Great Atlantic Sargassum Belt



The Great Atlantic Sargassum Belt is a mass of Sargassum in the Atlantic Ocean, and is the largest macroalgae bloom in the world.

History
This Sargassum was first reported by Christopher Columbus in the 15th century but recently appeared in 2011 in the Atlantic.

As of 2023, the belt is estimated to weigh about 5.5 million metric tonnes and extends 5,000 miles, stretching from West Africa to the Gulf of Mexico.

"“I try to shy away from the term blob. That’s not really what it is,” says Barnes, who says that the Great Atlantic Sargassum Belt is really a series of many small blobs with individual patches that are as large as an acre. Smushed together, he adds, it would be roughly the size of Delaware."

- National Geographic, March 2023



Effects
Due to the smell, the attracted insects, and the sheer amount of it piling up on beaches, the Sargassum Belt has a negative impact on communities in the Caribbean, and West Africa. When the Sargassum dies after about 48 hours on land, it releases hydrogen sulfide, a toxic gas. The sulfide can irritate eyes, nose and throat and has a smell akin to that of rotting eggs. The sulfide also can affect people with respiratory problems, including asthma. In 2022, the largest bloom on record was recorded, causing Guadeloupe to issue a health alert, as well as the US Virgin Islands issuing a state of emergency, requesting help from FEMA.

By June 2023 clumps of Sargassum had begun reaching Florida, prompting marine biologists at the Florida Atlantic University Harbor Branch Oceanographic Institute to issue a warning against the presence of Vibrio bacteria on the algae. The bacteria stick to plastic debris that gets tangled in the algae, risking both wildlife and humans.

Cause
The buildup of Sargassum is caused by nutrients flowing into the Atlantic from water discharged by the Amazon and upwelling currents off West Africa. The Sargassum Belt, while in the Sargasso Sea, is different, composed of different morphological types of Sargassum. The Sargassum Belt has also been found to possess lower biodiversity than the Sargasso Sea and is mainly composed of more highly nutrient-efficient organisms.

The Sargassum Belt forms in the North Atlantic Gyre as currents push the material into one mass, similar to the North Atlantic garbage patch.