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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
But a surge in deaths in recent years – much of which has been blamed on poor water quality, algae blooms, increasingly busier waters and red tide – has led officials to consider whether the manatee should again be considered endangered.
—
Christopher Cann, USA TODAY, 30 Dec. 2024
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.
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Karen Garcia, Los Angeles Times, 21 Nov. 2024
This wash-up coincided with the recent red tide and Santa Ana winds last week, but many variables could lead to these strandings.
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Ashley J. Dimella Fox News, Fox News, 20 Nov. 2024
Where Trump gained ground in Southern California A red tide washed through the once strongly liberal Pico-Robertson neighborhood in recent months.
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Ryan Fonseca, Los Angeles Times, 10 Dec. 2024
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Word History
First Known Use
1904, in the meaning defined above
Dictionary Entries Near red tide
Cite this Entry
“Red tide.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/red%20tide. Accessed 22 Feb. 2025.
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
More from Merriam-Webster on red tide
Britannica.com: Encyclopedia article about red tide
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