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SCCF documents high concentrations of red tide

By SANIBEL-CAPTIVA CONSERVATION FOUNDATION 3 min read
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SANIBEL-CAPTIVA CONSERVATION FOUNDATION
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SANIBEL-CAPTIVA CONSERVATION FOUNDATION

The Sanibel-Captiva Conservation Foundation (SCCF) reported that onshore winds pushed a red tide bloom that has been offshore the islands for the last few months onto shore earlier this week.

On the evening of Jan. 26 and morning of Jan. 27, SCCF Marine Lab scientists found very high levels of Karenia brevis, the organism that causes red tide, at Algiers Beach and Tarpon Bay Road Beach.

“Our samples found more than 22 million cells per liter in the water just off the beach at both locations,” SCCF Research Associate Mark Thompson said.

Concentrations of over 1 million are considered high.

Karenia brevis is a single-celled organism belonging to a group of algae called dinoflagellates. Large concentrations of the organism, called blooms or “red tides,” can discolor water red to brown, giving it its name.

Karenia brevis produces brevetoxins, which may lead to adverse health impacts for humans and potentially fatal impacts for wildlife. The severity of the 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.

BLOOM BEGAN AFTER MILTON

The SCCF reported that the current red tide bloom started near Tampa Bay shortly after Hurricane Milton in October. It has been offshore and showing up in the satellite imagery for the last few months.

Samples collected along the beaches have been showing background concentrations during this time, even though the satellite images and reports from aerial photography showed the red tide west of Sanibel for the past month.

Satellite imagery, as well as aerial photography and video, shows that the bloom is large and stretches from Sanibel and Captiva to Naples.

LAB FOUND HIGH COUNTS OFFSHORE

Samples collected by the SCCF Marine Lab in early January confirmed the offshore presence of red tide in high concentrations.

“The runoff from recent rain events have provided additional nutrients which help sustain the bloom in the waters near the barrier islands,” Thompson said on Jan. 29. “The conditions of Sunday evening and Monday morning — with light onshore winds and no waves in the surf zone — caused it to become more concentrated along the shoreline leading to more potential adverse effects.”

The lab will continue to monitor the bloom and provide updates.

The SCCF has also received reports of dead fish from beachgoers. Those who see dead fish or experience any impacts from red tide are asked to email sccf@sccf.org.

In addition, report any fish kills to Florida Fish and Wildlife Conservation Commission at https://myfwc.com/research/saltwater/health/fish-kills-hotline/ or call 1-800-636-0511.