Sargassum: Brown Tide Threatens the Caribbean

Sargassum being cleaned up at Sapphire beach on St. Thomas in 2019. (Photo by Alain Brin, Blue Glass Photography.)

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.

Sargassum descends on Hull Bay on St. Thomas in April 2021. (Source photo by Shaun Pennington)

“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.

This graphic shows the accumulation of sargassum in the Atlantic. Source: Optical Oceanography Laboratory. University of South Florida (Graphic courtesy of InfoAmazonia)

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.

During the 2019 summer season, tourists walk through the brown sargassum in Cancun beach. (Photo by Archive/Paola Chiomante)

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.

Location of the Sargasso Sea which records date back from more than 500 years, and the “New Sargasso Sea”, a recently discovered phenomenon. (Map courtesy of InfoAmazonia)

“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.

Sargassum piles up in Christiansted harbor on St. Croix in August 2019. (Source photo by Susan Ellis)

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).

Workers from the Municipality Benito Juárez, Cancun remove sargassum from the beaches. (Photo by Archive/Paola Chiomante)

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.


Facts First: Explaining Sargassum

Key News – Environment
Facts First: Explaining Sargassum
by Rumya Sundaram
November 15, 2019

Sargassum washed up on Crandon North earlier this summer (Key News/Rumya Sundaram)

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 natansS. 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.

Source : Key News

Sargassum for dummies

More than a holiday problem.

Species: Sargassum natans
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 floating in the open ocean amidst clear waters
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 frogfish (Histrio histrio) captured in Playa del Carmen in 2015 by curious beach staff during Sargassum cleanup labors, later safely released.
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.
Species: Sargassum fluitans
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…)
Photo: Tropical Seagrass Systems Laboratory, UNAM, Puerto Morelos
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?
Photo: Wikipedia
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.

Another bad year for sargassum seaweed forecast for Quintana Roo

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.

Source: El Financiero

Sargassum seaweed on Caribbean islands: an international public health concern

December 22, 2018

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.

Source : The Lancet

Alarma hotelera en el Caribe: gran arribo de sargazo llegará en 2019

Cancún | 17 de diciembre de 2018

La Universidad del Sur de Florida lanzó una llamada de alerta para el Caribe debido a las cantidades de sargazo que pueden arribar en 2019, que podrían ser mayores a las que afectaron en el 2018 a Quintana Roo, lo que causó un gran impacto para los hoteleros de Riviera Maya y Cancún, como reveló (Hoteleros de Riviera Maya admiten la bajada de precios y ocupaciones).

Rosa Rodríguez Martínez, maestra en ciencias de la Universidad Nacional Autónoma de México (UNAM), que forma parte del Comité Técnico, informó que con base a la distancia a la que actualmente están las manchas del sargazo, su arribo al mar Caribe mexicano puede ser en el primer trimestre del año, según recogió Sipse (Lanzan iniciativa para declarar desastre natural arribo de sargazo).

El informe de la universidad estadounidense fue analizado en Cancún durante la segunda reunión ordinaria del Comité Estatal Científico Técnico para el Sargazo, que encabeza la Secretaría de Ecología y Medio Ambiente (Sema), en el que estuvieron presentes los representantes de diversos sectores de la sociedad.

Las noticias no son buenas, porque la acumulación del alga marina que se ve actualmente en el centro y oeste del océano Atlántico representan “una señal alarmante” en el Caribe para 2019, lo que puede presentar una gran cantidad de sargazo a partir de enero, similar o mayor a la de 2018, detalla el reporte.

“Del sitio en donde está ahorita la mancha del sargazo tardaría aproximadamente 32 semanas en llegar la Península de Yucatán, y si se toma en cuenta que se reproduce en cuestión de días, la cantidad podría ser mayor a la del 2018, pues (las imágenes satelitales muestran que) en este noviembre hay más sargazo que el año pasado (y que fue el que recaló en el 2018 en Quintana Roo)”, explicó la maestra en ciencias.

Source :

BTB announces $1.5 Million sargussum relief fund & tax reliefs

Wednesday, October 31st, 2018

The Government of Belize has granted $1.5 million to help contain and control of sargassum in the municipalities of San Pedro, Caye Caulker, Placencia and Hopkins, which will be disbursed through the Belize Tourism Board. Minister of Tourism and Civil Aviation Hon. Manuel Heredia announced GOB’s assistance and other tax reliefs at a press conference the BTB offices in Belize City on Wednesday afternoon, October 31.

