The 5,000-mile long bloom, which runs from West Africa to the Gulf of Mexico, weighs about 20 million metric tons.

Researchers have discovered the world's largest seaweed bloom, stretching from West Africa to the Gulf of Mexico.

In a study published Friday in the journal Science, satellite imagery disclosed the 5,000-mile bloom of the brown algae, called Sargassum. As of last month, the mass weighed about 20 million metric tons.

Blooms can be a benefit to some ecosystems by providing habitat and sources of food.

"In the open ocean, Sargassum provides great ecological values, serving as a habitat and refuge for various marine animals," said Mengqiu Wang of the University of South Florida. "I often saw fish and dolphins around these floating mats."

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On the other hand, they can also coat shorelines, smother wildlife and become a nuisance to local economies that rely on beach tourism. When the seaweed washes up on beaches and dies, it releases hydrogen and sulfide gas and smells like rotten eggs, which could present a public health problem, according to researchers. Last year, Barbados declared a national emergency due to the presence of the smelly seaweed on its shores.

Starting in 2011, these blooms began expanding into areas where they previously weren't found. Researchers warn that these massive blooms could be the new normal.

"This is all ultimately related to climate change because it affects precipitation and ocean circulation and even human activities, but what we've shown is that these blooms do not occur because of increased water temperature," said Chuanmin Hu, study author and professor at USF's College of Marine Science. "They are probably here to stay."

They also theorize another big concern could be at play – a change in the ocean's chemistry.

Hu said a change must have happened "in order for the blooms to get so out of hand."

Every year between 2011 and 2018 with the exception of 2013 had a major bloom. Researchers believe increases in deforestation and fertilizer use could be factors fueling blooms.

