Almost every summer since 2011, brown waves of seaweed have made their way towards the Caribbean. Once the masses arrive, they linger: choking inlets and bays, piling up on beaches and, eventually, rotting in long rows.
The British Virgin Islands is not immune to the seasonal invasion.
In recent years, the BVI has grappled with large quantities of this variety of macroalgae, or seaweed, called sargassum. Mountains of the seaweed have found a home on virtually every island, clogged boat engines in marinas, and often mingled with trash and other debris to form a thick clot in Road Harbour.
Despite wreaking havoc more recently, sargassum isn’t inherently bad. Floating mats of the seaweed have been spotted and written about by researchers and mariners for hundreds of years. Christopher Columbus, for one, reported seeing sargassum in the 15th century in the middle of the North Atlantic: an area dubbed the Sargasso Sea after the large masses of sargassum that have long accumulated there.
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Sargassum in normal proportions also provides a floating safe haven for sea turtles, shrimp, crabs, fish and other organisms. One species, the sargassum fish, lives among the beds of seaweed and has weed-like appendages that allow it to blend seamlessly into the algae.
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Eight years ago, though, things started to change. Islands across the Caribbean region began to see an unprecedented influx of sargassum arrive on their shores.
Enter the “Great Atlantic Sargassum Belt.” The great belt, a name given by Mengqiu Wang and her colleagues from the University of South Florida, is a long, chain-like smattering of seaweed that has been spotted in satellite imagery since 2011. Wang and her team found that the massive belt can sometimes extend all the way from the Gulf of Mexico to West Africa. Last June, it contained over 20 million tons of seaweed.
“This represents the world’s largest macroalgal bloom,” the team wrote in a report for the journal Science. “Such recurrent blooms may become the new normal.”
But why the amount of sargassum exploded when it did is still up for some debate.
Wang and her colleagues determined that the particularly large sargassum bloom of 2011 could have been caused by more water being discharged by the Amazon River, therefore flooding the Atlantic with fertilizer and prompting the seaweed to flourish. After 2011, the increase of sargassum could have been driven by upwelling – or cold seawater being moved towards the surface of the ocean – off West Africa during winter, and by the Amazon during spring and summer.
Living with Sargassum
If the past eight years are any indication, sargassum will continue its annual migration to the Caribbean. Those who live there are then forced to find creative solutions to the problem.
Once the algae settles on the sand and starts to decompose, it emits a potent odour that keeps visitors away. Often, workers are hired to rally against the mounds of seaweed that accrue on popular beaches with rakes, backhoes and nets. Many Caribbean nations have no choice but to send the huge heaps of seaweed to a landfill after removing it from beaches.
But moving sargassum with heavy machinery also poses potential issues for sea turtles, which nest and lay their eggs along the sandy edges of beaches. This month, special permits had to be obtained before crews could use bulldozers to rid Miami Beach of sargassum, including a guarantee from officials that baby turtles wouldn’t be harmed in the process.
Some in the private sector have tried to find new, innovative uses for sargassum.
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In 2016, Sir Richard Branson hosted a two-day sargassum conference on Moskito Island, inviting entrepreneurs and leaders from around the region to participate. Attendees at the conference discussed existing sargassum research and suggested various ways that the seaweed could be used for fertilizer and fuel.
“Sargassum is most useful when it is out at sea. But when it hits the shore in large quantities it clogs the beach up, stops baby turtles reaching the ocean and has very negative effects on other marine species,” Sir Richard wrote in a blog post for Virgin Unite, his non-profit foundation, at the time.
On an individual level, there are other ways to put sargassum to good use.
This past March, Jean Bonhotal and Mary Schwarz from the Cornell Waste Management Institute showed students how to make their own compost, rich with micronutrients, during a lecture series held across the BVI. One compost was made with more conventional materials – coffee grounds, banana peels, eggshells – and sargassum. Sam Brown of Tidal Roots Farm in Tortola is also experimenting with the seaweed as fertilizer for the organic farm operation.
The prominent – albeit unattractive – weed does serve a purpose (at sea), and island dwellers are getting creative in ways to adapt to this new way of Caribbean living.
Amanda Ulrich
Latest posts by Amanda Ulrich (see all)
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