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Will the Seaweed Blob Affect Your Florida or Caribbean Vacation This Summer?

Sargassum washed ashore in the Florida Keys and Cancun, but there may be hope

spinner image miami beach florida covered in sargassum seaweed
Sargassum washes up on the beach in Miami Beach, Florida, in May 2023. This rotting seaweed is smelly.
Photo by: Jeffrey Greenberg/Universal Images Group via Getty Images

Red tide, hurricanes, spring breakers: These aren’t the only factors beyond your control that can impact your vacation plans in Florida and the Caribbean.

For the last few months, the talk has been all about Sargassum, also referred to as the seaweed blob, the floating algae that’s washed ashore in places such as the Florida Keys, Barbados and Cancun, Mexico. The rotting, stinking algae leaves less than postcard-perfect views atop beaches that usually have no trouble getting by on their looks.

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With the current Sargassum bloom in the Gulf of Mexico predicted to peak from June to July, you might be wondering what to expect if you have vacation plans in Florida or the Caribbean.

AARP reached out to experts for the latest information on the Sargassum, where its effects are most likely to be felt ashore and potential health complications related to the rotting seaweed. 

What is Sargassum

Sargassum is a genus of naturally occurring algae or seaweed that exists in hundreds of species. 

“In the Atlantic Ocean and Gulf of Mexico, the dominant species are Sargassum fluitans and Sargassum natans,” says Chuanmin Hu, professor of optical oceanography at the University of South Florida. “Both are yellowish-brownish seaweed that are pelagic, meaning they live in surface waters and are not attached to ocean substrates,” such as sand or coral reef.

Sargassum has gas-filled structures called pneumatocysts that look like little berries and help to keep it afloat. “Once it dies, it sinks to the ocean floor,” Hu says. “But before it dies it can be washed ashore by wind, tides and ocean circulation, and this is what people are worried about.”

At sea, Sargassum provides an important habitat for juvenile fish and unique creatures that have evolved to live there, including perfectly camouflaged Sargassum frogfish, says Tracy Mincer, assistant professor of biology/biogeochemistry at the Florida Atlantic University (FAU) Harbor Branch Oceanographic Institute.

And while much clickbait has been made about the size of the Great Atlantic Sargassum Belt — the 5,000-mile-long, 300-mile-wide area of ocean with patches of Sargassum scattered from the coast of West Africa to the Gulf of Mexico — it’s important to note that it’s not a solid mass of continuous seaweed making its way toward our shores, Hu says.

“Remember, the Atlantic Ocean is huge. Within the Great Atlantic Sargassum Belt, you don’t find Sargassum everywhere. It’s scattered in patches,” he says, likening its density to the visual of ground pepper spilled across a table, heavier in some parts and only lightly sprinkled or absent in others.

Relative to the surface area of the Atlantic Ocean, the portion covered by Sargassum is almost nothing, but the total amount is huge, Hu says. 

“So even when a tiny amount of the total is washed on the beach, it means a lot to people,” he says. “It’s simply a scale difference."

The recent Sargassum bloom has been fueled by nutrient runoff — including nitrogen and phosphorus from agricultural runoff — arriving from rivers that flow into the Atlantic Basin, including Africa’s Congo River, the Amazon and the Mississippi, according to Brian Lapointe, a research professor with the FAU Harbor Branch Oceanographic Institute. Lapointe says natural nutrient sources, such as ocean upwellings and Saharan dust clouds, also contribute to Sargassum growth.

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A growing problem — and a hint of hope

This year, Hu says, his university released findings showing that the amount of seaweed in the Great Atlantic Sargassum Belt had doubled for two consecutive months, in December 2022 and January 2023. But the findings for May turned out to be a “surprise, in a good way,” he says. Sargassum cover in the belt decreased by 15 percent from April to May.

Hu says the amount of the algae had always increased from April to May. This year’s satellite findings are “likely due to ocean circulation and wind that changed the nutrient structure” feeding Sargassum growth, he says.

And the absence of a dramatic increase in Sargassum in the Gulf of Mexico in May is a “really good sign” for beaches on Florida’s east coast and the Florida Keys, Hu says. Sargassum in the Keys and the state’s east coast generally comes from the Gulf of Mexico, he says.

Hu cautions that May’s findings do not mean that those Florida beaches will be algae-free, however. “Those areas will get a certain amount of Sargassum, small to moderate, in the next few weeks,” he says.

Florida’s west coast beaches, from the eastern part of the Florida Panhandle south to Naples, “will be spared regardless of what happens on the east coast of Florida, mainly because of ocean currents,” he says.

As for the western part of the panhandle, and from Mobile Bay up into the Mississippi River Delta, that area will get some Sargassum depending on how far north the loop current penetrates, Hu says. “If it doesn’t go very far north, even the western part of the panhandle will be OK,” he says.

“The Caribbean Sea will continue to be the most affected [by Sargassum], there is no exception,” Hu says. He pointed to places like the U.S. Virgin Islands, the Dominican Republic, the Cayman Islands, Puerto Rico, Haiti and Mexico’s Yucatan coast as having seen major effects from where the seaweed washed ashore in recent years.

Can Sargassum affect health?

In addition to being unsightly and foul-smelling when it washes ashore, Sargassum has some potential health effects to be aware of. 

Sargassum itself is not harmful to health, says Jose Vazquez, M.D., chief of primary care for Baptist Health Medical Group in South Miami, Florida. But when it decomposes onshore, he says, it releases hydrogen sulfide gas. 

“It smells like rotten eggs and is an irritant to the respiratory system,” Vazquez says. People prone to respiratory problems — with chronic obstructive pulmonary disease (COPD), asthma, congestive heart failure or severe allergies — might see a worsening of their respiratory conditions when in close proximity to large quantities of decomposing Sargassum, he warns. Symptoms can include a runny nose, watery eyes, sneezing, coughing and shortness of breath. 

Staying safe around Sargassum is simple, he says: “If you know you have a respiratory problem, stay away from beaches when there’s a Sargassum problem.” People with asthma should use an inhaler, and if symptoms worsen, see a doctor. 

Mincer cautions people against touching Sargassum without protection on their hands due to the potential presence of Vibrio bacteria, a pathogen his research team found present in Sargassum with plastic marine debris entangled in the seaweed. Coming into contact with Vibrio can cause an infection, especially if you have an open wound, Mincer says.

“I’m not trying to freak people out, but wear gloves or wash your hands after, and be careful of open cuts,” he says.

Not freaking out about the Sargassum situation and your Florida summer vacation might be a good rule of thumb right now, too.

“In short, the sign is good for Florida, but we need to see what happens,” Hu says. “If this declining trend continues in the Gulf of Mexico, then by July most affected beaches in Florida should only have small to negligible amounts of Sargassum.” 

But if you’re planning a beach vacation on Florida’s east coast, in the Florida Keys or the Caribbean, be aware that the situation can always change, Hu says. 

“Now, I am more and more cautious whether I can really predict the future,” he says. “Life is full of surprise.”

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