Diatom analysis of the bottom sediments from the tundra lake of the Yerkuta River basin (Yamal Peninsula, Russia)

Abstract

This paper presents the results of a diatom analysis of a column of bottom sediments of an unnamed lake under the conditional name 21-Ya-02 (6809'90.3" N; 06857'61.0" E, Yamal Peninsula). The age of the selected column with a length of 67 cm was 6200 cal. years. 118 taxa of diatoms belonging to 38 genera were identified in the bottom sediments. The highest taxonomic richness is noted for the genus Eunotia (21 taxa). According to the number of diatom valves, the acidophilic taxon Tabellaria flocculosa (Roth) Kutzing dominated in the bottom sediments of the studied column of the lake. Diatom analysis of the bottom sediments of the studied lake allowed us to identify the main stages of the evolution of the reservoir in the Middle and Late Holocene. Acidophilic taxa Eunotia triodon, Tabellaria flocculosa dominated in Lake 21-Ya-02 in the period ~6200-–5100 cal. years BP, preferring shallow areas of reservoirs with low mineralization. Further, in the time interval ~5100–3600 cal. years BP, a transition to the dominance of planktonic alkaliphilic taxa was noted, presumably reflecting a decrease in acidification in the reservoir. 3600–700 cal. years BP absolute dominance of planktonic diatoms was observed in the bottom sediments, acidophilic taxa practically disappeared, which may indicate a change of slightly acidic conditions of the aquatic environment to slightly alkaline ones as a result of a change in environmental and climatic conditions. However, about 700 years ago, the importance of acidophilic and cold-water taxa increased again, which may reflect an increase in the areas of shallow waters and wetlands on the territory of the reservoir with worsening climatic conditions.