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

Keeping an Eye on Red Tide in SWFL

October 30, 2024
Red Tide Satellite Imagery 10.30.24

The Florida Fish and Wildlife Conservation Commission (FWC) reported on Oct. 25 that the red tide organism, Karenia brevis, was found in background to high concentrations in 49 samples offshore of Southwest Florida.


What Is Red Tide?
Red tide — a harmful algal bloom caused by the organism Karenia brevis — can develop or intensify due to multiple factors: Wind, ocean currents, or upwellings of nutrient-rich water from powerful storms. Once a red tide bloom is present, polluted watershed runoff or Lake Okeechobee releases can lead to intensification. Red tide can have massive impacts on our ecosystems, communities, and economies.


In Lee County, data from the NOAA National Center for Coastal Ocean Science (NCCOS) and the FWC indicate multiple offshore samples with very low to medium red tide concentrations.

FWC Red Tide Current Status >>

The SCCF Marine Laboratory‘s samples from the beach on Sanibel on Oct. 29 and Oct. 30 did not detect K. brevis.

“The dynamics of this event are hard to predict,” said SCCF Marine Laboratory Director Eric Milbrandt, Ph.D. “Over the last week the bloom seems to have gone from larger and higher counts around Tampa and where Hurricane Milton made landfall in the Sarasota area, to being transported south, and now it seems to be moderating and getting smaller.”

Fish kills have been reported along Boca Grande and on Manasota Key, but could be concentrated cases, Milbrandt said.

“We don’t know if it’s going to get worse or going to get better. The possibility of fish kills and wildlife in distress, that’s certainly something we’re watching out for,” he said. “Otherwise we are in wait-and-see mode.”

Wildlife Impacts Reveal Red Tide’s Persistence >>

K. brevis cells release a toxin that attacks the nervous system of animals. These neurotoxins, called brevetoxins, are often fatal to fish, birds, sea turtles and marine mammals and can have adverse impacts in humans. Report wildlife behaving erratically (unable to stand or fly, displaying tremors, apparent weakness or confusion) to Sanibel’s Clinic for the Rehabilitation of Wildlife (CROW), where treatment can be administered by calling the CROW Wildlife Hospital at 239-472-3644 ext. #222.

Although Lake Okeechobee releases to the west coast of Florida began on Saturday, Oct. 26, average flows to the Caloosahatchee remain in the optimum range for estuarine health. If the red tide bloom does intensify, SCCF will advocate for no stressful or damaging flows (>2,100 cubic feet per second at the W.P. Franklin Lock and Dam) from Lake Okeechobee.

Subscribe to SCCF’s Weekly Water Conditions Updates.

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