TAMPA, Fla. (WFLA) — You may have heard about the vast mats of smelly sargassum seaweed washing up along the coast of southeast Florida.
A new study from Florida Atlantic University is uncovering how the seaweed interacts with plastic debris and Vibrio bacteria to create the “perfect pathogen storm” for beachgoers and marine life.
But first, what are Vibrio bacteria — and what health effects can they have on humans?
What are Vibrio bacteria?
According to FAU, varieties of Vibrio bacteria are found in waters around the world and are a leading cause of death in humans from the marine environment.
One type of Vibrio bacteria, known as Vibrio vulnificus, is sometimes referred to as flesh-eating bacteria. Researchers say consuming seafood with this particular Vibrio bacteria can cause life-threatening illnesses.
The Florida Department of Health says Vibrio vulnificus normally live in warm, brackish seawater. Beachgoers with open wounds can easily become exposed through direct contact and be put at risk for disease or even death.
In 2022, FDOH reported 17 deaths and 74 Vibrio bacteria-related infections. It noted the abnormal increase was due to the impacts of Hurricane Ian.
What is creating this ‘perfect pathogen storm?’
Since 2011, scientists have watched as a giant blob of Sargassum has rapidly expanded in the Great Atlantic Sargassum Belt. The growing blob has caused “frequent and unprecedented seaweed accumulation events” on beaches across Florida.
In early 2023, marine scientists tracked a 5,000-mile-wide sargassum bloom so large, it could be seen from space. By April, some of Florida’s most picturesque beaches were covered in piles of the seaweed.
Meanwhile, researchers learned that varying sizes of plastic debris had made their way into the surface waters of the Sargasso Sea, raising worldwide concern.
Samples collected by FAU revealed that Vibrio pathogens had harnessed the unique ability to “stick” to microplastics within the seaweed blob. The findings further showed that some Vibrio bacteria had an ‘omnivorous’ lifestyle that targeted both plant and animal hosts.
“Another interesting thing we discovered is a set of genes called ‘zot’ genes, which causes leaky gut syndrome,” said assistant professor Tracy Mincer, Ph.D.
“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.”
Simply put, the combination of the bacteria and microplastics could be responsible, in part, for the rapid growth of Sargassum.
As coastal communities across the Sunshine State look for solutions to rid their shores of sargassum, researchers say caution should be exercised.
Some cultivation-based data showed that beached Sargassum appeared to harbor high amounts of Vibrio bacteria.
“I don’t think at this point, anyone has really considered these microbes and their capability to cause infections,” Mincer added. “We really want to make the public aware of these associated risks.”