Sargassum Belt

A type of brown floating algae known as Sargassum has shifted its range in recent decades, thinning out in the North Atlantic's Sargasso Sea while proliferating in the tropical Atlantic.

The Great Atlantic Sargassum Belt, which stretches nearly continuously from West Africa to the Gulf, saw its second-highest Sargassum year in the satellite record in June 2026, according to scientists at the University of South Florida (USF) College of Marine Science.

Regionally, the Caribbean Sea and the Gulf of America both hit record highs, with 3.6 and 9 million metric tons in the western and eastern Caribbean, respectively, and 5 million metric tons in the Gulf.

Sargassum provides habitat for turtles, invertebrates, fish, and birds, and adds oxygen to the water through photosynthesis, but too much of it near shore can tangle and suffocate marine life, and mats that sink can smother corals and seagrasses.