Here's the Real Story behind the Massive 'Blob' of Seaweed Heading toward Florida (2024)

March 17, 2023

3 min read

Here’s the Real Story behind the Massive ‘Blob’ of Seaweed Heading toward Florida

Florida beaches are already receiving hefty batches of brown seaweed, kicking off a year that could break records

By Meghan Bartels

Here's the Real Story behind the Massive 'Blob' of Seaweed Heading toward Florida (1)

A loose raft of brown seaweed spanning about twice the width of the U.S. is inching across the Caribbean. Currently, bucketloads of the buoyant algae are washing up on beaches on the eastern coast of Florida earlier in the year than usual, raising scientists’ concerns for what coming months will bring.

The seaweed is made up of algal species in the genus Sargassum. These species grow as a mat of glops of algae that stay afloat via little air-filled sacs attached to leafy structures. The algae form a belt between the Caribbean and West Africa in the Sargasso Sea in the North Atlantic Ocean and then ride the currents west. Scientists say that reports of a massive blob of seaweed slamming into coastlines are overblown because the Sargassum algae are scattered across the ocean, and much of the seaweed will never reach the coast’s sandy shores. But in recent years researchers have generally seen larger so-called Sargassum blooms. And once the seaweed begins washing up on beaches and rotting, it can cause serious problems, local communities say.

Among annual Sargassum censuses in the Atlantic Ocean, “2018 was the record year, and we’ve had several big years since,” says Brian Lapointe, an oceanographer at Florida Atlantic University, who has studied seaweed for decades. “This is the new normal, and we’re going to have to adapt to it.”

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The seaweed “blob” has been dubbed the Great Atlantic Sargassum Belt, and though it’s sprawling, the algae in the belt cover only about 0.1 percent of the water’s surface, says Chuanmin Hu, an oceanographer at the University of South Florida, who has used satellites to study Sargassum for nearly 20 years.

Hu and his colleagues estimate the total mass ofSargassumin the Atlantic every month, tracking a yearly cycle that typically peaks in June. To do so, they use data collected by NASA satellites such as Terra and Aqua, as well as National Oceanic and Atmospheric Administration satellites. Last year the seaweed broke the record for the highest amount ever recorded in the Atlantic, with some 22 million metric tons of the stuff found across the ocean, according to the team’s calculations.

Hu says the team estimated that the Atlantic contained about six million metric tons of Sargassum in February and that he’s confident March’s mass will be higher. “This month there should be more. There’s no doubt,” Hu says. “Even in the first two weeks, I have seen increased amounts.”

In the ocean, Hu says, the Sargassum is crucial habitat for fish and turtles, among other marine life. He calls the belt a “moving ecosystem.” And just a small portion of the seaweed present in the Atlantic will ever wash up on beaches, Hu adds.

But beaches in Fort Lauderdale and the Florida Keys are already reporting Sargassum deposits this year, Lapointe says, and it’s on beaches that the seaweed can be problematic. There, he says, the algae rot and release chemicals such as hydrogen sulfide gas, which smells like rotten eggs. When inhaled, the gas can also cause headaches and irritate a person’s eyes, nose and throat. People with asthma or other breathing problems may be more sensitive to the effect, according to the Florida Department of Health. The seaweed’s early arrival is raising concerns about what this summer might bring.

“This is pretty early in the Sargassum season to see that much coming in, so I think that’s also fueling some of the concern about what’s to come,” Lapointe says.

Hu says that Sargassum amounts can’t be forecast more than two or three months out, so this year’s seasonal peak in the summer is still too distant to predict. Researchers have expected this year might turn out to be heavy in seaweed, however, because even the winter lull saw higher amounts of the stuff than average.

And the Atlantic has been reliably producing much more Sargassum in recent decades than it has historically. Lapointe says that the high Sargassum levels of recent years are likely in part tied to nutrient-rich water running off land into rivers and out to the oceans, where it can fertilize the seaweed. But understanding and addressing the problem remains knotty, he adds.

“This has been going for over 10 years now, and we haven’t made a whole lot of progress in better understanding of all these nutrient and climate drivers,” he says. “It’s something we’re working on as scientists.”

Here's the Real Story behind the Massive 'Blob' of Seaweed Heading toward Florida (2024)


Here's the Real Story behind the Massive 'Blob' of Seaweed Heading toward Florida? ›

Scientists say that reports of a massive blob of seaweed slamming into coastlines are overblown because the Sargassum

The Sargasso Sea (/sɑːrˈɡæsoʊ/) is a region of the Atlantic Ocean bounded by four currents forming an ocean gyre. Unlike all other regions called seas, it has no land boundaries. It is distinguished from other parts of the Atlantic Ocean by its characteristic brown Sargassum seaweed and often calm blue water. › wiki › Sargasso_Sea
algae are scattered across the ocean, and much of the seaweed will never reach the coast's sandy shores. But in recent years researchers have generally seen larger so-called Sargassum blooms.

