Final answer:
Ocean acidification adversely affects corals and mollusks, which rely on the formation of carbonate ions to build their shells and skeletons.
Step-by-step explanation:
Ocean acidification is the process of ocean waters decreasing in pH. It occurs when carbon dioxide (CO2) emissions dissolve in the ocean, resulting in increased acidity. The organisms most likely to have the greatest impact from ocean acidification are corals and mollusks, including shellfish. These organisms rely on the formation of carbonate ions from dissolved CO2 to build their shells and skeletons. As ocean acidification increases, the availability of calcium carbonate declines, posing a threat to the survival of these organisms.