Mercury in fishes from 21 national parks in the Western United States: inter- and intra-park variation in concentrations and ecological risk

A comprehensive study of mercury (Hg) contamination in freshwater fish across 21 national parks in the Western United States reveals significant ecological and human health risks. The research found that while only 5% of fish exceeded Hg levels linked to toxic responses within the fish themselves, a substantial 68% surpassed exposure thresholds recommended for safe human consumption. Notably, parks like Zion, Capital Reef, Wrangell-St. Elias, and Lake Clark exhibited high Hg concentrations even in small, invertebrate-feeding species such as speckled dace, indicating widespread contamination. The study analyzed over 1,400 fish from 86 sites spanning 4,000 kilometers, highlighting substantial variation in Hg levels both among and within parks. This suggests that localized processes significantly influence Hg distribution, necessitating more intensive monitoring to assess risks accurately.

Eagles-Smith, C. A., Willacker, J. J., & Flanagan Pritz, C. M. (2014). Mercury in fishes from 21 national parks in the Western United States: inter- and intra-park variation in concentrations and ecological risk. Open-File Report. https://doi.org/10.3133/ofr20141051