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We conducted year-round, monthly monitoring of the stable isotope composition of DIC and water in hypereutrophic Lake Kierskie, western Poland, along with isotope measures of calcite collected in sediment traps installed at 16 and 30 m water depth in the lake. Isotope data were supplemented by previously published data on physico-chemical variables in the lake water column. We sought to determine how carbon and oxygen isotopic disequilibria in calcite deposited in the lake’s laminated sediments vary seasonally, and what factors drive this variability. Deposition of calcite out of equilibrium with DIC and water was documented over the entire study period. For δ18O, the disequilibrium difference between successive months far exceeded the amplitude of the seasonal variability in the isotope composition of water. The biggest difference between the measured and calculated δ13Ccalcite and δ18Ocalcite values was observed during late autumn and winter sediment resuspension and redeposition (2.4‰ and 5.4‰, respectively). In the spring, δ13Ccalcite and δ18Ocalcite offsets from equilibria, 0.5‰ and 1.3‰, respectively, resulted from rapid precipitation of large calcite crystals. During summer, intense productivity and processes related to calcifying algae (“vital effects”) caused lower δ13C (0.5–1.8‰) and δ18O (2.8–2.9‰) in calcite. Differences between isotope values of calcite collected from the two water depths were small, and might have resulted from different settling velocities of small and large crystals, and/or preferential dissolution of smaller grains. We suggest that winter laminae should be excluded from isotope studies of varved sediments whenever possible, as they likely contain redeposited carbonate in which the isotope value is not indicative of conditions in the lake at the time of laminae formation. We also recommend supplementing isotope analysis of calcite in varved lake sediments with seasonally resolved analysis of carbonate content. It appears that major shifts in the proportion of carbonate deposited across seasons can cause notable changes in mean annual values of δ18Ocalcite and δ13Ccalcite, even if DIC and water isotopic compositions remain stable.

In this study, we focus on the environmental changes recorded in the San River valley (Stubno–Naklo site, south-eastern Poland) at the beginning of the Holocene. This multi-proxy study for the first time in the region of the northern foreland of the Western Carpathians included quantitative thermal reconstruction based on Chironomidae and high-stratigraphic resolution of 14C AMS dating. We hypothesised that (i) climate events during the Early Holocene contributed to ecosystem turnovers via stimulating disturbances related to the river's fluvial activity and (ii) woodland and oxbow lake ecosystems became more resilient to flood disturbances along with the advance of forest succession on the floodplain. The results revealed that the response of ecosystems on the Early Holocene warming was strongly linked with the decrease in fluvial activity of the river. The reconstruction of the mean July temperature based on Chironomidae revealed the exceptionally high rate of warming during the period of ca. 11,490–11,460 cal. BP (at least 1 °C per decade) up to values > 2 °C than modern ones. During this period, the lake trophy and productivity started to increase with a simultaneous spread of Betula woodlands on the alluvial plain. The “Preboreal oscillation” cooling was dated at ca. 11,450–11,250 cal. BP. At that time, an increased climate instability led to a higher rate of extremal events such as flood at ca. 11,400–11,330 cal. BP, which probably led to the disruption of the Betula population. The development of riparian woodlands, initiated by the expansion of Ulmus from ca. 11,100 cal. BP, and further spread of Quercus and Fraxinus excelsior on the alluvial plain and lower river terraces increased plant transpiration and therefore limited the river runoff and its fluvial activity. This, together with the expansion of reed belt communities, probably limited the impact of floods on the oxbow lake. However, ca. 10,010–9880 cal. BP traces of higher fluvial activity, but of lower impact, were recorded.

We document the long-term development of a spring-fed fen assessing its sensivity to climate changes over the last ca. 4000 years. Our investigation is based on high-resolution, continuous plant macrofossil remains and mollusc records, complemented by pollen, geochemical analysis and radiocarbon dating of Valea Morii, located in the Feleac Hills (Transylvanian Depression) in NW Romania, Central Eastern Europe. Based on our palaeocological data we have distinguished three stages of wet habitat conditions: two stages between 4000 and 2450 cal yr BP and one in the last 800 cal yr BP, and one dry stage between ca. 2450 and 800 cal yr BP. These local habitat conditions appear to reasonably reflect regional climate characteristics. High-resolution analysis of two replicated cores documented a mostly comparable pattern of local plant and mollusc succession, and stable isotope values from ca. 500 cal yr BP. The appearance of C. mariscus during the last two centuries may be related to increased wetness and associated active CaCO3 precipitation, which allowed this plant to colonise the spring-fed fen studied. However, it can be not excluded that the occurrence and spread of a Cladium mariscus population at this site during the last two centuries might have been partly favoured by the warming of the climate after the Little Ice Age. The potential of carbonate oxygen stable isotope values as an indicator of major trends in climatic change, both temperature and humidity, in mountain spring-fed fen deposits is shown. Carbon isotopes in the carbonates were found to be useful in reconstruction of changes in vegetation, soil development and the dissolution of bedrock carbonates, primarily as a reaction to changes in climate humidity.

