Collaborative Proposal: Anoxic Sediment Diagenesis at the Sulfate-Methane Interface: Does a Novel Microbial Syntrophy Result in Enhanced POC Remineralization?

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Organic carbon breakdown, or diagenesis, within continental margin sediments is an important component of the C cycle in marine sediments as its extent controls long-term burial rates. Scientists from University of Southern California, California Institute of Technology and University of Hawaii have hypothesized a novel diagenetic process that may result in enhanced carbon remineralization when both sulfate and methane are present. Based on preliminary data, this process appears to occur at a localized horizon (cm's thick) where there is a microbial syntrophic relationship between anaerobic oxidation of methane by archaea and sulfate reducing bacteria. They will study sediments of the Santa Barbara Basin using high-resolution pore water measurements to create models of the chemical gradients and calculate diffusive flux values. The microbial community will be described using total microbial cell counts, archaeal and bacterial 16S rDNA and dsrAB-based community characterization, and fluorescent in situ hybridization (FISH). Manipulative incubation experiments will attempt to induce higher rates of carbon remineralization by the addition of sulfate and or methane. The importance of this unique zone in anoxic marine sediments has potentially significant implications to current modeling approaches to carbon diagenesis, interpretation of paleoproxy records in marine sediments and to general understanding of sediment microbial community ecology. Collaboration between a microbiologist and two geochemists will illustrate the synergies created by interdisciplinary research to a wide range of students including REU, middle and high school students, as well as the graduate and undergraduate students participating in this collaboration on cruises and in data analysis.