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

This red tide is extremely patchy, and many areas will not experience a problem even with an onshore wind. —Josh Hammer, Newsweek, 3 Dec. 2024

After Hurricane Milton made landfall in Sarasota, satellites began to detect significant levels of chlorophyll, which can trigger red tide events. —Greg Wehner, Fox News, 21 Oct. 2024

On a night when Republicans swept races around the country, Baldwin bucked the red tide by eking out a narrow win over GOP challenger Eric Hovde to secure a third term in the U.S. Senate. —Daniel Bice, Journal Sentinel, 6 Nov. 2024

Along with a rise in life-threatening bacteria, FOX 13 reported that scientists are monitoring for a rise in Karenia brevis, also known as the algae that produces red tide, along the Gulf Coast. —Greg Wehner, Fox News, 21 Oct. 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