Will we have a repeat of last summer? August 2022 staff file photo
By Larry Barszewski
Sea turtles aren’t the only things returning to south Palm Beach County beaches this year.
So is seaweed. Lots and lots of it.
Not since Jaws has so much attention been given to a potential menace lurking off the coastal shoreline. Most every major television network, including cable, has run news segments in recent weeks about the massive amount of sargassum — a brown, free-floating seaweed — heading this way.
The sargassum — or the “blob,” as some have dubbed it — has also made the pages of the New York Times, Washington Post and Wall Street Journal — even The Guardian in England.
It is accumulating in the Atlantic Ocean at a record pace, forming the Great Atlantic Sargassum Belt that stretches 5,000 miles from the west coast of Africa to South America and is hundreds of miles wide.
Offshore, it is a floating buffet, offering food and a place to hide for small fish, juvenile sea turtles and other marine life.
On the beach, though, it decomposes and produces a rotting-egg stench as it releases hydrogen sulfide gas. Beach visitors stepping in or touching the seaweed can get skin rashes and blisters from jellyfish larvae, sea lice and other marine organisms on the sargassum.
“I don’t want to scare away tourists by giving a false alarm: ‘Look, there’s a gigantic blob coming your way.’ No, that’s not the case,” says professor Chuanmin Hu, an optical oceanographer at the University of South Florida in Tampa who studies the sargassum. “What my group has been saying is there’s a gigantic blob in the Atlantic Ocean and a small amount of that blob will sooner or later come to Florida. And that doesn’t mean every beach will get a lot of sargassum.”
So, if you’re wondering whether the sargassum washing ashore on South Florida beaches will be more or less than last year’s, the answer is yes.
Where the wracks of sargassum land is at the mercy of coastal currents, tidal action and wind patterns. Some stretches of beach will see smaller amounts than in 2022, while other sections will see significantly more pile up.
“Predicting nature, especially in this regard, is dangerous because we don’t fully understand what’s going on in the vast ocean,” Hu says.
But make no mistake, there’s an awful lot of sargassum out in the ocean — more than 6 million tons of it in the belt as of February — and more is expected. Last year peaked at about 22 million tons in the ocean in July. Last year’s amount broke the previous record set in 2018, and this year may well top the 2022 level.
Not a single blob
The sargassum belt is not a single blob, though it may look that way from satellite imagery. It’s made up of clumps of sargassum spread out over about 2 million square miles of the ocean. If you took out the spacing between clumps, the sargassum would cover an area roughly the size of Lake Okeechobee, Hu says.
The amount of sargassum in the belt doubled in size in December and doubled again in January, before shrinking by about 20% in February, according to USF research data. Early indications were that it was growing again in March.
It’s anticipated that it will keep growing as we head into the peak summer months, fueled by nitrogen and phosphorous flowing into the ocean from the Congo, Amazon and Mississippi rivers.
While Southeast Florida could see large amounts of sargassum this summer, it’s unlikely to have beaches with anywhere near the 6-foot-high piles known to rise up on some islands in the Caribbean.
Sargassum is carried here on strong ocean currents. The sargassum is at its densest as it flows through the Caribbean, along the Caribbean Current, depositing huge piles along the shores there.
Then, as it heads toward Mexico it is picked up by the Yucatan Current and then the Loop Current that takes it through the Gulf of Mexico. The sargassum that hasn’t been washed ashore then moves into the Strait of Florida between Cuba and the Florida Keys, traveling along the Florida Current. That current then takes the sargassum into the Gulf Stream, which carries it northward just off the East Coast, where a good wind out of the east will push it to shore.
The worst of the sargassum beaching here is expected in the summer months, but last year significant amounts showed up in April and May and kept landing on local beaches even into September.
“Mexico is already being heavily impacted,” says Florida Atlantic University professor Brian LaPointe of the Harbor Branch Oceanographic Institute.
Where sargassum will come ashore, like where a hurricane will make landfall, is hard to pinpoint with great precision. There is great variability because sargassum floats on top of the water and is heavily influenced by winds. Better satellite imagery of the coastal ocean is needed to make more accurate forecasts, LaPointe says.
“We’re hoping in the future to be able to give better predictions on sargassum landings,” he says. “Right now, we’re kind of constrained by the technology.”
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