red tide n seawater discolored by the presence of large numbers of dinoflagellates esp. of the genera Gonyaulax and Gymnodinium which produce a toxin poisonous esp. to many forms of marine vertebrate life and to humans who consume contaminated shellfish see PARALYTIC SHELLFISH POISONING compare SAXITOXIN
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a tremendous overabundance of protozoa of the phylum Dinoflagellata in ocean waters, giving them a red tint; some species simply deplete oxygen in the water, but many species contain neurotoxins that can kill fish and other marine life and cause shellfish poisoning (q.v.) in humans who eat contaminated seafood.Medical dictionary. 2011.