Nearly a decade ago, the worst red tide outbreak in a generation choked Sarasota Bay and much of Florida’s Gulf Coast, killing marine life by the thousands and sickening residents.
From October 2017 through January 2019, crews removed more than 2,400 tons of dead animals from beaches and waterways as the toxic bloom killed hundreds of manatees, dolphins, whales and sea turtles, along with countless fish, crabs and other creatures that washed ashore.
It also sent people with respiratory issues to the hospital and dealt a $2.7 billion blow to the local economy. The event was “unprecedented in duration, intensity and impact,” according to one report.
Now, scientists say a wave of new research happening in Sarasota could help stop future outbreaks before they spiral into that kind of disaster.
Researchers at Mote Marine Laboratory are testing a new generation of treatments designed to kill red tide organisms quickly without harming the surrounding environment. In lab and field trials, some have reduced algae levels by more than 70%, raising hopes that blooms could one day be knocked down before they spread.
At the same time, federal officials have recently changed how water is released from Lake Okeechobee, a shift experts say could reduce the conditions that fuel and intensify red tide once it reaches coastal waters. That change, adopted in 2024, is designed to send more water south through the Everglades while reducing harmful discharges to estuaries along Florida’s west coast.
Together, those developments mark a potential turning point in a problem that has long felt inevitable, and uncontrollable, for coastal communities.
If successful, they could not only reduce the environmental damage caused by red tide but also limit the economic losses and public health risks that ripple through the region during major outbreaks.
For decades, red tide has been a recurring threat along Florida’s Gulf Coast. The blooms, caused by the organism Karenia brevis, form when algae multiply rapidly in coastal waters. Scientists say pollution and runoff, including large discharges from Lake Okeechobee, help fuel those blooms once they reach the coast.
In recent decades, outbreaks have persisted for months at a time and appeared outside their typical seasonal patterns, raising concerns that the problem is getting worse.
Suncoast Searchlight reviewed recent scientific studies, examined state and federal water management policies, and interviewed marine scientists, engineers and environmental experts to understand how those efforts intersect and what they could mean for the region.
But some area environmentalists fear the mitigation could have unintended consequences, replacing one disaster with another that’s even worse.
“We do believe that mitigation is probably rife with unintended consequences,” Suncoast Waterkeeper Executive Director Abbey Tyrna said.
Glenn Compton, chairman of the local environmental nonprofit ManaSota-88 Inc., also would rather see more effort aimed at eliminating wastewater “at its source,” which would erase the need for mitigation.
Cynthia Heil leads the Red Tide Institute at Mote, where researchers have tested more than a hundred compounds designed to reduce the intensity of red tide blooms.
Heil, a biologist with a master’s degree in red tide from the University of South Florida College of Marine Science, said researchers are using only compounds that are safe for the marine environment.
She says the first priority with the testing is to “do no further harm than the red tide is doing.”
Red tide’s link to Lake Okeechobee
Red tides in Florida have been documented since the 1500s — and their likely impacts date back to records from Spanish explorers. The toxic tides are caused by Karenia brevis. The harmful algal blooms occur when colonies of the algae grow out of control and are common during the hottest months of the year.
Research shows that over time, these toxic blooms have gotten worse. The Maryland Center for Environmental Science and Mote this year released a series of studies that documented “a clear shift toward longer, more severe, and seasonally altered red tide events” on the west coast of Florida.
Researchers point to Lake Okeechobee as the primary culprit.
Lake Okeechobee is the largest lake in the southeastern United States, covering 730 square miles. It is so big, in fact, you cannot see all the way across it in most areas.
Situated in the middle of the state, the lake has faced rising levels of nutrient contamination from sugar farming, including high concentrations of nitrogen, phosphorus and ammonia — elements commonly found in fertilizers and human waste — all of which feed the algae blooms.
For years, the U.S. Army Corps of Engineers has managed water levels in the lake through controlled releases to prevent it from cresting and flooding neighboring communities. When levels get too high, the Corps dumps lake water into the Caloosahatchee River, which flows into the Gulf and exacerbates red tide.
That’s exactly what happened during red tide blooms in 2004 and again in 2017.
But after environmental groups sued the Corps in 2019, arguing the toxic discharges from the lake were endangering protected species, including manatees, a federal judge ordered the agency to consult with stakeholders to minimize environmental impacts.
The result was a new operating manual for Lake Okeechobee releases, adopted in August 2024, that prompted the Corps to take a more proactive approach to keeping the lake waters low.
The Lake Okeechobee System Operating Manual was implemented to reduce harmful discharges into estuaries by instead sending more water south — where it is filtered naturally by the Everglades.
Fewer releases of nitrogen may “significantly reduce the duration of (red tide) blooms, particularly those originating with the Caloosahatchee River and Lake Okeechobee,” the Corps announced in 2024.
“The lawsuit certainly seemed to have the effect of increasing accountability and transparency in the process,” said Jaclyn Lopez, who was lead counsel in the lawsuit when she worked for the Center for Biological Diversity and is now a professor at Stetson Law School.
Lenny Landau, a retired mechanical engineer, has lived in Longboat Key since 2002. He has been studying Lake Okeechobee’s connection to red tide for eight years and co-authored a peer-reviewed paper for Florida Scientist in May 2024.
He said the reductions in the lake’s overflow are key to preventing the massive blooms that have devastated the Suncoast.
“The takeaway is that we’re not going to have these events, which is very significant,” Landau said.
Inside Mote’s red tide research lab
About 15 miles from the coast, a cluster of buildings tucked away in a rural area off eastern Fruitville Road make up the Mote Aquaculture Research Park.
Among the structures is the laboratory home for the red tide mitigation project — a 28,800-square-foot laboratory, where researchers are developing tools they hope will stop red tide in its tracks.
The facility includes an aquarium that can hold almost 150,000 gallons of treated and recirculated seawater, where scientists can grow algae and create mini versions of Sarasota Bay, complete with shellfish, seaweed, sponges, sediments and other ecosystem components that could be sensitive to mitigation efforts.
The lab was created with funding from a 2019 state law that provides $3 million a year to support the Florida Red Tide Mitigation & Technology Development Initiative as a partnership between Mote and its government partner, the Florida Fish and Wildlife Conservation Commission.
Mote researchers have evaluated more than 300 chemicals and compounds, and over 40 projects have been completed or are currently underway, according to a January progress report.
A handful of products have even been tested at canals in Venice, waters adjacent to Sapphire Shores Park in Sarasota and near Fort Myers.
“We are actually testing in the water right now,” said Heil, the director of the Red Tide Institute and senior biologist at Mote.
The institute is testing various chemical compounds that could potentially kill red tide without harming the other sea life. They include targeted pesticides and herbicides that are already used on the market for other purposes.
Several herbs and spices also have been tested against algae blooms, including turmeric, according to one research paper. Turmeric, commonly used in curries, soups, and rice, is known for its vibrant yellow color and earthy, mild flavor.
“Turns out it works wonderfully well at killing red tide cells,” Heil said.
Mote also has been testing clay to control algal blooms. The clay drags red tide organisms and their toxins to the seafloor, where it smothers them.
“I’m really encouraged,” Heil said. “Florida is kind of at the forefront of this research. Our program is at the forefront. And based on do no further harm.
“We’re producing results. We’ve gotten to the field. And now, we’re really waiting for the next bloom.”
This story was produced by Suncoast Searchlight, a nonprofit newsroom of the Community News Collaborative serving Sarasota, Manatee and DeSoto counties. Learn more at suncoastsearchlight.org.
