In May, a record-breaking amount of sargassum blanketed the Caribbean and surrounding regions, with predictions of more in the following month, as highlighted by a recent study. This brown, spiky seaweed is impacting shorelines from Puerto Rico to Guyana, wreaking havoc on tourism, devastating wildlife, and emitting harmful gases that led to the temporary closure of a school in Martinique.
The mass of sargassum — totaling 38 million metric tons — is the largest recorded since scientists began monitoring the Great Atlantic Sargassum Belt in 2011, according to Brian Barnes, an assistant research professor at the University of South Florida. The previous high was 22 million metric tons, recorded in June 2022. “The peaks just seem to keep getting bigger and bigger year after year,” Barnes remarked, though the exact reasons remain elusive.
There are three varieties of sargassum in the Caribbean and adjacent regions, which multiply asexually and float due to small air sacs. They thrive based on sunlight, water temperature, and nutrients — factors currently under scrutiny by researchers like Barnes. Agricultural runoff, climate changes, and wind and water current shifts might also play a role, scientists suggest.
While sargassum in open waters supports marine life such as shrimp and turtles, its presence near shores can be damaging. It obstructs sunlight crucial for coral reefs and, if it sinks, can suffocate marine ecosystems. Once beached, the seaweed becomes a foul-smelling nuisance, impacting tourism, a vital economic driver for small islands. “It is a challenge, but it’s certainly not affecting every single inch of the Caribbean,” said Frank Comito, an advisor with the Caribbean Hotel and Tourism Association.
Efforts to manage the situation vary; Punta Cana in the Dominican Republic has installed barriers to prevent sargassum from reaching shorelines. In St. Maarten, Dutch Caribbean crews deployed backhoes for a cleanup after residents complained of odors affecting the respiratory system. French Caribbean authorities plan to use advanced vessels to clear tons of seaweed daily. However, these solutions can be costly, with some regions preferring manual cleanup to protect local wildlife.
For many islands, financial constraints mean cleanup often falls on hotels, with some offering guests refunds or shuttles to clear beaches. Sargassum blooms typically expand in late spring, peak in summer, and decline by autumn or winter. Nonetheless, this year’s record amount isn’t static; experts project more growth in June.