Response of the Siberian methane cycling microbial community to climate changes in Late Pleistocene and Holocene

• Main Authors: Griess, Juliane, Mangelsdorf, K., Wagner, Dirk
• Format: Conference Object
• Language: unknown
• Published: 2010
• Subjects: lena delta; permafrost; Polarforschung; Siberia
• Online Access: https://epic.awi.de/id/eprint/23179/; https://hdl.handle.net/10013/epic.35949

Permafrost environments are supposed to be strongly affected by the currently observed global temperature rise. About one third of global soil carbon is preserved in permafrost and an increase in temperature might increase the microbial turnover of recent as well as ancient carbon and cause the release of large amounts of greenhouse gases such as methane. To predict future methane emissions and to estimate the global atmospheric carbon budget, we need to understand the present composition of microorganisms being involved in cycling of methane and know their response to climate changes in the past. Therefore, a combination of quantitative and qualitative analyses of the variations in composition of bacterial and archaeal communities involved in the Siberian methane cycle was accomplished to reveal variations in permafrost deposits of the Holocene and Late Pleistocene. Such an approach was used on permafrost sediments for the first time.A 23 m long permafrost core drilled in 2002 on Kurungnakh Island, Lena Delta, Siberia, was examined using biogeochemical as well as microbiological methods. The interpretation of our data was done in context of a paleoclimate reconstruction based on pollen analysis at the same site (Schirrmeister et al., 2002). The sediments of Kurungnakh achieve different climatic stages: cold & dry, warm & wet, Holocene warming. As a general result it is shown that it was possible to recover lipid biomarkers and amplifiable DNA throughout the Kurungnakh permafrost sequence with an age of up to 42 ka. First analyses of glycerol dialkyl glycerol tetraethers (GDGTs) were conducted. GDGTs provide paleo-signals of archaeal and bacterial communities, since these lipids are already partly degraded but their core lipids are relatively stable outside intact cells. Highest amounts of ether lipids were found in the upper layer and at the bottom of the core. Total GDGT contents show highest concentrations with 495 ng/g sediment at 122 cm depth, with 70 ng/g sediment at 1184 to 1745 cm and with about ...