Picture football field-sized islands of algae stretched across the open ocean, extending across the entire Atlantic from Western Africa all the way to the Gulf of Mexico. This is the Great Atlantic Sargassum Belt, 5,000 miles of seaweed canopy that provides essential habitat for a host of marine life, from the green sea turtle to the blue marlin, as well as the sargassum fish, a camouflage-colored frogfish with leafy spines lining its body — so named because they are uniquely adapted to live and feed within the snarls of sargassum beds. By providing shelter, food, migratory pathways, and resting areas for at least 80 marine species, sargassum seaweed ecosystems are essential for the ocean’s biodiversity. World-renowned oceanographer Sylvia Earle characterized sargassum islands as the “golden floating rainforests” of the Atlantic.
Several natural processes promote sargassum growth — foremost among them the upwelling of nutrients from deep ocean waters and the influx of fertilizers like iron, nitrogen, and phosphorus from agricultural runoff. Small quantities of sargassum have always washed up on coastlines, stabilizing the shorelines by buttressing the build-up of sand dunes and nourishing the flora that live within them. But since 2011, as sea temperatures rise and new circulation patterns accelerate sargassum growth, the seaweed has bloomed in increasingly large quantities, brought to nearby shores to decompose en masse by changing winds and ocean currents. It’s along the coast where the once golden rainforest turns into a force of destruction — no longer floating in the open ocean, sargassum accumulates, suffocating shores, trapping marine life inside its tangles, smothering seagrass meadows and coral reefs, and ultimately coming between people and their connection with the ocean.
Reaching the shores of the Dominican Republic
Enter the Dominican Republic, the second largest country in the Caribbean. In 2022 alone, its beachfronts brought in a record 8.5 million island visitors. The country’s fishing industry provides not just local sustenance, but also fuels local economies, bringing in around $93.4 million annually. In some communities, local reports estimate that up to 60% of people directly depend on fishing for a living.
But as those millions of visitors set foot on the white sand beaches in the summer of 2022, sargassum accumulation in the Atlantic reached a staggering mass of over 24 million tonnes — blooming larger and spanning farther along the shore than ever before. This inrush of seaweed engulfed the islands’ coastal waters and piled up in red blankets across miles of sand. Satellite images taken in March revealed even more massive mats of algae looming in the Caribbean, some of them over half a mile wide, heading towards the coasts of Caribbean islands in unprecedented proportions and arriving earlier in the season than ever before.
Sargassum invasion in these quantities raises alarms for both the economies and ecosystems of the Dominican Republic. Forming a dense layer on the sea surface, sargassum prevents sunlight from penetrating the water column. As a consequence, corals and seagrasses become shrouded in shadow and suffocate. These vital coral and seagrass ecosystems are essential habitats for local populations of reef and demersal fish, those residing closest to the sea floor. Once the sargassum dies, it sinks, further stifling marine plants and coral reefs, and its decomposition causing “dead zones” — areas with low oxygen levels unsustainable for life. “The coast begins to change dramatically upon the arrival of sargassum to the shore, as it decomposes in such a way that it depletes the water of oxygen and kills the fish offspring that reproduce near the shore,” says Carlos Perdomo, president of a fisherman association in Punta Cana. The devastation doesn’t stop there: Sargassum decomposition acidifies the water, bleaching corals and depleting fish stocks. Because sargassum accumulates in this shallow water, its overgrowth traps dolphins and turtles in deadly natural nets, ensnaring coastal marine life indiscriminately.
Effects on small-scale fishing and tourism
Sargassum accumulation creates severe complications for the local fishing community. The thick mats of seaweed entangle fishing gear, hindering the ability of fishermen to cast their nets or even operate their fishing boats at all. Local fishermen like Elías Rodrïguez, president of the Association of Fishermen in Cabeza De Toro, testify to the technological issues spurred by sargassum. “Our equipment breaks constantly, especially [as] the boat motors get clogged and our propellers sink. In just one week, sargassum has [cost] me four propellers.” When sargassum accumulates, it can extend five meters into the water, not only reducing the catch but also leading to additional maintenance costs and time lost as fishermen struggle to navigate through the dense vegetation.
This effect is compounded by the constant friction against the rough seaweed surface that wears out fishing lines and nets, leading to frequent equipment replacements. For small-scale fishermen, who operate with limited financial resources, these additional expenses can become a considerable burden. Eventually, fishermen may be forced to alter their fishing grounds or temporarily suspend fishing operations until the seaweed dissipates, which can lead to significant economic loss and food insecurity for them, their families, and their communities. “Fishermen suffer a lot [...] ‘the fisherman is hungry,’ as we say,” shares Elías. “Right now, red snapper fishermen have not gone out in a month, and they can’t subsist. It’s very hard.”
The Dominican Republic’s tourism industry has felt devastating effects. Once pristine, sandy beaches transform into unsightly mounds of rotting vegetation; once crystal-clear waters take on a murky, orange hue. As sargassum piles up on the beaches and dries, it produces the notoriously pungent hydrogen sulfide gas. Simply put, it stinks! The combined sight and smell of the decaying seaweed not only reduce the aesthetic appeal of the beaches, but also render them unavailable for visitors to engage in water-based activities. Within 48 hours, the decaying sargassum produces significant amounts of other toxic gases like ammonia, endangering anyone nearby and putting people at risk of respiratory and neurological damage. Sargassum overblooms are a public health crisis.