What is causing the seaweed blob in Florida? ›

Piles of sargassum seaweed are accumulating on the beaches of Florida's Key West. Scientists say the seaweed is expected to increase even more over the next few months. CNN. A record-breaking blob of smelly seaweed is arriving in Key West -- and tourists aren't happy about it.

Where is a giant blob of seaweed expected to hit? ›

It's called sargassum, and scientists say the blob is growing and already making its way to Florida.

What is causing all the seaweed? ›

One possible contributor is nutrient pollution from land that washes into the ocean from cities, farms, roadways and other human sources. This effectively floods the ocean with a food source that leads to rapid growth in Sargassum. Another possible source is one we know all too well, climate change.

Where is all the sargassum coming from? ›

The Great Atlantic Sargassum Belt

Historically, the majority of Sargassum was located in the Sargasso Sea in the western North Atlantic. In 2011, the geographic range of Sargassum expanded. A newly established population, driven by shifting wind patterns, is now thriving in the open ocean.

Which Florida beaches will be affected by sargassum? ›

Florida's southeast coast gets the brunt of summer's sargassum blobs, whereas beaches on Florida's west coast only get a little bit of seaweed, if any.

What is causing the bloom of sargassum? ›

Much of that was converted for agricultural uses, which means more fertilizer and other nutrients. "The Amazon River, which is the largest river in the world, is now bringing all these nutrients, phosphates and nitrates to the coast, which feeds the sargassum which is right offshore. And it blooms.

What is the smell in the Florida Keys? ›

As sargassum washes ashore every year in Key West, locals and visitors alike are primarily annoyed by the smell of the sargassum quantity on the beach.

Can you eat sargassum? ›

Did you know? Sargassum is edible, it's harvested to feed livestock too, and you can fry, boil, steam or dry it. It's played a part in Chinese medicine as far back as the 8th century, treating goiters (high iodine content) — and made into tea to control phlegm.

Do the Florida Keys get sargassum? ›

"If large amounts of sargassum do come to Florida at that time — late May or early June — the most impacted areas will be the lower Florida Keys (ocean side) and along the southeast coast of Florida (Miami Beach, Fort Lauderdale, Palm Beach, etc)," Hu said.

What happens to your body when you eat seaweed everyday? ›

Seaweed contains a range of minerals that are easy for the body to break down, so it may be good for someone to include in their diet. Eating seaweed may help with thyroid function, heart health, weight loss, and more. Types of seaweed include: nori.

Is Sargassum harmful to humans? ›

For example, Sargassum may harbor organisms, like jellyfish, that can cause skin irritation. Exposure to hydrogen sulfide and ammonia, produced during the decay of Sargassum, may also cause mild to serious health effects, including respiratory, cardiovascular, and neurological impacts.

Can Sargassum seaweed be used for anything? ›

Sargassum seaweed can be used in a variety of ways, such as in fertilizer, animal feed, or as a renewable energy source.

Can you swim in sargassum? ›

You can swim in the water if there's sargassum and people do, but I have seen some reports of sea lice associated with sargassum in water with big mats of it floating around,” he says, referring to small jellyfish larvae, which can cause the skin to erupt in a red, itchy rash.

Is sargassum coming from Africa? ›

The source of the Sargassum inundating beaches in Western Africa, the Caribbean, and the Eastern US is not suspected to be Sargassum drifting from the Sargasso Sea, but Sargassum germinating in the north equatorial recirculation region (NERR) south of the Sargasso Sea between the north equatorial current and the ...

Why is there so much seaweed in Florida? ›

BAYLES: For centuries, the huge mats of algae have swirled around the Sargasso Sea in the middle of the tropical Atlantic. In recent years, masses of sargassum broke loose in the spring and floated toward the beaches of Florida and the Caribbean.

Where is the Great Atlantic Sargassum Belt now? ›

As of 2023, the belt is estimated to weigh about 5.5 million metric tonnes and extends 5,000 miles (8,000 km), stretching from West Africa to the Gulf of Mexico. “I try to shy away from the term blob.

What is causing all the seaweed in Cancun? ›

There are a number of different theories for the rise in the seaweed in Mexico over the last few years. These include changing climate and wind patterns; nutrient-rich waters; and less hurricane activity, meaning the shredding of the seaweed by storms is reduced. However, there's no cause for concern.

What is the problem with sargassum? ›

It can not only block access to beaches and ports, but it can also negatively impact water quality. These problems often arise when sargassum isn't cleaned up in a timely manner. Because the seaweed begins to decompose within 24 hours, it must be processed or preserved relatively quickly.

Will there be sargassum seaweed in Florida in 2024? ›

Sargassum forecast 2024

Sargassum is expected to increase in the central Atlantic over the next few months. Coastal regions in the western Caribbean Sea will begin to see small to moderate amounts of sargassum around late April to early May. The southeast coast of Florida won't see much sargassum until late May.

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