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A compilation of phytoplankton species abundance data from the spring bloom along the northern Norwegian coast and in the Barents Sea shows that the quantitatively most important species are the prymnesiophyte Phaeocystis pouchetii and the common cold water to temperate diatoms Chaetoceros socialis, Skeletonema costatum sensu lato, Fragilariopsis oceanica, Thalassiosira spp., Chaetoceros furcellatus, Chaetoceros compressus, Chaetoceros debilis and Bacterosira bathyomphala. The relative abundance of diatoms and Phaeocystis varied highly and apparently stochastically between years. P. pouchetii occurred during all stages of the spring bloom and sometimes completely dominated the phytoplankton community. Along the Norwegian coast, the importance of P. pouchetii increased northwards. The species composition in coastal fjords at 70° N is surprisingly similar to that of shelf waters in the Barents Sea (up to 80° N). An exception is S. costatum sensu lato which was seldom observed in Arctic waters. Small flagellates (<10 μm) other than dinoflagellates and P. pouchetii are also important among the Barents Sea spring phytoplankton. Associations of species seem rigid over time and are dominated by C. socialis and P. pouchetii in northern waters. Biogeographical categories of spring bloom species in relation to environmental conditions are discussed. [ABSTRACT FROM AUTHOR]

Abstract: During a circumnavigation of the Svalbard archipelago in May 2006, simultaneous marine environmental (meteorology, heat flux, ocean turbulence, irradiance) and biological (phytoplankton and zooplankton biomass/species) data were sampled at selected stations. The zooplankton data were supplemented by high-resolution, high-speed VPR sampling down to 100m depth at most stations. We were able to sample different phases of the phytoplankton spring bloom in Arctic as well as in Atlantic waters, and the stations represented different situations with respect to irradiance, turbulence and water-column stability. Phytoplankton growth and depth distribution were physically controlled, while zooplankton distributions were affected by biological parameters and turbulence. Development of the zooplankton followed the phytoplankton bloom phase, which was progressing in a direction from west to east in the waters north of Svalbard, and southwards in the Barents Sea. Our results also showed that the zooplankton did not avoid Phaeocystis pouchetii colonies, which have earlier been described as toxic. Despite an early retreat of the ice this year there was no apparent mismatch between the phytoplankton bloom and the dominant mesozooplankton, Calanus spp. [Copyright &y& Elsevier]

Abstract: 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 10μm. Particulate primary production was measured using 14C and 24h 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 588mg chl a m−2 and 1475mg Cm−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. [Copyright &y& Elsevier]

Abstract: To evaluate importance of bacterioplankton in the Barents Sea, we investigated the spatial and temporal distribution of bacterial abundance, biomass and production in relation to spring-bloom stages. During three cruises in 2003–2005, 12 stations were investigated. Average bacterial abundance (±S.D.) in the photic zone was 3.6±3.0×105 cellsml−1, corresponding to 7.1±6.1mgCm−3. Bacterial production in the photic zone was measured using dual labelling technique with 3H-thymidine and 14C-leucine, resulting in average production rates (±S.D.) of 1.5±1.0 and 6.9±4.8mgCm−3 d−1, respectively. In spite of low water temperature, the bacterial community was well developed and active. Similarity analysis of stations resulted in four distinct spring-bloom stages, covering pre- early-, late- and post-bloom stages. In the photic zone, bacterial biomass on average corresponded to 6±2% of phytoplankton biomass. Highest integrated bacterial biomass was observed at mid- to late-bloom stages. Average bacterial production equalled 32±6% (±S.E., n=24) of particulate primary production. The bacterial production to primary production ratio tended to increase at late-bloom stages. The observed bacterial activity illustrates the importance of the bacterial pathway for channelling carbon from DOC through the microbial food web back into the classical food web, which previously has not been adequately considered in plankton ecosystem models of the Barents Sea. [Copyright &y& Elsevier]

Analysis of data obtained by the Institute of Marine Research, Norway, at their regular surveys of the Fugløya-Bjørnøya section, between the northern tip of Norway and Bear Island, has allowed for an identification of the factors that control spring bloom development in the region, and their interannual variability. In the southern part of the section the bloom starts as the waters become stratified due to a northward spreading of low salinity water from the Norwegian Coastal Current. In the middle part of the section the bloom is initiated when vernal stratification develops due to heating of the ocean surface, and the bloom may develop in either of two directions throughout summer, depending on the prevailing atmospheric pressure gradient over the region. A north to south high to low pressure gradient will direct surface winds to the west. Ekman drift will then be to the north and a wedge of low salinity, low nutrient water will spread out over the region, leading to the termination of the bloom. When the pressure gradient is reversed, winds will blow to the east and intrusion of fresh water into the region will be limited. In these years the bloom appears to follow a classical Atlantic pattern, unable to fully utilize available nitrate and probably terminated due to extensive grazing. The central part of the Barents Sea Opening is thus yet another northern high latitude region where the bloom is subject to substantial interannual variations, potentially affecting higher trophic levels. [ABSTRACT FROM AUTHOR]

The knowledge of the relative contribution of algal groups and the environmental factors that control their abundance in the marginal ice zone of the Barents Sea is rather limited. Therefore, a field investigation to study the hydrography and the phytoplankton composition of the marginal ice zone (MIZ) in the central Barents Sea was carried out along a south-north transect in May 1993. The weakly stratified Atlantic sector of the transect appeared to be in a pre-bloom state and had intermittent intrusions from the meandering Polar Front and the Norwegian Coastal Current, introducing water of a more advanced bloom state. Pico- and nanoplankton flagellates and monads dominated, with a few diatoms and Phaeocystis pouchetii colonies. The average new production rate of 26 g C · m-2 as reflected by NO3 depletion in the euphotic zone, however, indicated that the vernal bloom had been in progress for some time in the Atlantic sector without leaving specific signals in the suspended fraction. The ice-edge and Polar Front area was characterized by a dominance of centric colonial diatom genera Chaetoceros and Thalassiosira with some development of P. pouchetii. In the densely ice-covered and stratified Arctic zone the vernal bloom was at its maximum and dominated by the diatom genera Fragilariopsis and Chaetoceros. Diatoms were limited by silicate concentrations <2 µM in 32% of all samples. New production, as revealed by the C equivalent of nitrate depletion in the upper layer, ranged between 12 g C · m-2 in the north to 45 g C · m-2 in the meandering Polar Front, with an average of about 27 ± 28% g C · m-2. The time development of the vernal bloom in the marginal ice zone and the central Barents Sea in late May 1993, with its complicated zonal structure, was not from south to north, but intermittently from north to south. Later during the year the general development of the vernal bloom... [ABSTRACT FROM AUTHOR]