Collaborative Research: Microbial carbon cycling and its interactions with sulfur and nitrogen transformations in Guaymas Basin hydrothermal sediments

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Overview: Hydrothermally active sediments in the Guaymas Basin are dominated by novel microbial communities that catalyze important biogeochemical processes in these seafloor ecosystems. This project will investigate genomic potential, physiological capabilities and biogeochemical roles of key uncultured organisms from Guaymas sediments, especially the high-temperature anaerobic methane oxidizers that occur specifically in hydrothermally active sediments (ANME-1Guaymas). The study will focus on their role in carbon transformations, but also explore their potential involvement in sulfur and nitrogen transformations. First-order research topics include quantifying anaerobic methane oxidation under high temperature,in situ concentrations of phosphorus and methane , and with alternate electron acceptors; sulfate and sulfur-dependent microbial pathways and isotopic signatures under these conditions; and nitrogen transformations in methane-oxidizing microbial communities, hydrothermal mats and sediments. Intellectual Merit: This integrated biogeochemical and microbiological research will explore the pathways of and environmental controls on the consumption and production of methane, other alkanes, inorganic carbon, organic acids and organic matter that fuel the Guaymas sedimentary microbial ecosystem. The hydrothermal sediments of Guaymas Basin provide a spatially compact, high-activity location for investigating novel modes of methane cycling and carbon assimilation into microbial biomass. In the case of anaerobic methane oxidation, the high temperature and pressure tolerance of Guaymas Basin methane-oxidizing microbial communities, and their potential to uncouple from the dominant electron acceptor sulfate, vastly increase the predicted subsurface habitat space and biogeochemical role for anaerobic microbial methanotrophy in global deep subsurface diagenesis. Further, microbial methane production and oxidation interlocks with syulfur and nitrogen transformations, which will be explored at the organism and process level in hydrothermal sediment microbial communities and mats of Guaymas Basin. In general, first-order research tasks (rate measurements, radiotracer incorporation studies, genomes, in situ microgradients) define the key microbial capabilities, pathways and processes that mediate chemical exchange between the subsurface hydrothermal/seeps and deep ocean waters. Broader Impacts: The Zephyr Education Foundation, with its unique marine science literacy and education program will collaborate in the design of an educational field exercise. The Foundation is located in Woods Hole and coordinates school class field trips that include participating in hands-on learning and discovery on the water and in the laboratory. The questions, techniques, and relevance of this research will be presented in a manner that promotes awareness and understanding. Sediment coring, comparisons of coastal sediments to original Guaymas Basin sample materials, and side scan sonar demos that illustrate the challenges of sea floor mapping (a very real problem in hydrothermal vent research) will be performed as part of seagoing class trips with the Zephyr Foundation 40-foot boat RV Minuteman in the coastal waters of Woods Hole. The Foundation will present this unit as part of their on-board, hands-on marine science field trip series that is delivered to approximately 1,000 students and their teachers per year. This outreach component expands the ongoing collaboration of the PIs with Zephyr-led outreach activities. Day-by-day cruise blogs, written, illustrated and posted by the PI for three recent Atlantis/Alvin cruises are used extensively for teaching and engaging classes at UNC at the undergraduate level (Extreme microbes seminar for freshmen of all fields, and Introduction to Oceanography for junior/senior science majors). The PI will write a daily cruise blog for the next Guaymas Basin cruise and make short (3 min) videos at sea for web site posting and classroom use.