14,000-year carbon accumulation dynamics in a Siberian lake reveal catchment and lake productivity changes

International audienceA multi-proxy paleolimnological analysis of a sediment core sequence from Lake MalayaChabyda in Central Yakutia (Eastern Siberia, Russia) was conducted to investigatechanges in lake processes, including lake development, sediment and organic carbonaccumulation, and changes in primary productivity, within the context of Late Pleistoceneand Holocene climate change. Age-depth modeling with 14C indicates that the maximumage of the sediment core is ∼14 cal kBP. Three distinct sedimentary units were identifiedwithin the sediment core. Sedimentological and biogeochemical properties in the deepestsection of the core (663–584 cm; 14.1–12.3 cal kBP) suggests a lake environment mostlyinfluenced by terrestrial vegetation, where organic carbon accumulation might have beenrelatively low (average ∼100 g OC m−2 a−1), although much higher than the global modernaverage. The middle section of the core (584–376 cm; 12.3–9.0 cal kBP) is characterizedby higher primary productivity in the lake, much higher sedimentation, and a remarkableincrease in OC delivery (average ∼300 g OC m−2 a−1). Conditions in the upper section ofthe core (30%) measured in the upper section of the core.Compact lake morphology and high sedimentation rates likely resulted in this lake acting asa significant OC sink since the Pleistocene-Holocene transition. Sediment accumulationrates declined after ∼8 cal k BP, however total OC concentrations were still notably high.TOC/TNatomic and isotopic data (δ13C) confirm the transition from terrestrial-influenced toaquatic-dominated conditions during the Early Holocene. Since the mid-Holocene, therewas likely higher photosynthetic uptake of CO2 by algae, as suggested by heavier(isotopically enriched) δ13C values (>−25‰)