USF Researchers Develop Sunlight-Activated Material That Kills 90 Percent of Red Tide Algae Within 24 Hours

Researchers at the University of South Florida have developed a reusable, light-activated material that kills approximately 90 percent of the harmful algae responsible for Florida's recurring red tide outbreaks within 24 hours of deployment in contaminated water, the university announced in a study that is drawing attention from coastal management officials across the Gulf Coast. The material, made primarily from bismuth and iodine, is considered safe for humans and marine life and is designed to remain solid in seawater, allowing it to be recovered and reused multiple times without dissolving or degrading into the water column.

What the Researchers Developed

The research team, led by USF chemistry professor Ioannis Spanopoulos and sustainability expert George Philippidis, spent several years developing the material with a specific focus on Florida's red tide problem. Karenia brevis, the microscopic algae that blooms in Florida's Gulf Coast waters and releases potent neurotoxins called brevetoxins, has devastated marine ecosystems, killed wildlife, and driven visitors away from Florida beaches during outbreak years. Finding a treatment that could reduce algae concentrations without itself becoming a source of pollution has been one of the central challenges of red tide management research.

The USF material solves the pollution problem through its physical properties. Because the crystalline compound is designed to remain solid rather than dissolving in seawater, it can be deployed in a mesh bag, a permeable container, or a similar vessel that allows water to flow through while retaining the material. After treatment, the material can be removed from the water, dried, and reused, creating the potential for a reusable treatment tool rather than a single-use chemical application that itself becomes a water quality concern.

The mechanism by which the material kills Karenia brevis relies on sunlight activation. When exposed to solar radiation, the bismuth-iodine crystalline compound undergoes a photocatalytic reaction that generates reactive oxygen species, compounds that are lethal to algae cells at relatively low concentrations. The material essentially uses solar energy to produce a localized algae-killing environment in the water immediately surrounding it. In laboratory tests, exposure to the activated material reduced Karenia brevis concentrations by roughly 90 percent within 24 hours.

Why Red Tide Is Such a Persistent Problem in Florida

Florida's Gulf Coast has battled red tide blooms for generations, but outbreaks in recent years have grown more severe, more frequent, and more economically damaging. The worst recent event occurred between 2017 and 2019, when a sustained red tide outbreak blanketed portions of the Southwest Florida coast for more than a year, killing thousands of tons of fish, dozens of manatees, and significant numbers of sea turtles. The economic impact on coastal tourism, fishing, and property values in counties including Lee, Sarasota, Manatee, and Charlotte ran into the hundreds of millions of dollars.

The toxins released by Karenia brevis are carried ashore on sea spray, causing respiratory irritation in beachgoers and nearby residents and prompting beach closures along affected stretches of coast. Fish die in large numbers when brevetoxin concentrations reach sufficiently high levels, and the resulting mass mortality events coat beaches with rotting marine life, making affected areas effectively unusable for tourism. Manatees and other marine mammals are particularly vulnerable to brevetoxin exposure through the fish and shellfish they consume.

Red tide blooms are fed by warm water temperatures, reduced water circulation, and nutrient inputs from coastal runoff, agricultural discharges, and stormwater. Climate scientists have warned that warming Gulf of Mexico surface temperatures are likely to create conditions that are increasingly favorable for more frequent and intense blooms. Florida's ongoing water quality challenges, including nutrient-laden discharges from Lake Okeechobee and agricultural runoff into coastal water bodies, also contribute to conditions that allow blooms to persist once they establish.

A Safer Alternative to Existing Treatments

Current red tide management strategies are primarily reactive. Florida and local governments deploy monitoring buoys, conduct aerial surveys, and issue public warnings about bloom locations and respiratory risk levels. Some experimental treatments involving clay dispersal have been tested in limited settings, with clay particles binding to algae cells and sinking them to the bottom, but the effectiveness and potential ecological side effects of clay dispersal have limited its use.

The USF material offers a different approach. Because bismuth and iodine are elements already in widespread use in medical and pharmaceutical applications and are considered safe for human exposure, the research team argues the material poses minimal risk to the marine ecosystems it would be deployed in. The photocatalytic process that kills the algae targets the cellular structure of Karenia brevis specifically and operates through chemistry that is well understood in other contexts.

Unlike broad-spectrum algaecides that can kill a wide range of aquatic organisms indiscriminately, the USF team designed the material to function through targeted photocatalysis that is most effective against the algae it targets. The team conducted biocompatibility tests to assess the material's effects on other marine organisms, though independent regulatory review of those results will be necessary before any open-water deployment could receive approval.

