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The decrease in Arctic sea-ice extent and thickness as a result of global warming will impact the timing, duration, magnitude and composition of phytoplankton production with cascading effects on Arctic marine food-webs and biogeochemical cycles. Here, we elucidate the environmental drivers shaping the composition, abundance, biomass, trophic state and vertical flux of protists (unicellular eukaryotes), including phytoplankton, in the Barents Sea in late August 2018 and 2019. The two years were characterized by contrasting sea-ice conditions. In August 2018, the sea-ice edge had retreated well beyond the shelf break into the Nansen Basin (>82°N), while in 2019, extensive areas of the northwestern Barents Sea shelf (>79°N) were still ice-covered. These contrasting sea-ice conditions resulted in marked interannual differences in the pelagic protist community structure in this area. In August 2018, the protist community was in a post-bloom stage of seasonal succession characterized by oligotrophic surface waters and dominance of small-sized phytoplankton and heterotrophic protists (predominantly flagellates and ciliates) at most stations. In 2019, a higher contribution of autotrophs and large-celled phytoplankton, particularly diatoms, to total protist biomass compared to 2018 was reflected in higher chlorophyll a concentrations and suggested that the protist community was still in a late bloom stage at some stations. It is noteworthy that particularly diatoms contributed a considerably higher proportion to the protist biomass at the ice-covered stations in both years compared to the open-water stations. This pattern was also evident in the higher vertical protist biomass flux in 2019, dominated by dinoflagellates and diatoms, compared to 2018. Our results suggest that the predicted transition toward an ice-free Barents Sea will lengthen the oligotrophic summer period with low algal biomass and associated low vertical flux. publishedVersion

The Nansen Legacy (NL) JC3 cruise (19.02.-11.03.2022) aimed to fill regional, temporal and scientific gaps following the earlier NL cruises, in particular during the winter-to-spring transition and in the northern part of the NL transect to the Nansen Basin. Joint physical, chemical, and biological sampling and experiments for new technology addressed aims of RF1, RF2, RF3 and RA-C.

The main scientific goal of the Nansen Legacy JC2-2 cruise was to extend the project’s research activities from the northern Barents Sea shelf into the central Arctic Ocean. Specifically, JC2-2 addressed objectives of the research foci RF1, RF2 and RF3 by jointly collecting interdisciplinary samples and data at five process (P) and in-between NLEG stations extending northward from the previously northernmost station P7. We had a special focus on sea ice and the upper ocean as well as connectivity to the mid and deep water column and underlying sediments in early autumn. In addition, JC2-2 explored the role of transport of elements and organisms from the Siberian shelves through the Transpolar Drift in the Amundsen Basin. Experiments were an important part of the cruise and were designed to measure and quantify relevant processes and their rates. This cruise was also a Norwegian contribution to the international Synoptic Arctic Survey (SAS) and took place at the same time as the Swedish icebreaker Oden was on their SAS expedition in the nearby region between Northeast Greenland and the North Pole.

The Nansen Legacy cruise Q1 (Q1: 1st quarter of the year) was part of the seasonal investigation of the northern Barents Sea and adjacent Arctic Basin. The cruise was conducted in March 2021, and focused on comparing the physical, chemical and biological conditions along the Nansen Legacy main transect in open waters and within the sea ice. The cruise addressed objectives of the Nansen Legacy work packages ‘Physical drivers’ (Research Focus 1), ‘Human impact’ (Research Focus 2) and ‘The living Barents Sea’ (Research Focus 3).In total, seven process stations (P1, P2, P3, P4, P5, P6 and P7) were conducted, with some more additional (NLEG) stations in-between.

In the Arctic shelf seas, the mesozooplankton biomass is dominated by the arctic copepod Calanus glacialis, but its boreal congeneric C. finmarchicus is expanding northwards. Even though it is already there, C. finmarchicus may not be able to truly establish itself in the Arctic seas and potentially replace C. glacialis. We compared metabolic and digestive enzyme activities of sympatric C. glacialis and C. finmarchicus from Isfjorden, Svalbard and off-shelf north of Svalbard. The seasonal regulation of anabolic and catabolic enzyme activities was generally similar for the two species, but with some interspecific differences corresponding to their ontogeny. Wake-up from overwintering started earlier in adults of C. glacialis than in C. finmarchicus, while the onset of dormancy started early in the overwintering stages of both species. Furthermore, C. glacialis showed an earlier and higher mobilization of lipase enzyme activities, indicating higher efficiency in assimilating dietary lipids compared to C. finmarchicus. Similar population sizes and population structures for C. finmarchicus off-shelf north of Svalbard and in Isfjorden support a similar origin. Still, C. finmarchicus was able to match regulation of enzyme activities to the bloom even though the bloom peaked approximately a month later off-shelf north of Svalbard, indicating that food availability is an important signal for the final step of termination of diapause. Even though the two species largely follow the same patterns of metabolic enzyme activities, the more efficient lipid anabolism of C. glacialis may give it an advantage over C. finmarchicus in high-Arctic unpredictable environments with short-pulsed primary production regimes.

The objectives of this study were to explore trophic levels and possible diet overlap between harp seals (Pagophilus groenlandicus) and common minke whales (Balaenoptera acutoroostrata) in the Barents Sea using stable isotopes of nitrogen (δ15N) and carbon (δ13C) and fatty acid analyses, and to explore the energy pathways from the plankton to the top predators. Blubber and muscle samples from 93 harp seals and 20 minke whales were collected in the southern Barents Sea in May 2011. The study showed that harp seals were at a higher trophic level than minke whales during spring. This supported previous diet studies suggesting a more fish-dominant diet for seals, as compared with the whales, at this time of the year. The stable isotopes and fatty acids indicated niche separation between the seals and the whales, and between different age groups of the harp seals. Older seals had fatty acid profiles more equal to minke whales as compared with younger seals. Furthermore, while the fatty acid profiles suggested that krill were of particular importance for the young seals, the profiles from older seals and whales suggested that fish dominated their diets.

