Record sargassum seaweed in Atlantic, Mexico beaches covered
Record levels of seaweed in the Atlantic are moving west and have already hit Mexico beaches.
Piles of sargassum stretch across the shore in Playa Lucía, Yabucoa, Puerto Rico, Monday, June 2, 2025. (AP Photo/Alejandro Granadillo)
Tracking seaweed might sound like a boring job, but the scientists at the University of South Florida Optical Oceanography Lab take it very seriously.
At the end of May, they sounded the alarm: Sargassum seaweed is forming earlier and in more abundance than ever this season in the Atlantic -- worse than the record year of 2022.
Where is the seaweed now, and where will it go?
Averaged over the month of May, this map shows the concentration of Sargassum seaweed across the Atlantic ocean. Black areas did not have sufficient data to estimate. (USF COOL)
At the end of May, the largest concentration of the 37.5 million metric tons of Sargassum was in the the eastern Caribbean Sea and western Atlantic. This broke historical records for the basin in both April and May. Piles of the stinky seaweed have rolled up on beaches in Puerto Rico already this June.
Some of that seaweed will make it to Florida and the Gulf Coast later in the summer, but the devil is in the details. Ultimately, currents and wind patterns will dictate which beaches are inundated with the brown stuff.
This map shows the risk of Sargassum seaweed affecting coastal areas. Black areas or missing coastlines did not have sufficient data to estimate risk. (USF COOL)
The Miami area is area is listed as a "high risk" for Sargassum currently by NOAA's CoastWatch website. The eastern shore of Mexico is also in the high risk, and many videos have shown seaweed on the beaches this week.
What is Sargassum?
Sargassum is a kind of seaweed, which is a type of algae. Sargassum never touches the seafloor until it dies, tends to float in island-like chunks and serves as breeding grounds for fish, turtles, birds and other animals.
Seaweed covers the Atlantic shore in Frigate Bay, St. Kitts and Nevis, Wednesday, Aug. 3, 2022. (AP Photo/Ricardo Mazalan)
Is seaweed dangerous?
The hydrogen sulfide gas it releases when it rots is not only stinky but can irritate your eyes, nose and throat, the Miami Herald says. The seaweed can also contain jellyfish or sea lice that can irritate your skin.
Because it discourages beach tourism, in 2022, Miami-Dade County spent $3.9 million to haul the seaweed to a landfill before tourists arrived each morning. This year, officials launched a competition to find new ways to recycle the piles of sargassum—and they may have no shortage of raw material to work with.
A young boy plays walks across seaweed that has accumulated on the beach, Tuesday, June 24, 2014, in Port Aransas, Texas. The Sargassum is piled and removed as it continues to wash onto the beach. (AP Photo/Eric Gay)
