FIG 1.

Biogenic methane precursor assays in the Formosa cold seep sediments. (a) Geographic location of the Formosa Ridge cold seep in the South China Sea where sediment samples were taken. The map was created using Global Mapper. (b) Each 0.5 g of sediment was sampled from either 0 to 20 cm below the sea floor (cmbsf) or from 20 to 60 cmbsf and dissolved in 5 ml of artificial seawater, followed by amendment with 0.25% casein and 1 mg/ml of ampicillin and kanamycin in addition to 20 mM trimethyl amine (TMA), glycine betaine (GBT), choline, acetate, or 0.1 MPa H₂/CO₂ (80:20). The sediment microcosms were incubated at 18°C, followed by measurement of methane and GBT accumulation (orange bar) after 9 weeks. The inset shows carbon isotope signatures of methane at two concentrations in microcosms amended only with casein, GBT, or TMA and were measured using isotope ratio MS. Triplicate microcosms of each tested substrate were evaluated, and the averages and standard deviations are shown.