Overgrown enteromorpha — a kind of green algae, also commonly known as sea lettuce — fills a breeding pond in Qingdao city, East China's Shandong province, July 6, 2011. Cleanup efforts are being made to prevent the algae from covering the water surface, which would deprive the sea cucumbers of oxygen. Piles of the algae were found on the beaches of Qingdao city on July 6. As part of the clean-up work, nearly 200 tons of enteromorpha were collected in one day from Qingdao Silver Beach.[Photo/CFP]