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 is 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.

After a relatively calm 2020, experts are noting that sargassum levels have increased and are predicting that the impact on the Caribbean islands will be somewhat greater this year.  The Sargassum Sub-Regional Outlook Bulletin reports a 150% increase in the sargassum visible in the Atlantic compared to 2020. Latest reports show approximately four million tons of sargassum currently in the sea. However, it notes that it is still well below the levels reported in 2018, the worst year on record.

The islands of the Eastern Caribbean can expect moderate to severe sargassum influxes throughout 2021, with the northernmost of these islands being the hardest hit.  The reasons for this are many and varied, with climate change playing a predominant role.

Sargassum can be more than just an inconvenience. In addition to spoiling the beauty of otherwise pristine beaches and discouraging swimming, 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 quickly 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.

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. The Global Tourism and Crisis Management Centre, a Jamaica-based research and advocacy organization, estimates that governments alone spent about $120 millionUSD on cleaning beaches in the Caribbean in 2019. Plus the efforts of some beachfront resorts throughout the region have been impressive.  But governments and the tourist sector 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’ in specific areas. One such resource is

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, Toronto General Hospital, Sargassum Sub-Regional Outlook Bulletin, The Global Tourism and Crisis Management Center,

“File:Sargassum Varech (3).jpg”by Filo gèn’ is licensed under CC BY-SA 4.0

IC 2021