Electron microscope image of Emiliania huxleyi, the most abundant coccolithophores in the ocean. Phytoplankton, such as the one pictured here, live in the sunlit portion of the world’s oceans and are responsible for nearly half of primary production on Earth. Primary production is organic matter mostly produced via photosynthesis either in the marine or terrestrial biosphere. Almost all life on Earth is directly or indirectly reliant on primary production.