Mercury concentrations in lentic fish populations related to ecosystem and watershed characteristics

Abstract

Predicting mercury (Hg) concentrations of fishes at large spatial scales is a fundamental environmental challenge with the potential to improve human health. In this study, mercury concentrations were examined for five species across 161 lakes and ecosystem, and watershed parameters were investigated as explanatory variables in statistical models. For all species, Hg concentrations were significantly, positively related to wetland coverage. For three species (largemouth bass, pike, and walleye), Hg concentrations were significantly, negatively related to lake trophic state index (TSI), suggestive of growth biodilution. There were no significant relationships between ecosystem size and mercury concentrations. However, Hg concentrations were strongly, positively related to ecosystem size across species. Scores of small or remote lakes that have never been tested could be prioritized for testing using models akin to those presented in this article. Such an approach could also be useful for exploring how Hg concentrations of fishes might respond to natural or anthropogenic changes to ecosystems over time.

Fig. 1

Mercury concentrations of five fish species in Wisconsin lakes plotted against a wetland area index, b trophic state index, c ecosystem (lake) size, and d mean ecosystem size inhabited by each species (Log(Hg + 1) = 0.04x + 0.03, R² = 0.83), error bars represent the mean ± 1 SE). For panels a–c, Hg values were adjusted for effects of fish length by using standardized residual values from a fish length-Hg regression. For panel d, mean Hg values (log + 1) represent geometric means. Horizontal dashed line represents the US EPA 0.3 mg kg⁻¹ action level for a human consumption advisory. Only significant factors in multiple linear regressions (from Table 2) are shown as regression lines in these panels