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(019) Identifying major stressors using tiered, in situ-based approaches. Burton, G. Allen1, Rowland, Caroyln 1, Greenberg, Marc1, Johnson, Jeffrey1, Lavoie, Daniel1, Nordstrom, Juanita1, 1 ABSTRACT- Assessments of aquatic ecosystem contamination were conducted at several sites across the United States, impacted by differing stressors. The accuracy, strengths and limitations of traditional and in situ assessment methods were evaluated, taking into account overlying water and sediment compartments. Methods included use of sediment quality guidelines, laboratory and in situ toxicity (survival and growth), bioaccumulation tests, resident species tissue residues, and characterization of habitat, hydrology, physicochemistry and benthic macroinvertebrate communities. Multiple test species were used in caged exposures partitioned into overlying water (high and low flow), pore water/ground water, sediment-water interface and surficial sediment compartments. Acute to chronic toxicity existed in sediments at all impacted streams, resulting from ammonia, metals, pesticides, chlorobenzenes, PAHs and/or PCBs. In addition, in situ toxicity tended to increase with increasing degree of exposure to sediments (i.e., overlying water to pore water). However, toxicity often increased during high flow conditions at some sites. A tiered assessment scheme was most efficient, delaying the more expensive chemical and laboratory assays for further stressor confirmation. While a combination of traditional, standardized assessment methods and in situ approaches was useful (particularly in a weight-of-evidence approach), the in situ methods provided the most realistic exposures and greater accuracy at moderately contaminated sites in Tier 1 evaluations. Key words: Sediment, In situ, Ecological risk, Stressors |
