Same core just with the paradoxical condition: A review of biogeochemical mechanisms of oxic methane production in lakes.

The discovery of oxic methane production has significantly expanded the conceptual boundaries of traditional methane production theory, extending research from marine to lake environments. This review systematically synthesizes current research progress on oxic methane production mechanisms in lakes, with particular emphasis on the processes by which methylated nitrogen (N)-, sulfur (S)-, and phosphorus (P)-compounds serve as key precursors to generate methane through both enzymatic biological reactions and chemical transformation pathways, and oxic methane production mechanisms driven by fundamental metabolic processes such as photosynthesis and nitrogen fixation. We specifically highlight that despite significant differences in environmental conditions and reaction pathways, both oxic and classic anoxic methane production fundamentally share combination of methyl group and hydrogen as the core step. This theoretical framework provides novel insights for a unified understanding of diverse methane production pathways involving both biological and chemical processes, holding significant implications for refining global methane cycle models.