This article presents the first multi-proxy study of palaeoecosystem changes during the Late Weichselian and Early Holocene in western Ukraine. The site is a former oxbow lake situated in the Dniester River valley (western Ukraine). We hypothesised that this area may have been one of the nuclei for the Holocene expansion of elm (Ulmus), a primary arboreal taxon in riparian woodlands, in the Central and Eastern European lowlands. Our study was undertaken on a profile encompassing the period ca. 12,900–9880 cal. BP. We applied selected palaeobotanical, palaeozoological and geochemical analyses. During the Younger Dryas the area was dominated by well-developed Pinus sylvestris-Betula woodlands. Drier habitats were overgrown by Juniperus shrublands and steppe communities. Patches of tundra with Betula nana were also present. Ulmus started to spread on the lower river terraces before ca. 11,840 cal. BP i.e., during the late Younger Dryas, which suggests this area as a nucleus for its Holocene expansion. A chironomid-based reconstructed mean July temperature (MJT) of 15–17 °C is suggested during the Younger Dryas. The main Ulmus expansion started ca. 11,160 cal. BP and its optimum in local woodlands lasted until ca. 10,340 cal. BP, when Pinus sylvestris rapidly expanded. The reconstructed MJT varied between 18 and 21 °C during the Ulmus optimum; however, it rapidly declined to 16 °C around ca. 10,800 cal. BP. Fire activity increased before ca. 10,870 cal. BP, concurrent with the climate warming at the Younger Dryas-Holocene transition, but did not affect the population of Ulmus, a taxon intolerant of fires. Wildfires probably affected patches of steppe vegetation and Pinus sylvestris-Betula woodlands occupying higher elevations of the valley and watersheds. However, changes in the fire activity may have stimulated Ulmus retreat at ca. 10,340 cal. BP.

Oxygen (δ18O) and carbon (δ13C) stable isotope analyses are among the standard methods applied in the studies of past environment, including climate. In lacustrine sediments, δ18O and δ13C values can be measured in various carbonates including charophyte encrustations. Application of the stable isotope record of lacustrine carbonates requires knowledge about the possibilities and limitations of the method. Thus, this study presents the oxygen stable isotope composition of carbonate encrustations precipitated by modern charophytes (δ18OCARB) and of ambient waters (δ18OWATER). The study objects were widely distributed and morphologically different charophyte species, large and branchy Chara tomentosa L. and small and slender Chara globularis Thuill. Each species was studied in five lakes located in western Poland, at three sites per lake. The study demonstrated that δ18OCARB values were similar for the two charophyte species and were lake-dependent. δ18OCARB and δ18OWATER relationships were also similar for the studied charophytes with carbonate encrustations 18O-depleted compared to ambient waters. The shift of mean δ18O values between C. tomentosa and C. globularis encrustations and ambient waters, 2‰ and 3.2‰, respectively, was evidenced in all studied lakes which may indicate potential applicability of δ18OCARB of the two species in paleolimnological studies.

This study focuses on the inter- and intra-specific variability in δ13C and δ18O values of shells and opercula of gastropods sampled live from the littoral zone of Lake Lednica, western Poland. The δ13C and δ18O values were measured in individual opercula of Bithynia tentaculata and in shells of Bithynia tentaculata, Gyraulus albus, Gyraulus crista, Lymnaea sp., Physa fontinalis, Radix auricularia, Theodoxus fluviatilis and Valvata cristata. The gastropods selected for the study are among the species most commonly found in European Quaternary lacustrine sediments. The carbon isotope composition of the gastropod shells was species-specific and the same order of species from the most to the least13C-depleted was observed at all sites sampled. Differences in shell δ13C values between species were similar at all sampling sites, thus the factors influencing shell isotopic composition were interpreted as species-specific. The δ18O values of shells were similar in all the species investigated. Significant intra-specific variability in shell δ13C and δ18O values was observed not only within the populations of Lake Lednica, which can be explained by heterogeneity of δ13C DIC, δ18O water and water temperature between the sites where macrophytes with snails attached were sampled, but also between individuals sampled from restricted areas of the lake’s bottom. The latter points to the importance of factors related to the ontogeny of individual gastropods.

