9 things to know about red tide in Florida

ORLANDO, Fla. — Red tide is returning to Florida beaches.

Here are 9 things you need to know about red tide, according to the Florida Fish and Wildlife Conservation Commission:


1. A red tide, or harmful algal bloom, is a higher-than-normal concentration of a microscopic alga. In Florida and the Gulf of Mexico, the species that causes most red tides is Karenia brevis, often abbreviated as K. brevis.

2. At high enough concentrations, red tide can discolor water a red or brown hue. Blooms caused by other algal species can appear red, brown, green or even purple. The water can also remain its normal color during a bloom.

SEE: 9 things to know about red tide in Florida

Read: Red tide guide: How to check Florida beach conditions

3. Red tides can last as little as a few weeks or longer than a year.

4. Many algae species cause red tides all over the world. But the organism that causes Florida’s red tide, Karenia brevis, is found almost exclusively in the Gulf of Mexico and occurs from Mexico to Florida.

5. K. brevis can be transported around the Gulf of Mexico as coastal waters move with winds and currents. Some red tides have even been carried by the Gulf Stream current into the Atlantic Ocean as far north as Delaware.

Read: ‘A lot of dead fish’: Beach visitors in Southwest Florida deal with red tide conditions

6. Although the occurrence of a red tide cannot be predicted, scientists can forecast its movement using wind and water current data once a bloom is located.

7. Many red tides produce toxic chemicals affecting both marine organisms and humans.

8. Some people experience respiratory irritation, such as coughing, sneezing, tearing and an itchy throat, when red tide is present and winds blow onshore.

Read: ‘Huge’ bloom of seaweed looms in the Atlantic, likely headed to Florida beaches

9. FWC advises people not to swim in or around red tide because the toxin can cause skin irritation, rashes, burning and sore eyes.

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Sarah Wilson

Sarah Wilson, WFTV.com

Sarah Wilson joined WFTV Channel 9 in 2018 as a digital producer after working as an award-winning newspaper reporter for nearly a decade in various communities across Central Florida.