General description of carbon dioxide release through the formation of calcium carbonate particles

Textbook description of calcium carbonate shell formation and carbon dioxide release

　When organisms form calcium carbonate shells, they are known to take in Ca²⁺ ions and HCO₃^- ions, which are abundant in seawater, and the following in vivo reactions are possible.

             2HCO₃^- + Ca²⁺ ⇆ CaCO₃ + H₂CO₃ 　　（ ⇆ CaCO₃ + CO₂ + H₂O ） 

　According to this equation, from two HCO₃^- and one Ca²⁺ in seawater, one CaCO₃ and one CO₂ are formed, and with the formation of CaCO₃, CO₂ can be released into the atmosphere. In other words, for every 0.1 mmol of CaCO₃ formed, 0.1 mmol of CO₂ is released into the atmosphere.

　A more accurate estimate of the amount of CO₂ released into the atmosphere is as explained earlier: if 0.1 mmol of CaCO₃ is formed, 0.08 mmol of CO₂ is released into the atmosphere. For a more accurate estimate (development), boric acid and pH changes in seawater should also be considered.