Investigating interactions between macroinvertebrate indices, water quality parameters, and stream quality classifications in a Wisconsin agricultural watershed

Increasing agricultural and urban land use poses a growing threat to freshwater ecosystems worldwide, contributing to nutrient loading and degradation of surface water quality. Stream restoration, such as riparian vegetation, can help mitigate nonpoint source pollution, yet its ecological outcomes remain variable. Aquatic macroinvertebrates are widely used as bioindicators for water quality due to their sensitivity to environmental change, but their responses to stream impairment and restoration in the context of ongoing land-use pressures are less well understood. This study investigates associations between water quality parameters, biotic indices, and stream classifications using macroinvertebrate and water quality data collected from stream sites within an intensively managed agricultural watershed in the Midwestern United States during the autumn seasons of 2021 and 2022. Numerical analyses were used for water quality and macroinvertebrate indices, while stream classifications-impairment status, nutrient thresholds, and habitat quality-were analyzed categorically. Nonmetric multidimensional scaling assessed macroinvertebrate correlations with water quality, while Kruskal-Wallis tests identified statistical differences across stream classifications. Findings show that sites with stream improvement projects exhibit higher macroinvertebrate index scores, with strong correlations between higher index scores, higher dissolved oxygen, and lower total phosphorus. These results suggest macroinvertebrates and water quality parameters are effective indicators of stream impairment and habitat quality, though long-term links to restoration require further study. Findings contribute to a broader understanding of how biological indicators can inform restoration success and impairment conditions in agriculturally impacted watersheds across temperate regions.