RELATIONSHIP BETWEEN ECOLOGICAL EVOLUTION OF MOON LAKE AND SEASONAL VARIATION DURING THE LAST DEGLACIATION
Seasonal variations are a central aspect of climate change.Investigating the interplay between seasonal fluctuations and lake ecological evolution offers a fresh lens into the ecological responses of lakes to climatic shifts,while enhancing comprehension of the paleoclimatic significance conveyed by lake biological and biogeochemical proxies,ultimately fostering deeper insights into past climatic dynamics.This study delves into the correlation between lake ecological response processes and seasonal variations through the analysis of diatom records spanning the Last Deglaciation(886～497 cm,corresponding to 20111～9902 cal.a B.P.)within the Moon07-AB sediment core retrieved from the maar Moon Lake(47° 30.36′N,120°51.99′E;1190m a.s.1.)in Northeast China.Utilizing the ecological traits of diatoms,we preliminarily investigate this connection.Based on the cluster analysis of diatom relative abundances and absolute fluxes from 98 samples collected at 4 cm intervals within the sediment core,the lake diatom assemblage is divided into two primary zones and seven subzones.A comparative analysis of diatoms alongside representative paleoclimate records indicates that the ecological evolution of Moon Lake during the Last Deglaciation can be broadly categorized into two phases.The first phase,which extends from the Last Glacial Maximum to just before the Bølling interstadial,is characterized by a low-biomass,algae-dominated lake environment.In this context of global orbital-scale warming and millennial-scale climate fluctuations,the lake transformed from one primarily populated by mud-attached,low-light tolerant benthic diatoms(e.g.,Staurosira pseudoconstruens)under persistent year-round ice cover to one dominated by planktonic diatoms(e.g.,Pantocsekiella ocellata).The second phase,which spans from the rapid warming of the Bølling interstadial to the Early Holocene,witnessed a shift to a mixed ecosystem dominated by eutrophic planktonic diatoms(e.g.,Cyclostephanos delicatus and Stephanodiscus binatus)as well as various epiphytic benthic diatoms indicative of aquatic vegetation location.Notably,during the Younger Dryas cold period,which falls within this phase,planktonic diatoms nearly vanished,lake levels experienced significant declines,and trends toward marsh formation began to emerge.These transformative processes are closely tied to seasonal variations occurring in the context of orbital-scale warming and millennial-scale climate fluctuations.
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