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Biogeochemical impact of cable bacteria on coastal Black Sea sediment

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  • Martijn Hermans, University of Utrecth, Holland
  • Nils Risgaard-Petersen
  • Filip JR Meysman, University of Antwerp, Belgien
  • Caroline P. Slomp, Utrecht University, Holland
Cable bacteria can strongly alter sediment biogeochemistry. Here, we used laboratory incubations to determine the potential impact of their activity on the cycling of iron (Fe), phosphorus (P) and sulfur (S). Microsensor depth profiles of oxygen, sulfide and pH in combination with electric potential profiling and fluorescence in situ hybridisation (FISH) analyses showed a rapid development (< 5 d) of cable bacteria, followed by a long period of activity (> 200 d). During most of the experiment, the current density correlated linearly with the oxygen demand. Sediment oxygen uptakewas attributed to the activity of cable bacteria and the oxidationof reduced products from the anaerobic degradation oforganic matter, such as ammonium. Pore water sulfide waslow (<5 μM) throughout the experiment. Sulfate reduction macted as the main source of sulfide for cable bacteria. Porewater Fe2C reached levels of up to 1.7mM during the incubations, due to the dissolution of FeS (30 %) and siderite, anFe carbonate mineral (70 %). Following the upward diffusion of Fe2C, a surface enrichment of Fe oxides formed. Hence, besides FeS, siderite may act as a major source of Fe for Fe oxides in coastal surface sediments where cable bacteria areactive. Using μXRF, we show that the enrichments in Fe oxides induced by cable bacteria are located in a thin subsurfacelayer of 0.3 mm. We show that similar subsurface layers enrichedin Fe and P are also observed at field sites where cable bacteria were recently active and little bioturbation occurs. This suggests that such subsurface Fe oxide layers, which are not always visible to the naked eye, could potentially be a marker for recent activity of cable bacteria
Sider (fra-til)5919-5938
Antal sider20
StatusUdgivet - 2020

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