Microbial communities and their response to Pleistocene and Holocene climate variabilities in the Russian Arctic

• Main Author: Bischoff, Juliane
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2013
• Subjects: ddc:500; Institut für Geowissenschaften; Arctic; Arktis; Arktis*; Chukotka; Climate change; Global warming; permafrost; Siberia
• Online Access: https://publishup.uni-potsdam.de/frontdoor/index/index/docId/6657; https://nbn-resolving.org/urn:nbn:de:kobv:517-opus-68895; https://publishup.uni-potsdam.de/files/6657/bischoff_diss.pdf

The Arctic is considered as a focal region in the ongoing climate change debate. The currently observed and predicted climate warming is particularly pronounced in the high northern latitudes. Rising temperatures in the Arctic cause progressive deepening and duration of permafrost thawing during the arctic summer, creating an ‘active layer’ with high bioavailability of nutrients and labile carbon for microbial consumption. The microbial mineralization of permafrost carbon creates large amounts of greenhouse gases, including carbon dioxide and methane, which can be released to the atmosphere, creating a positive feedback to global warming. However, to date, the microbial communities that drive the overall carbon cycle and specifically methane production in the Arctic are poorly constrained. To assess how these microbial communities will respond to the predicted climate changes, such as an increase in atmospheric and soil temperatures causing increased bioavailability of organic carbon, it is necessary to investigate the current status of this environment, but also how these microbial communities reacted to climate changes in the past. This PhD thesis investigated three records from two different study sites in the Russian Arctic, including permafrost, lake shore and lake deposits from Siberia and Chukotka. A combined stratigraphic approach of microbial and molecular organic geochemical techniques were used to identify and quantify characteristic microbial gene and lipid biomarkers. Based on this data it was possible to characterize and identify the climate response of microbial communities involved in past carbon cycling during the Middle Pleistocene and the Late Pleistocene to Holocene. It is shown that previous warmer periods were associated with an expansion of bacterial and archaeal communities throughout the Russian Arctic, similar to present day conditions. Different from this situation, past glacial and stadial periods experienced a substantial decrease in the abundance of Bacteria and Archaea. This trend ...