While harmful algal blooms of red tide and blue-green algae receive a lot of press in South Florida, there’s another threat that’s emerged in recent years and choking the Caribbean — Sargassum seaweed.
Brian Lapointe, Ph.D., a research professor with FAU’s Harbor Branch Oceanographic Institute, has studied Sargassum seaweed since the 1980s. He’s long suspected that water quality issues, due to runoff and sewage, are the cause for the increasing Sargassum blooms. Now, in a recently published study, he’s confirmed that theory. Compared to the 1980s, Sargassum today has 35% more of the nutrient nitrogen in its tissues.
Sargassum seaweed is a type of floating brown algae. It drifts along the currents of the open ocean and accumulates in the Sargasso Sea, a region of the Atlantic Ocean bounded by four currents rather than land. Under normal circumstances, the seaweed provides shelter and food for an impressive array of marine life, like sea turtles, fish and crabs, as well as commercially important species like mahi-mahi, Lapointe said.
But more isn’t necessarily better, as is the case with Sargassum. With increasing nutrients from rivers including the Amazon and Orinoco in South America as well as the Mississippi, Sargassum becomes a problem. Since 2011, unprecedented strandings of the seaweed have occurred over vast areas of the North Atlantic basin and Caribbean. “It’s causing catastrophic problems in the Caribbean, because the massive amounts cause dead zones,” Lapointe said. “When it comes ashore, it’s just so much it strips the oxygen out of the water.”
The excessive Sargassum blooms are contributing to the decline of coral reefs, dangerous for wildlife by smothering sea turtle nesting sites or entangling dolphins surfacing to breathe, and even a threat to human health. When the rotting, foul-smelling seaweed clogs up canals and buries the beach, it releases hydrogen sulfide, which can irritate your eyes, nose and throat, according to the Florida Department of Health. It also contains heavy metals like arsenic and fecal bacteria. For that reason, the state monitors the water quality around beaches when Sargassum is present. You won’t catch Lapointe swimming at the beach during these times, he said.
For this study, Lapointe and his team collected a total of 488 samples of Sargassum between 1983 from 2019, from locations around the North Atlantic, including the Florida Keys, Gulf Stream, Sargasso Sea and reefs in Central and South America. The researchers analyzed the tissues and compared the baseline values in the 1980s to those in more recent decades. They found that nitrogen increased by 35%, while phosphorus decreased by 44%.
In Florida, and across the Caribbean, people are spending millions of dollars to mitigate this problem, which will likely get worse with global warming and the associated climate change, Lapointe said. With predictions including heavier rainfall and more severe storms, climate change has potential to release even more nutrients into the water, and further feeding the blooms.
The solution, Lapointe said, is to address our water quality issues locally, particularly due to septic tanks and sewage. “People talk about the fertilizer, but no one wants to talk about sewage. I’ve been fighting that for a long time in Florida,” he said. That’s slowly starting to change, however, despite being long overdue, Lapointe added. For instance, a recently approved senate bill, called the Clean Waterways Act, includes changes in wastewater treatment, reuse potable water and biosolids application.”
“The vitality of Florida’s environment, economy and way of life is dependent on the health of our waterbodies. That’s why the state prioritizes protecting and preserving Florida’s waterways by implementing sound, science-based solutions to current and future environmental challenges,” said Alexandra Kuchta, press secretary for the Florida Department of Environmental Protection (DEP). “The Clean Waterways Act is part of a multifaceted effort to improve and maintain the health of our waters for generations, and DEP looks forward to continuing working with partners to guarantee this success.”
Action to clean up our sewage to reduce nitrogen coming into the water is a start, Lapointe said. “If we want healthy oceans, we need to go on a nitrogen diet.” Emerging technologies are now available that can reduce nitrogen in sewage effluent by up to 98% and can be used anywhere without the need for a municipal collection system. Most importantly, they are as affordable as a conventional septic system, he said.
Lapointe is currently studying these systems with promising prognosis. “Our groundwater monitoring data for the On-Syte Performance system is showing a major reduction in nitrogen concentrations by this technology,” Lapointe said. “This could be a game changer for Florida and beyond.” ⬥
BY GISELE GALOUSTIAN | 5/24/2021
For centuries, pelagic Sargassum, floating brown seaweed, have grown in low nutrient waters of the North Atlantic Ocean, supported by natural nutrient sources like excretions from fishes and invertebrates, upwelling and nitrogen fixation. Using a unique historical baseline from the 1980s and comparing it to samples collected since 2010, researchers from Florida Atlantic University’s Harbor Branch Oceanographic Institute and collaborators have discovered dramatic changes in the chemistry and composition of Sargassum, transforming this vibrant living organism into a toxic “dead zone.”
Their findings, published in Nature Communications, suggest that increased nitrogen availability from natural and anthropogenic sources, including sewage, is supporting blooms of Sargassum and turning a critical nursery habitat into harmful algal blooms with catastrophic impacts on coastal ecosystems, economies, and human health. Globally, harmful algal blooms are related to increased nutrient pollution.
The study, led by FAU Harbor Branch, in collaboration with the University of South Florida, Woods Hole Oceanographic Institution, the University of Southern Mississippi, and Florida State University, was designed to better understand the effects of nitrogen and phosphorus supply on Sargassum. Researchers used a baseline tissue data set of carbon (C), nitrogen (N) and phosphorus (P) and molar C:N:P ratios from the 1980s and compared them with more recent samples collected since 2010.
Results show that the percentage of tissue N increased significantly (35 percent) concurrent with a decrease in the percentage of phosphorus (42 percent) in Sargassum tissue from the 1980s to the 2010s. Elemental composition varied significantly over the long-term study, as did the C:N:P ratios. Notably, the biggest change was the nitrogen:phosphorus ratio (N:P), which increased significantly (111 percent). Carbon:phosphorus ratios (C:P) also increased similarly (78 percent).
“Data from our study supports not only a primary role for phosphorus limitation of productivity, but also suggests that the role of phosphorus as a limiting nutrient is being strengthened by the relatively large increases in environmental nitrogen supply from terrestrial runoff, atmospheric inputs, and possibly other natural sources such as nitrogen fixation,” said Brian Lapointe, Ph.D., senior author, a leading expert on Sargassum and a research professor at FAU Harbor Branch.
A total of 488 tissue samples of Sargassum were collected during various research projects and cruises in the North Atlantic basin between 1983-1989 and more recently between 2010-2019, and included seasonal sampling offshore Looe Key reef in the lower Florida Keys (1983 and 1984) and a broader geographic sampling (1986 and 1987) offshore the Florida Keys, Gulf Stream (Miami, Charleston and Cape Fear), and Belize, Central America. Oceanic stations included the northern, central and southern Sargasso Sea.
