A giant "blob" of sargassum seaweed measuring 5,000 miles wide — twice the width of the continental United States — is headed for the Florida coast and already covering beaches with algae that will begin to smell as it decomposes.
Sargassum is a type of seaweed algae that floats in island-like masses without ever attaching to the seafloor. According to the National Oceanic and Atmospheric Administration, it functions as a floating habitat providing food, shelter and breeding grounds for many different types of sea animals.
Chuanmin Hu, a professor of optical oceanography with the University of South Florida, said the mass of seaweed, or “mat,” making its way toward Florida is not so much a “blob” but more of an “elongated belt.”
“There is not a single source, but sargassum is a natural plant in the Atlantic Ocean so it can grow in the entire tropical Atlantic,” Hu explained in an email to Yahoo News.
"Most beaches on the west coast of Florida will be spared but some beaches on the east coast will receive Sargassum of variable amount."
Once the seaweed begins to rot, it releases a substance called hydrogen sulfide, which gives off an unpleasant odor similar to rotting eggs. While it may be smelly, for the most part sargassum isn’t a health hazard or unsafe for humans — though those with respiratory problems should steer clear.
“Only when too much of the seaweed gets decomposed on the beach or in nearshore waters, then does it become a nuisance for animals and humans. People with respiratory problems don’t want to get close to the rotten, smelly seaweed. But it is not toxic in the ocean,” Hu said.
“For small amounts (e.g., a mat like the size of a room), you can swim around. But for large mats such as a football field, you want to avoid it,” he added.
Florida’s seaweed season runs from March through October, though an expert told the New York Times that this year may be the “biggest year yet on record.” So while sargassum’s presence on beaches should eventually peak and decline, it will inevitably return.
“It will continue to grow until June/July, and then start to decrease until winter. Then next year it will enter another cycle,” Hu said.
But while it may be annoying for beachgoers, rather than disposing of all that seaweed some of it may serve a higher purpose. A local Palm Beach County TV station reported that many cities hire firms to rake the dried seaweed and bury it to strengthen dunes. Natural “beach litter” such as algae and grasses can enhance the growth of dune vegetation when placed near native dune plants.