Schefuß, Enno

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Schefuß, Enno
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Schefuß, Enno

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    Fluid flow shapes microbial carbon cycling and mineral formation in shallow-water hydrothermal vents
    (2026-02-17)
    Maak, Joely Marie 
    ;
    Schefuß, Enno
    ;
    Sessions, Alex
    ;
    Schefuß, Enno
    Hydrothermal systems are characterized by steep thermal and chemical gradients, high metal and sulfur concentrations, and high variability in redox and pH. They provide natural laboratories to study microbial adaptation at the limits of habitability and offer insights into early Earth and potential extraterrestrial life. This dissertation investigates how hydrothermal fluid flow shapes microbial carbon cycling, ecosystem transfer, and mineral formation in shallow to transitional systems (8 to 210 m water depth) off Kueishantao (Taiwan) and Milos (Greece). By integrating lipid biomarkers with compound-specific δ13C, Δ14C, and δ2H analyses and mineralogical data, it explores carbon uptake pathways, fossil carbon incorporation, and membrane adaptation under contrasting physicochemical regimes. At Kueishantao, extreme sulfur-rich and acidic fluids promote chemoautotrophy dominated by sulfur-oxidizing Campylobacteria using the reductive tricarboxylic acid (rTCA) cycle, reflected in 13C-enriched fatty acids with minimal isotopic fractionation. These organisms are mostly responsible for vent carbon uptake (as shown by compound-specific 14C and 2H data). At Milos, spatial variations in diffusive versus advective fluid flow control redox conditions, microbial metabolism, and mineral formation. Sulfate-rich diffusive settings favor sulfate reduction linked to pyrite formation, whereas advective flow supports sulfide oxidation and elemental sulfur accumulation. Membrane adaptations, including elongation of bacterial ether lipids and methylation of archaeal tetraethers, reflect increasing environmental stress, particularly in metal-rich chimney deposits. Together, this work demonstrates that shallow hydrothermal systems sustain diverse and metabolically flexible microbial communities that are linked to local geochemical and mineralogical conditions.
    Dissertation
      49  95
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    Southern Patagonian climate the last 51,000 years : Insights from lipid biomarkers and their isotopes
    (2017-10-27)
    Hockun,Katja
    ;
    Diekmann, Bernhard
    ;
    Mollenhauer, Gesine
    ;
    Schefuß, Enno
    Laguna Potrok Aike (LPA) is situated in the core region of the Southern Hemispheric Westerlies (SHW) and provides an exceptional sedimentary archive to investigate the southern Hemisphere mid-latitude climate change over the last 51,000 years. This study gives the opportunity to reconstruct climatic and environmental conditions in an area sensitive to changes in polar and mid-latitude wind fields and hydrological regimes, and it provides insights into the complex interaction of terrestrial, marine and glacial environmental changes on glacial-interglacial timescales. Within the framework of this thesis the temperature and hydrological fluctuations of the maar lake were investigated using organic-geochemical proxies based on microbial membrane lipids (so called GDGTs) and compound-specific isotope analysis (d13C and dD) of plant-wax derived n-alkanes of different origins, respectively.
    Dissertation
      290  108