Stay in the know about wildlife, water quality, and ecosystems on Sanibel and Captiva Islands and in Southwest Florida

Red Tide Persists and Intensifies

February 28, 2023

As Southwest Florida continues to rebuild in the wake of Hurricane Ian, a second natural disaster is slowing the path to economic recovery. Red tide remains high in the region, with bloom concentrations of over 100,000 cells/liter detected in seven counties, including high concentrations inshore and offshore of Lee and Collier Counties. Red tide alerts have been issued by the Florida Department of Health in Lee County on Sanibel, Captiva, Fort Myers Beach, and Boca Grande Pass.

“When red tide intensifies, it’s not only bad for wildlife and human health, but it is also bad for tourism. Sanibel is typically viewed as an escape from the overly developed cities of Fort Myers and Cape Coral,” said SCCF Research and Policy Associate Leah Reidenbach. “Although our beautiful island isn’t recovered, red tide is stymying our ability to bring back the tourism economy that many businesses on Sanibel and Captiva depend on.”

Persistent red tide has been blooming in the Gulf of Mexico since October, when it was exacerbated by nutrient pollution from Hurricane Ian.

“Naturally occurring K. brevis tends to bloom by feeding on upwellings of deep ocean nutrients that become mixed in warmer waters near the surface of the Gulf. However, when provided with a large supply of man-made nutrients such as nitrogen, the bloom can grow much larger than it otherwise would,” said SCCF Environmental Policy Director Matt DePaolis, adding that SCCF and the University of Florida recently published a study showing this connection.

The ongoing red tide bloom has resulted in frequent reports of mild to severe respiratory irritation and fish kills along beaches, and the public is urged to follow all beach closures and red tide advisories and avoid areas with active red tide blooms.

“Water managers must send more water south where it is needed, and more water storage and treatment in the Caloosahatchee watershed are absolutely necessary to buffer periods of high and low flows and reduce nutrient loading. Our islands’ economy and our future depend upon it,” Reidenbach said.

About Red Tide

Red tide results from a high concentration of Karenia brevis, a toxin-producing dinoflagellate (a type of single-celled organism). The resulting toxins can be harmful to pets and cause respiratory irritation in most people, with an elevated danger to people with respiratory conditions such as asthma.

Visit the Florida Fish and Wildlife Conservation Commission’s website for the most recent red tide data, and learn more on our red tide resources page.


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