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School of the Earth, Ocean and Environment


We study: Aqueous biogeochemistry; water-rock-microbe interactions, particularly in hydrothermal and subsurface systems; stable (13C, 15N, 34S) and radiocarbon (14C) isotopes of organic molecules; serpentinization as a source of energy for microbes and the abiotic synthesis of organic molecules; past, present, and future cycling of carbon and nitrogen through the environment.  

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Water-rock-microbe interactions

The vast majority of prokaryotes on Earth live in subsurface environments, and their abundance and activity has important consequences for global biogeochemical processes. The impact of microbial communities in sedimentary habitats, or in hydrologically active oceanic crust, on the chemical exchange between global reservoirs remains poorly constrained however. One of our major interests is the exchange of carbon and energy between geological environments and the microbial communities inhabiting them.  

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Serpentinization Environments: Lost City

In serpentinization environments, the reaction of ultramafic rocks with water results in alkaline fluids containing high concentrations of abiogenic hydrogen, methane, short-chain hydrocarbons, and formate. These highly reactive systems are widespread on earth and are responsible for approximately 70% of the mid-ocean fluxes of hydrogen and methane to the ocean. Both gasses provide abundant thermodynamic energy to fuel chemolithoautotrophy. The extent to which they are utilized by microbial communities can, in turn, exert a strong influence on their fluxes to the ocean. The Lost City Hydrothermal Field (Mid-Atlantic Ridge, 30ºN), is the best studied example of an active low-temperature serpentinizing environment. Our research at this site has focused on identifying organic molecules that have been formed abiotically, characterizing the metabolisms of the microbes that call it home, and defining the source and fate of carbon that cycles through the system. 

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Serpentinization Environments: Continental  

 Serpentinization environments can also be found in continental environments, such as this location in Liguria, Italy. Along with collaborators, we are working to identify what abiogenic and biogenic processes take place in these lower temperature environments.

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New Methods!  

 There are approximately 2 x 1015 organic molecules in 1 mL of water, and each of those molecules carries with it structural and isotopic information. This data can be used to track the source and fate of carbon as it cycles through the environment. Developing new methods provides fresh insights. A current push in our laboratory is to isolate small polar organic molecules for isotope (13C, 14C) analysis. These molecules (e.g. organic acids) can be particularly important to carbon cycling in subsurface and anaerobic environments.