Bildung authigener Mineralien in Verbindung mit mikrobieller Aktivität in eisenhaltigen Sedimenten, Lake Towuti
Hydrogeologie, Hydrologie, Limnologie, Siedlungswasserwirtschaft, Wasserchemie, Integrierte Wasserressourcen-Bewirtschaftung
Mikrobielle Ökologie und Angewandte Mikrobiologie
Zusammenfassung der Projektergebnisse
Siderites (FeCO3) were recovered from 50 different depths over a 100 m drill core covering about 500’000 years of sediment history. Also, macroscopically visible vivianite crystals were picked by hand from distinct horizons located between 20 and 50 m sediment depth. These minerals were investigated to infer mineral formation and recording of microbial processes. SEM and TEM imaging showed that siderites grow from micritic phases into mosaic monocrystals, developing into aggregates with increasing burial depth. Green rust (Fe6[OH]12⋅[CO3⋅2H2O]) and magnetites (Fe3O4) were observed interlaced within siderites, suggesting successive diagenetic phases related to iron reduction. Elemental mapping revealed Mn/Fe zonations with Mn enrichment in the center of the minerals, reflecting diagenetic evolution of pore water chemistry. Intervals with persistent light δ13C and δ56Fe compositions were interpreted to reflect long periods of bottom water anoxia with little siderite formation in the sediment. The concomitance of vivianites (Fe2[PO4]2⋅8H2O) argued for variable sediment sorption processes arising from fluctuations in the depth of the water column oxycline. Under anoxic conditions, diffusion of dissolved iron, phosphate and methane from underlying sediments leads to vivianite formation at the water-sediment interface with inclusion of specific minerals formed in the water column (e.g. millerite, siderite, detrital goethite). We observe contrasting siderite-rich intervals that lack vivianite, which point toward bottom water oxygenation with increased burial of amorphous Fe3+. After burial, this amorphous Fe3+ is reduced and reacts with the pore water DIC to form siderite with heavy δ13C but light δ56Fe compositions. The siderite δ18O compositions are presently unexplained, but could reflect the influence of river discharges and evaporation on the water body. We therefore consider siderite isotopic compositions to reflect intricate lacustrine processes of redox fluctuations and diagenesis. Because hydrated iron phases and smectites tend to sorb chemical solutions and produce artifacts during sample preparation, we renounced to image microbe/mineral interactions related to EPS, biofilms and cell membranes and focused on neoformed minerals only. DNA fingerprinting was performed in shallow sediments providing relevant insights into the influence of microbial activity on short-term sorption processes. Additionally, the Joint Genome Institute provided us three metagenomes at no cost, as part of their “Rare Biosphere” Program. The amount of data that has now become available by far exceeds our expectations. The complete characterization of the deep biosphere in terms of phylogenetics and metagenomics is the present focus of a grouped proposal led by our Canadian collaborators from the UBC. These data are currently being produced free of charge at the Joint Genome Institute.
Projektbezogene Publikationen (Auswahl)
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2016. Geomicrobiological features of ferruginous sediments from Lake Towuti, Indonesia. Frontiers in Microbiology 7, 1007
Vuillemin A., Friese A., Alawi M., Henny C., Nomosatryo S., Wagner D., Crowe S.A., and Kallmeyer J.
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2016. The Towuti Drilling Project: Paleoenvironments, biological evolution, and geomicrobiology of a tropical Pacific lake. Scientific Drilling 21, 29-40
Russell J.M., Bijaksana S., Vogel H., Melles M., Kallmeyer J., Ariztegui D., Crowe S., Fajar S., Hafidz A., Haffner D., Hasberg A., Ivory S., Kelly C., King J., Kirana K., Morlock M., Noren A., O'Grady R., Ordonez L., Stevenson J., von Rintelen T., Vuillemin A., Watkinson I., Wattrus N., Wicaksono S., Wonik T., Bauer K., Deino A., Friese A., Henny C., Imran, Marwoto R., Ngkoimani L.O., Nomosatryo S., Safiuddin L.O., Simister R., and Tamuntuan G.
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2017. Preservation and significance of extracellular DNA in ferruginous sediments from Lake Towuti, Indonesia. Frontiers in Microbiology 8, 1440
Vuillemin A., Horn F., Alawi M., Henny C., Wagner D., Crowe S., and Kallmeyer J.
