Red tide causes fish kills, respiratory irritation along Southwest Florida coast

A red tide that’s lingered along the Southwest Florida coast for months has some environmental groups worried the region may see a larger outbreak this summer or fall. 

Red tide is caused by the organism Karenia brevis, which is found naturally in the Gulf of Mexico at background levels. 

But concentrations can become deadly for marine wildlife when levels get too high, as they did during a particularly strong red tide that lasted from the fall of 2017 until the spring of 2019. 

In other news:Boaters' cleanup is latest citizen-led effort to help improve water quality

The summer of 2018 was the worst, with dead and decomposing fish, birds and turtles piled up along local beaches. 

And while conditions are nowhere near as potent as they were three years ago, the threat is always there.  

“I think the conditions are ripening with nutrients along the coastal waters, and that can contribute to red tide blooms becoming more frequent, severer or longer-lasting,” said Jennifer Hecker, with the Coastal and Heartland National Estuary Partnership in Charlotte County. “I think it’s possible we will see more in the coming months, given those things.” 

Red tides have been documented for hundreds of years, meaning they existed before modern humans had any ecological impact. 

But researchers from the University of Miami and other schools and laboratories say red tide blooms here are more frequent, longer-lasting and stronger than they were just 50 years ago due to agriculture runoff and urbanization. 

Southwest Florida coastal counties have seen varying degrees of the bloom over the past six months or so. 

Blooms typically start in late summer or early fall and are usually driven away by advancing cold fronts from the mainland in January and February. 

By the way:Researchers release playbook for combating red tide, other deadly algae

That didn’t happen this year, and the bloom could continue into the summer. 

Charlotte County was recently the focal point for high counts, after a front pushed the bloom from the Gulf of Mexico into Charlotte Harbor. 

“We’ve been seeing it in the Punta Gorda area as well,” Hecker said. “We’re seeing some fish accumulated, and I think part of that was from the wind we had from storm fronts that pushed it further into the harbor than we’re used to seeing.” 

The Florida Fish and Wildlife Conservation Commission is the state agency charged with monitoring red tide. 

The agency posts daily updates online as a public safety precaution. 

Red tide can cause respiratory irritation in humans, especially for people who have existing medical challenges. 

Conditions in south Lee County have ranged from normal background concentrations to medium concentrations, according to FWC records. 

Counts have been similar in Collier County, although most of the bloom is north of the Naples area. 

“Although our most recent sample results (from April 22) showed not present to medium concentrations of red tide at the beaches, we have not gotten reports of any dead fish or respiratory irritation,” said Rhonda Watkins, principal environmental specialist for Collier County. “Winds have been mostly offshore since last week so that would reduce the potential for people to feel red tide at the beach.” 

Watkins said people should still be cautious when visiting beaches. 

“We are still recommending that people who have chronic respiratory issues avoid the beach as respiratory irritation is possible at all of our beaches when winds are blowing onshore,” she said.

In 2020:Researchers warn red tide is back in Southwest Florida

In 2019:Lingering red tide gaining strength, killing sea turtles

In 2018:Red tide suspected as dead dolphins wash up

In 2017:Red tide spreads out, lingers along coast

The blooms typically initiate off Sarasota and work their way south toward Lee, Collier and the Everglades. 

Stephannie Kettle, with MOTE Marine Laboratory and Aquarium in Sarasota, described conditions as patchy. 

“Last week we had some respiratory (issues reported) and dead fish at Siesta (Key),” Kettle said. “Last week the wind was blowing it onto the beach, but we looked this morning and there was no irritation or dead fish reported. With winds and currents, the bloom can move around and be pretty patchy. So Lido (Key) has a little irritation today but Siesta doesn’t.” 

She said this bloom has been much weaker and, overall, more like a typical outbreak than some of the devastating ones in recent memory. 

“If people are remembering the 2018 bloom, we’re not there,” Kettle said. “The cell counts are much lower, and it’s more patchy and not as severe. This is more of a normal red tide versus what we saw in 2018.” 

Connect with this reporter: @ChadEugene on Twitter.