Minister of Tourism and Civil Aviation Hon. Manuel Heredia

To help the affected coastline properties at these destinations defray the cost of fighting the sargussum scourge, GOB has also agreed to waive two per cent of the of the 9 percent hotel tax due which all hotels pay in their monthly accommodation tax returns, a 22 per cent reduction in tax for these resorts. This tax relief will remain in effect for the months of October, November, December 2018, through January 2019.

Furthermore, GOB through the Ministry of Finance is providing additional tax relief by way of duty exemption on all materials, equipment and machinery which the affected properties at these four destination may choose to import to address the sargassum blight.

The government decided to offer this assistance on the recommendation of the Sargassum Task Force (STF) led by Minister Heredia, BTB chairman Einer Gomez and BTB Director of Tourism Karen Bevans. With the high tourism season about to start, The STF had assessed the gravity of the sargassum problem during several visits to coastal properties around the country, during which they had consulted with the owners of these seaside resorts to work out a joint strategy to deal with the problem.
During these visits, the BTB team came to recognize that the owners of these blighted resorts have had to incur significant expenses in cleaning up and disposing of the sargasssum scourge, and to erect barriers to deflect the sargassum off their beachfronts, all of which have increased their operating costs.

The BTB has promised all interested parties that the STF continues to research and consult in find a long term solution to the sargassum blight, and will continue to seek new ways to address this situation. They promised to update all interested parties as new developments arise. The STF includes the National Emergency Management organization (NEMO), Fisheries Department, the Tourism minstry, the BTB, the Coastal Zone Management Authority, Ministry of Health, the Belize Tourism Industry Association (BTIA), the Belize Hotel Association (BHA) and representatives of the tourism property owners in San Pedro, Caye Caulker, Hopkins and Placencia, and these village councils.

Source : The San Predro Sun

Record-Setting Sargassum Event Threatens Marine Life and Dive Conditions in Caribbean

The brown seaweed is more than just an eyesore on some beaches.

By Melissa Gaskill

Playa del Carmen

The spring and summer seasons brought a new style for the Caribbean’s iconic white-sand beaches — mounds and mounds of brown, stringy, stinky sargassum.

Divers encountered piles of the seaweed floating nearshore and ­covering beaches in Little Cayman, ­Barbados, ­Antigua, and other destinations throughout the Caribbean and western Atlantic. The unattractive, stinky seaweed kept many away from the sand and ­sometimes interfered with dive plans.

Sargassum is usually a diver’s friend. This vital marine ecosystem provides food, shelter, breeding grounds and nursery habitat for a wide variety of life, including fish, sea turtles and birds. As mats lose their buoyancy and sink, they feed creatures throughout the water column. The algae also add nutrients and structure to beaches.

But in recent years, sargassum has appeared in unusually great quantities, called blooms, and in places it typically did not. Research shows that blooms result from increased runoff of nutrients from land and warmer waters. Where they end up depends on wind, tides and ocean currents, which have shifted as a result of climate change.

But Hazel Oxenford, a fisheries biologist at the University of the West Indies in ­Barbados, points out that many areas ­remained unaffected.

“The news created impressions of whole islands covered by great, ­stinking plumes of sargassum,” ­Oxenford says. “But it comes ashore on ­windward coastlines, and most tourism infrastructure in the Caribbean is on the ­leeward side of islands.”

In Barbados, for example, sargassum inundated the east coast, which is generally considered too rough for diving.

And while the stuff covered beaches at Little Cayman’s ­resorts, most dive sites lie on the ­opposite side of this small ­island. In general, dive shops simply adopted the ­strategy of frequenting dive sites ­unaffected by sargassum, says marine biologist and dive ­instructor Andre Miller of ­Barbados Blue Watersports.

The seaweed did get swept into large bays on the southeast coast of Barbados and those on Antigua where — as the seaweed decomposed — it turned the water brown.

One Barbados dive instructor blamed it for a temporary drop in viz from 100-plus feet to about 15 feet in Carlisle Bay. The thick mats also can make it difficult to launch boats and foul the engines of those who encounter it.

Sargassum blooms also affect ­marine life that attract divers in the first place. Miller reports that recent blooms have killed sea turtles, dolphins and fish. Floating mats can block needed sunlight from sea-grass beds and coral reefs, and heavy beach accumulations appear to discourage sea turtles from ­nesting. Sea turtle hatchlings can die due to ­hyperthermia, exhaustion, drowning and ­predation as they navigate thick seaweed on the beach and in the water.

