Record Sargassum Algae Bloom Hits Caribbean and Gulf of Mexico in June 2026

NASA satellite observations recorded a massive surge of the brown algae Sargassum across the tropical Atlantic in June 2026, marking the second‑highest accumulation ever measured. The Great Atlantic Sargassum Belt stretched from West Africa to the Gulf of Mexico, with the western Caribbean reporting 3.6 million metric tons, the eastern Caribbean 9 million tons, and the Gulf of Mexico 5 million tons – nearly twice the previous record.

Scientists at the University of South Florida’s College of Marine Science used the Ocean Color Instrument on NASA’s PACE satellite to monitor the bloom. While moderate amounts of Sargassum provide habitat for marine life and produce oxygen, the unprecedented volumes threaten coastal ecosystems, tourism, and public health as decomposing mats emit hydrogen sulfide. The data help coastal communities prepare for potential shoreline impacts.

The phenomenon, first noted in 2011, reflects changing ocean currents and winds, shifting Sargassum from the North Atlantic’s Sargasso Sea into tropical waters. Continuous satellite tracking remains the only way to capture the belt’s basin‑scale extent and guide regional response efforts.