Rotting Mass Of Sargassum Seaweed Threatens Beaches

A 10-million-pound blob is riding ocean currents toward Florida’s tip. The Great Atlantic Sargassum Belt, a 5,000-mile-long goopy mass of green, floating seaweed, is meandering its way through Florida and into the Caribbean.


It may be an oasis in the vastness of the ocean. Passing fish and sea turtles may find refuge and food in the patches of seaweed.

Sargassum was once a natural element of the ocean ecology, but over the last decade, it has evolved into a nuisance capable of causing considerable damage—and a rotten, stinky one at that. Here’s what we know about where it comes from—and if you need to worry about it.

Sargassum is a golden-hued seaweed, a big macroalgae that is constantly swept by the ocean currents. Unlike other species of seaweed, such as kelp, which is attached to the shallow ocean floor, sargassum is suited to open sea life and only exists in floating patches.

Most of it may be found in the Sargasso Sea in the western Atlantic, which is such an essential ocean home for so many marine animals that it has been dubbed the “golden floating rainforest.”

The Sargasso Sea, located entirely within the Atlantic Ocean, is the only sea without a land boundary, being instead defined by currents.

Sargassum has been around for roughly 30 million years, but huge blooms of this scale are a growing problem. Pollution is a major contributor to dangerous algal blooms such as red tides, and sargassum is no exception. When farmers spray fertilizer on land, they release nutrient-rich compounds that aid crop growth. As fertilizers leach into rivers and find their way the sea, they unwittingly feed sea plants with the same plant-growing nutrients.

As sargassum accumulates on beaches, it is at best an annoyance for companies that rely on tourists flocking to pristine, seaweed-free beaches plus when it decomposes, it emits a gas known as hydrogen sulfide, which smells like rotten eggs. According to the Florida Department of Health, this gas can irritate the eyes, nose, and throat. Sargassum may also include tiny marine organisms, such as jellyfish, which can irritate the skin.

Excessive seaweed can also hurt the ecology. The dense, tangled mass may suffocate coral reefs and mangroves, as well as small terrestrial organisms like crabs and clams. There is currently no straightforward way to get rid of sargassum, and cleanup can cost tens of millions of dollars.

Reference – National Geographic, INVERSE, Horizon, BBC Earth, Discovery Magazine