red tide

American  

noun

1. a brownish-red discoloration of marine waters caused by the presence of enormous numbers of certain microscopic flagellates, especially the dinoflagellates, that often produce a potent neurotoxin that accumulates in the tissues of shellfish, making them poisonous when eaten by humans and other vertebrates.

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red tide British  

noun

1. 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

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red tide Scientific  

1. 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.

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Etymology

Origin of red tide

First recorded in 1900–05

Example Sentences

There was a weak El Niño earlier this year, and this wash-up coincided with the recent red tide and Santa Ana winds last week.

From Los Angeles Times • Nov. 21, 2024

Elsewhere, other threats continued, like collisions with boats and poisoning from red tide, a toxic algae.

From New York Times • Mar. 7, 2024

This behavior mirrors the natural processes at play when the dinoflagellates cause bioluminescence in the ocean during red tide events.

From Science Daily • Oct. 20, 2023

A red tide swept over Asia-session screens on Friday as markets took a hot Japanese inflation reading and the Bank of England's super-sized rate hike as bad news for growth.

From Reuters • Jun. 23, 2023

A red tide rose from the collar of his shirt and his shoulders crept up, like a kid expecting a cuff to the back of the head.

From "Anthem of a Reluctant Prophet" by Joanne Proulx