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- Hinrichs Lab - MARUM-B2
Hinrichs Lab - MARUM-B2
MARUM-B2 Simulation of biogeochemical processes in the marine subsurface: understanding carbon-flow and identification of process-specific biosignatures
| Duration: | July 2005 - June 2009 |
| Funding: | Deutsche Forschungsgemeinschaft (DFG) DFG-Research Center "Ocean Margins - Research Topics in Marine Sciences for the 21st Century |
| Principal Investigator(s): | Kai-Uwe Hinrichs (MARUM/Universität Bremen), T. Ferdelman (MARUM/Max-Planck-Institut für marine Mikrobiologie, Bremen), Matthias Zabel (MARUM/Universität Bremen) |
| Involved scientists in the Hinrichs Lab: | Solveig Bühring, Marcus Elvert, Verena Heuer, Tobias Goldhammer, Yu-Shih Lin |
| Partners: | Dr. N. Gussone (MARUM/Universität Bremen), Prof. Dr. Andreas Mackensen (Alfred Wegner Institut, Bremerhaven), Prof. Dr. Jörn Peckmann (MARUM/Universität Bremen) |
Abstract
Microbially mediated diagenetic processes ultimately control whether sedimentary carbon is buried or reentering the oceanic carbon cycle. Our current understanding of processes and microorganisms in deeply buried sediments is, at best, rudimentary. The primary goals of this project was to identify geochemical signatures of biological processes (biosignatures) in situ and track the responses of microbial communities to their chemical environment. Through experimental studies of different terminal electron-accepting processes, such as sulfate reduction, iron reduction and methanogenesis in microcosms with natural microbial communities from a variety of deeply buried continental margin sediments, we compared the microbial community structures and pathways of carbon degradation and seeked to identify process-specific geochemical biosignatures. Specifically, we addressed the following questions:
1. To what degree does geochemistry dictate the community structure of sedimentary microbial ecosystems? Understanding the relationship between geochemical conditions and the function and structure of microbial communities within the sediment has important ramifications for our understanding of element cycling in the ocean. In microcosm experiments with natural sediments, we monitored with culture-dependent molecular techniques how the community structure evolves in response to different, externally controlled electron-accepting processes.
2. What are the pathways of carbon fixation of novel uncultured prokaryotes that appear to dominate deeply buried continental margin sediments? In marine sediments uncultured lineages of bacteria and archaea are widespread and might use diverse anaerobic respiration pathways and electron acceptors (sulfate, metals and nitrogen species). In experiments, we added selected inorganic electron acceptors to stimulate growth of these lineages in different ways. We used quantitative and qualitative molecular surveys based on lipids and rRNA in combination with stable isotope labeling techniques to evaluate the growth response of these uncultured
lineages and to follow the uptake of carbon by different phyla as a first step towards understanding their physiology.
3. Do mineral and isotopic signatures of iron, oxygen, and sulfur species record process-specific information? In order to gain a better understanding of sedimentary biogeochemical processes in situ, we explored the potential of geochemical techniques that are not influenced by perturbations going along with the dramatic change of pressure, redox conditions, and temperature during sediment core retrieval. We were particularly interested in the oxygen isotopes (delta 18O) in phosphate, sulfate and ferric iron oxides/oxyhydroxides that have a high potential to carry process-specific information.
Our investigative techniques included tools from microbiology, organic and inorganic geochemistry, and mineralogy, e.g.: (i) simulation of sedimentary biogeochemical processes (iron and sulfate reduction, methanogenesis) in controlled microcosms experiments; (ii) molecular techniques to study microbial diversity,i.e. analysis of intact polar lipids and SSU 16S rRNA; (iii) quantitative and isotopic analyses of key metabolites and lipids; (iv) isotope labeling techniques to study carbon flow through microbial ecosystems; (v) quantitative, qualitative, and stable isotopic (C, O, S, (Fe)) analysis of dissolved and solid-phase chemical species.
This project is followed up by MARUM GB3.
Microbially mediated diagenetic processes ultimately control whether sedimentary carbon is buried or reentering the oceanic carbon cycle. Our current understanding of processes and microorganisms in deeply buried sediments is, at best, rudimentary. The primary goals of this project was to identify geochemical signatures of biological processes (biosignatures) in situ and track the responses of microbial communities to their chemical environment. Through experimental studies of different terminal electron-accepting processes, such as sulfate reduction, iron reduction and methanogenesis in microcosms with natural microbial communities from a variety of deeply buried continental margin sediments, we compared the microbial community structures and pathways of carbon degradation and seeked to identify process-specific geochemical biosignatures. Specifically, we addressed the following questions:
1. To what degree does geochemistry dictate the community structure of sedimentary microbial ecosystems? Understanding the relationship between geochemical conditions and the function and structure of microbial communities within the sediment has important ramifications for our understanding of element cycling in the ocean. In microcosm experiments with natural sediments, we monitored with culture-dependent molecular techniques how the community structure evolves in response to different, externally controlled electron-accepting processes.
2. What are the pathways of carbon fixation of novel uncultured prokaryotes that appear to dominate deeply buried continental margin sediments? In marine sediments uncultured lineages of bacteria and archaea are widespread and might use diverse anaerobic respiration pathways and electron acceptors (sulfate, metals and nitrogen species). In experiments, we added selected inorganic electron acceptors to stimulate growth of these lineages in different ways. We used quantitative and qualitative molecular surveys based on lipids and rRNA in combination with stable isotope labeling techniques to evaluate the growth response of these uncultured
lineages and to follow the uptake of carbon by different phyla as a first step towards understanding their physiology.
3. Do mineral and isotopic signatures of iron, oxygen, and sulfur species record process-specific information? In order to gain a better understanding of sedimentary biogeochemical processes in situ, we explored the potential of geochemical techniques that are not influenced by perturbations going along with the dramatic change of pressure, redox conditions, and temperature during sediment core retrieval. We were particularly interested in the oxygen isotopes (delta 18O) in phosphate, sulfate and ferric iron oxides/oxyhydroxides that have a high potential to carry process-specific information.
Our investigative techniques included tools from microbiology, organic and inorganic geochemistry, and mineralogy, e.g.: (i) simulation of sedimentary biogeochemical processes (iron and sulfate reduction, methanogenesis) in controlled microcosms experiments; (ii) molecular techniques to study microbial diversity,i.e. analysis of intact polar lipids and SSU 16S rRNA; (iii) quantitative and isotopic analyses of key metabolites and lipids; (iv) isotope labeling techniques to study carbon flow through microbial ecosystems; (v) quantitative, qualitative, and stable isotopic (C, O, S, (Fe)) analysis of dissolved and solid-phase chemical species.
This project is followed up by MARUM GB3.