The highest percentage of tissue N occurred in coastal waters influenced by nitrogen-rich terrestrial runoff, while lower C:N and C:P ratios occurred in winter and spring during peak river discharges. The overall range for N:P ratios was 4.7 to 99.2 with the highest mean value in western Florida Bay (89.4) followed by locations in the Gulf of Mexico and Caribbean. The lowest N:P ratios were observed in the eastern Caribbean at St. Thomas (20.9) and Barbados (13.0).
Because of anthropogenic emissions of oxides of nitrogen (NOx), the NOx deposition rate is about five-fold greater than that of pre-industrial times largely due to energy production and biomass burning. Production of synthetic fertilizer nitrogen has increased nine-fold, while that of phosphate has increased three-fold since the 1980s contributing to a global increase in N:P ratios. Notably, 85 percent of all synthetic nitrogen fertilizers have been created since 1985, which was shortly after the baseline Sargassum sampling began at Looe Key in 1983.
“Over its broad distribution, the newly-formed Great Atlantic Sargassum Belt can be supported by nitrogen and phosphorus inputs from a variety of sources including discharges from the Congo, Amazon and Mississippi rivers, upwelling off the coast of Africa, vertical mixing, equatorial upwelling, atmospheric deposition from Saharan dust, and biomass burning of vegetation in central and South Africa,” said Lapointe.
Long-term satellite data, numerical particle-tracking models, and field measurements indicate that the Great Atlantic Sargassum Belt has recurred annually since 2011 and extended up to 8,850 kilometers from the west coast of Africa to the Gulf of Mexico, peaking in July 2018.
“Considering the negative effects that the Great Atlantic Sargassum Belt is having on the coastal communities of Africa, the Caribbean, Gulf of Mexico and South Florida, more research is urgently needed to better inform societal decision-making regarding mitigation and adaptation of the various terrestrial, oceanic, and atmospheric drivers of the Sargassum blooms,” said Lapointe.
Sargassum removal from Texas beaches during earlier, less severe inundations was estimated at $2.9 million per year and Florida’s Miami-Dade County alone estimated recent removal expenses of $45 million per year. The Caribbean-wide clean-up in 2018 cost $120 million, which does not include decreased revenues from lost tourism. Sargassum strandings also impact marine life and cause respiratory issues from the decaying process and other human health concerns, such as increased fecal bacteria.
“Human activities have greatly altered global carbon, nitrogen, and phosphorus cycles, and nitrogen inputs are considered now ‘high risk’ and above a safe planetary boundary,” said Lapointe. “Based on scientific research, population growth and land-use changes have increased nitrogen pollution and degradation of estuaries and coastal waters since at least the 1950s. Despite decreases in nitrogen loading in some coastal watersheds, N:P ratios remain elevated in many rivers compared to historic values. The trend toward higher N:P ratios in the major rivers in the Atlantic basin parallel the increased N:P ratios we now see in Sargasum.”
Study co-authors are Rachel Brewton, a research coordinator, and Laura Herren, a research biologist, both at FAU Harbor Branch; Chuanmin Hu, Ph.D., a professor of optical oceanography, University of South Florida; Mengqui Wang, Ph.D., a post-doctoral researcher in the College of Marine Science, University of South Florida; Dennis McGillicuddy, Jr., Ph.D., senior scientist and department chair of applied ocean physics and engineering, Woods Hole Oceanographic Institution; Scott Lindell, a research specialist, Woods Hole Oceanographic Institution; Frank J. Hernandez, Ph.D., an assistant professor, Division of Coastal Sciences, University of Southern Mississippi; and Peter Morton, Ph.D., Department of Earth, Ocean and Atmospheric Science, Florida State University.
This research was funded by the U.S. NASA Ocean Biology and Biogeochemistry Program (NNX14AL98G, NNX16AR74G) and Ecological Forecast Program (NNX17AE57G), NOAA RESTORE Science Program (NA17NOS4510099), National Science Foundation (NSF-OCE 85–701 15492 and OCE 88–12055) and a Red Wright Fellowship from the Bermuda Biological Station.
Depuis 2011, cela n’a échappé à personne que la partie tropicale de l’océan Atlantique fait face à une prolifération importante de sargasses. L’une des explications pointées est l’augmentation de nutriments (azote, phosphore et silice) provenant des rivières et liée aux changements climatiques et des usages des sols ainsi qu’à l’accroissement de l’urbanisation.
Les flux de nutriments des trois grands fleuves Amazone, Orénoque et Congo, suivis par satellite et par des mesures de terrain, n’auraient pourtant pas véritablement augmenté sur les 15 dernières années. Si la déforestation et la pollution sont une réalité très préoccupante, il apparait que des changements hydrologiques ne sont pas directement responsables de la prolifération des sargasses. Des études doivent continuer pour mieux comprendre les sources de nutriments qui favorisent le développement du phytoplancton et des sargasses dans la région tropicale.-
Editor’s note: The Source is republishing this InfoAmazonia story to highlight the growing economic and environmental threat of sargassum to the U.S. Virgin Islands and wider Caribbean region. Sargassum has again begun washing up on the territory’s beaches in April 2021. Previously the Source has reported on the spread of sargassum becoming the new normal.
A decade after the first sargassum blooms were spotted in the South Atlantic, these massive brown mats of macro-algae represent one of the largest ecological threats to the Caribbean, a megadiverse region whose tens of millions of inhabitants heavily depend on tourism and natural resources.
The coming year looks like it will be particularly bad, scientists are predicting. The floating sargassum bloom has shown accelerated growth since December of 2020, according to satellite monitoring reports that carried out by the University of South Florida jointly with NASA.
“The crisis is coming again for the Caribbean coasts,” warns Alejandro Bravo Quesada, specialist in marine oceanography and the Director of Ocean Solutions Mexico.
According to the reports, the amount of sargassum in the sea went from 3.2 million tons in December to 4.6 million tons in February. This amount is four times higher than reported for the same period in February of last year.
The University report indicates that this amount is comparable to the 2018 and 2019 records, when the brown sargassum tide completely transformed the Caribbean coast of turquoise waters and white sands.
“The sargassum phenomenon has begun to show some behavior patterns since we started to observe it more carefully, in 2015. The blooming season begins early in the year and has its highest peaks in the summer, showing a significant decline in the winter. We see that it has annual periods of greater intensity, then less and it rises again. These patterns indicate that most likely this year we will have large quantities,” explains Bravo Quezada, who is a member of the group of scientists who advise the Mexican state government of Quintana Roo about this phenomenon.
