Great Atlantic Sargassum Belt is World's Largest Seaweed Bloom

Posted on July 5, 2019

Sargassum seaweed accumulated on Delray Beach, FL

The Great Atlantic Sargassum Belt (GASB) is the world's biggest seaweed bloom and it may become permanent. The mass reaches from West Africa to the Gulf of Mexico. Scientists led by the USF College of Marine Science using NASA satellite observations determined the GASB has a biomass of over 20 million tons, heavier than 200 fully loaded aircraft carriers.

The image above shows sargassum decaying on Delray Beach in South Florida in May 2019.

Scientists have linked the growing belt to nutrients discharged from the Amazon River that may have increasing in recent years because of increased deforestation and fertilizer use. However, additional research is needed to confirm this theory.

Dr. Chuanmin Hu of the USF College of Marine Science says in a statement, "The evidence for nutrient enrichment is preliminary and based on limited field data and other environmental data, and we need more research to confirm this hypothesis. On the other hand, based on the last 20 years of data, I can say that the belt is very likely to be a new normal."

The seaweed bloom has become an annoying presence on some coasts.It rots on the beach and releases smelly hydrogen sulfide gas. It can also smother corals and native seagrasses when it dies and sinks to the ocean bottom.

GASB Quick Facts The presence of the seaweed in the Sargasso Sea was reported by Christopher Columbus in the 15th century. The researchers say in a report that 2011 may have been a tipping point for the massive bloom. This was when it started exploding in places in had not been seen before, like the central Atlantic Ocean.

The researchers say, "In 2011, Sargassum populations started to explode in places it hadn’t been before, like the central Atlantic Ocean, and it arrived in gargantuan gobs that suffocated shorelines and introduced a new nuisance for local environments and economies. Some countries, such as Barbados, declared a national emergency last year because of the toll this once-healthy seaweed took on tourism."

Brian Lapointe, a research professor and oceanographer with Florida Atlantic University's Harbor Branch Oceanographic Institute, tells Travel Weekly that sargassum gases can create toxic air and kill sea turtles: "The masses are heavy, hard to remove and can stand in piles as much as 10 feet high. When layers of sargassum are trapped in coves, the air can become very toxic. No one wants to walk on a beach or swim in water that's choked by this seaweed. It can kill sea turtles as they try to come ashore to lay eggs and it's causing problems for the juveniles as they try to make their way from the beaches to the shore."

An article about the sargassum belt findings was published in the journal, Science. The image below shows how the GASB has modified and expanded since 2011.

Great Atlantic Sargassum Belt Annual Changes since 2011


Image Credits: Top Image: Sargassum on Delray Beach in South Florida in May 2019. | Bottom Image: USF College of Marine Science