Seen from a geological perspective, phases of ocean acidification are not new. During the Paleocene-Eocene Temperature Maximum (PETM) 55 million years ago, global temperatures rose by about 6 degrees Celsius in less than 10,000 years. The carbon dioxide concentrations in the atmosphere increased as well as the ocean’s acidity. Many calcifying benthic organisms died – but some species living at the surface survived.
The crucial difference: The changes that we are experiencing today are taking place at least ten times faster than during the PETM. Even species that reproduce fast and are thus able to adapt to changing conditions through evolution seem to find it harder to keep pace with the current rate of changes.