Why does ocean acidification threaten organisms that build shells or skeletons from calcium carbonate?

Ocean acidification threatens marine organisms that build shells or skeletons from calcium carbonate because it fundamentally alters the chemistry of seawater, making it more difficult for these "calcifiers" to survive and grow.12

When carbon dioxide from the atmosphere is absorbed by the oceans, it reacts with water to form carbonic acid, which increases the concentration of hydrogen ions and lowers the seawater pH. This chemical process consumes carbonate ions, which are essential raw materials that organisms like coral, shellfish, and various plankton species use to build and maintain their protective structures.12

As carbonate ion concentrations fall, these organisms face several critical challenges:
* Reduced Growth: Calcifiers have less material available to build their skeletons and shells, often resulting in smaller, weaker structures that leave them more vulnerable to predators.12
* Dissolution: In high-acid environments, existing shells can begin to dissolve, as observed in some pteropods.12
* Ecological Disruption: The decline of these organisms threatens the stability of marine food chains and the health of coral reefs, which serve as vital habitats for diverse marine life.12