Ocean acidification threatens marine life

Increasing acidification of the oceans from carbon dioxide emissions could cause mass extinction of marine life, reports Ken Caldeira of the Carnegie Institution’s Department of Global Ecology

When carbonic acid input is modest, sediments from the ocean floor can buffer the increases in acidity. But at the current rate of input--nearly 50 times the natural background from volcanoes and other sources--this buffering mechanism is overwhelmed. Previous estimates suggest that in less than 100 years, the pH of the oceans could drop by as much as half a unit from its natural value of 8.2 to about 7.7. (On the pH scale, lower numbers are more acidic and higher numbers are more basic.)

This drop in ocean pH would be especially damaging to marine animals such as corals that use calcium carbonate to make their shells. Under normal conditions the ocean is supersaturated with this mineral, making it easy for such creatures to grow. However, a more acidic ocean would more easily dissolve calcium carbonate, putting these species at particular risk.