The temporal effects of heavy metal contamination on the fish community of the West Fork White River, Delaware County, Indiana, USA.

The importance of monitoring anthropogenic changes in a lotic system is not limited to chemical water quality monitoring. The addition of biological monitoring allows fish to be used as bioindicators because of their varying tolerance to pollution. For this study, we utilized long-term water quality and fish data to evaluate temporal changes brought on by passage of the Clean Water Act (1972). Non-metric multidimensional scaling (NMS) was used to describe changes in the fish community and also heavy metal concentrations of the West Fork White River in Muncie, Indiana, USA, over the past 33 years. A linear mixed effects model was used to evaluate the relationship between heavy metal concentrations and the fish community. The NMS results for both heavy metals and fish were separated into distinct decadal clusters. The shift in fish community data represented by NMS axis 1 was characterized by a drop in pollution-tolerant species and an increase in intolerant species. Decreases in heavy metal concentrations of chromium, zinc, and lead were also significant predictors of changes in the fish community. All NMS fish axis had a positive slope indicating an increase in intolerant species as heavy metal concentrations decreased. Our findings indicate that the water quality improvements documented in the West Fork White River have directly impacted its local fish community.