Mercury Bioaccumulation in a Terrestrial Food Web of a Montane Forest

We investigated mercury (Hg) concentrations in a terrestrial food web in high elevation forests in Vermont. Mercury concentrations increased from autotrophic organisms to herbivores < detritivores < omnivores < carnivores. Within the carnivores studied, raptors had higher blood mercury concentrations than their songbird prey. The Hg concentration in the blood of the study focal species Bicknell’s thrush varied over the course of the summer in response to a diet shift related to changing food item availability. The montane food web is more detrital-based (with higher Hg concentrations) in early summer and more foliage-based (with lower Hg concentrations) during late summer. There were significant year effects in different ecosystem compartments indicating a possible connection between atmospheric Hg deposition, detrital-layer Hg concentrations, arthropod Hg concentrations, and passerine blood Hg levels.