Seaweed Blob Headed to Florida Shrinks Dramatically

But scientists don’t know why the decline was so rapid. One theory is that strong winds caused by recent tropical storms could have dissipated the sargassum into smaller clumps, or sunk it to the ocean floor, Dr. Hu said, making it hard to see from a satellite. “There could be other reasons, we just don’t know,” he added.

While floating sargassum can benefit marine animals by providing shade and shelter, it begins to die once it comes ashore, degrading water quality and polluting beaches, scientists say. The decaying algae also releases hydrogen sulfide, a colorless gas that smells like rotten eggs, and can cause respiratory problems in humans. Some types of bacteria may colonize rafts of sargassum and marine plastics, which, once ashore, can pose a risk to public health, according to a recent study published by researchers from Florida Atlantic University.

Sarah Collier, who works for Seabird Key, a private island vacation rental in Key West, said that her community had been on edge since hearing of the sargassum blob earlier this year. “It’s such a relief,” she said of news that it was dissipating in the Gulf of Mexico, noting that she had not personally seen more seaweed than usual.

But while tour operators, holidaymakers and locals in Florida are enjoying sargassum-free beaches, the situation is not as rosy further south.

The beaches of the Dominican Republic, Haiti, Puerto Rico, the U.S. Virgin Islands, British Virgin Islands, the Lesser Antilles Islands, Barbados and Trinidad, will likely remain threatened by seaweed for the next one to two months, Dr. Hu said.

He and his colleagues predict that over the next two to three months, the amount of sargassum in the Gulf of Mexico will remain minimal, and that it will either decrease or remain stable in the Caribbean Sea. While that’s good news for the residents of Florida’s east coast, as well as the Florida Keys, sargassum is still likely to wash ashore in parts of the Caribbean, they said in the bulletin, noting that it was “difficult to predict exact timing and location for individual beaching events.”