Title: Diatoms in the Bottom Sediments of Two Closely Located Lakes in Khakassia
Abstract: Diatoms are one of the main paleo-indicators of lake changes, as they are preserved in bottom sediments for centuries.The present study reports new data on diatoms in the bottom sediments of Lake Shira and compares them with diatoms from the bottom sediments of Lake Utichye-3, which is situated close to Lake Shira (Khakassia, Russia).The results showed that both lakes have undergone changes in the past, and the species compositions have changed several times.The dominant species in Lake Shira is now Cyclotella choctawhatcheeana Prasad, a planktonic marine species.Rhopalodia constricta (W.Smith) Krammer is a benthic brackish or freshwater species that often occurs in Lake Shira.The lower layers of sediments, dating from approximately the 17 th century, were dominated by the freshwater plankton species Aulacoseira ambigua (Grunow) Simonsen and A. italica (Ehrenberg) Simonsen; Staurosira venter sensu lato (Ehrenberg) Cleve & JD Möller, a benthic freshwater species, also occurred there.The bottom sediments of Lake Utichye-3, with the exception of the lower layers, were dominated by C. meneghiniana Kützing (a planktonic brackish or freshwater species).This species was also found in the upper layers of the bottom sediments of Lake Shira.This suggests that conditions in Lake Shira and Lake Utichye-3 were once similar.Surirella peisonis Pantocsek (a marine species) prevailed in the lower layers of the core of Lake Utichye-3.Thus, we can say that the climatic conditions in the region where the lakes are situated have changed several times.