<p>Elevated nutrient levels in lakes, particularly excess phosphorus and nitrogen, contribute to harmful phenomena such as harmful algal blooms, and the production of harmful substances, impacting water quality and ecosystem health. This study aimed to reveal the potential of hypolimnetic oxygenation through proton exchange membrane (PEM) water electrolysis as a novel approach to mitigate nutrient and metal ion release from lake sediments. In the first mesocosm experiment, the PEM system demonstrated its efficacy in enhancing dissolved oxygen (DO) concentration and improving redox potential in the sediment. However, a notable decline in pH was observed, resulting in the release of ammoniumnitrogen (NH₄-N), orthophosphate (PO₄-P), and an increase in metal ions, particularly Mn²⁺ and Fe²⁺. In the second experiment, the PEM system kept the water column oxygenated, reduced NH₄-N release, and promoted nitrification, shown by increased nitrate nitrogen (NO₃-N). Even after pH adjustment, bacterial growth remained suppressed, likely due to the generation of hydroxyl radicals during PEM water electrolysis. Oxygen transfer rate (OTR) declined in both systems. However, while the rate of decrease diminished in the air system after 1.25&#xa0;h, the OTR in the PEM system remained stable, indicating more efficient oxygen transfer. In light of these findings, both DO and pH are recognized as key regulators of nutrient and metal ion release from bottom sediments.</p> Graphical Abstract <p></p>