Red tide experts: latest bloom an example of longer-lasting, stronger blooms

Chad Gillis
Fort Myers News-Press

An intense and widespread red tide, that seemed to go away after Hurricane Ida, now stretches from the Panhandle to Charlotte County; and with red tide blooms being stronger than they were just 50 years ago, summer blooms may become more common. 

Although red tide (Karenia brevis) season is October to February, blooms are possible during the hotter summer months. 

Some scientists say although red tide naturally occurs in the eastern Gulf of Mexico, modern blooms are not natural as they're fed by man-made nutrient sources like farming and urban development. 

"They’re more prevalent in the late summer and fall but we’ve had red tide for any month of the year," said Larry Brand, a professor and researcher at the University of Miami. "Some years we get essentially no red tide, although it’s getting more and more rare. And we don’t really understand that." 

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Summer red tides have been recorded for several decades, and some blooms have lasted for more than a year. 

"I argue it’s because of nutrients from land-based runoff with our rainy season," Brand said. "Last fall (the U.S. Army Corps of Engineers) released water from Lake Okeechobee, and there was soon red tide at the mouth of the Caloosahatchee." 

This bloom has lingered for almost a year, at times being very intense. 

Fish kills and breathing irritation in humans can occur when levels reach 100,000 cells per liter. Measurements over the past year along the west coast of Florida have been at 1 million cells per liter and higher. 

FWC's latest report shows high concentrations in Clearwater and off Charlotte County. 

An anglers jumps a tarpon in the Tampa Bay area, where a recent red tide bloom has regained strength.

One million cells per liter is the top of the scale for the Florida Fish and Wildlife Conservation Commission, although counts can get to 100 million and higher. 

Brand says excess nutrients are the cause of the longer-lasting and stronger blooms. 

"You saw that with Piney Point," Brand said "Go back 50 years, in general they’re tending to last longer and they’re more overall abundant. To get more abundant red tide you have to have more nutrients."

In March, a leak sprung at the Piney Point phosphate mine and fertilizer plant, sending pollution into the nearby waterway. 

Brand said that injection of nutrients has helped feed the red tide bloom off Manatee County, which has been the center-point of the recent bloom. 

The average abundance of red tide here is 15-fold what it was 50 years ago, Brand said. 

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"What has happened has been a tremendous increase in population growth," Brand said. "(The blooms) are getting denser than they used to be and that’s because of more nutrients. If I want to grown more algae I need more nutrients. There's not question about that." 

Chris Simoniello, with a research scientist at Texas A&M who is also with the Gulf of Mexico Coastal Ocean Observing System, recently helped develop a website that gives red tide updates every three hours. 

"We're monitoring Clearwater south to Sarasota, and the last few weeks were pretty intense, Simoniello said. "You'd look at the map and think it wasn't going to be so bad but then you'd get back from the beach and see the orange and red." 

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While FWC's report shows average conditions over an eight-day period, the Coastal Ocean Observing System updates upwards of eight times a day. 

"It's very low in the panhandle," she said. "And it's moderate to high at south end of Tampa Bay, and south of there is in the blue." 

Blue is the color used when only normal, background traces are found. 

Jim Beever, a retired biologist and expert in climate change planning, said red tides have occurred in summers before, that the overall phenomena is nothing new. 

"There was one off the panhandle in 1947," Beever said. "In 1994 to 1995 there was a two-year red tide bloom eclipsing the 40-year record for sustained episodes. Then in 1996 after a brief respite, red tide returns to the Gulf again in January, and within a month extends from Pinellas County nearly to Key West." 

Beever agreed with Brand, saying that red tides are stronger than they were a half-century ago, and that humans are to blame. 

"More frequent, intense, and longer blooms have occurred in the Lee County area with mismanagement of Lake Okeechobee flow releases," Beever said. "And do not forget that the watersheds of Glades and Hendry Counties also contribute more nutrients as more land was converted from native habitat and range to other land uses."

Connect with this reporter: @ChadEugene on Twitter.