Ocean Acidification Explained
Quick Fact
The ocean has become 26% more acidic since the Industrial Revolution — a rate of change faster than anything seen in the past 300 million years.
About This Species
The ocean absorbs approximately 30% of the carbon dioxide released by human activities. As CO₂ dissolves in seawater it forms carbonic acid, lowering the ocean's pH — a process called ocean acidification. Since the Industrial Revolution, ocean pH has dropped by 0.1 units, representing a 26% increase in acidity. This threatens organisms that build shells and skeletons from calcium carbonate — including corals, oysters, mussels, sea urchins, and many species of plankton that underpin the entire marine food web.
Why It Matters
Ocean acidification threatens the foundation of marine food webs. If pteropod plankton — a key food source for fish, whales, and seabirds — cannot form their shells, the consequences cascade through the entire ocean ecosystem.
Transcript
The ocean is becoming more acidic. And it's happening faster than at any point in the last 300 million years. Here's the chemistry. The ocean absorbs around 30% of the carbon dioxide we release into the atmosphere. When CO₂ dissolves in seawater, it forms carbonic acid. That acid releases hydrogen ions, which lower the pH of the water. Since the Industrial Revolution, ocean pH has dropped from 8.2 to 8.1 — a change that sounds small but represents a 26% increase in acidity. For animals that build shells and skeletons from calcium carbonate — corals, oysters, mussels, sea urchins, and many species of plankton — this is catastrophic. More acidic water dissolves calcium carbonate. Shells become thinner, weaker, and harder to form. In some cases, they dissolve entirely. Pteropods — tiny free-swimming sea snails sometimes called sea butterflies — are already showing shell dissolution in parts of the Southern Ocean. They're a critical food source for salmon, herring, and whales. If pteropod populations collapse, the effects cascade through the entire food web. Coral reefs are particularly vulnerable. Ocean acidification weakens coral skeletons and slows reef growth, making reefs less able to recover from bleaching events. The solution is the same as for climate change — reduce carbon dioxide emissions. The ocean can't absorb our carbon indefinitely without consequences. We are conducting an uncontrolled experiment on the chemistry of the sea. And the results are already coming in.