This report documents a study into the use of three aquatic biomonitors, namely the freshwater mussel Elliptio complanata, the mayfly nymph Hexagenia limbata, a benthic invertebrate species, and the aquatic macrophyte species Myriophyllum spicatum, as biomonitors of water quality in a quantitative sense. The main objective of this research was to investigate if these three biomonitors can provide quantitative information of ambient contaminant concentrations in Ontario waters and sediments. The reason for this research is that due to analytical difficulties with contaminant analysis in water, it is presently very difficult to monitor on a regular basis the water quality of rivers and lakes in Ontario an a quantitative level. The use of biomonitors may provide a method to quantitatively determine water quality in Ontario waters.