Absorbed CO2 forms carbonic acid, lowering ocean pH and harming shell-forming organisms.
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Carbon dioxide from the atmosphere dissolves in seawater, forming carbonic acid and lowering the pH. Since pre-industrial times the average surface ocean pH has fallen by about 0.1 units, which corresponds to roughly a 25 to 30 percent increase in hydrogen ion concentration. The lower pH also reduces the carbonate ions that corals, molluscs and other organisms need to build calcium carbonate shells and skeletons. This threatens reefs and shellfish, and it is an ongoing consequence of rising atmospheric carbon dioxide. Monitoring it relies on measurements of seawater carbonate chemistry.
Key ideas: CO2 dissolves in seawater: CO2 + H2O gives H2CO3 gives H+ + HCO3-, and H+ + CO3 2- gives HCO3-. Ocean pH has fallen from about 8.2 to 8.1 since pre-industrial times, a roughly 30 percent rise in [H+]. Lower carbonate ion reduces the saturation state of aragonite and calcite, making shell formation harder: CaCO3 dissolves when carbonate is too low.
Common mistakes and connections: Mistake: calling the ocean acidic; it is still basic (pH above 7), the change is toward acidity. The log scale hides the size of the shift. Buffering by carbonate slows but does not stop it, and the effect is greatest in cold water. Connects to Henry's law, solubility equilibria and the carbonate buffer.
Absorbed CO2 forms carbonic acid, lowering ocean pH by about 0.1 since 1850, a 30 percent rise in H+ that harms shell-forming organisms. The interactive lesson shows this as a live animation or chart.
Coral reefs weaken and can bleach as the carbonate supply needed for their skeletons decreases.
Absorbed CO2 forms carbonic acid, lowering ocean pH and harming shell-forming organisms.
Ocean Acidification is a intermediate topic in Acids, Bases & Electrochemistry. It builds on the vocabulary of beginner topics in this area.
Study these earlier topics in Acids, Bases & Electrochemistry first: pH Meter, Hydrogen Production by Electrolysis, Acid Rain.
The next topics in Acids, Bases & Electrochemistry are Antacids and Leveling Effect.
Yes. The interactive lesson includes a self-check question on Ocean Acidification, and the Acids, Bases & Electrochemistry quiz draws on every topic in this area.
Ocean Acidification is topic 96 of 105 in Acids, Bases & Electrochemistry.