Lab work: Photo: Norwegian Polar Institute

Phytoplankton development in the Barents Sea is typical for a high latitude region with pronounced maximum biomass and productivity during spring. During winter and early spring (January-March), both phytoplankton biomass and productivity are relatively low. Spring bloom is initiated during mid-April to mid-May and may vary strongly from year to year. Bloom duration is typically about 3-4 weeks and is followed by a reduction in phytoplankton biomass mainly due to nutrient exhaustion and grazing by zooplankton. Later in the fall when the increasing winds start to mix the upper layer and bring nutrients to the surface, a short autumn bloom can be observed. However, the timing of phytoplankton development can vary geographically. Spring bloom in the Atlantic water domain (without sea-ice) is thermocline-driven; whereas in the Arctic domain (with seasonal sea-ice), stability from ice-melt determines the bloom (Skjoldal and Rey 1989, Hunt et al. 2012). Thus, spring bloom at the ice edge can sometimes take place earlier than in the southern regions of the Barents Sea due to early stratification from ice melting.