Artificially oxygenating the Swan River estuary increases dissolved oxygen concentrations in the water and at the sediment interface

•Artificial oxygenation increased oxygen concentrations in the shallow Swan River estuary.•Volume-averaged dissolved oxygen concentrations increased by 1 mg L−1 day−1.•Tidal excursion distributed added oxygen.•Impacts were observed from 4.8 km downstream to 6.7 km upstream of plant discharge.•Water column dissolved oxygen increased over a distance in excess of 11.5 km.•Oxygen fluxes and concentrations at the sediment-water interface increased locally.