Phytoplankton response to climate changes in Lake Baikal during the Holocene and Kazantsevo Interglacials assessed from sedimentary pigments |
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| Authors: | Susanne Fietz Andreas Nicklisch Hedi Oberhänsli |
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| Institution: | (1) Leibniz Institute of Freshwater Ecology and Inland Fisheries, Mueggelseedamm 301, 12587 Berlin, Germany;(2) Institute of Biology, Humboldt-University Berlin, Luisenstrasse 53, 10099 Berlin, Germany;(3) GeoForschungsZentrum Potsdam, Telegraphenberg, 14473 Potsdam, Germany |
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| Abstract: | Lake Baikal, an ancient pristine lake in Siberia, has accumulated sediment deposits that span 25 million years. These deposits
have the potential to provide a long-term record of climate changes and their interaction with the ecology of the lake. In
order to investigate whether sedimentary phytoplankton pigments could be used to reconstruct past changes in total phytoplankton
abundance and productivity, we compared the spatial variability in sedimentary pigment distributions in Holocene cores from
three separate regions of the lake; Vidrino in the south, Posolski on Selenga Delta and Continent Ridge in the north. Furthermore,
we present the first continuous sedimentary pigment and organic carbon sequence of the Kazantsevo interglacial (roughly a
time equivalent to the European Eemian, and Marine Isotopic Stage MIS5e) at a resolution of approximately 150 years. Results
of the spatial study showed marked differences in the sediment pigment deposition. Lowest chlorophyll a plus its degradation products versus organic carbon ratios (Chlas/TOC) indicating lowest production, but highest variability with time (indicating strongest climatic oscillations) were found
at Continent Ridge. The study of sedimentary pigments deposited during the last two interglacial periods at Continent Ridge
showed Chlas/TOC ratios 50–1000 times higher during the Kazantsevo Interglacial compared to the glacial periods, whereas the TOC content
was only five times higher, thus indicating the significance of the Chlas/TOC ratio for the reconstruction of the phytoplankton abundance and productivity. Strong oscillations occurred during the
Kazantsevo Interglacial within centennial time scales. Chlorophyllb plus its degradation products provided additional information on the past development of Chlorophyceae. Highest Chlas/TOC ratios were found during the early Holocene at approximately 9 kyr BP. Indications of short phytoplankton production
maxima were also found during the late Atlantic (6 kyr BP) and at the Subboreal/Subatlantic transition (3 kyr BP). From this
we conclude that sedimentary chlorophyll a is a reliable indicator of phytoplanktonic response to climate changes and may serve for␣validation of future climate scenarios
in continental regions. |
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| Keywords: | Chlorophyll Chlorophyceae Degradation Diatoms MIS5e Palaeoproductivity |
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