Brilliant green swirls of phytoplankton colored the water of the Barents Sea north of Norway in late July 2004. An extra-tropical low pressure system swirls over the Baltic States in this image, captured on July 30, 2004. Along the top of the image, a splash of bright blue colors the waters of the Barents Sea, north of Norway. The color is caused by a large phytoplankton bloom, which are common in the region during the summer. It’s not clear what kind of plant is causing the bloom, but the brightness of the color suggests coccolithophores, a type of microscopic plant coated in calcium carbonate (chalk). Their white, chalky exteriors reflect light through the blue ocean water, making bright swirls of turquoise in satellite imagery. Europe and Scandinavia are visible.