Atmospheric CO2 Concentration
The Chemical Mechanism
CO₂ + H₂O ↔ H₂CO₃ (Carbonic Acid)
H₂CO₃ ↔ H+ (Acid) + HCO₃⁻ (Bicarb)
Healthy Calcification: Plentiful free carbonate ions allow coral reefs and pteropods to easily construct their calcium carbonate (CaCO3) shells.
AP Exam Tip
A major misconception is that ocean water becomes actually acidic (pH < 7). It does not. It remains basic, but the pH shifts from ~8.2 down toward 7.8, which is a massive logarithmic increase in H+ ions!