You’ve probably seen it. Large clumps of yellowish-brown seaweed clogging and disfiguring beaches and floating offshore, often stretching off seemingly miles into the distance.
It’s sargassum, a type of seaweed with small air-filled ‘berries’ that floats, sometimes in island-like masses, in the sea, and emits an unpleasant odour after it washes up on beaches and rots in the Caribbean sun.
On the positive side, sargassum provides a food source, home, and shelter to an amazing variety of marine species (plant, shrimp, crab, bird, fish, turtle and whale, included). It also plays a vital role in anchoring sand dunes and encouraging plant growth, thus helping reduce wave and wind erosion on the beach.
But it’s a hassle. It defiles the beauty of otherwise pristine beaches and discourages swimming. And it can also be unhealthy.
As sargassum decays, it produces hydrogen sulfide, the main cause of the rotten egg like smell. For most people, the odour coming off rotting sargassum isn’t a serious problem, as it dissipates in the outdoor air, especially with sea breezes. However, long term exposure to hydrogen sulfide fumes can cause multiple health problems.
As Dr. Andrea Boggild, the clinical director of the Tropical Disease Unit at the Toronto General Hospital, notes, breathing in the fumes from decaying sargassum can cause heart palpitations, shortness of breath, dizziness, vertigo, headaches, and skin irritations. People with respiratory problems are particularly at risk.
Direct contact with the strands can also cause minor skin rashes in some individuals.
In recent years, due to weather patterns, the situation has been getting worse. In fact, a recent editorial co-authored by experts at University Hospital of Martinique and Paris-Diderot University in France notes “an alarming number of consultations and hospital admissions related to the effects of both acute and chronic exposures among the local population has been reported in the Caribbean since the beginning of the year 2018”.
An article in the medical journal The Lancet, with which I was once affiliated, reported over 11,000 cases in Guadeloupe and Martinique alone in 2018.
At present, there is no specific treatment for sargassum toxicity, but medical care can help if you experience these symptoms.
Hoteliers and local authorities fight sargassum build up whenever and however they can, coordinating removal and beach protection efforts. Some of these efforts are impressive. The French Government has recently promised €10 million to supply equipment that can be used to remove the seaweed within 48 hours, to monitor hydrogen sulphide concentrations on the affected shores, to train doctors, and to assign experts in toxicology in affected areas under their jurisdiction (Guadeloupe, Martinique, etc.).
But they are at the mercy of forces beyond their control, such as rising water temperatures, changing currents and other factors.
What can you do? Canadian and U.S. health experts generally recommend that people with asthma and other respiratory conditions should be cautious. They should avoid areas with large accumulations of sargassum and leave beaches immediately if they start to feel nausea or have difficulty breathing.
Many beachfront resorts are used to guests checking in advance if they are anticipating problems with sargassum. So, if you or a fellow traveler is particularly sensitive, call and check before booking. Be aware, while they will generally do their best, they can never totally predict weather patterns far in advance. You can also check the internet for ‘sargassum alerts’.
Playing it safe is the best policy. If you think you may be at risk, talk to your doctor before you go.
Resources: Pan American Journal of Public Health, The Lancet, San Pedro Sun, Toronto General Hospital