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The impact of the rapidly changing Arctic on zooplankton community structure and seasonal behaviour is not yet understood. Here we examine 6 months of under-ice zooplankton observations from the N-ICE2015 expedition (January to June 2015) in the Nansen Basin and on the Yermak Plateau north of Svalbard. Stratified sampling in the water column was done with MultiNet during the entire expedition, and sampling in the upper 5 m below sea ice was performed during April-May by divers using a hand-held net. Hydrographic conditions were dominated by northward-flowing warm and saline Atlantic Water at intermediate depth, and southward-flowing cold Polar Surface Water in the upper 100 m. The mesozooplankton was dominated by copepods. Most numerous were the small ubiquitous Oithona similis in the upper 200 m, with Microcalanus spp. and Triconia borealis further down the water column. Calanus finmarchicus dominated among the Calanus species while Metridia longa was also numerous. The most abundant deep-water copepods were Paraeuchaeta spp. and Spinocalanus spp. Arrow worms (Chaetognatha) and comb jellies (Ctenophora) were the most numerous non-copepods. The mesozooplankton community was more dependent on surrounding water mass characteristics, such as salinity and depth, than geographical location. Algal food availability, which was closely linked to seasonality, explained the community changes seen in surface waters in May and June due to seasonal ascent and recruitment. Seasonal changes from winter to spring mostly involved an increase in the herbivorous C. finmarchicus and its nauplii in the upper 200 m of the water column coinciding with the peak of the phytoplankton bloom in late May. The Yermak Plateau and adjacent Nansen Basin were characterised by oceanic North Atlantic and Arctic species, many of which are deep water specialists. Despite the late onset of the spring bloom due to consolidated sea ice, both North Atlantic and Arctic species successfully reproduced in the study area. This explains the species-rich mesozooplankton community in this region as opposed to the less productive central Arctic Ocean. Future prospects of less sea ice and earlier onset of the bloom will likely be positive for the overall secondary production by both Arctic and boreal zooplankton in this region.

Summary Zooplankton inhabiting the Hornsund and Kongsfjorden fjords on Spitsbergen (Svalbard) were investigated in summer 2013. The goal of the study was to determine how the zooplankton communities vary in environments functioning under different oceanographic regimes. Sampling was conducted with nets of different mesh size and selectivity (56 μm WP-2, 180 μm MultiNet, and 1000 μm Tucker Trawl), which permitted comparing a wide size spectrum of zooplankton components. Species composition did not differ substantially between the fjords, but the zooplankton in Hornsund was almost two times less numerous, and it had lower biomass per unit volume. The highest abundance at both sites was in the smallest zooplankton size fraction found only in samples taken with 56 μm mesh WP-2 net. These comprised as much as 71% and 58% of the total zooplankton abundance in Hornsund and Kongsfjorden, respectively. The communities in both fjords had comparable contributions of Arctic and boreo-Arctic species biomass in the year of the study. However, the comparison of zooplankton characteristics over several years showed changes in abundance and biogeographic structure that corresponded with variations in the physical environments of the fjords. The results of the study permit predicting the possible effects of the increasing influence of Atlantic waters on zooplankton communities inhabiting Arctic marine pelagic ecosystems.

Source at https://doi.org/10.3389/fmars.2019.00293. The Arctic Ocean is changing rapidly with respect to ice cover extent and volume, growth season duration and biological production. Zooplankton are important components in the arctic marine food web, and tightly coupled to the strong seasonality in primary production. In this study, we investigate zooplankton composition, including microzooplankton, copepod nauplii, as well as small and large copepod taxa, and primary productivity in the dynamic Atlantic water inflow area north of Svalbard in May and August 2014. We focus on seasonal differences in the zooplankton community and in primary productivity regimes. More specifically, we examine how a shift from “new” (nitrate based) spring bloom to a “regenerated” (ammonium based) post bloom primary production is reflected in the diversity, life history adaptations and productivity of the dominant zooplankton. North of Svalbard, the seasonal differences in planktonic communities were significant. In spring, the large copepod Calanus finmarchicus dominated, but the estimated production and ingestion rates were low compared to the total primary production. In summer, the zooplankton community was composed of microzooplankton and the small copepod Oithona similis. The zooplankton production and ingestion rates were high in summer, and probably depended heavily on the regenerated primary production associated with the microbial loop. There was clear alteration from dominance of calanoid copepod nauplii in spring to Oithona spp. nauplii in summer, which indicates different reproductive strategies of the dominating large and small copepod species. Our study confirms the dependence and tight coupling between the new (spring bloom) primary production and reproductive adaptations of C. glacialis and C. hyperboreus. In contrast, C. finmarchicus appears able to take advantage of the regenerated summer primary production, which allows it to reach the overwintering stage within one growth season in this region north of Svalbard. This suggests that C. finmarchicus will be able to profit from the predicted increased primary production in the Arctic, a strategy also recognized in small copepod species such as O. similis. We speculate that the ability of the copepod species to utilize the regenerated summer primary production and microbial food web may determine the winners and losers in the future Arctic Ocean.

