Sargassum kelp on its way to Florida explained

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A giant seaweed patch twice the width of the continental United States is headed for the coast of Florida and other coastlines throughout the Gulf of Mexico, threatening to dump smelly and possibly harmful mounds on beaches and dampening the tourist season.

Sargassum – the specific variety of seaweed – has long formed large blooms in the Atlantic Ocean, and scientists have been tracking massive accumulations since 2011. But this year’s bloom may be the largest ever, spanning more than 8,047 kilometers from the coast of Africa to the Gulf of Mexico.

This year’s sargassum bloom started forming early and doubled in size between December and January, said Dr. Brian Lapointe, a researcher at Florida Atlantic University’s Harbor Branch Oceanographic Institute. The mass “was bigger in January than it’s ever been since this new region of sargassum growth began in 2011,” he told CNN International’s Rosemary Church.

Heading west, the blob will push through the Caribbean and up into the Gulf of Mexico during the summer. The seaweed is expected to show up on Florida beaches around July, Lapointe said.

“This is a completely new oceanographic phenomenon that is creating such a problem – really a catastrophic problem – for tourism in the Caribbean region, where it’s piling up on beaches up to 5 or 6 feet deep,” Lapointe said.

Here’s what you should know about why these masses happen and how they affect both humans and marine life.

Sargassum is an umbrella term that can be used to refer to more than 300 species of brown algae, although Sargassum natans and Sargassum fluitans are the two species most commonly found in the Atlantic Ocean.

When the algae drift in the ocean, they can have benefits for marine life.

“This floating habitat provides food and protection for fish, mammals, seabirds, crabs and more,” according to the Sargassum Information Hub, a joint project between various research institutions. “It serves as a critical habitat for endangered sea turtles and as a nursery area for a number of commercially important fish such as mahi mahi, jacks and amberjacks.”

The problems with sargassum occur when it hits beaches, piles up in piles that can be difficult to navigate and emits a gas that can smell like rotten eggs.

Sargassum can also quickly turn from a resource to a threat to marine life.

It comes in such “large amounts that it basically sucks the oxygen out of the water and creates what we refer to as dead zones,” Lapointe said. “These are usually nursery habitats for fisheries … and once they’re deprived of oxygen, we’ve lost that habitat.”

Sargassum can also be dangerous to humans, Lapointe added. The gas released from decaying algae – hydrogen sulphide – is toxic and can cause respiratory problems. The seaweed also contains arsenic in its flesh, which makes it dangerous if swallowed or used for fertiliser.

“You have to be very careful when you clean the beaches,” Lapointe said.

Just like plants and crops on the ground, the spread of seaweed can shift from year to year depending on ecological factors, influenced by changes in nutrients, rainfall and wind conditions, said Dr. Gustavo Jorge Goni, an oceanographer at the National Oceanic and Atmospheric Administration’s Atlantic Oceanographic and Meteorological Laboratory .

Ocean currents also influence sargassum growth and how much it accumulates, Goni added. Phosphorus and nitrogen in the sea can serve as food for the algae.

These elements can be dumped into the ocean from rivers, which receive concentrations of phosphorus and nitrogen from human activities such as agriculture and fossil fuel production, according to the US Environmental Protection Agency.

For now, researchers are looking at ways to prevent the seaweed’s impact on beaches, possibly by sinking it to the bottom of the ocean or harvesting it for use in commercial products like soap, Goni said.

Goni cautioned that research into these sargassum assemblages is new, and it is likely that scientists’ understanding of how the algae grow will change over time.

“What we think we know today,” he said, “may change tomorrow.”

Before traveling to coastal areas this spring or summer, research whether sargassum is at your destination or may appear there, Lapointe said. Plan ahead so your vacation won’t disappoint.

There are sargassum Facebook groups, with members posting about what they recently saw on the beaches, Lapointe said.

“It has already affected the travel industry,” he said.

Tourists enjoy the beach despite a build-up of sargassum algae in Cancun, Mexico, in May 2021.

Unfortunately, sargassum can build up overnight, so you might not be able to predict the effect on a trip, Lapointe said.

“This is why we’re trying to work with these early warning systems – high resolution in coastal areas, which requires higher resolution satellite imagery to do a better job of showing what’s actually coming onto a beach in the next 24 or The 48 hours,” he added.

Satellite images from the past week show that sargassum is not an amorphous mass moving across the ocean, but rather drop-shaped blobs followed by long, thin strands of seaweed.

Over the past week, sargassum blobs have been spotted about 346 kilometers from Guadeloupe, between the islands of St. Vincent and Bequia, 1,000 yards (914 meters) off Martinique and off the coast of Key Largo, Florida.

Piles of algae collected on beaches cost millions of dollars to clean up, and removal efforts can also harm marine life, according to the Sargassum Information Hub.

In Barbados, locals used “1,600 dump trucks a day to clean the beaches of this seaweed to make it suitable for tourists and beach recreation,” Lapointe said.

In shallow water, sargassum can be removed using fishing nets towed by light boats or by hand, according to the Dutch Caribbean Nature Alliance.

In the United States, the cleanup is often done with Barber beach drifters pulled by a tractor, Lapointe said. But once there’s an accumulation of more than a foot of sargassum, the rakes don’t work as well, he added. This is when front loader dump trucks can be useful, but they can be harmful to beach health.

Using dump trucks to remove sargassum can be problematic.

“Often you have sea turtle nests on beaches that are run over by the tires of this heavy equipment that crush the eggs,” Lapointe said.

If sargassum is not cleaned from beaches or used as fertilizer, the arsenic in the flesh can leach into groundwater, which could be a human health hazard, Lapointe said.

An excessive amount of rotting sargassum can also support the growth of fecal bacteria.

And in 2018, a massive bloom that ended up on South Florida beaches coincided with the largest red tide ever seen on that coast, Lapointe said. Red tides occur when toxin-producing algal blooms grow so out of control that they discolour coastal waters. Red tide organisms can live on sargassum and be transported by it.

The toxins in red tides can harm marine life, and sargassum buildup on beaches can prevent sea turtle hatchlings and adults from getting to sea, Lapointe said.

Experts don’t know if a sargassum bloom of this size will happen every year, Lapointe said.

“It’s hard to project because we don’t know everything we need to know about the drivers (behind this),” he said. – We know that it varies from year to year, and that the trajectory generally goes up. So based on what we’ve seen in the past, we think we may continue to see this worsen in the coming years. What will it be like in 10 years? Will it be twice as big as it is now?”

More funding to do the research that can answer these questions is needed, he added.

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