PUNTA GORDA, Fla., Jan. 8 (UPI) -- Like winter turns into spring, Florida's toxic red tide -- lethal to marine life and harmful to tourism -- is sure to return, although no one can say precisely when.
Scientists and fishermen have observed the infestation for decades, and there's little likelihood it will be eliminated in the foreseeable future. Efforts are ongoing, though, to wipe out this aquatic menace.
"I've hated red tide since the '70s," said Ralph Allen, a fisherman and owner of the King Fisher Fleet of tourist excursion boats in southwest Florida. "Red tide is hard on my business and hard on me personally. But I'm not sure why it happens or if there's a natural reason for it."
The federal government estimates that red tide causes an average of $82 million annually in losses to the economy, with $20 million of that from diminished tourism -- mostly in Florida. While red tide usually occurs in the last half of the year, it does not appear every year -- at least not at a scale that would cause significant disruption to people's lives.
Red tide refers to algae blooms that occur in the Gulf of Mexico, and it can be a problem at any time of year. The algae release toxins in the air and water that can kill fish and marine animals.
During a red tide event, tourists, business owners and local residents often confront a one-two punch of respiratory irritation, such as an allergy attack and the odor of dead fish rotting in local harbors.
"Some people say they can smell red tide, but I can't. I know it's there when I feel it in my throat, eyes and nose -- just an irritation at first," fisherman Allen said.
Fishing becomes impossible in some places, although fish can congregate away from the toxic tide and make the sport more productive in other areas.
Hotel and restaurant owners often see a sudden drop in business as word of the bad odor and irritation spreads, often on social media. Local residents must either stay indoors or endure the odors and toxic air.
But red tide most severely impacts people who have chronic respiratory or kidney problems. For them, the toxins can be life-threatening, according to doctors and the U.S. Centers for Disease Control and Prevention.
Despite its name, red tide usually is not red. Most of the time, it is not visible. When it is seen, it often appears as brownish hazy streaks in the water. Red tones only appear during the most extreme outbreaks -- such as when winds have pushed large amounts of algae into a small cove or inlet.
A native problem
Red tide algae -- Karenia brevis -- always is present in low concentrations, according to University of Florida researchers. The longest duration for a red tide bloom was 30 months from 1994 to 1997, according to a report from the university and Florida Sea Grant, a university-based program that promotes conservation of coastal resources.
Red tide occurs in other parts of the world, but the worst and most regular events in the United States happen in Florida. The area impacted most frequently stretches from Tampa to Naples -- about 170 miles of coastline that features some of Florida's most popular beaches.
Since a severe red tide outbreak in 2018, Florida has launched new research efforts funded by tens of millions of state dollars, while federal funding also has ramped up. Red tide in 2019 was scattered and less damaging, and by the end of December, all signs of it had disappeared from the state's monitoring map.
Despite accounts of red tide dating to the 1800s, it is poorly understood.
"Red tide is hard to predict. It is patchy and it changes from day to day," said Betty Staugler, a marine biologist with Florida Sea Grant.
What is known, Staugler said, is that the algae feed on nutrients like nitrogen and phosphorus from lakes and streams, or from the sea floor. The most common sources of land-based nutrients are fertilizers, soil runoff and sewage.
These same nutrients also fuel toxic blue-green algae, which is more deadly. Blue-green algae problems in Florida are centered in Lake Okeechobee and the southeast region, but can occur statewide.
During a severe red tide outbreak in 2018, county governments reported removing thousands of rotting dead fish that had floated onto beaches and into harbors. Since then, Staugler and others have answered many questions from concerned tourists and property owners about why the phenomenon occurs, why it seems have been worse in recent years and whether it follows hurricanes.
Staugler said Hurricane Irma in 2017 might have caused a severe outbreak because the storm churned up the near-shore waters in the Gulf for months. But scientists still "don't specifically know what role, if any, this played," she said.
Healthcare costs soar
Health problems associated with harmful algae cost the nation $22 million annually, according to a report from the University of Florida.
The report said treatment of respiratory illness in Sarasota County, halfway between Tampa and Fort Myers, during red tide in 2015 and 2016 resulted in up to $4 million in medical bills. Calls to the Florida Poison Control Center due to red tide more than tripled between 2017 and 2018.
The Florida Department of Health advises that people with respiratory conditions like asthma avoid red tide. The most severe exposure can result in liver or kidney damage, according to the CDC.
Paul Simeri, a Michigan resident who spends winters in southwest Florida, said he's had kidney problems and he knows about red tide health warnings. His winter home in Burnt Store Marina, 13 miles south of Punta Gorda, had a red tide episode in the fall that included a fish kill.
"My eyes were burning and I was coughing. For a couple of days it was so bad, I couldn't go out for long," he said.
News reports about red tide in 2018 made it seem like all of southwest Florida was experiencing a crisis, even on days when red tide was absent, said Frank Hommema Jr., a fisherman and businessman in Port Charlotte.
"Red tide has been bad before, but now everyone posts photos of dead fish on social media and it becomes a big scare," Hommema said.
Property values along the Gulf beaches are impacted by severe blooms that last a long time, said Brian Ziegler, 37, a lifelong resident of the Charlotte Harbor area and a Realtor.
A 2015 report from the Florida Realtors trade association said algae blooms dented those values in the Fort Myers area by an estimated $541 million annually and in Martin County, about 30 miles north of West Palm Beach, by an estimated $428 million annually.
For some, the red tide threat isn't enough to keep them away.
Patricia Trefry of Westport, Ontario, said she and her husband came to the Punta Gorda area despite seeing the red tide warnings in mid-December. They are seasonal visitors who live on their boat.
"A lot of people are wondering where to go or how bad it is," Trefry said. "People at the docks say, 'I'm coughing, maybe it's red tide.' But we're determined to enjoy ourselves -- and we love it here."