Self-sustaining sargassum blooms turn coastal nuisance into lasting challenge

Tourists and residents along the Caribbean, Gulf, and South Florida coasts have increasingly encountered foul-smelling, brown sargassum piles on beaches, a phenomenon that began in 2011 and has intensified each year. The seaweed, originally abundant in the North Atlantic's Sargasso Sea, now forms a massive “Great Atlantic Sargassum Belt” that produced an estimated 37,500 million tons in 2025, with 2026 forecasts pointing to new records.

Scientists found that strong winter winds pushed sargassum southward, while subsequent wind-driven upwelling supplied nutrients that the algae and its associated marine life recycle, creating a self-sustaining bloom cycle. A newly developed model, calibrated with nitrogen measurements from the U.S. Virgin Islands, successfully replicated blooms from 2011-2022 and predicted the 2023-2024 events. Understanding this mechanism enables better forecasting and early-warning for vulnerable communities. Meanwhile, researchers are exploring ways to turn the invasive biomass into renewable biofuels, soil amendments, and low-carbon building products, offering a possible economic upside to the environmental problem.