The waters of the Norwegian Sea were awash with color on August 4, 2009, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this photo-like image. The brilliant shades of blue and green that fill the waters near the shore are likely phytoplankton, microscopic plant-like organisms that live in the surface waters of the ocean.

Northern summers bring long, sunlit days, giving the organisms plenty of time to grow and reproduce. Over the winter, when days are short and the water is covered with ice, nutrients build up in the surface waters. When summer returns, phytoplankton have an abundance of light and nutrients. Large blooms frequently develop throughout the Arctic.

Phytoplankton are the base of the marine food chain. Areas in which phytoplankton thrive—in the cold waters of the Arctic or Antarctic and in areas where currents bring nutrients to the surface—tend to support a rich and varied ecosystem. Phytoplankton are also an important part of the carbon cycle. The tiny organisms absorb carbon dioxide from the atmosphere as they grow. When they die, plankton sink to the bottom of the ocean, where the carbon is stored.