Ferromagnetic resonance of magnetite biominerals traces redox changes
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Date
2020-09-01
Publication Type
Journal Article
ETH Bibliography
yes
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Abstract
Redox variations govern a multitude of key geochemical and microbiological processes within lacustrine and marine systems, yet the interpretation of these geological archives can be limited because redox-sensitive microorganisms leave behind sparse fossil evidence. Here, we assess a biologically controlled magnetic proxy through investigation of a well-constrained sedimentary record covering a perturbation of redox-conditions driven by a complete trophic cycle in Lake Constance. Ferromagnetic resonance spectroscopy of sediments reveals strong uniaxial anisotropy, indicative of single-domain magnetite particles in intact or fragmentary chain arrangements, which are an unambiguous trait of magnetotactic bacteria (MTB) and their magnetofossil remains. We show that biogenic magnetite formed intra-cellularly in MTB faithfully records changing redox-conditions at or close to the sediment water-interface. Biogenic magnetite within sedimentary records points to the proliferation of MTB parallel to a decline in water column dissolved oxygen and the formation of sulfidic surface sediments in Lake Constance associated with an episode of eutrophication (1955–1991). We conclude that magnetofossils may serve as a sensitive geological proxy to reconstruct dynamic redox-changes along the sediment-water interface and bottom waters.
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Publication status
published
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Book title
Journal / series
Volume
545
Pages / Article No.
116400
Publisher
Elsevier
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Edition / version
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Software
Geographic location
Date collected
Date created
Subject
magnetotactic bacteria; magnetofossil; anoxia; sediment; redox gradient; eutrophication
Organisational unit
03868 - Eglinton, Timothy I. (emeritus) / Eglinton, Timothy I. (emeritus)
03734 - Jackson, Andrew / Jackson, Andrew
Notes
Funding
165851 - The origin and legacy of microbially-derived magnetism in marine sediments (SNF)