Divers making plans for next spring and summer can check the Sargassum Watch System, maintained by the ­University of South Florida’s Optical ­Oceanography Laboratory. It shows satellite images of Caribbean locations affected by past blooms, making them candidates to ­experience future blooms.

Travelers also can view and share ­sargassum images on Texas A&M ­University at Galveston’s Sargassum ­Early Advisory System Facebook page, and ask experts questions about conditions in the Caribbean and Gulf of Mexico. The system uses NASA satellite imagery of blooms and scientific tracking of ocean currents to make short-term predictions of where sargassum might land.

Ironically, sargassum mats make for ­interesting dive sites. Species commonly found beneath them include many types of jacks, flying fish, tripletail, cobia, dolphinfish, vermilion snapper, swordfish, pipefish, scrawled filefish, gray triggerfish, barracuda, tuna and billfishes, as well as juvenile sea turtles and a variety of crustaceans.

Avoid them or embrace them, though, sargassum blooms may be the new normal, Miller says. And we have only ­ourselves to blame.

Source : Scuba Diving

The Great Seaweed Invasion

In the Caribbean, sargassum deposits have grown to unprecedented sizes, obscuring the sand and turning nearshore waters into seething sargassum soup.

beach in saint lucia laden with mysterious sargassum seaweed

Juliet Lamb – October 24, 2018

They’d seen seaweed before, but nothing like this.

From the shores of Nigeria, to remote villages in the West Indies, to the tourist beaches of Quintana Roo and the glossy high rises of Florida, the seaweed kept coming. Each incoming tide added to the precarious cliffs of algae until they were taller than grown men. The piles reeked of decay, disgorging dead fish and smothered turtles. Tourists stayed away. Out in the harbors, boats floated, useless, on dense tides of solid brown weeds. In the past, villagers might have harvested the beached seaweed to dry or bury as fertilizer, but the sheer volume of it on the shoreline—trapped and rotting—made any practical use impossible. They could only watch as the piles grew higher. The year was 2011, and something was wrong.

An attempt to find a solution to this ecological mystery has been underway for the better part of the past decade, a search that has stretched from the Sahara Desert to the Amazon rainforest, from the Bermuda triangle to outer space. More importantly, it would serve as a reminder of how little we know about what’s happening in the oceans that occupy the majority of our planet—and of how rapidly our own actions might be changing them beyond recognition.

If you’ve ever been out on a boat, you’ve probably seen pelagic sargassum. It floats on the ocean’s surface in narrow, shifting bands, driven by the competing forces of wind and water. From above, sun-baked sargassum rafts look like barren, discolored ribbons of oceanic detritus. From below, they are as complex and teeming with life as inverted coral reefs. Green-brown fronds trail spherical air sacs; coin-sized sea turtles and fish whose patterns imitate sun on water dart in and out of the algal forest. In tropical waters, where nutrients are scarce and marine life scattered, a sargassum raft is an oasis of life and productivity. Floating sargassum acts as a mobile buffet, supporting entire food chains, from primary producers to top predators.

Looking closer at a sargassum mat, you might notice two different plants: needle-leaved Sargassum natans, which forms the majority of pelagic sargassum biomass, and broad-leaved, bushy Sargassum fluitans, which makes up the rest. Although the sargassum family includes hundreds of other members, most are sedentary plants tethered to the seafloor. These two species, found only in the Atlantic, are the only fully pelagic (open sea) members of their genus.

For a long time, the origins of floating sargassum remained a mystery. Were the plants that formed them completely free-living? Or had they once been rooted before becoming detached by waves or storms? The confusion stemmed from the fact that nobody had ever found reproductive organs on either of the two floating sargassum species. Eventually, observers concluded that pelagic sargassum really do reproduce at sea. When enough nutrients are available, the plants undergo rapid growth and, in a process called vegetative fragmentation, break into smaller pieces. These independent offshoots eventually form mature plants, and the cycle begins again.

It’s no coincidence that the location of the Sargasso Sea matches that of the Bermuda Triangle.

Adding further to the mystery, until fairly recently, observers could only guess at where sargassum mats came from. In a 1914 speech to the American Philosophical Society, naturalist William Farlow summed up a few of the more colorful speculations: “Von Marten’s theory that the gulf-weed originated in the Indian Ocean and was carried by currents round the Cape of Good Hope to the Sargasso Sea has nothing to support it, nor can the theory of Ed. Forbes that the floating gulf-weed is the survival of Sargassum growing on the submerged Atlantis be seriously considered.”

