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

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.

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.