| Biomarkers are biological indicators that measure change at the sub-organismal level or below (molecular, biochemical, histological and physiological), that respond to exposure to, or doses of, xenobiotic substances. At present the use of biomarkers in ecological risk assessment is limited, however advancements in biochemistry, analytical chemistry, and toxicology are resulting in the detection of insults at lower levels of biological organization and shifting the focus from retrospective analysis to preemptive characterization of potential ecological risk. The focus of this research was the application of biomarkers in laboratory and field studies with the ultimate goal of characterizing the potential application of biomarkers in ecological risk assessment. This was accomplished by investigating (1) the use of biomarkers ethoxyresorufin-O-deethylase (EROD), bile fluorescence, and metallothionein in the assessment of contaminated impoundments in the Saluda-Reedy watershed, (2) the use of vitellogenin gene expression and DNA damage as biomarkers to determine the effects of urbanization, and (3) the effects of dose, feeding status, and time post exposure on fish bile metabolites and EROD activity on channel catfish exposed to benzo[a]pyrene. Results of these studies consistently demonstrated the utility of biomarkers to refine the estimate of contaminant exposure. EROD, bile fluorescence, and metallothionein results combined with chemical measurements showed that PAHs are present and bioavailable to fish in the Saluda-Reedy watershed, while metals were shown to be present, but not bioavailable to fish. Increases in DNA damaging compounds and vitellogenin were linked to increases in urbanization. The effect of dose and time post exposure were the most influential factors on fish bile metabolites and EROD activity in channel catfish exposed to benzo[a]pyene. Overall, these biomarkers provide insight into contaminant bioavailability and would reduce the uncertainty associated with exposure assessments in ecological risk assessments. A model (integrated endpoint evaluation) was developed that integrates chemical and biological endpoints with the goal of simplifying complex data sets. The model normalizes all data to the same scale and uses a simple graphical representation to simplify the data and calculate a single integrated output value. |