Thanks to remote sensing, we now have a more accurate idea of where sargassum originates (unfortunately, not Atlantis). Although small blooms of sargassum occur throughout the tropics, most sargassum production is concentrated in a few hotspots, particularly the northwestern Gulf of Mexico, where sargassum plants grow and fragment each spring during periods of high nutrient availability. Their offshoots catch a ride on powerful loop currents to the Gulf Stream, which eventually brings them to the Sargasso Sea, east of the Bahamas. The Sargasso Sea, considered the world’s only sea with no terrestrial boundaries, is enormous, borderless, and bright blue. It is ringed by competing oceanic currents that convey passive oceanic drifters—hatchling sea turtles, larvae from fish and eels, trash—into a sort of watery holding cell. Those that can leave under their own steam eventually do, once they grow large enough; those that can’t either spin off on fortuitous ocean currents or float around in a permanent raft of flotsam until they decompose. While the Sargasso Sea likely doesn’t produce much new sargassum—nutrients there are too scarce to support large-scale growth and fragmentation—it’s very good at collecting it.

It’s no coincidence that the location of the Sargasso Sea matches that of the Bermuda Triangle, a mysterious stretch of ocean where things are known to vanish, never to be seen again. Sailors from Columbus onward reported sargassum mats thick enough to impede navigation—or even disable ships. Writing for the royal geographical Society in 1925, Captain C.C. Dixon asked:

Who could know whether this weed got thicker and thicker till there was no turning back? Its changing tints and shadows as daylight faded and at the approach of dawn needed but little help from the imagination to be wrought into fearsome monsters that inhabited its depth and whose very appearance would steal away one’s sanity.

Mariners imaginatively conjured a gyre of ghost ships from every era of navigation, tangled in sargassum and doomed to turn in endless circles until they disintegrated or sank. In modern times, the Sargasso Sea is described, perhaps more realistically, as containing a large amount of seagrass diluted over a vast region, only occasionally forming the epic mats described in early narratives (never thick enough to actually trap a ship).

Until recently, sargassum patterns were relatively easy to predict. From their Sargasso Sea stronghold, modest quantities might shoot off into the Gulf Stream, catch lateral currents, or ride storm surges that convey them to tropical beaches on either side of the Atlantic. However, in 2011, that pattern abruptly changed. In the Caribbean, sargassum deposits grew to several meters thick, obscuring the sand and turning nearshore waters into seething sargassum soup. Along the shores of West Africa, similarly unprecedented levels of sargassum choked the ocean beaches.

Although news coverage of the sargassum bloom tended to focus on lost revenue from tourism, excess sargassum is more than just an aesthetic concern. At sea, sargassum is buoyant and full of life; landlocked, it’s heavy and putrid. While small amounts of beached sargassum can create refuges for invertebrates and provide foraging areas for shorebirds, large quantities quickly become unusable and dangerous. Deep deposits can bury hatchling sea turtles, who emerge from nests laid months earlier to find themselves beneath meters-deep vegetation. Decaying sargassum also releases hydrogen sulfide, a noxious gas that can be mildly toxic to humans.

The source of the sudden sargassum influx proved difficult to pinpoint. Initial theories ranged from the effects of dispersants used to sink oil during the 2010 Deepwater Horizon oil spill in the Mississippi Delta to unusually severe African dust storms that airlifted nutrients to the Atlantic.

Oddly enough, the eventual solution came from outer space. Images of ocean reflectivity from satellites proved able to distinguish floating sargassum mats, which appear as dark spots, from the surrounding water. By examining satellite imagery from that year, scientists noticed a new hotspot for sargassum production: an area off the northern coast of Brazil, at the outflow of the Amazon River, where in the past hardly any sargassum growth had been detected. The amount of sargassum produced in this new area dwarfed any previous estimates from outside the Sargasso Sea. Although sargassum production fluctuates between years, the assumption was always that the lack of nutrients in the offshore waters of the Sargasso Sea imposed a ceiling on the amount of sargassum that could grow at any given time. This new hotspot, disturbingly close to shore, next to a highly productive river mouth, isn’t limited by a lack of nutrients or blocked in by an oceanic gyre. You’d be hard-pressed to find a more ideal producer and exporter of sargassum.

By all predictive measures, sargassum blooms are here to stay.

