Diatom-based reconstruction of Lake Turgoyak (Southern Urals) ecosystem changes in the Holocene

Abstract

Lake Turgoyak development through more than 12 thousand years was studied based on diatom analysis of the lake sediment core. Altogether 142 diatom taxa were identified. Four diatom zones corresponding to main stages of the lake ecosystem development were distinguished with application of stratigraphically constrained cluster analysis. It was found that in the period from 12.1 to 11.0 cal ka BP Lake Turgoyak had maximum salinity and a high degree of overgrowth with hydrophytes. Desalination and an increase in the lake depth occurred between 11.0 and 7.7 cal ka BP. Substantial fluctuations of the lake parameters about 8.0-7.0 cal ka BP were followed by period of lower flow rate and accumulation of sediments with a high content of organic matter. Approximately 2.7 ka cal BP the lake depth increased and salinity decreased. It was concluded that the chronological boundaries of the main stages of the lake ecosystem development coincide with the climatic events previously determined for the Holocene and Late Glacial of the Urals.