Effects of air discharge on bubble dynamics in vertically discharged bubble plumes

•The effect of air discharge on the mixing capacity of bubble plumes was tested.•Effects of air discharge on bubble concentration and bubble interface area were studied.•Bubble interfacial area and bubble size frequency were measured along the plume axis.•Bubble parameters were independent of air discharge <35% of the water depth.•The number of bubbles and their velocities increased non-linearly with air discharge.•Bubble diameter increased by 32 % as air discharge quadrupled.