Nonlinear diatom responses to millennial-scale climate-mediated terrestrial-aquatic interactions in a treeline lake on the Tibetan Plateau

Understanding the complex, nonlinear responses of aquatic ecosystems to climate-driven terrestrial-aquatic interactions is crucial for identifying the mechanisms underlying ecosystem dynamics. This study investigates the diatom community changes over the past 20 kyr in Cuoqia Lake, a treeline lake on the southeastern Tibetan Plateau . By integrating fossil diatom assemblages with cladoceran , geochemical, and sedimentological proxies, we reveal how differential mechanisms influenced diatom responses from post-glacial lake formation to early Holocene treeline shifts. Our results indicate abrupt, phase-dependent shifts in diatom and cladoceran communities during major climatic transitions, particularly at the Late Glacial/Holocene boundary. These regime shifts were likely driven by cascading effects of glacial retreat, soil development and subsequent increases in organic matter inputs associated with climate warming and treeline migration. Notably, while diatoms responded quickly to initial climate warming, cladocerans exhibited a delayed response, reflecting its greater sensitivity to catchment vegetation stabilization. These findings highlight the attendant changes in climate, vegetation, and lake ecosystems on millennial time scales, illustrating the tight biogeochemical coupling between terrestrial succession and lake dynamics during glacial retreat and landscape colonization. This study offers critical insights into the mechanisms behind primary succession in alpine lake ecosystems and provides a valuable framework for understanding the ecological impacts of ongoing and future climate warming. • Diatom and cladoceran shifts in Cuoqia Lake reveal climate-driven ecosystem changes. • Human activities since 4 cal ka BP increased nutrient input and lake productivity. • Deforestation and grazing intensified soil erosion, altering lake's nutrient dynamics. • Post-glacial warming (∼1.1 °C) triggered rapid ecological reorganization in alpine lakes.