Fig. 8: Abundance of aerobic/denitrifying hydrogen, methane, and sulfur oxidizers versus oxygen concentration.
From: Hydrogen and dark oxygen drive microbial productivity in diverse groundwater ecosystems
a Hydrogenophaga b Methylobacter and Methylotenera and c Sulfuricurvum and Thiobacillus. Oxygen concentration is shown on pseudo-log10 scale, to include samples with no oxygen (zero). Boxplots summarize relative abundances of d hydrogenotrophs, e methylotrophs, f thiotrophs, and g oxygen concentrations based on water age categories (upper and lower quartiles and whiskers (each representing 25% of the data), median (line) and outliers (dots)). Relative sequence abundances of the aerobic/denitrifying clades tend to peak at hypoxic conditions (~0.5 mg L−1) potentially because these waters contain both sufficient electron donors (hydrogen, methane, sulfur) and electron acceptors (oxygen, nitrate). n is given in f and applies to all panels.
