Staff

Carsten Schubert

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Prof. Dr. Carsten Schubert

Department Surface Waters Research & Management

About Me

Projects
See projects on the webpage of the group Biogeochemistry


Research interests
•    Genesis, aerobic and anaerobic oxidation of methane in freshwater systems
•    Understanding food chains using stable isotopes
•    Isotopic (C,N,O,H) and organic geochemical investigations in respect to the cycling of nutrients (C,N) and the preservation/degradation of organic matter
•    Investigation of the nitrogen cycle (amino-sugars and amino acids as the main nitrogen compounds in organisms, stable isotopes on bulk and single compounds to understand food webs)
•    Determination and use of biomarkers in organic materials (sediments, plankton, and bacteria), especially alkenones, n-alkanes, fatty-acids, alcohols, sterols, ether-lipids and lignin for identifying key processes taking place today or in the past (palaeo-reconstructions)

 

Teaching

  • Lecture: Isotopes and Biomarkers in Biogeochemistry at ETH Zürich
  • Laboratory: Isotopes and Biomarkers in Biogeochemistry at ETH Zürich


PhD students

  • 2021-    Bastiaan Drost, Blue Green Biodiversity Project
  • 2020-    Grégoire Saboret, Isotopes and food chains

Postdocs in research group

  • 2021-            Maja Illic, Blue Green Biodiversity
  • 2021-2022    Sigrid vanGrinsven, Methanogenesis and dependence of organic material

Field experience

8 Oceanographic cruises (2 times as chief scientist) to the Arctic, Pacific Ocean, Atlantic Ocean, Black Sea and numerous lake sampling campaigns


Reviewer for Journals, Funding agencies

Nature, Science, Nature Communications, Nature Climate Change, Nature Geosciences, Scientific Reports, Geology, Marine Chemistry, Palaeoceanography, Geochimica et Cosmochimica Acta, Journal of Geophysical Research, Marine Geology, Limnology & Oceanography, Environmental Science & Technology, Organic Geochemistry, Gcubed, Global Biogeochemical Cycles, FEMS Microbial Ecology, Chemical Geology, Journal of Earth System Science, Journal of Great Lakes Research, Archives of Microbiology, Aquatic Microbial Ecology, Aquatic Geochemistry, Continental Shelf Research, Journal of Chromatography A, Environmental Microbiology, Ecological Monographs

Reviewer for Funding agencies

ERC Grants, European Science Foundation
DFG, German research foundation
NSF, National Science Foundation, USA
NWO Earth and Life Science, Dutch research council
SNF, Swiss National Science Foundation
Academy of Finland
Fondecyt, Chilean national research funding
U.S.-Israel Binational Science Foundation
NERC, National Science Foundation, UK
Darwin Center for Biogeosciences (Netherlands)
American Chemical Society Petroleum Fund
French National Research Agency

Publications
Eawag Publications

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Curriculum Vitae

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Publications

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Purple sulfur bacteria fix N2 via molybdenum-nitrogenase in a low molybdenum Proterozoic ocean analogue

Biological N2 fixation was key to the expansion of life on early Earth. The N2-fixing microorganisms and the nitrogenase type used in the Proterozoic are unknown, although it has been proposed that the canonical molybdenum-nitrogenase was not used due to low molybdenum availability. We investigate N2 fixation in Lake Cadagno, an analogue system to the sulfidic Proterozoic continental margins, using a combination of biogeochemical, molecular and single cell techniques. In Lake Cadagno, purple sulfur bacteria (PSB) are responsible for high N2 fixation rates, to our knowledge providing the first direct evidence for PSB in situ N2 fixation. Surprisingly, no alternative nitrogenases are detectable, and N2 fixation is exclusively catalyzed by molybdenum-nitrogenase. Our results show that molybdenum-nitrogenase is functional at low molybdenum conditions in situ and that in contrast to previous beliefs, PSB may have driven N2 fixation in the Proterozoic ocean.
Philippi, M.; Kitzinger, K.; Berg, J. S.; Tschitschko, B.; Kidane, A. T.; Littmann, S.; Marchant, H. K.; Storelli, N.; Winkel, L. H. E.; Schubert, C. J.; Mohr, W.; Kuypers, M. M. M. (2021) Purple sulfur bacteria fix N2 via molybdenum-nitrogenase in a low molybdenum Proterozoic ocean analogue, Nature Communications, 12, 4774 (12 pp.), doi:10.1038/s41467-021-25000-z, Institutional Repository