With a current extension of 86 kilometers, the sargassum belt is currently located to the south of the Lesser Antilles, which have already experienced minor landfalls. The dynamics of the maritime currents and the trajectory the floating mats have followed in previous years allow experts to infer that this sargassum would travel through the Caribbean region until it meets the Mexican coasts and then heads to South Florida.
For the last six years, tourists have been welcomed at Caribbean destinations by images of brown water, a foul odor, dead marine fauna and tons of accumulated algae on the coast, especially when sargassum landfall became more intense.
But bad sights and smells are only the tip of the iceberg of an “environmental disaster” at regional level if it is not managed soon, warns Rosa Elisa Rodríguez, a researcher at the National Autonomous University of Mexico (UNAM, by its Spanish acronym) Institute of Limnology and Marine Sciences.
The sargassum piling up on the coasts already impact seagrass meadows, mangroves, reefs and beaches, in addition to representing a threat to the economy of regions that essentially live on tourism, such as Quintana Roo (Mexico), the Dominican Republic, Jamaica, Belize and Aruba, among others.
However there is no agreed figure on the economic consequences about the sargassum arrival in the Caribbean.
During a talk at the University of West Indies, Edmund Bartlett, co-chair at the Global Tourism Resilience and Crisis Management Center, said that the annual cost of cleaning-up the Caribbean islands was around 120 million dollars.
Quintana Roo’s Government reported that in 2018 were removed 522,226 tons of sargassum from the public beaches and coastal zones, which represented an investment of 17 million dollars. For 2019 and 2020 there are no concise figures.
The mentioned amount of money is aside from what each hotel allocates to clean-up its beach-front every day, and this cost could be up to 60 thousand dollars annually for a medium size hotel, according to hotel owners.
Nevertheless, this figure varies over the time, depending on the beach size, its location and sargassum quantity.
Those figures only include cleaning costs without taking into account a possible drop in tourist arrivals.
The environmental and economic impacts have led to a desperate search for solutions from the scientific community and governments in many countries, but have yet to lead to effective actions.
In June of 2019, the first International convention to address the sargassum problem was held in Cancun, Mexico. At this meeting, representatives from 13 Caribbean countries committed to working together through public policies and knowledge production to deal with this phenomenon. The commitment was endorsed in a second meeting held on the island of Guadalupe in October of the same year.
Nevertheless, it is a complex problem to address, starting with its origin, says biologist Adán Caballero Vázquez of the Yucatan Center for Scientific Research (CICY, by its acronym in Spanish), who has studied the invasion of this macro-algae and its associated fauna for many years.
An expert in invasive species of flora and fauna, Caballero Vázquez says the sargassum that reaches the Caribbean does not come from the famous “Sargasso Sea,” located in the Bermuda Triangle area, and that even the species of algae is different.
It is a relatively new phenomenon of sargassum accumulation between the coasts of Brazil and Africa, in the South Atlantic, which some have called “New Sargasso Sea.” Alfonso Aguirre Muñoz, former Director-General of the Group of Ecology and Conservation Islands, explains that the sargassum biomass originates along the eastern Atlantic coast of Africa and the mouth of the Congo River and is swept along by marine currents that circulate through tropical latitudes, passing across the mouth of the Amazon River where it is fed by the increasing outflow of nutrients, along the northeastern coast of Brazil, finally reaching the Caribbean Sea and continuing on to the coast of Florida through the Gulf of Mexico.
“New Sargasso Sea”
Hypotheses about the origin of this New Sargasso Sea and its arrival to the Caribbean Sea are many, but experts agree that several factors are probably at work.
Rosa Isela Rodríguez Martínez, one of the first scientists to study the behavior of this algae, points to the increase in ocean nutrients originating from the discharge of pollutants into the mouth of the Amazon River, in addition to the Sahara dust that gets deposited in the eastern Atlantic and which flows along the westerly marine currents, including among their components algae “fertilizers” such as magnesium, calcium, phosphorus, and nitrogen.
Another story in this series produced by journalists in Brazil looks more closely at the ecological trends in the Amazon region, documenting how increasing deforestation since 2012 and agricultural production are believed to be increasing sedimentation of the river and nutrient outflows into the Atlantic. Increasing ocean temperatures resulting from climate change also benefit algae growth, note the experts. Adán Caballero Váquez explains that the explosive growth of sargassum over the past decade could be the sum of all these factors.
According to Caballero Vázquez, algae from the original Sargasso Sea are poor in nutrients, while those from the New Sargasso Sea have high concentrations of nutrients and heavy metals.
Caribbean waters are historically “oligotrophic”, meaning they typically have a very low nutrient load, hence its picturesque blue color and legendary transparency. But when the sargassum algae reach the coast, they completely transform ecosystems and landscape.
Visible and invisible impacts
In terms of environmental impacts, the primary problem is algae rotting in the sea, which produces a foul-smelling odor and releases liquids known as “leachates” that load the water with nutrients.
In marine zones with high sargassum concentrations and the brown tide effect, meadows of seagrass began to die, observed the academic, since they need oxygen and light to survive.
Seagrasses are highly important to the coast because they serve as refuges, habitat, and food for hundreds of marine species. In addition, they protect the coast from erosion and reduce the sea’s strength during storms and hurricanes.
In 2018, Rodríguez continues, scientists began to register a rising death toll of marine species — fish, crustaceans, octopuses, sea cucumbers — in zones with high sargassum concentrations on the beaches. A study led by the scientist showed that in the accumulated sargassum along the beaches of Quintana Roo were found 76 corpses of different animal species, among fish, crustacean, octopuses and sea cucumbers.
Gonzalo Merendiz Alonso, Executive Director at Amigos de Sian Ka’an, explains that the sargassum is also affecting mangrove forests, wildlife refuges, habitats and the breeding of hundreds of fish species.
Since 2015, some Caribbean countries have taken measures to mitigate the effects of sargassum on the coasts. In Mexico, the Secretariat of Environment and Natural Resources (Semarnat, by its acronym in Spanish) issued a series of guidelines for the treatment of algae that turned into non-formal standards. For example, burying sargassum in the sand is prohibited – a recurring practice until 2018. There is a specific machinery allowed to collect sargassum, so it does not damage sea turtles and algae must be taken to a proper waste disposal.
However, the coasts already show visible impacts.
Hydrogeologist Guadalupe Velazquez, from the Research Center for Sustainable Development (Cides, by its acronym in Spanish), indicates that in the town of Puerto Morelos in Quintana Roo, beaches have suffered from serious erosion and compaction, because in the process of removing algae, many kilos of sand are also taken away, in addition to the pressure caused by the continuous crossing of machinery.
