Huge masses of foul-smelling seaweed in the Caribbean could cause headaches for sun-seekers

Every winter, millions of Canadians head to the Caribbean in search of sunshine, clean beaches and clear waters.

But this year, tourists may have noticed something unpleasant on the beach: the smelly brown sargassum.

Over the past decade, foul-smelling seaweed has become more common on beaches around the Caribbean and the southern Atlantic Ocean. So what happened? To understand, first you need to understand sargassum.

What is sargassum?

Sargassum is a type of brown seaweed (and a form of algae) found in the Atlantic Ocean. It is made from pieces of leaves, as well as round berry-like pieces that are filled with oxygen that help them float on the surface. No roots or seeds.

Unlike some other types of seaweed, it lives entirely on the surface of the sea in small pieces. Sargassum is usually found in areas called Sargasso Seawhere it tends to circulate in a vortex called a gyre, over five million square kilometers of belt that runs from the Chesapeake Bay in the mid-Atlantic, all the way to the Caribbean.

However, sargassum can clump together, creating a raft or patch. It has a seasonal cycle, starting in the spring, reaching its peak in the summer, and finally dying down in the fall.

Sometimes large collections can wash up on the shore, which can be a nuisance for beachgoers. But it is important for some marine life, providing food and breeding for animals such as fish, sea turtles and others.

“[Sargassum] have formed huge floating masses in the open sea, which is very good, actually … because they absorb carbon, absorb nutrients, save life, and many animals depend on them, “said Brigitta Ine van Tussenbroek. , scientist at the Institute Marine Sciences and Limnology National Autonomous University of Mexico.

“Even the American eel, the Northern European eel, they wouldn’t exist without the Sargasso Sea, for example. So it’s a wonderful system.”

Is it an increase?

While most sargassum usually stays in this gyre, it can travel along a sort of conveyor belt in the Atlantic and the Caribbean. Scientists have seen an increase in sargassum along the Caribbean coast since 2011..

“Sometimes, some of these gyres… slackened, and some of the sargassum escaped and then went to Cuba, to Hispaniola, and some ended up in Mexico passing to the Gulf of Mexico. And then back to the Sargasso Sea,” van Tussenbroek said.

“Since 2010-11, suddenly, some sargassum began to accumulate in a new area, which is north of the equator in the tropical Atlantic.”

Why is this happening? Scientists aren’t sure.

Several factors may be at play, including climate change and human activity, van Tussenbroek said.

Chuanmin Hu, a professor at the University of South Florida who studied the flower Sargassum Watch System (SaWS), says that most of the nutrients come from the dust of the Sahara Desert that crosses the Atlantic Ocean.

But there is also an upwelling of the sea, he said, where water from deep below the sea is brought to the surface, and along with it, more nutrients, which further support these blooms. And, scientists believe that with a climate change, possibly ocean upwelling. Also, nutrients flow into the Atlantic from the Congo River in Africa and the Amazon River in South America.

“Now the question is, who is dominant?” He said. “We just don’t know. It’s hard to quantify the contribution.”

What is the situation this year?

According to SaWS, January is the second month in a row in which sargassum doubled, the last time it happened in 2018. Although it decreased in February, the confidence will continue to grow and make its way along the coast of the Caribbean countries. Last year saw the most sargassum on record.

But so far, this year has been impressive, Hu said, adding that in December SaWS predicted that 2023 could be another record year, although there were no guarantees.

“All we can say is it’s going to be another major year.”

How much does it cost?

As of January, there were more than eight million metric tons of sargassum in the Atlantic Ocean, Hu said. In February, that dropped to between six and seven million metric tons. But Hu said there could be even more in March.

“Now they are scattered here and there with low density. Even in the belt, the density is less than 0.1 percent,” said Hu. “But if someone could put all the sargassum in one place, how big would this be? About, roughly, 3,000 square kilometers, without gaps.”

What are some of the effects of a large bloom?

It’s the big blooms that scientists have been seeing since 2011 that are causing problems. First, hotels and cities must swallow the costs of removing the masses, to protect the lucrative tourism industry.

Then, there are concerns about ecosystems.

The abundance of sargassum can threaten the delicate coastal ecosystem, as well as shrinking coral reefs, reducing their cover and roughness, which makes them more vulnerable to waves and less protection from hurricanes. It can also prevent turtle hatchlings from reaching the sea.

The good news is that there may be several uses for sargassum mass, including use as biofuel or even as a building material.

Should I be worried?

If you are going to the beach and encounter such a mass, there is no immediate concern, although the smell of decay can be unpleasant. And it can spoil the snorkeling or swimming at the beach that you want to enjoy.

“What I want to say now, you know to tourists, don’t panic,” Hu said. “This is a natural, non-toxic plant, if you have too many of them, if [it decomposes]it can be dangerous, but it’s usually not toxic,” Hu said.

“And also most of the time, even if they collect it on the coast, the local people usually remove it. So, if you have travel plans, come to Florida, come to the Caribbean. I will not worry about that.”

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