There is growing evidence that a substantial sub-seafloor biosphere exists and that its chemical composition and associated microbial activity changes across the seafloor, especially in relation to mid-ocean ridge (MOR) environments, where new crustal material is formed and ages over time along the MOR flanks. While many aspects of these environments are being studied, and dedicated observatories have been established to examine the biological and chemical processes in such environments, there has been little study, and there is little understanding of how the composition of dissolved and particulate organic matter changes in these environments. A detailed examination of the composition of the dissolved and particulate organic material, and an examination of isotopic signatures of compound 'age' of the MOR flank subsurface (basement) fluids will provide much needed information on the biogeochemistry of these systems. The current project is designed to examine this aspect of sub-seafloor biogeochemistry using existing facilities funded through the International Ocean Drilling Program (IODP).
Investigators from the University of Illinois at Chicago will collect samples from the ODP Borehole Observatory Facility that exists at the Juan de Fuca Ridge, and will collect these samples in collaboration with other funded studies. The samples will be used to examine the composition of dissolved and particulate organic matter (DOM and POM) during the aging and transformation of the crust. The study will examine the organic geochemical properties of the fluids that range in age from less than 0.5 to 3.5 million years, and temperatures from about 38° to 270°C. The existing facility will allow for the collection of uncontaminated subsurface fluids and the interpretation of the chemical and isotopic results will allow examination of the impacts of chemical reactions and microbial processes on the fluids over time. The analysis of samples will be completed in collaboration with the University of Bremen, Germany, and samples co-collected by other investigators from the Universities of Hawaii and Washington will provide details concerning the bulk characteristics of the fluids, including their bulk organic characteristics. This research is adding an important component to the existing multidisciplinary research team of microbiologists, inorganic and organic geochemists already working at this location.
The research is guided by hypotheses relevant to the biogeochemistry of the basement biosphere. The hypotheses state that the lipid composition, and overall DOM composition, will reflect differences in biological assemblage and community structure, which depends on the temperature, chemistry, and hydrology of the basement crust, and that low molecular weight organic compounds (LMOM) are important sources of microbial productivity. It is further hypothesized that these LMOM are produced by both chemical and biological processes. Finally, it is hypothesized that the sub-seafloor processes are potentially important sources of sulfurized organic compounds that could be exported from the basement crust.
The organic geochemical analyses will include characterization of lipids as well as measurement of carbon isotopic composition. Dissolved organic matter (DOM) of basement fluid and bottom seawater will be analyzed by Fourier Transform-Ion Cyclotron Resonance-Mass Spectrometry (FT-ICR-MS), a very powerful technique that can resolve the complex nature of the DOM constituents and provide information on their exact elemental composition. This data will allow ?fingerprinting? of the source materials and allow examination of the evolution of DOM characteristics over time, which will help identify the relevant biogeochemical processes occurring in these environments.
Broader impacts: The scientific and societal impacts of this study relate to understanding the complex interactions that occur within the ocean-upper crust environment, a region of biogeochemical importance and high temporal and spatial variability. These interactions influence the inputs of chemicals to the deep ocean, and influence ocean chemistry. The proposed research will involve graduate and undergraduate students from the University of Illinois at Chicago, an urban campus with the majority of the science students being from under-represented groups. These students will be recruited for this project. The Principal Investigator will also contribute to the ?Teacher-at-Sea? outreach program at the University of Washington, and will interact electronically with students in the classrooms during these activities.