“When there are meteorological phenomena, it can be seen how the sea is gaining more and more ground on the coast,” adds the expert.
The problems caused by the excessive landfall of sargassum do not end when it is taken off the beach, because to date only one municipality, Puerto Morelos, has set up a final disposal site with a geomembrane to avoid the pollution of soil by leachates. Other municipalities, in the best of cases, dispose of sites specifically set up for this type of organic waste, located far from urban zones.
Alejandro López Tamayo, president of the Centinelas del Agua (Water Sentinels) organization, explains that the Yucatan Peninsula region in Mexico has a system of porous karstic ground, with an aquifer a few meters deep. Without appropriate processing, the leachates released during the rotting of sargassum rotting easily seep into the water table and the aquifer, polluting the soil and water, explains López Tamayo.
Another study led by the academic Rosa Rodríguez Martínez also shows the presence of polluting elements in the sargassum, such as arsenic, copper, manganese, and molybdenum, which in high concentrations can be harmful for humans, local flora, and fauna.
Scientists warn that, in the long term, the effects of sargassum in the main coastal ecosystems could produce devastating impacts on the Caribbean Sea and in the economies of the countries that make up this region, which is highly dependents on their natural resources.
Mexico’s management to deal with sargassum
For five years, Mexican government has failed to contain or reduce the problem. During the first years, Quintana Roo’s government, municipalities, and hotels were in charge of the beach cleaning work. That entailed investments of many millions of pesos to build barriers, purchase machinery, pay workers and transport and dispose of the waste.
In 2019, the Quintana Roo´s Government Advisory Council to manage sargassum was created, and in conjunction with members of the scientific community and business owners, several initiatives for the integrated management of sargassum were started, from monitoring and collection at sea, on the beaches, to final disposal and even industrialization (turning the waste into useful by-products). The proposed projects would be funded with a joint contribution of the three levels of Government.
However, because of some conflicts among the stakeholders and the outrage arising from suspected interference from an official in the drafting of contracts — whose connection to the alleged scandal was not verified — the main project nicknamed “Caribbean Shield” was discarded.
Manuel López Obrador, Mexico’s President, ordered the Secretariat to take charge of the issue, which he said he “inherited from other governments” and which he claimed was “amplified” to criticize his governance.
After the announced decision in June of 2019, the Secretariat of the Navy (Semar, by its acronym in Spanish), took the lead in coordinating strategy with Quintana Roo’s Secretariat of Ecology and Environment (SEMA, by its acronym in Spanish) and the municipalities along the coastline.
One of the first strategies implemented by the Semar was the collection of sargassum in the open sea, following up on the Advisory Council’s recommendations. Five deep draft vessels were assigned to carry out this task.
Nevertheless, the support from the federal agency is minimal and comes with high operational costs. From 2019 to September 2020, the Semar reported collecting 304 tons of sargassum in the sea, barely 1.6 percent of the 18,317 tons collected on public beaches by municipal city councils in Quintana Roo.
During seasons with a surge of sargassum, beginning at dawn hundreds of temporary workers hired by the city councils and hotels pick up tons of wet algae, to try to avoid having it rot on the beach. “When the tourists come to the beach, he has to see everything clean,” is the instruction a crew chief yells.
Sargassum represents a threat to the Mexican Caribbean tourism industry, the most powerful in Latin America. “If a prompt solution to the problem is not sought, consequences for the future could be fateful,” warns Rodríguez Martínez.
Quinta Roo receives 14 million visitors annually, with a contribution to the national Gross Domestic Product of more than 60 billion pesos, according to reports from the Tourism Secretariat (Sectur, by its acronym in Spanish).
In order to lead the Latin American tourist market, destinations such as Cancun, Playa del Carmen, Tulum and Cozumel offer the beauty of their beaches as the main attraction.
In beaches with high sargassum concentrations, especially in the bays and reef lagoons where the algae become stagnant, the color of the water has changed from turquoise to brown, completely changing the landscape even when is not the sargassum season. Examples of this phenomenon can be found on the coasts of Puerto Morelos and Xcalak, as well as the bays of Sian Ka’an. In addition to the environmental problems that this represents, brown waters, like a polluted river, are not attractive to national and foreign tourists.
Solutions, still uncertain
Currently, there are several proposals to harvest and process the sargassum in the Caribbean, a measure that would solve part of the problem by transforming the algae into a resource with commercial value, according to promoters.
One of the most advanced projects is from the company Dianco Mexico, which will start operations in Cancun in mid April to transform sargassum into biofertilizer. Another product they plan to produce is cellulose.
Héctor Romero, the company’s CEO , affirms that the factory will have the capacity to process up to 600 tons of algae.
Other proposals suggest the algae can be used in the livestock feed industry, in the cosmetic industry and to generate biofuel.
To Adán Caballero, the research available to date on the algae of the New Sargasso Sea is not enough to establish its potential use, because the contaminants it contains could represent a risk to public health.
“The original Sargasso Sea has several associated industries and large studies that support the use of its algae, but the studies we have on the sargassum affecting the Caribbean are still emerging,” added.
Meanwhile, the tide of sargassum keeps rising.
This story was produced by InfoAmazonia with support from Internews’ Earth Journalism Network and in partnership with the EarthRise Media; it also appears in Arestegui Notícias, from Mexico. It was translated by Lucy Calderón and edited by James Fahn.
Key News – Environment
Facts First: Explaining Sargassum by Rumya Sundaram
November 15, 2019
If you’ve walked on the beach at all this year, you know what sargassum looks like. But beyond the unsightliness and the smell, what is really happening here?
What is sargassum?
Sargassum is a type of macroalgae that floats at the ocean’s surface. Each stipe (that is, stalk) and frond can be several meters in length. Many species create small berry-like attachments filled with air, which help them stay afloat.
There are two species of sargassum to consider in the Atlantic and the Sargasso Sea (although there are hundreds of species worldwide): Sargassum fluitans and Sargassum natans. S. fluitans tends to be the more common species.
The Sargasso Sea is a vast area of about 2 million square miles off the East Coast of the United States and is a unique habitat for dozens, if not hundreds, of species of marine animals including fish, shrimp, crabs, baby sea turtles and many others. The sea itself is distinctive in that it has no land barriers and instead is contained solely by ocean currents.
The sargassum problem
Sargassum is not new to beachgoers in South Florida and the Caribbean. It has always been a part of the scenery, and it plays an important role in beach ecology.
As early as 2012, researchers in the Caribbean started seeing an increase in the amount of sargassum washing up. In 2011 satellite imagery used for spotting algal blooms had revealed a marked increase in sargassum.
