“Later, I would learn that the reason the conches and other shells were thinning was twofold. Over the years, as the pH of the ocean has decreased by what would seem the tiniest of measures, shellfish have become increasingly sensitive to the water’s acidity. The acid isn’t dissolving their shells. Something more complicated is happening here. The rise of carbon dioxide in the ocean has made calcium more soluble, and so the biological mechanisms that shellfish have used to compose their shells for millions of years no longer function as they once did. The process of converting calcium into shell is now slower. Population dynamics are at play, too. Conches with thicker shells are older ones. If we’re only turning up young conches, it means something is happening to the others, likely increased predation or predation by another name, overfishing.”