Sargassum is a brown seaweed belonging to the Sargassaceae family, which includes a large number of species worldwide. Algae of the Sargassum genus are commonly fixed on coastal seabeds, with the exception of two species that grow on the surface of the ocean, drifting freely with ocean currents in the form of slicks: These are the pelagic Sargassum fluitans and Sargassum natans.
The natural decomposition of Sargassum seaweed, in the absence of oxygen, results in the emission of hydrogen sulfide (H2S). This gas, with its characteristic rotten-egg odour, is the cause of respiratory, ophthalmic and/or cutaneous symptoms.