The decaying seaweed degrades water quality and harms marine organisms. As a result, popular snorkeling and diving spots in Punta Cana — one of the country’s most visited destinations — have seen a decline in marine biodiversity, threatening underwater tourist experiences like dive tours. These environmental concerns have also led to much-needed conservation efforts that restrict entry to certain areas, limiting tourist access to beaches and reducing the overall accessibility of the island.
In combination, all of these factors could reduce Dominican tourism, motivating visitors to cancel reservations and causing severe ramifications for its economy. Tourism is a crucial pillar of the Dominican Republic, contributing significantly to its GDP, foreign exchange earnings, and employment opportunities. In 2019, tourism revenues accounted for approximately 20% of the Dominican Republic's total export earnings. The industry supported around 800,000 jobs, representing around 16.6% of total employment. Tourism has also played a vital role in regional development, attracting investment and infrastructure development in coastal areas.
Due to the overpopulation of sargassum seaweed globally, the United Nations estimated that some countries, like Mexico, experienced a 35% drop in tourism in 2018. Reports from local businesses in Guayacanes — another popular tourist destination in the Dominican Republic — estimate losses of up to 60% of visitors in 2023. The decline in tourism decreases the demand for locally caught fish, exacerbating the financial strain on small-scale fisherfolk and their families.
Fishing for solutions
Sargassum overblooms have threatened fishing and tourism industries, with cascading effects on local communities. But these communities are resilient, and many are coming together to explore technological solutions to the crisis. Andrés Bisonó León, executive president of Sargassum Ocean Sequestration of Carbon (SOS Carbon), believes that the excessive influx of sargassum can be an opportunity to create new jobs and markets for the use of sargassum as raw material. The company’s namesake product is the SOS system — a boat-mounted device that pumps the surface seaweed to 200 meters below the surface, a depth beyond which the ocean pressure is expected to continue sinking it to a depth of 1 km or more. As Andrés describes, the benefits are twofold: first, this method precludes the high-cost current necessity of bringing the sargassum inland to manage, and second, it allows Dominicans to sequester carbon deep in the ocean. “We can use the oceans as a carbon storage and carbon removal place.”
Patent pending, this innovation could partly counter the environmental impact of sargassum overgrowth. But financing remains an issue. As Andrés notes, “We're still working on launching this technology at an operational level — that's an area where funding would be very handy because we can propel [...] or advance the scientific knowledge around it, to really just launch it or implement it at that operational scale.”
SOS aims to prioritize sustainable, community-centered practices in their approach. Andrés emphasizes that whether they are designing or deploying systems and technologies, their goal is to maximize efficiency and uptake, and minimize the use of new equipment, incorporating local materials that communities already have on hand. “We try to do the opposite of just saying hey, you cannot go fish. We instead offer them a platform of employment and help in this transition.”
Using artisanal vessels to harvest sargassum with retrofitted hardware, SOS turns local boats into high-capacity harvesters. In doing so, they not only take advantage of existing infrastructure, but also incorporate the local expertise of already established industries and communities into their designs and planning.
Beyond the Dominican Republic, a bevy of other solutions to the sargassum crisis are under development with potential for widespread application. In Puerto Morelos, Mexico, Omar Vázquez Sánchez stirs sargassum into bricks to build houses for those in need. Traditional building materials like concrete and clay bricks pose a significant environmental footprint due to their high-pollution production processes — sargassum, renewable and biodegradable, may well prove a more sustainable construction material. With its natural insulating properties, sargassum-brick buildings could be more energy-efficient and cost-effective than those built with conventional materials, able to be quickly scaled in regions like the Dominican Republic where the seaweed is abundant.
In Jamaica, entrepreneur Daveian Morrison is constructing a processing facility to convert seaweed into charcoal as a substitute for firewood. His recipe for animal feed made from the protein-rich algae proved a hit at a local goat farm, but needs more testing to further evaluate its scalability.
And in Barbados, a team from the University of the West Indies integrates sargassum with waste from a rum distillery to produce methane to power transportation across the island. Subject to additional research and funding, this biofuel holds the promising potential to replace fossil fuels that currently power the majority of Caribbean vehicles.
Confronting the climate crisis and the need for the Loss & Damage Fund
The sargassum crisis is but one of the myriad consequences of climate change currently devastating the Dominican Republic and other Caribbean nations. Small island communities like the Dominican Republic pay the steepest price for the climate crisis, despite developed nations bearing the responsibility for the vast majority of greenhouse gas emissions that fuel climate change. Every year, rising sea levels and temperatures, intensifying extreme weather events, and the degradation of marine ecosystems increase the burden on small island states and their communities.
The profound impacts of the sargassum crisis in the Dominican Republic cast a glaring spotlight on the necessity for the Loss & Damage Fund — a new financial mechanism through which developed countries can support small islands and developing countries in their fight against climate change. Designed to aid those on the front lines, the Loss & Damage Fund will allow vulnerable countries to recover from climate-induced losses and adapt to new realities.
The Loss & Damage Fund is primed to be the necessary lifeline for small island nations in response to our global crisis. Its impact will extend far beyond the mitigation of sargassum, a testament to international cooperation and coordination in the service of all who seek a just and sustainable future in the face of a changing world.
