The Florida Department of Health in Charlotte County has issued a health advisory about toxic blue-green algae showing up east of Rotunda, in Zephyr Waterway near South Gulf Cove, warning people to stay away from the noxious algae bloom.
Microscopic parts of the harmful bloom can make adults sick. Children, too, need to stay away from the dangerous water. Dogs and cats can die.
Toxic blue-green algae have been found in the inland portions of the Peace River off and on for weeks, as the worst drought in 25 years has parched Southwest Florida.
“It’s nice and warm and sunny. They like the warm temperatures, they like the low flow, and they like to multiply,” said Barry Rosen, a leading expert on algae and cyanobacteria based at The Water School at Florida Gulf Coast University. “They love being in a stationary environment like lakes and canals.”
Rosen is a professor at FGCU’s Department of Ecology & Environmental Studies who has been studying freshwater bacteria for several decades with a focus on Lake Okeechobee and the Caloosahatchee River.
He said blue-green algae have it good right now because they like things calm and warm. The scattered showers that fell on the region earlier this month did little to quench the drought, but it did rain enough to wash in all of the nutrients, like fertilizers, that had been on the land for a while.
“It was like a steak dinner to them,” he said. “It’s prime time now, until the rainy season.”
That’s when the clumps of blue-green algae like those being seen right now in the Matlacha area will be broken up and washed away.
Blue-green algae are rather common in Florida waters. Given the right conditions, the cyanobacteria at the heart of the algae will bloom and turn into nasty-smelling, floating mats of scum colored blue and green, sometimes with a white foam wrapped in it.
Microcystis, a type of cyanobacteria commonly called blue-green algae, thrives in warmer water temperatures that can be tied to climate change. That means the freshwater species can bloom in Southwest Florida freshwater year-round. With warmer water due to climate change, some believe the harmful algae are doing just that.
What’s not in question is how devastating long-lasting blue-green algae blooms are becoming, such as in 2018.
That summer, there was a historic outbreak of blue-green algae in Lake Okeechobee and the Caloosahatchee River turning vast stretches of water into toxic, fluorescent green scum and triggering widespread ecological damage and public health fears. Then a red tide formed along the shoreline.
The simultaneous blooms of blue-green algae in freshwater and red tide in coastal waters devastated wildlife, crippled tourism, and caused hundreds of millions in economic losses across the region. Many scientists blame chronic nutrient pollution from agricultural runoff, overflowing septic tanks, urban development, and discharges of billions of gallons of nutrient-polluted water from Lake Okeechobee into the Caloosahatchee River.
It’s starting to cause real concern in the region.
A January 2024 study commissioned by Southwest Florida nonprofits, including Captains For Clean Water, Conservancy of Southwest Florida, and Sanibel-Captiva Conservation Foundation, calculated the catastrophic economic consequences of recurring blue-green algae outbreaks. The analysis predicted that a major bloom in Charlotte, Lee, and Collier counties now would trigger $460 million in commercial and recreational fishing losses.
The study also said 43,000 jobs would be lost, and property value in the region would decline by $17.8 billion as tourism faltered. Saltwater fishing and the beach recreation sectors, which generate $6.5 billion annually, would also suffer major losses.
Health care costs from respiratory and gastrointestinal illnesses during blooms — previously estimated at up to $4 million per event — were excluded from the model, suggesting total impacts could be higher.
Reducing the supply of nutrients, nitrogen and phosphorus in particular, can help decrease the intensity and duration of blue-green algal blooms.
But that is going to be a tough place to get to with farmers, large and small, ringing Lake Okeechobee, people using too much fertilizer on lawns, and more than 100,000 septic tanks abandoned throughout Southwest Florida still leaking their contents during storms.
The blue-green algae health advisory out of Charlotte County may have been one of the first this year, but odds are there are a lot more to come.
Warm temperatures, strong sunlight, and calm water during late summer create ideal conditions for these blooms, making August and September the peak months for blue-green algae health advisories in Southwest Florida.
Environmental reporting for WGCU is funded in part by Volo Foundation, a non-profit with a mission to accelerate change and global impact by supporting science-based climate solutions, enhancing education, and improving health.
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