Since 2011, the increase in sargassum production and distribution has persisted, with abnormal sargassum blooms in at least five of the last eight years. 2015 was a new record year, and 2018 is already on track to surpass it; peak deposits are expected in late summer and through the fall. The blooms reflect a combination of environmental conditions, but are particularly severe in years with above-average sea-surface temperatures and high levels of nutrients in the Amazon river. Nutrient levels in the Amazon basin are increasing, driven mainly by nitrogen and phosphorous from fertilizers used in areas of rainforest recently converted to farmland. Downstream, their fertilizing effects are equally powerful for marine vegetation, sargassum included.

Although it’s difficult to know exactly how sargassum blooms first took hold in the region, they aren’t likely to go away any time soon. The continuing conversion of Brazilian rainforests to agriculture fuels a constant demand for fertilizer, of which Brazil is one of the highest consuming nations on earth. Between steadily rising sea-surface temperatures and ever-increasing nutrient loads, it seems almost certain that high sargassum productivity will persist or increase in the Amazon outflow, and could spread to similar regions of nearshore tropical ocean. By all predictive measures, sargassum blooms are here to stay.

So, what’s the solution? Mass harvesting of sargassum at sea is impractical, with negative consequences for the many marine species that use sargassum mats as refuges, nurseries, and foraging areas. Once the plants wash ashore, removing the massive piles becomes even more challenging—and potentially damaging to sensitive beach habitat. Until now, measures to address the sargassum influx have been short-term and piecemeal. Mexico has hired thousands of people to manually rake the seaweed, deployed floating barriers to keep it from reaching beaches, and used hydraulic pumps to collect it on the open ocean. However, there are signs of developing interest in the potential uses of sargassum: in fertilizers, biofuels, sunscreens, or food products. Learning to live with sargassum will depend on finding a balance, for tourists and fishermen as well as for pipefish and sea turtles.

Meanwhile, much about sargassum remains a mystery. It may not grow on the lost city of Altantis, or harbor ancient galleons doomed to spend eternity floating in circles. Although American and European eels are known to breed in the Sargasso Sea, nobody has ever seen them spawn in the wild. Perhaps it’s time for a new sargassum mythology: not one of monsters or shipwrecks, but of the profound mystery and vulnerability of the ocean itself.

Source : JSTORE Daily

Algues rouges et Sargasses – Interview Radio Canada 10-2018

Algues rouges et sargasses, une vengeance de la nature!

Radio Canada

Emission Medium Large animée par Catherine Perrin.
Interview de Denis Jimenez « The ocean Cleaner  » et Dolores Planas Biologiste.

C’est la pollution, le déversement d’engrais et la déforestation qui sont à l’origine des algues toxiques qui causent la mort de milliers de poissons, de tortues, de dauphins et de plantes aquatiques depuis la fin de l’été au large de la Floride. Plus au sud, le Mexique et les Caraïbes sont également aux prises avec la multiplication des sargasses. Dolores Planas, professeure émérite en sciences biologiques, et Denis Jimenez, constructeur de bateaux, expliquent à Catherine Perrin comment les ouragans stimulent la progression de ces algues, puis donnent un aperçu des solutions possibles.

Selon Dolores Planas, l’actuelle vague d’algues rouges a été déclenchée par les ouragans de la saison 2017. « Si vous regardez aujourd’hui l’évolution des nouveaux ouragans, vous verrez qu’il y a des vents très forts qui remuent l’eau, indique-t-elle. Alors, les nutriments qui se sont accumulés au fond des zones côtières remontent à la surface. Les petites algues n’attendent que de la nourriture pour se reproduire et [proliférer], comme c’est arrivé à d’autres reprises. Normalement, ces phénomènes d’algues rouges dans les zones des côtes de l’Amérique du Nord et du Mexique durent trois, quatre mois. […] Jamais elles n’ont explosé comme elles le font présentement. »

Étouffantes sargasses
Denis Jimenez, pour sa part, a mis au point une barrière flottante pour récupérer les sargasses au large du Mexique et de la Floride. Il croit qu’elles peuvent être utilisées pour fabriquer des engrais, du bioplastique ou du biogaz. « Ces derniers temps, surtout cette année, nous sommes très [touchés] par ces algues qui viennent s’échouer sur les plages et tuer tout ce qui est en dessous, dit-il. Elles consomment tout l’oxygène. Malheureusement, tout ce qui est faune et flore en dessous meurt, y compris les coraux. En se décomposant, elles provoquent la mort de tout un écosystème. Elles ont tendance à se décomposer sur place et à transformer l’eau qui était transparente et limpide en mer café. »

Source : Medium Large – Radio Canada