In which chemical form is most of the carbon in the ocean found?

1. Carbon dioxide from the atmosphere dissolves into sea water. 2. It then combines with water molecules to form carbonic acid. 3. That acid ionizes, giving carbonate and bicarbonate ions. 4. The equilibrium between these forms is not even. 5. More than 90 percent of ocean carbon ends up as bicarbonate ions. 6. Some carbonate ions do combine with calcium to build shells of calcium carbonate. 7. Those shells settle and over geologic time become limestone, the largest carbon reservoir on Earth. 8. Choosing dissolved gas stops at the first step and ignores the reactions that follow. _Source: OpenStax Biology 1e (CC BY 4.0), Chs 44 and 46, section 46.3 Biogeochemical Cycles_