A new record of Holocene climate change from the bottom sediments of Lake Baikal

Detailed siliceous microfossil records (diatoms and chrysophyte cysts) from the BDP-93-2 borehole with resolution of ca 30-120 years were obtained from Lake Baikal sediments to test the sensitivity of the Lake Baikal system to minor climate changes during the Holocene. Our new results demonstrate that the Subboreal period is characterized by the highest accumulations of diatom frustules and chrysophyte cysts in Lake Baikal sediments. The siliceous microfossil record suggests that the Holocene climatic optimum in this interior part of Asia corresponds to the Subboreal period 2.5-4.5 ka and not to the Atlantic period 4.6-6 ka. Although quite different from Holocene reconstructions for the European part of Eurasia, the Holocene sedimentary record from Lake Baikal shows good correlation with palynological and soil climatic records from southeast Siberia and Mongolia where similar responses of the terrestrial biosphere are also documented, A distinctive monospecific lamina of Synedra acus diatom species, coincident with the maximum of chrysophyte cyst accumulation during the Subboreal period, argues for the possible short-term changes of the trophic state of Lake Baikal from oligotrophic, with a cold-water diatom assemblage, to eutrophic with a thermophilic monospecific diatom flora. Comparison of diatom and cyst responses provides a key to distinguishing the humidity from temperature response in future studies of high-resolution records of Lake Baikal. (C) 2000 Elsevier Science B.V. All rights reserved.