Date Awarded

2011

Document Type

Thesis

Degree Name

Master of Science (M.Sc.)

Department

Virginia Institute of Marine Science

Abstract

The studies involved in this thesis expanded the current project being conducted in Dr. Newman’s laboratory that aimed to define and quantify the impacts of mercury movement in contaminated aquatic and terrestrial food webs in the South River watershed (Virginia, USA). This expansion involved a two phase study, which fulfilled the requirement of a master thesis.

Previous research in our lab documented mercury biomagnification in the river itself and two floodplain locations on the South River watershed. Predictive models were built for mercury concentration in members of these food webs. These studies reached a preliminary conclusion that mercury biomagnification in members of floodplain food webs was faster than that of the aquatic food web. To substantiate this finding and further understand the factors that might produce the differences observed among floodplain locations, two additional floodplain locations were sampled and modeled in 2010. Overall, the models constructed in this study for predicting methylmercury were superior to models for total mercury or the percentage of the mercury present as methylmercury. Including previous models for other sites, four of five attempted methylmercury models based on δ15N met the criterion for useful prediction. For the floodplain models, thermoregulatory strategy was found to have substantial influence on mercury concentrations of food web members. The food web biomagnification factors for the four floodplain locations were consistently higher than that of the contiguous aquatic food web.

The second phase of this research focused on description and determination of current mercury exposure to adults of three avian species during nesting on the South River floodplain and judgment of the risk of harmful mercury exposure to these species by comparing the mercury exposure distributions to published toxicity test results. This study incorporated a formal expert elicitation involving a modified Delphi framework and a Monte Carlo simulation to accomplish a probabilistic risk assessment. Simulations from this study predicted the probability that an adult bird during breeding season would ingest harmful amounts of mercury during daily foraging and also the probability that the average mercury ingestion rate for the breeding season of an adult bird would exceed published rates found to cause harm to other birds (>100 ng total Hg/g body weight per day).The probabilities that these species’ averaged ingestion rates exceeded the threshold value were all less than 0.01.

DOI

https://dx.doi.org/doi:10.25773/v5-hkqc-kw61

Rights

© The Author

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