Cladocera Analysis Research Articles

Fossil cladoceran record from Lake Beloe in the Altai region (Western Siberia) during the late Holocene

An analysis of subfossil Cladocera in a 193-cm sediment core from Lake Beloe (Altai region) was conducted to trace the history of limnological conditions in the lake over the past 4600 years. Currently, a total of 34 Cladocera taxa were identified in the taphocenosis. The greatest cladoceran species richness was observed among littoral forms of Cladocera, reflecting the presence of shallow areas overgrown with macrophytes. The highest concentration of cladoceran remains was observed in the lower horizons of the core (150-191 cm, 3600-4600 cal yr BP). In this zone, the highest values of Hill indices are recorded, indicating high taxonomic diversity in the community. At a depth of 141 cm (3500 cal yr BP), significant changes in community structure occur, with Chydorus cf. sphaericus beginning to dominate. Taxonomic diversity of Cladocera noticeably increases in the upper part of the core.

Paleoecological reconstruction of water level changes in a cascade of lakes on Lunkulansaari Island (Lake Ladoga) based on the analysis of Cladocera remains in lake sediments

In this study we investigate the dynamics of Cladocera subfossil assemblages (taphocoenoses) during the formation of the cascade of three lakes located on the island of Lunkulansaari in the northeastern part of Lake Ladoga in the late Holocene. Since the last regression of Lake Ladoga and the formation of the lake cascade, Cladocera subfossil assemblages began to accumulate in bottom sediments. Their species structure was alternately dominated by species typical for aquatic vegetation in the littoral zone or species that prefer to live in open water. The data obtained allowed to reconstruct changes in lakes’ water levels and clarify the stages of their development, previously revealed on the basis of pollen spectra of aquatic vegetation.

Late-Weichselian (Vistulian) environmental changes in NE Poland – Evidence from Lake Suchar Wielki

By applying pollen and subfossil Cladocera analyses to the Late-Weichselian section of the sediment profile from Lake Suchar Wielki, we aimed to track paleoenvironmental changes in NE Poland, locally (lake formation and its early development) and regionally (terrestrial plant succession). The article aims to indicate how not only stadial-interstadial changes were noticeable in the study area, but above all even short-term climatic fluctuations.The obtained record covers the period of ca. 13,400–11,500 cal. BP, i.e. the part of the Allerød interstadial (GI-1c1 to GI-1a), the Younger Dryas stadial (GS-1), and the very beginning of the Holocene. During the Allerød, a short-lasting cooling was recognized (the Gerzensee oscillation, GI-1b). It is the first study for this part of Poland evidencing the inter-Allerød cooling by the Cladocera-based mean July temperature reconstruction. In the palynological record it was reflected in an increased temporary share of Betula alba t. pollen, while in the Cladocera record in the appearance of cold-water taxa and low total abundance. At the transition to the Younger Dryas further cooling took place that was evidenced by the increase in the proportion of herbaceous plants together with a distinct decrease of tree pollen concentration in sediments as well as by important changes in Cladocera communities including reduced species diversity, disappearance of more demanding temperate taxa and the expansion of cold-tolerant species. The palaeobotanical record revealed that the proportion of juniper pollen in the studied area was lower than in other regions of NE Poland. A case study demonstrated this was mainly due to local conditions. Moreover, it is noteworthy that, at the end of the Younger Dryas, spruce appeared temporarily in local forest stands. The results of the study suggest climate change, which has also been recorded in ice cores from Greenland as cooling ca. 11,800–11,600 cal. BP.

Cladocera Responses to the Climate-Forced Abrupt Environmental Changes Related to the Late Glacial/Holocene Transition

This article aims to trace in detail the periods of rapid changes during the Late Glacial period based on a subfossil Cladocera analysis and a palynological, geochemical, and statistical analysis. At the end of the Older Dryas, the water level in the reservoir was low, with quite cold waters and inconvenient conditions for developing Cladocera-dominated cold-tolerant species. The beginning of the Alleröd is marked by increasing vegetation density and a rising water temperature, with favorable conditions for developing rare species. At its end, there was a large diversity of species, along with the quite deep and rather mesotrophic nature of the water body. The beginning of the Younger Dryas is a shift back to conditions similar to those noticed during the Older Dryas. The shift to Holocene is manifested by a rapid increase in the number of species and abundance of planktonic forms that appeared before the Holocene onset. The high resolution of the research (1 cm sampling) allowed us to set up more precisely the boundaries between the stadials and interstadials of the Late Glacial and to find some species which were found in the sediment earlier than in previous studies.

