Schwark, Lorenz
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Item-typ:Veröffentlichung, Gaseous hydrocarbon cycling and lipid biogeochemistry in cold and hot seep sediments(2020-07-22); ; ; The release of hydrocarbon gases at the seafloor is a rich energy source for chemosynthetic ecosystems, but can also impact the climate when entering the atmosphere. The overall objective of this thesis was to explore the formation and degradation pathways of hydrocarbon gases in marine sediments and to characterize the involved microorganism in these processes. Two contrasting seep systems were explored for this purpose: the cold, methane-laden US Atlantic Margin (USAM) sediments and the hot, methane and higher hydrocarbon impregnated hydrothermal sediments of the Guaymas Basin. The unusual isotopic relationships for C2-C5 hydrocarbon at the Guaymas Basin were inconsistent with thermogenic cracking of larger molecules as well as other known abiotic reactions as their major source. A novel formation pathway was proposed and thereby confirmed by isotope tracer experiments under hydrous pyrolysis conditions and by thermodynamic computations. This pathway involves abiotic reduction of volatile fatty acids, whose carboxyl groups are isotopically equilibrated with ambient dissolved inorganic carbon in the hot subsurface of the basin. Additionally, microbial regulation of methane and higher hydrocarbons in these two seep settings was characterized by means of intact polar lipid (IPL) biomarkers in parellel with geochemistry and gene-based analyses. At the USAM, the diversity and abundance of archaeal IPLs were closely linked to the in situ microbial community composition and was well-constrained by methane flux and organic carbon content. In the hydrothermal sediments of Guaymas Basin, distribution of microbial lipids was indicative of the existence of mesophilic and thermophilic methane and potential higher hydrocarbon degraders, and was mainly controlled by in situ temperature.Dissertation380 260 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Tracing the effect of nutrient and carbon supply on the biosynthesis and composition of lipids from marine microbes(2017-11-13); ; ; The marine water column and the subsurface sediments remain among the least understood ecosystems on Earth. Particularly, microbial driven processes in marine environment, such as their activity, food-web strategies and ecological function within the marine realm are poorly understood. The aim of the presented research was to expand our knowledge on the microbial community structure and their lipid-based adaption mechanisms to nutrient limitation in the marine realm. To this end pure culture and environmental samples from different regions of the world were investigated using state-of-the-art analytical techniques. This dissertation provides important information on the biosynthesis of microbial lipids under energy limiting conditions, showing that microbes modify their lipid composition according to changing nutrient levels. Moreover, the detailed investigation of the proxy potential of selected microbial lipids, serves important information for future biomarker-based studies. Therefore, this dissertation increased the current knowledge of the microbial community and the physiologic mechanisms of microbes in the marine realm.Dissertation552 124