Evaluation of Fish and Macroinvertebrate Indices of Biotic Integrity in the Bioassessment of the Illinois River Basin

Evaluating performances of the fish and invertebrate Indices of Biotic Integrity (IBIs) for a region is important to maintain rigorous assessment of the environmental quality of streams, especially with increasing urbanization. Timing of the assessment is considered important, with the critical season (low flow, high temperature) preferred, but the primary season (spring– summer) may be as efficient. I assisted with the collection and analysis of fish and macroinvertebrates using methods developed by the United States Environmental Protection Agency’s (USEPA) Rapid Bioassessment Protocols (RBPs) and the Arkansas Department of Environmental Quality (ADEQ), along with obtaining habitat and chemical assessments during primary and critical periods during 2007-2009 at ten sites in the Illinois River Basin up and downstream of two wastewater treatment plants (WWTPs). My objectives were to (1) compare fish and macroinvertebrate IBIs for use in the Illinois River Basin; (2) investigate correlations with each IBI and its metrics to nutrient, habitat, and watershed variables; (3) compare the efficacy of the IBIs during both critical and primary seasons; and (4) determine how two WWTPs in the area affect downstream water quality into Oklahoma. The two IBIs were strongly correlated with each other (Rs of 0.59); however, macroinvertebrates outperformed the fish. More regionally specific fish metrics should allow for better performing fish IBIs, but adequate performance was found. Combining the seasons’ data allowed for a more comprehensive and statistically significant assessment; however, the primary season evaluated each site comparably to the combined data and generally outperformed the critical seasons. The combined and primary seasons’ macroinvertebrate IBIs revealed sites with lowered environmental quality below the WWTPs but with quick returns to reference conditions. My results indicate that it may be possible to test IBIs during only the primary seasons to get efficient water quality and site comparison assessments