The chemistry
CO₂ + H₂O → H₂CO₃ → H⁺ + HCO₃⁻. More CO₂ means more hydrogen ions, lower pH, and less carbonate available for shell-building organisms.
Since 1750, surface ocean pH has dropped from ~8.2 to ~8.1. Under RCP8.5, it could hit 7.7 by 2100 — a 150% increase in acidity vs pre-industrial.
Who's most at risk
Coral reefs, oysters, mussels, pteropods, and larval fish. Pacific oyster hatcheries have already collapsed twice from acidified upwelling.
Frequently asked questions
- Can ocean acidification be reversed?
- On human timescales, no — chemistry takes tens of thousands of years to rebalance. Emissions cuts today prevent worse damage tomorrow.
oceans acidification coral reefs climate