Spatial and temporal Oxygen, pH and CO2 dynamics in the rhizosphere of the salt marsh plant; Spartina anglica. Profiles and time-series of Oxygen, pH and CO2 were measured in the laboratory on Spartina anglica samples collected in the Danish Wadden Sea ("Rømødæmningen" 55°08'44 N, 08°36'57 E). The study was conducted using a Planar optode system; VisiSens TD from PreSens - Precision Sensing GmbH, Regensburg, Germany. Data includes: Cross-sectional concentration profiles of O2, pH, and CO2 measured across roots of Spartina anglica growing in sandy sediment under daylight conditions Time-series following that average concentration of oxygen, pH and CO2 at the root surface and in the bulk sediment, respectively, during two days with alternating light and dark conditions.