The existence of significant bacterial populations in deep subseafloor sediments has been established over the last decade through the analysis of samples obtained from the Ocean Drilling Program (ODP). To date, core material analyzed for a range of microbiological studies has been obtained either using advanced piston coring (APC) or extended core barrel (XCB) technology and thus has been restricted to softer sediments.
Bacteria are thought to exist much deeper than samples currently analyzed (750 meters below seafloor [mbsf]), and further investigation will require sampling and analysis of more indurated sediments obtained using rotary core barrel (RCB) technology. Unlike APC and XCB cores, RCB core samples have variable outer diameters and do not fit tightly in the plastic core liners used by ODP. Thus, the outer layers of RCB cores are open to contamination and exposure to oxygen during coring, recovery, storage, and subsequent handling.
A hydraulic cutting system was developed to obtain a sample of the "pristine" inner core of the sample under sterile, anoxic conditions. In addition, as RCB samples are too hard to use intact core techniques, samples were powdered and slurried prior to further analysis. The cutting rig worked well on indurated sediments from Leg 180, the first ODP cruise in which RCB core samples have been used for a suite of microbiological analysis (activity measurements, enrichments, and enumeration) in indurated sediments. Data from these samples demonstrate culturable anaerobic bacteria and realistic rates of anaerobic bacterial activity (sulfate reduction, methanogenesis, and thymidine incorporation) in the deepest samples from the deep subseafloor biosphere analyzed to date for microbial populations (842 mbsf) and activities (800 mbsf). The new sample handling technique preserves the anoxia of the core with no evidence of contamination, and application of this new technique will permit microbiological investigation of deeper indurated deep-sea sediments.
1Wellsbury, P., Mather, I.D., and Parkes, R.J., 2001. Subsampling RCB cores from the western Woodlark Basin (ODP Leg 180) for microbiology. In Huchon, P., Taylor, B., and Klaus, A. (Eds.), Proc. ODP, Sci. Results, 180 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/180_SR/chap_175/175.htm>. [Cited YYYY-MM-DD]
2Department of Earth Sciences, University of Bristol, Bristol BS8 1RJ, United Kingdom. Correspondence author: peter.wellsbury@bris.ac.uk
Initial
receipt: 19 December 2000
Acceptance: 10 June 2001
Web publication: 27 August 2001
Ms 180SR-175