Long distance electron transport in marine sediments: Microbial and geochemical implications

Publication: Research - peer-reviewConference abstract for conference

Anaerobic oxidation of organic matter in marine sediment is traditionally considered to be coupled to oxygen reduction via a cascade of redox processes and transport of intermittent electron donors and acceptors. Electric currents have been found to shortcut this cascade and directly couple oxidation of sulphide centimeters down in marine sediment to the reduction of oxygen at the very surface1 . This electric coupling of spatially separated redox half-reactions seems to be mediated by centimeter long filamentous Desulfubulbus affiliated bacteria with morphological and ultra-structural properties suggesting that they are living electric micro cables. The mode of action of these organisms has major impacts on element cycling by redox processes, pH balances, mineral dissolution/precipitations, and electro migration of ions in marine sediment. The ability of Desulfubulbus filaments to bridge redox half-reactions in distant regions of the sediment leads to formation of electrical fields, which modifies ion transport. The local proton producing and proton consuming half reactions induces pH extremes that accelerate dissolution of iron sulphides and calcium carbonates in anoxic layers and promotes the formation of Mg-calcite and iron oxides in the oxic zone. Oxygen seems to be the major electron acceptor, and more than 40% of the oxygen consumption in sediments can be driven by long distance electron transfer from distant electron donors. The major e-donor is sulfide, which is oxidized to sulfate, and iron sulphides are the major sources for sulfide in the system. Procaryotes with the ability to perform long distance electron transmission may flourishes in marine sediments exposed to transient oxygen depletion, leaving distinct signatures of such events in the geological record.
Original languageEnglish
Publication year2013
Number of pages1
StatePublished

Conference

ConferenceIsme14
Number14
CountryDenmark
CityCopenhagen
Period19/08/1224/08/12

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