Zooplankton in Kongsfjorden, Svalbard, is shaped by irregular advection of seawater from the West Spitsbergen Current as well as input of freshwater of glacial and riverine origin. The zooplankton community reflects contributions of Arctic vs. Atlantic water masses in the fjord, and is changing with increasing temperature and declining sea ice. Here, we review zooplankton studies from Kongsfjorden, and present new data from a 20-year time series (1996–2016) of zooplankton abundance/biomass in the fjord based on annual surveys during summer. During the last decade, the marine environment of the West Spitsbergen Shelf and adjacent fjords has undergone changes with increasing temperatures and volume of inflowing Atlantic Water and declining sea ice. Annual monitoring of mesozooplankton since 1996 has shown high seasonal, spatial, and inter-annual variation in species abundance and biomass, and in the proportion of Atlantic and Arctic species. Inter-annual variations in species composition and abundance demonstrate fluctuating patterns related to changes in hydrography. “Warm years” in Kongsfjorden were characterized by higher abundances of Atlantic species, such as Calanus finmarchicus, Oithona atlantica, Thysanoessa longicaudata and Themisto abyssorum. Other krill species, particularly Thysanoessa inermis and to a lesser extent T. longicaudata, increased in abundance during the warming period in 2006–2007, mainly in the inner basin. “Cold years”, on the other hand, were characterized by higher abundance of Themisto libellula. There was no clear impact, however, of changes in environmental factors on the abundance or biomass of the Arctic species Calanus glacialis suggesting that the changes in environmental conditions have not reached critical levels for this species. The long-term zooplankton data demonstrate that some Atlantic species have become more abundant in the Kongsfjorden’s pelagic realm, suggesting that they may benefit from increasing temperature, and also that the total biomass of zooplankton has increased in the fjord implying potentially higher secondary production.

Summary This paper presents information on diet and distribution of larval snailfishes from the genus Liparis on the Canadian Beaufort Sea Shelf. In this study, 153 larval snailfishes of three species, Liparis fabricii, L. gibbus and L. tunicatus, were collected during 4 summer cruises (2003–2005, 2007). The majority of the larvae were either in flexion or post-flexion stage, and some were in pre-flexion stage. Liparis larvae appeared to be generalists in terms of diet and fed on a wide range of planktonic organisms. Pre-flexion larvae fed on small copepods (mainly adult stages of Triconia borealis). As larvae grew their diet shifted towards larger copepods (copepodids III/IV of Calanus hyperboreus, copepodids II–IV of Calanus glacialis and females of Metridia longa) and amphipods (Themisto libellula). Remarkably, larvaceans Oikopleura spp. and pelagic snails Limacina helicina made up a substantial part of the larval diet. This paper contributes to the knowledge on arctic larval fishes and to the ongoing efforts regarding Canadian Beaufort Sea ecosystem modeling.

