sp., Fish kill