Waves of sargassum mixed with flotsam and jetsam, Belize, April 2022 (W. Tilt photo)
Numerous news channels have recently reported on the near-record amounts of seaweed smothering Caribbean coasts from Puerto Rico to Barbados, killing fish and other wildlife, choking tourism and releasing stinky, noxious gases.
More than 24 million tons of sargassum blanketed the Atlantic in June, shattering the all-time record, set in 2018 according to the University of South Florida’s Optical Oceanography Lab. And unusually large amounts of the brown algae have drifted into the Caribbean Sea.
Scientists say more research is needed to determine why sargassum levels in the region are so high, but the United Nations’ Caribbean Environment Program said possible factors include a rise in water temperatures as a result of climate change, and nitrogen-laden fertilizer and sewage that nourish the algae.
“This year has been the worst year on record,” said Lisa Krimsky, a university researcher with Florida Sea Grant, a program aimed at protecting the coast. “It is absolutely devastating for the region.”
She said large masses of seaweed have a severe environmental impact, with the decaying algae altering water temperatures and the pH balance and leading to declines in seagrass, coral and sponges.
Experts first noted large amounts of sargassum in the Caribbean Sea in 2011, and the problem has occurred practically every year since then.
Sargassum in moderation helps purify water and absorb carbon dioxide and is a key part of the habitat for fish, turtles, shrimp, crabs and other creatures. It is also used in fertilizer, food, biofuel, construction materials and medicinal products. But it is bad for tourism and the environment when too much accumulates just offshore or on beaches.
For more information on sargassum read The “Massive influxes of Pelagic Sargassum in the Wider Caribbean Region” fact sheet describing the science, law and policy, and management challenges of Sargassum. The project was facilitated by the National Sea Grant Law Center and the NOAA Center for Coastal and Marine Ecosystems, and the Harte Research Institute for Gulf of Mexico Studies at Texas A & M.