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Throughout all oceans, aggregations of zooplankton and ichthyoplankton appear as horizontal sound scattering layers (SSLs) when detected with active acoustic techniques. Quantifying the composition and density of these layers is prone to sampling biases. We conducted a net and trawl survey of the epipelagic fauna in northern Norway (70° N) in June 2018 while an autonomous surface vehicle equipped with a broadband echosounder (283–383 kHz) surveyed the same region. Densities from the autonomous hydroacoustic survey were calculated using forward estimates from the relative density from the net and trawl, and inversion estimates with statistical data-fitting. All four methods (net, trawl, acoustic forward and inverse methods) identified that copepods dominated the epipelagic SSL, while pteropods, amphipods and fish larvae were present in low densities. The density estimates calculated with the inverse method were higher for mobile zooplankton, such as euphausiid larvae, than with the other methods. We concluded that the inverse method applied to broadband autonomous acoustic surveys can improve density estimates of epipelagic organisms by diminishing avoidance biases and increasing the spatio-temporal resolution of ship-based surveys.

This is the second paper in a series of two, which analyze the position of the Barents Sea ice-edge (BIE) based on a 442-year long dataset to understand its time variations. The data have been collected from ship-logs, polar expeditions, and hunters in addition to airplanes and satellites in recent times. Our main result is that the BIE position alternates between a southern and a northern position followed by Gulf Stream Beats (GSBs) at the occurrence of deep solar minima. We decompose the low frequency BIE position variations in cycles composed of dominant periods which are related to the Jose period of 179 years, indicating planetary forcings. We propose that the mechanism transferring planetary signals into changes in BIE position is the solar wind (SW), which provides magnetic shielding of the Earth in addition to geomagnetic disturbances. Increase in the solar wind produces pressure which decelerates the Earth’s rotation. It also transfers electrical energy to the ring current in the earth’s magnetosphere. This current magnetizes the earth’s solid core and makes it rotate faster. To conserve angular momentum the earth’s outer fluid mantle rotates slower with a delay of about 100 years. In addition will geomagnetic storms, initiated by solar coronal mass ejections (CMEs) penetrate deep in the Earth’s atmosphere and change pressure pattern in the Arctic. This effect is larger during solar minima since the magnetic shielding then is reduced. The Arctic may then experience local warming. The transition of solar activities to a possibly deep and long minimum in the present century may indicate Arctic cooling and the BIE moving south this century. For the North Atlantic region, effects of the BIE expanding southward will have noticeable consequences for the ocean bio-production from about 2040.

A comparative study into the daily dynamics of the lipid and fatty-acid profile and the level of energy metabolism was conducted for the first time in young fishes of the daubed shanny L2, L3, L4, L4*, L5 stages of development, which are links of pelagic (L2, L3, L4) and benthic (L4, L4*, L5) food chain) from Kongs Fjord Bay in polar night conditions. Daily dynamics of lipid components and the activity of anaerobic exchange enzymes can be considered as one of the mechanisms of genetically determined ontogenetic and environmentally oriented phenotypic heterogeneity of the life strategy of the species, which is aimed at maintaining its existence in specific environmental conditions and adaptation to them at different levels of life organization.

This is the first report of the Barents Sea Ice Edge (BIE) project. The BIE position has varied between latitude 76°N and above 82°N during the last 440 years. During the period 10,000 to 6000 years ago, Arctic climate was significantly warmer than today. We review various oceanic and atmospheric factors that may have an effect on the BIE position. The Gulf Stream beat with respect to alternations in flow intensity and N-S distribution plays a central role for the changes in climate and BIE position during the last millennium. This occurred in combination with external forcing from total solar irradiation, Earth’s shielding strength, Earth’s geomagnetic field intensity, Earth’s rotation, jet stream changes; all factors of which are ultimately driven by the planetary beat on the Sun, the Earth and the Earth-Moon system. During the last 20 years, we see signs of changes and shifts that may signal the end of the late 20th century warm period. The BIE position is likely to start advancing southward in next decade.

