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.
Dhiman et al. (Fri,) studied this question.