The importance of small-celled phytoplankton in spring blooms at the marginal ice zone in the northern Barents Sea

The contribution from small and large cells to biomass and primary production was investigated during three cruises to the marginal ice zone in the northern Barents Sea in 2003, 2004 and 2005. Chlorophyll a biomass and primary production were size-fractionated at 10 μm. Particulate primary production was measured using 14C and 24 h in situ incubations. Twelve stations were successfully sampled and the stations were grouped into three different stages of a phytoplankton bloom. No pre- or post-bloom situations were observed. The highest integrated chl a biomass and primary production were 588 mg chl a m−2 and 1475 mg C m−2 d−1 measured during peak bloom situations in May 2005. In the early and late bloom groups the chl a biomass and primary production were dominated by small cells, while large cells dominated in the peak bloom group. Most of the carbon was produced during the peak bloom dominated by large cells. When seen over the stations that were size-fractionated the small cells contributed with 46% of the total carbon production (large+small cells). The importance of small cells in the carbon production is emphasized and small cells should not be neglected during phytoplankton blooms in marginal ice zones.