Mountainous areas of Central and Eastern Europe were crucial for the survival of temperate deciduous trees during the Weichselian glaciation. The distribution of these tree refugia was one of the key factors for the migration and composition of temperate forests during the Late Glacial and Holocene. In this article, a palaeoenvironmental reconstruction from the landslide palaeolake located within a lower montane zone in the northern part of the Western Carpathians (Beskid Makowski Mountains) is presented. A multiproxy approach, involving several biotic proxies, combined with organic carbon and nitrogen content and their isotopic ratio, supported by high stratigraphic accelerator mass spectrometry (AMS) 14 C dating was applied for the reconstruction of vegetation changes and their influence on the small lake ecosystem. The results revealed that forests dominated by Pinus sylvestris , Betula , and Picea abies , in which Pinus cembra and Larix decidua were an admixture, were present from at least ca. 11,240 cal BP. From ca. 11,130 cal BP, elm ( Ulmus ) started to spread, and ca. 70 (± 30) years later, it probably has become a prominent constituent of the local forests. This process was coincident with an increased fire activity and the retreat of P. cembra and L. decidua . The early spread of Ulmus in the lower mountainous forest ecosystem is an indirect evidence of the presence of its Late Glacial refugia in the Western Carpathians. The lake, functioning during that time, was characterised by high sedimentation rate (0.16–0.2 cm year − 1 ), low primary productivity, low Cladocera diversity mainly dominated by Chydorus sphaericus complex, and low Chironomidae concentration. The spread of aquatic vegetation, among them Potamogeton obtusifolius and Potamogeton friesii , in the lake was simultaneous to Ulmus expansion and the constant presence of P. abies macrofossils.

Here, for the first time in SE Poland, we document the long-term development of a rich fen and assess its sensitivity to climate change and human impacts over the last ca. 3500 years. Our results are based on a high-resolution, continuous plant macrofossil remains, mollusc and pollen record, complemented by geochemical, mineral magnetic and physical characterisation, and radiocarbon dating from Bagno Serebryskie rich fen located in SE Poland. Based on the palaeoecological data we distinguished five stages of wet habitat conditions: 5000–3300, 2800–2150, 1600–1100, 750–230, 150–10 cal yr BP and five dry periods at ca. 3300–2800, 2150–1600, 1100–750, 230–150, 10 to − 64 cal yr BP. The pollen and geochemistry records, particularly Pb, show that the first human activity in the study area occurred ca. 3200 cal yr BP and increased markedly from 500 cal yr BP affecting local plant development including the population size of Cladium mariscus. Our study has shown that despite human impact (drainage, fire), Bagno Serebryskie peatland has hosted rare, presently protected species, such as Cladium mariscus for hundreds of years. We conclude that, in common with ombrotrophic bogs, rich fen ecosystems can provide a reliable source of palaeoclimatic and palaeohydrological data. Our study also shows that a large peatland (376 ha) can be as sensitive a palaeohydrological archive as smaller mires.

The stable carbon isotope composition of the carbonate encrustations (δ13CCARB), organic matter (δ13CORG) and the dissolved inorganic carbon (δ13CDIC) in the ambient lake waters were analysed for two common but morphologically different and, thus, representing different growth forms of Chara species. We hypothesized that the relationships between δ13CCARB, δ13CORG and δ13CDIC are species specific and related to the different growth forms of the studied charophytes. For each species (Chara tomentosa and Chara globularis), 10 individuals and water samples from above the macrophytes were collected in five lakes at three sites per lake in mid-summer. Opposing shifts were found between δ13CCARB and δ13CDIC values with 13C enrichment in C. tomentosa and 13C depletion in C. globularis. In addition, C. globularis exhibited more negative values of δ13CORG than C. tomentosa, even under similar conditions. The δ13CCARB and δ13CORG values were positively correlated in both species, but δ13CCARB and δ13CDIC as well as δ13CORG and δ13CDIC were positively correlated in C. tomentosa only. The differences found result from the different proportions between 13C and 12C in DIC used as a CO2 source for photosynthesis, which is linked to the different growth forms represented by the two studied charophytes and, thus, are species specific as we hypothesized.

