Ocean Acidification

Ocean acidification, the worldwide reduction in the pH of seawater as a consequence of the absorption of large amounts of carbon dioxide by the oceans. Ocean acidification is largely the result of loading Earth’s atmosphere with large quantities of CO₂, produced by vehicles and industrial and agricultural processes. Marine scientists are concerned that the process of ocean acidification constitutes a threat to sea life and to the cultures that depend on the ocean for their food and livelihood. Increases in ocean acidity reduce the concentration of carbonate ions and the availability of aragonite in seawater. Marine scientists expect that coral, shellfish, and other marine calcifiers will be less able to obtain the raw materials that they use to build and maintain their skeletons and shells. These scientists also note that rising ocean acidity presents a number of other physiological problems to different groups of marine organisms and those problems could threaten the stability of marine food chains. The acidity of any solution is determined by the relative concentration of hydrogen ions. A larger concentration of H+ ions in a solution corresponds to higher acidity, which is measured as a lower pH. When CO₂ dissolves in seawater, it creates carbonic acid and liberates H+, which subsequently reacts with carbonate ions and aragonite to form bicarbonate. At present seawater is extremely rich in dissolved carbonate minerals. However, as ocean acidity increases carbonate ion concentrations fall.