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A bloom of plankton, especially dinoflagellates, that causes a usually reddish discoloration of coastal ocean waters. Certain dinoflagellates produce toxins that contaminate shellfish, making them unsafe to eat, and can kill fish.
(Environmental Science) a discoloration of sea water caused by an explosive growth in phytoplankton density: sometimes toxic to fish life and, through accumulation in shellfish, to humans
a brownish red discoloration of marine waters caused by a huge aggregation of flagellates, esp. dinoflagellates, that often produce a potent neurotoxin that contaminates shellfish.
A population explosion of certain species of dinoflagellates, a kind of protozoan found in plankton. The dinoflagellates color the water red or reddish-brown, and secrete a toxin that kills fish. Red tide usually occurs in warm coastal waters.