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.
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.
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.
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.
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.