A new study shows that trace elements found in fish ear bones can be used as biogenic tracers to track coal ash contamination. Strontium isotope ratios in the otoliths of fish collected from two lakes that received coal ash effluents matched strontium isotope ratios in contaminated pore water samples from the lakes' bottoms. This marks the first time strontium isotope ratios have been used as fingerprints to track coal ash's impacts in living organisms.