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.

Sediment depth is given in mbsf. #0 = the ion and corresponding MS2 data was observed but the peak was not quantifiable. Data are semiquantitative and result from peak areas of individual compound per gram of sediment, where the sum of peak areas of all intact polar lipids (IPLs)/g dry sediment in Sample 207-1257C-5R-2,130-140, is equivalent to 100%. Note that response factors of individual IPLs are not known; consequently the relative signal intensity is not necessarily equivalent to relative abundance.

Supplement to: Fredricks, Helen F; Hinrichs, Kai-Uwe (2007): Data Report: Intact membrane lipis as indicators of subsurface life in Cretaceous and Paleogene sediments from Sites 1257 and 1258. In: Mosher, DC; Erbacher, J; Malone, MJ (eds.) Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX, 207, 1-11