Complete mitochondrial genome of Ovalona pulchella (Branchiopoda, Cladocera) as the first representative in the family Chydoridae: Gene rearrangements and phylogenetic analysis of Cladocera.

Chydoridae are phytophilic-benthic microcrustaceans that make up a significant proportion of species diversity and play an important role in the littoral zone of freshwater ecosystems worldwide. Here, we provide the complete mitochondrial genome of Ovalona pulchella (King, 1853), determined by next-generation sequencing. The entire mitochondrial genome is 15,362bp in length; this is the first sequenced mitochondrial genome in the family Chydoridae. The base composition and codon usage were typical of Cladocera species. The mitochondrial gene arrangement (37 genes) was not consistent with that of other Branchiopoda. Both maximum likelihood and Bayesian analyses supported each suborder and family of Branchiopoda as monophyletic groups. The relationships among the families were as follows: [(Leptestheriidae+Limnadiidae) + (Sididae + (Bosminidae + (Chydoridae+Daphniidae)))]+Triopsidae. The newly sequenced O. pulchella was most closely related to the family Daphniidae. The complete mitochondrial genome of O. pulchella also provides valuable molecular information for further analysis of the phylogeny of the Chydoridae and the taxonomic status of the Branchiopoda.

The environmental context of Early Neolithic cultural transformation in the Targowisko settlement region

The aim of this article is to provide information on environmental changes in the Targowisko region in the Early Neolithic as a natural response to settlement and economic activity of the human population in that area. The discussion is based on lithological, geochemical, and palynological analyses, as well as the analysis of Cladocera within strata inside the TRG (Targowisko) core, located in a small wetland in the immediate vicinity of the eastern edge of the Neolithic settlement in the Targowisko region. Settlement analysis points to the absence of stable microregions and to the mobility of human groups. This is confirmed by the sequence of settlement episodes and economic activity, reflected in the stratigraphy of the core sediments, where episodes of significant human interference are followed by phases of almost complete regeneration of the environment. No differences have been noticed between the Linienbandkeramik and Malice culture communities as regards their impact on the environment.

Small peatland with a big story: 600-year paleoecological and historical data from a kettle-hole peatland in Western Russia

Peatlands are important records of past environmental changes. Based on a multiproxy analysis, the main factors influencing the evolution of a peatland can be divided into autogenic and allogenic. Among the important allogenic factors, apart from climate change, are deforestation and drainage, which are directly associated with human impact. Numerous consequences arise from these processes, the most important of which are physical and chemical denudation in the catchment and the related hydrological disturbances in the catchment and peatland. The present study determined how human activities and the past climatic variability mutually influenced the development of a small peatland ecosystem. The main goals of the study were: (1) to trace the local changes of the peatland history over the past 600 years, (2) to investigate their relationship with changes in regional hydroclimate patterns, and (3) to estimate the sensitivity of a small peatland to natural and human impact. Our reconstructions were based on a multiproxy analysis, including the analysis of pollen, macrofossils, Chironomidae, Cladocera, and testate amoebae. Our results showed that, depending on the changes in water level, the history of peatland can be divided into three phases as follows: 1/the phase of stable natural conditions, 2/phase of weak changes, and 3/phase of significant changes in the catchment. Additionally, to better understand the importance of the size of catchment and the size of the depositional basin in the evolution of the studied peatland ecosystem, we compared data from two peatlands – large and small – located close to each other. The results of our study indicated that “size matters,” and that larger peatlands are much more resilient and resistant to rapid changes occurring in the direct catchment due to human activities, whereas small peatlands are more sensitive and perfect as archives of environmental changes.

Eemian (MIS 5e) climate oscillations based on palaeobotanical analysis from the Beckentin profile (NE Germany)

Climate instability in the Eemian Interglacial is gaining more and more evidence. One of such oscillations in the Beckentin record is indicated by the disappearance of the Cladocera and changes in macroremains at the beginning of E4a (Corylus phase). They confirm the shallowing of the reservoir, probably caused by climate changes, but not reflected in the palynological record. However, a significant oscillation observed in the first half of the E5 (Carpinus phase), ~5860 years after the boreal forests subsided and ~6290 years after the onset of interglacial forestation, suggests that, although not being an analogue of the OHO (Older Holsteinian Oscillations) in MIS 11c and the 8.2 ka cold event in the Holocene, it is very similar to these oscillations. The Eemian oscillation was noted also in the Bispingen profile in northern Germany, ~6500 years after the interglacial forestation. However, the course of vegetation changes there differs from that in Beckentin. The analysis of macroremains and Cladocera confirms the disappearance of rush and water vegetation in the water reservoir at that time in Beckentin. These results confirm that numerous climatic oscillations could have occurred in the Eemian Interglacial.

