The ocean’s chemistry is shifting in ways that could blunt one of nature’s most iconic weapons: shark teeth. A new wave of research shows that as seas absorb more carbon dioxide and grow increasingly acidic, the razor-sharp teeth of blacktip reef sharks and other species begin to corrode, crack, and weaken.⁠ ⁠ Sharks normally offset tooth loss by growing new ones, often tens of thousands over a lifetime. But when acidity accelerates wear faster than replacement, even these top predators face a critical disadvantage. In lab experiments, teeth kept in seawater adjusted to the pH levels scientists expect by the year 2300 showed about twice as much damage as those in present-day conditions. Cracks, holes, and root corrosion reduced both sharpness and structural strength.⁠ ⁠ The culprit is ocean acidification, driven by carbon dioxide emissions dissolving into seawater. Global average pH has already fallen from 8.2 to about 8.1 since the industrial revolution, a 30 percent increase in acidi...