red tide

noun

: seawater discolored by the presence of large numbers of dinoflagellates (as of the genera Karenia, Gymnodinium, and Alexandrium) which typically produce a toxin poisonous especially to many forms of marine vertebrate life and to humans who consume contaminated shellfish compare saxitoxin

Examples of red tide in a Sentence

Recent Examples on the Web

Resilient red tide Over the last decade, Tiernan says there’s been a spate of massive crabling returns–markedly increasing the population. —Lauren Leffer, Popular Science, 11 July 2024

Beyond the evacuations, the contaminated release triggered a toxic red tide outbreak that killed more than 600 tons of fish and other aquatic life in summer 2021 around the Tampa Bay area. —Curt Anderson, Sun Sentinel, 9 July 2024

Florida’s state wildlife and environmental agencies have ruled out exposure to red tide, water temperature and salinity. —Max Chesnes, Orlando Sentinel, 26 June 2024

The microscopic species Karenia brevis is responsible for most red tides, according to the Florida Fish and Wildlife Conservation Commission. —Kinsey Crowley, USA TODAY, 7 Mar. 2024

Word History

First Known Use

1904, in the meaning defined above

Kids Definition

red tide

noun

: seawater discolored and made poisonous by the presence of large numbers of dinoflagellates

Medical Definition

red tide

noun

: a large area of seawater discolored by the presence of large numbers of dinoflagellates (as of the genera Karenia, Gymnodinium, and Alexandrium) which typically produce toxins poisonous especially to many forms of vertebrate marine life and to humans who consume contaminated shellfish

In simple terms, a red tide is a dinoflagellate population explosion, caused when certain species "bloom," or multiply many times faster than usual.

—Ellen Girardeau

Red tides, the blooms of toxic Karenia brevis algae that appear almost every year in Florida, often lasting for months and turning the ocean red, may be dangerous to asthma sufferers—even if they don't go swimming.

—Nicholas Bakalar

see brevetoxin, saxitoxin, shellfish poisoning