The 5,000-mile-wide bloom is a belt of sargassum, a floating brown algae that usually floats in the Atlantic. The problems start when it comes on land and starts to rot. As it decays, sargassum lets off hydrogen sulfide and smells like rotten eggs, explains the Florida Department of Health. It can irritate people’s eyes, nose and throat, and trigger breathing issues for people with asthma.
Image: USF/NOAA
[ed. Didn't know it was this big.]