LAUSR

Abstract Invasive dreissenid mussels have successfully established dense population at nearshore and mid-depth regions, and significantly altered the ecosystem and food web dynamics in Lake Michigan. In this work, we used a high-resolution hydrodynamic-biogeochemical model to evaluate how these extensively colonized benthic mussels will affect the dynamics of phosphorus cycling in Lake Michigan. Model results demonstrated the important role of mussels in re-engineering of phosphorus cycling, with their filtering and excretion activities causing increasing lake-wide ratio of dissolved (DP) and particulate (PP) phosphorus. The diffusive flux at the bottom of mid-depth site was significantly enhanced compared to the sedimentation due to the benthic mussels, with an average effective flux 12.1 times greater than the passive setting, which was consistent with the field observations. Nearshore-offshore phosphorus transport displayed substantial spatial and temporal variabilities, and the nearshore was identified as an overall source/sink of PP/DP to the offshore region. The simulation results with mussels revealed that the mussel could effectively reduce the PP transport to the offshore region, potentially risking the pelagic fish abundance. This study provides key quantitative estimates for the impact of benthic mussels on vertical PP delivery and lake-wide nearshore offshore phosphorus transport, and could inform potential ecosystem management strategies of Lake Michigan and other dreissenid mussel invaded lakes.