South Florida Grapples with Mounting Sargassum Invasion Along its Coastline

FORT LAUDERDALE, Fla. — For Concetta Distefano, summer trips to the beach have brought an unwelcome sight: thick piles of brown sargassum covering the shoreline and crowding the path to the water.

She expected the familiar sights of clear water, warm sand and swimmers along the shoreline. Instead, she was met with piles of brown algae and the strong, unpleasant smell of decaying seaweed.

“Every August, sargassum seems to be a persistent problem, but this year has been worse than previous years. The large quantities of seaweed have flooded the shoreline and made it much harder for my family to enjoy the beach,” Distefano said. “I love to swim, so it’s especially disappointing when the sargassum makes it difficult to get in the water.”

For residents and visitors across South Florida, the problem has become increasingly difficult to ignore. In June, large accumulations of Sargassum washed ashore along beaches from Miami Beach to Fort Lauderdale, where the decomposing seaweed produced an odor that lingered along the coastline. 

Miami-Dade spends about $3 million a year on sargassum cleanup – and the problem may be getting worse. In just the month of July, the city removed 9,000 tons of seaweed, more than ever removed in a single month before, Chris Bumpus, the Chief of Conservation for Miami-Dade county’s parks, told The Guardian.

What appears to be an ordinary mass of seaweed is part of a much larger phenomenon unfolding across the Atlantic, Caribbean and Gulf.

Sargassum is a floating brown algae that spends its life at sea rather than growing from the ocean floor. Large floating mats provide important habitat for fish, crabs, shrimp, sea turtles and other marine organisms. Much of the sargassum affecting Florida originates in the tropical Atlantic before being transported by ocean currents and winds toward the Caribbean, Gulf and Florida coastline. Since 2011, scientists have observed substantially larger quantities of Sargassum appearing throughout the tropical Atlantic and Caribbean.

According to the University of South Florida's Optical Oceanography Lab, 2026 is now projected to be the second-largest Sargassum year on record, behind 2025. The lab reported that June 2026 brought record-high Sargassum levels to the Caribbean, while the Gulf accumulated approximately 5 million metric tons, nearly twice the previous historical record for the region.

Moreover, the stinky seaweed is no longer just a summertime issue. What was once confined to the warmer months is now lingering into the winter season. As of December 2025, Florida’s Gulf Coast reported high levels of sargassum buildup, while low-level blooms persist in multiple U.S. regions. Warmer oceans and shifting weather patterns are stretching the bloom season.

What was once harmless seaweed has now become an increasing environmental concern. The presence of sargassum has been known to negatively affect coral reefs, hinder tourism and lastly, deprive marine organisms of oxygen living within the region, experts say.

Over the last 15 years, experts have recorded a dramatic increase in the amount of sargassum along the coastline of South Florida. The large amounts of sargassum present along Florida's coastline make sea turtle hatchlings particularly vulnerable, as turtles get stuck in the tall mounds of sargassum piled up on the coastline.

In June of 2018, the University of South Florida's Optical Oceanography Lab acknowledged the biomass surpassed 20 million metric tons, which at the time was the highest metric on record. However, a recent analysis dating back to June 2022 reported 24.2 million tons. In May of 2025 the report indicated that monthly biomass reached an extreme high of 37.5 million tons, the largest amount ever recorded in history.

“We can observe the seasonality, and the first time we saw really anything with this bloom was in 2011,” said Brian Barnes, a research assistant professor at the College of Marine Science at the University of South Florida. 

“Since then, with that seasonality in mind, we just kept seeing an increase every year,” Barnes explained. “The larger trend has been steadily increasing over the last 14 years, and prior to that, we didn't see anything like this.”

Sargassum has proven to be a persistent issue affecting the south Florida region significantly. As large quantities of decaying algae lead to decreased oxygen levels in the water, directly correlating to suffocating fish and the decomposition of ocean ecosystems.

“Sargassum carries an unbearable odor, directly affecting tourism. Although the odor itself is not harmful, the overbearing smell harms people enjoying their time on the beach,” said Jace Tunnell, Director of Community Engagement at the Harte Research Institute at Texas A&M University- Corpus Christi.

“This year, sargassum hit its peak exponentially,” Tunnell explained. “Sargassum is an ongoing issue that has to be watched closely. Although there is no direct way to combat the issue due to its build-up in international waterways, we continue to watch it closely every day.”

Experts are working to identify ways to mitigate the effects of persistent Sargassum blooms. At the University of Miami, researchers are tracking sargassum at sea to better understand how the algae moves and accumulates in large quantities before reaching shore.

Although the golden-brown algae cannot be eliminated permanently, continued efforts to monitor its movement will help researchers develop methods to lessen its impact on tourism and South Florida’s beautiful beaches.