Only trace amounts of the red tide organism, Karenia brevis, have been detected in Florida waters, the Florida Fish and Wildlife Conservation Commission reports.

SARASOTA — A Florida red tide bloom that began in September has subsided, the Florida Fish and Wildlife Conservation Commission reports.

For now, it’s all gone.

Florida residents were concerned about a comeback of the poisonous algae that lasted from 2017-2019 and that stretched from Pinellas County to Monroe County. It killed generations of fish and hundreds of Florida’s beloved manatees, sea turtles and dolphins.

This year’s red tide was typical of a "normal" red tide year, experts say.

Historically, red tide can develop from August to December and disappears in the cool winter months, from December to March. A bloom persisting past December can occur, especially when the average temperature is above normal, as it has been the past several months.

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Recent water samples tested by the Florida Fish and Wildlife Conservation Commission found that bloom conditions no longer exist from Marco Island to Venice, where the red tide organism resurfaced beginning in August. It grew to bloom conditions from September-November before quickly dwindling in December.

A series of cold fronts helped chill Southwest Florida waters, making them less hospitable for red tide cells, which thrive between 60 and 86 degrees, experts say.

Currently, the Beach Conditions Reporting System shows no respiratory irritation, moderate water color, and 68-degree water temperatures at beaches along the west coast of Florida.

Water temperatures on the East Coast of Florida are around 77 degrees.

This year, there have been 19 manatee deaths attributed to the recent red tide bloom, FWC reports. All of the deaths occurred from Englewood to Marco Island. However, 574 manatees died in 2019 from cold stress, human activities and other undetermined conditions.

Long term

Rick Bartleson, a research scientist at Sanibel-Captiva Conservation Foundation, said his nonprofit group, which monitors coastal habitats and aquatic resources, detected a 100-square-mile dead zone near Sanibel Island in August 2018. It created blackwater at the south end of Boca Grande.

He said low-oxygen conditions were found in the bottom 12 feet of water, and the area was in recovery until red tide returned.

"It takes a long time to come back from it," Bartleson said. "There were things that were dead down there, like giant horse conchs, all the corals, and things that couldn't swim away; they’re gone for a long time. … It could take 30 years for some of those whelks to come back again. Those are the things the sea turtles, loggerheads and Kemp’s ridleys would eat.

"It's a big long-term problem now."