Oxygen profiles across the sediment-water interface in three different habitats in salt marshes: 1) Tidal river; submerged sediment. 2) Tidal ponds; submerged sediment and 3) vegetated marsh platform; intertidal. Profiles from tidal river were measured in sediment cores in the laboratory. Profiles from tidal ponds and marsh platform were measured in situ.Instrumentation: Optode microprofiling device from PreSens GmbH (Germany, www.presens.de) with needle-type optodes (PM-PSt7) for measurements of oxygen profles.Time: Tidal river (Parker river, Ma, USA) - August 2016, Tidal Ponds (Plum Island Estuary marshes, MA, USA) July 2018,Marsh Platform (Great Sippewissett marsh, MA, USA) August 2016.