Fig. 4: Influence of oxygen (O₂) on respiration.

a Oxygen concentrations (open circles) and sulfate (SO₄²⁻) reduced (open squares) in mol m⁻³ sed in slurries over an oxic-anoxic transition. Slurries were from sediment collected on May 25, 2020. Oxygen concentrations are shown for four Exetainers, resampled over the course of the incubation. b Radiolabeled sulfate reduced bound to a silver wire (closed squares), or to the sediment in the same incubation vial (open squares) in incubations including a silver wire over an oxic-anoxic transition. For all sulfate reduction measurements, each point corresponds to a separate incubation vial. The vertical line represents the transition to anoxic conditions. c Sulfate reduction rates in sediment slurries from May 25, 2020 during three different periods of incubation. Slurries were untreated or amended with a combination of catalase (CAT) and superoxide dismutase (SOD). Black bars represent the sulfate reduction rate in the oxic period of the incubation, light gray bars represent the sulfate reduction rate between the start and 2 h after the start of anoxia, dark gray bars the sulfate reduction rate between 2 h after the start of anoxia and the end of the incubation (20–22.5 h). Error bars represent the standard error of the slope.