Nothing like watching the ginormous blob of sargassum 2025 floating not too far southwest of the island to get me scurrying for a leftover Covid mask. Because, my beach-loving friends, we’re right on schedule for what the experts are calling a record-breaking Stink Season when tons of sargassum wash ashore, turning beaches into mountains of dead stuff and the water into chocolate pudding — only not so tasty.
In April the University of South Florida, one of the world’s premier laboratories for sargassum research, let us know just how big the 2025 bloom is — and it’s likely to grow as the water temperatures heat up. “(The) 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.”
Whoopty-doopty-stinky-do.
Stink Season arrives April-ish and hangs around until October-ish, pretty much corresponding with hurricane season. A hurricane or other big blow is often the only thing that clears the sargassum out of the nearshore water. Who’d have thought there was a side benefit to a hurricane?
Sargassum is nature’s nursery for all sorts of sea creatures, like turtles, fish and even the occasional Man o’ War jellyfish. It’s not particularly harmful to humans who swim through or fish in it, though new research has begun using terms like “flesh-eating bacteria.” Sargassum tickles your skin — as long as it’s alive — when it floats past in lovely yellow bunches. Darn hospitable stuff that’s been around since, well, forever.
But the past decade of outsized sargassum blooms has brought warnings. Once that biomass hits land, it piles up into walls of decaying flora and fauna. Onshore it turns blackish-brown and stinks to high heaven of hydrogen sulfide (think rotten eggs on steroids). The dying sea creatures can sting unsuspecting toes and the hydrogen sulfide can trigger asthma attacks in folks with respiratory challenges.
You can only smell the stink for about 120 seconds before your nose says “enough” and stops noticing the offending odor. Unless you do something silly like clearing your nasal passages with a big sniff of Cuban coffee. Then you have to desensitize again.
Sargassum 2025 | Beaches were spared on Memorial Day
The water along the beach turns brackish at best and looks and feels like chunky chocolate pudding extending for yards and yards away from shore. It takes a hardy, determined water nymph to brave that mess. I sure don’t.
Used to be most of our Florida Keys sargassum floated in from the Sargasso Sea, located in the heart of the Atlantic Ocean, east of Florida and between the Bahamas and the Azores. But changing wind patterns over the past decade now push that sargassum past the Yucatan Peninsula and into the Gulf of Mexico, where the Gulf Stream sweeps it east past the Keys and up the east coast of Florida. Blooms from the South American coast add to the biomass headed our way.
Once a benign summer nuisance, sargassum 2025 now comes with microplastics, which appear to be the perfect “home” for Vibrio bacteria, aka “the flesh-eaters.” Vibrio can cause fatal food-borne illness from eating infected seafood and infections in open wounds. Not exactly the kind of information you’re going to get in an ad for a Keys vacation, huh?
Key West and Monroe County get out the big tractors most mornings and clear off the piles of dead sargassum, so the beaches are not so awful. But there’s nothing to be done about the mess in the water. It’s illegal to clear it and protective booms are ineffective or outrageously expensive. Or both. Here’s how the City of Key West cleans its beaches.
The state doesn’t clear its beaches, so that means the Fort Zachary Taylor State Park shore can be iffy. The good news for Fort Zach is that the currents tend to sweep a lot of the sargassum away before it hits the beach, though you’ll often have to wade through a lot of muck to get to clear water. Fort Jefferson in the Dry Tortugas gets some sargassum, but the currents out there tend to keep both water and beaches clear.
Most locals ignore it. We’re used to the Big Stink and adjust accordingly. Tourists not so much. They get a tad frantic about sargassum forecasts for their vacations, looking for reassurances that there will be pristine beaches for their trek. I tell them, nicely of course, that if they’re coming to the Keys in Big Stink season, assume they’ll encounter sargassum walls and sludge-like water. It is, after all, summer in Key West.
Learn more
LGC’s sargassum columns over the years:
- Dear people: We can’t predict the sargassum today, much less for your August vacation
I promised myself I was not going to write about sargassum more than three times this season. This is No.… Read more: Dear people: We can’t predict the sargassum today, much less for your August vacation - Sargassum Season 2024 | Wait! What? Key West doesn’t stinkWhew. Two Gulf of Mexico hurricanes in two weeks behind us, and I’ve got to admit I’m pretty darn happy… Read more: Sargassum Season 2024 | Wait! What? Key West doesn’t stink
- Sargassum 2024 | How many more environmental disasters do we face in the Keys?
Here’s a bit of good news: Spring break visitors to Key West and the Florida Keys dodged an early mashup… Read more: Sargassum 2024 | How many more environmental disasters do we face in the Keys? - Eau de Key West | Get a whiff of ubiquitous island essence
Couple years ago while visiting in Atlanta, I tossed my bag on the bed, unzipped the sides and flung them… Read more: Eau de Key West | Get a whiff of ubiquitous island essence - Key West weather | Or, what happened to the sargassum?On Aug. 23, 1856, an American scientist forecast the now-weeks-long heat wave smothering Key West and the Florida Keys. The… Read more: Key West weather | Or, what happened to the sargassum?
- Key West sargassum 2023 | Four months early and already piling upNo. Just no. It’s not time for the Key West sargassum 2023 update. I don’t write about Key West sargassum… Read more: Key West sargassum 2023 | Four months early and already piling up
- Key West sargassum 2022 | One of these days, it’ll kill summer beach timeIf you want a happy-face spin on the state of Key West sargassum 2022, you best look elsewhere because —… Read more: Key West sargassum 2022 | One of these days, it’ll kill summer beach time
- How’s the sargassum today on Key West beaches?Man, what a can of worms I opened last week with the post about the unholy, smelly, messy sargassum invasion… Read more: How’s the sargassum today on Key West beaches?
- OMG, does Key West really stink all the time? Or, everything you need to know about sargassumKey West smells like sewage gone way ripe. This summer we’ve gone from smell to stench and it’s not going to get better. That ubiquitous smell is decaying sargassum, islands of floating, brown sea vegetation that are piling up along the beaches of Key West, the Florida peninsula, Mexico and other Caribbean islands.
https://www.floridarambler.com/beaches/sargassum-seaweed-florida-beaches
https://www.fau.edu/newsdesk/articles/perfect-pathogen-storm.php
https://optics.marine.usf.edu/projects/SaWS/pdf/Sargassum_outlook_2025_bulletin04_USF.pdf
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