A record-breaking amount of sargassum seaweed piled up across the Caribbean in May, with experts warning that even more is expected this month. The brown, prickly algae is inundating shorelines from Puerto Rico to Guyana, disrupting tourism, killing wildlife, and releasing toxic gases that have caused health concerns.
Scientists report that an unprecedented 38 million tonnes of sargassum were observed across the Caribbean Sea, the western and eastern Atlantic, and the Gulf of Mexico. This is the largest amount recorded since the Great Atlantic Sargassum Belt was first studied in 2011. The previous record was set in June 2022 with 22 million tonnes.
While the exact cause of this surge remains unclear, researchers are investigating factors such as agricultural runoff, warming ocean temperatures, and changes in wind, currents, and rainfall patterns. Sargassum thrives in different conditions depending on sunlight, nutrients, and water temperature.
In open waters, sargassum provides a vital habitat for marine life, from tiny shrimp to endangered sea turtles. However, when it accumulates near shorelines, it can cause significant problems. The algae can block sunlight needed by coral reefs, and if it sinks, it can smother reefs and seagrasses. On beaches, decaying sargassum produces strong odors and emits gases like ammonia and hydrogen sulfide, which can affect people’s respiratory systems.
The influx of seaweed is a major concern for Caribbean nations, many of which rely heavily on tourism. In Punta Cana, a popular destination in the Dominican Republic, officials have installed barriers to prevent sargassum from reaching the beaches. On the island of St. Maarten, emergency clean-up crews have been dispatched to remove the algae. In Martinique, a school had to temporarily close due to the toxic gases released by decaying sargassum.
Cleanup efforts are challenging and costly. Some islands lack the resources to tackle the problem effectively, leaving hotels and local businesses to manage the situation. The seaweed season typically peaks around summer and declines in late fall, but with the new record set in May, communities are bracing for a challenging few months ahead.
“We’re expecting even more sargassum to arrive in June,” experts say, urging residents and visitors to be prepared for the impact.
