Sargassum seaweed has been invading the coasts of the Caribbean and putting the health and economy of the region at risk. But innovative solutions try to make the best of the waste.
Across the Sargasso Sea in the Atlantic lie the shores of the Caribbean, “a beautiful place — wild, untouched, above all untouched,” as described by Jean Rhys in her 1966 novel Wide Sargasso Sea.
But by the summer of 2011, this pristine coast started turning orange, then brown, then black, becoming littered with heavy metals and toxic gasses as the sargassum seaweed took over and turned the turquoise oceans into dead zones.
This invasive algae has not only been killing the corals, mangroves, and fish along the coasts but is also driving away the region’s tourists, as the unbearable stench of the rotting seaweed threatens to ruin the fantasy of an idyllic vacation.
But the public health effects of this decomposing seaweed are worse: according to a 2023 study, sargassum releases hydrogen sulfide gas and ammonia, which affects the respiratory system and skin, causing neurocognitive symptoms within 48 hours of the seaweed washing ashore.
“Together we are weak, separated we are even weaker.”
Over the past 15 years, the coastal communities of the Caribbean have undertaken the arduous task of learning what they can about sargassum and converting the waste into biostimulants, gas, plastics, and bricks to build homes with. But as the sargassum invasion becomes worse due to a changing climate, locals struggle to keep up with it.
According to Dominican sociologist Max Puig, the sargassum invasion is a case of climate injustice. In his role as the executive vice president of the Dominican Republic’s National Council for Climate Change and Clean Development Mechanism, he has been involved in conversations happening during the Regional Sargassum Conferences — the first one in the Dominican Republic, and most recently in Grenada.
“Together we are weak, separated we are even weaker,” he said.
The sargassum crisis in the Caribbean began around 2010 when the algae migrated from the Sargasso Sea — the only sea in the world surrounded completely by oceanic gyres rather than a landmass or more — to the equatorial Atlantic, where a combination of warmer waters and nutrients from the Amazon and Sahara facilitated its proliferation until it formed the “Great Atlantic Sargassum Belt.”
This crisis was precipitated by an extreme climate event during the winter of 2009, when an extreme shift in the North Atlantic Oscillation caused westerly winds to blow across the Sargasso Sea for a longer period of time, bringing the sargassum to the larger system of ocean currents that move along the coasts of Africa, South America and all the way into the Gulf of Mexico.
On the high seas, sargassum plays a positive role in marine biodiversity, but when it reaches the coasts in large numbers, its color changes from orange to brown as it decomposes. As it covers significant parts of the coastline, it blocks the exchange of light and oxygen between the surface and the waters, creating a dead zone where neither fish nor corals survive, driving away tourists from the most tourism-dependent economies in the world.
The island of Barbados, located at the eastern end of the Antilles archipelago, is the most vulnerable to sargassum flooding, being the first landmass to get hit by the onslaught of algae every summer.
“The entire island is threatened by climate change, and sargassum is another unwanted addition to this list of problems, as hurricanes and this algae have become simultaneous dangers,” said Barbadian Karima Degia, programme manager for the Prevention, Recovery & Resilience program at the United Nations Development Program office for Barbados and the Eastern Caribbean.
According to the University of South Florida's Optical Oceanography Laboratory, by June 2024, the total amount of sargassum in the Caribbean increased to almost 10 million metric tons.
“Today, it takes 70 days for sargassum to reach the beaches from the [sargassum belt] southeast of Hispaniola, with flooding exceeding 68 million tons per year,” said Jimmy García, president of the National Authority for Maritime Affairs, which is the Dominican government agency in charge of all marine-related research.
According to García, sargassum can sometimes get caught in the turbines of thermoelectric plants, leaving the coal plants idle and costing around $700,000 per day. Satellite monitoring services have been alerting hotels, thermoelectric plants, and municipalities about any potential sargassum flooding.
But if the sky is cloudy, satellites can be delayed in the detection of sargassum for up to 24 hours.
According to Ulises Jáuregui, a chemical engineer and researcher at Santo Domingo’s National Institute of Technology, not dealing with sargassum at the regional scale is an example of “environmental injustice” in the Caribbean.
“It is a problem generated in another part of the planet but which we suffer from. It is time to mobilize to obtain funds that will allow us to launch a sustainable development industry around sargassum,” he said.
