Cool, alkaline serpentinite formation fluid regime with scarce microbial habitability and possible abiotic synthesis beneath the South Chamorro Seamount

Progress in Earth and Planetary Science

Table 3 Radio-isotope-tracer carbon assimilation of microbial community in the CORK fluids and positive controls

Cruise ID	HPD dive#	Tracer and incubation condition	Incubation time (days)	Net assimilation (nmol day⁻¹ L⁻¹)
NT09-01	943	¹⁴C-CH₄ (0.25 MBq per bottle and 0.4 mM)	54	0.036
NT09-01	943	¹⁴C-CH₄ (0.25 MBq per bottle and 0.4 mM) with 40 μM O₂	54	0.049
NT09-01	947	¹⁴C-Leucine (0.25 MBq per bottle and 0.1 mM)	52	0.014
	947	¹⁴C-Formate (0.25 MBq per bottle and 0.1 mM)	52	0.06
	947	¹⁴C-Acetate (0.25 MBq per bottle and 0.1 mM)	52	0.004
NT09-01	948	¹⁴C-CH₄ (0.25 MBq per bottle and 0.4 mM) with 10 mM NaSO₄ and 0.5 mM Na₂S	49	0.039
NT09-01	948	¹⁴C-CO (0.25 MBq per bottle and 0.4 mM)	49	n.d.^a
NT09-07	1007	¹⁴C-CH₄ (0.25 MBq per bottle and 0.4 mM)	123	0.2
	1007	¹⁴C-HCO₃⁻ (0.25 MBq per bottle and 0.1 mM) with 0.4 mM H₂	123	1.4
	1009	¹⁴C-Formate and ¹⁴C-acetate (each of 0.25 MBq per bottle and 0.1 mM)	122	0.05
An aerobic methanotroph culture		¹⁴C-CH₄ (0.25 MBq per bottle and 0.4 mM)	1	20
An autotrophic community in diffusing hydrothermal fluid		¹⁴C-HCO₃⁻ (0.25 MBq per bottle and 0.1 mM)	5	2.3