From National Geographic:
Turquoise plumes stain the waters of the Barents Sea (map), north of Scandinavia, in a satellite picture of a plankton bloom taken September 10. The bloom first appeared in summer months and had persisted for weeks when it was photographed by NASA’s Aqua satellite.
Feeding off plentiful nutrients, phytoplankton can thrive in the cool waters of the Arctic and North Atlantic Oceans. The milky blue hues of this bloom might come from coccolithophores—plankton with white calcite shells that appear blue in the ocean.