Effective ocean management requires integrated and sustainable ocean observing systems enabling us to map and understand ecosystem properties and the effects of human activities. Autonomous subsurface and surface vehicles, here collectively referred to as “gliders”, are part of such ocean observing systems providing high spatiotemporal resolution. In this paper, we present some of the results achieved through the project “Unmanned ocean vehicles, a flexible and cost-efficient offshore monitoring and data management approach—GLIDER”. In this project, three autonomous surface and underwater vehicles were deployed along the Lofoten–Vesterålen (LoVe) shelf-slope-oceanic system, in Arctic Norway. The aim of this effort was to test whether gliders equipped with novel sensors could effectively perform ecosystem surveys by recording physical, biogeochemical, and biological data simultaneously. From March to September 2018, a period of high biological activity in the area, the gliders were able to record a set of environmental parameters, including temperature, salinity, and oxygen, map the spatiotemporal distribution of zooplankton, and record cetacean vocalizations and anthropogenic noise. A subset of these parameters was effectively employed in near-real-time data assimilative ocean circulation models, improving their local predictive skills. The results presented here demonstrate that autonomous gliders can be effective long-term, remote, noninvasive ecosystem monitoring and research platforms capable of operating in high-latitude marine ecosystems. Accordingly, these platforms can record high-quality baseline environmental data in areas where extractive activities are planned and provide much-needed information for operational and management purposes.

A fatty acid content of structural (phospholipids, PLs) and storage (triacylglycerols, TAGs) lipids in muscles of daubed shanny Leptoclinus maculatus postlarvae from Kongsfjord (Svalbard archipelago waters) was studied. A high level of monounsaturated fatty acids (MUFAs), mainly due to 20:1(n-9) and 22:1(n-11), was shown in TAGs of daubed shanny muscles at the L2 stage of larval development. Polyunsaturated fatty acids (PUFAs) were found to dominate in PLs due to n-3, mainly 20:5(n-3) and 22:6(n-3), fatty acids. The ∑n-3/∑n-6 PUFA index was established to be 2-fold higher in PLs compared to TAGs (9.7 vs. 4.1). The fatty acid profile at the L1 stage of larval development was characterized by a pronounced specificity: a highest content of saturated fatty acids (SFA) due to 16:0 and a dominance of 18:1(n-9) among MUFAs. Our results demonstrate the age-related specificity of the fatty acid content of PLs and TAGs in daubed shanny muscles, which determines their functional significance and reflects both feeding features and the physiological state of the daubed shanny at different stages of its development under the Arctic conditions.

Accepted manuscript version, licensed CC BY-NC-ND 4.0. Source at https://doi.org/10.1038/s41598-018-37129-x. Zooplankton provide the key link between primary production and higher levels of the marine food web and they play an important role in mediating carbon sequestration in the ocean. All commercially harvested fish species depend on zooplankton populations. However, spatio-temporal distributions of zooplankton are notoriously difficult to quantify from ships. We know that zooplankton can form large aggregations that visibly change the color of the sea, but the scale and mechanisms producing these features are poorly known. Here we show that large surface patches (>1000 km2) of the red colored copepod Calanus finmarchicus can be identified from satellite observations of ocean color. Such observations provide the most comprehensive view of the distribution of a zooplankton species to date, and alter our understanding of the behavior of this key zooplankton species. Moreover, our findings suggest that high concentrations of astaxanthin-rich zooplankton can degrade the performance of standard blue-green reflectance ratio algorithms in operational use for retrieving chlorophyll concentrations from ocean color remote sensing.

This is a post-peer-review, pre-copyedit version of an article published in Polar Biology. The final authenticated version is available online at: https://doi.org/10.1007/s00300-020-02669-4. Recent discoveries of high levels of biological activity in the Arctic marine ecosystems during the polar night raise questions regarding the ecophysiology of the pelagic postlarval daubed shanny Leptoclinus maculatus. Of special interest is the composition of the lipid sac—a unique feature not found in other Arctic fishes. Analysis of the fatty acid content of major classes of lipids as membrane—total phospholipids (PL) and storage—triacylglycerols (TAG) in the different postlarvae stages during the polar night is presented in this work for the first time. A high level of monounsaturated fatty acids (MUFAs) (71–74% of the total fatty acids (FA) of TAG) was found in the TAG of the L3-L4* postlarvae stages, among which 20:1(n-9) (28%) and 22:1(n-11) (27–29%) FAs are trophic biomarkers of the zooplankton Calanus spp. Among the polyunsaturated FA (PUFA), the FAs of (n-3) class were dominated (22:6(n-3)—in the PL, and 18:4(n-3)—in the TAG). A decrease in the content of the saturated FA (SFA) and an increase in the MUFA in the structural PL during the transition from the postlarval to the demersal stage were observed. Our analyses of the FA composition of the lipid sac suggest that the fish continues to actively hunt for its preferred prey item Calanus spp. during the polar night.

