I didn’t realise that Sargassum had become a problem on the Pacific coasts. Sargassum horneri is a seaweed native to eastern Asia
that has recently become established in the coastal waters of southern California
, and Baja California
Evidently, the Atlantic [Sargassum natans and S. fluitans] variety, and Pacific [Sargassum Horneri] variet are very different species.
Scientists discover the biggest seaweed bloom in the world
The Great Atlantic Sargassum Belt (GASB) is a loose collection of seaweed scattered over a very large area, not a continuous bridge. It’s also not produced by the Sargasso Sea, which lies further north. The belt likely develops from local patches of sargassum that occur naturally in the tropics.
The decomposition of beached sargasso begins 48 hours after washing
up. It then releases hydrogen sulfide (H2S) gas and ammonia. H2S is a broad-spectrum poison that smells of rotten eggs.
Breathing in these toxic gases may cause respiratory, skin and neurocognitive symptoms in people that come in close contact with degrading sargasso. In 2018, in Guadeloupe
, there were 11,000 cases of suspected poisoning reported. Patients complained of heart palpitations, shortness of breath, dizziness, vertigo, headache, and skin rashes.
There is no specific treatment for the symptoms caused by exposure to H2S. Symptoms are usually mild and resolve with time. When necessary, supportive treatment may be provided.
Avoiding exposure is the most important preventive measure. The peak Sargassum season in the Caribbean is January to April. If beaches are covered with brown seaweed, travelers should not walk on the beach—especially if there is a smell of rotten eggs in the air.
Boaters may also have trouble navigating their vessels through the weed floats and should follow forecasts, like the Sargassum Watch System (SaWS), to avoid being captured by grass
in bays and shallow waters.
Satellite-based Sargassum Watch System (SaWS)
“The great Atlantic Sargassum belt”
~ by Mengqiu Wang et al