Fig. 4: Potential rates of biological methanogenesis from formate and bicarbonate by planktonic microbial communities in well water samples collected from the Samail Ophiolite in 2020.

Potential rates of biological substrate transformation were determined via microcosm assays using well waters collected from the Samail Ophiolite in 2020. Results are plotted on a logarithmic scale. The average rates of methane generation observed in four replicate abiological controls were subtracted from values in four replicate biological assays (Avg) and their combined standard deviations (SD) are presented at five timepoints over an 8-week incubation. P-values were determined between biological assays and abiological controls at each timepoint via Student’s t-test assuming unequal variance for each condition (*p < 0.05, **p < 0.01).