RP12 Application of Spatially Explicit Techniques in Ecological Risk Assessment
Thursday, 17 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(AAA-1116-601265) Ecological impact of agriculture and point sources on fish assemblages in Ohio rivers in a multiple stress context.

de Zwart, D¹, Posthuma, L¹, Dyer, S², ¹ RIVM. Lab for Ecological Risk Assessment, Bilthoven, Netherlands² The Procter & Gamble Company, Cincinnati, OH, USA

ABSTRACT- Ohio rivers have extensively been monitored for the occurrence of fish species in relation to habitat suitability and chemical exposure. Concentrations of contaminants emanating from point sources (municipal wastewater treatment plants) and from agricultural practices were obtained from federal databases as well as watershed-based exposure models (e.g., GIS-ROUT, WASP). Factors that are coincident with point sources and non-point sources (e.g., percent cumulative effluent, amount of flow over row crops) were also obtained via these exposure models. Species Sensitivity Distributions (SSD) were applied to contaminant concentrations to estimate measures of toxic risk per sampling site (ms-PAF, multi-substance potentially affected fraction of species). For example, atrazine, metals, ammonia and household product chemicals were assessed for several hundred sites. The ecological meaning of these toxic pressure estimators in terms of species occurrence and abundance effects in a real ecosystem is largely unknown. The Ohio data have been used for ecoepidemiological modeling that quantifies the observed ecological effects on species composition and that attributes the effects to the probable underlying causes. To accomplish this, we linked an ecologically predictive model with ecotoxicologically-based methods via GLM regression. This analysis explains the magnitude of impact on a site by the individual and cumulative risk of toxic compounds and/or degraded habitat conditions. The results are GIS-mapped as Effect and Probable Cause (EPC) pie diagrams to reveal local impact as pie size and the relative contribution of stress factors as slice size.

Key words: Community responses, Ecoepidemiology, Ecological risk assessment, Mixture toxicity