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(80-82) Separating Natural and Anthropogenic Stressors Using In Situ and Laboratory Approaches. McWilliam, Ruth*,1, Burton, Allen1, Irvine, Cameron1, Johnson, Jeff1, Schwab, Becky1, 1 Wright State University, Dayton, OH, USA ABSTRACT- Assessments often focus on chemical contamination and do not assess the role of natural stressors. A common approach to separating chemical stressors is to use Toxicity Identification Evaluations (TIEs) whereby samples are fractionated in the laboratory and then toxicity and chemical testing conducted. We have demonstrated an in situ-based assessment strategy for determining whether impairment exists and to separate stressor compartments and types. Multiple sites across the United States were evaluated. The approach involves water and sediment exposures, separating suspended and bedded sediment, upwelling/downwelling, and low and high flow effects. Multiple species occupying differing niches and trophic levels were evaluated for lethal and sublethal responses and supplemented with indigenous biota and laboratory-based responses. In some cases, adverse effects were detected quicker in situ and sublethal responses were not needed. Once impairment was identified in the water or sediment column, in situ TIEs were conducted to separate stress due to metals, nonpolar organics, ammonia and photo-induced toxicity. Results showed in situ treatment responses tend to be more sensitive and realistic than laboratory-based responses and effectively separated major stressor compartments and classes. Natural stressors dominated at some sites and must be considered in the assessment process. The resulting information is useful in weight-of-evidence based decisions on the need for more focused risk assessments or management decisions. Key words: in situ toxicity, bioaccumulation, chronic toxicity |
