Long-distance electron transport occurs globally in marine sediments
- 1NIOZ Royal Netherlands Institute for Sea Research, Department of Estuarine and Delta Systems, and Utrecht University, Korringaweg 7, 4401 NT Yerseke, the Netherlands
- 2Department of Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
- 3Greenland Institute of Natural Resources, Greenland Climate Research Centre, P.O. Box 570, Kivioq 5, 3900 Nuuk, Greenland
- 4Arctic Research Centre, Aarhus University, 8000 Aarhus, Denmark
- 5Department of Marine Sciences, University of Gothenburg, Carl Skottsberg gata 22B, 41319 Gothenburg, Sweden
Abstract. Recently, long filamentous bacteria have been reported conducting electrons over centimetre distances in marine sediments. These so-called cable bacteria perform an electrogenic form of sulfur oxidation, whereby long-distance electron transport links sulfide oxidation in deeper sediment horizons to oxygen reduction in the upper millimetres of the sediment. Electrogenic sulfur oxidation exerts a strong impact on the local sediment biogeochemistry, but it is currently unknown how prevalent the process is within the seafloor. Here we provide a state-of-the-art assessment of its global distribution by combining new field observations with previous reports from the literature. This synthesis demonstrates that electrogenic sulfur oxidation, and hence microbial long-distance electron transport, is a widespread phenomenon in the present-day seafloor. The process is found in coastal sediments within different climate zones (off the Netherlands, Greenland, the USA, Australia) and thrives on a range of different coastal habitats (estuaries, salt marshes, mangroves, coastal hypoxic basins, intertidal flats). The combination of a widespread occurrence and a strong local geochemical imprint suggests that electrogenic sulfur oxidation could be an important, and hitherto overlooked, component of the marine cycle of carbon, sulfur and other elements.