Warunki ekologiczne rozwoju późnovistuliańskiego zbiornika Koźmin Las w świetle analizy Cladocera

The sediments from small pond infillings located in the Warta River valley in central Poland was studied by Cladocera analysis in order to examine the response of aquatic ecosystems to environmental changes in the Younger Dryas. Lithological and geochemical records were also used to reconstruct fluvial activity of the Warta River. In the Koźmin Las site development, between ca. 12.900 and 11.600 cal BP, prevailed variable hydrological conditions. Cladocera analysis indicates the presence of shallow pool and partly telmatic conditions. The local processes, such as the influence of the Warta River, habitat modification, macrophyte presence, and eutrophication, were important, but these forces were not only major factors that affect the biota diversity in the Younger Dryas. The observation of changes in the composition and concentration of aquatic communities in the studied pool indicates that the changes also occurred in response to climate changes.