Beaches in Qingdao, China have been covered with 790 square meters of algae. The edible plant is called Enteromorpha or Sea Lettuce, and is known to emit toxic fumes when it decomposes.

Tens of thousands of local volunteers came out for the clean up effort, fearing that the rotting green mush would poison the air. Rotting sea lettuce has been blamed for a few deaths in England in recent years.

The plant covered all local beaches, making it impossible for visiting tourists to swim.