Whale Earwax Archives Ocean Stress History

Researchers discovered that baleen whale earwax plugs, which grow in six-month layers, contain a lifelong chemical record. By analyzing these plugs, scientists can measure cortisol, testosterone, and pollutants like mercury and DDT metabolites at six-month intervals. A 2018 study processed 20 earplugs, creating a dataset spanning 146 years from 1870 to 2016, revealing whale stress levels correlate with historical whaling and modern ocean conditions.