Table 1.

Geochemical and cell enumeration for SIP-NanoSIMS incubations

DIC, mMδ13C-DIC, ‰CH4/Ar, ‰δ13C-CH4, ‰δ2H-CH4, ‰Cells, g (rock)Total cellsPercent active
Lithology13C source, 1.5 mM15N source, 0.15 mMH2, 15%AAAAAAA
Shale - 8L4 (1,606 mbsf)0.36nm−0.46nmnmnmnmnmnmnm770nmnmnmnm
MeAm.Y0.280.100.66−1.240.20.3nmnmnm8511,5481E + 051E + 05ndnd
MeAm.0.302.314.624.800.10.3nmnmnm1535,8732E + 046E + 05526
MeAm.Am.Y0.510.728.325.720.10.2nmnmnm1,205951E + 051E + 04061
MeAm.Am.0.280.40−2.862.450.10.2nmnmnm26,7171,6643E + 062E + 05nd33
MeOHAm.Y0.740.69123.87430.030.10.2nmnmnm5397,5035E + 041E + 06nd78
MeOH0.091.166.43261.940.20.1nmnmnm1,9481,9672E + 052E + 05025
Coal - 15R3 (1,921 mbsf)0.16nm−10.33nmnmnmnmnmnmnm60nmnmnmnm
MeAm.Y0.060.07−6.00−3.771.15.5−42.8−46.1−170.4692637E + 023E + 0356
MeAm.0.040.23−16.19−7.200.88.6−57.2−55.7−198.221*70,3631E + 029E + 05061
MeAm.Am.Y0.020.0388.7720.100.84.5−42.3−55.0−144.137*5293E + 027E + 031419
MeAm.Am.0.110.03108.0655.791.08.1−58.0−58.8−158.24,86434*4E + 044E + 0274
MeOHAm.Y0.060.0819.09−6.462.45.4−49.7−52.9−96.532*2684E + 024E + 03ndnd
MeOH0.070.05−15.1426.671.23.8−57.5−56.6bd7,69311,0466E + 041E + 05033
Mixed - 19:25R (1,950–2,000 mbsf)0.16nm4.29nmnmnmnmnmnmnm22,200nmnmnmnm
MeAm.Y1.481.385.633.350.21.4nmnmnm32*24*8E + 027E + 02ndnd
MeAm.0.901.975.726.850.12.0nmnmnm24437E + 021E + 03nd8
MeAm.Am.Y0.980.9738.4537.730.10.5nmnmnm17*13*6E + 025E + 02711
MeAm.Am.1.731.7948.63327.560.10.1nmnmnm421309E + 025E + 03ndnd
MeOHAm.Y1.541.766.3214.870.22.2nmnmnm16*2715E + 021E + 04nd37
MeOH1.831.969.4244.640.42.2nmnmnm14*2,6925E + 021E + 0515100
  • Geochemical summary of incubations by lithology and substrates added [MeAm., methylamine (tan); MeOH, methanol (gray); Am., ammonium], with 2H2O only (no C or N added) provided as a background sample, after 864 d incubation. Addition of hydrogen to incubation is indicated by Y (yes). Samples are in paired columns of autoclaved (A) and untreated (−). DIC concentration, 13C-carbon isotopic composition of DIC, ratio of methane (mass 16) to argon (mass 40), and 13C-carbon and 2H-hydrogen isotopic composition of methane in incubation headspace in permil are shown. Due to low yields, methane isotopic analyses were only performed on coal incubations. Only nonautoclaved samples had enough methane to determine 2H enrichment, except for the last condition, which was below detection (bd). Cell density was measured from incubation separates before NanoSIMS sorting after 864 d for all substrate-added conditions and after 1,140 d for no-substrate–added control (2H2O only). Total cells were calculated from estimates of grams of rock per incubation. The active cell percentage is the number of ROIs above 10-fold natural abundance for 2H. nd, not detected (specifically, no cells were detected on the NanoSIMS membrane); nm, not measured.

  • * Indicates a sample of lower statistical reliability that was below the quantification limit (negative control) but cells were detected. Errors on DIC measurements are ±0.5‰ δ13C-DIC and ±0.0086 μmol DIC.