Between January and September 2022, approximately 29,000 tons of this algae were collected from the Quintana Roo shoreline in Mexico, and so, some companies are beginning to see sargassum as the 'new gold' of the Caribbean. If collected before it rots, it could be used to issue green bonds as a method for carbon sequestration. However, the smaller budgets of Caribbean countries make it difficult to transform waste into valuable goods.
“This is due to insufficient financial support for research and uncertainty on the part of certain businessmen, given that the quantities, dates, and places of arrival of this algae are difficult to estimate,” Jáuregui said.
“A country like the Dominican Republic cannot dedicate resources to subsidizing products resulting from sargassum, and that is the dilemma: we have the problem that it affects tourism, the environment and generates economic problems,” García said.
That has made sargassum “a fundamental issue in all environmental forums,” García said, with a cabinet in the Dominican Republic dedicated exclusively to sargassum research. “Currently, universities in our country are looking for solutions to this problem, developing applications that can use sargassum as raw material.”
Jáuregui’s laboratory is experimenting with possible applications of this algae: as biostimulant fertilizers for agriculture; as activated carbon to treat the acidic waters generated during mine closures; for advanced oxidation technologies for water purification; and alginate for the manufacture of degradable bioplastics.
Meanwhile, projects like Dominican start-up SOS Carbon are attempting to clean up the shores of the Caribbean by organizing events for the collection of the sargassum.
“By collecting for seven hours – in a strip of approximately 10 kilometers long by 500 meters wide — a single barge can collect up to 70 tons of sargassum per day,” said Andrés Bisonó León, founder and CEO of SOS Carbon, which has a collection device that can collect sargassum in open waters and can fit on most of the small fishing boats in the Caribbean.
The company’s objective is to prevent more than 70% of sargassum algae from reaching land and to use more than 90% of the harvested algae.
“It is a problem generated in another part of the planet but which we suffer from. It is time to mobilize to obtain funds that will allow us to launch a sustainable development industry around sargassum.”
A secondary goal is to position the Caribbean as a “BlueTech” center, making it the advanced technology sector of the maritime industry: the company’s “Marine Symbiotic” biostimulant has already been applied to more than 12 crops in the fields.
SOS Carbon has also pioneered the global supply chain for fresh sargassum in both dried and treated form, having shipped samples and container loads of seaweed to over 10 countries — in Finland, it is used as a chemical feedstock for the textile industry by the company Origin by Ocean.
Mari Granström, CEO and Founder of Origin by Ocean said that the main takeaway from the recent regional conference on sargassum in Grenada was the transformation of discussions regarding sargassum: the conversations had started to move away from the identification of the program to taking action.
“There is a lot of money out there, and now we just must mobilize it towards the supply chain,” Granström said.
In southeastern Mexico, tourism is the driving force for the Riviera Maya economy, comprising more than 20% of the gross domestic product of the region in 2019, and with almost 140,000 hotel beds by the end of 2024. Yet, 4% of the sargassum that circulates between the Caribbean and the Atlantic reaches the state of Quintana Roo in Mexico, the state only has sargassum containment barriers along less than 3% of its coastline, and thus suffers the consequences of sargassum flooding.
According to the Inter-American Development Bank, the impact on Quintana Roo’s gross tourism product due to sargassum from 2016 to 2019 was 11.6%. The bank just released a report highlighting community perspectives regarding sargassum in the Caribbean, as well as innovations by entrepreneurs in the region.
In the port town of Puerto Morelos in Quintana Roo, Omar Vázquez is trying to make composite bricks with 40% sargassum through his Sargablock initiative.
Vázquez says he would like to have more state support to be able to add machines to his workshop. He wants to increase his production of sargassum bricks to 10,000 a day which could then be used to remodel homes vulnerable to hurricanes in the Riviera Maya area.
But for regions that are directly impacted by the increasing quantities of sargassum, “collecting the millions of tons of sargassum floating in the Caribbean would be very expensive,” said Rosa Rodríguez, marine biologist and researcher at the Institute of Marine Sciences and Limnology of the National Autonomous University of Mexico.
Instead of burdening the communities with the additional responsibility of collecting sargassum, Rodríguez suggests a “mitigation scheme that facilitates the import of containment barriers and “management strategies for rapid collection with a regulatory framework where sargassum is handled as special waste since it contains heavy metals, hydrocarbons, and pesticides.”
This story was produced in partnership with the Pulitzer Center.
