History of the Development of Eemian Interglacial Lakes on the Basis of Cladocera Subfossil Analysis (Central and Eastern Poland)

This paper presents the results of Cladocera subfossil analysis using material obtained from five paleolakes of the Eemian Interglacial located in central and north-eastern Poland. Analyses of Cladocera subfossils in Poland and other parts of the world have revealed detailed results covering the last 13,000 years. Cladocera subfossils from sediments older than the last glaciation have been analysed occasionally. The first analyses of older sediments were conducted in Denmark by Frey in 1962. In Poland, the first analyses of this type were conducted on material obtained in Konin. The Eemian lakes subject to the study were formed at the end of the Warta Glaciation in tunnel and kettle holes. A continuous record of environmental changes throughout the Eemian Interglacial until the early Vistulian Glaciation has been preserved in lake sediments. The bottom part of the profile consists of sands and silts, followed by gyttja and peat. The upper part of the profile contains peat and organic shales. Cladocera subfossils found in Eemian sediments were thinner and their structure was more damaged. The low degree of subfossil preservation forced a change in the method of preparation of subfossils for microscopic analysis as required by IGCP Project 158. Cladocera species determined within the studied paleolakes correspond to the present-day species inhabiting the area of Poland and Europe. The species composition and the variability in the frequency of Cladocera specimens made it possible to distinguish discrete phases of lake development associated with changes in temperature and water level, trophic state and the presence of macrophytes. The results of Cladocera analysis are well correlated with data obtained in pollen analyses.