Making waves: phosphorus awakened by light: hidden fluxes and abiotic drivers in organic phosphorus transformation...

Lake phosphorus (P) cycling regulates bioavailable P supply and productivity. In eutrophic lakes, high total P but low orthophosphate indicates supply is controlled by rapid non-steady-state transformations, not pool size. Traditional studies emphasize microbial hydrolysis, sediment release, and particle exchange; photochemical processes have received comparatively less attention. Current assessments use net P changes, bulk DOP, and DOM optical properties, which cannot distinguish P production from uptake, adsorption, fixation, and reorganicization, and do not fully capture DOP heterogeneity or the decoupling of P‑bond transformation from carbon photobleaching. They may therefore underestimate photochemistry-associated P transformation. Our analysis highlights photochemistry as an underrecognized abiotic process in lake P cycling. Irradiation generates excited DOM and reactive intermediates, which can drive direct photochemical Pi release from some OP components or partial OP restructuring that produces P-containing products with altered reactivity. These products may subsequently enter enzymatic hydrolysis and microbial utilization pathways. Therefore, photochemistry should be incorporated into a kinetic framework linking organic P restructuring, biological utilization, and multiphase interfacial exchange. Future research integrating high-frequency monitoring, isotope tracing, molecular characterization, quantum chemistry, and modeling approaches will help further resolve gross photochemical Pi production fluxes, DOP molecular reactivity, and ecological impacts, thereby providing a basis for more systematically evaluating the contribution of photochemistry to lake P cycling and informing lake P management.