The Sargasso Sea Is Plenty Wide, and It’s Growing
Atlas Obscura 4/14/2020
Sargassum is the umbrella term for a group of marine algae species—within a larger group called seaweed—that’s fundamental to the health of an entire region of the Atlantic and the many species who either live there or pass through. Sometimes, though, it explodes in growth, creating a continent-sized bloom that thoroughly freaks out multiple countries. These blooms have long happened and are perfectly acceptable if they happen rarely. They have not been happening rarely.
There were huge blooms in 2011, and then 2014, 2015, and 2017. In 2018 and 2019, the blooms were much bigger than they had been before 2011.
“When you have a very large quantity of sargassum, either on the beach or in coastal waters, then you have a problem,” says Hu. Hu’s team tracked this washed up sargassum to a strip they’re calling the Great Atlantic Sargassum Belt, a larger area than the Sea, stretching all the way from West Africa to the Caribbean and the Gulf of Mexico. Sargassum has always lived in these areas outside the Sargasso Sea, but never before in these quantities. Since 2011, it’s all become an essentially uninterrupted, massive strip—tens of millions of tons of seaweed that weren’t there before. Excess sargassum can cause any number of problems. The algae floats when the mats are alive, but when they die, they sink. That can lead to suffocating blankets coming to rest atop delicate ecosystems such as coral reefs. Even worse, bacteria in decomposing sargassum suck oxygen out of the environment.