Path to Real-World Testing

The critical next step for the USF material is a controlled field test in actual marine conditions. Laboratory conditions, while rigorous, differ from the open Gulf in important respects including wave action, variable sunlight, water temperature fluctuations, competing marine biology, and the three-dimensional distribution of algae through the water column. Researchers acknowledge that the 90 percent reduction achieved in the lab may not directly translate to equivalent results in ocean conditions without further refinement of deployment methods.

Regulatory approval for open-water testing would require engagement with state and federal agencies including the Florida Fish and Wildlife Conservation Commission, the Florida Department of Environmental Protection, and likely the Environmental Protection Agency. Those processes typically involve extensive environmental review and can take one to several years depending on the scope of the proposed test and the complexity of the regulatory pathway.

The research team has indicated interest in partnering with coastal counties, water management districts, and possibly the Florida legislature to fund the next phase of development. State funding for red tide research has fluctuated over the years, with major blooms typically driving surges in legislative attention and appropriations that fade between outbreak events. The USF breakthrough may help sustain momentum for continued investment regardless of whether a major bloom is currently active.

Reaction from the Gulf Coast

Coastal communities in Lee, Collier, Sarasota, Manatee, and Charlotte counties have the most immediate stake in any practical treatment for red tide. Those counties have borne the brunt of Florida's worst bloom years and have channeled significant local resources into monitoring, response, and economic mitigation efforts. The prospect of a reusable, low-cost, environmentally safe treatment is generating genuine interest among local officials, though experts caution that many research breakthroughs that show promise in the laboratory face significant challenges in the path to deployment at the scale Florida's coastal waters would require.

The fishing industry, which includes both commercial operations and the substantial charter and recreational fishing economy along the Gulf Coast, has a particular stake in red tide management solutions. During major bloom events, commercial fishing closures and the collapse of recreational fishing bookings cost the industry tens of millions of dollars. Any treatment technology that could shorten bloom duration or reduce bloom intensity in nearshore waters would have immediate economic benefit for fishing-dependent communities.

Tourism officials and beachfront businesses in communities like Fort Myers Beach, Sarasota, Siesta Key, and Anna Maria Island, all of which suffered devastating economic losses during the 2017-2019 bloom event, are also monitoring the USF research with interest. A summer red tide outbreak can cost a single affected county hundreds of millions in lost visitor spending over a season, and the reputational damage to Florida's beach tourism brand can persist beyond the bloom itself.

What's Next for the Research

The USF team has published its findings in a peer-reviewed scientific journal, making the research available for independent assessment by other red tide scientists and marine chemists. The next phase involves securing funding for mesocosm testing, controlled experiments conducted in large enclosed tanks or pens of natural seawater that allow researchers to test the material in conditions that more closely approximate real marine environments while still maintaining scientific controls.

Commercialization of the technology, should it prove effective in field conditions, would likely involve partnerships with environmental technology companies or government agencies with the resources to manufacture the material at sufficient scale for coastal deployment. The reusable nature of the material is a significant advantage for any commercialization pathway, as it reduces the per-treatment cost compared to single-use chemical applications and aligns with growing regulatory and public preference for sustainable environmental remediation approaches.

For Florida, where red tide has resisted every previous management approach and continues to pose recurring threats to coastal ecosystems and economies, the USF breakthrough represents one of the most promising leads in years. Whether it delivers a practical solution will depend on the outcomes of the next several years of testing, regulatory review, and scale-up work that lies ahead.

Funding and the Path to Practical Application

One of the persistent challenges in Florida's red tide research ecosystem is the episodic nature of funding. Major bloom events generate political urgency and legislative appropriations for red tide research, but between events, when the financial and reputational damage to coastal communities has faded from immediate public attention, funding tends to decline. The result is a research landscape in which promising leads are sometimes not followed through with the sustained investment needed to take them from laboratory demonstration to deployed technology.

The USF team's approach to seeking commercial partnerships for the bismuth-iodine material addresses this challenge by creating a potential revenue stream that does not depend entirely on state or federal government appropriations. If the material can be produced at sufficient scale and at a cost point that makes it commercially viable, private sector interest in licensing or manufacturing the technology could provide a more stable funding base for the research than grant cycles and legislative allocations alone.

Governor DeSantis and the Florida Legislature have in prior years allocated substantial state funding for red tide research through agencies including the Florida Department of Environmental Protection, the Fish and Wildlife Research Institute, and the university system's environmental research programs. The USF breakthrough is likely to become a reference point in future funding discussions, as legislators and the governor's office evaluate where state research dollars can produce the most significant impact on the chronic problem that has defined environmental quality concerns for Gulf Coast communities across multiple years and multiple administrations. Translating a laboratory result into a funded field research program that can demonstrate real-world effectiveness is the essential next step, and securing that funding will be a key measure of whether the USF breakthrough becomes a practical management tool or remains a promising but unrealized scientific advance.