Access Type

Open Access Dissertation

Date of Award

January 2013

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Civil and Environmental Engineering

First Advisor

Shawn P. McElmurry

Second Advisor

David K. Pitts

Abstract

Pharmaceuticals, and personal care products (PPCPs), and other emerging contaminants, such as pesticides, are increasingly being detected in the environment. Important sources of these contaminants are waste water treatment plants and agriculture. Many of these contaminants are biologically active at low concentrations, and may impair physiological processes in exposed organisms, alter reproductive, endocrine or immune system function, and ultimately affect fitness and survival. These chemicals are often found in the environment as complex mixtures, and this complicates their evaluation of their toxicity. There is a need for high-throughput assays to rapidly assess the toxicity of these emerging contaminants. A behavioral assay utilizing freely swimming Daphnia pulex was developed to evaluate the sub-lethal chemical effects. Daphnia, a keystone species, are small planktonic invertebrate crustaceans (0.5-5.0mm) in freshwater ecosystems. They are commonly used for aquatic toxicity testing because of high sensitivity to changes in their environment. This novel optical bioassay was validated with a series of model compounds that have known modes of action. By measuring changes in their swimming activity, concentration-dependent behavioral responses in Daphnia were observed and quantified by the assay. Compounds with similar modes of action were found to elicit similar behavioral responses. Mixtures of compounds were then evaluated using the optical assay to identify possible synergistic, additive or antagonist effects. Additive effects at environmentally relevant concentrations were observed between mixtures of contaminants with similar modes of action, from different classes, and in the presence of wastewater effluent. Finally, in order to address potential ecosystem impacts, alterations in predator-prey interactions caused by exposure to an insecticide were observed in a community study. A prototype of a high-throughput assay that has great utility for evaluating the biological effects of chemicals and chemical mixtures was developed. This assay has demonstrated that chemicals within waste water may interact in complex ways to enhance toxicity, and may have important implications for regulatory agencies. The assay may also serve as a valuable ecotoxicological tool for studies aimed at assessing chemical contamination on ecosystem health.

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