by Lacey Pfalz
Last updated: 8:30 AM ET, Thu June 4, 2026
Scientists are expecting June to be another record month for the red-brown algae called sargassum, which grows in thick clumps in the warm ocean waters of the Caribbean and washes ashore from Florida’s panhandle to the Mexican Caribbean.
The University of South Florida’s Optical Oceanography Laboratory uses satellite-based systems to monitor and track algal growth throughout the year, especially during its bloom periods, which occur from March through October.
April and May were records for sargassum this year, and the season started in January, a full three months early, due to warm ocean temperatures.
The Mexican state of Quintana Roo, located along the Caribbean, had collected 25,000 metric tons of sargassum by April, with fifteen beaches being designated “red zones” for cleanup efforts.
This June, scientists predict another record month—and are now saying it might be a record year for sargassum overall.
In May, three large clumps were detected growing throughout the Caribbean: the Western Caribbean mass was growing along the Yucatan Peninsula in Mexico; the Eastern Caribbean mass was growing alongside major cruise port destinations; and the Western Atlantic mass was growing near the upper part of South America.
“The transport of Sargassum to the Gulf also continued, resulting in record-high amount at this time of year,” the latest sargassum outlook report explained. “Major beaching events have been reported around the Caribbean and the Lesser Antilles islands as well as along the Florida Keys and east coast of Florida.”
The laboratory expects sargassum beaching events to increase across the Caribbean and southeastern Florida, with some extending into Louisiana and Texas.
Sargassum removal efforts cost destinations millions of dollars annually. In addition to being a beach irritant, it also poses health risks, as the Environmental Protection Agency warns that sargassum’s decay produces ammonia and hydrogen sulfide, which can have cardiovascular, neurological and respiratory impacts.
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