A 200,000-year, high-resolution record of diatom productivity and community makeup from Lake Baikal shows high correspondence to the marine oxygen-isotope record of climate change

Siliceous microfossil succession was analyzed in a 200,000-yr sediment sequence recovered from the Buguldeika Saddle in Lake Baikal, Russia. Siliceous microfossil abundance varied among core depths from no preserved microfossils during inferred colder climate conditions to recent interglacial sediments containing over 300 3 106 microfossils per g dry sediment. Depth-age microfossil assemblage zones (CA-I to CA-IV) identified using correspondence analysis had high correspondence to stages in the marine d18O isotope record and could be partially aligned with Late Pleistocene glacial–interglacial cycling models from the mid-Siberian Highland. These observations suggest that Lake Baikal phytoplankton communities have responded to climatic changes driven by insolation parameters and global ice volumes on temporal scales similar to tropical and polar oceans. Microfossil zone CA-I (0–11.4 kyr B.P.) corresponded to the Holocene interglacial or d18O stage 1 (0–11.4 kyr B.P.), a period of higher production in Lake Baikal during a climatic optimum. Microfossil zone CA-II (12.3–18.7 kyr B.P.) corresponded to the Sartan glaciation and d18O stage 2 (12–24 kyr B.P.). Zone CA-III (21.3–73.2 kyr B.P.) comprised d18O stages 3 and 4. However, within zone CA-III, subzones CA-IIIa and IIIb (21.3–56.8 kyr B.P.) grouped were well aligned with d18O stage 3 and contained sediments deposited during the inferred Karginskiy interstade. Microfossil zone CA-IVa (77.4–129.2 kyr B.P.) and CA-IVb (130.3–172.5 kyr B.P.) included d18O stages 5 and 6, respectively, with sediments that were most likely deposited during the Taz glaciation and the Kazantsevo interstade. Climate-induced changes are reflected in production differences and in community composition specificity within microfossil zones or climate stages. This suggests that climate change drives major historical successional patterns in Lake Baikal’s primary producer community; changes in primary producers must have further impacted the system’s entire biota. Lake Baikal, the world’s largest single body of fresh water by volume, is located in Central Asia (518439N, 1038449E to 558469N, 1098379E) along the Baikal Rift Zone between the Siberian Craton of the Eurasian continental plate and the Amur plate (Hutchinson et al. 1993; Moore et al. 1997). The lake is composed of three major basins separated by local highs in the lakebed. The Buguldeika Saddle-Selenga Delta separates the south from the central basin, and the Academician Ridge separates Baikal’s deepest basin, the central, from the shallowest basin, the north (Fig. 1). Baikal is thought to have persisted as a lake for at least 25 million years, from the Miocene to present (Mats 1993). The large size, ancient age, and natural/economic resource potential of Lake Baikal have contributed to the uniqueness of its modern limnological conditions (Shimaraev et al. 1994), biota (Kozhov 1963), and environmental concerns (Galaziy 1980). The lake is situated in the mid-Siberian Highland, a wide geographical province within central Siberia (Arkhipov et al. 1986b). This region has been subjected to the impacts of glacial–interglacial cycling during the Pleistocene, as evidenced in pollen records and geomorphological features. 1 Corresponding author ([email protected]).