WEST PALM BEACH, Fla. (CN) - Toxic red algae blooms in Florida have spread to metropolitan counties on the state's east coast, triggering large-scale beach closures and fears of a plunge in the tourist economy.
The blooms, known as red tide, release toxins notorious for killing marine life and causing respiratory irritation in beachgoers. Vast stretches of southeast Florida shoreline were shuttered this week after visitors complained of burning eyes and coughing attributable to exposure to the algae. The algal toxins are airborne, so standing on the beach is enough to generate symptoms.
Water test results released Thursday confirmed that the red tide stretched down to Florida's most populous county, Miami-Dade. To the north, Palm Beach shorelines were reopened to the public Friday after remaining closed all week.
The red tide contamination is the highest measured on the southeast Florida coast in 15 years, according to data from the Florida Fish and Wildlife Conservation Commission.
Though Florida's east coast hasn't seen a red tide bloom this severe in a long while, the algae -- Karenia brevis -- has been wreaking havoc on the Gulf coast (west side) of Florida since the fall of 2017. The smell of washed-up fish poisoned by the algae has become an all-too-familiar odor there in recent months. The National Oceanic and Atmospheric Administration reports that more than sixty dolphins have been stranded since July.
In a mid-summer survey by the tourism department in Sarasota County, most of the 40 respondents said their revenue was down at least 25 percent year-over-year.
Christina Brown, a Lee County hotel manager, said in an interview Friday that at the height of the blooms in her area, she and her coworkers helped scrape the rotting marine life off the beach because local cleanup crews had trouble keeping up with the never-ending streams of fish washing ashore.
"There were dead eels, fish: piles and piles that just kept coming. Out there in the water, you'd be surrounded by dead fish," Brown said.
She said the situation has since improved on the beaches around her hotel. The hotel currently has a high occupancy rate, she said.
With the red tide now present on the east coast -- in Florida's three most populated counties -- beachside restaurants and hotels fear they'll face the same devastation suffered on the Gulf. The Florida Fish and Wildlife Conservation Commission noted in a public statement that east coast red tide blooms are "typically of shorter duration than those on the Gulf coast."
What's causing the unusually widespread toxic algae growth is up for debate.
Red tide presents as a natural phenomenon all over the world.
But some scientists believe the blooms in Florida have been fed by nutrients from agricultural and septic tank runoff.
"We can't prove it. But it certainly makes sense," coastal researcher and ecologist Stephen Leatherman said in an interview. "Any nutrients that can feed it would be a problem. The red tide is natural. But we think it may be worse because of excess man-made nutrient [sources]."
One heavy source of nutrient-rich outflow is Lake Okeechobee, one of the largest freshwater lakes in the country. It's heavily polluted by runoff from from cattle and dairy farms, sugar production and other agricultural activities.
The Army Corps of Engineers periodically releases massive flows of water from the lake in order to prevent its aging dike from breaking and causing catastrophic flooding. The controversial practice sends polluted, nutrient-laden water through Florida's Caloosahatchee and St. Lucie River systems, which lead towards the open sea on opposite sides of the state.
This outflow of Lake Okeechobee water is linked closely to the estuary growth of blue-green algae, another toxic microorganism that has been plaguing Florida. However, Leatherman said more research is needed to determine the extent to which the pollution fuels red tide algae.
The Conservation Commission says the red tide develops offshore, away from man-made nutrient sources. Scientists theorize that the persistent bout of it in Florida could be related to Hurricane Irma's churning of water in the Gulf of Mexico, which caused upwelling of nutrients from the bottom of the Gulf.
"Red tides occurred in Florida long before human settlement, and severe red tides were observed in the mid-1900s before the state’s coastlines were heavily developed. However, once red tides are transported inshore, they are capable of using man-made nutrients for their growth," the commission's web site states.
Leatherman said that as fall brings lower temperatures, Floridians may see some relief. The cooler weather slows red tide growth, he said.
"But you still have these strong onshore winds. The algae is out in the Gulf Stream, and the winds are just blowing it in here. That's the bad news," Leatherman said.
Florida Gov. Rick Scott in August declared a state of emergency across several west coast counties due to the red tide. Affected businesses are eligible for special low-interest loans and other assistance to help them cope with financial losses.
Leatherman said the arrival of the red tide in the more densely populated counties of Miami, Broward and Palm Beach was confirmed just this week, so it's too early to tell whether these areas will face the same long-lasting blooms experienced on the Gulf side.
"The jury is still out," Leatherman said.
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