In the surface waters, dissolved atmospheric carbon dioxide (CO2(aq)) reacts with water molecules to form carbonic acid (H2CO3), a weak diprotic acid. Diprotic acids consist of two ionizable hydrogen atoms in each molecule. In an aqueous solution, partial dissociation of carbonic acid releases a hydrogen proton (H+) and a bicarbonate ion (HCO3-), and subsequently, the bicarbonate ion dissociates into an additional hydrogen proton and a carbonate ion (CO32-). The dissolving and dissociating of these inorganic carbon species generate an increase in the concentration of hydrogen ions and inversely lowers ambient surface ocean pH. The carbonate buffering system governs the acidity of seawater by maintaining dissolved inorganic carbon species in chemical equilibrium.