Those giant patches of floating algae called sargassum that originate in the Atlantic Ocean, then head west on currents toward Florida and the Caribbean, are getting bigger every year.
Massive piles of sargassum, the size of which have not been seen before, are floating this way, right now, sure to coat the beaches of Florida's East Coast, the Keys, and various Caribbean islands.
The long band of sargassum heading west from the South Atlantic is called the Great Sargassum Belt, and right now, there is more of it heading this way than ever before.
All totaled, there are nine-point-five million metric tons of it this year — record amounts — and the sargassum mats are growing larger by the day.
Massive sargassum blooms are either wonderful or awful, depending on what type of creature you are. In open water, the huge mats have endless nooks and crannies for small fish, crabs, and sea turtles to grow protected.
But once the sargassum hits Caribbean island beaches, it piles up, day after day, and to clear the beach for tourists later in the day is often back-breaking work, with hand tools at dawn, often. If left on the shoreline, sargassum decomposes, attracts insects, and smells like rotten eggs as it emits hydrogen sulfide.
It also smothers sea turtle nesting sites, increasing hatchling deaths, and causing fish kills.
MORE:
- Massive swath of brown algae angles toward Southwest Florida beaches, but need we worry?
- Water Quality Report: Sargassum? What Sargassum?
- Atlantic sargassum mass growing early, setting records, eyeing Florida
- Sound at sea, sargassum buries beaches and threatens tourism
- WGCU's Tom Bayles discusses Florida's sargassum problem nationally in 2024 on NPR's All Things Considered
The increases in sargassum are likely to be caused by global warming, increasing the temperatures, affecting ocean currents, and providing more nutrients, according to the authors, and could have a significant impact on marine life, tourism, and coastal economies.
Sargassum can, and does, bury beaches in Southeast Florida and in the Florida Keys. But the Loop Current usually keeps the stinky seaweed off the beaches of Southwest Florida
Researchers at the University of South Florida's Sargassum Watch System, which works with NOAA to use satellites to improve forecasting of the algae blooms and their size, warn that the huge mats of the brown and banana-colored algae are growing larger this month.
The USF July 2025 bulletin estimated 38 million metric tons total in the entire Atlantic, including the Caribbean Sea and Gulf of America.
The top sargassum researchers at USF's College of Marine Science, Brian Barnes and Chuanmin Hu, said in 2022 that the Great Sargassum Belt was so big it posed challenges on a hemispheric scale for marine ecosystems and coastal towns in terms of tourism, fishing, and marine life. It reached 19 million metric tons that year.
Last year, USF estimated 38 million metric tons total in July in the entire Atlantic, including the Caribbean Sea and the Gulf.
There are about three or four months until this sargassum season's total will be known.
"Before 2008, there were no major blooms of macroalgae reported except for sargassum in the Sargasso Sea," Hu said. "On a global scale, we appear to be witnessing a regime shift from a macroalgae-poor ocean to a macroalgae-rich ocean."
Environmental reporting for WGCU is funded in part by VoLo Foundation, a nonprofit with a mission to accelerate change and global impact by supporting science-based climate solutions, enhancing education, and improving health.
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