Sargassum: The Good, the Bad and the Smelly

Sargassum is breaking down near Coki Point, seen above, and Margaritaville, and creating a serious smell. (Photo by Alain M. Brin, Blue Glass Photography)
Sargassum is breaking down near Coki Point, seen above, and Margaritaville, and creating a serious smell. (Photo by Alain M. Brin, Blue Glass Photography)

You don’t have to see it to know it’s here. The brown sea grass called Sargassum has made a grand entrance into the territory. And it smells.

It started as a nuisance in 2011 when the volume grew considerably. Seven years later, the combination of global warming, pollution and hurricanes formed the perfect conditions for it to grow and prosper. When it gets to land and decomposes, the sulfur-like stench can be overwhelming.

Like many other scientists, Tyler Smith, a marine biologist at the University of the Virgin Islands, is eager to find out the secrets of these floating islands.

“The tremendous amount of grass that has entered our waters seems to have come up from the coast of Brazil and from the Sargasso Sea, a two-million square mile area at the Bermuda Triangle,” Smith said.

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This sea without borders is confined by the North Atlantic Gyre, a set of currents that move water around the ocean.

“An estimated 10 million tons of grass, sometimes three to five feet thick, is gathered in this location,” Smith said, adding that scientists believes “the trifecta of warmer waters, pollution and storms conspired to increase the volume and send much of it our way. It is the most we’ve ever seen.”

Sargassum is nothing new. Christopher Columbus is said to have sailed through the thick of it in 1492. Until recently, it was simply a minor feature among the flotsam of the sea.
The situation today gives marine biologists the opportunity to study the grasses in depth and its effect on coral.

“Our post-hurricane monitoring is ongoing at 32 sites from 19 to 220 feet (in depth) and it is our best look at coral ever. The good news is that it is unlikely to harm our corals, perhaps excepting some small, shallow coves,” Smith said. “Our colonies at 100 plus feet are surprisingly healthy. The large reef we study in Brewers Bay is thriving. The storms have lowered the deep water temperatures and that will hopefully be a boost to the coral and a bust to hurricane formation.”

Marine scientist Blair Worthington compared the sargassum and ocean to their seeming opposite.

“The open sea is like a desert and Sargassum is an oasis in that desert,” Worthington said.

The grass provides food, refuge and breeding grounds for turtles, sea birds and crabs and is a nursery for Mahi-Mahi. This habitat available because it floats at the surface thanks to the small, gas-filled “berries” that adorn the branches.

Another benefit is its use in pharmaceutical research (it has been used in Chinese medicine since the 8th Century) and as an important ingredient in biofuel. The grass also helps in the formation of dunes by catching and holding blowing sand.

On the negative side, Sargassum often carries bacteria that can cause irritation in allergic humans, and might be a support system for the invasive species of lionfish. The prolific intruders decimate the local reef fish. Their population is being held in check by the human harvesters who target the species and offer them for sale to restaurants. The lionfish is gaining repute as a delicacy for its tasty white flesh, similar to the butterfish.

The grass should have no effect on ciguatera, the toxin found in small reef fish. Incidents of fish poisoning in the territory have remained at approximately 12 cases per thousand for several years.

Finally, the last but not least negative is its dizzying smell of rotting fish.

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