Date of Award

8-2016

Degree Type

Thesis

Degree Name

Master of Science

Major

Entomology and Plant Pathology

Major Professor

Jerome F. Grant

Committee Members

John K. Moulton, Teresa J. Mathews

Abstract

Mercury (Hg) and methylmercury (MeHg) are environmental concerns due to their abilities to cause neurological, reproductive, and other physical damage to wildlife. Lower East Fork Poplar Creek (LEFPC), stemming from the Y-12 National Security Complex, located in Oak Ridge, TN, has elevated concentrations of inorganic mercury, a majority of which was released between 1950 and 1963. This inorganic mercury has been, and is currently, converted to methylmercury. An ecological assessment in 2011 revealed high concentrations of methylmercury in riparian spiders along LEFPC. These results suggested the transfer of mercury from aquatic to terrestrial systems may be higher than previously expected and suggested the need for a more complete study of the concentrations of total mercury and methylmercury in terrestrial invertebrates along LEFPC floodplain. A study was designed to address these needs.

The first objective was to quantify total mercury and methylmercury in terrestrial invertebrates along LEFPC floodplain. Four terrestrial invertebrate taxa were chosen for analysis: isopods (detritivore), leafhoppers (herbivore), wolf spiders (carnivore), and earthworms (detritivore). Earthworms (Family: Lumbricidae) had the highest concentration of total mercury at 7.04 ppm, while wolf spiders (Family: Lycosidae) and isopods (Family: Trachelipodidae) had the highest concentrations of methylmercury. The second objective was to investigate the relationship between total and methylmercury concentrations and trophic levels in terrestrial invertebrates. Methylmercury was found to increase with trophic level. Variation between methylmercury concentrations and trophic levels were seen in correlation with location along LEFPC. The third objective was to examine if the distance from the contaminated stream influenced mercury concentrations in the floodplain soils and invertebrates. Mercury concentrations were higher at upstream locations, closest to the source of mercury, and decreased with distance downstream. The fourth objective was to examine the relationship between soil and biota mercury concentrations, bioaccumulation factors (BAF), and compare BAFs in LEFPC to those at other contaminated sites. Earthworms had the highest BAFs and overall, BAFs in this study were lower than reported at other sites. The information from this study will inform management decisions on conservation efforts to protect upper-level predators in areas where mercury and methylmercury are present.

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