Demonstration of a toxicological risk ranking method to correlate measures of ambient toxicity and fish community diversity

Abstract

The goal of this study was to assess a new toxicological risk ranking model, field validate it with results from a battery of sediment and water column bioassays, and identify correlations of model output with fish community and population metrics. The model has five components: severity of effect, degree of response, bioassay variability, consistency, and number of measured endpoints. The model can reliably reduce an array of ambient toxicity data into a site-specific metric that is appropriate for comparisons with other metrics, such as Index of Biotic Integrity (IBI) or community diversity indices. The model is tolerant of variable amounts of data between stations. It does not generate probability limits without repeated sampling. The model can identify trends between sampling stations and document where chemical contamination is contributing to community impacts as well as where toxicological impacts are not likely to be contributing to observed population level impairment. The model was evaluated with field/laboratory data. Test sites were located in tributaries of Chesapeake Bay watersheds that are impacted by industrial, urban, and agricultural land use patterns. The toxicological risk scores correlate with fish community health metrics. The strongest correlations were between sediment toxicity risk and bottom trawl fish community diversity index.