Investigation of Marine Sediment Microbial Populations in Microbial Fuel Cells

Many bacteria can convert chemical energy to electrical energy: they oxidize diverse organic substrates, transfer electrons to anodic electrodes and thus generate electricity in microbial fuel cells (MFCs). In the marine environment, microbial fuel cells termed either sediment or benthic microbial fuel cells, have been developed to generate power via anodic bacteria in the ocean sediment. Power is dependent upon enriched anodic bacteria that transport their electrons onto the anode. The marine-deployed MFC systems can provide renewable, harvested power to trickle charge batteries or other storage devices. Through power management systems these storage devices can power traditional electronic loads of interest. The systems have the promise to allow for long term deployment of in-water sensor and communications systems, providing decreased maintenance and increased operational capabilities.

At SSC Pacific, MFC prototypes have been tested and evaluated in a field environment to determine their potential to power devices such as acoustic arrays. Two prototype MFC systems specifically developed to facilitate examination of the temporal and spatial response of anodic bacteria in marine MFCs were deployed in the San Diego Bay over a 60-day time period. Both had identical cathodes, load electronics, and data acquisition devices. The two systems had different anode architecture; one was called the 'Eel' and the other the 'Octopus' (see below). Sampling of bacteria on, and/or adjacent to the graphite sheet anodes allowed for the determination of the most probable number (MPN) of iron-reducing bacteria over time. For the 'Eel', sediment cores were taken near, between, and 15 cm away from the anodes. The 'Octopus' MFC was constructed to allow sacrificial removal of anode material for direct swabbing of the anode.

Figure 1. Schematic of the ‘Eel’ and 'Octopus' MFC system designed to take bacterial samples. A. 'Eel' design, 10x30 cm sheet graphite electrodes on redwood backplane (not shown, see Figure 2) attached to electronic cabling. B. 'Octopus' design, 5x5 cm attached to electronic cabling. In both, the sealed electronics package lies directly on the ocean sediment. The graphite filament electrode is suspended in the marine water column to a float.		Figure 2. Microbial fuel cells designed specifically for bacterial sampling over time. 'Eel' MFC top (A) and bottom (B) viewpoints with backplane installed; C is the 'Octopus' MFC. A. Top view of the redwood board with holes drilled to enable sediment core sampling to occur adjacent to (outside holes), and ~2 cm away from the two anodes (center hole). B. Bottom view to visualize the two anodes placed 5.5 cm apart; placed for sampling in the space between the two anodes. C. 'Octopus' MFC; nine small 7x7 cm sacrificial anodes attached to an underwater deployable electronics package.

Capabilties:

• Molecular Biology/Microbiology Laboratory
• Pier facilities
• Diver support services
• Ocean engineering expertise

Further Information:

• Arias-Thode, Y.M., K. Richter, A. Wotawa-Bergen, D.B. Chadwick, J. Kan, and K. Nealson. 2011. Development of Microbial Fuel Cell Prototypes for Examination of the Temporal and Spatial Response of Anodic Bacterial Communities in Marine Sediments. IEEE OCEANS 2011, Santander, Spain, June 6-9, 2011. [in press]