Sargassum Swamps South Florida Beaches During World Cup

In early June 2026, as the FIFA World Cup draws crowds, a bloom of sargassum seaweed has blanketed the Atlantic and Gulf coasts of South Florida. The brown mats stretch for miles, emit a strong hydrogen-sulfide odor, and have forced many visitors to avoid the sand and surf.

The Hill

Scientists trace the bloom to the Great Atlantic Sargassum Belt, a band of algae that has expanded since 2011. Mass estimates differ: University of South Florida notes 29 million metric tons in the ocean, Interfax-cited Guardian cites 13 million tons in the belt, and FIU researchers estimate roughly 10 million metric tons.

Ocean sargassum useful beyond South Florida beaches

The rotting mats release hydrogen sulfide and ammonia, causing respiratory irritation, and EPA notes pesticides, heavy metals, and Vibrio vulnificus bacteria. Nutrients threaten seagrass, mangroves, and coral reefs, driving tourists away. Florida health officials advise avoiding contact, wearing gloves, and closing windows; EPA funds FIU research to convert the algae into fertilizer and biogas.

Harmful seaweed washed up on Florida beaches

Visitors like Kirsty Douglas described walking on the beach as “like walking on a sponge,” while her children turned the seaweed into a game. Lucia Heighes said the smell was so overpowering they could not stay on the sand, prompting tourists to abandon beach plans and seek indoor alternatives.

Ocean sargassum useful beyond South Florida beaches

Reported sargassum quantities differ—FIU cites roughly 10 million metric tons, Interfax-cited Guardian reports 13 million tons, and University of South Florida notes 29 million tons in the ocean—showing no standardized measurement. Scientists also disagree on decomposition effects on coral reefs, and health data remain limited to anecdotal reports.

Ocean sargassum useful beyond South Florida beaches

Florida International University researchers are testing ways to extract alginate for food and convert sargassum into fertilizer and biogas, backed by an EPA grant. They aim to lower the algae’s environmental load. Forecasts indicate beachings will intensify through summer, potentially reaching Texas and Louisiana, highlighting the need for scalable mitigation.

Ocean sargassum useful beyond South Florida beaches

• “We weren’t sure if this was normal,” — Kirsty Douglas, 40, visitor

New York Times

• “Beaching events around the Caribbean and southeast coast of Florida will continue and likely increase,” — University of South Florida researcher

The Hill

• “I think if we go about this research the right way, we can benefit a lot from it,” — Dr. Imran Ahmad, FIU food scientist

Ocean sargassum useful beyond South Florida beaches

• “It’s to the point that you can’t even be in the sand because the smell gets to your head and you can’t even go in the ocean,” — Lucia Heighes, FIU student

Ocean sargassum useful beyond South Florida beaches