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Iron Reduction and Methanogenesis in Marine Subsurface Sediments from Helgoland

MPS-Authors

Gonzalez–Ortiz,  Aldo
Max Planck Society;

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Gonzalez–Ortiz, A. (2015). Iron Reduction and Methanogenesis in Marine Subsurface Sediments from Helgoland. Master Thesis, University of Bremen, Bremen, Germany.


Cite as: http://hdl.handle.net/21.11116/0000-0001-C447-2
Abstract
Methanogenesis and iron reduction are microbial–mediated processes of biogeochem- ical relevance. Due to thermodynamic reasons, they are deemed to occur in spatially separated zones in marine subsurface sediments—a phenomenon referred to as bio- geochemical zonation. Both processes have been observed to occur concomitantly in incubations of marine subsurface sediment from the Helgoland mud area amended with peptone. In this thesis, I developed three incubations with marine subsurface sediment from the Helgoland mud area from depths between 225–250 (HE406–4) and 250–275 (HE406–8) centimetres below the sea surface (cmbsf), and an analytical framework to relate the measured concentrations of CO 2 , CH 4 and Fe(II) to the content of dry sediment dynamically. In incubations with sediment from a depth of 250–275 cmbsf, the use of a defi ned amino acid mix (composed of alanine, glutamic acid, proline, leucine, and methionine) at a concentration of ca. 10 mM induced the performance of CH 4 in levels comparable to those found with peptone at a concentration of 1.7 g per litre. Iron reduction was observed in association to methanogenesis in incubations amended with the amino acid mix. However, the specifi c methanogenesis inhibitor 2–bromoethanesulphonate (BES) was shown to impair iron reduction, for reasons beyond the scope of this thesis. Furthermore, the study of the microbial community structure by T–RFLP in these incubations revealed complex interaction patterns infl uenced by the addition of the amino acid mix, ferrihydrite, and BES. Variation between incubation bottles and diff erent incubation days were shown to be relevant as well. In conclusion, the use of the amino acid mix and the analytical methods developed provide a more quantitative approach for further incubation experiments.