The seasonal dynamic of lipids and their fatty acid constituents in the lipid sac and muscles of pelagic postlarval Leptoclinus maculatus, an ecologically important fish species in the Arctic food nets, in Kongsfjord, Svalbard waters was studied. The determination of the qualitative and quantitative content of the total lipids (TLs), total phospholipids (PLs), triacylglycerols (TAGs), cholesterol (Chol), cholesterol esters (Chol esters) and wax esters was analyzed by TLC, the phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylcholine (PC), lysophosphatidylcholine (LPC) and sphingomyelin (SM) were determined by HPLC, and fatty acids of total lipids using GC. The lipid sac is a system of cavities filled with lipids, and it is not directly connected to organs of the digestive system. The wall&rsquo, s inner layer is a multinuclear symplast that has a trophic function. The results provide additional knowledge on the role of lipids in the biochemical and physiological adaptation of fish to specific environments and clarify the relationship between fatty acids and the food specialization of postlarvae. Analysis of the fatty acid (FA) profile of TLs in the muscles and lipid sac of daubed shanny pelagic postlarvae showed it to be tissue- and organ-specific, and tightly associated with seasonal variations of environmental factors (temperature conditions and trophic resources).

Isfjorden, a broad Arctic fjord in western Spitsbergen, has shown significant changes in hydrography and inflow of Atlantic Water (AW) the last decades that only recently have been observed in the Arctic Ocean north of Svalbard. Variability and trends in this fjord’s climate and circulation are therefore analysed from observational and reanalysis data during 1987 to 2017. Isfjorden experienced a shift in summer ocean structure in 2006, from AW generally in the bottom layer to AW (with increasing thickness) higher up in the water column. This shift, and a concomitant shift to less fast ice in Isfjorden are linked to positive trends in the mean sea surface temperature (SST) and volume weighted mean temperature (VT) in winter (SSTw/VTw: 0.7 ± 0.1/0.9 ± 0.3 °C 10 yr−1) and summer (SSTS/VTS: 0.7 ± 0.1/0.6 ± 0.1 °C 10 yr−1). Hence, the local mean air temperature shows similar trends in winter (1.9 ± 0.4 °C 10 yr−1) and summer (0.7 ± 0.1 °C 10 yr−1). Positive trends in volume weighted mean salinity in winter (0.21 ± 0.06 10 yr−1) and summer (0.07 ± 0.05 10 yr−1) suggest increased AW advection as a main reason for Isfjorden’s climate change. Local mean air temperature correlates significantly with sea ice cover, SST, and VT, revealing the fjord’s impact on the local terrestrial climate. In line with the shift in summer ocean structure, Isfjorden has changed from an Arctic type fjord dominated by Winter Deep and Winter Intermediate thermal and haline convection, to a fjord dominated by deep thermal convection of Atlantic type water (Winter Open). AW indexes for the mouth and Isfjorden proper show that AW influence has been common in winter over the last decade. Alternating occurrence of Arctic and Atlantic type water at the mouth mirrors the geostrophic control imposed by the Spitsbergen Polar Current (carrying Arctic Water) relative to the strength of the Spitsbergen Trough Current (carrying AW). During high AW impact events, Atlantic type water propagates into the fjord according to the cyclonic circulation along isobaths corresponding to the winter convection. Tides play a minor role in the variance in the currents, but are important in the side fjords where exchange with the warmer Isfjorden proper occurs in winter. This study demonstrates that Isfjorden and its ocean climate can be used as an indicator for climate change in the Arctic Ocean. The used methods may constitute a set of helpful tools for future studies also outside the Svalbard Archipelago.

