Diatom assemblages in the Lateglacial-Holocene sediments of Lake Bolshoye Shchuchye (Polar Urals)

The study of the diatom assemblages from the sediment core from Lake Bolshoye Shchuchye (Polar Urals) was performed. The composition of diatom assemblages in the Lateglacial sediments characterizes alternating periods of predominance of planktonic and benthic diatoms. In the Holocene, planktonic species predominate with Aulacoseira subarctica being the most abundant. The climate amelioration during the first half of the Holocene resulted in increased proportions of large-celled diatoms, the taxa with a wide geographical distribution, as well as species preferring higher trophicity. The cooling of the Late Holocene, in turn, caused an increase in the proportion of cold-water species characteristic of oligotrophic lakes. The morphological variability of A. subarctica observed in the Holocene sediments apparently results from its adaptation to changes in hydrodynamic conditions.