Introduction to the Special Issue on green tides in the Yellow Sea

The spectacular massive green tide of Ulva prolifera in the southern Yellow Sea, which has become a recurrent phenomenon in this region over the last 8 years, attracted much attention of scientists and local government. Several mechanisms have been proposed to explain the early development of green tides in the Yellow Sea, but many questions still remain to be answered. Two years after the first occurrence of massive green tide in the Yellow Sea, a project in the National Basic Research Priority Program (973 project) "Succession of Harmful Algal Blooms in the Coastal Waters of China and the Impacts on Marine Ecosystems (CEOHAB II)" supported by the Ministry of Science and Technology of China started to perform comprehensive investigations and studies on the early development of green tides in the western part of the southern Yellow Sea. In this introduction, we reviewed the progress in understanding aspects of green tide dynamics made by researchers working in the region, and highlighted remaining questions.