Abstract:
In 1997, a simple 'BioColumn' sampler was coupled to the CORK observatory at borehole 1026B to sample fluid chemistry, biomass and microbial community diversity (16S rRNA). The results demonstrated that the 65 degrees C fluids from the 3.5 My old sediment-buried ocean basement support a diverse Bacteria and Archaea community (Cowen et al. 2003, Science 299, 120-123). The large bore of the overpressured CORK body provided high unassisted flow rates through the BioColumn, but possessed the disadvantage of the unknown extent to which the basement fluids were altered by the chemically and biologically (e.g., biofilm community) reactive surface of CORK's steel pipe. Subsequently, new generations of CORKs have incorporated less reactive materials in the CORK body, the use of stainless steel or inert PVDF (Teflon-like) 0.5" ID fluid delivery lines (FDL) running continuously from basement depths to accessible ports at the seafloor, and multiple FDLs from distinct depth horizons within basement. Simultaneously, we have developed increasingly capable fluid sensor and sampling systems for both real-time (Mobile Pumping and Sampling System-MPSS) and long-term autonomous applications (GeoMICROBE sleds). Both incorporate strong efficient pumps to overcome the drag inherent in the 0.5" or smaller bore FDL, multiple sensors (e.g., flow rate, temperature, O2, pH and redox-voltametry chemistry), versatile multi-port large volume fluid collection and/or in situ filtration systems, integrating computer controller/software and non-contaminating (inert) plumbing. These combined developments now provide unparalleled opportunities for access to large volumes of pristine basement samples for geochemical and microbial ecology studies. The MPSS and GeoMICROBE will be described. The multi-year results of organic geochemical and microbial community studies from recent studies at CORK observatories (boreholes 1301A, 1362A 1362B) on the Juan de Fuca Ridge flank will be summarized.