Sediment Resuspension as a System-Wide Driver of Legacy and Bioavailable Phosphorus Release in Lake Erie

Freshwater ecosystems worldwide face persistent eutrophication and harmful algal blooms (HABs), driven primarily by external phosphorus (P) inputs from agricultural runoff. However, internal P loading remains poorly quantified in eutrophic systems such as Lake Erie, which store substantial legacy P pools within benthic sediments. Here, we resolved system-wide internal P loading from sediment resuspension, an overlooked but significant P cycling pathway. During the observed event, sediments released 2.3-11 × 10^-2 g m^-2 of bioavailable P, 22-256× greater than previously reported aerobic diffusive fluxes, highlighting resuspension as a major episodic internal P source in western Lake Erie. Using Sentinel-3 remote sensing reflectance, we quantified changes in suspended particulate matter (SPM) (ΔSPM) with a single-wavelength semiempirical algorithm that enabled a mechanistic, spatially resolved framework linking benthic sediment traits to satellite-derived SPM for basin-wide P release estimates during resuspension. Beryllium-7 analysis showed that repeated sediment mixing reworks multiyear deposits and remobilizes legacy P when resuspended. Compared to Maumee River spring P targets, this single event contributed ∼4.8% and ∼7.0% to total and soluble reactive P, respectively. Quantifying resuspension-driven P loads is expected to better constrain interannual HAB variability and contribute to assessing nutrient management outcomes for Lake Erie and similar aquatic systems.