Ocean Acidification

Ocean acidification — the decrease in ocean pH caused by absorption of atmospheric CO2 — is often called 'the other CO2 problem' (alongside climate change). The ocean absorbs approximately 25-30% of all CO2 emissions, which reacts with seawater to form carbonic acid, releasing hydrogen ions and reducing pH. Since the Industrial Revolution, ocean surface pH has fallen from 8.2 to 8.1 — seemingly small, but pH is logarithmic, representing a 26% increase in acidity. The impacts: organisms that build calcium carbonate shells and skeletons (corals, oysters, mussels, pteropods, some plankton) cannot build and maintain their structures at lower pH — they literally dissolve. At projected pH levels by 2100, coral reefs may be chemically unable to exist. Pteropods (small sea snails, crucial food for salmon, whales, and seabirds) already show dissolving shells in the Southern Ocean. Ocean acidification also affects fish behavior — fish exposed to acidified water show impaired hearing, smell, and predator avoidance. The economic cost: $10 billion annually to shellfish industries alone (already occurring).