Mechanistics of Coral Calcification in the Context of Ocean Acidification

The process of calcification in corals leads to the formation of an exoskeleton which is a composite structure made of an organic fraction embedded in a mineral fraction of calcium carbonate. Whereas corals are bathed by external seawater, the composition at the site of calcification is different from seawater and is under biological control. The aim of my talk is to describe the biological toolkit used by corals to promote calcification and to show that calcification is far from being a simple physicochemical reaction. I will discuss ion transport to the site of calcification by cellular ion carriers and enzymes, and also the synthesis of proteins which play a key role in the different steps of crystal formation. These results will then be discussed in the context of ocean acidification which, by decreasing pH and modifying seawater carbon chemistry, decreases coral calcification. I will show how the resistance of corals to ocean acidification can be linked to the biological control they exert on calcification.