Marine Cyanobacteria

Marine cyanobacteria are the photosynthetic bacteria of the sea. Cyanobacteria are aquatic, usually unicellular and often grow in colonies large enough to see, and they have the distinction of being the oldest known fossils, more than 3.5 billion years old. They take their name from the bluish pigment phycocyanin, although some are red or pink from phycoerythrin, and the Red Sea gets its name from occasional blooms of a reddish species of Oscillatoria. Cyanobacteria are among the few organisms able to convert inert atmospheric nitrogen into nitrate or ammonia, and the oxygen atmosphere we depend on was generated by numerous cyanobacteria during the Archaean and Proterozoic Eras.