English: CO₂ dissolves in seawater to form carbonic acid (H₂CO₃), which can be broken down into hydrogen and carbonate ions. More CO₂ means more hydrogen ions, which decreases carbonate ion levels because some of the additional hydrogen ions combine with carbonate ions (CO₃^2-) to form bicarbonate (HCO₃^-). This means there is less carbonate available for calcifying organisms to build their shells with, resulting in their shells beginning to dissolve. While not all species of marine calcifying organisms will experience negative effects, species like pteropods will experience possibly devastating effects to their populations.