By 2015 sargassum was piling up feet deep on Caribbean beaches. This continued to a nadir in 2018, when financial strain for many countries in the Caribbean, Mexico, and cities or counties in Florida, both through potential loss of tourism and the cost of hiring companies to remove it.
Satellite imagery shows the Great Atlantic Sargassum Belt, a bloom stretching 5,500 miles from the Gulf of Mexico to the western coast of Africa, has been growing. Imagery studied from 2000 through 2018 showed more of the macroalga showing up in new areas in 2011, before which the influx of these large amounts of sargassum were not observed in the Caribbean.
A research team who discovered the bloom, with members from University of South Florida and Georgia Institute of Technology, also determined that its seasonal formation has both natural and unnatural contributing factors. Specifically, it is naturally fed in the winter by upwelling from deep in the ocean off the eastern African coast which feeds nutrients to the sargassum. However, increased nutrient runoff and discharges from the Amazon River from deforestation and fertilizer use, predominantly nitrogen and phosphorus, have been unnaturally feeding the bloom also. Both increased deforestation and fertilizer use in 2010 coincide with the increase in sargassum observed by satellite the following year.
But the problem might be even more complex.
In July of this year, University of Miami Rosenstiel School of Marine and Atmospheric Science released a study which showed that aerosolized phosphorus from smoke in Africa is also unnaturally feeding nutrients to the Amazon. This smoke comes from biomass burning including “land clearing, brush fires and industrial combustion emission.” The transport of aerosolized African dust from the Sahara Desert depositing nutrients in the Amazon, tropical Atlantic Ocean, and Southern Ocean has been studied for decades. The study shows these newer aerosolized particles from African fires may now make up a major part in the normal movement of airborne nutrients from the African continent (though it did not specifically link the increase in aerosolized phosphorus to the increase in Atlantic sargassum).
Effects on the environment
Sargassum washing on shore is a natural process. The movement onshore adds to beach stabilization and transport of marine nutrients to terrestrial environments.
The floating mats of sargassum in the water, particularly in the Sargasso Sea, are key habitats and nursery grounds for a number of species. For example, loggerhead sea turtles hatch from their native beaches and make the journey out to the Sargasso Sea where they live, feed and gain protection from sargassum as they grow. A frogfish known as the Sargassum fish, (scientific name Histrio histrio) has evolved to live in floating mats of these macroalga.
There has been some evidence that sargassum buildup on beaches may cause problems in nesting or hatching of sea turtles. During large-scale buildups on nesting beaches in Antigua, fewer or no nests were observed, indicating that the large amounts of sargassum may impede or deter females from nesting in those areas.
Once a nest is hatched, large amounts of sargassum may prevent or hinder baby sea turtles from reaching the sea. They may also get mired in or confused by floating mats which can cause them to wash back to shore or starve. However, not enough research has been done to provide definitive conclusions of the effects on sea turtles yet. So far, in some areas such as Bill Baggs State Park, which does not manually remove or bury its sargassum, there appears to be little effect on hatchlings making their way to the sea.
In other areas of Florida and the Caribbean, there have been reports of large amounts of sargassum causing the deaths of many animals (including sea turtles) by preventing them from coming up to breathe or trapping and entangling them.
One major problem which has been documented are changes in the Caribbean in seagrass meadows. Large mats of macroalga can block out the light, causing photosynthesizing seagrasses to die out and be replaced by other species, changing the seascape entirely. As the sargassum dies and decomposes, it removes oxygen from the water, which can cause fish and other organisms in the area to suffocate. All of these issues have been shown to change the water quality, negatively impacting some coral species.
Most governments have relied on removal techniques using bulldozers, trucking to landfills, composting when possible or burying it. However, the costs of these actions can quickly build up into the millions, making them financially prohibitive.
How do you solve a problem like sargassum?
The current solution of burying it comes with its own pitfalls and may possibly be responsible for some of the high bacteria counts lately – a point made by Kelly Cox of Miami Waterkeeper at the Nov. 5 workshop.
When the sargassum is exposed to the sun, it dries out and decomposes relatively quickly (although the process is slower when it is piled several feet deep). When it is buried, it decomposes more slowly and remains damp and warm longer, creating a possible breeding ground for enterococci bacteria, which could then leach back into the water, and may exacerbate the bacteria problem that Key Biscayne beaches have been experiencing.
Differences in coastal currents can also dictate how and where sargassum lands. In the case of Key Biscayne, the southern end around Bill Baggs has more flow through, possibly preventing very large amounts from accumulating. The northern end, on the other hand, tends to accumulate quite a bit more (this may also account for the difference in bacterial counts along the East Coast of the Key).
As of now, no removal technique has proven better than any others, and the environmental impacts are still being investigated and researched.
As many scientists are now saying, sargassum blooms may become the new normal.
Growing up by the sea, I am used to find Sargassum floating in the water or washed up on the beach. We have always seen Sargassum and other seaweeds and plants which presence is normal in the marine and coastal environment. However, the quantity of Sargassum that has arrived through the Great Caribbean region since 2014 is unprecedented, as well as the consequences. That’s why there are studies being conducted to understand what this phenomenon is and how to deal with it, not an easy task. I had the opportunity of listening to a senior researcher of UNAM (Mexico’s National Autonomous University) and expert in seagrasses and tropical marine vegetation, she works at the Tropical Seagrass Systems Laboratory in Puerto Morelos. Many of the questions I had were answered during her talk at a local Planetarium. I am hereby sharing them with you.
I have recently learned that the Sargassum arrival has completely changed the dynamic of some very important coastal environments in our region and we all need to take a better look at the issue if we want to continue enjoying our beaches and reef in the future. The problem is not only how tourists perceive the beach and where we are putting the sargassum after it’s collected.
I used to think that Sargassum affected the tourism industry because visitors have high expectations and find it hard to enjoy the beach full with this brown colored alga. I have recently learned that the problem is way more worrying than the holidaymakers and a 10 day vacation in the Caribbean. We are not talking about the way the beach looks anymore, we are talking about an environmental issue that is not about to be solved any time soon. Sargassum might be a problem that our grandchildren (which aren’t born yet) will have to fix. If you want to learn more, keep reading.
Sargassum might be a problem that our grandchildren (which aren’t born yet) will have to fix.
What is Sargassum?
Sargassum is an alga that lives most of its lifecycle floating on the surface of the ocean. Sargassum does not originate on the bottom like other kinds of algae, it reproduces and grows while drifting with the currents and floats in the water column until it reaches the coast where, usually, exits with the movement of the water (waves and currents) onto the sand. It then dries, decomposes or simply goes back to the water and continue on floating.
