Stay in the know about wildlife, water quality, and ecosystems on Sanibel and Captiva Islands and in Southwest Florida
Red Tide No Longer Present Off Lee County
A red tide bloom that has been causing impacts to wildlife and people in Southwest Florida since mid-January is no longer being detected in Lee County, according to recent water samples and satellite imagery.
Water samples taken and analyzed by the SCCF Marine Laboratory on Sanibel and Captiva over the last 10 days did not find any Karenia brevis, the organism that causes red tide. On Feb. 19, the Lee County Department of Health lifted its red tide alerts for Tarpon Bay Beach and Bowman’s Beach.
“Though there could be Karenia away from shore and deeper, it’s likely the bloom crashed,” said Marine Lab Research Scientist Rick Bartleson, Ph.D.
Concentrations of the red tide organism (Karenia brevis) were listed as “not present” in all water samples from offshore Lee County between Feb. 14-21, according to the most recent Florida Fish & Wildlife Conservation Commission (FWC) report. High and medium concentrations were still found in Sarasota County and Monroe County, respectively, though more recent samplings from Feb. 24 show only low concentrations in Manatee County.
Feb. 21 FWC Red Tide Status Update
- Pinellas County: Background to very low concentrations
- Hillsborough County: Very low to low concentrations
- Manatee County: Background to low concentrations
- Sarasota County: Background to high concentrations
- Charlotte County: Background to low concentrations
- Lee County: Not present
- Collier County: Background concentrations
- Monroe County: Background to medium concentrations
Despite the bloom disappearing, SCCF continues to document and receive reports of fish kills and other stranded coastal wildlife, including birds and sea turtles.
“This is likely because red tide toxins (brevetoxins) accumulate in the tissues of small fish and invertebrates, which are then ingested by wildlife higher in the food chain,” Bartleson said. “Toxins from dead Karenia cells can also contaminate sediments and be absorbed by seagrasses, which can remain toxic to marine life after a red tide has passed.”
Since December 2024, the Caloosahatchee Estuary has been receiving scheduled Lake Okeechobee releases within the optimum flow envelope as part of Lake Okeechobee Recovery Operations. SCCF staff and partners have provided regular updates and recommendations to water managers and decision makers through our Caloosahatchee Conditions Reports.
About Red Tide
Karenia brevis is a single-celled organism belonging to a group of algae called dinoflagellates. Large concentrations of this organism can discolor water red to brown, giving ‘red tide’ its name.
K. brevis produces brevetoxins, which may lead to adverse health impacts for humans and potentially fatal impacts for wildlife. The severity of these impacts depends on the concentration of K. brevis cells per liter of water, with impacts to humans and wildlife becoming likely at concentrations of 10,000 and above.
While red tide occurs naturally, human activities such as the introduction of excess nutrients into waterways via watershed runoff and Lake Okeechobee releases can intensify an existing bloom.
SCCF continually monitors regional water conditions — sign up for our Weekly Water Conditions Tracker to stay informed.