Red tide patches move along Southwest Florida coast

Karl Schneider
Fort Myers News-Press

Sporadic reports of fish kills and respiratory irritation point to patches of red tide off the coast of Southwest Florida, aligning with data researchers have collected this week.

Dead fish spotted were at Bonita Beach Friday morning and high counts of red tide, caused by the organism Karenia brevis, were reported along Sanibel earlier this week.

“It hasn’t looked good for most of the week,” said Rick Bartleson, research scientist with the Sanibel-Captiva Conservation Foundation. “It started out pretty bad on Monday with about 20 million cells per liter, a significant jump from last week so I started increasing sampling.”

Dead fish are seen on Bonita Beach on Barefoot Beach south of the Bonita Beach parking area on Friday, December 18, 2020. Red tide has been documented in the area.

The Florida Fish and Wildlife Conservation Commission deems anything greater than 1 million cells per liter to be high with respiratory irritation and probable fish kills anticipated.

FWC data confirms Bartleson’s observations showing a Dec. 14 sample at Redfish Pass near Pine Island Sound with high concentrations.

“Almost all of our samples this week have had high samples,” Bartleson said.

More:Researchers warn red tide is back in Southwest Florida

Red tide was also reported southward all the way to South Marco Beach on Marco Island, according to FWC data. High concentrations were recorded offshore about 16 miles from Doctors Pass.

Mike Parsons, FGCU professor and director of its Vester Field Station in Bonita Springs, said his team started noticing red tide offshore around Thanksgiving.

“Offshore we did not see any dead fish but we noticed them near shore,” he said. “We collected some for toxin analysis and other experiments.”

Parsons said they’ve been collecting samples about 75 miles offshore and are still looking at a lot of them. The highest concentrations he and his team found were about 2 million cells per liter at a 10-foot depth. He said it’s been patchy and that Karenia brevis may be looking for its “happy zone” in terms of the right amount of light and nutrients.

“We’re still learning about how if you have this one patch or one bloom, maybe a swarm you could call it, does it move around and spread or grow,” he said.

More:Exposed to red tide? Scientists seek volunteers to learn long-term health effects

North winds have moved red tide south, but Southwest Florida does not get cold enough to kill off the Karenia brevis. And even with the understanding that winds move the blooms, they’re still hard to predict.

Dead fish are seen spread out on Bonita Beach on Thursday, December 17, 2020. Red tide is present in the area.

“The problem with predicting is that north winds give us upwelling and bring water from offshore —that’s what caused this bloom to begin with,” Bartleson said. “We don’t know what’s coming to us from offshore.”

Friday afternoon, most beaches on Sanibel had low Karenia concentrations, Bartleson said.

"And they had some nice, big diatoms, so maybe a different water mass came in with the tide," he said.

Rhonda Watkins, Collier County's principal environmental specialist, shared data from Dec. 16 showing low to medium levels of red tide along the county's beaches. 

The Beach Conditions Report (visitbeaches.org) or the Red Tide Respiratory Forecast (habforecast.gcoos.org) can be used for those sensitive to red tide prior to heading to the beach, county spokeswoman Connie Deane wrote in an email to the Daily News.

"People with chronic respiratory illnesses such as asthma or emphysema should avoid going to the beach when red tide is at the beach," she wrote.

Collier's Coastal Zone Management staff members have cleaning equipment used to remove debris, such as dead fish, from the beach.

"If the numbers of dead fish reach levels that present a public health emergency, we have a contractor available to assist in a removal operation," Deane wrote. "The numbers of fish on the beach the last several days have not approached a level considered to be an emergency."

And while beachgoers may run into red tide on the shore, Parsons said it’s possible to move a half mile down the beach and find a better spot.

“If you’re breathing in toxins, especially with breathing issues, you have to be careful,” he said. “The best thing to do is look at beach condition reports.”

More:U.S. House passes bill to improve forecasting of harmful algal blooms

Karl Schneider is an environment reporter. Send tips and comments to kschneider@gannett.com. Follow on Twitter @karlstartswithk