Pelagic communities play a key role in Arctic ecosystems. Although zooplankton occupy several different trophic levels in the food chain, their primary niche is often considered that of a link between pelagic and ice-associated primary production on one side and higher trophic levels on the other. In fact, most of the biological energy (organic carbon) ending up in top predators such as seabirds, fish and marine mammals have been funnelled through one or more zooplankton species. As such, zooplankton ecology is often viewed and understood in relation to primary production regimes. However, recent research has also showed that processes occurring in the zooplankton community during winter are crucial for our understanding of Polar Night ecology. As a group, they are active throughout the entire year, they conduct various forms of vertical migration in relation to both the moon and solar background illumination and some species utilize the Polar Night for reproduction. Evidence of reproduction among short-lived omnivorous zooplankton species during the Polar Night suggests that production is sustained by feeding opportunistically throughout winter and Polar Night and that life history strategies are tuned to support fast turnover rates and not on building up large lipid reserves. This chapter provides an overview of the main zooplankton taxa inhabiting Arctic waters during the Polar Night and describes the main processes typical for zooplankton taxa during the Polar Night.

Accepted manuscript version, licensed CC BY-NC-ND 4.0. Published version available at https://doi.org/10.1016/j.marenvres.2018.09.004. Due to retreating sea ice and predictions of undiscovered oil and gas resources, increased activity in Arctic shelf sea areas associated with shipping and oil and gas exploration is expected. Such activities may accidentally lead to oil spills in partly ice-covered ocean areas, which raises issues related to oil spill response. Net Environmental Benefit Analysis (NEBA) is the process that the response community uses to identify which combination of response strategies minimises the impact to environment and people. The vulnerability of Valued Ecosystem Components (VEC's) to oil pollution depends on their sensitivity to oil and the likelihood that they will be exposed to oil. As such, NEBA requires a good ecological knowledge base on biodiversity, species' distributions in time and space, and timing of ecological events. Biological resources found at interfaces (e.g., air/water, ice/water or water/coastline) are in general vulnerable because that is where oil can accumulate. Here, we summarize recent information about the seasonal, physical and ecological processes in Arctic waters and evaluate the importance these processes when considering in oil spill response decision making through NEBA. In spring-time, many boreal species conduct a lateral migration northwards in response to sea ice retraction and increased production associated with the spring bloom. However, many Arctic species, including fish, seabirds and marine mammals, are present in upper water layers in the Arctic throughout the year, and recent research has demonstrated that bioactivity during the Arctic winter is higher than previously assumed. Information on the seasonal presence/absence of less resilient VEC's such as marine mammals and sea birds in combination with the presence/absence of sea ice seems to be especially crucial to consider in a NEBA. In addition, quantification of the potential impact of different, realistic spill sizes on the energy cascade following the spring bloom at the ice-edge would provide important information for assessing ecosystem effects.

Phenological variations of the marine copepod Calanus finmarchicus were studied in Svalbard and northern Iceland, where samples were collected in summer and spring, respectively, over two decades. ...

The daubed shanny Leptoclinus maculatus is a relatively common fish species in Svalbard waters, but little is known about its reproduction. In total, 207 specimens (76 females, 131 males) were collected and examined. Gonadosomatic (GSI) and hepatosomatic indices were significantly higher in females (mean 2.8 and 2.7%, respectively) than males (mean 0.3 and 1.8%) in all seasons. The GSI of females was highest during autumn and winter (18.5%) while the GSI of males was highest in winter (1.7%). Females become sexually mature at 125 mm standard length (SL) and 7 years of age while males become sexually mature at similar length and 6 years of age. The number of oocytes in gonads increased with SL and age and comprised two groups: (1) 115–124 mm SL, 5–7 g gutted weight (GW) and 5–6 years of age with potential fecundity of 950–1850 oocytes, (2) 125–134 mm SL, 7–9 g GW and 7–12 years of age with 1250–2800 oocytes. The daubed shanny seems to spawn all its ripe oocytes during one spawning event each year. Fish become sexually dimorphic after maturation, and differences in sexual morphology are likely linked to reproduction, with female parental care and territorial defence for males. The reproductive strategy of daubed shanny is characterized by late maturation, relatively low fecundity and large size of offspring, i.e. large investment in relatively few offspring.

