Giant mass of sargassum nears the Caribbean

WTTC presents basic concepts of hotel sustainability

13-02-23

The mass of brown seaweed in the Atlantic Ocean is so large that it can be seen from space.

Stretching some 8,000 kilometres, roughly twice the width of the United States, the thick layer of sargassum floats between the Gulf of Mexico and the coast of West Africa.

In open water, these giant mats of algae are mostly harmless and even have some benefits, such as providing habitat for certain fish and crustaceans and absorbing carbon dioxide. But ocean currents are pushing the sargassum westward, causing hundreds of tonnes of algae to wash up on the beaches of the Caribbean and the Gulf of Mexico.

There, it can smother corals, wreak havoc on coastal ecosystems and diminish water and air quality as it rots.

Scientists say the bloom is one of the largest on record, raising fears that algal invasions on beaches in the coming weeks and months could be particularly severe.

"It's unbelievable," says Brian LaPointe, a research professor at Florida Atlantic University's Harbor Branch Oceanographic Institute. "What we're seeing on satellite imagery does not bode well for a year of clean beaches."

Sargassum growth varies from season to season. LaPointe, who has studied it for four decades, said huge piles usually come ashore in South Florida in May, but Key West beaches are already inundated with seaweed. Parts of Mexico's Yucatan peninsula, such as Cancun, Playa del Carmen and Tulum, are preparing to accumulate up to a metre of sargassum in the next few days.

According to Brian Barnes, assistant research professor at the University of South Florida's College of Marine Sciences, the giant sargassum mounds are more than just a nuisance and an eyesore.

Last summer, the US Virgin Islands declared a state of emergency after unusually high amounts of sargassum caused water shortages on St. Croix.

Other human health consequences are coming to light. As the seaweed rots, it releases hydrogen sulphide, which can cause respiratory problems for tourists and residents in the vicinity, LaPointe said.

"After the large blooms in 2018, doctors in Martinique and Guadeloupe reported that thousands of people were going to clinics with respiratory complications from the air given off by these decomposing sargassum piles," he explained.

Then there are the economic problems. Sargassum invasions can stifle tourism, and removing hundreds of tons of seaweed from beaches is costly.

Scientists noticed more than a decade ago that sargassum blooms were beginning to grow at a staggering rate. Since then, researchers have documented the proliferation of the algae in the tropical Atlantic.

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