Fig. 4: In situ, ex situ and cell-level energy yield measurements for trace gases H2, CO and CH4.
From: Microbial aerotrophy enables continuous primary production in diverse cave ecosystems
a Boxplots showing in situ atmospheric concentrations (ppm), with independent replicates (n = 81) grouped by gas, site and host rock. Dashed horizontal lines show average global concentration (2021-2022) for atmospheric H2 (0.53 ppm), CO (0.10 ppm) and methane (1.9 ppm). b Boxplots showing in situ sediment–atmosphere uptake gas fluxes (values indicate net gas consumption) with biological replicates (n = 12) grouped by gas and site. Flux phases provide upper (transient) and lower bound (equilibrium) estimates. c Boxplots showing bulk sediment and biofilm oxidation rates normalised to global average atmospheric gas and cell numbers, with biological replicates (n = 44) grouped by gas, site and host rock. d Boxplot showing the amount of power per cell derived from the oxidation of each trace gas, with biological replicates (n = 44) grouped by gas, site and host rock. Coloured bars depict the range of literature values of energy yield per cell by atmospheric methane oxidising isolates M. aurea KYG, M. gorgona MG08, M. palsarum NE2 and M. rosea SV97 (orange42), maintenance energy requirements or endogenous metabolic rates of different pure cultures (green104, yellow105, jade106) and hydrogen oxidisers in deep marine sediments (pink107). e Boxplot showing rates of nitrogen and sulphur compound metabolism, with positive values indicating accumulation and negative values showing uptake with biological replicates (n = 17) grouped by site. Nitrification is expected to result in ammonium (NH4+) consumption and nitrite (NO2−), nitrate (NO3−), whereas sulphide oxidation is expected to cause sulphate (SO42−) production. Boxplots display the median (centre line), interquartile range (box) and whiskers extending to values within 1.5 × IQR of the box.
