Late Quaternary Climate Reconstruction and Lead-Lag Relationships of Biotic and Sediment-Geochemical Indicators at Lake Bolshoe Toko, Siberia

Abstract

Millennial-scale climate change history in eastern Siberia and relationships between diatom diversity, paleoclimate, and sediment-geochemical lake system trajectories are still poorly understood. This study investigates multi-proxy time series reaching back to the Late Pleistocene derived from radiocarbon dated Lake Bolshoe Toko sediment cores, southeastern Yakutia, Russia. We analyzed diatoms, elements (XRF), minerals (XRD), grain-size, organic carbon, and included chironomid analyses and published pollen-data for quantitative paleoclimate reconstruction. Changes in diatom species abundances reveal repeated episodes of thermal stratification indicated by shifts from euplanktonic Aulacoseira to Cyclotella species. Chironomid and pollen-inferred temperature reconstruction reveal that the main shift between these diatom species is related to the onset of Holocene Thermal Maximum (HTM) at 7.1 cal ka BP. Comparison to other paleoclimate records along a north-south transect through Yakutia shows that the HTM was delayed as far south as the Stanovoy mountains. Relationships between sediment-geochemistry, paleoclimate variability and diatom species richness (alpha diversity) was tested in a moving temporal offset approach to detect lead-lag relationships. Sediment-geochemical data, mainly uniform during the Holocene, revealed strongest positive or negative correlations ahead of species richness changes. Mean July air temperature (TJuly) reconstructions correlate with both Hill numbers and relative assemblage changes indicated by sample scores of multidimensional scaling analysis (MDS) over the entire time series. We found that sediment organic carbon revealed distinct positive correlations, i.e., centennial-scale delay to increases in diatom effective richness (Hill numbers N0 and N2). We conclude that a lag of deposited organic carbon concentrations behind changes in diatom alpha diversity reveals that species richness can augment the production and thus sequestration of organic matter in comparable lake systems.

14,000-year Carbon Accumulation Dynamics in a Siberian Lake Reveal Catchment and Lake Productivity Changes

“…High Ti values can also indicate increased run-off from precipitation events and/ or increased aeolian deposition (Davies et al, 2015). This could have been the case at the study site, with active soil erosion and transport associated with poorly developed vegetation cover during this period of cold, Late Pleistocene climate (Biskaborn et al, 2021b). Precipitation was generally low in the study site region during the time of deposition, making increased aeolian deposition more likely than increased run-off from precipitation events (Biskaborn et al, 2012).…”

“…OC accumulation rates for Unit 3 are slightly lower, but still quite high (average of ∼200 g OC m −2 a −1 , ranging from 144 to 354 g OC m −2 a −1 ) compared to other reported values in both temperate and high-latitude regions (Meyers, 2003;Vyse et al, 2021 and references therein). As Lake Malaya Chabyda is located in a semiarid climate, with high summer temperatures and humid climate, the primary production in its ecosystems can be quite high, resulting in strong accumulation of organic matter in bottom sediments (Biskaborn et al, 2021b). Given the significant increase of OCAR (Figure 5) and TOC accumulation (Figure 4) around 11 cal kBP, Lake Malaya Chabyda likely transitioned to an OC sink at approximately the Pleistocene-Holocene transition.…”

Long-term fungus-plant co-variation from multi-site sedimentary ancient DNA metabarcoding in Siberia

“…To our knowledge, we conducted the first study on fungus-plant interactions and co-occurrences in the palaeo context, assessing community shifts in boreal forests as well as tundra ecosystems. However, our results can only be seen as a first proxy on future fungal community changes in response to warming as the magnitude of warming differs strongly between the studied samples and present warming and any relationship may incorporate lagged responses on decadal to millennial time-scales (Biskaborn et al, 2021).…”

Diatom responses and geochemical feedbacks to environmental changes at Lake Rauchuagytgyn (Far East Russian Arctic)

“…However, there is yet only sparse information available in the literature addressing the contribution of aquatic bioproduction, i.e. diatom primary producers, to accumulation rates of organic matter over different climate stages (Biskaborn et al, 2021b).…”