The patterns of growth and development have been studied in L. maculatus early life stages of different ecological groups (pelagic and demersal) from Kongsfjorden and Billefjorden (the northwestern coast of West Spitsbergen). It has been found that the growth rate of larvae markedly increases by age 2+ (stage L2), which is due to their transition to exogenous feeding. Consideration is given to changes in the length and condition of the lipid sac (a provisory organ) in the period of its formation, growth, and resorption in the course of ontogeny. The lipid sac reaches the maximum size at stage L4* and is resorbed at stage L5. Analysis of individual variation in the size and body weight of fish early life stages provides the possibility to evaluate the adaptation capacity of a species under specific conditions of the Arctic.

For oil spill responses, assessment of the potential environmental exposure and impacts of a spill is crucial. Due to a lack of chronic toxicity data, acute data is used together with precautionary assumptions. The effect on the Arctic keystone (copepod) species Calanus hyperboreus and Calanus glacialis populations is compared using two approaches: a precautionary approach where all exposed individuals die above a defined threshold concentration and a refined (full-dose-response) approach. For this purpose a matrix population model parameterised with data from the literature is used. Population effects of continuous exposures with varying durations were modelled on a range of concentrations. Just above the chronic No Observed Effect Concentration (which is field relevant) the estimated population recovery duration of the precautionary approach was more than 300 times that of the refined approach. With increasing exposure concentration and duration, the effect in the refined approach converges to the maximum effect assumed in the precautionary approach.

The content of total phospholipids and their classes (phosphatidylinositol, phosphatidylserine, phosphatidylethanolamine, phosphatidylcholine, sphingomyelin) of muscles (flesh) and lipid sac of different developmental stages of young fish the daubed shanny, Leptoclinus maculatus from Kongsfjord (Svalbard, Norway) in winter was studied. The content of phospholipids in flesh decreases with age on account of phosphatidylcholine and phosphatidylethanolamine that probably related to their role in morphogenesis during differentiation of tissues and organs. The content of phospholipids is lower than reserve lipids in the lipid sac. The level of phospholipids in the lipid sac compared to flesh increases with age of fish reaching the maximum in benthic juveniles. Variations of minor phospholipids content of young fish of the daubed shanny indicate their participation in biochemical mechanisms of adaptation realizing in specific and varying Arctic conditions.

In the advective realm of the seas, it is challenging to disentangle the role of regional and local processes on zooplankton populations. However, comparative studies of spatially separated zooplankton populations can provide valuable insights into this issue. We studied interannual abundance variation of the key zooplankton species Calanus finmarchicus and C. hyperboreus in three near-shore locations of the Nordic Seas: off northern Norway, Svalbard, and northern Iceland. Average abundances of both species were similar among locations, while in each location the abundance of C. finmarchicus was about an order of magnitude higher than the abundance of C. hyperboreus. The abundance of both species decreased in northern Norway, while C. finmarchicus abundance increased in northern Iceland. C. finmarchicus abundance in northern Norway covaried with regional climate, while the Svalbard Calanus populations were related to local environment (hydrography, phytoplankton). In northern Iceland, C. finmarchicus abundance covaried with local environmental factors, while C. hyperboreus abundance covaried with climate variability. Top-down forcing could not be investigated. The results indicate that the mechanisms relating regional climate variability (North Atlantic and Arctic oscillations) to Calanus abundance are mediated through advection of water masses, while more local environmental variability involved bottom-up processes or advection.

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 Bare...

