We report results from the analysis of intact polar lipids (IPLs) in sediments from Ocean Drilling Program Sites 1257 and 1258. IPLs, constituting the cell membranes of living organisms, were detected in organic-lean sediments but not in underlying organic-rich black shales. Microbial activity in organic-lean sediments is likely due to sulfate-dependent oxidation of methane whereas difficulties detecting IPLs in black shales are interpreted to result from unfavorable signal-to-noise ratios due to low cell concentrations in combination with extremely high analytical noise created by uncharacterized organic matrix. IPLs found are consistent with a low-diversity community of archaea and bacteria. The concentrations of IPLs are more than one order of magnitude lower than those in Neogene deep subsurface sediments at the Peruvian margin, suggestive of significantly lower cell concentrations in Demerara Rise. This finding is consistent with inferred low rates of subsurface microbial activity.
1Fredricks, H.F., and Hinrichs, K.-U., 2007. Data report: intact membrane lipids as indicators of subsurface life in Cretaceous and Paleogene sediments from Sites 1257 and 1258. In Mosher, D.C., Erbacher, J., and Malone, M.J. (Eds.), Proc. ODP, Sci. Results, 207: College Station, TX (Ocean Drilling Program), 1–11. doi:10.2973/odp.proc.sr.207.112.2007
2(née Sturt), Woods Hole Oceanographic Institution, Department of Marine Chemistry and Geochemistry, Mail 4, Woods Hole MA 02543, USA. hfredricks@whoi.edu
3Organic Geochemistry Group, DFG-Research Center Ocean Margins and Department of Geosciences, University of Bremen, 28334 Bremen, Germany.
Initial receipt: 3 January 2006
Acceptance: 11 April 2006
Web publication: 8 March 2007
Ms 207SR-112