Abstract: The development of the phytoplankton bloom and its relation to the water column stabilization duringthe transition from early to high summer (of 1991) in the seasonally ice covered zone of the Barents Sea isstudied from a meridional transect of repeated hydrographic/biological stations. The water column stabilization isdescribed in detail with the aid of vertical profiles of the Brunt-Väisälä frequency squared (N2). The contributionsof seasonal warming and ice melting to the stabilization are elucidated by determining the effects of temperatureand salinity on N2.The spring bloom in 1991 migrated poleward from June to July by about 400 km, associated with the retreat ofthe ice edge. The spring bloom culminated with maximum chlorophyll concentrations in the mixed layer about100-300 km north of the centre of the meltwater lense, at its northern edge, where the ice cover was stillsubstantial.From the distribution of N2 it becomes obvious that the bloom starts at the very beginning of stabilization whichresults solely from the release of meltwater. The increase of temperature due to the seasonal warming does notcontribute to the onset of the vernal blooming; temperature starts to contribute to the stratification later, when thespring bloom already has ceased due to the exhaustion of nutrients in the mixed layer. At that time a deepchlorophyll maximum has formed in the seasonal pycnocline, 20-30 m below the base of the mixed layer.The effect of the seasonal ice cover on the mean areal new primary production is discussed.