The dynamics of lipid and fatty acid composition of the muscles (flesh) and lipid sac in L. maculatus early life stages of different age collected in Kongsfjorden (Svalbard, Norway), in winter, during the polar night was studied. We showed that the total lipid content in the muscles increases on account of energetic triacylglycerols derived from the lipid sac, which is resorbed in juveniles as they switch to a demersal mode of life. The fatty acid spectrum directly reflects age-dependent and seasonal features of L. maculatus early life stages. The results of the study elucidate the specific role of lipids and fatty acids in the ecological and biochemical mechanisms related to ontogenic development of fish from the family Stichaeidae, particularly arctic-boreal L. maculatus, which assumed to become increasingly frequent in the Spitsbergen water area. They are important for understanding the ability of organisms to maintain and preserve the functional stability of ecosystems as a whole, especially under conditions of climate change in the Arctic.

Observations of spatial and temporal distribution of low and mid trophic level organisms traditionally rely on ship-based measurements. The integration of fisheries research echosounders on surface and sub-surface unmanned vehicles change this situation and facilitate persistent monitoring of these trophic levels. Additionally, concurrent observations by surface and subsurface vehicles with appropriate sensors facilitate measurements of physical and biological processes at appropriate spatial and temporal scales, needed in order to sufficiently resolve the connected variability of physical and biological processes in the oceans. The GLIDER project implements this approach by utilizing three unmanned vehicles with a suite of sensors for persistent marine monitoring. Integration of a low power scientific echosounder in two of the autonomous surface vehicles are discussed in this paper; a Wave Glider (Liquid Robotics, Maritime Robotics) and a Sailbuoy (Offshore Sensing). Both vehicles are compact, cost-efficient platforms for persistent marine monitoring. We discuss key features of the systems and challenges in ensuring the collection of high-quality echosounder data. Experiences with the systems and examples of zooplankton echosounder data, collected over a period of six months on the highly productive Norwegian shelf outside Lofoten-Vesteralen, are presented and discussed.

The overall aim of the GLIDER project is to demonstrate an innovative, flexible and cost-efficient offshore monitoring and data management approach. GLIDER consists in the deployment of 3 ocean autonomous and mobile platforms, a Sea glider (Kongsberg), a Sailbuoy (Offshore Sensing) and a Wave Glider (Maritime Robotics), fitted with a well proven suite of sensors to collect chemical, physical and biological data of the ocean space. The aim is to increase the sampling of high quality marine environmental data and provide more flexible sampling schemes. These state-of-the-art platforms can move in space, provide long-term and real-time monitoring, and in addition reduce costs and CO2 emission compared to other traditional measurement approaches. A data management e-platform has been developed along with scientists and consultants to ensure a high integration of the collected data. The e-platform will allow to manage the data from storage approach, to visualization tools, and finally to allow interpretation and use for different end users. We have successfully deployed the three vehicles fitted with sensors from March to September 2018 in the Lofoten - Vesteralen area along the Norwegian coast above the Arctic circle (67°16'48''N 14°24'00''E ) with the objective to get a better understanding of the ecosystem during the spawning period of the Atlantic cod. The data collected revealed that the autonomous vehicles provide scientific information of a completely undisturbed ecosystem unlike what is collected from traditional research vessels from which instruments are deployed. The survey provided significant gain on the understanding on the dynamic and timing of biological events over large spatial and temporal scale. Furthermore, we have successfully assimilated data in real time into oceanographic model in order to improve the forecast. Currently, data are being analyzed to understand the ecosystem from the primary production to zooplankton, fish larvae, adult fish and sea mammals. Analysis will offer i) baseline data on a large spatial scale ii) professional solutions to industry operating in the marine environment iii) scientific data for improving knowledge in ecosystem functioning and structure and iv) input data into existing models (oceanography, weather and ecology).

Life cycle and reproduction of Calanus hyperboreus were studied during a year of record low ice cover in the southeastern Beaufort Sea. Stages CIV, adult females and CV dominated the overwintering population, suggesting a 2- to 3-year life cycle. Within two spring-summer months in the upper water column females filled their energy reserves before initiating their downward seasonal migration. From February to March, vigorous reproduction (20–65 eggs f−1 d−1) delivered numerous eggs (29 000 eggs m−2) at depth and nauplii N1-N3 (17 000 ind. m−2) in the water column. However, CI copepodite recruitment in May, coincident with the phytoplankton bloom, was modest in Amundsen Gulf compared to sites outside the gulf. Consequently, C. hyperboreus abundance and biomass stagnated throughout summer in Amundsen Gulf. As a mismatch between the first-feeding stages and food was unlikely under the favourable feeding conditions of April-May 2008, predation on the egg and larval stages in late winter presumably limited subsequent recruitment and population growth. Particularly abundant in Amundsen Gulf, the copepods Metridia longa and C. glacialis were likely important consumers of C. hyperboreus eggs and nauplii. With the ongoing climate-driven lengthening of the ice-free season, intensification of top-down control of C. hyperboreus recruitment by thriving populations of mesopelagic omnivores and carnivores like M. longa may counteract the potential benefits of increased primary production over the Arctic shelves margins for this key prey of pelagic fish, seabirds and the bowhead whale.

This book summarizes physical and biological aspects from Kongsfjorden (78° 59’ N, 11–12° E), Svalbard. The contributions to this volume cover atmospheric conditions above Ny-Alesund, as well as physical conditions in Kongsfjorden. The chapters about oceanographic dynamics and sea ice conditions are based on time-series observations of interannual variability, whereas the chapter about the underwater light regime focuses on seasonal dynamics. The pelagic system is covered by reviews of pelagic production, phytoplankton and zooplankton communities. Benthic flora studies address microphytobenthos and macroalgal biodiversity, as well as the physiology of kelp related to stress perception and responses. Benthic fauna communities are described with associated environmental drivers of change. An outline of an Arctic fjord ecosystem model for Kongsfjorden- Krossfjorden is presented. Data that go into models come from sampling at different stations in the marine environment, with an important contribution from long-term data series at stations. Some of the long-term data are based on recordings from autonomous underwater observatories. Finally, one summary presents Kongsfjorden as harbinger of the future Arctic.

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.

The fatty acid (FA) composition has been analysed in the blubber of 56 minke whales caught during the Norwegian commercial whaling period in 2009–2011. Minke whales from four regions were sampled: the North Sea, Vesteralen, Spitsbergen/Bear Island and Finnmark. The FA profiles of the whale blubber have been compared with FA profiles of potential prey species to investigate if FA analysis can be used to predict the diet of minke whales and how the FA profiles of the blubber reflect the regional ecosystem in which the whales were caught. Clear differences in blubber FA profiles were found between minke whales from different areas, and the results of the present study show that FA analysis of the blubber can be used to indicate the whale's diet, but there appears to be a strong impact from metabolism on several FAs. The whale blubber FAs are separate from those of the prey by having relatively high levels of FAs likely to originate from endogenous metabolism, such as 18:1n9 (Δ9-desaturation of 18:0);...

This is a pre-copyedited, author-produced version of an article accepted for publication in ICES Journal of Marine Science following peer review. The version of record Renaud, P.E., Daase, M., Banas, N.S., Gabrielsen, T.M., Søreide, J.E., Varpe, Ø., ... Berge, J. (2018). Pelagic food-webs in a changing Arctic: a trait-based perspective suggests a mode of resilience. ICES Journal of Marine Science, is available online at: https://doi.org/10.1093/icesjms/fsy063. Arctic marine ecosystems support fisheries of significant and increasing economic and nutritional value. Commercial stocks are sustained by pelagic food webs with relatively few keystone taxa mediating energy transfer to higher trophic levels, and it remains largely unknown how these taxa will be affected by changing climate and the influx of boreal taxa. Calanus species store large quantities of lipids, making these zooplankton a critical link in marine food-webs. The Arctic Calanus species are usually larger and, importantly, have been suggested to contain disproportionately larger lipid stores than their boreal congeners. Continued climate warming and subsequent changes in primary production regimes have been predicted to lead to a shift from the larger, lipid-rich Arctic species, Calanus glacialis and Calanus hyperboreus, toward the smaller, boreal Calanus finmarchicus in the European Arctic, with negative consequences for top predators. Our data show that lipid content is closely related to body size for all three species, i.e. is not a species-specific trait, and that there is considerable overlap in size between C. finmarchicus and C. glacialis. A trait-based life-history model was used to examine an idealized scenario where, in a changed Arctic with a longer period of primary production, C. glacialis- and C. hyperboreus-like copepods are indeed replaced by C. finmarchicus-like individuals, whether through competition, plasticity, hybridization, or evolution. However, the model finds that transfer of energy from primary producers to higher predators may actually be more efficient in this future scenario, because of the changes in generation length and population turnover rate that accompany the body-size shifts. These findings suggest that Arctic marine food webs may be more resilient to climate-related shifts in the Calanus complex than previously assumed.