Source at: http://doi.org/10.3389/fmars.2018.00194 The largest contribution of oceanic heat to the Arctic Ocean is the warm Atlantic Water (AW) inflow through the deep Fram Strait. The AW current also carries Atlantic plankton into the Arctic Basin and this inflow of zooplankton biomass through the Atlantic-Arctic gateway far exceeds the inflow through the shallow Pacific-Arctic gateway. However, because this transport has not yet been adequately quantified based on observational data, the present contribution is poorly defined, and future changes in Arctic zooplankton communities are difficult to project and observe. Our objective was to quantify the inflow of zooplankton biomass through the Fram Strait during different seasons, including winter. We collected data with high spatial resolution covering hydrography (CTD),currents (ADCP and LADCP) and zooplankton distributions (LOPC and MultiNet) from surface to 1,000 m depth along two transects crossing the AW inflow during three cruises in January, May and August 2014. Long-term variations (1997–2016) in the AW inflow were analyzed based on moored current meters. Water transport across the inflow region was of the same order of magnitude during all months (January 2.2 Sv, May 1.9 Sv, August 1.7 Sv). We found a higher variability in zooplankton transport between the months (January 51 kg C s −1 , May 34 kg C s −1 , August 50 kg C s −1), related to seasonal changes in the vertical distribution of zooplankton. However, high abundances of carbon-rich copepods were observed in the AW inflow during all months. Surface patches with high abundances of C. finmarchicus, Microcalanus spp., Pseudocalanus spp., and Oithona similis clearly contributed to the advected biomass, also in winter. The data reveal that the phenology of species is important for the amount of advected biomass, and that the advective input of zooplankton carbon into the Arctic Basin is important during all seasons. The advective zooplankton input might be especially important for mesopelagic planktivorous predators that were recently observed in the region, particularly during winter. The inflow of C. finmarchicus with AW was estimated to be in the order of 500,000 metric tons C y −1 , which compares well to modeled estimates.

The advection of warm Atlantic water into the Arctic influences not only the thermal and sea ice conditions in the Arctic Ocean and the adjacent seas but also the Arctic marine biota. Earlier efforts to characterize the response of zooplankton communities to the increasing influence of warm AW were focused mostly on changes in taxonomic diversity and community structure, but how the zooplankton functional role will evolve under future global warming scenarios remains largely unknown. Based on the zooplankton collection gathered along a thermal gradient from temperate to Arctic marine domains (76-79°N) and an extensive functional trait matrix, we assessed the zooplankton taxonomical and functional structure and diversity under different temperature regimes. The results suggest that the temperature effects zooplankton community structure, taking into account not only the taxonomic, but also functional features. The findings can be used in predicting changes in the pelagic realm in the warming Arctic Ocean, and in constructing and tuning plankton components of ecosystem models.

International audience; The Arctic icescape is rapidly transforming from a thicker multiyear ice cover to a thinner and largely seasonal first-year ice cover with significant consequences for Arctic primary production. One critical challenge is to understand how productivity will change within the next decades. Recent studies have reported extensive phytoplankton blooms beneath ponded sea ice during summer, indicating that satellite-based Arctic annual primary production estimates may be significantly underestimated. Here we present a unique time-series of a phytoplankton spring bloom observed beneath snow-covered Arctic pack ice. The bloom, dominated by the haptophyte algae Phaeocystis pouchetii, caused near depletion of the surface nitrate inventory and a decline in dissolved inorganic carbon by 16 ± 6 g C m−2. Ocean circulation characteristics in the area indicated that the bloom developed in situ despite the snow-covered sea ice. Leads in the dynamic ice cover provided added sunlight necessary to initiate and sustain the bloom. Phytoplankton blooms beneath snow-covered ice might become more common and widespread in the future Arctic Ocean with frequent lead formation due to thinner and more dynamic sea ice despite projected increases in high-Arctic snowfall. This could alter productivity, marine food webs and carbon sequestration in the Arctic Ocean. Annual phytoplankton net primary production in the Arctic Ocean has increased by 30% since the late 1990's mainly due to the declining sea ice extent and an increasing phytoplankton growth season 1. However, there is considerable uncertainty about the future change in Arctic Ocean primary productivity largely attributed to the

