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

Some Red Tide Impacts Begin Showing Up on Islands

January 14, 2025
deceased eel on shore of sanibel

A deceased moray eel on Sanibel on Jan. 13, 2025

Local concentrations of Karenia brevis, the organism that causes red tide, have begun trending upward in Southwest Florida over the past week, along with impacts to coastal wildlife on Sanibel and Captiva.

The most recent data from the Florida Fish and Wildlife Conservation Commission detected K. brevis at background, very low, and low concentrations in Lee County, with medium concentrations recorded offshore of Sanibel and at Alison Hagerup Beach Park.

Multiple instances of wildlife impacts have been reported on the islands, potentially linked to the presence of K. brevis. These include strandings of various fish species (including mullet and catfish), crabs, eels, and two black scoters found deceased on the shore.

“While determining the cause of death for wildlife is difficult to prove without individual examination, the close proximity of K. brevis provides reason to believe these impacts are correlated to the existing red tide bloom,” said SCCF Policy Associate Allie Pecenka. 

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. Even when K. brevis cell counts read as ‘not present’ or ‘background concentrations,’ animals may still experience brevetoxicosis (red tide poisoning) symptoms due to foraging offshore where a bloom is active. Toxins can also bioaccumulate in prey and plants that are eaten by larger animals such as cormorants and sea turtles.

Read more about red tide and wildlife >>

Current satellite imagery suggests the bloom contains a patch located southwest of Sanibel Island and offshore of Naples.

“Impacts of the red tide bloom will likely be seen during south and westerly winds because of the onshore transport of the bloom patches,” said SCCF Marine Lab Director Eric Milbrandt, Ph.D. “While there is an uptick in strandings this past week, the largest detectable patch from satellite imagery is 15-20 miles offshore and south of Sanibel.”

The distribution of the bloom can change daily due to wind and currents, he added.

If you notice deceased wildlife, fish kills, or experience respiratory impacts potentially linked to red tide, please email sccf@sccf.org with details including the location, date and photos of wildlife impacts. 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.

The National Centers for Coastal Ocean Science (NCCOS) reported that water samples from Jan. 6 to Jan. 13 detected K. brevis along the coast at levels that pose a respiratory irritation risk in Charlotte, Lee, manatee, Monroe, Pinellas, and Sarasota counties.

SCCF will continue to monitor this situation closely while using our local water quality reports to advocate for strategies to best support our coastal ecosystems and communities.  

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