Late Holocene transition from natural to anthropogenic forcing of lake archaeal community dynamics in semi-arid northern China

Archaea are key mediators of biogeochemical cycles because of their diverse metabolic capacities. Their community structure is shaped by multiple drivers, but how the relative importance of these drivers changes over long timescales remains poorly understood. This uncertainty partly reflects the limited ability of traditional paleoecological proxies to reconstruct archaeal community composition. Here, we used sedimentary DNA from Lake Gouchi, a well-documented lake in northern China, to reconstruct Holocene archaeal dynamics and assess their responses to natural and anthropogenic forcing. The community was dominated by halophilic archaea, with methanogenic and ammonia-oxidizing archaea as minor groups. During 9600–2000 cal yr BP, halophilic archaeal abundance remained low but gradually increased, while other groups peaked in several layers. After 2000 cal yr BP, halophilic archaea experienced a sharp increase and became overwhelmingly dominant. Environmental analyses identified salinity, precipitation, and total nitrogen as the main controls on community structure. Mid-Holocene aridification, warming, and salinization primarily favored the expansion of halophilic archaeal assemblages before 2000 cal yr BP, whereas intensified salt production since the Han Dynasty further promoted their accelerated proliferation after 2000 cal yr BP. These results provide a long-term record of archaeal dynamics at a saline lake in a semi-arid region and reveal a shift from natural to anthropogenic forcing. They also suggest that halophilic archaea have potential value for regional paleoenvironmental reconstruction.