Regionally, the Caribbean Sea and the Gulf of America (Gulf of Mexico) both hit record highs, according to USF’s June 2026 Sargassum outlook. In moderate amounts in the open ocean, Sargassum provides habitat for turtles, invertebrates, fish, and birds, and adds oxygen to the water through photosynthesis. Note that although the “belt” appears continuous, discrete Sargassum mats are scattered across the ocean surface. NASA Earth Observatory/Lauren DauphinThe chart above uses the continuous MODIS record since March 2000 to show how Sargassum biomass across the Great Atlantic Sargassum Belt has changed through June 2026. “Since the initial appearance of the Great Atlantic Sargassum Belt in 2011, the total Sargassum amount in the Atlantic Ocean has increased substantially, more than doubling every five years,” Hu said.