We have two types of Sargassum in the Caribbean: Sargassum natans and Sargassum fluitans. Both species look almost exactly the same to the untrained eye.
Sargassum and seagrasses are NOT the same thing, they are totally different kinds of living organisms. Seagrasses are plants with seeds, flowers and fruits (yes, underwater flowers AND fruits! While Sargassum is an alga.
Sargassum is good…
In the open ocean, islands of Sargassum are formed as the currents reassemble large quantities and keep them together as a floating island thanks to the gyres. A gyre is a system of currents that forms a “cycle” movement. In a gyre, the water on the surface is pushed by the wind in “circles”, it turns and turns, keeping whatever floats in it within that same area. You must have heard of the Sargassum Sea, this place holds large quantities of Sargassum, in normal conditions sargassum stays within the gyre and only occasionally “escapes” the gyre, hence sargassum has been found in the Gulf of Mexico prior to the Sargassum crisis. However, the Sargassum we have found in the Caribbean since 2014 has not been proved to come from that place. More on this further down.
Hundreds of species or living organisms can be found within these masses of Sargassum, juvenile fish find shelter, crabs and other crustaceans drift with the Sargassum in the open ocean while they find food and a healthy habitat among these floats. Turtle hatchlings spend a great deal of time swimming with the Sargassum as it represents the only protection they can find during their first years in the ocean and Sargassum provides an ecosystem that guarantees food, shade and a home for many.
Sargassum has been documented since a really long time. Columbus mentioned it in his discoveries as far back as 1492, when he arrived in the American continent, and many explorers, scientists and researchers have known of its existence for a long time. Sargassum is part of the marine environment and has ecological value, when the quantities that reach our beaches are normal.
Sargassum is bad…
In recent years, we experienced an unprecedented arrival of Sargassum, this phenomenon reached the entire Caribbean region, the coast of Central and South America and even Africa. The amount that washed up on the white sand beaches was a big shock for everybody: tourists, locals, government, tourism industry, travel industry, scientists, press, etc. Literally, nobody had ever seen anything alike (although we all knew Sargassum, we had never seen this much). The first reaction was to remove it, but rather quickly people realized this was a task for thousands of people. Due to the fragility of the coastal environment, this had to be done by hand. Men and women worked endless hours to remove Sargassum from beaches and seagrass meadows. Only to find that overnight the quantities had increased and there was more to arrive.
So, how an alga that is supposed to be good and provide much value for the environment, as described above, can be such a stinky business to deal with from one day to another, and why our feelings are mixed between concerned and overwhelmed?
“The excess of Sargassum is detrimental to the environment, just like any excess. Excess of sugar is bad. Excess of Sargassum, is also bad” Brigitta van Tussenbroek
What are the immediate effects of Sargassum?
The islands of Sargassum accumulate near the coast where other marine ecosystems thrive, for example: seagrass meadows and coral reefs. It causes a bad smell and releases Hydrogen Sulfide.
Big amounts of sargassum can prevent turtles from nesting and can make it very difficult, if not impossible for hatchlings to reach the ocean from the nest.
Sargassum can cause beach erosion by altering the structure of the reef lagoons, by suffocating the seagrasses and by creating unbalance in the health of the beach ecosystem.
Seagrasses serve in fixing sediment and keeping sand in place, when seagrasses are gone, the sand might erode and the water will rise its level, recently we have experienced unprecedented levels of beach erosion too and it might be linked to the arrival of massive sargassum amounts.
Sargassum can be dangerous for our health, respiratory issues have been reported due to the concentration of gases that the decomposing Sargassum provokes.
Sargassum blocks the light that normally penetrates the surface, preventing many organisms from completing their photosynthesis process, therefore diminishing the amount of oxygen they produce (yes, the oxygen we breath is produced by seagrass and coral reefs in considerable amounts).
Who else is affected by the Sargassum?
Many living organisms are affected by the massive arrival of Sargassum.
Seagrasses need light to conduct photosynthesis, if big islands of Sargassum cover an extended area of seagrass, these will lack the sunlight and will not be able to produce oxygen which they normally release into the environment during the day, helping other organisms live (including me and you).
Seagrasses are plants, during the day they produce oxygen, but during the night they consume oxygen (since there is no sunlight available to produce it), being covered over long periods of time (by a shade like the one Sargassum islands create near the coast) will create a “night” environment where seagrasses only consume the oxygen to live -day or night- therefore altering the natural process of oxygen production. This, together with the bacteria involved in the decomposition of Sargassum will cause the depletion of all oxygen available in the water and the seagrasses will die along other organisms. When an environment lacks of oxygen, it is called apoxic. This is also a very smelly phase and if you’ve been in the Caribbean recently you will remember a stinky smell if you walk near the beach.
But, what about the fish?
Fish and other marine organisms are able to flee (in most cases). As the environment becomes hypoxic (low oxygen levels) or anoxic (no oxygen at all) animals move to healthier parts of the reef lagoon or the reef. But many organisms, such as seagrasses cannot just pack up and leave. Therefore, they die. Entire seagrass meadows have been swept dead due to the extended presence of Sargassum. But, who can live in a hypoxic environment then? Some algae live in more flexible conditions than seagrass, which is more sensitive to changes in the environment, and therefore can tolerate conditions like the ones the arrival or Sargassum produced, therefore it starts gaining territory in spots where seagrass decays at really fast rates.
So, what we would typically see, is that the seagrass, as its health deteriorates, gets “invaded” by the algae which will cover entire areas in a matter of days, and will suffocate the little chance it has to recover.
But, wait, why do we care about seagrass?
(I thought a dirty beach was already a big problem to deal with…)
When an excess of nutrients is put in an environment, such as in the seagrass meadows, the growth of the plants is altered. We know that Mexico has a less than optimal residual water management and we know for a fact that part of the residual waters of coastal communities, like Puerto Morelos, ends up in the ocean through filtration and leakages into the phreatic layer (because water in the Yucatan Peninsula is underground due to the porous ground which is mainly limestone).
Seagrass meadows are an essential link in the health of the ocean and the coral reef. They provide food, shelter, and a complete habitat for species that spend their life (or at least part of it) next to coral reefs.
When the Sargassum reaches the coast and accumulates near the beach, it starts decomposing, producing extremely high amounts of nitrogen and phosphor, these two elements are needed for many living organisms to thrive, in controlled amounts. These two elements are considered nutrients. However, the excessive arrival and decomposition of Sargassum increases the levels of nutrients that the living organisms can tolerate. We already know the levels of nitrogen and phosphor are considered high due to the gaps in residual water management, but scientists discovered that the arrival of Sargassum increased that amount even more, creating a crisis in the balance of an already fragile ecosystem.
