In June and early July 2013, beaches and bays along the east coast of China's Shandong Province were coated in thick mats of green algae, or seaweed, that washed in from the Yellow Sea.
According to reports, the algae Ulva prolifera covered 11,500 square miles of coastal water and piled up as much as 16 inches deep on some beaches around Qingdao. Reports from international and Chinese news sources suggested that the algae didn't deter many beachgoers in the province; it is harmless to humans.
Massive phytoplankton blooms have become more frequent along the Shandong coast (sixth year in a row) and many other coasts around the world as excessive nitrogen from fertilizers and septic and sewage systems provides nutrients for algae both harmless and toxic. Coastal scientists note that such blooms are a mixed blessing, promoting growth of some species, crowding out others, and reducing oxygen and sunlight needed by other marine life.
Image courtesy of NASA.