¹National Water Research Institute (NWRI), P.O. Box 5050, Burlington, Ontario, Canada, L7R 4A6
²Great Lakes Laboratory for Fisheries & Aquatic Sciences, P.O. Box 5050, Burlington, Ontario, Canada, L7R 4A6

*Corresponding author: David.Lam@ec.gc.ca

Summary

   Using the NWRI nine-box water quality model calibrated for pre- Dreissena years, with the model coefficients unchanged, we demonstrate that changes in phosphorus and dissolved oxygen in post- Dreissena years can be detected by the deviation of computed results from observed data. Through sensitivity analysis, we exclude other possible mechanisms to conclude that Dreissena can affect the total phosphorus concentration in Lake Erie, notably a concentration decrease in the east basin. On the other hand, changes in dissolved oxygen in the central basin hypolimnion are influenced less by Dreissena, as the model was able to simulate the observed oxygen concentration in Post- Dreissena years, using the original formulation on oxygen, thermal layer thicknesses and sediment oxygen demand and in the absence of a new Dreissena submodel. The impact of these and other findings on the phosphorus-dissolved oxygen relationship and its implication to the Lake Erie lakewide management plan is discussed using the results of this study.