How is atmospheric CO2 responsible for ocean acidification?
When CO2 dissolves in seawater, it forms carbonic acid, which releases hydrogen ions into solution. Acidity is a measure of the hydrogen ion concentration in the water, where an increase in hydrogen leads to an increase in acidity (and a decrease in the pH scale used to quantify acidity). These hydrogen ions then combine with carbonate ions in the water to form bicarbonate. Carbonate ions are the basic building blocks for the shells of many marine organisms. Thus the formation of bicarbonate through this chemical reaction removes carbonate ions from the water, making them less available for use by organisms. The combination of increased acidity and decreased carbonate concentration has implications for many functions of marine organisms, many of which we do not yet fully understand. The details of the reactions look like this: When CO2 dissolves in seawater, carbonic acid is produced via the reaction: This carbonic acid dissociates in the water, releasing hydrogen ions and bicarbonate:
