Abstract. 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 was, as expected, from south to north.

Abstract. Large phytoplankton biomass accumulates during ice-edge blooms in Arctic waters, where taxa such as diatoms or the prymnesiophyte Phaeocystis pouchetii usually dominate. Based on characteristics from temperate phytoplankton, we hypothesized that in Barents Sea waters, a larger fraction of primary production would be extracellular (for synthesis of colonial mucilage) during periods of dominance by P. pouchetii as opposed to periods when diatoms dominated. This altemation of P. pouchetii and diatoms would affect the relationship between the particulate and dissolved carbon pools in the upper water column of the marginal ice zone (MIZ). Results presented in this paper do not support this hypothesis. Although P. pouchetii contributed strongly to the extracellular carbon pool (mucilage and dissolved organic carbon, DOC) during an ice-edge bloom in May 1993, arctic diatoms contributed an equal amount of exuded carbon. Three process stations visited along a north-south transect in the MIZ in the Barents Sea, presented between 36% and 55% of the primary production as extracellular carbon, defined as labeled organic matter which passes through a Whatman GF/C filter. No difference in the carbon allocation between diatom-and P. pouchetii-rich phytoplankton was observed in these stations. In contrast, the station located in ice-free waters had 18% of primary production in the extracellular fraction. These results (1) highlight similar carbon allocation for diatom-and P. pouchetii-dominated phytoplankton in surface waters of the Barents Sea during the spring and/or ice-edge bloom at the MIZ and (2) suggest that polar phytoplankton may be stronger producers of extracellular carbon, and possibly DOC, than previously thought.

The changes in egg lipids and fatty acid compositions that occur during embryonic development of spotted wolf-¢sh, Anarhichas minor, were examined by monitoring individual egg batches from the time of spawning (egg stripping) until hatching. The lipids, present as 3.7 AE 0.1% of the wet mass of the freshly stripped eggs, contained high percentages of monoenes (monounsaturated fatty acids (MUFAs), ca. 33%) and polyenes (ca. 43%) and approximately 20% saturated fatty acids (SFAs). The fatty acid pro¢les were dominated by a small number of fatty acids. The major SFA was 16:0 (ca. 14%), the dominant MUFA was 18:1 n-9 (ca. 21%), and among the polyenes, the n-3 highly unsaturated fatty acids (HUFAs) 22:6 n-3 docosahexaenoic acid (DHA) and 20:5 n-3 eicosapentaenoic acid (EPA) were present in the highest concentrations (EPA, ca. 16%; DHA, ca. 19%). The n-6 HUFA 20:4 n-6 arachidonic acid (AA) was present as ca. 1% of the total fatty acids in the freshly stripped eggs. This resulted in an AA:EPA of ca. 0.07, which is lower than reported for eggs of many other ¢sh species. As embryonic development progressed, the percentage contribution of AA to the total fatty acids almost doubled. There were also increases in the relative proportions of SFAs (due mainly to an increase in the percentage of 16:0 to ca. 16% at hatch) and DHA (to ca. 23%), and there was a corresponding decrease in the percentage of MUFAs (mostly brought about by a decrease in the percentage of18:1n-9 to ca. 18% at hatch). The most marked changes occurred towards the end of incubation. The percentage of EPA changed little during incubation. This implies that there was selective retention of DHA, 16:0 and AA, and these fatty acids were probably incorporated into cell membranes. MUFAs, particularly 18:1 n-9, seem to have been catabolized to provide energy for the developing embryo, and some EPA also seems to have been utilized as an energy source. Survival of eggs to the eyed stage (range ca. 10^80%) and to hatch (ca. 5^75%) was negatively correlated with the %AA, %EPA and AA:DHA of the freshly stripped eggs. There was also a negative correlation between AA:EPA and egg survival, which implies that there is not a universal requirement for a high AA:EPA to ensure high rates of survival of ¢sh eggs.

Phytoplankton dynamics and carbon input into Arctic and sub‐Arctic ecosystems were investigated around Svalbard, in summer 1991. Phytoplankton biomass, species composition and dissolved nutrient concentrations were analysed from water samples collected along seven transects. Phytoplankton biomass was low especially to the north (Chlorophyll‐a mean 0.3 pg 1‐ '), where flagellates dominated the communities and only ice‐diatoms were present. To the west, the phytoplankton composition was representative of a summer Atlantic community, in a post‐bloom state. Zooplankton grazing, mainly by copepods, appeared to be the main control on biomass to the west and north of Svalbard. In the Barents Sea (east of Svalbard), an ice edge bloom was observed (Chlorophyll‐a max. 6.8 pgl‐') and the ice edge receded at a rate of approximately 1 1 km day‐'. The phytoplankton community was represented by marginal ice species, especially Phaeocystis poucherii and Chaeroceros socialis. South of the ice edge, Deep Chlorophyll Maxima (DCM) were observed, as surface waters became progressively nutrient‐depleted. In these surface waters, the phytoplankton were predominantly auto‐ and heterotrophic flagellates. Carbon production measurements revealed high net production (new and regenerated) to the north of the Barents Sea Polar Front (BSPF); it was especially high at the receding ice edge (reaching 1.44gC m‐'day‐'). To the south, a low level of production was maintained, mainly through regenerative processes.

Suspended and sedimented part~culate matter was examined along transects on the continental shelf off northern Spitsbergen, Norway, during summer 1991 The transects were situated in non-ice-covered areas dominated by Atlantic water, areas with multi-year ice and the marginal ice zone. The variability of the sedirnented matter with regard to composition, quantity and quality between the 7 investigated stations was considerable. The open Atlantic water showed the highest suspended blomass [l00 to 280 mg particulate organic carbon (POC) m-3] and the vertical flux was moderate (24 to 30 mg POC m-' d") and dominated by faecal matter. While the suspended biomass in areas covered by multi-year ice was low (<65 mg POC m-3), the vertical flux was relatively high (18 to 76 mg POC m-2 d") and dominated by terrestrial organic and faecal matter. The contribution of phytoplankton cells to the vertlcal flux of POC was small in areas covered by multi-year ice, on average about 1 %,. The contribution of phytoplankton cells to the vertical flux jn the marginal ice zone was higher (5 F?; of POC), consisting mainly of Chaetoceros socialis and Fragilariopsis sp., but a considerable amount of faecal matter also settled At all stations zooplankton strongly influenced the vertical flux, not only by faecal pellet production but probably also by direct mediation of fluxes (e.g. coprophayy).