A multi-scale approach was used to evaluate which spatial gradient of environmental variability is the most important in structuring zooplankton diversity in the West Spitsbergen Current (WSC). The WSC is the main conveyor of warm and biologically rich Atlantic water to the Arctic Ocean through the Fram Strait. The data set included 85 stratified vertical zooplankton samples (obtained from depths up to 1000 metres) covering two latitudinal sections (76°30’N and 79°N) located across the multi-path WSC system. The results indicate that the most important environmental variables shaping the zooplankton structural and functional diversity and standing stock variability are those associated with depth, whereas variables acting in the horizontal dimension are of lesser importance. Multivariate analysis of the zooplankton assemblages, together with different univariate descriptors of zooplankton diversity, clearly illustrated the segregation of zooplankton taxa in the vertical plane. The epipelagic zone (upper 200 m) hosted plentiful, Oithona similis-dominated assemblages with a high proportion of filter-feeding zooplankton. Although total zooplankton abundance declined in the mesopelagic zone (200–1000 m), zooplankton assemblages in that zone were more diverse and more evenly distributed, with high contributions from both herbivorous and carnivorous taxa. The vertical distribution of integrated biomass (mg DW m-2) indicated that the total zooplankton biomass in the epipelagic and mesopelagic zones was comparable. Environmental gradients acting in the horizontal plane, such as the ones associated with different ice cover and timing of the spring bloom, were reflected in the latitudinal variability in protist community structure and probably caused differences in succession in the zooplankton community. High abundances of Calanus finmarchicus in the WSC core branch suggest the existence of mechanisms advantageous for higher productivity or/and responsible for physical concentration of zooplankton. Our results indicate that regional hydrography plays a primary role in shaping zooplankton variability in the WSC on the way to the Arctic Ocean, with additional effects caused by biological factors related to seasonality in pelagic ecosystem development, resulting in regional differences in food availability or biological production between the continental slope and the deep ocean regions.

One of the main challenges in contemporary biological oceanography is to understand the factors that drive the spatial heterogeneity of pelagic organisms. Our study was performed at 10-m depth intervals within the upper 50 m of the ocean, at two different localities on the West Spitsbergen Shelf in the summers of 2009 and 2010. The fine-scale patterns in vertical zooplankton distribution were studied concurrently with measurements of hydrographic and optical properties of the water. We adopted a novel approach to the acquisition of information on light, phytoplankton and particle distributions by in situ measurements with optical sensors. Based on our data, we distinguished specific zooplankton vertical distribution patterns such as the aggregation of Calanus finmarchicus and small copepods toward the surface and the relatively high contribution of C. glacialis to subsurface layers. A vertical separation of Calanus sp. developmental stages was observed, and zones of rather even zooplankton distributions were also found. The variability in zooplankton distribution and community structure was closely related to the hydrographic and optical characteristics of the water; therefore, we hypothesize that these patterns could be the result of fine-scale microhabitat selection by different zooplankton species and life stages.

We studied summer mesozooplankton composition between 2001 and 2009, in the epipelagic zone of the West Spitsbergen Current (WSC) and adjacent areas, which constitute a transition zone between warmer Atlantic and cold Arctic waters. According to hydrography and species composition, this region could be divided into 4 main areas: western and eastern branches of the WSC, the Greenland Sea together with Fram Strait, and the shelf areas of Spitsbergen and the Barents Sea. The most abundant species was Oithona similis and the most important, in terms of biomass, was Calanus finmarchicus; both species were found at all stations. The novel spatial analysis method of principal coordinates of neighbour matrices (PCNM) and the following variation partitioning were applied to disentangle the contributions of environmental variables and spatial differences in explaining mesozooplankton community variation. In spite of the large geographic area covered, environmental factors used in redundancy analysis (RDA) explained 30.6% of zooplankton variability, while the spatial distribution of sampling stations was responsible for 27.2%, and 12.5% was a common share of both predictors, coming from their correlations. We observed a smooth change from dominance of ubiquitous and boreo-Arctic taxa such as O. similis and Triconia sp. in the beginning of the study period towards stronger dominance of boreal taxa such as C. finmarchicus, which was the most abundant species in 2009.

