Beschreibung: Subfossil Cladocera were sampled and examined from the surface sediments of 35 thermokarst lakes along a temperature gradient crossing the tree line in the Anabar-river basin in northwestern Yakutia, northeastern Siberia. The lakes were distributed through three environmental zones: typical tundra, southern tundra and forest tundra. All lakes were situated within the continuous permafrost zone. Our investigation showed that the cladoceran communities in the lakes of the Anabar region are diverse and abundant, as reflected by taxonomic richness, and high diversity and evenness indices (H = 1.89 ± 0.51; I = 0.8 ± 0.18). CONISS cluster analysis indicated that the cladoceran communities in the three ecological zones (typical tundra, southern tundra and forest-tundra) differed in their taxonomic composition and structure. Differences in the cladoceran assemblages were related to limnological features and geographical position, vegetation type, climate and water chemistry. The constrained redundancy analysis indicated that TJuly, water depth and both sulphate (SO4 2−) and silica (Si4+) concentrations significantly (p ≤ 0.05) explained variance in the cladoceran assemblage. TJuly featured the highest percentage (17.4 %) of explained variance in the distribution of subfossil Cladocera. One of the most significant changes in the structure of the cladoceran communities in the investigated transect was the replacement of closely related species along the latitudinal and vegetation gradient. The results demonstrate the potential for a regional cladoceran-based temperature model for the Arctic regions of Russia, and for and Yakutia in particular.

Beschreibung: Permafrost records, accessible at outcrops along the coast of Oyogos Yar at the Dmitry Laptev Strait, NE-Siberia, provide unique insights into the environmental history of Western Beringia during the Last Interglacial. The remains of terrestrial and freshwater organisms, including plants, coleopterans, chironomids, cladocerans, ostracods and molluscs, have been preserved in the frozen deposits of a shallow paleo-lake and indicate a boreal climate at the present-day arctic mainland coast during the Last Interglacial. Terrestrial beetle and plant remains suggest the former existence of open forest-tundra with larch (Larix dahurica), tree alder (Alnus incana), birch and alder shrubs (Duschekia fruticosa, Betula fruticosa, Betula divaricata, Betula nana), interspersed with patches of steppe and meadows. Consequently, the tree line was shifted to at least 270 km north of its current position. Aquatic organisms, such as chironomids, cladocerans, ostracods, molluscs and hydrophytes, indicate the formation of a shallow lake as the result of thermokarst processes. Steppe plants and beetles suggest low net precipitation. Littoral pioneer plants and chironomids indicate intense lake level fluctuations due to high evaporation. Many of the organisms are thermophilous, indicating a mean air temperature of the warmest month that was greater than 13 °C, which is above the minimum requirements for tree growth. These temperatures are in contrast to the modern values of less than 4 °C in the study area. The terrestrial and freshwater organism remains were found at a coastal exposure that was only 3.5 m above sea level and in a position where they should have been under sea during the Last Interglacial when the global sea level was 6–10 m higher than the current levels. The results suggest that during the last warm stage, the site was inland, and its modern coastal situation is the result of tectonic subsidence.

