Effects of temporary streamflow interruption on hyporheic oxygen dynamics

Short-term streamflow interruptions, i.e. brief recessions of surface water resulting in temporary drying of streams, are occurring more frequently nowadays due to climate change or water management operations. The impact of these streamflow disruptions on hyporheic oxygen dynamics and their legacy effect on stream metabolism remains unclear. This study aims to investigate the effects of a one-day streamflow interruption on oxygen patterns in surface water and the hyporheic zone by comparing conditions before and after the disturbance. We monitored oxygen concentrations in surface water and streambed sediment of a side channel of the River Erpe (Berlin, Germany) at different experimentally manipulated surface water velocities (0.1–0.5 m s −1 ) for five days before and fifteen days after the streamflow interruption. After rewetting, the diel amplitude of surface water oxygen concentrations decreased by 30% relative to pre-interruption conditions, and partially recovered within five days. Oxygen concentrations in deeper sediment layers were lower than before the interruption. This response pattern was observed across all surface water velocities (0.1–0.5 m s −1 ), and it was more pronounced at 0.4 and 0.1 m s −1 . Three weeks after flow resumed, surface water and porewater oxygen concentrations remained around 2 mg L −1 lower than pre-interruption values. Five days after the disturbance, a gradual metabolic response was observed, with gross primary production and ecosystem respiration increasing in magnitude by 26% and 31%, respectively. These findings emphasize that short streamflow intermittency can trigger shifts in oxygen regimes and metabolism, and therefore needs to be accounted for in sustainable water management strategies.