Bartz, K.K., M.P. Hannam, T.L. Wilson, R.F. Lepak, J.M. Ogorek, D.B., Young, C.A. Eagles-Smith, D.P. Krabbenhoft. 2023. Understanding drivers of mercury in lake trout (Salvelinus namaycush), top-predator lake fish from southwest Alaska parklands. Environmental Pollution 330: 121678. https://doi.org/10.1016/j.envpol.2023.121678
Abstract
Mercury (Hg) is a widespread element and persistent pollutant, harmful to fish, wildlife, and humans in its organic, methylated form. The risk of Hg contamination is driven by factors that regulate Hg loading, methylation, bioaccumulation, and biomagnification. In remote locations, with infrequent access and limited data, understanding the relative importance of these factors can pose a challenge. Here, we assessed Hg concentrations in an apex predator fish species, lake trout (Salvelinus namaycush), collected from 14 lakes spanning two National Parks in southwest Alaska, U.S.A. We then examined factors associated with the variation in fish Hg concentrations using a Bayesian hierarchical model. We found that Hg concentrations in lake water were uniform and very low. Conversely, Hg concentrations in lake trout were variable and, in some lakes, very high, exceeding Alaska’s human consumption threshold at half of our study sites. Additionally, model results indicated that fish age and, to a lesser extent, body condition best explained variation in Hg concentration among fish within a lake, with Hg elevated in older, thinner lake trout. Other factors, including plankton methyl Hg content, fish species richness, volcano proximity, and glacier loss, best explained variation in lake trout Hg concentration among lakes. Collectively, these results provide evidence that multiple, hierarchically nested factors control fish Hg levels in these lakes.