About half of atmospheric carbon dioxide is fixed by ocean’s phytoplankton through a process called photosynthesis. A large portion of biologically fixed carbon is formed by picocyanobacteria at the sea surface and then transported to the deep ocean. But what remains a mystery is how colored dissolved organic matter which originates from plant detritus (either on land or at sea) makes it into the deep ocean. A team of scientists has potentially found a viable marine source of this colored material.