By Cailey Rizzo
July 08, 2019
Credit: Marc Bruxelle/Getty Images

Scientists announced the discovery of the world’s largest seaweed bloom last week, according to Science Magazine.

Using satellite imagery, an international team of scientists has determined that the seaweed bloom stretches more than 5,500 miles across the Atlantic Ocean, from the Gulf of Mexico to West Africa, and is estimated to weigh more than 20 million tons.

The bloom consists primarily of a brown type of seaweed called sargassum. It appeared in the Atlantic Ocean, between Africa and South America, in 2011. Up until then, its appearance in those waters was considered rare. But in the past seven years, the bloom has grown about 10 times its original size.

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Scientists believe the Great Atlantic Sargassum Belt, as it is now known, has grown rapidly due to nutrients from the waters in the Amazon river and the West African coast washing out to sea. They believe that some of this sweep is due to increased deforestation and use of soil fertilizers.

"This is all ultimately related to climate change because it affects precipitation and ocean circulation and even human activities,” Dr. Chuanmin Hu, who led the study, told BBC, “but what we've shown is that these blooms do not occur because of increased water temperature. They are probably here to stay."

Sargassum can provide a rich habitat for certain marine animals but in too high quantities, it can suffocate and kill coral and other seagrasses. When it washes up on shore, it releases a gas (hydrogen sulfide) which many people liken to rotten eggs. Now, the seaweed bloom is washing ashore on Atlantic and Caribbean beaches where it was previously rarely seen.

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There are many factors (like salinity, seed population and surface water temperatures) that could contribute to the growth of sargassum. Scientists will continue monitoring the belt and looking for more potential effects its growth could have on the planet.