Recent discoveries indicate that microbes beneath the Earth's surface make up as much as half of all living material on our planet. One habitat for subsurface microorganisms is the volcanic rock that forms the ocean basins. These rocks cover at least fifty percent of the Earth's surface and are the most abundant rock types on Earth.  Low temperature (<100oC) hydrothermal ocean fluids circulate everywhere within these porous and permeable volcanic rocks, creating temperatures and chemical gradients that form plausible habitats for a variety of microorganisms.  In fact, there is growing evidence that indigenous communities of microbes extend throughout the immense volume of aging basement rocks underlying the global system of mid-ocean ridge flanks and ocean basins, making the volcanic rocks of the ocean basins the largest habitat on Earth.

    Outside of their presence, we currently know very little about the microorganisms living in basalt-hosted subsurface fluids.  Since most mid-ocean ridge flank and ocean basin basement is buried under thick, impermeable layers of sediment, the fluids circulating within the underlying ocean basement are usually inaccessible for direct studies.  However, Circulation Obviation Retrofit Kit (CORK) observatories affixed to Ocean Drilling Program boreholes offer an unprecedented opportunity to study biogeochemical properties and microbial diversity in circulating fluids from aging ocean basement.  Through our recently funded NSF Microbial Observatory grant, University of Hawaii colleagues Jim Cowen, Brian Glazer and I are exploiting new CORK observatories installed on the flanks of the Juan de Fuca Ridge in order to study the deep biosphere of the ocean basement.

    My group is currently studying the structure of basement microbial communities in the context of geochemical and physical conditions (e.g., inorganic and organic chemistry, temperature, Eh, pH).  We are relying on phylogenetic and functional gene marker-based methods to rapidly assess microbial community structure from a large number of samples.  We are phasing in metagenomic studies as we learn more about the variability in the system.  The in situ geochemical data is being used to guide enrichment culture efforts as well as in situ metabolic activity experiments, for which we are currently designing in situ incubation devices. 

The GeoMICROBE instrument and sampling array after first deployment off of the R/V Atlantis, August 2008.

Deployment of the DSV Alvin from the R/V Atlantis during cruise AT15-35, August 2008.

The DSV Alvin, August 2008.

Cool bottom creature.