Investigating water level changes in Lake Balaton over the past 500 years

Abstract

Climate change and anthropogenic disturbance on our water bodies cause rapid changes in aquatic ecosystems. The study of subfossil aquatic organisms can be used to track the history of various environmental changes, hydrological events, climate and human impacts. The aim of this study is to reconstruct historical water levels, water quality and predation changes in Lake Balaton, Hungary using subfossil cladoceran remains.

A 65-cm long sediment core was taken and analysed for cladocerans at 2 cm resolution using 1 cm³ subsamples. Cladocera remains preserved well in the sediment and can be identified at the species level. Relative frequency distribution and concentration of the cladocera assemblages were recorded for each depth and plotted along age and depth using the 210Pb and 137Cs based age-depth model for the last 200 years (0-30 cm) and linear extrapolation for the deeper layers (30-65 cm). So far, we found minor variation in species number, but major variation in total cladocera concentrations. Changes in subfossil Cladocera communities did not always show changes in water levels. Our results suggest that water level fluctuations in the Szemesi-basin of Lake Balaton cannot be determined with high confidence from changes in Cladocera communities alone, so we need to include other proxies in this type of studies.