Trillions have died in the Earth's seas. Calcified shields of the dead already make up the white cliffs of Dover . The battle between ball-shaped light-colored single-celled plants -- phytoplankton called coccolithophores -- and even smaller, diamond-shaped viruses dubbed coccolithoviruses -- has raged for tens of millions of years. To help fight this battle , the coccolithophores create their chalky armor by absorbing carbon dioxide from the atmosphere. This battle is so epic that coccolithophores actually remove a significant fraction of Earth's atmospheric carbon dioxide , bolstering the breathability of air for animals including humans . Pictured in this 2012 image from NASA's Aqua satellite , the Black Sea was turned light blue by coccolithophore blooms .
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