The legacy of hurricanes Katrina and Rita on land has been one of human devastation and long-term damage to the infrastructure of communities along the northern Gulf of Mexico. In addition, these hurricanes had major impacts on offshore regions of the shelf and slope. A multi-institution, rapid-response effort investigated the immediate effects of the storms on the seabed off the Louisiana coast. These studies revealed intense reworking of surface sediment layers during the storm passage and re-deposition of materials following the hurricanes over a broad area of the shelf and slope. The pattern of deposition varied significantly along the region between the Mississippi and Atchafalaya rivers, depending on both the characteristic of the shelf and the paths of the storms. Geochemical tracers indicate the origin of the materials in the post-hurricane layers was predominantly local sediments mobilized by the intense wave activity during the storms. The combined impact of the hurricanes was a massive disturbance of benthic communities throughout the region, including marked erosion of the seabed in the shallower regions of the shelf and elevated deposition of sediments in the deeper regions. The total amounts of sediment, carbon and nitrogen re-deposited following the storm far exceeded the combined annual inputs of these materials by the Mississippi/Atchafalaya Rivers. The characterization of these storm deposits provides an opportunity to investigate the history of hurricane activity in the recent past based on the sedimentary record preserved in this region.

The decomposition of marine plankton in two-chamber, seawater-filled microbial fuel cells (MFCs) has been investigated and related to resulting chemical changes, electrode potentials, current efficiencies, and microbial diversity. Six experiments were run at various discharge potentials, and a seventh served as an open-circuit control. The plankton consisted of a mixture of freshly captured phytoplankton and zooplankton (0.21 to 1 mm) added at an initial batch concentration of 27.5 mmol liter ؊1 particulate organic carbon (OC). After 56.7 days, between 19.6 and 22.2% of the initial OC remained, sulfate reduction coupled to OC oxidation accounted for the majority of the OC that was degraded, and current efficiencies (of the active MFCs) were between 11.3 and 15.5%. In the open-circuit control cell, anaerobic plankton decomposition (as quantified by the decrease in total OC) could be modeled by three terms: two first-order reaction rate expressions (0.79 day ؊1 and 0.037 day ؊1 , at 15°C) and one constant, no-reaction term (representing 10.6% of the initial OC). However, in each active MFC, decomposition rates increased during the third week, lagging just behind periods of peak electricity generation. We interpret these decomposition rate changes to have been due primarily to the metabolic activity of sulfur-reducing microorganisms at the anode, a finding consistent with the electrochemical oxidization of sulfide to elemental sulfur and the elimination of inhibitory effects of dissolved sulfide. Representative phylotypes, found to be associated with anodes, were allied with Delta-, Epsilon-, and Gammaproteobacteria as well as the Flavobacterium-Cytophaga-Bacteroides and Fusobacteria. Based upon these results, we posit that higher current efficiencies can be achieved by optimizing plankton-fed MFCs for direct electron transfer from organic matter to electrodes, including microbial precolonization of high-surface-area electrodes and pulsed flowthrough additions of biomass.

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Prevention of wellbore CO 2 leakage is a critical component of any successful carbon capture, utilization, and storage program. Sporosarcina pasteurii is a bacterium that has demonstrated the potential ability to seal a compromised wellbore through the enzymatic precipitation of CaCO 3. Here we investigate the growth of S. pasteurii in a synthetic brine that mimics the Illinois Basin and on Mt. Simon sandstone encased in Class H Portland cement under high pressure and supercritical CO 2 (P CO2) conditions. The bacterium grew optimum at 30 o C compared to 40 o C under ambient and high pressure (10 MPa) conditions; and growth was comparable in experiments at high P CO2. Sporosarcina pasteurii actively induced the biomineralization of CaCO 3 polymorphs and MgCa(CO 3) 2 in both ambient and high pressure conditions as observed in electron microscopy. In contrast, abiotic (non-biological) samples exposed to CO 2 resulted in the formation of surficial vaterite and calcite. The ability of S. pasteurii to grow under subsurface conditions may be a promising mechanism to enhance wellbore integrity.