Ocean acidification: basics

In short: Ocean acidification refers to the falling pH of the world’s oceans caused by absorbing CO2 from the atmosphere. It particularly threatens marine organisms that build calcium shells or skeletons.

In more detail: About a quarter of human-released CO2 is absorbed by the ocean and chemically transformed.

In detail

• Chemical process: CO2 reacts with seawater to form carbonic acid, which lowers pH and binds carbonate ions.
• Affected organisms: Corals, molluscs, and some plankton species increasingly struggle to build their calcium structures.
• Food chain: Since many affected organisms sit at the base of marine food chains, effects can ripple through entire ecosystems.
• Speed: The current rate of acidification is historically exceptionally fast, making adaptation difficult for many species.
• Regional differences: Cold, nutrient-rich waters are often more affected by acidification than warmer regions.
• Economic consequences: Oyster and mussel farms already report measurable yield losses due to changed water chemistry.
• Link to climate change: Ocean acidification and global warming share the same cause and reinforce each other’s ecological consequences (korallenriffe-und-ihre-bedeutung, co2-fussabdruck-im-alltag).