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EN
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 least 13C-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.
EN
The present study investigates environmental conditions during sediment accumulation in Lake Niepruszewskie, western Poland. Palaeolimnological reconstructions are based on stable isotope composition ([delta^13]C and [delta^18]O) of a wide range of biogenic carbonates occurring in the sediments, including shells of several gastropod species and the bivalve genus Pisidium, carapaces of ostracods belonging to the subfamily Candoninae and encrustations and oogonia of the aquatic macrophyte genus Chara. According to the radiocarbon dates obtained, accumulation of the sediment sequence began in the early Atlantic and terminated in the early Subboreal. Both [delta^13]C and [delta^18]O records reveal significant and frequent fluctuations that are attributed to repeated changes in the Lake Niepruszewskie water balance. However, conditions of prevailing long water residence time, accompanied by high productivity within the lake, are reflected in a [^13]C-enriched carbon-isotope record. Minimum [delta^13]C and [delta^18]O values were recorded for the earliest Atlantic and maximum values characterize the interglacial optimum during the middle and late Atlantic. Discrepancies observed between isotope records of particular taxa reflect the specific season and subhabitat of each carbonate secretion. [^13]C-enriched Chara encrustations and oogonia are consistent with their precipitation within the photic zone, which is commonly [^13]C-enriched due to the photosynthetic activity of macrophytes and phytoplankton. The carbon isotope composition of Lymnaea auricularia shells indicates that breathing behaviour leaves its imprint on [delta^13]C in snail shells. In aquatic air-breathing pulmonate gastropods this results in [^13]C-depletion in shells. Isotope records of individual shells of two snail species, Valvata piscinalis and Gyraulus laevis, indicate that in order to obtain mean [delta^13]C and [delta^18]O values that are representative of a 5 cm thick sampling interval, stable isotope signatures of more than five shells must be obtained.
EN
Stable isotope composition ([delta^18]O and [delta^13]C) of biogenic carbonates derived from the Lake Lednica sediments at Rybitwy, western Poland, was applied to obtain data on climatic changes during the Late Glacial and early Holocene. A wide range of carbonates occurring in the sediments was analysed for [delta^18]O and [delta^13]C records, including shells of several gastropod species, the bivalve genus Pisidium and carapaces of ostracods belonging to the subfamily Candoninae. The [delta^18]O and [delta^13]C records reveal changes commonly observed for the Late Glacial and early Holocene with the exception of the low oxygen isotope values of the Bolling and Allerod Interstadials. The latter is interpreted as a consequence of [^18]O-depletion of the lake water resulting from gradual melting of the dead ice that still filled the deepest parts of the Lake Lednica valley during the period described. The Younger Dryas Stadial begins with the isotopically lightest values in the sequence; however, due to the [^18]O-depleted values of the Allerod Interstadial the Allerod/Younger Dryas boundary is poorly marked. The Younger Dryas/Preboreal transition is documented by a significant shift in [delta^18]O values of about 2-3[per mil], resulting from an increase in the mean annual temperature. The [delta^13]C record reflects the productivity level in the lake, with [^13]C-enriched carbonates during the Bolling and Allerod Interstadials, and the Preboreal and Boreal, when photosynthetic activity of phytoplankton and macrophytes was the most intensive. Differences in [delta^18]O and [delta^13]C values between mollusc shells and ostracod carapaces reflect the specific season and subhabitat of each carbonate secretion.
EN
Late Glacial and Holocene lacustrine molluscs occurring in three sites from the Gniezno and Poznan Lake Districts in central Poland are described. The mollusc fauna present in the sites is composed mainly of aquatic species with an accessory content of terrestrial snails inhabiting damp or very damp, periodically flooded sites. Ecological preferences of species, changes in their composition and frequency together with shell dimensions are used as indicators of palaeoenvironment and palaeoclimate. Infrequent shells present in the Imiolki and Rybitwy sites are small and thin-walled in consequence of the cold climate prevailing in the Late Glacial when the sediments in question were deposited. In the Imiolki site Pisidium lilljeborgii CLESSIN, a species indicative of low temperatures, occurs. Deposits in the Niepruszewo-Ciesle site were accumulated through most of the Holocene, thus warmer conditions resulted in considerably more abundant and larger shells with thicker walls.
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