A 5,000-kilometer-wide patch of seaweed is headed for Florida and threatens tourism

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A gigantic mass of seaweed that has formed in the Atlantic Ocean is headed for the coast of Florida and other coasts throughout the Gulf of Mexico, threatening to dump foul-smelling and potentially dangerous piles across the beaches and put a major damper on the tourist season .

The seaweed, a variety called sargassum, has long formed large blooms in the Atlantic Ocean, and scientists have been tracking massive accumulations since 2011. But this year’s sargassum mass may be the largest ever — stretching more than 5,000 miles from the coast of Africa to the Mexican Golf.

The blob is currently pushing west and will pass through the Caribbean and up into the Gulf of Mexico during the summer, when the seaweed is expected to be widespread on Florida beaches around July, according to Dr. Brian Lapointe, a researcher at Florida Atlantic University’s Harbor Branch Oceanographic Institute.

Lapointe said this year’s sargassum bloom started forming early and doubled in size between December and January. The mass “was bigger in January than it’s ever been since this new region of sargassum growth began in 2011,” Lapointe told CNN’s Rosemary Church.

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

He noted that in Barbados, locals used “1,600 dump trucks a day to clear the beaches of this seaweed to make it suitable for tourists and beach recreation.”

Sargassum is a collective 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.

The algae have their advantages when they drift in the sea.

“This floating habitat provides food and protection for fish, mammals, seabirds, crabs and more,” according to the Sargassum Information Hub website, which is 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 amberjack.”

The problems arise when sargassum hits beaches, not only piling up in mounds that can be physically difficult to navigate, but also emitting a gas that can smell like rotten eggs. And it can quickly turn from an asset to a threat to marine life.

“It comes in 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 human health, Lapointe noted. The gas released by the rotting algae, hydrogen sulphide, is toxic and can cause respiratory problems.

“You have to be very careful when cleaning the beaches,” he warned.

The seaweed itself also contains arsenic in the flesh, which makes it dangerous if eaten or used for fertilizer.

“If you’re in a place where you’re harvesting this to use as fertilizer … you have to be very concerned, especially if you’re using it for a food and fiber crop for human consumption,” Lapointe told CNN on Thursday.

Piles of algae dumped on beaches also cost millions of dollars to clean up, notes the Sargassum Information Hub.

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

Also, ocean currents can change the annual growth of sargassum and how much accumulates, Goni added. Phosphorus and nitrogen in the sea can also serve as food for the algae.

After taking samples of the area where the Sargas was formed and comparing it to old samples from the 1980s, Lapointe found that the nitrogen content had increased by 45%. Scientists believe that elevation is a likely cause of the bloom’s massive growth.

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

For now, researchers are investigating ways to counteract its impact on beaches, possibly by sinking the seaweed to the bottom of the ocean or harvesting it for use in commercial products such as soap, Goni said.

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

“Whatever we think we know today, it could change tomorrow,” he said.

Taylor Nicioli contributed to this story.

A 5,000-kilometer-wide patch of seaweed is headed for Florida and threatens tourism

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