Assessing Mercury Levels of Terrestrial Invertebrates in East Tennessee

Mercury is a pollutant that negatively impacts ecosystems.  An inorganic mercury spill occurred at the Y-12 Plant, which heads the Lower East Fork Poplar Creek (LEFPC) in Oak Ridge, TN.  Years later, mercury lingers in the environment where it is converted to the bioavailable methyl-mercury.  Elevated levels of total mercury in the waters of LEFPC and floodplain soils indicated the need for improved understanding of the threat mercury poses to terrestrial invertebrates dwelling in this area together with upper-level predators that feed on them. To assess the current threat, four families (Lycosidae, Trachelipodidae, Lumbricidae, and Cicadellidae) in three feeding guilds (carnivore, detritivore, and herbivore) were collected from the LEFPC floodplain and analyzed for total mercury and methyl-mercury.  Results reveal that earthworms have the greatest total mercury (22.16ppm), then isopods (6.82ppm), wolf spiders (3.54ppm), and leafhoppers (0.43ppm). Regression analysis showed a significant relationship between total mercury and methyl-mercury in all taxa when plotted against background total mercury soil concentrations except for leafhopper methyl-mercury quantities. Data indicate that though total mercury in earthworms is greater, wolf spiders and isopods have the most methyl-mercury (3.29ppm and 3.88ppm, respectively). Thus, these taxa potentially pose a greater environmental threat to upper-level predators.