ALBERT

Description: will be submitted by the author

Description: Aim: To understand modern and past aquatic community responses to climate-induced shifts in productivity and ultraviolet radiation (UV) exposure. Location: Treeline ecotone from north boreal forest to subarctic tundra in northeastern Finnish Lapland. Taxon: Cladocera (Crustacea: Branchiopoda). Methods: 31 small and shallow lakes were examined for summer epilimnetic communities (SEC) and surface sediment fossil integrative communities (FIC) of Cladocera for species distribution and their environmental correlations. A 700-year down-core sediment sequence from a treeline lake (Námmájávri) was analyzed for FICs and cladoceran-inferred UV-absorbance (ABSUV, indicative of melanin pigmentation) for evidence of long-term community and photoprotective responses and compared with records of paleotemperature, solar intensity, and composite sediment biogeochemistry by variance partitioning analysis. Results: The SECs were primarily correlated with specific UV absorbance (indicative of UV exposure) and total phosphorus and FICs by mean July air temperature and total nitrogen. The Námmájávri FICs showed subtle changes with a directional shift between the 19th and 21st centuries and were mostly explained by solar intensity. ABSUV exhibited increases during the 18th and 20th centuries, being related to variation in sediment biogeochemistry, which was indicative of changes in auto- vs. allochthonous production. Main conclusions: The ecotonal distribution of cladocerans is sensitive to temperature, nutrients, and allochthonous carbon, which is closely linked with UV exposure. The long-term community shifts and photoprotection have been governed by solar intensity and biogeochemical shifts through lake water optics, attributable to direct UV impact or climate-mediated intensification in photodegradation of allochthonous carbon. Estimations of the dual effects and mechanisms of increasing temperatures and UV on subarctic lakes and their biota remain challenging as their individual impacts on key species were partly contradictory.

Description: These datasets provide data for the lowest part of a new composite profile GOS18 from Lake Gościąż in central Poland. The composite profile was established using sediment cores recovered in 2015 and 2018 with an UWITEC Piston Corer at 19.6-21.5 m water depth (Bonk et al., in press). Our data covers the time interval from the onset of lacustrine sedimentation in the late Allerød to the early Preboreal. Since Lake Gościąż comprises a continuous, seasonally resolved (varved) and exceptionally well-preserved archive of the Younger Dryas (YD) climate variation, it is highly suitable for detailed investigations of lake system responses during periods of rapid climate cooling (YD onset) and warming (YD termination), respectively. Chironomidae head capsules (hc) were utilized to reconstruct the mean July air temperature from the late Allerød to the early Preboreal in Lake Gościąż (central Poland). Sample resolution ranges from 0.5 to 6 cm. Two different training sets were used for the reconstruction - the Swiss-Norwegian-Polish Training Set (SNP TS) (Kotrys et al. 2020) and the East European TS (EE TS) (Luoto et al. 2019). Both use the Weighted Averaging-Partial Least Squares transfer function (WA-PLS).The dataset incorporates the composite depth and age [BP] for the sample midpoint, as well as for both training sets, respectively, the chironomid-inferred mean July air temperature, the standard error and the squared chi-square distance between the fossil sample and its closest modern analogue in the respective training set.

Description: These datasets provide data for the lowest part of a new composite profile GOS18 from Lake Gościąż in central Poland. The composite profile was established using sediment cores recovered in 2015 and 2018 with an UWITEC Piston Corer at 19.6-21.5 m water depth (Bonk et al., in press). Our data covers the time interval from the onset of lacustrine sedimentation in the late Allerød to the early Preboreal. Since Lake Gościąż comprises a continuous, seasonally resolved (varved) and exceptionally well-preserved archive of the Younger Dryas (YD) climate variation, it is highly suitable for detailed investigations of lake system responses during periods of rapid climate cooling (YD onset) and warming (YD termination), respectively. Stable isotopes of oxygen in carbonates (δ18Ocarb) and of carbon in bulk organic matter (δ13Corg) were determined on bulk sediment samples contiguously taken at 0.5-1 cm resolution for the time interval from late Allerød to early Preboreal in Lake Gościąż (central Poland). All samples were freeze-dried, manually ground and homogenized, while samples for δ13Corg were additionally de-carbonized in situ. The dataset incorporates the composite depth and age [BP] for the sample midpoint, as well as the respective δ18Ocarb and δ13Corg values.

Description: These datasets provide data for the lowest part of a new composite profile GOS18 from Lake Gościąż in central Poland. The composite profile was established using sediment cores recovered in 2015 and 2018 with an UWITEC Piston Corer at 19.6-21.5 m water depth (Bonk et al., in press). Our data covers the time interval from the onset of lacustrine sedimentation in the late Allerød to the early Preboreal. Since Lake Gościąż comprises a continuous, seasonally resolved (varved) and exceptionally well-preserved archive of the Younger Dryas (YD) climate variation, it is highly suitable for detailed investigations of lake system responses during periods of rapid climate cooling (YD onset) and warming (YD termination), respectively. Our varve chronology is the lowest part of a new floating varve chronology established for Lake Gościąż (central Poland) that has been anchored to the absolute time scale through radiocarbon dating and age modelling (Bonk et al., in press). The here presented varve chronology reaches from the onset of lacustrine sedimentation in the late Allerød until the early Preboreal. Uncertainties for the absolute ages are derived from radiocarbon age modelling and varve counting. The internal varve counting uncertainty for the observed time interval is generally low (+14/-22) due to the mostly excellent varve preservation. Microfacies analyses, including varve counting and measurements of varve and sublayer thickness, have been performed on overlapping large-scale thin sections under an Axioplan 2 and Axiolab pol imaging microscope at magnifications of 50-400x. Thin sections have been prepared from 10 cm long freeze-dried and resin impregnated sediment slices (Brauer & Casanova 2001; doi:10.1023/A:1008136029735). The dataset incorporates the composite depth, age [BP] and age uncertainties [BP] for the varve bottom, the total varve thickness, selected sublayer thicknesses, detrital sublayer occurrence, the different varve types and the varve quality index (VQI).