A methodological proposal for the analysis of Cladocera (Crustacea, Branchiopoda) subfossils from sediments of temporary aquatic ecosystems.

The main objective of the present study was to promote some adaptations to the standard methodology used in the analysis of Cladocera subfossils. The samples used in this study were collected at Lagoa dos Coutos, a temporary lake located on an outcrop with iron-rich duricrust in the Serra do Gandarela (Minas Gerais, Brazil). The sediment from this pond, typical of temporary ecosystems in the region, is characterized by rigid concretions that are difficult to dissolve in aqueous media, making it difficult to visualize and analyze subfossils taxa. Sediment samples were prepared according to the standard methodology used in paleolimological studies and the methodological adaptations proposed in the present study, which included the addition of 1 mg of Kochia scoparia, a palynological marker used to estimate subfossil density, as well as the addition of hydrofluoric acid (HF) to oxidize silicate materials. The samples prepared according to the new methodological procedure improved Cladocera subfossil visualization, facilitating the taxonomic analysis of the species. The samples submitted to the standard methodological procedure had a significantly higher mean of sediment particles (mean of 84.2 sediment particles) and 70% more residues compared to the samples prepared with the newly proposed methodology (mean of 22.1 sediment particles). Absolute data on the temporal variation of the density of Cladocera subfossils was obtained by using the palinological marker K. scoparia, which showed higher densities of subfossils in more recent, humid periods (112,000 subfossils/cm3 at 5 cm, equivalent to 3,500 years BP). The results indicate that the new methodology can contribute to advances in paleolimnological studies of temporary aquatic ecosystems, whose lake histories are rarely investigated, despite their ecological relevance as ecosystems that indicate environmental and climatic changes.

Effects of environmental change on subfossil Cladocera in the subtropical shallow freshwater East Taihu Lake, China

East Taihu Lake (the south-eastern portion of Taihu Lake in China) suffers from eutrophication. The study of lacustrine subfossil zooplankton assemblages can be used to reconstruct the long-term evolution of lake water environments. In particular, the analysis of subfossil Cladocera can indicate historical changes in aquaticplants, water level, trophic states, and human disturbance in lakes. In this study, we correlated downcores changes in cladoceran assemblages with several geochemical proxies to identify the response of Cladocera to environmental change in East Taihu Lake over the past one hundred years. Redundancy analysis (RDA) and Pearson correlation analysis identified significant correlations between total phosphorus (TP) and Bosmina spp. (total), B. (E.) longispina, and Chydorus cf. sphaericus (correlation coefficients: −0.720 (P < 0.01), −0.646, and 0.667 (P < 0.05), respectively). We observed decreasing abundances of subfossil Bosminidae and increases in littoral cladoceran species and TP after the 1960s, coinciding with the introduction of land reclamation for fish and crab farming. These anthropogenic pressures exacerbated eutrophication, which led to the rapid growth of submerged vegetation and subsequently altered the zooplankton assemblage.

Bottom-Up Forces Drive Increases in the Abundance of Large Daphnids in Four Small Lakes Stocked with Rainbow Trout (Oncorhynchus mykiss), Interior British Columbia, Canada

The introduction of salmonids into lakes of western North America for sport fishing is a widespread phenomenon. While numerous investigations have documented cascading trophic interactions upon the introduction of fish into naturally fishless systems, little research has been done to investigate the importance of natural fish status (fishless vs. fish bearing) in modulating historical food web response to dual forcing by bottom-up (resource regulation from nutrients) and top-down (planktivory from stocked fish) processes. We used the paleolimnological record to reconstruct food web changes in four lakes in interior British Columbia that have been stocked with rainbow trout since the early to mid-1900s. Analysis of pigments, diatoms, and Cladocera was undertaken in cores from all lakes. We predicted that if fish were important in structuring cladoceran abundance and composition, we would document a decline in the abundance of large daphnids post-stocking in our two naturally fishless lakes, and little change in the two fish-bearing lakes. Instead, we documented increased abundance of large daphnids after stocking in all lakes in the early to mid-1900s, a finding inconsistent with size-selective predation from planktivorous fish. Further, our data suggest that deep, low-oxygen refugia may be important in sustaining populations of large Daphnia, a process which was enhanced by increased nutrients and lake production according to sub-fossil diatom and pigment analyses. This study shows that fish stocking does not invariably result in a decrease in large-bodied Cladocera and that nutrients and lake type can modulate the response of invertebrate planktivores.

