Environmental structuring of early biosphere evolution: spatial decoupling of oxygenic photosynthesis persistence and ecological expansion

The emergence of oxygenic photosynthesis fundamentally transformed Earth’s surface environment and ultimately enabled atmospheric oxygenation and complex life. However, geological evidence suggests a substantial temporal gap between early biological carbon fixation and the later rise of stromatolites and atmospheric oxygenation during the Great Oxidation Event (GOE). Here, we propose a conceptual framework in which the long-term persistence of oxygenic photosynthesis and its later ecological expansion were spatially decoupled. We suggest that ultraviolet-attenuated environments preferentially supported the persistence of early oxygenic phototrophs, whereas warm, shallow, high-productivity environments promoted ecosystem-scale expansion. Iron redox buffering further constrained oxygen accumulation prior to the GOE. Within this framework, early carbon isotopic signatures reflect spatially restricted metabolic activity, whereas stromatolites record a later phase of ecological expansion. More broadly, this perspective suggests that environmental structure may regulate the ecological scaling of metabolic innovations in planetary biospheres.