Dead seaweed chokes beaches across the Caribbean every year. (Credit: Playa del Carmen/Shutterstock)

(Inside Science) — In the summer of 2018, thousands of tons of a prolific seaweed called sargassum invaded the pristine beaches of the Caribbean. In Mexico, the turquoise waters and clear, smooth sand of the touristy Mayan Riviera turned into a brown mess. The sight of sargassum — a type of brown algae — and its smell scared tourists away, and local ecosystems started to suffer greatly.