Abstract
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 × 10 6 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 d 18 O 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 d 18 O 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 d 18 O stage 2 (12–24 kyr B.P.). Zone CA‐III (21.3–73.2 kyr B.P.) comprised d 18 O 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 d 18 O 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 d 18 O 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.