The ocean's loneliest microbe has a secret second life — and it may carry half a billion tons of carbon down with it

Prochlorococcus is the most abundant photosynthetic microbe in the ocean — a tiny organism that makes oxygen and feeds marine food webs, long pictured as a solitary drifter. Research published this week shows it also sticks to sinking particles: at a research site off Hawaii, about 12% of the microbes riding particles down were Prochlorococcus. If that holds across the oceans, these microbes could carry roughly half a billion metric tons of carbon a year into deep water, where it can stay locked away for centuries — a hidden, living conveyor in Earth's climate system that scientists had simply missed.

SDG 14 · Life below water