Is a giant blob of seaweed really bringing flesh-eating bacteria to Florida?

Pieces of an absolutely enormous blob of seaweed in the middle of the Atlantic Ocean have been breaking off and making their way to the Florida coast, and some experts are warning they could be bringing a dangerous type of flesh-eating bacteria with them. 

Somewhere out in the no man’s land of the Atlantic Ocean, there is a 5000-mile-long patch of brown seaweed known as sargassum just waiting for the right time to strike the coast of Florida, and it's already sent out a few pieces of itself to muck up beaches. 

"The low season of the cycle is now higher than the high point of the cycle five or six years ago," University of South Florida’s Brian Barnes told NPR in March about the sargassum patch. "What we thought was just a massive bloom has only gotten bigger.”

This latest bloom is just one of a number of massive buildups that scientists have seen forming with alarming regularity since 2011 according to The Guardian. But sargassum just doesn’t make pretty beaches ugly, it can have some serious environmental impacts. 

Sargassum is a type of floating algae according to The Guardian, and it does so through “berry-like bubbles'' that the seaweed fills with oxygen so it can stay buoyant. Once the sargassum reaches shore, it starts to decay and eventually releases hydrogen sulfide. 

In March 2023, PBS News noted that sargassum can be dangerous to humans when it is decomposing because the hydrogen sulfide it releases can make people sick if they are exposed to it for a long period of time. But that’s not what has researchers worried. 

In May, a group of researchers from the Florida Atlantic University published a paper in the journal Water Research that found sargassum, and the tiny pieces of marine plastic that it carries with it could also be accompanied by a lot of dangerous Vibrio bacteria. 

“Our lab work showed that these Vibrio are extremely aggressive and can seek out and stick to plastic within minutes,” explained Florida Atlantic University Professor of Biology Tracy Mincer and the study’s lead author according to a release from the University. 

Mincer continued, saying he didn’t think “anyone has really considered these microbes and their capability to cause infections” and added that he wanted to “make the public aware of the associated risks.” But what risks can come with Vibrio-laden sargassum?

Newsweek reported that Vibrio bacteria and species like the feared Vibrio vulnificus can lead to pretty horrible infections in humans, and in some cases, individuals can develop necrotizing fasciitis—which is why the bacteria has gained a reputation as flesh-eating. 

The Centers for Disease Control and Prevention has said Vibrio vulnificus infections can be extremely life-threatening and estimated that as many as one in five people die from the infection while many more will require some form of amputation to save their lives. 

Luckily, cases of necrotizing fasciitis are extremely rare and Newsweek noted that only 0.4 people in 100,000 are infected with it each year in the United States. Plus, there is evidence suggesting we shouldn’t be too worried about catching flesh-eating bacteria from sargassum. 

Live Science pointed out that while the researchers from Florida Atlantic University did find some species of Vibrio in the sargassum they tested, they didn't find the dangerous Vibrio vulnificus nor Vibrio cholerae—two species known to cause infections in humans. 

"Clearly, the Vibrio can and does colonize both plastic and Sargassum, and it can carry genes that are potentially pathogenic," Linda Amaral-Zettler, an author of the study and Marine Biologist at the Royal Netherlands Institute for Sea Research, told Live Science.

"I don't think people have to go running screaming away from Sargassum, but they do need to be responsible and realize that there are hazards associated with handling and exposing yourself to these kinds of materials,” Amaral-Zettler continued.

Florida Department of Health’s Jae Williams echoed the advice from Amaral-Zettler and told Live Science: "What is important is that individuals should take caution.” Williams urged people not to play in sargassum and said they should “just stay away from it."