Abstract
Siliceous stomatocysts of chrysophyte algae, along with diatom frustules, are well preserved in bottom sediments of various water bodies. Analysis of microfossils from a core sample of the Upper Pleistocene and Holocene sediments from the southern part of Lake Hovsgol revealed 36 different morphotypes of chrysophycean stomatocysts. Some of them were attributed to species of the genera Mallomonas Perty, Chrysosphaerella Lauterborn., Paraphysomonas (Stokes) De Saedeleer, and Dinobryon Ehr.; 20 morphotypes were described as novel. The abundance and diversity of stomatocyst morphotypes in the core sample varied depending on the age of sediments. The results obtained in the study broaden views on the biological diversity of microalgae and confirm that chrysophycean stomatocysts can serve as good environmental indicators in paleolimnological and paleoclimatic reconstructions.
Highlights
Bottom sediments of Lake Hovsgol, which are approximately 550 m deep [1], reflect the history of climate change as well as the history of the lake itself
A palynological analysis of the Upper Pleistocene and Holocene sediments from the deep-water part of Lake Hovsgol has resulted in identification of six palynozones indicative of the following climatic sequence: a sharply continental climate with a deficiency of atmospheric moisture supply about 14 ka BP; a milder climate with higher winter and summer temperatures and increasing atmospheric moisture between 9.5 and 6.5 ka BP; a cool and moist climate during the Holocene optimum, which ended about 6 ka BP; the prevalence of dry and warm climate between 5.5 and 3.5 ka BP; and the development of climatic conditions close to those prevailing today beginning from 3.5 - 3.0 ka BP [5]
The purpose of this research was to study the morphology of chrysophycean stomatocysts by means of scanning electron microscopy (SEM) and to analyze the pattern of their distribution in a core sample of sediments from the southern part of Lake Hovsgol, which was stratigraphically correlated with previously studied sediment cores on the basis of diatom analysis
Summary
Bottom sediments of Lake Hovsgol, which are approximately 550 m deep [1], reflect the history of climate change as well as the history of the lake itself. Palynological and diatom analyses of core samples from the central and northern parts of the lake have revealed specific features of the climate of Mongolia during the Holocene and have shown that fluctuations in the concentration of microfossils depend on climatic changes and on variation in the level and, probably, salinity of water in the lake [2,4,8]. As follows from the results of palynological and diatom analyses [8], such events repeatedly took place during the Holocene (in particular, 6500 - 5400, 4900 - 4000, and 2600 - 1800 years BP)
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