Late Glacial palaeoenvironmental changes in the southern part of the Holy Cross Mountains based on the “Białe Ługi” peatland record

This paper presents the Late Glacial stage of the development of the Białe Ługi peatland in the southern Holy Cross Mountains, based on a comprehensive palaeoenvironmental data. A complex analysis of palynology, Cladocera, sed imentology, geochemistry and 14C dating were used. Organic deposition was initiated during the Oldest Dryas. The sedimentary record of the aquatic and terrestrial ecosystems reflects considerable difference between cooler (Oldest, Older and Younger Dryas) and warmer phases (Břlling and Allerřd). Periods of intensified interaction between aeolian processes and peatland are related to stages of disappearing vegetation and changes in aquatic invertebrate communities. We therefore suggest that peatlands were created as a result of local lithological-structural, tectonic, hydrogeological and morphological conditions, and the peatland development rate was largely influenced by changing climatic conditions, which determined local vegetation development, intensity of denudation processes and water level changes. The results validate significance of selection and use of several methods, as well as value of biogenic deposits from the Białe Ługi peatland as archives of past climate change in the Małopolska Upland. Relatively stable water conditions and uninter rupted biogenic sedimentation in the Late Glacial that were provided by the geological structure and relief suggest the studied peatland is a leading one in the region.

Postglacial evolution of a small lake in the South Baltic coastal zone based on geochemical, pollen and subfossil Cladocera analysis

Abstract The paper presents sedimentary records acquired as part of the research on the coastal cliff located between 221.3 and 221.4 km of the Slovincian (Słowinskie) Coast near Debina. Palynological and subfossil Cladocera analysis of sediments combined with geochemical data proves the existence of varying environmental conditions that occurred depending on the climate fluctuation. The Debina reservoir was formed in the Late Glacial period. Mud and gyttja were deposited in an initially cold proglacial lake. Species of Cladocera identified in this period indicate a deeper oligotrophic reservoir. The end of the Late Glacial cooling inhibited the development of fauna in the reservoir. Climate change at the beginning of the Holocene improved the habitat conditions in the Debina paleolake, which is reflected in the growth of zooplankton biodiversity and enrichment of the aquatic pollen content. We distinguished three phases that illustrate the evolution of the studied aquatic-mire ecosystem. In the following periods, the trophic level in the reservoir increased and significant water-level fluctuations led to periodic transformations of reservoirs into peat bogs. Gradually, the water-level lowering and the intensification of eolian processes led to terrestrialization of the paleolake.

Holocene climate vs. catchment forcing on a shallow, eutrophic lake in eastern Poland

This paper presents a sedimentary record from Lake Łukie located in the southeastern part of the Central European Plain, beyond the reach of the maximum extent of the last glaciation. The lake has thermokarstic origin and developed during the last glacial termination due to subsidence of the sub‐Quaternary carbonate basement triggered by permafrost thawing. A sediment core was investigated to reconstruct water trophic state and lake depth changes during the Holocene. We aimed at showing the relationship between ecological and geochemical changes in the lake and regional/supraregional climatic and hydrological trends throughout the Holocene. Results of subfossil Cladocera analysis were combined with data on the geochemistry and stable C and O isotopes in sedimentary carbonates. Isotopic and geochemical proxies helped to detect sources of sedimentary particles in the lake and thus to reconstruct changes in the intensity of atmospheric and catchment processes (e.g. precipitation and surface runoff). The Cladocera analysis results indicated endogenic processes in the lake such as trophic changes. Our data revealed that Lake Łukie has always been a rather eutrophic water body and the periods of particularly high productivity were in the lower Preboreal and upper Subatlantic. Periods of increased water depth were recorded in the lower Preboreal, lower Boreal and upper Subboreal, whereas low water stands were obtained during the late Preboreal, late Boreal, late Atlantic and Atlantic/Subboreal transition as well as during the lower Subboreal. The sediment succession from Lake Łukie provides the first full Holocene record of carbon and oxygen stable isotopes in lacustrine carbonates from the eastern part of the Central European Lowland. The record is characterized by uncommonly high δ13C and δ18O values of the carbonates resulting from a combination of within‐lake processes and dissolution of the carbonate bedrock of Cretaceous age. The impact of the old carbonates on isotope values was helpful in the reconstruction of the catchment forcing on the lake.

