Dr Sabine Lengger

Research interests

Past, present and future of methane emissions from wetlands: Identifying pathways of methanogenesis via the carbon stable isotopic composition of biomarkers. Methane, a potent greenhouse gas, plays a crucial role in the global climate system. The majority of methane emissions is produced by methanogenic archaea in wetlands. These organisms generate methane mainly via two pathways: fermentation of acetate, a product of organic matter degradation, and CO2 reduction with hydrogen. Relative amounts of methane produced by each pathway differ amongst settings, and which pathway is dominant depends on various environmental conditions. To assess the global methane budget both today and in the past, it is crucial to be able to distinguish between these pathways. However, methane formation in ancient settings cannot yet be determined. A promising approach could be the carbon isotopic composition of methanogen derived lipids since the two pathways appear to result in lipids with different values. As this is based on limited data, I propose to develop a novel method for the rapid determination of the stable carbon isotope composition of tetraether lipids. I will study the suitability of tetraether lipids as biomarkers for methanogens and their isotopic compositions as potential proxy for methanogenic pathways, and apply this proxy to past environments, thereby increasing our understanding of the methane cycle in the past, present and future.

Other research

My research topics have developed out of a strong interest in analytical techniques for detection of biomarkers / polar molecules and microbial ecology / biogeochemistry. I worked on Archaea (production and biodegradation of lipids) in sediments, on products of microbial biodegradation of oil, on polar compounds (sterols) in sponges and fossil concretions. Now, I am working on a way to enable the determination of the stable isotopic composition of large, polar biomarkers for the methane cycle. For my research, I use highly developed analytical methods such as HPLC-ESI-MSn, GC-IRMS, GCxGC-TOFMS and GC-IRMS. I am also very interested in the use of advanced data processing and statistical methods for geochemistry, in order to investigate patterns of naturally produced and anthropogenic compounds in the environment, and to compare recent organisms or samples with fossil biomarker distributions.

Grants & contracts

2014 Rubicon Fellowship (NWO, Netherlands Organization for scientific research), for conducting research on the methane cycle at the University of Bristol with Prof. R. Pancost (151 000 €) 2007 Double Degree program (Cranfield University / Graz University of Technology), for courses in Environmental Diagnostics and Master’s dissertation at Cranfield University, UK (ca. 4 000 €) 2006 Vulcanus in Japan Fellowship, EU/Japan Center for industrial Cooperation, for studies of Japanese language/business culture and internship (15 000 €) 2006 Faculty of science grant, University of Graz, for attendance of a course in Arctic Microbiology, University of Trømsø – The University Center in Svalbard, Norway (ca.1 000 €) 2004 Erasmus scholarship, Graz University of Technology, for studies at the University of Oviedo, Spain (ca. 4 000 €)

Research groups

• Biogeochemistry Research Centre (BGC)
• Petroleum and Environmental Geochemistry