Editing Ocean Acidification (section)

== Carbonate Depletion and the Calcification Crisis ==

The increase in hydrogen ions triggers a secondary chemical reaction that is devastating for marine [[biology]]. The newly freed hydrogen ions are highly reactive, and they naturally bond with free carbonate ions (CO3) floating in the seawater to form even more bicarbonate. 

This is the crux of the biological crisis. Countless marine organisms—from reef-building corals and commercial bivalves (like oysters and mussels) to microscopic foundational species like pteropods (sea butterflies)—rely on an abundance of free carbonate ions to build their calcium carbonate (CaCO3) shells and skeletons. 

As ocean acidification binds up the available carbonate, the water becomes "undersaturated." Building shells becomes energetically exhausting, and in highly corrosive waters, existing calcium carbonate structures literally begin to dissolve while the organism is still alive.