red tide

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.

red tide

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

red tide

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.

Word History and Origins

Origin of red tide¹

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

“I did notice that the ocean was really red-brown last week, but I didn’t put it together that the smell was linked to the red tide,” she said.

From Los Angeles Times

During the day, those dinoflagellates cast a rusty hue across the ocean — often called a “red tide” — which sky cameras on Tuesday captured around the Santa Monica Pier.

From Los Angeles Times

Sawfish necropsies have not revealed any pathogen or bacterial infections, nor problems with low water oxygen levels or contaminants such as chemicals, or toxic red tide.

From Seattle Times

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

From New York Times