World Oceans Day 2022: What is Ocean Acidification?

Ocean acidification threatens marine ecosystems, which also affects populations who rely on the ocean as a source of income and diet. Over three billion people depend on marine and coastal biodiversity for their livelihoods.

For marine ecosystems, ocean acidification presents a two-fold challenge: higher acidity and lower availability of carbonate ions (CO₃^2-). Calcifying organisms – such as oysters, crabs, sea urchins, lobsters and coral – need CO₃^2- to build and maintain their shells and skeletons. Furthermore, studies suggest marine shells and skeletons may dissolve more easily as pH decreases. Scientists are studying the extent to which calcifying organisms are affected by acidification and how some organisms may be more sensitive than others.

Energy spent by marine organisms overcoming more acidic conditions may reduce the energy available for physiological processes, such as reproduction and growth, threatening the stability of food chains that would affect the ecosystem resilience and economic activities, such as fisheries and tourism.