Changes in chironomid communities during the Holocene in Lake Polevskoye (Zaonezhsky Peninsula, northwestern Russia)

Abstract

We reconstructed paleoclimatic and paleoenvironmental changes based on the analyses of sediments from the Lake Polevskoye on the Zaonezhsky Peninsula in northwestern Russia. The change in the taxonomic composition of chironomids was analysed in the studied core. The age of the sediments covers ca 7.1 thousand years. Based on the cluster analysis, 3 main stratigraphic zones were identified. From 7.1 to 5.2 ka cal. yrs. BP, phytophilic taxa associated with shallow lakes dominated. Later between 5.2 – 2.0 ka cal. yrs. BP chironomids biodiversity increased. During this period, cold-water taxa appeared, which might indicate some cooling during this period. There was also a simultaneous increased in the number of profundal and semi-terrestrial species, which may indicate the changes of the water level in the lake and paludification. After 2.0 ka cal. yrs. BP the total number of species decreased. The dominant taxa associated with shallow water levels and moderately warm climatic conditions. Changes in the taxonomic composition of chironomids in Lake Polevskoye responded to paleoenvironmental changes. During the studied period, there was an increase in diversity of chironomids and a change in dominant taxa. The reconstructed conditions showed an increase in the water level in the lake from 5.2 to 2.0 ka cal. yrs. BP, as well as a gradual increase in trophicity.