Papers 1,3,4 and 5 of this thesis are not available in Munin: 1. Wold A, Darnis G, Søreide JE, Leu E, Philippe B, Fortier L, Poulin M, Kattner G, Graeve M and Falk-Petersen S: 'Life strategy and diet of Calanus glacialis during the winterspring transition in Amundsen Gulf, southeastern Beaufort Sea' Polar Biology (2011) 34:1929-1946. Available at http://dx.doi.org/10.1007/s00300-011-1062-6 3. Wold A, Leu E, Walkusz W and Falk-Petersen S: 'Lipids in copepodite stages of Calanus glacialis', Polar Biology (2007) 30:655-658. Available at http://dx.doi.org/10.1007/s00300-006-0233-3 4. Wold A, Jæger I, Hop H, Geir Wing Gabrielsen GW and Falk-Petersen S: 'Arctic seabird food chains explored by fatty acid composition and stable isotopes in Kongsfjorden, Svalbard', Polar Biology (2011) 34:1147-1155. Available at http://dx.doi.org/10.1007/s00300-011-0975-4 5. Falk-Petersen S, Haug T, Hop H, Nilssen KT and Wold A: 'Transfer of lipids from plankton to blubber of harp and hooded seals off East Greenland', Deep-Sea Research II (2009) 56:2080-2086. Available at http://dx.doi.org/10.1016/j.dsr2.2008.11.020 The Arctic marine ecosystem is characterized by strong seasonality and a short but productive period of primary production in the spring when the ice breaks up. Calanus glacialis is one of the key links between primary producers and higher trophic levels, and it is adapted to the strong seasonality by life cycle traits such as; seasonal vertical migration, diapausing, reproduction in the spring and extensive energy storage. The timing of these events will have consequences for the success of C. glacialis and also for the energy available at higher trophic levels. The aim of this study was to increase the knowledge about these key life history traits with focus on the role of lipid accumulation, seasonal vertical migration and the transfer of energy from primary producers through Calanus, to higher trophic levels, such as seabirds and seals. Lipid accumulation and seasonal vertical migration of C. glacialis were studied in the Amundsen Gulf, in the Canadian Arctic (Paper I) and in Svalbard waters (Paper II and III). The transfer of energy to higher trophic levels was studied by comparing the fatty acid composition of predators to that of their prey and by using stable isotope analysis to calculate their trophic level. We analyzed five seabird species from Kongsfjorden; Little auk (Alle alle), Brünnich’s guillemot (Uria lomvia), Black-legged kittiwake (Rissa tridactyla), Northern fulmar (Fulmarus glacialis) and Glaucous gull (Larus hyperboreus) (Paper IV) as well as harp seals (Phoca groenlandica) and hooded seals (Cystophora cristata) from the West Ice (Paper V). The timing of the ascent of C. glacialis during spring, the match of reproduction with the primary production as well as the length of the primary production period determines the development of offspring , the overwintering stage the following winter, and hence the length of the life cycle. The shorter the period of primary production, the more important is the match between reproduction and bloom. Ice algae may fuel early maturation of the females and prolong the reproductive period. In the Amundsen Gulf, C. glacialis ascended to the surface water in time to feed on the ice algae bloom, but since CIII was the main overwintering stage, the ice algae fuelled development of CIII which could develop to females that possibly could spawn during the summer. The life history trait of accumulating energy in form of lipids is an adaptation of Calanus to the large seasonal and inter-annual fluctuations in food availability, and the lipids represent an effective transfer of energy up the food chain. High levels of the Calanus markers 20:1n9 and 22:1n11 in the seabirds Little auk, Black-legged kittiwake and Northern fulmar from Kongsfjorden, Svalbard, indicate that these seabirds are part of the Calanus based food web (Paper IV). Harp seals and hooded seals (Paper V) showed considerably overlap in diet, but the fatty acid composition of harp seals originated from a diatom–Calanus based food web, while the fatty acids of hooded seals originated from a food web based on dinoflagellates and the prymnosiophyte Phaeocystis pouchetii. To conclude, the diatom–Calanus food chain is an important driver for the high latitude pelagic arctic food web. The match between timing of primary production, either as ice algae or phytoplankton bloom, and the timing of reproduction of C. glacialis is crucial for the accumulation of lipids in Calanus may have consequences for the energy available for higher trophic levels.

Studentarbeid i sykepleie (bachelorgrad) - Høgskolen i Bodø, 2010

Gelatinous zooplankton, here referring to the phylum Cnidaria and Ctenophora and the class Appendicularia are important components of marine ecosystems due to their very diverse diets, life cycles and seasonal dynamics. In the Barents Sea, several studies reviewed the gelatinous zooplankton diversity, yet few studies documented the diversity and distribution patterns between the advected Atlantic Waters (AW) and Polar waters (PW) and no study reviewed the gelatinous zooplankton seasonality over a full year. The aim of this master thesis is to (1) investigate diversity and distribution patterns between the different water masses and regions of the northern Barents Sea and (2) investigate the gelatinous zooplankton seasonality over a whole year in the northern Barents Sea. For this purpose, during the Nansen Legacy project four seasonal surveys covered the full seasonal cycle of the Barents Sea marginal ice zone and collected both biological and physical data, including gelatinous zooplankton. Overall, 31 gelatinous zooplankton taxa were identified. Fritillaria borealis, Oikopleura sp. and Aeginopsis laurentii were the most abundant taxa and AW and PW influenced areas had different seasonal dynamics and composition, which were significantly influenced by the primary production, the zooplankton biomass, the inflow of AW and the latitudes. Keywords: Gelatinous zooplankton, Barents Sea, Seasonality, Distribution, Atlantic Waters, Polar Waters, Nansen Legacy