Many regions around the world experienced abrupt climate change with far-reaching societal and environmental effects at ca. 4.2 cal. ka BP. As one of the most distinct climatic events of the last 11.7 ka, it has been used to establish the formal boundary between the mid- and late-Holocene. Although the 4.2 ka event was not pronounced in East-Central Europe, its exact impact on the area has yet to be evaluated. The aim of this paper is twofold: (1) to reconstruct the functioning of the selected lake and terrestrial ecosystems from northern Poland around the time of the 4.2 ka event, and (2) to disentangle the drivers of the recorded environmental changes (local factors vs. climate impact). We studied the sedimentary record of Lake Spore, focusing on the period between 3.8 and 4.5 cal. ka BP using numerous biotic and abiotic proxies, such as chironomids, cladocerans, pollen and spores, δ13Corg, δ15Norg, δ18Ocarb, δ13Ccarb, TOC/N, Fe, S, LOI550, and LOI950. The chironomid-derived reconstruction of mean July air temperature did not change during the 4.2 ka event. Pollen accumulation rate (PAR) data showed lower pollen production of some tree taxa during the period 4.0–4.25 cal. ka BP that is consistent with low PARs recorded for the corresponding period in the sediments of nearby (~75 km) Lake Suminko. This change might have occurred due to either regional-scale forest disturbance or cooler winters resulting from an exceptionally strong Siberian High during the 4.2 ka event. Distinct peaks of Fe and δ13Ccarb at 4.2 cal. ka BP likely record a pulse of podzolization. Although soil transformation processes were common in East-Central Europe after ca. 5 cal. ka BP due to general climate cooling, they could have been enhanced at Lake Spore during the 4.2 ka event, if winters were more severe. The δ13Corg, δ15Norg, TOC/N and δ18Ocarb records point to a water level rise after 4.2 cal. ka BP that most likely resulted from soil transformation in the catchment, not a change in effective precipitation. The composition of the terrestrial vegetation and the lake fauna and flora remained largely unaffected by the 4.2 ka event.

High-resolution biological proxies (pollen, macrofossils, Cladocera and diatoms), geochemical data (μ-XRF element scans, TOC, C/N ratios, δ 18 O carb and δ 13 C org values) and a robust chronology based on varve counting, AMS 14 C dating and tephrochronology were applied to reconstruct lake system responses to rapid climatic and environmental changes of the Trzechowskie palaeolake (TRZ; Northern Poland) during the late Allerod – Younger Dryas (YD) transition. Palaeoecological and geochemical data at 5–15 years temporal resolution allowed tracing the dynamics of short-term shifts of the ecosystem triggered by abrupt climate change. The robust age control together with the high-resolution sampling allowed the detection of leads and lags between different proxies to the climate shift at the Allerod-Younger Dryas transition. Our results indicate (1) a water level decrease and an increase in wind activities during the late Allerod and the Allerod-YD transition, which caused intensified erosion in the catchment, (2) a two-decades delayed vegetation response in comparison to the lake depositional system. Comparison with the Lake Meerfelder Maar record revealed slightly different vegetation responses of the Trzechowskie palaeolake at the YD onset.

The aim of this study was to better understand the relations between carbon and oxygen stable isotope values of ambient water, mollusc shells, macrophytes and their carbonate encrustations, commonly used in palaeolimnological studies. Water, molluscs and macrophytes were sampled from the littoral zone in Lake Lednica, NW Poland. The influence of carbon species assimilated during photosynthesis and the net intensity of photosynthesis resulting from the size of charophyte species and the density of their stands were postulated to be the most important factors causing the species-specific δ13C values of charophyte thalli and encrustations. It was suggested that photosynthetic activity of charophytes affected not only the δ13C values of charophyte encrustations but also mollusc shells by changing δ13C values of DIC within charophyte stands. In addition, incorporation of metabolic carbon into the shell was proposed as the main cause of both the 13C depletion of mollusc shells relative to δ13C values of DIC and the species-specific δ13C values of shells. Mollusc shells were precipitated at the isotope equilibrium or close to the equilibrium with δ18O values of lake water. Charophyte encrustations were found to be 18O depleted due to the kinetic isotope effects during intense photosynthesis and thus fast precipitation of the calcite.