Seagrass meadows are feeding grounds for turtles and manatees, they are also essential for many species of fish that are important for the economy (fisheries, tourism, etc.), and they are used by conch, rays, and other organisms during different stages of their life. If seagrass meadows are gone, all those other organisms will lack food, protection and a healthy environment to continue their functions within the chain, therefore disturbing food chains and altering its normal balance. Moreover, the economy can collapse as the fisheries and tourism rely on the health of the marine ecosystems (if there are no seagrass meadows there will be no more reef to snorkel at all!)
How long does it take to rehabilitate the seagrass meadows and reestablish that balance?
According to dr. Brigitta van Tussenbroek, it will take at least 10 years to rehabilitate these environments that has been affected due to the effects of Sargassum. It might take even longer, depending on the damage (up to 50 years), however the most worrying effect would be not to be able to recover them at all, meaning that if the seagrass is gone completely this might turn into a situation that has no return point. Knowing this puts your worries in perspective, most people talk about a crisis because tourists are unable to enjoy a white beach, just like the ones in the brochures, an aesthetic disturbance. But if we think about it, your 10 day holiday might be ruined due to the arrival of Sargassum. however…
In the Mexican Caribbean we might end up with 50 years of damage, if not permanent damage and loss of these incredibly rich and important habitats.
As dr. van Tussenbroek says: 4 years after the first massive arrival of Sargassum, we’re still in the beginning of this journey to understand what we can do about it, the problem has just started.
What else do we know about sargassum?
Sargassum can duplicate its biomass in about 18 days. Experiments were conducted where Sargassum was collected in an enclosure and was left floating, two weeks after, its weight accounted for twice of the initial amount.
Sargassum in the Caribbean DOES NOT come from the Sargassum sea, the journey of Sargassum has been studied and researched, and tracked back with satellite imaging and other technologies to the coasts of Brasil, where we now have a newly baptized “Small Sargassum Sea”. Sargassum travels north with the currents and is pushed by waves and wind, it enters the Great Caribbean then making its way to our coasts, and eventually, even crossing the Yucatan Channel into the Gulf of Mexico, that’s one long journey!
Scientists and government do not have enough data to make an accurate prediction about the future yet, but we know that the increase in Sargassum and other actual environmental issues are produced by the global changes we live in our times, namely global warming.
When Sargassum is a healthy environment floating in the column of water it is called Golden Tide, however after the later phenomenon in the Caribbean, it has been granted the less romantic name “Brown tide”.
Sargassum DOES NOT become sand, if that was the case we would have solved the beach erosion problem. Sand in the Caribbean is almost exclusively organic, crushed coral, shells and skeletons of other organisms become sand thanks to different processes. Sargassum does not have a link to the production of sand in the Caribbean.
Sargassum does not sting! However, some tiny organisms that live in the Sargassum may provoke a reaction or a rash, this does not come from the alga itself but from its passengers!
I hope I have answered some of the questions that you might have had regarding Sargassum. We’ve all had those questions and often we find it hard to get trustworthy information. The national university (UNAM) has a research station for marine sciences in Puerto Morelos since 1981, where they study Sargassum and its effects in our marine environment, especially on seagrass meadows. It was a pleasure to listen to Brigitta van Tussenbroek, one of their senior researchers, who has studied sea grasses since 1990 and to learn about her research and encouragement for government and industry to work towards integrative solutions and more importantly, anticipate and prepare to be resilient about these changes we experience.
El sargazo y el “síndrome blanco” son dos factores que están causando alta mortalidad de las colonias de coral del Arrecife Mesoamericano, sin que hasta la fecha se tengan protocolos o procedimientos para frenar los daños, manifestó la Dra. Claudia Padilla Souza, investigadora del Centro Regional de Investigación Acuícola y Pesquera Puerto Morelos.
Explicó que en el mar, el problema es que los sitios donde se da la afectación por sargazo hay una mortalidad muy alta de corales. Son áreas que después se tienen que intervenir con siembra para restituir su condición original, el problema es mayor en los arrecifes costeros, como el de Puerto Morelos.
Ahora tenemos la complicación del “síndrome blanco” que, en mi opinión, es consecuencia de un estrés en el que están los corales por muchas causas y ahora se incrementa por la presencia del sargazo, que rompe un umbral y por eso muestran procesos de enfermedades que anteriormente no tenían.
“El ´síndrome blanco´ es relativamente nuevo, no se sabe mucho del origen, el patógeno o el origen de la enfermedad y tampoco hay una cura o procedimiento para evitarlo”,explicó.
La entrevistada, quien tiene a cargo el proyecto de producción de corales y programas de restauración de arrecifes coralinos, señaló que ese programa empezó en 2009 con las primeras pruebas y sistemas de cultivo, a fin de producir los corales necesarios para su siembra en los sitios donde están deteriorados.
Con el proyecto han alcanzado una producción de 8 mil colonias de coral
Fue así como alcanzamos una producción de 8 mil colonias de coral de 8 diferentes especies y se trabajó también en la producción de “reclutas sexuales” para tener mayor diversidad genética de los organismos.
Sin embargo en cuanto al tema del sargazo, afecta directamente a los sistemas de cultivo porque se toma agua del mar para alimentarlos y, cuando hay presencia del alga , se torna turbia, con materia orgánica en descomposición que entra a los cultivos. Eso obligó a hacer modificaciones importantes en la infraestructura.
En el 2018 sembramos 3 mil 334 colonias en 1 mil 840 metros cuadrados y este año esperamos que la siembra y el área de intervención sea mucho mayor, prosiguió.
Ahorita trabajamos en 12 sitios de cuatro arrecifes, entre éstos el Parque Nacional Arrecifes de Puerto Morelos y el Parque Nacional Arrecife de Isla Mujeres y Punta Cancún.
MIAMI.- Para este año, la llegada de sargazo al Caribe será masivo, según pronostica la Universidad del Sur de la Florida. La situación podría ser similar a la de 2018 o tal vez aun peor, según las imágenes satelitales. « El último diciembre mostró una cobertura total de sargazo de 173 km2, en comparación con una media histórica de 59 km2 entre 2011 y 2017 », indica el informe.
« Estamos al tanto de las imágenes que sugieren que el sargazo estará en la región muy pronto -cuenta Hazel Oxenford, profesora de ecología marina para el centro de investigación de la Universidad de las Indias Occidentales en Barbados-. Dado que es un fenómeno nuevo, no conocemos sus estaciones todavía. No obstante, parecería que la zona de abarque se está expandiendo en tiempo y forma », detalla.