This paper contributes to baseline knowledge of lower trophic levels that is necessary to monitor the impact of oil and gas development on the Canadian Beaufort Sea ecosystem. As part of the Nahidik Program, the vertical distribution of mesozooplankton was studied along two transects in the coastal Canadian Beaufort Sea in the summer of 2009. Mesozooplankton was collected with 153 μm conical net in two hydrologically distinct layers – the upper layer which was fresher and warmer due to the Mackenzie River runoff, and the lower layer which was colder and more saline. Two separate mesozooplankton assemblages were distinguished in the individual layers. The average zooplankton abundance in the two layers was 3120 ± 2860 ind. m − 3 and 4200 ± 5550 ind. m − 3 in the upper and lower layer, respectively. The upper layer was largely inhabited by meroplanktonic Polychaeta (752 ± 1038 ind. m − 3 ) and Bivalvia larvae (228 ± 307 ind. m − 3 ) as well as by youngest stages of Pseudocalanus spp. (245 ± 499 ind. m − 3 ). Conversely, the lower layer was mainly occupied by typical marine taxa such as Calanus glacialis (95 ± 76 ind. m − 3 ), C. hyperboreus (27 ± 12 ind. m − 3 ) and Triconia borealis (111 ± 81 ind. m − 3 ). Oithona similis , a widely distributed eurytopic cyclopoid copepod, showed no consistent pattern of vertical distribution (280 and 291 ind. m − 3 , in the lower and upper layer, respectively).

Bowhead whales (Balaena mysticetus) of the Bering-Chukchi-Beaufort population form annual late-summer feeding aggregations offshore of the eastern Tuktoyaktuk Peninsula and Cape Bathurst. This region is strongly influenced by episodic upwelling events. A systematic aerial survey (10% coverage) was flown over the eastern shelf on 2 August 2008, revealing large numbers of bowheads (est. 3500 individuals) in a clumped distribution over the continental shelf. Between 7 and 11 August 2008, zooplankton samples and hydrography were obtained from the vicinity of two bowhead feeding aggregations, one at the northeast edge of the continental shelf, and the second off the northeast shore of the Cape Bathurst. Dense aggregations of zooplankton were found in the lower part of the water column (below 40 m), on the shelf, in water with an upwelling signature. The zooplankton were largely resting phases of calanoid copepods (Calanus hyperboreus and C. glacialis) and collectively had twice the abundance, twice the biomass, three times the caloric density and thus six times the energy content of contemporaneous zooplankton samples from the western Canadian Beaufort Shelf. Although upwelling at Cape Bathurst is wind-driven and thus episodic in nature, its consistent delivery of zooplankton to the bowhead foraging area creates conditions attractive to bowhead whales, with an estimated 33% of the bowhead population present on the eastern portion of the shelf at the time of the August 2008 aerial survey.

The Arctic Ocean is facing rapid changes in seawater carbonate chemistry due to the uptake of atmospheric carbon dioxide (CO 2 ). In the current study, the effects of different seawater pH levels (8.2, 7.6 and 6.9) on the reproduction of Calanus glacialis , an Arctic shelf-water copepod, have been quantified. Results indicated that CO 2 -induced seawater acidification had no significant effect on C. glacialis egg production. However, a reduction in pH to 6.9 significantly delayed hatching and possibly reduced overall hatching success. The results of the current study are in agreement with previous studies on other copepod species and would indicate that copepods, as a group, may be well equipped to deal with the chemical changes associated with ocean acidification. However, all previous studies have been over relatively short exposure periods and most have only considered the isolated impacts of elevated CO 2 . Long-term exposures examining the synergistic effects of ocean acidification with other climate stressors, particularly warming on population viability and success, have yet to be conducted.

