What is ocean acidification?
Ocean acidification is the long-term decline in seawater pH as the ocean absorbs more atmospheric carbon dioxide.
How it works and what the evidence shows
Core idea Dissolved carbon dioxide changes seawater chemistry, increasing hydrogen ions and changing carbonate availability. This can affect some shell- and skeleton-building organisms. Evidence and research Scientists measure pH, dissolved carbon and alkalinity together. Effects differ by species and region and interact with temperature; a single reading does not represent the whole ocean.
Uses and limitations
Why it matters Corals, shellfish and food webs can be affected. Reducing carbon dioxide emissions addresses the main driver, while local water management can reduce additional pressure. Common misunderstandings Acidification does not necessarily mean the ocean falls below pH 7. Seawater can remain alkaline while becoming less alkaline than before.