Microbial Substrate Use at Sites of Continental Serpentinization: The Tablelands, NL, CAD and the Cedars, CA, USA

Friday, 19 December 2014: 11:50 AM
Penny L Morrill1, Amanda Rietze2, Lukas Kohl3, Sarah Miles2, Heidi Kavanagh2, Alison Cox2, William J Brazelton4, Shino Ishii5, Barbara Sherwood Lollar6, Matthew O Schrenk7, Kenneth H Nealson8, Susan E Ziegler1, Shuhei Ono9, David T Wang10, Susan Q Lang11 and Emily Cumming2, (1)Memorial University of Newfoundland, St John's, NL, Canada, (2)Memorial University of Newfoundland, St John's, Canada, (3)Memorial University of Newfoundland, St John\'s, Canada, (4)University of Utah, Salt Lake City, UT, United States, (5)J. Craig Venter Institute, La Jolla, CA, United States, (6)University of Toronto, Toronto, ON, Canada, (7)East Carolina University, Greenville, NC, United States, (8)University of Southern California, Los Angeles, CA, United States, (9)MIT, Cambridge, MA, United States, (10)Massachusetts Institute of Technology, Cambridge, MA, United States, (11)University of South Carolina Columbia, Columbia, SC, United States
Ultra-basic reducing springs at continental sites of serpentinization act as portals into the biogeochemistry of a subsurface ultramafic environment rich in hydrogen and methane gases. Field data and results from substrate addition microcosm experiments will be presented from two contrasting continental sites of serpentinization: the Tablelands, NL, CAN and The Cedars, CA, USA both Phanerozoic in age. These continental sites share geochemical characteristics that make these environments challenging for life, such as high pH, low Eh, scarce electron acceptors, and limited dissolved inorganic carbon for autotrophic growth. However, microbiological analyses have demonstrated that life does indeed exist in these environments. While environmental genomic studies indicated the potential metabolic capabilities of microorganisms in the sites, actual microbial metabolic activities in these environments remain unknown. To expand the understanding of biogeochemistry of the sites, we are conducting studies focusing on chemical and isotopic measurements, carbon substrate utilization, energy sources, and metabolic pathways of the microorganisms. Thus far, in situ geochemical data suggests that the methane from the Tablelands is primarily non-microbial, while the methane from The Cedars likely has some microbial contributions. To date, substrate addition microcosm experiments show no microbial production of methane from Tablelands’ water and sediments. However, microbial carbon monoxide utilization has been observed in Tableland microcosms, but not in The Cedars microcosms. These results demonstrate how geochemistry and substrate addition experiments can be complementary for the determination of the processes favored at these continental sites of serpentinization.