Increase in mercury in Pacific yellowfin tuna

Abstract

Mercury is a toxic trace metal that can accumulate to levels that threaten human and environmental health. Models and empirical data suggest that humans are responsible for a great deal of the mercury actively cycling in the environment at present. Thus, we would predict that the concentration of mercury in fish should have increased dramatically since the Industrial Revolution. Evidence in support of this hypothesis has been hard to find, however, and some studies have suggested that analyses of fish show no change in mercury concentration. By compiling and re-analyzing published reports on yellowfin tuna (Thunnus albacares) caught near Hawai’i over the past half century, we find that the concentration of mercury in these fish is currently increasing at a rate ≥ 3.8 % per year. This rate of increase is consistent with a model of anthropogenic forcing on the mercury cycle in the North Pacific, and suggests fish mercury concentrations are keeping pace with current loadings increases to the ocean. Future increases in mercury in yellowfin tuna and other fishes can be avoided by reductions in atmospheric mercury emissions from point sources.