Amino acid and chlorin based degradation indicators in freshwater water systems

Lakes cover a global area that is about 35 times smaller than the oceans, but carbon burial in lakes and oceans are on the same order of magnitude. Hence, understanding the processes for such high organic carbon burial in lacustrine systems is essential. We applied proxies typically used for marine environments including amino acid (AA) content and their nitrogen stable isotope composition to the water columns and sediments of three lakes that differ in their trophic states and depositions rates of sedimentary terrestrial organic matter. Additionally, we used carbon isotope fingerprinting of AAs to characterise their sources and fates. We show that this set of proxies tracks sources and degradation processes in eutrophic lakes with high sedimentary total organic carbon and nitrogen content. Those lakes also have a high total hydrolysable amino acid (THAA) content as well as higher pigment concentrations. While the Chlorin degradation Index (CI) showed increasing values with depth, the patterns were less consistent for the Degradation Index (DI). In general, all parameters failed to describe degradation in the most oligotrophic lake due to the very low organic carbon and nitrogen content in the sediment. We show that AAs are mostly of autochthonous origin and that AA contribute 5-45 % to the organic material in plankton, POM, and sediment. Proxies based on AA for bacterial reworking (ΣV) or trophic level (TL) showed increasing values in the water column but relatively stable values in the sediments. Furthermore, we show that methanotrophic bacteria led to increased values for the bacterial reworking proxy (ΣV) and extraordinarily low δ13C AA values (-30 to -60 ‰).
Stücheli, P. E.; Larsen, T.; Wehrli, B.; Schubert, C. J. (2021) Amino acid and chlorin based degradation indicators in freshwater water systems, Geochimica et Cosmochimica Acta, 304, 216-233, doi:10.1016/j.gca.2021.04.006, Institutional Repository

Anoxic chlorophyll maximum enhances local organic matter remineralization and nitrogen loss in Lake Tanganyika

In marine and freshwater oxygen-deficient zones, the remineralization of sinking organic matter from the photic zone is central to driving nitrogen loss. Deep blooms of photosynthetic bacteria, which form the suboxic/anoxic chlorophyll maximum (ACM), widespread in aquatic ecosystems, may also contribute to the local input of organic matter. Yet, the influence of the ACM on nitrogen and carbon cycling remains poorly understood. Using a suite of stable isotope tracer experiments, we examined the transformation of nitrogen and carbon under an ACM (comprising of Chlorobiaceae and Synechococcales) and a non-ACM scenario in the anoxic zone of Lake Tanganyika. We find that the ACM hosts a tight coupling of photo/litho-autotrophic and heterotrophic processes. In particular, the ACM was a hotspot of organic matter remineralization that controlled an important supply of ammonium driving a nitrification-anammox coupling, and thereby played a key role in regulating nitrogen loss in the oxygen-deficient zone.
Callbeck, C. M.; Ehrenfels, B.; Baumann, K. B. L.; Wehrli, B.; Schubert, C. J. (2021) Anoxic chlorophyll maximum enhances local organic matter remineralization and nitrogen loss in Lake Tanganyika, Nature Communications, 12, 830 (11 pp.), doi:10.1038/s41467-021-21115-5, Institutional Repository

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Files

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Address

E-Mail: carsten.schubert@eawag.ch
Phone: +41 58 765 2195
Fax: +41 58 765 2168
Address: Eawag
Seestrasse 79
6047 Kastanienbaum
Office: SL C18
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Expert on

isotopes, surface water

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