Aun no hay explicación cierta del aumento. Una de las teorías lo atribuye a una nueva región de origen en el Ecuador donde las algas se forman, se consolidan y son periódicamente desprendidas. El patrón de retención o liberación varía de un año a otro y la cantidad de sargazo florece cuanto mayor es la temperatura del agua y los nutrientes. Los científicos aun no definen la explosión, pero la mayoría confirma que es consecuencia de la acción humana.
« El sargazo ha sido siempre un ecosistema marino en el Atlántico. En efecto, una enorme región de la parte oeste del océano se llama Mar Sargazo por la prominencia de algas », explicó James W. Fourqurean de la Universidad de la Florida. De cualquier manera, en los últimos cinco años ha habido un enorme incremento que llega al Caribe que está lavando las costas y ha degradado playas y aguas costeras.
Industria y viajeros, en alerta
La industria hotelera ya está en alerta. Desde la Asociación de Hoteles de Cancún y Puerto Morelos surgió la iniciativa de lograr un compromiso con los 19 países del Caribe afectados y realizar un congreso donde se unifiquen esfuerzos para encontrar una solución. Hay quienes plantean usar embarcaciones que succionen el sargazo del mar y lo compacten, mientras otros se preocupan por evitar que se reproduzcan en altamar.
El año pasado, el estado mexicano de Quintana Roo, que alberga a Cancún, además de limpiar las playas, colocó barreras flotantes de contención. En Miami Beach y Fort Lauderdale, la ciudad limpió el exceso de sargazo con tractores y también lo mezclaba con la arena para hacerlo menos invasivo. Pero no se puede hacer a lo largo de toda la costa: hay lugares con alta densidad de huevos de tortuga que están protegidos.
Hazel cuenta que la mayoría de los países están formando planes de respuesta contra estas algas, si bien es difícil su recolección en el mar. « Por otro lado, generalmente no es recomendable debido a los beneficios ecológicos del sargazo en mar abierto », explica.
Como respuesta a viajeros desconcertados, Christine Jimenez, francesa residente en Riviera Maya, creó la web www.sargassummonitoring.com. Gracias a sus mapas, los turistas pueden ver y enviar fotos de las zonas impactadas. « Pedimos que especifiquen fecha precisa y locación para proveer información confiable. El trabajo lleva tiempo, pero creemos que la gente ahorra mucho dinero para costear un viaje y no queremos que se desilusionen al llegar », dice.
Jimenez asegura que gran cantidad de sargazo impactará en el Caribe y México. « Dado que no todas las algas están bloqueadas por las islas del Caribe podemos confirmar que llegarán a la Riviera Maya en algunos días. No podemos dar fecha exacta dado que depende de los vientos y las corrientes », explica.
El programa de investigación SEAS ( www.seas-forecast.com) también ofrece información útil a quien esté pensando en visitar las playas cálidas. Creado en Texas, desde 2017 abarca a toda la zona del Caribe. En la web hay imágenes satelitales y pronóstico de la llegada de algas a las costas.
Possibility very high that large masses of sargassum currently in the Atlantic will find their way to the state’s beaches
Monday, January 14, 2019
Large quantities of sargassum are again likely to wash up on the beaches of Mexico’s Caribbean coast in 2019, according to an ocean researcher from the National Autonomous University (UNAM).
Brigitta Ine van Tussenbroek, a scientist at the university’s Institute of Marine Sciences and Limnology, said that satellite images from the University of Florida show that there are currently large floating masses of the brown seaweed in the Atlantic Ocean between southern Africa and Brazil.
The coast of Quintana Roo at Chetumal, Tulum or Cancún could all be affected, van Tussenbroek said, although she explained that more detailed monitoring and modeling is needed to say with confidence which beaches would see large amounts of sargassum.
“If it’s in open ocean, the possibility of it arriving on the Mexican coast is very high although it depends on local atmospheric conditions, like trade winds, that carry sargassum to our beaches,” she said.
Van Tussenbroek warned that if the seaweed arrives in quantities similar to those seen last year, the impact on local ecosystems and tourism will be severe.
In 2018, tourism declined in some parts of coastal Quintana Roo due to the presence of unsightly and smelly sargassum on beaches that draw visitors because of their usually pristine white sand.
Van Tussenbroek said that authorities at all levels of government need to work together to establish efficient and environmentally-friendly methods with which to collect sargassum before it reaches the coastline.
“In Quintana Roo, the tourism sector is extremely worried and actively participates . . in the mitigation [of the problem] but [the response] should reach another level, go beyond local action,” she said.
The scientist added that her suggestion is to “establish a state or national coordinating body, [that is] specifically dedicated to effective [sargassum] mitigation.”
Floating sargassum barriers were installed off some sections of Quintana Roo’s coast last year to prevent the seaweed from arriving on shore but authorities and citizens were still required to dedicate thousands of hours to clean the state’s beaches.
An unexplained invasion of Sargassum seaweed has been taking place on the coasts of Caribbean countries in recent years. Areas affected by the seaweed invasion include Barbados, Guadeloupe, Martinique, Puerto Rico, Saint Lucia, and Saint Martin.1, 2 The presence of this brown algae represents not only an environmental and economic disaster but a real threat to human health. After 48 h on the seashore, large amounts of toxic gas are produced through matter decomposition, including hydrogen sulphide and ammonia.3 The effects on humans of exposure to high concentrations of hydrogen sulphide have been described 4, 5, 6 and are of mounting severity with increasing concentration, leading to potentially fatal hypoxic pulmonary, neurological, and cardiovascular lesions. Although less documented, subchronic and chronic exposures can cause conjunctival and upper airway irritation, headaches, vestibular syndrome, memory loss, and modification of learning abilities. In the absence of any available specific treatment, management of hydrogen sulphide intoxication relies on supportive care, and prevention relies on individual protection.
Between January and August, 2018, doctors in Guadeloupe reported more than 3341 cases, and doctors in Martinique reported more than 8061 cases of acute exposure,7 among which three patients were admitted to intensive care. The number of consultations related to the effects of chronic exposure is also increasing in the local population. To mitigate this emerging airborne poisoning outbreak, the French Government has already promised €10 million to supply equipment that can be used to remove the seaweed within 48 h, to monitor hydrogen sulphide concentrations on the affected shores, to train doctors, and to assign experts in toxicology in affected areas. Despite this commendable first effort by the French Government, a mitigation plan to address this enigmatic Sargassum invasion should urgently be discussed at an international level to boost marine research, pool resources, and consolidate local political priorities.
We declare no competing interests. Written on behalf of the Research Group on Sargassum in Martinique.