This project assessed the long-term trends in ecosystem health of the Peace and Athabasca rivers by evaluating changes in the composition of invertebrate communities in relation to effluent loading. Existing long-term data sets for benthic invertebrates were compiled and their sampling procedures reviewed for deficiencies. Where the sampling procedures were sufficiently similar, quantitative statistical analyses (e.g., time series analyses) was performed on the data to determine whether patterns in benthic community structure were consistent with those predicted impacts from point-source inputs.