PARENT SESSION
MA6 - Contaminant Effects on Amphibians & Reptiles
Chair: Bridges, Christine¹, ¹
Co-chair: Krest, Sherry², ²
8:00 AM to 12:00 PM - Monday, 18 November 2002
Room Ballroom B

(217) Establishing Causality in Amphibian Ecotoxicological Studies Designed to Support Ecological Risk Assessments.

Fort, Douglas^*,1, Rogers, Robert¹, Thomas, John¹, ¹ Fort Environmental Laboratories, Stillwater, OK, USA

ABSTRACT- One of the greatest obstacles in providing adequate amphibian data to support ecological risk assessment (ERA) is associated with data gaps that limit the establishment of multiples lines of evidence. In order to establish multiple lines of evidence needed in risk assessment; causality, ecological significance, and ecosystem recovery must be addressed. Ecological significance and ecosystem recovery involve collection of field data that supports an understanding of the effect elicited and eventual ecological restoration achieved at the local population level. However, establishing causality often is a more difficult process. To establish causality, the effects must be identified, exposure proven, the response demonstrated, and mechanistic links established. Identification of the effect requires definition of the endpoints to be measured at the local population, community, and individual species levels. Exposure can be established by measuring the presence of chemical and non-chemical stressors in the environment, as well as, tissue residues. The effects are best demonstrated by collecting ecotoxicological data with high laboratory-to-field extrapolation potential. Mechanistic links between exposure and effect are established through the use of well-constructed biomarker studies. Adequate laboratory-to-field extrapolation data are comprised of a combination field-based and laboratory-based data. Field data can include in situ exposure studies and examination of field collected specimens. Laboratory data can include the culture of indigenous species collected from the field in the laboratory and the culture of representative species in the laboratory under field simulated conditions. Adequately designed laboratory data provides a distinct advantage in helping establishing causality in that it provides a higher level of experimental control and greater degree of experimental design flexibility. Laboratory study designs should include evaluation of specimen at different life stages using partial and full lifecycle studies, cross-over exposure experiments to evaluate the influences of transgenerational transport and environmental exposure on the effects induced, toxicant spiking studies, appropriate biomarker studies. This approach has been successfully used in recent ERAs.

Key words: Lab-to-field extrapolation, ERA, amphibians, in situ