Reaction of the lake environment to the Holocene warming depending on the distance to the maximum extent of the Vistulian ice sheet

This study presents 1) the results of a stable isotope and subfossil Cladocera analyses of lacustrine sediments from Maliszewskie Lake (E Poland) and next 2) different reaction of the lake environments depending on the lake's localization. Maliszewskie Lake is located in North Podlasie Lowland ca. 30 km to the south of the Vistulian ice sheet limit. The approximately 4.80-m-thick sediments (Maliszewo I profile) are mainly comprised of calcareous gyttja covered by peat and organic detritus gyttja. Pollen analysis documents that the sediments accumulated from the Late Glacial (Allerød period) to recent times. Based on the results of stable isotope and subfossil Cladocera analyses of sediments, the lake environmental changes were reconstructed. A positive trend in δ18O and δ13C values documents a gradual climatic warming. The fluctuations of the oxygen isotopic values suggest the multiple oscillation of water level due to a change in the evaporation/precipitation ratio. The subfossil cladoceran fauna in the Maliszewo I profile is represented by 21 species belonging to five families. Three zones of Cladocera development were distinguished. The Cladocera species indicate the initial oligotrophic status of the lake and its subsequent increase of trophic status. Currently, Maliszewskie Lake is a very shallow, declining reservoir. The initial period of its existence probably saw its maximal depth. In presented studies we compared our results with data from three other sites documenting the reaction of the lake environment during the Late Glacial and Holocene transformation. At that time we observed different reactions to the climate amelioration. In the northern, postglacial lakes, the Holocene warming at first provoked an input cold melting water characterized by more negative oxygen isotope values and then a rise in water temperature. In the lakes further away from the glaciation border (periglacial lakes), the increase in water temperature, documented by e.g. more positive oxygen isotopic immediately occurred. The climate warming is commonly manifested by a significant increase of number of species and individuals of Cladocera.

The record of postglacial environmental changes of the southern Baltic coastal zone in the sequence of fossil soils

PurposeThe studies aimed to reconstruct major phases of litho-morpho-pedogenic processes and past environmental changes in the Baltic coastal zone near Poddąbie (54°37,070′ N, 16°57,897′ E) based on physical, chemical, pollen, and fossil Cladocera analysis of the polycyclic pedocomplex.Materials and methodsThe polycyclic pedocomplex under study included seven fossil soils developed from the Early Holocene until modern times from various materials. The soils were sampled and analyzed using standard procedures in soil science to determine their physical and chemical properties. Pollen and fossil Cladocera analysis was also carried out in the examined profile. Radiocarbon dates of selected samples were also specified.Results and discussionThe studied polycyclic pedocomplex has been developed from materials of varied origin, including glaciofluvial, fluvial, aeolian, and biogenic deposits of the lake. According to the results of pollen and fossil Cladocera analysis and radiocarbon dating, this body of water has evolved from the beginning of Preboreal period to the half of Boreal. The studied soils represent various reference groups and advancement of development. They constitute relics of former geomorphological and soil-forming processes, which have taken place over the last 9500 years, including periglacial processes, wildfires, Baltic Sea shoreline changes, and aeolian activity. The last stage of the coastal relief dynamics was conditioned by the fire which took place about 1472–1637 AD. The lack of plant cover and intensive abrasion due to direct vicinity of the coastline has caused the deposition of aeolian material, which is the parent material of nutrient-poor initial soils.ConclusionsThe analysis of fossil soil development with the use of specialized research methods allowed for reconstructing the dynamics of past geomorphological processes and natural environment changes in the study area. The studied polycyclic pedocomplex constitutes a record of environmental changes taking place in the central part of the Polish Baltic coastal zone from the Early Holocene to the present day. The studied soil sequence is located within a land depression developed in place of the former water reservoir created as a result of permafrost degradation, and filled with Holocene deposits.

