Florida’s beaches are facing an unprecedented influx of sargassum seaweed in 2025. According to the University of South Florida’s Optical Oceanography Lab, the amount of sargassum in the Caribbean and western Atlantic has reached levels 200% higher than historical records for April and 40% greater than the all-time high recorded in June 2022. “In April 2025, the total Sargassum amount sets a new record that exceeds the all-time high in June 2022, while the exact reasons remain to be investigated,” according to the University of South Florida’s College of Marine Science.
Photo: Charles Boyer / FMN
This massive bloom is part of the Great Atlantic Sargassum Belt, a 5,000-mile-long stretch of floating seaweed that has been expanding since 2011. The belt’s growth is attributed to factors such as nutrient-rich runoff from rivers, rising sea temperatures, and changing ocean currents. These conditions have created an ideal environment for sargassum proliferation, leading to increasingly severe beach inundations along Florida’s coastline where sargassum is prevalent.
The Current Forecast
“As predicted last month, the Sargassum amount in each region but the east Atlantic increased in April. The increases in the Gulf of Mexico and western Caribbean Sea were typical as in most previous years, but total amounts in the eastern Caribbean Sea and west Atlantic reached surprisingly high levels – they were both 200% higher than their historical records in April. Similarly, the total amount in all regions combined was 150% higher than the historical record in April. Furthermore, this total amount was 40% higher than the all-time high in June 2022, which makes 2025 a new record year.”
Outlook of 2025 Sargassum blooms :A perspective for the Caribbean Sea and Gulf of Mexico* April 30, 2025, by University of South Florida Optical Oceanography Lab (bbarnes4@usf.edu, yuyuan@usf.edu, huc@usf.edu)
What Is Sargassum, Anyway?
Photo: NOAA
Sargassum is a genus of large brown seaweed, and is actually a type of algae that floats in island-like masses and never attaches to the seafloor. Early Portuguese explorers named it “Sargassum “after finding it in an area of the Atlantic that was later named the “Sargasso Sea.” The sailors thought Sargussum was like the wooly rock rose (Halimium lasianthum) that grew in their water wells at home, called sargaço in Portuguese.
While it is at sea, sargassum is beneficial to the ocean ecosystem as a floating habitat, food source, and breeding ground for various marine animals. Florida beaches affected by sargassum seaweed see both ecological benefits and challenges related to Florida beaches and sargassum accumulation. It provides shelter and resources for fish, sea turtles, crabs, shrimp, and other marine life, contributing to the health and diversity of the Sargasso Sea and other areas where it is abundant.
The arrival of sargassum on Florida’s shores is where problems for humans and wildlife begin. Sargassum brings with it a host of challenges. As the seaweed decomposes, it emits hydrogen sulfide gas, producing a foul odor reminiscent of rotten eggs. This smell can deter tourists and pose health risks to individuals with respiratory conditions. Additionally, thick mats of sargassum can smother marine life, disrupt nesting grounds for sea turtles, and impede coastal water systems. It is an unsightly, smelly mess than can harm some kinds of wildlife on the coast and is considered a general nuisance.
Some local governments and beach communities in the Sunshine State are grappling with the logistical and financial burdens of sargassum removal. Brevard County and other jurisdictions do not remove the sargassum at all, preferring to allow nature to take its course. The removal process is labor-intensive and costly, often requiring heavy machinery and frequent clean-up efforts to maintain beach accessibility and aesthetics. In some areas, the accumulation of seaweed has led to temporary beach closures and advisories, further impacting tourism-dependent economies.
As of mid-May 2025, Cape Canaveral’s beach in Brevard County (pictured above), is experiencing significant sargassum seaweed accumulation, marking the onset of what experts are predicting as a record-breaking season. City officials have opted not to remove the seaweed to avoid disturbing sea turtle nesting sites, which are currently active along the Space Coast. Residents and visitors are advised to exercise caution, as contact with fresh sargassum can cause skin irritation due to microscopic organisms present on the seaweed. This influx on Florida beaches is expected to continue through October, influenced by ocean currents and wind patterns.
Photo: Charles Boyer / FMN
Advanced Forecasting and Monitoring Efforts
To better predict and manage sargassum blooms, researchers at the University of South Florida have developed a high-resolution detection and forecasting system. This system utilizes satellite imagery and ocean circulation models to monitor sargassum distribution and movement with greater precision. By providing near real-time data, the tool enables coastal managers to anticipate seaweed landings, particularly at Florida beaches troubled by sargassum, and implement timely mitigation strategies.
Resource managers in South Florida now have a new tool in their fight against sargassum thanks to a five-year, $3.2-million grant from the National Oceanic and Atmospheric Administration (NOAA) Monitoring and Event Response for Harmful Algal Blooms program that was awarded in 2023.
The enhanced forecasting capabilities allow for more targeted responses, such as deploying barriers to prevent sargassum from entering sensitive areas, scheduling clean-up operations more efficiently, and informing the public about potential beach conditions, particularly in areas impacted by sargassum on Florida beaches. These proactive measures are crucial in minimizing the ecological and economic impacts of sargassum invasions.
Looking Ahead: Preparing for the Peak Season
As Florida approaches the peak sargassum season in the coming months, citizens and tourists in the state’s coastal communities dealing with sargassum on the beaches are urged to stay informed.
The University of South Florida’s ongoing monitoring efforts will continue to provide valuable insights into the progression of the bloom. Residents and visitors are advised to heed local advisories, support beach clean-up initiatives, and exercise caution when encountering large accumulations of seaweed.
University of South Florida: Sargassum Watch System
While sargassum presents significant challenges, it also underscores the importance of adaptive coastal management and environmental stewardship.
For more Florida news, click here!
