Sargassum Seaweed Still Invading Atlantic Coasts
- Kate Pugnoli
- Aug 14
- 5 min read
Can These Beach-Fouling Algae Be Turned into Useful Products?
The Caribbean islands, Florida, and the Mexican Riviera are well known as popular vacation hotspots, but since 2011, these beautiful locations can sometimes become blanketed with Sargassum seaweed “rafts” that stretch for miles along coastlines.
As this seaweed rots, it releases a sulfurous stench—which sickens local residents and drives away tourists—and poses risks for adverse health effects and environmental impacts.
To clear the water and the air, various companies are working to harvest Sargassum and turn this unwanted vacation-wrecker into something useful.
Sargassum’s Environmental Concerns
Sargassum is a type of floating brown algae that can collect in large masses. Out in the ocean, these huge, floating rafts act as habitat, food, protection, and breeding grounds for various marine species.
Unfortunately for humans, since 2011, these huge rafts have also floated onto Atlantic coastlines and become trapped. When Sargassum decomposes, it releases hydrogen sulfide, a noxious gas.
At concentrations of 2 to 5 parts per million (ppm), hydrogen sulfide can cause nausea, tearing of the eyes, headaches, or loss of sleep. A 2020 study found that patients living near Sargassum-invaded waters may have been exposed to hydrogen sulfide concentrations of greater than 5 ppm for 50 days per year. This could explain why the patients’ most frequent reasons for seeking medical care were for neurological, digestive, and respiratory disorders.
At even higher concentrations—50 to 400 ppm—the fumes can lead to “difficulty in breathing, agitation, confusion, nausea and vomiting, elevated blood pressure, and loss of consciousness,” a 2023 study found. In addition, a 2024 study found that Sargassum hydrogen sulfide exposure is linked to increased central sleep apnea events.
When it decomposes, Sargassum releases hydrogen sulfide … [which] can cause nausea, tearing of the eyes, headaches, or loss of sleep.
Sargassum also can contain heavy metals and a pathogen (Vibrio bacteria) that can lead to skin infections or gastrointestinal illness. For example, arsenic concentrations in Sargassum that washed up in Mexico along the Gulf of America in 2018 ranged from 29.0 to 65.7 mg/kg, according to the Environmental Protection Agency. This is well above the 3 mg/kg recommendation set by the Algae Technology & Innovation Centre in France in their 2024 update.
Ever since the first Sargassum bloom in the Atlantic occurred in 2011—following prevailing wind, ocean currents, and nutrient conditions in 2009 to 2010—huge patches of it have been found from the coast of Africa to the Americas.
When overaccumulations occur—known as Sargassum inundation events—this can adversely impact coastal ecosystems, local tourism, and public health.
Challenges in Handling Sargassum
Sargassum can be left on beaches, the Cayman Islands’ Department of Environment (DOE) notes. The algae, which can occur in small amounts too, “will eventually get washed away or buried in the next storm, with rain easing the smell,” the agency says. “Leaving Sargassum on the beach has proven to be the simplest and lowest cost approach, also helping to nourish the beach and stabilize the shoreline.”
But if the Sargassum has got to go, it should be collected and removed when it is fresh, free-floating, and before it piles up and starts to rapidly deteriorate, environmental experts say.
Removal is not an easy task, though.
The US Environmental Protection Agency, for example, recommends manual or mechanical removal that minimizes sand displacement and doesn’t use chemicals. The Cayman Islands’ DOE adds that extreme care should be taken to prevent destruction of beach vegetation, turtle nests, and bird nesting habitat. Beaches should be “naturally clean” but not “over-sanitized,” it says.
The Cayman Islands’ Department of Environment adds that [when removing sargassum,] extreme care should be taken to prevent destruction of beach vegetation, turtle nests, and bird nesting habitat.
Unfortunately, using heavy machinery to remove Sargassum mats can negatively impact beach habitats by compacting sand and killing organisms that live there, such as ghost crabs that keep a beach healthy by aerating the sand. Heavy machinery can also crush potential sea turtle nests.
Converting Sargassum into Useful Products
A 2020 report by the University of the West Indies, funded by the UN’s Food and Agriculture Organization, reviews potential uses and associated challenges of converting Sargassum into commercial products. These include agriculture (such as for animal feed and compost), bioenergy (for bioethanol and biogas), bioplastics, clothing and footwear, construction (bricks), cosmetics, and paper products.
[Sargassum has potential] uses in agriculture …, bioenergy …, bioplastics, clothing and footwear, construction (bricks), cosmetics, and paper products.
For instance, Omar Vázquez Sánchez, who started off with a sargassum cleanup business in 2015 upon his return to Mexico, eventually had a vision that inspired him to construct the “Sargablock”—brick made from 40% sargassum and 60% other organic materials. Equipped with a machine that could make 1,000 Sargablocks per day, Sánchez’s work was part of the UNDP’s Support for Strategic Initiatives to build homes with Sargablocks for those in need.
“The first thing I did was to put myself in other people’s shoes since I was in a similar situation,” Sánchez said. “The irony of life is growing up without a house of your own and now having the opportunity to donate them to people.”
Florida-based company Algas Organics has developed what they call a non-wood kraft pulp from banana stems, pineapple leaves, and seaweed for application as pulp, textile fiber, and packaging material.
<<Readout: “We developed a patented fermentation process to remove heavy metals from the [Sargassum] seaweed, which is a significant barrier for many potential uses.”>>
According to company founder Johanan Dujon in an interview last year, “We developed a patented fermentation process to remove heavy metals from the [Sargassum] seaweed, which is a significant barrier for many potential uses.” If the pilot trial proves successful, this process could be adopted by Miami-Dade County. “The most exciting application is in the paper and pulp industry. If our material can help reduce deforestation, that would have a significant impact,” he said.
In Mexico, researchers at Tec de Monterrey are developing methods to transform the overabundant mats of Sargassum into an oil that can be used as an additive in synthetic lubricants commonly used in car engines and industrial machinery. The researchers tested a formula that had 10% Sargassum oil and 90% conventional lubricant, which resulted in a 26% higher viscosity index and “improved metal part protection in engines by up to 10%” compared to pure PAO6, a common lubricant.
However, not all projects are bearing fruit. In 2019, a company called Renovare developed an eco-friendly shoe using five PET bottles for the shoe’s upper part and 100 grams of Sargassum for the shoe’s sole, according to Mexico News Daily. They had sales of about 20,000 pairs per month. While a patent was filed in 2020 and assigned to Renovare USA LLC in 2024, the company’s website and social media are no longer active as of late 2024.
Prospects of Sargassum
While new research and innovations with Sargassum are ongoing, there is hope that it can be used to make alternatives to fossil fuel–based products.
Whether it be through Carbonwave’s efforts to make Sargassum-based fertilizers and cosmetic emulsifiers; Seafields’ efforts to grow and produce Sargassum to make bioplastics, fertilizers, and emulsifiers; or Seaweed Green’s Sargassum-based soil enhancer, there appears to be great potential for converting a beach-fouling nuisance into sustainable products.
*Kate Pugnoli is an Arizona-based freelance journalist and former educator who works with nonprofit organizations. Her area of interest is in addressing environmental issues impacting marine biodiversity and conservation.
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