Moving 6-year analysis of Water body dissolved oxygen concentration in Black Sea for each season: winter (December-February), spring (March-May), summer (June-August), autumn (September-November). Every year of the time dimension corresponds to the 6-year centered average of the season. 6-years periods span from 1980-1985 until 2016-2021. Data Sources: observational data from SeaDataNet/EMODNet Chemistry Data Network. Units: umol/l. DIVA analysis: The computation was done with the DIVAnd (Data-Interpolating Variational Analysis in n dimensions), version 2.7.9, using GEBCO 30sec topography for the spatial connectivity of water masses The horizontal resolution of the produced DIVAnd maps grids is 0.05 degrees. The vertical resolution is 16 depth levels: 0, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 125, 150, 200, 250m The horizontal correlation length: 100km. The vertical correlation length (in meters): twice the vertical resolution (10, 10, 20, 20, 20, 20, 20, 20, 20, 20, 20, 50, 50, 100, 100, 100). The error variance (epsilon2): 1 An anamorphosis transformation was applied to the data: threshold value=200. Background field: not used. Quality control of the observations was applied using the interpolated field: QCMETHOD=3 and visual inspection (Observations with residuals outside the minimum and maximum values of the 99% quantile were discarded from the analysis after thoroughly visual inspection)