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The vicinity of the Rozprza archaeological site (central Poland) has been the area of a series of palaeoecological studies tracking the environmental history of the Luciąża River valley up to ca. 13,200 cal. BP. Numerous subfossil palaeomeanders of different sizes have been discovered in the valley floor. Here, we present the first results of multiproxy research on the paleo-oxbow lake fill, one of the oldest in the region. The wide range of palaeoecological analyses resulted in reconstructions of vegetation history, climatic, hydrological and habitat changes. The studied oxbow was an aquatic ecosystem with diverse invertebrate fauna until the end of Younger Dryas when it transformed into a limno-telmatic habitat. The sediment composition indicates active denudation processes and several episodes of turbulent hydrological conditions. Such an increased river activity could have caused flooding, resulting in an allochthonous matter supply to the oxbow lake in Late Vistulian. Environmental changes were strictly related to the regional features of the catchment, the transformation of soils, and the hydrogeological conditions. The chironomid- and pollen-inferred climatic reconstructions indicate periods of high and low continentality. The chironomid record indicates relatively cool summer conditions in the Allerød, especially ca. 13,000 cal. BP, possibly related to the Gerzensee Oscillation. On the other hand, a distinct increase of summer temperatures in Younger Dryas (up to 16 °C) was recorded. Such a situation was also confirmed in some other studies from the region, suggesting that it might be the effect of some specific, local palaeoclimatic conditions. Fundator badań: Fundator badań: Optional.empty

Algal communities act as sensitive indicators of past and present climate effects on northern lakes, but their responses can vary considerably between ecosystems. Functional trait-based approaches may help us better understand the nature of the diverse biotic responses and their underlying ecosystem changes. We explored patterns in diatom (Bacillariophyceae) growth forms and species composition during the Neoglacial in two shallow lakes typical of subarctic regions, including a dark-colored woodland lake and a clear tundra lake. Sediment carbon and nitrogen elemental and isotope biogeochemistry and spectral indices were used to track broadscale changes in lake productivity, the inflow of organic carbon from land, and benthic substratum over the past three millennia. The biogeochemical indices tracked declines in land-lake connectivity as well as lake-water and sediment organic enrichment above and below the subarctic treeline driven by Neoglacial cooling. This broadscale environmental transition was intercepted by periods of elevated primary production associated with transient Neoglacial warm anomalies and, in particular, the twentieth century warming. Although the Neoglacial development of the lakes showed conspicuous similarities, diatom functional and taxonomic responses were not uniform between the lakes pointing to intrinsic differences in the development of benthic habitats and underwater-light regimes. Many of the observed biotic shifts aligned with expectations based on earlier research linking diatom functional traits to changing light and organic levels but the results also point to further research needs, particularly to better differentiate the individual and interactive effects of substratum and light. Despite distinct anthropogenic imprints in the biogeochemical record, the scale of human impact on the lakes’ biota has not, as yet, been profound, but the changes are nonetheless clear when compared to the previous three millennia of natural lake development.

The Warta River val ley was greatly in flu enced by the ice sheet of the Last Gla cial Max i mum (LGM). A small peatland lo cated in the Warta drain age sys tem is here used as a palaeoarchive of cli ma tic and hab i tat changes dur ing the Late Gla cial (Weichselian). The ugi pound sed i ment pro file was in ves ti gated us ing multi-proxy (pol len, Chironomidae, Cladocera and geo chem is try) anal y ses that re corded changes in a fluviogenic sed i men tary de pres sion. Af ter the Poznan Phase (LGM), ugi pound func tioned as an ox bow lake that was cut off from the ac tive river chan nel as a re sult of flu vial ero sion. Since that time, the Warta River has flowed only along the sec tion now oc cu pied by the Jeziorsko Res er voir. Sed i men ta tion of lac us trine de pos its started at the be gin ning of the Late Gla cial. Sum mer tem per a ture re con struc tions in di cate cool Old est and Youn ger Dryas, but no clear cool ing in the Older Dryas. Dur ing the Youn ger Dryas the palaeolake was com pletely oc cu pied by a peatland (fen), which pe ri od i cally dried out dur ing the Ho lo cene. In ves ti ga tion of this site has tracked the re ac tion of the hab i tat to cli ma tic, hy dro log i cal and geomorphological changes through out the Late Weichselian.

To investigate the Lateglacial and early Holocene climatic and environmental dynamics in the Eastern Baltic we analysed chironomid and pollen data from Lieporiai palaeolake, North Lithuania. The first quantitative mean July air temperature reconstruction from Lithuania based on fossil chironomid assemblages was performed using expanded Fennoscandian calibration model. Our study suggests that sedimentation started at about 14 600 cal yrs BP and lasted until the early Holocene. The mean July air temperature for Lateglacial and early Holocene from studied site ranged between 13 °C−16 °C which was ~ 2–4 °C lower than the present. Rapidly after the deglaciation during Bolling (GI-1e) interstadial reconstructed July air temperature reached ~ 15 °C. The marked temperature decrease to 13.2 °C was recorded during the Older Dryas (GS-1d). Temperature reached its highest values (up to 16 °C) during the Allerod (GI-1a). The Younger Dryas (GS-1) was relatively cold with the mean July air temperature ~ 14 °C and this was 3.9 °C colder than the present. The pattern of the Lateglacial temperature changes from Lieporiai Lake shows both similarities and some differences from the other chironomid based regional and European reconstructions. Chironomid inferred palaeoenvironmental changes are in positive correlation with changes in the development of vegetation.

The Younger Dryas (YD) is a roughly 1,100-year cold period marking the end of the last glaciation. Climate modelling for northern Europe indicates high summer temperatures and strong continentality. In eastern Europe, the scale of temperature variation and its influence on ecosystems is weakly recognised. Here, we present a multi-proxy reconstruction of YD conditions from Lake Gościąż (central Poland). The decadal-resolution analysis of its annually varved sediments indicates an initial decrease in Chironomidae-inferred mean July air temperature followed by steady warming. The pollen-inferred winter-to-summer temperature amplitude and annual precipitation is highest at the Allerød/YD transition and the early YD (ca. 12.7–12.4 ky cal BP) and YD/Holocene (11.7–11.4 ka cal BP) transition. Temperature and precipitation were the main reasons for lake level fluctuations as reflected in the planktonic/littoral Cladocera ratio. The lake’s diatom-inferred total phosphorus decreased with increasing summer temperature from about mid YD. Windy conditions in the early YD until ∼12.3 ka cal BP caused water mixing and a short-lived/temporary increase in nutrient availability for phytoplankton. The Chironomidae-inferred summer temperature and pollen inferred summer temperature, winter temperature and annual precipitation herein are one of only a few in eastern Europe conducted with such high resolution.