Mineralogical Signatures in Electrically Coupled Marine Sediments

Abstract:

‘Electric cable bacteria’ are organisms of the family Desulfobulbaceaethat exhibit a novel method of electron transport. Cells form conductive filaments that function like electric wires, transferring electrons over distances of more than 1 cm from deep sulfidic sediments to oxygen or other electron acceptors near the soil/water interface. The rate of electron transfer across redox boundaries far exceeds that of diffusion limited processes and generates pH gradients that can significantly influence geochemical reactions, leading to the formation of distinct mineralogical profiles unlikely to be created by abiotic means. Electrically coupled sediments are characterized by carbonate and iron sulfide dissolution reactions occurring at depth and formation of carbonate and metal oxide crusts at the surface, exhibiting a reverse pattern compared to conventional sediment geochemistry. Our research seeks to address the following questions:

1. How prevalent are electric cable bacteria in diverse environments?
2. How do biogeochemical conditions such as ion concentration influence mineral formation?
3. Do biogenic minerals participate in charge transfer?
4. What is the importance of electric charge transfer in the subsurface or other low energy habitats?
5. Can mineral banding patterns caused by cable bacteria activity be preserved in the geologic record?

With this research we hope to further elucidate the impact of biologically-induced electric fields on the mineralogy of sediments.