The University of Southampton
University of Southampton Institutional Repository

Biotic and abiotic alteration of hydrothermal sulphides at the seafloor

Mueller, Moritz (2009) Biotic and abiotic alteration of hydrothermal sulphides at the seafloor University of Southampton, Faculty of Engineering Science and Mathematics, School of Ocean and Earth Science, Doctoral Thesis , 208pp.

Record type: Thesis (Doctoral)

Abstract

When active venting has ceased, reduced minerals in hydrothermal mounds and sediments continue to provide an inorganic energy source for chemolithotrophic microbes. This research focuses on the nature of microbially-mediated metal transformations in hydrothermal sediments during sulphide alteration and their impact on the ultimate fate of hydrothermal sulphides on the seafloor. The core studied is more seawater altered than other cores studied at TAG and provides an insight into the bacterial and archaeal communities as well as the geochemical processes taking place in highly altered metalliferous sediments. This study combines geochemical approaches with microbiological and organic biomarker measurements within the suboxic transition zone of sulphidic sediments to characterise the reactions and microbial communities present. This integrated approach demonstrates that (a) there is biogeochemical zonation within the sediment sequence with distinct microbial communities present at the sulphide-oxic seawater transition, (b) the microbes identified are associated with Fe and S redox cycling, (c) Marinobacter sp. are dominant at the sulphide interface. There is a significant shift in the microbiological community across the redox transition zone in these sulphidic sediments. The microbial assemblage of the suboxic transition zone is dominated by Bacillus sp. which are microaerophilic whereas the sulphide layer assemblage is dominated by Marinobacter sp. which are Fe oxidisers. Based on biomarker assemblages and genetic analyses, archaeal (and to a certain degree bacterial) communities are comparable to other hydrothermal settings despite the low biomass present. Processes inferred to be important in this sediment include the S, Fe and N cycle, all potentially coupled to the release and uptake of a range of transition metals. Significant recycling of redox active species occurs in the suboxic transition zones present in the sediment core. Uranium concentrations are low compared with other less altered sulphidic hydrothermal sediments, and U is associated with the upper regions of the suboxic transition zone and is associated with enrichment of a suite of other transition metals (e.g. Cu, Mo, As and V). Massive electrodes were constructed from CuFeS2 (from Ireland and TAG) and FeS2 (from TAG) and studied in oxygenated artificial seawater under circumneutral conditions using electrochemical methods. The results can be explained by existing hypotheses about pyrite and chalcopyrite oxidation and their oxidation products. The oxidation status of Cu in covellite could be identified as Cu+1. Impurities found (as expected because natural samples were used) have no effect on the electrochemical behaviour of the electrodes. The impact of Marinobacter sp. on sulphide alteration was studied in detail using an electrochemical approach. The results demonstrate that Marinobacter aquaeolei enhances the rates of oxidation. Marinobacter species seem to be of special importance for weathering reactions on the seafloor and in hydrothermal settings like the TAG area.

PDF Mueller_2009_PhD.pdf - Other
Restricted to Registered users only
Download (4MB)

More information

Published date: 2009
Organisations: University of Southampton

Identifiers

Local EPrints ID: 69029
URI: http://eprints.soton.ac.uk/id/eprint/69029
PURE UUID: bd81869d-90ff-474d-b0e4-e772e92c8573

Catalogue record

Date deposited: 14 Oct 2009
Last modified: 19 Jul 2017 00:14

Export record

Contributors

Author: Moritz Mueller

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×