Kwasniewski, S., Gluchowska, M., Walkusz, W., Karnovsky, N. J., Jakubas, D., Wojczulanis-Jakubas, K., Harding, A. M. A., Goszczko, I., Cisek, M., Beszczynska-Möller, A., Walczowski, W., Weslawski, J. M., and Stempniewicz, L. 2012. Interannual changes in zooplankton on the West Spitsbergen Shelf in relation to hydrography and their consequences for the diet of planktivorous seabirds. – ICES Journal of Marine Science, 69: 890–901. The purpose of the work was to determine how atmospheric and oceanic processes (the North Atlantic Oscillation (NAO) and the Arctic Ocean Oscillation (AOO)) influence hydrography and zooplankton on the West Spitsbergen Shelf (WSS), and the impacts of the processes on chick meals of zooplanktivorous little auks Alle alle. There were distinct Atlantic and Arctic oceanographic domains on the shelf resulting from the presence of the West Spitsbergen Current and the Sørkapp Current, which contain different proportions of Calanus finmarchicus and C. glacialis. The abundance of warm- and cold-water species varied as a result of an interplay between processes in the atmosphere and ocean. In the Arctic domain, on which the study focused, the NAO impacted oceanography, zooplankton, and consequently little auk chick meals, with time-lags of 4–7 years. The diet of little auk chicks was more energy-rich when C. glacialis stage 5 in the Arctic community were more easily available. To date, the changes in zooplankton abundance on the WSS have not posed a threat to the ability of little auks to feed their chicks lipid-rich Arctic copepods.

The distribution and diet of larval and juvenile Arctic cod ( Boreogadus saida ) were studied during summer 2005 in the coastal Canadian Beaufort Sea. A total of 275 individuals were captured and the highest abundance was observed at station depths of 20–30 m. This corresponds well with the location of the frontal zone where the Mackenzie River plume water and open sea water meet. Diet examinations were performed on 220 Arctic cod, which were found undamaged from sampling. We observed a gradual decrease in prey number per fish and increase in prey size as larvae grew which corresponded to a shift from Rotifera and nauplii towards larger copepodid stages. However, at all sizes, the larvae remain generalists and feed on a broad range of organisms. Environmental changes due to climate warming could have a two-fold impact on fish larvae feeding in the studied region. First, the potential for increased primary production may lead to increased zooplankton production that may impact the feeding and nutrition positively. On the other hand, greater discharge of turbid water from the Mackenzie River may reduce light penetration in the water column that may negatively influence the ability of visual predators to successively forage.

Composition and abundance of zooplankton were studied simultaneously with feeding ecology of planktivorous Little Auks (Alle alle) in two different sea shelf areas of West Spitsbergen, Norway, in summer 2007. Zooplankton was collected adjacent to bird colonies in Magdalenefjorden (influenced by Atlantic West Spitsbergen Current) and Hornsund (dominated by the Arctic Sorkapp Current). In spite of different hydrological situations, the abundance of prey preferred by Little Auks, Arctic Calanus glacialis copepodids stage V, among zooplankton was similar in both localities. However, there was much more of Atlantic Calanus finmarchicus on the shelf outside Magdalenefjorden compared to Hornsund, resulting in different abundance ratios of Arctic to Atlantic copepods in the two areas (1:14 and 1:1, respectively). Even greater differences between the two areas occurred in the ratio of C. glacialis CV to other zooplankters, amounting to 1:40 in Magdalenefjorden and 1:6 in Hornsund. In both Little Auk colonies food brought by parents to their chicks contained mainly C. glacialis CV, albeit the proportion of this copepod in meals was significantly higher in Hornsund. Meals delivered to Little Auk chicks in Hornsund had also higher zooplankton numbers, biomass and energy content. In Magdalenefjorden, on the other hand, a higher number of feedings and longer duration of foraging trips were recorded. These differences became more apparent with increasing energy requirements of the fast growing nestlings. This was probably a consequence of lower relative abundance of the Little Auks’ preferred prey in the sea adjacent to Magdalenefjorden colony. It seems that searching for the preferred food items, such as C. glacialis, among abundant but less favored C. finmarchicus, may require more time and energy demanding foraging behavior. As a consequence, foraging effort of the Little Auk parents from Magdalenefjorden was higher, and feeding efficiency lower, than those of birds from Hornsund. Increasing influx of warm Atlantic waters that bring boreal zooplankton to the Arctic Seas may have negative impacts on Little Auks’ time and energy budgets and eventually on their breeding success and range of breeding distribution.

