In Depth: Why ‘Green Tides’ Keep Rolling Into East China

At noon on July 9, the temperature on Dujiadao Island in East China’s Shandong province was around 34 degrees Celsius (93 F). As the tide came in, vast sheets of algae called Ulva prolifera rolled ashore like an enormous quilt. Layer upon layer of algae piled up on the shore, creating a green blanket as thick as a person’s forearm.