Flesh-eating bacteria on Florida beaches? Seaweed-plastic mix causes concern, study shows

2023 biggest year for Sargassum, scientists concur, and Sargassum could bring with it bacteria

The biggest Sargassum bloom is expected for South Florida beaches in 2023 carrying with it bacteria.

PEMBROKE PINES, Fla. – In March, a coastal science professor at Florida International University told Local 10 News that this summer may be the largest bloom of mounds of thick, brown, tangled blobs of seaweed, also known as Sargassum, on beaches in South Florida.

Stephen Leatherman, Ph.D. is sure that the seaweed that’s washed up in previous years is nothing compared to what we’ll see this summer.

NASA scientists are also predicting that this year’s Sargassum seaweed bloom along the Caribbean and eastern Florida coastlines will be the largest ever recorded, with the bulk of it arriving in June and July.

But now, the unsightly, smelly massive bloom can be deadly, too. A new study that included researchers from Florida Atlantic University has uncovered that plastic marine debris when combined with Sargassum, which is a living population of brown macroalga, can become filled with vibrio vulnificus, sometimes referred to as flesh-eating bacteria. The interaction of Sargassum and plastic debris is a breeding ground for a perfect “pathogen” storm, the researchers stated.

“Plastic is a new element that’s been introduced into marine environments and has only been around for about 50 years,” Tracy Mincer, Ph.D., corresponding lead author of the study and an assistant professor of biology at FAU’s Harbor Branch Oceanographic Institute and Harriet L. Wilkes Honors College, told Science Daily. “Our lab work showed that these Vibrio are extremely aggressive and can seek out and stick to plastic within minutes. We also found that there are attachment factors that microbes use to stick to plastics, and it is the same kind of mechanism that pathogens use.”

About a dozen species of bacteria in the genus Vibrio cause vibriosis, an illness that can occur either when people ingest the bacteria or when the microbes infect an open wound. When eaten, the bacteria can cause severe diarrhea, stomach cramps, fever and vomiting. Regarding wound infections, one species of Vibrio can sometimes cause flesh-eating infections, scientifically known as necrotizing fasciitis, which quickly kills the skin around the infected wound.

The genomics study found that the Vibrio pathogens had the ability to stick to microplastics. It was published in the journal “Water Research,” but Mincer said there is still much research to be done.

“I don’t think at this point, anyone has really considered these microbes and their capability to cause infections,” Mincer told Science Daily. “We really want to make the public aware of these associated risks. In particular, caution should be exercised regarding the harvest and processing of Sargassum biomass until the risks are explored more thoroughly.”

Just to be safe, anyone going in the ocean or walking in and around the bulky Sargassum should take precautions. The CDC recommends precautions for flesh-eating bacteria:

  • Stay out of the water if you have a wound (including from a recent surgery, piercing, or tattoo), or cover the wound with a waterproof bandage if there’s a possibility it could come into contact with salt water.
  • Wash wounds and cuts thoroughly with soap and water if they have been exposed to seawater.
  • If you develop a skin infection, contact a medical professional and tell them if your skin has come into contact with salt water.

Mincer also explained that the team of researchers discovered a set of genes called “zot” genes, which was first discovered in the bacteria Vibrio cholerae, which can cause cholera, and which is usually rare in the United States and other industrialized nations. But the discovery of these “zot” genes, which cause leaky gut syndrome, are also being found when the plastic and Sargassum mass interact.

“For instance, if a fish eats a piece of plastic and gets infected by this Vibrio, which then results in a leaky gut and diarrhea, it’s going to release waste nutrients such nitrogen and phosphate that could stimulate Sargassum growth and other surrounding organisms,” said Mercer.

The bottom line from the study shows that with increased interaction with human-Sargassum-plastic debris interaction, opportunities are created for pathogens to develop. The journal study said that data showed beached Sargassum “appear to harbor high amounts of vibrio bacteria.”

Experts say there was a big uptick of seaweed in 2014, 2019, and now get ready for the Sargassum bloom in 2023 to be the largest ever recorded.

Many municipalities throughout South Florida have clean-up crews clearing the seaweed from beaches each morning.

(See the study below)

About the Author:

Michelle F. Solomon is a multi-platform producer/reporter for Local10 and is the podcast producer/reporter/host of the station's original, true-crime podcast The Florida Files and producer of Local10.com's DigiShorts.