The diel vertical migration (DVM) of zooplankton and pelagic fish in the southern Arctic Ocean (82°N) and in Rijpfjorden (Svalbard, Nordaustlandet, 80°N) was investigated in autumn 2004, when there were distinct differences in light conditions between day and night. We collected data on zooplankton and fish distribution using plankton nets, trawls, and an echo sounder together with data on environmental parameters including sea-ice distribution, hydrography, and in situ fluorescence in the water column. In Rijpfjorden, the Arctic phytoplankton bloom had culminated several weeks prior to the present study and all three Calanus species had migrated down to depths for over wintering and did not show any changes in vertical distribution. However, in the Arctic Ocean pack ice at 82°N, Calanus hyperboreus, was found in high abundances (up to 65 ind. m−3) actively feeding on the Arctic bloom in September. They performed a classic DVM, feeding in the upper 50 m during the night and descending to depths below 50 m during the day. In Rijpfjorden, distinct DVM patterns were observed among the amphipod Themisto libellula, adult and juvenile stages of the pteropod Limacina helicina, and polar cod. Polar cod in Rijpfjorden fed on Calanus spp. and on L. helicina. We conclude that animals display DVM in the Arctic during autumn if they need to feed in food-rich surface waters.

The small, sub-ice copepod Jaschnovia brevis is rich in triacylglycerols, suggesting a feeding behaviour not constrained to the seasonal phytoplankton bloom. The copepod's triacylglycerol reserves contain: the diatom biomarkers 16:1n-7 (23.9%), 20:5n-3 (8.5%) and C16 PUFA (1.3%), the flagellate biomarkers 18:4n-3 (3.7%) and 22:6n-3 (3.3%), and the Calanus copepod biomarkers 20:1n-9 (7.7%) and 22:1n-11 (6.2%). Total lipid from particulates in the water column contained polar lipid (45.0%), wax esters (24.9%) and triacylglycerols (11.2%) as major components. The total lipids in the particulates were rich in 18:1n-9 (31.5%) and 16:0 (21.2%), and relatively rich in 18:0 (7.8%) and 18:2n-6 (9.2%). The triacylglycerols in the particulates contained 16:1n-7 (20.7%), C16 PUFA (4.1%), 18:4n-3 (1.9%), 20:5n-3 (3.6%), 22:6n-3 (1.9%), 20:1n-9 (5.2%) and 22:1n-11 (3.9%). The polar lipids in the particulates contained 16:1n-7 (17.3%), C16 PUFA (7.8%), 18:4n-3 (3.3%), 20:5n-3 (14.5%) and 22:6n-3 (9.6%). The fatty alcohols in the wax esters of the particulates were mainly 16:0 (11.3%), 20:1n-9 (21.1%) and 22:1n-11 (30.6%). The nature of the particulates, their possible origin in living and non-living material, and their role in the nutrition of J. brevis are discussed.

The lipid class compositions of the ctenophores Mertensia ovum and Beroe cucumis were very similar, with polar lipid and wax esters each accounting for 35 to 40% of the total. The fatty acid compositions of the polar lipids in the 2 species were essentially the same, with 22:6n3 and 20:5n3 in a ratio of 2:1 accounting for more than 40% of the total. The fatty acid and fatty alcohol com- positions of the wax esters of both species were also essentially the same, with 20:1n9 and 22:1n11 fatty alcohols present in equal amounts accounting for 60% of the total fatty alcohol composition. The fatty acid and fatty alcohol compositions of the wax esters of M. ovum and B. cucumis were averaged and compared, using principal component analyses, to averages derived from published data for the potential prey species: Calanus finmarchicus, C. glacialis, C. hyperboreus, Pseudocalanus acuspes, Acartia longiremis and Metridia longa. The results were consistent with Calanus spp., especially C. glacialis, being the major prey of M. ovum and with M. ovum being the major prey of B. cucumis.

