nai

Project Progress

Project personnel participated in a research cruise on the Integrated Ocean Drilling Program’s drill ship (Joides Resolution) during Aug-Sep. 2010 and another 14 day research cruise during June 2011 using the ship R/V Atlantis and the remotely operated vehicle (ROV) Jason; both cruises were to study the sediment-buried basement (basaltic crust) biosphere. Participants on the June 2011 cruise included 3 NAI team members (including NAI postdoctoral fellow, Alberto Robador), 2 gradu-ate students and a middle school teacher from the island of Hawaii, serving underrepresented Ha-waiian and Pacific Islander families. This project utilized the long-term ODP borehole ‘CORK’ obser-vatories to collect clean samples of crustal fluids for geochemical, microbiological and ecological characterization (Fig. 1). 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 ca-pable suite of instruments for extracting, analyzing and sampling large volumes of fluids from the basement environment. An upgraded sampling system (Fig. 2) used during the summer 2011 cruise permitted the collection of large volumes of the most pristine fluids ever collected from the basaltic crust. We now have 4 years of time series geochemical and molecular biological data from this en-vironment.

We have also made substantial progress towards the characterization of microbial respiration activity in deep sub-seafloor habitats and the development of a high-pressure thermal gradient sys-tem to study the pressure and temperature response of microbial metabolism. A current prototype of the incubation device was already used during the past two cruises to the Juan de Fuca Ridge Flanks (2010 and 2011) and it is on a final developmental stage. Potential rates of sulfate reduction were detected in hydrothermal fluids from the upper ocean crust on the Juan de Fuca Ridge flanks and the physiological characterization of microorganisms as a function of temperature in the base-ment fluids revealed the coexistence of different sulfate reducing populations in the mesophilic to thermophilic range. Together, these observations confirm that basement fluids support microbial sulfate reduction and underscore the temperature control on the metabolic reactions and microbial community distribution in the upper basement’

An existing fluid sampling and sensor instrument (the GeoMICROBE) sled was substantially up-graded over the past year in anticipation for our summer 2010 research cruise to the Juan de Fuca Ridge flank (see 2010 Annual Report for brief description). The sled was recovered after a success-ful year-long deployment (Fig. 3) (Deployed June 2010 to CORK at U1301A), refurbished and then redeployed for another one-year deployment at a new CORK observatory (U1362A) on the Juan de Fuca Ridge flanks. We have completed fabrication of two out of three new GeoMICROBE sleds, with significant improvements, for the North Pond (flanks of the northern Mid-Atlantic Ridge) CORK ob-servatories to be installed during November, 2011.

Another component of our Deep Biosphere Project 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 (Fig. 4). As noted above during this years ROV cruise to the Juan de Fuca Ridge flank CORKs we were able recover the GeoMICROBE sled and other long-term (1 year) samplers (OsmoSamplers) with which we have been monitoring the transport of a suite of dissolved and colloid (fluorescent microspheres and fluorescently stained bacteria) in-jected into the deep sediment-buried basement during summer 2010. 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. Analyses of these samples for evidence of tracer break through is underway.