RED TIDE

discoloration of sea water caused by dinoflagellates (phylum Protozoa), during periodic blooms (or population increases). Toxic substances released by these organisms into the water may be lethal to fish and other marine life. Red tides, or red waters, occur worldwide in warm seas. Up to 50,000,000 individuals per litre (quart) of the species Gymnodinium brevis caused a red tide off the Florida coast in 1947 and turned the water from green to yellow to amber; thousands of fishes died. The red tide along the Northumberland coast in England in 1968 was the cause of the death of many sea birds. Similar red tides, caused by Gonyaulax polyedra, have occurred off the California and Portuguese coasts. Toxins released into the water are irritating to the human respiratory system; coastal resorts sometimes close when breaking waves release the toxic substances into the air.