A singular marine phenomenon begins to generate concern in Mexico and the State of Florida. An 8,000 km long mass of algae, known as the Great Atlantic Sargassum Belt, was detected in the Atlantic Ocean and is expected to reach the Caribbean coast in the coming months.
The episode is unique because the biomass, which stretches from West Africa to the Gulf of Mexico, contains scattered patches of open-ocean algae, rather than a continuous patch of sargassum.
It is not a new phenomenon, but satellite images captured in February show that this large accumulation in the open sea has started earlier than usual.
Once ashore, sargassum is a nuisance: a thick, brown algae that blankets beaches, emits a pungent odor when it decomposes, and entangles people and animals that step on it.
For hotels and resorts, beach cleaning can be a 24-hour-a-day operation.
What is sargassum?
It is a leafy brown algae adorned with what look like berries. It floats in the open sea and, unlike other algae, it reproduces on the surface of the water thanks to air-filled structures that give it the ability to float.
Sargassum originates from a vast stretch of the Atlantic Ocean called the Sargasso Sea, located off the southeast coast of the US. This sea has no land boundaries, but is bounded by four dominant ocean currents.
A mass of accumulated sargassum washes up on Florida beaches. Photo: AP
According to the National Oceanic and Atmospheric Administration, brown algae stretches for miles across the ocean, serving as a breeding ground, food, and habitat for fish, turtles, and seabirds.
“It’s a dynamic and constantly changing set of pieces of this great mass,” said Rick Lumpkin, director of NOAA’s Division of Physical Oceanography. “It’s not one large continuous blob heading directly into southern Florida.”
Sargassum piles up on beaches, where it decomposes quickly in the sun, releasing gases that smell like rotten eggs.
A group of tourists in the middle of an accumulation of sargassum on the beaches of Cancun. Photo: REUTERS
Why is it a problem?
In recent years, sargassum has washed up on the beaches of some Caribbean islands and the Mexican Yucatan peninsula during the spring and summer months.
Coastal towns and cities, as well as hotel chains, have been hard-pressed to cope with the huge amounts of seaweed washing up on shore.
What is happening now?
According to Chuanmin Hu, a professor of oceanography at the University of South Florida, some of the sargassum has already washed up on the beaches of Key West. But most of it will arrive in summer, completed the academic.
“What is unusual this year compared to previous years is that it has started early,” Hu said. The alga usually blooms in spring and summer, but “this year, in winter, we already have a lot.”
South Florida, the Caribbean and the Yucatan Peninsula typically see sargassum build up in the summer months and could expect the same this year, Hu said.
Sargassum can be dangerous for people with respiratory problems, since it releases toxic gases after spending many hours in the sun. Photo: AP
Is it normal for this amount of sargassum to appear?
It’s a large number, but there have been worse years.
Scientists estimate that there are more than 10 million metric tons of sargassum in the belt this year. Lumpkin called it “one of the strongest years, but not the strongest” since scientists began taking a close look at biomass via satellite imagery in 2011.
He said there was more in 2018. The years 2019 and 2021 also saw a lot of sargassum, he said.
Why is sargassum generated?
Scientists aren’t quite sure, in part because this phenomenon didn’t begin to be closely studied until 2011.
“We know that for a lot of algae to grow, you need nutrients and sunlight. Of course, as you get closer to the equator, there’s going to be more sunlight,” explained Mike Parsons, a professor of marine sciences at the University of the Coast of the Florida Gulf.
Parsons and other experts say that agricultural runoff (rainwater) seeping into the Amazon and Orinoco rivers, and eventually into the ocean, could explain the greater growth of the belt on the western side.
According to Parsons, warming the waters can accelerate the growth of algae. Changes in wind patterns, ocean currents, precipitation, and drought could also affect blooms.
“It’s possible that the entire belt feeds more in some years than others due to dust containing iron and other nutrients from the Sahara desert,” NOAA’s Lumpkin explained.
It is not clear if climate change has something to do with it. According to Hu, extreme weather events — strong winds, storms, more precipitation — occurring more frequently due to climate change could contribute to this.
Can sargassum be dangerous to humans?
It can be. When sargassum decomposes, it releases ammonia and hydrogen sulfide, which are responsible for the rotten-egg stench.
According to scientists, brief exposure is not enough to make someone sick, but prolonged exposure, especially for people with respiratory problems, can be dangerous.
Hu says it could be a problem for hotel workers and others who spend hours removing decomposing sargassum from beaches.
If left to rot on the beach, sargassum can become a problem. It can damage coastal marine ecosystems and also favors the growth of fecal bacteria.