Monitoring of the polygonal reservoir of the Kytalyk reserve (Indigirka river)

Diatom analysis is one of the methods of paleolimnological research, with the help of which it is possible to determine the state and development of aquatic ecosystems in the past and present. Assessment of the current state of reservoirs is of great importance in paleolimnology, it will allow to obtain results about temperature regime, mineralization, pH environment and water quality. The research area is a region with a lot of small polygonal reservoirs that react quickly enough to external environmental changes that are formed during the cracking of re-vein ice and may form large reservoirs in the future. In this work, the IP-1 monitoring reservoir of the Kytalyk locality was studied for 10 days (every three days) during the expedition work carried out in 2011 using standard methods and a set of field equipment. The material of the study was phytoplankton samples, as a result of which the taxonomic composition of the diatom flora was investigated and the water quality of the Kytalyk monitoring site located in the basin of the Berelyakh river, the left tributary of the Indigirka, was determined

Dendroclimatic studies of Larix cajanderi Mayr. in the Omoloy River Basin

This study presents the results of research on the climatic signal of radial growth of Siberian larch (Larix cajanderi Mayr.) in the Omoloy River Basin, (north-eastYakutia). Tree-ring width chronologies were obtained from three sites  located in the valley complexes of subarctic tundra and forest-tundra ecotone, with chronologies spanning up to 498 years. Comparative analysis of radial growth dynamics and its statistical parameters indicated similar variability patterns within the study region. Dendroclimatic analysis revealed that the primary limiting factor determining the magnitude of radial growth in Siberianlarch is the air temperature during the first half of the growing season. Increasing temperatures have led to an increased role of precipitation and changes in the strength of growth-temperature correlations, especially in northern sites.This study highlights the potential for dendroclimatic and dendroecological researchin northern Yakutia.</jats:p

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‰)

Late Holocene thermokarst variability inferred from diatoms in a lake sediment record from the Lena Delta, Siberian Arctic

Thermokarst lakes in the Siberian Arctic contain sediment archives that can be used for paleoenvironmental inference. Until now, however, there has been no study from the inner Lena River Delta with a focus on diatoms. The objective of this study was to investigate how the diatom community in a thermokarst lake responded to past limnogeological changes and what specific factors drove variations in the diatom assemblage. We analysed fossil diatom species, organic content, grain-size distribution and elemental composition in a sediment core retrieved in 2009 from a shallow thermokarst lake in the Arga Complex, western Lena River Delta. The core contains a 3,000-year record of sediment accumulation. Shifts in the predominantly benthic and epiphytic diatom species composition parallel changes in sediment characteristics. Paleoenvironmental and limnogeological development, inferred from multiple biological and sedimentological variables, are discussed in the context of four diatom zones, and indicate a strong relation between changes in the diatom assemblage and thermokarst processes. We conclude that limnogeological and thermokarst processes such as lake drainage, rather than direct climate forcing, were the main factors that altered the aquatic ecosystem by influencing, for example, habitat availability, hydrochemistry, and water level

Siberian larch forests and the ion content of thaw-lakes form a geochemically functional entity

Siberian larch forests growing on shallow permafrost soils have not, until now, been considered as controlling the abiotic and biotic characteristics of the vast number of thaw-lake ecosystems. We show, using four independent data-sets (a modern data-set from 201 lakes from tundra to taiga, and three lake-core records), that lake-water geochemistry in Yakutia is highly correlated with vegetation. Alkalinity increases with catchment forest density. We postulate that in this arid area, higher evapotranspiration in larch forests compared to tundra vegetation leads to local salt accumulation in soils. Solutes are transported to nearby thaw-lakes during rain-events and snow-melt, but are not fully transported into rivers because there is no continuous groundwater-flow within permafrost soils. This implies that potentially large shifts in the chemical characteristics of aquatic ecosystems to known warming are absent because of the slow response of catchment forests to climate change