The percentage (%) fatty alcohol and fatty acid compositions of the wax esters of large numbers of Stage V and females of Calanus hyperboreus, C. glacialis and C. finmarchicus taken in late August to late September from Arctic waters (Kongsfjord in Svalbard, 78° 57' N, 11° 50' E) are presented. The data reveal that these stages of development of the 3 species can be discriminated on the basis of the % of 22:1n-11 fatty alcohol in their large levels of wax esters, with C. hyperboreus having the highest % followed by C. finmarchicus and then C. glacialis. Equally, C. hyperboreus has the lowest % of 20:1n-9 fatty alcohol in its wax esters with C. finmarchicus having a higher % and C. glacialis the highest %. Relatively minor differences occur in the fatty acid compositions of the wax esters of the 3 species, which consisted principally of 20:1n-9 (15 to 18%) and 22:1n-11 (10 to 15%), together with the diatom-derived fatty acids 16:1n-7 (20 to 23%) and 20:5n-3 (11 to 13%). The flagellate-derived fatty acids, 18:4n-3 (3 to 6%) and 22:6n-3 (1 to 3%), were minor constituents. The fatty acid compositions of the small amounts of polar lipid in the 3 species were indistinguishable with 22:6n-3 (41 to 46%) and 20:5n-3 (22 to 24%) being the major components. We conclude that Stage V and females of the species can be distinguished in autumn on the basis of the different % of 22:1n-11 and 20:1n-9 fatty alcohols in their wax esters and that de novo lipid biosynthetic activity in the cope- pods increases in the order C. finmarchicus < C. glacialis < C. hyperboreus. We discuss the results in terms of the contributions of fatty acids and fatty alcohols biosynthesised de novo and fatty acids derived from the diet to the copepods' lipids, the role of 20:1 and 22:1 fatty alcohols and fatty acids as energy sources, and the possible role of 22:6n-3 in the copepods' physiology.

The complete diet composition structure of the most numerous planktivorous sea bird, little auk (Alle alle), in the European Arctic, is still not fully recognized. Although regular constituents of little auk chick diets, the copepods, Calanus glacialis and C. finmarchicus have been previously relatively well described, more taxa were frequent ingredients of the bird’s meals. Therefore, the role of the little auks supplementary diet components (SDCs) at two colonies in the Svalbard Archipelago, Hornsund and Magdalenefjorden, in 2007–2009, is a main subject of this comparative study. Because the SDCs often consisted of scarce but large zooplankters, this investigation was focused on biomass as a proxy of the SDCs’ energy input. Although the total biomass of the food delivered to chicks in both colonies was similar, in Magdalenefjorden, the proportion of SDCs was twice that found in Hornsund. The main SDCs in Hornsund were Decapoda larvae (with predominating Pagurus pubescens) and Thysanoessa inermis, whereas the main SDCs in Magdalenefjorden were C. hyperboreus and Apherusa glacialis. Previous investigations, which indicated lipid richness of SDCs, together with our ecological results from the colonies, suggest that this category might play a compensatory role in little auk chick diets. The ability to forage on diverse taxa may help the birds to adapt to ongoing Arctic ecosystem changes.

Lipid class and fatty acid compositions were determined in Limacina helicina and Clione limacina from an Arctic fjord and the marginal ice zone around Svalbard. C. limacina had higher levels of neutral lipids, including both alkyldiacylglycerols (ADG) and triacylglycerols (TAG), than L. helicina, which contained mainly TAG. However, considerable heterogeneity in the lipid classes and their fatty acids/alcohols were observed in C. limacina in that only two out of the seven specimens analysed were lipid-rich and contained both ADG and TAG, the others having only low percentages of TAG. In specimens of C. limacina containing ADG, 15:0 and 17:1n-8 were prominent fatty acids in both ADG and TAG. The fatty acids of the TAG of L. helicina were variable but 15:0 and 17:1n-8 were absent. We consider the heterogeneity in the fatty acid compositions of L. helicina to reflect temporal and spatial variability in the animals' predominantly phytoplanktonic and particulate diet, which occasionally includes small copepods. We further consider L. helicina to be the prime food for C. limacina and the noticeable amounts of 22:1 found in one sample of C. limacina to reflect significant input of Calanus either directly or indirectly through their prime food, L. helicina. We view the heterogeneity in the fatty acid compositions of both L. helicina and C. limacina, as well as the ability of C. limacina to biosynthesise WE, ADG, 15:0, and 17:1n-8, as adaptations to a large variation of food availability that enables C. limacina to synthesise lipids rapidly and flexibly. Thus, the lipid biochemistry of C. limacina is important in enabling the species to thrive in strong pulses in polar systems.