In the quiet seaside village of Capesterre on Marie-Galante island in Guadeloupe on April 18, 2023, the air-quality monitoring institute Gwad’Air issued a “red alert” to warn people away from coastal areas.
The culprit was sargassum. After washing ashore for days, the floating seaweed was emitting a dangerous level of hydrogen sulphide gas as it rotted on the beach.
The problem was not new for residents of Marie-Galante, a sleepy agricultural island of about 11,000 inhabitants that is part of Guadeloupe’s biosphere reserve.
Since the first mass strandings more than ten years ago, rotting sargassum has frequently plagued residents and tourists and forced several businesses and restaurants to close their doors for months at a time.
Among the struggling proprietors are sisters Marie-Louise and Lyselène Bade, who recently shuttered their small hotel Le Soleil Levant.
Marie-Louise Bade is the owner of the small hotel Le Soleil Levant, which had to close due to the sargassum invasion in Guadeloupe. (Photo: COURTESY OF MARIE-LOUISE BADE)
Though they still operate a bakery and grocery store they inherited from their mother, Marie-Louise Bade said a Gwad’Air technician recently asked her a worrying question: “How do you manage to stay here?”
She often wonders the same thing.
“You know, I love wearing costume jewellery, but now I can’t keep it on my skin for more than a quarter of an hour. They oxidise and make my skin itch. When you see what it does to electrical equipment and metal, you wonder what it does inside your body, to your lungs,” she said.
According to Marie-Louise Bade, since sargassum has increased in Guadeloupe, metal furniture and other household items have begun to corrode more quickly. (Photo: OLIVIA LOSBAR RCI GUADELOUPE)
Thanks to recent research carried out in the French Caribbean — much of which has struggled with similar problems as Marie-Galante — scientists can now better answer that question.
They paint a bleak picture. Their studies suggest that the hydrogen sulphide and ammonia gasses released by rotting sargassum can endanger pregnant women, exacerbate respiratory issues like asthma, and cause headaches and memory loss, among other serious health problems.
But this knowledge has not been enough to protect the Bades and many other Guadeloupe residents. Even as the French Caribbean has emerged as a regional leader in the fight against sargassum, researchers such as Martinique-based doctor Dr. Dabor Resiere have said response efforts there have fallen far short.
As a result, many residents regularly face dangerous health risks — and the French government has turned to the world stage to call for an international response to address sargassum as a global problem.
Record 2018 influx
By the time 2018 brought a record sargassum influx to Caribbean shorelines, the health effects of the rotting seaweed had become much better known. In December of that year, a group of sargassum researchers in Martinique issued a stark warning.
In a letter published in The Lancet medical journal, they noted that doctors in Martinique and Guadeloupe — French islands with a combined population of nearly 800,000 — had recently recorded more than 11,000 cases of acute sargassum toxicity during an eight-month period. Among them were three cases admitted to intensive care.
“To mitigate this emerging airborne poisoning outbreak, the French government has already promised €10 million [US $10,835,600] to supply equipment that can be used to remove the seaweed within 48 hours, to monitor hydrogen sulfide concentrations on the affected shores, to train doctors, and to assign experts in toxicology in affected areas,” wrote Dr. Resiere and 10 other researchers based in Martinique and France.
“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.”
Regional leader
The French government — which for decades has struggled with algae washing ashore on its European coasts — has launched two national sargassum plans funded with about $26 million for 2018-2022 and about $40 million for 2022-2026. Millions more were spent by local authorities in sargassum collection operations and investment in dedicated equipment.
As a result, the French islands of Guadeloupe, Martinique, St. Martin and St. Barthelemy have launched some of the most extensive response efforts in the Caribbean in recent years.
Besides the ongoing research, these efforts have included air-quality-monitoring programmes, clean-up initiatives, and one of the rare national response strategies that has been officially adopted by the government.
In 2019, Guadeloupe also hosted the first International Sargassum Conference, where the Guadeloupe Region — in partnership with the French government, the French National Research Agency and two Brazilian agencies — launched a call for projects with financial support from the European Union and other sources.
This effort ultimately funded 12 projects — the results of which were presented on Feb. 28, 2024 — as part of the National Sargassum Prevention and Control Plan. Besides probing the algae cycle and the environmental effects of sargassum, these projects have also investigated health impacts.
One of the outcomes, the SargaCare project, led to a July 2022 study on more than 3,000 pregnant women on Martinique, which reported finding evidence of a higher risk of potentially fatal preeclampsia in expectant mothers exposed to sargassum fumes.
A later SargaCare study suggested that prolonged exposure to the fumes increases the risk of patients developing sleep apnea.
‘The situation remained unchanged’
But despite this work, health researchers have warned that response efforts have not kept pace with the problem in the French Caribbean or the wider region.
More than four years after their 2018 warning in The Lancet, Dr. Resiere and seven colleagues upped the ante in a March 2023 letter published in the Journal of Global Health.
In Guadeloupe and Martinique, they wrote, “the situation remained unchanged. Despite the French government’s plans to tackle the sargassum problem, these toxic algae are continuing to inundate the coasts of Martinique, Guadeloupe, and French Guiana in ever-greater volumes.”
The Covid-19 pandemic, they stated, was partially to blame for the problem because it had sucked up health resources.
But they also noted the absence of a coordinated regional health response and warned that Caribbean governments eager to jumpstart their post-pandemic tourism economies may be inclined to downplay the sargassum problem.
“The public continues to be adversely affected, some have sold their dream houses, which are becoming unlivable, some have abandoned their schools and workplaces for lack of a solution to this scourge,” the researchers wrote.
“It is urgent to come to the aid of these families who, in addition to the health consequences due to the significant emanations of hydrogen sulfide, have to bear the material consequences, being often forced to replace all their household appliances or the metal parts of their houses.”
2023 season
By the time the researchers’ letter was published in March 2023, a new sargassum season was already causing health problems across the French Caribbean.
In late January 2023, a 59-year-old woman was treated by emergency services for acute toxicity after taking part in a sargassum clean-up on Tartane beach in Trinité, Martinique.
On March 2, the Martinique municipality of Le Robert partially closed the Four à Chaux school due to high exposure to gas released by sargassum.
Boats float in sargassum off Batelière Beach in Schoelcher, Martinique, on Sept. 12, 2023. (Photo: JACQUES DIJON
