Before you even ask, this is indeed a real image of Earth! In August 2015 a massive bloom of cyanobacteria - more than 100 square kilometers - was seen in the Baltic Sea. Cyanobacteria are a type of marine bacteria that capture and store solar energy through photosynthesis. While some are toxic to humans and animals, large blooms can cause an oxygen-depleted dead zone where other organisms cannot survive. Scientists believe that blooms are more likely to form in the presence agricultural and industrial run-off or from cruise ships that provide excessive nutrients for the bacteria through the dumping of sewage.