Beschreibung: The sediment succession of Lake Imandra in the central Kola region was investigated by a hydro-acoustic survey followed by sediment coring of site Co1410 (67°42'56.76"N, 33°5'6.42"E) down to the acoustic basement. We reconstructed the environmental history of Lake Imandra after the last deglaciation based on physical, biogeochemical, sedimentological, granulometrical, and micropalaeontological proxies. Our findings reveal the timing of the onset of lacustrine sediment deposition in the lake basin during the Late Glacial and the variability of climatic signals throughout the Holocene. All datasets comprise a depth and age column and: 1. S = Sulfur (%); TOC = Total Organic Content (%); TOC/TN = Total Organic Content / Total Nitrogen; Water Content (%); Grain Size d50 (µm); EM1 =Endmember 1 (%); EM2 =Endmember 2 (%); EM3 = Endmember 3 (%) 2. Acroperus harpae; Alona affinis; Alona guttata/Coronatella rectangula; Alona intermedia; Alona quadrangularis; Alona rustica; Alonella excisa; Alonella exigua; Alonella nana; Alonopsis elongata; Bosmina (Bosmina) longirostris; Bosmina (Eubosmina) cf. longispina/cf. coregoni; Chydorus cf. sphaericus; Daphnia longispina agg.; Eurycercus sp. Leptodora kindtii; Monospilus dispar; Paralona pigra; Pleuroxus truncatus; Rhynchotalona falcata; Planktonic; Littoral-benthic ; (%) Acroperus harpae; (%) Alona affinis; (%) Alona guttata/Coronatella rectangula; (%) Alona intermedia; (%) Alona quadrangularis; (%) Alona rustica; (%) Alonella excisa; (%) Alonella exigua; (%) Alonella nana; (%) Alonopsis elongata; (%) Bosmina (Bosmina) longirostris; (%) Bosmina (Eubosmina) cf. longispina/cf. coregoni; (%) Chydorus cf. sphaericus; (%) Daphnia longispina agg.; (%) Eurycercus sp.; (%) Leptodora kindtii; (%) Monospilus dispar; (%) Paralona pigra; (%) Pleuroxus truncatus; (%) Rhynchotalona falcata 3. magnetic susceptibility (SI * 10^-5) 4. Pinus(%); Artemisia (%); Total Pollen Concentration /1000; AP/NAP; Arboreale Pollen (%); Non-Arboreale Pollen (%) 5. Zr/Rb (log); Rb/Sr; Zr/Al; K/Al; Ti (cps); Ti/Al; Si (cps); Si/Ti; Br/Al; Fe (cps); Fe/Mn

Beschreibung: Subfossil Cladocera remains were examined from small thermorkarst Lake 17-PE-03 (68.183967 N, 53.808247 E, Pechora Delta, Nenets Autonomous Region, Russia) from one core (48 cm-long). Results of the analysis are presented in date base. For the first time, the species Phreatalona protzi (Hartwig, 1900) (Crustacea: Cladocera) has been found in the Nenets Autonomous Region, Russia.

Beschreibung: 25 samples from the lake Bayan Nuur sediment core ( BN2016-1) bottom sediments were processed for diatom analysis in the range from 0 to 110.4 cm (Appendix 2). The samples of sediments were treated using the water bath method. We used high refracting Naphrax resin for the preparation of slides. The species were identified by key books. The valves were counted by parallel transects up to 300 pieces in a sample, using a light microscope and immersion oil. The total number of valves was considered to be 100%. Dominant species were defined as those which accounted for 10% of the total amount or more; subdominants were species which accounted for 5–10%. The pH and total phosphorus (µg/l) values were reconstructed using the European diatom algae database. The trophic status was assessed according to the reconstructed value of total phosphorus. Biogeographical and ecological characteristics of the taxa concerning preferences of habitat, pH, water salinity, geographical distribution were described following Van Dam et al. (1994, doi:10.1007/BF02334251) and Barinova et al. (2006).

Beschreibung: Diatoms are good indicators of a variety of lake water conditions including salinity, pH, light availability, temperature and nutrient levels, but diatoms as palaeoindicators are poorly studied in the Lake Shira. Our research on the species composition and ecological parameters of diatoms provide additional data for the regional databases and contributes to improving the accuracy of paleoecological reconstructions. In this study the diatom results of analysis a 528 cm long continuous sediments core from the Lake Shira (Khakassia, Russia) are presented. The core was collected in August 2020 from central part of the lake from a depth of 24 m. 39 samples were investigated by us for diatom analysis. Diatoms were found only in 13 samples. Diatom analysis of samples revealed 30 taxa, belonging to 19 genera. The analysis of the ecological structure of the diatom flora of the sediment core sample from the lake under study shows that it is dominated by the cosmopolitan representatives of benthic and planktonic-benthic, indifferent to salinity and halophiles organisms giving preference to the alkaline environmental conditions. The prevalence of Handmannia comta (Ehrenberg) Kociolek & Khursevich diatom in sediments have been established.