TABLE 3.

Stable carbon isotopic compositions of bicarbonate, CO₂ (calculated from bicarbonate), bulk biomass, Chloroflexus and cyanobacterial biomarkers, nondiagnostic lipids, and glucose in mat samples expressed in per mille relative to the PeeDee Belemnite standard

Category or compound	Peak no.a	δ13C values of samples
		NMA sourceb	NMA downstreamb	Tangerine Spring	Octopus Spring	Mushroom Spring	C. aurantiacusc
Bicarbonate		−2 to −4d	−2 to −4d	−3.3	∼6.8e	−6.8	0
CO2f		∼9	∼9	∼9	∼12	∼11
Bulk biomass		−14.9	−23.5	−24.8	−16.9	−13.2	−13.0
Chloroflexus biomarkers
C31:3 alkene	9	−8.9	−15.1	−20.0	−18.9g	NMh	−12.5
C32 wax ester	12	−17.7	−22.7	−26.0	−18.3	−16.5	NM
C33 wax ester	14	−17.9	−24.1	−27.0	−18.5	−16.4	−15.0
C34 wax ester	16	−17.4	−23.4	−26.7	−18.5	−16.5	−14.4
Cyanobacterial biomarker
C17 n-alkane	1		−36.3	−36.3	−34.1	−29.6
General lipids
C15 fatty acid	2	−19.4	−23.4	−27.1	−20.2	−17.5	NM
C16 fatty acid	3	−19.3	−34.5	−35.3	−21.3	−21.3	−13.8
C17 fatty acid	4	−18.9	−22.1	−27.6	−18.7	−16.8	−14.8
C17 alkanol	5	−18.0	−22.0	−27.9	−19.4	−15.5	NM
C18:1 fatty acid	6		−32.7	−35.5			−12.5
C18 fatty acid	7	−16.0	−33.9	−35.1	NM	−24.4	−13.6
C18 alkanol	8	−16.1	−24.3	−29.1	−22.2	−21.5	−12.5
Sugar
Glucose		−5.1	−21.8	−20.0	−11.0	−11.5	−5.7

^aSee Figure 1.

^bPreviously reported by van der Meer et al. (39), except for the glucose isotope values.

^cFrom van der Meer et al. (40). Isotope values for organic compounds are reported relative to bicarbonate.

^dMadigan et al. (19).

^eAssuming similar δ¹³C value as for Mushroom Spring.

^fCalculated based on temperature-dependent isotope equilibrium equation (21).

^gPartial coelution.

^hNM, not measured.