Chironomid-based Late Glacial and Early Holocene summer temperature variability in Lake Prokoško (Western-Balkan region)

The Late Glacial and Early Holocene were marked by abrupt climate oscillations, yet high-resolution quantitative temperature reconstructions remain scarce in the climatically transitional Western Balkans. Here, we present a chironomid-based mean July air temperature (T July ) reconstruction from subalpine Lake Prokoško (1670 m a.s.l., Bosnia and Herzegovina), spanning ~18–9.87 ka BP. Using a Swiss–Norwegian calibration dataset together with geochemical (XRF, LOI) and palynological proxies, we reconstruct the climatic and limnological evolution of the lake ecosystem.Before ~14.6 ka BP, Lake Prokoško was a cold oligotrophic glacial environment with T July below 8.0 °C, dominated by cold-stenotherm taxa such as Pseudodiamesa . The Bølling–Allerød interstadial experienced rapid warming to ~10.2 °C (+2.6 °C), accompanied by enhanced aquatic productivity and catchment stabilization. During the Younger Dryas (~13.07–11.61 ka BP) July mean temperatures declined by ~2.3 °C (to ~7.9 °C), coinciding with increased soil erosion, catchment instability, and the return of cold-water fauna. The onset of the Early Holocene brought a further warming of 2.9 °C (>12.0 °C), leading to stable summer stratification, hypolimnetic anoxia, and a shift to a highly productive mesotrophic–eutrophic lake state. Regionally, the ~2.3 °C Younger Dryas cooling places Lake Prokoško between the stronger Alpine (>3.0–4.0 °C) and weaker Eastern Carpathian (<1.0 °C) responses. Our results support a west–east decreasing summer cooling gradient across Europe during the Younger Dryas, linked to diminishing North Atlantic influence inland.