Cladocera remains in short cores from two small northern lakes (Bolshezemelskaya Tundra, Russia)

Abstract

© 2018, International Multidisciplinary Scientific Geoconference. All rights reserved. Territories of Bolshezemelskaya tundra are characterized by permafrost and large number of lakes in the region. Harbey lakes are the largest lakes system in the SouthEast of Bolshezemelskaya tundra. The system is a chain of series-connected water bodies (Golovka, Bolshoy Harbey and Maliy Harbey), which are connected by ducts with shallow lakes (Kilometrovoye, Kotovo, Leningradskoye). Short columns of bottom deposits of Kotovo and Kilometrovoye lakes with the lengths of 27 and 16 cm, respectively, were analyzed for the qualitative content of Cladocera. In the subfossil composition of lakes 20 taxa of Cladocera were registered: 17 taxa in Kotovo lake and 15 taxa in Kilometrovoye lake belonging to 4 families (Chydoridae, Eurycercidae, Daphniidae, Bosminidae) and 10 genera. Subdominants of Kotovo lake are represented by Chydorus cf. sphaericus, Alona affinis and Bosmina (Eubosmina) sp. Chydorus cf. sphaericus is the dominant in Kilometrovoye lake throughout the entire period of the study, while in Kotovo lake this taxon becomes the dominant only at the depth of 9 cm by replacing Alona affinis. The increase of the planktonic species proportion in the upper 0-3 cm of the sediments with decreasing of the relative abundance of the littoral zone inhabitants is noted. The proportion of littoral species in the composition of Cladocera remains of the Kotovo and Kilometrovoye lakes is quite high, due to small size and depths of the water object. Increase of the proportion of Chydorus cf. sphaericus at the present stage of the lake evolution indicates the beginning of the water pollution and eutrophication. The increase of the planktonic species proportion can be the consequence of the permafrost melting.