As large, oceangoing predators, sharks rely heavily on their sense of smell to locate prey dispersed throughout an expansive environment. This honing ability, however, may be compromised by the ocean-wide changes predicted to occur by the end of the century, researchers report online this week in Global Change Biology. Ocean waters are becoming increasingly acidic as they absorb the atmospheric CO2 released by human activities. Previous research has shown that CO2-rich, acidic waters may impair the ability of reef fish to smell predators. The new study examines the effects of ocean acidification on the odor-tracking ability of sharks to locate prey. For 5 days, the team exposed sharks to waters with current ocean CO2 levels and the elevated CO2 concentrations predicted to occur by mid- and late-century. Sharks were then released into a pool where a “squid juice” odor attractant was dispensed, and shark tracking and attack behaviors were monitored. The researchers found that sharks exposed to the highest CO2 levels significantly avoided, rather than gravitated toward, the prey odor cues and attacked food less aggressively. Feeding behaviors are critical for shark survival, therefore ocean acidification could have far-reaching effects on already threatened shark populations and subsequent, cascading effects on marine ecosystems. Although sharks have adapted to acidifying oceans in their evolutionary history before, they’ve never had to adapt as quickly as the changes are occurring today.