Fig. 2

The effect of particle size-induced variations in the extent of anaerobic microsites on microbial metabolic rates and pathways. a Overall mineralization rate within the reactor, b comparison of the total aerobic and anaerobic respiration rates, c volume-specific aerobic and anaerobic respiration rates, and d contribution of anaerobic respiration pathways to the overall rates. The overall mineralization rates were calculated using linear fits, as shown in Fig. 1a. A combination of anaerobic incubations, solid- and solution-phase measurements, and a mass balance approach was used to quantify aerobic and anaerobic respiration rates across the diffusion-limited domain (a detailed description of our approach is provided in the “Methods” section). Particle size variations to manipulate the extent of anaerobic microsites are shown in red (coarse = 150–250 µm) and blue (fine = 25–45 µm). Error bars denote the standard error of the mean calculated from four replicate reactors