Records of the 8200 cal BP cold event reflected in the composition of subfossil Cladocera in the sediments of three lakes in Poland

The 8200 cal BP cold event was documented by analyzing cladoceran subfossil remains in sediments of three Polish lakes. To date, this cold event has primarily been identified in areas located at higher latitudes of the Northern Hemisphere. It has mainly been confirmed by results of oxygen and carbon stable isotope analyses. This survey represents an attempt to find traces of the 8200 cal BP cold event in lake sediments, based on changes in the species composition and frequency of cladoceran individuals. Both archival, accurately dated sediments (Lake Ostrowite, Lake Gosciaz), and recently cored samples (Lake Charzykowskie) were used. The analysis of subfossil cladocerans was performed at a high resolution. This allowed derivation of detailed conclusions regarding Early Holocene changes within lakes, and therefore conclusions on short-term climate changes. In Lakes Ostrowite, Charzykowskie, and Gosciaz, changes in the zooplankton Cladocera composition occurred at the same time as the cold event. Certain species disappeared completely, and the percentage share of the majority of zooplankters decreased significantly. Certain species (Camptocercus lilljeborgi, Alonopsis elongata), that are typical of lakes in Northern areas, appeared during the cold event, although not in large numbers. (C) 2010 Elsevier Ltd and INQUA. All rights reserved.