HP10 New Advances in Estimating Effects of Toxicants on Populations
D135-136
1:20 PM - 5:20 PM, Thursday
() Integrating chemical and biological criteria.
Pacheco, Manoel1, McIntyre, Dennis1, Linton, Tyler1, 1 Great Lakes Environmental Center, Columbus, Ohio, USA
ABSTRACT- In an effort to integrate chemical and biological criteria, we present a system to derive benchmarks for protection of aquatic organisms that promote regulation of contaminants and focus on endpoints that adequately represent conservation targets. The foundation of our system lies on the use of quantile regression to quantify the decline in maximum number of organisms in samples along a gradient of contaminant concentrations. This limiting function is then applied to project the contaminant concentration associated with a threshold number of organisms. The threshold value is defined according to the study's objective and level of desired protection. Here, we defined it as 0.8 × 90th quantile of the number of organisms in samples from reference sites. We use the proposed system to derive field-based copper and zinc effect concentrations in Ohio rivers and streams. Comparisons of results with respective chronic values suggest that only the draft criteria for copper are adequately protective. Effect concentrations derived with our methods are likely to be less sensitive to impacts of confounding factors because high numbers of organism in samples are observed when negative effects of other stressors are absent or minimal. We discuss other advantages, limitations, and potential applications of the proposed system.
Key words: effect concentration, contaminant regulation, limiting factor, quantile regression