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Project Progress

Project personnel participated in 3 week research cruise to study the sediment-buried basement (basaltic crust) biosphere, using the ship R/V Atlantis and the remotely operated vehicle (ROV) Jason; participants included 3 NAI team members, 5 graduate students, 2 undergraduate students and 2 early-career high school teachers. This project utilized the long-term ODP borehole ‘CORK’ observatories to collect clean samples of crustal fluids for geochemical, microbiological and ecological characterization. Because water-rock reactions and associated microbial habitats vary with crustal temperature and age, we are comparing the geochemistry and molecular diversity in crustal fluids from multiple borehole observatories on the flanks of the Juan de Fuca Ridge (JFR), ranging in basement age (~1.24 to 3.5 my) and in basement temperature (~38° to ~65°C).

In support of these microbial geochemical studies, we have been developing an increasingly capable suite of instruments for extracting, analyzing and sampling large volumes of fluids from the basement environment. An existing fluid sampling and sensor instrument (the GeoMICROBE) sled was substantially upgraded over the past year in anticipation for our summer 2010 research cruise to the Juan de Fuca Ridge flank. The sled was successfully deployed for several days during the past summer (June, 2010) research cruise and then redeployed for a one-year deployment at the Juan de Fuca CORK 1301A. We are currently fabricating 3 new sleds, with significant improvements, for the North Pond (flanks of the northern Mid-Atlantic Ridge) CORK observatories to be installed in Fall 2011

These sleds combine innovative electronic and mechanical designs to draw basement fluid from several hundred meters below seafloor to the seafloor sled via inert PVDF (polyvinyl-difluoride) fluid delivery lines and past an aggressive set of sensors for key biogeochemical and physical parameters (Fig. 1; see also list of attributes below). Each sled is also equipped with a time-series, 48 port time-series fluid sampler for large volume fluid collection (500 ml each port) and/or in situ filtration (>10,000 ml each port), with or without in situ fixation or extraction. These sleds will support the data and sample needs of many researchers and students requiring real-time and/or large volume samples (10’s of ml to 10,000’s of ml).

Another component of our Deep Biosphere Projeccts involves the establishment of a three-dimensional, subseafloor, IODP observatory network in the northeastern Pacific Ocean, for initiation of a large-scale, large-term cross-hole experiments. In addition to co-I J. Cowen this is in collaboration with colleagues at UCSC (A. Fisher), U. of Miami (K. Becker), U. of Alaska (G. Wheat) and UCSB (J. Clark). This year we were able to finalize preparation for this tracer transport project (e.g., installation of 2 additional CORK observatories) and to initiate the actual tracer transport experiment by injecting a suite of dissolved and colloid (fluorescent microspheres and fluorescently stained bacteria) into the deep sediment-buried basement. The colloid tracers represent proxies for microorganisms and their recover at monitoring holes should provide unprecedented insight into the mobility and origin of microorganisms within this remote biosphere. Cowen participated in the 2-month IODP expedition (aboard the drilling ship R/V Joides Resolution) that initiated the experiment. The instrument sled described above will be collecting samples 2/month as part of the long-term program to monitor the CORKs for the appearance of the injected tracers.

Also, A. Robador, coordinated by co-I J. Cowen, has fabricated an advanced instrument for the incubation of liquid samples at ultra high pressures (1000 Bar) and temperature gradients (up to 150 °C) that allows discrete sampling during time-course experiments (Figure 5). The specific goals are the characterization of temperature and pressure as microbial physiological variables, as well as the quantification of relevant metabolic processes rates under energy limiting conditions. During the past cruise to the Juan de Fuca Ridge flanks (June, 2010) on board R/V Atlantis, A. Robador explored the correlation between active microbial metabolic processes in fluids from ocean crust and the physical parameters that characterize these habitats. Samples are currently being analyzed and preliminary results from measurements of potential rates of microbial heterotrophic metabolism (namely, hydrolysis rates of extracellular enzymes and bacterial sulfate reduction rates) will soon become available.