Sargassum overwhelms South Florida beaches, raising health concerns before World Cup

Large mats of sargassum seaweed have blanketed South Florida shorelines, forming piles up to a quarter of a football field long and emitting a strong, unpleasant odor. The algae decompose within two days, releasing hydrogen sulfide and ammonia, which can irritate the respiratory system, worsen asthma, and cause nausea, headaches, or neurological effects. Contact with the seaweed may also lead to skin rashes, blistering puncture wounds from stingrays, and bacterial infections, especially for beachgoers with open cuts.

The buildup arrives as the region prepares for the 2026 FIFA World Cup, a major draw for tourists. NOAA’s risk map rates Miami‑Dade County at high risk for continued sargassum influx through June‑August, and local officials warn that the odor and health hazards could dampen beach tourism and pose additional risks to visitors.