Travel Sargassum seaweed on Florida beaches contains arsenic and other health hazards July 5, 2019 Tyler Treadway, Treasure Coast Newspapers Comments Off on Sargassum seaweed on Florida beaches contains arsenic and other health hazards Sargassum, the seaweed with small air-filled "berries" that floats in masses on the ocean, emits hydrogen sulfide after it washes up and rots in the sun.