The rare Holsteinian (Mazovian) interglacial limnic deposits in the Książnica outcrop at Krzczonów (near Świdnica), Sudetic Foreland

The article presents the results of research on peats, muds and sands filling a palaeocavity within alluvial fans of the Bystrzyca River valley, in the Sudetic Foreland of SW Poland. In the 534-cm deep research profile in the central part of a palaeolake, 267 samples were collected at an interval of 2 cm and lithologically (structural and textural studies), palaeobotanically (studies of diatoms, pollen plant macrofossils and fossil wood), palaeozoologically (Cladocera, Mollusca and Ostracoda), geochemically (chemical elements and isotopes) and palaeomagnetically analyzed.The profile consists of three parts: organic with mineral layers (lower), mineral (middle), and organic (upper). The palynological diagram was divided into three zones that represent local sets of pollen zones. This diagram, although incomplete, is clearly indicative of the younger part of the Holsteinian (Mazovian: pollen III and IV periods interglacial). The upper part of the diagram consists of four local pollen zones that are correlated with stadial and interstadial periods. Analysis of several samples of fossil wood shows the widespread presence of Pinus remains and numerous fragments of rhytidome (bark) of Betula. Development of the peat layer (1.36–0.68 m depth) started with paludification of the forest with the Betula forest. Analysis of Cladocera shows the presence of chitin armor components (species: Chydorus sphaericus, Alona rectangula and ephippia of Alona rectangula) in three samples.Lithological, Cladocera and palaeo-magnetic research, supported by geochemical studies, indicate the existence of at least three main phases. The lake originated during the younger part of the Holsteinian (Mazovian) Intergalcial as an oxbow within the valley, where the deposition of variously thick (up to 1.5 m depth) peats, organic and minerogenic silts (the first stage). In the second phase, a closed, fairly deep late Holsteinian lake continued to exist under relatively warm conditions with mainly mineral deposition from the slope. The lake became shallower and wider, and then more open and better oxygenated (with through-flow). In the final phase the lake was completely filled by organic sediments under interglacial conditions. The absence of diatom, molluscan and ostracod communities indicates an acid lacustrine environment at this time. The fluvial and limnic deposits are sealed by overlaying Saalian (Odranian) till.

Reconstruction of the history of a thermokarst lake in the Mid-Holocene based on an analysis of subfossil Cladocera (Siberia, Central Yakutia)

This paper presents the results of a cladoceran analysis of a sediment core with a lenght of 382 cm collected from a pingo in alas Khara Bulgunnyakh located in Central Yakutia. Based on the Cladocera analysis results, the formation of the lake had started during the Holocene climatic optimum ~6600 cal. yrs. BP. The analysis of changes in the species composition of subfossil cladoceran communities made it possible to identify, on the basis of cluster analysis, four statistically significant ecological zones. The period of optimal conditions for the Cladocera community is defined by a complex evened community structure and numerous cladoceran remains in the sediments accumulated between 6500 and 6000 cal. yrs. BP. The history of the thermokarst water body development and existence reconstructed on the basis of the subfossil cladoceran analysis was rapid and short.

Late Pleistocene and Holocene environmental evolution of the Wkra River Valley near Bielawy Gołuskie (central Poland) recorded in palaeo-oxbow lake deposits

This study aimed to reconstruct environmental changes in the Wkra River Valley near Bielawy Goluskie (central Poland) based on geochemical, palynological and subfossil Cladocera analysis of deposits filling a palaeo-oxbow lake. Two sediment boreholes collected from the palaeochannel bend (BG-1) and neck (BG-2) include full sequences of organic deposits lying on clastic deposits. The lower part of the BG-1 borehole contains gyttja that accumulated during the Younger Dryas and the Preboreal, which is covered by reed peat of Preboreal and Boreal age. On top of this is alder peat that accumulated during the Atlantic. The ages of the gyttja and peat were confirmed by both radiocarbon dating and palynological analysis. The peats are characterized by a significant content of organic matter, which is relatively stable over time. This indicates a low intensity of mechanical denudation in the catchment, which is supported by low concentrations of aluminum and potassium. Calcium values greatly exceed these elements, suggesting that the lake was mainly fed by groundwater. Variation in trophic conditions over time is indicated by a vertical variability in the content of nitrogen, as well as by the Cladocera population. The strong decomposition of peat in the top layer of the mire, and increased concentrations of phosphorus and heavy metals, testify to increasing human activity during the most recent time periods

Reconstruction of the History of the Thermokarst Lake During the Middle Holocene Based on the Analysis of Subfossil Cladocera (Siberia, Central Yakutia)

Reconstruction of the History of the Thermokarst Lake During the Middle Holocene Based on the Analysis of Subfossil Cladocera (Siberia, Central Yakutia)