Underwater light regime is controlled by distribution and optical properties of colored dissolved organic matter (CDOM) and particulate matter. The Fram Strait is a region where two contrasting water masses are found. Polar water in the East Greenland Current (EGC) and Atlantic water in the West Spitsbergen Current (WSC) differ with regards to temperature, salinity and optical properties. We present data on absorption properties of CDOM and particles across the Fram Strait (along 79° N), comparing Polar and Atlantic surface waters in September 2009 and 2010. CDOM absorption of Polar water in the EGC was significantly higher (more than 3-fold) compared to Atlantic water in the WSC, with values of absorption coefficient, aCDOM(350), m−1 of 0.565±0.100 (in 2009) and 0.458±0.117 (in 2010), and 0.138±0.036 (in 2009) and 0.153±0.039 (in 2010), respectively. An opposite pattern was observed for particle absorption with higher absorption found in the eastern part of the Fram Strait. Average values of particle absorption (aP(440), m−1) were 0.016±0.013 (in 2009) and 0.014±0.011 (in 2010), and 0.047±0.012 (in 2009) and 0.016±0.014 (in 2010), respectively for Polar and Atlantic water. Thus absorption of light in eastern part of the Fram Strait is dominated by particles — predominantly phytoplankton, and the absorption of light in the western part of the strait is dominated by CDOM, with predominantly terrigenous origin. As a result the balance between the importance of CDOM and particulates to the total absorption budget in the upper 0–10m shifts across Fram Strait. Under water spectral irradiance profiles were generated using ECOLIGHT 5.4.1 and the results indicate that the shift in composition between dissolved and particulate material does not influence substantially the penetration of photosynthetic active radiation (PAR, 400–700nm), but does result in notable differences in ultraviolet (UV) light penetration, with higher attenuation in the EGC. Future changes in the Arctic Ocean system will likely affect EGC through diminishing sea-ice cover and potentially increasing CDOM export due to increase in river runoff into the Arctic Ocean. Role of attenuation of light by CDOM in determining underwater light regime will become more important, with a potential for future increase in marine productivity in the area of EGC due to elevated PAR and lowered UV light exposures.

This paper presents the first comprehensive insight into the structure of planktonic communities, from nanoprotists to mesozooplankton in the waters north of Svalbard during the dark Arctic winter. Our investigations were carried out in two contrasting locations comparing a shallow fjord, Rijpfjorden, and a deep ice-covered region, Sofiadjupet, in January 2012. They revealed low chloro- phyll a concentrations (\0.05 mg m -2 ), as a result of the low protist biomass (0.54-2.04 mg C m -2 ). Overall, 27 plastidic protist taxa were observed including 14 auto- trophic taxa and one typical early Arctic spring bloom species (Entomoneis sp.). The presence of these photo- trophic organisms, mostly dinoflagellates, showed that some pelagic autotrophs are able to survive the dark winter period. The high mesozooplankton biomass (6-8 g C m -2 ) indicated a healthy community despite the scarcity of pri- mary producers. Three Calanus species dominated the mesoplanktonic biomass (79 %) in Rijpfjorden, whereas in Sofiadjupet carnivorous Chaetognatha (72 %) were domi- nant. Vertical distribution/profiles of the different trophic categories showed that herbivores were concentrated in the surface water layers (20-0 and 100-10 m) at both sites, whereas predators were occupying the deeper waters (600-100 m) of Sofiadjupet. Our results indicate that high mesozooplankton biomass is concentrated in surface waters. This contradicts the paradigm that mid-January, Arctic zooplankton communities overwinter in deep waters in a dormant state. Moreover, this work fills an evident gap in existing knowledge of Arctic plankton standing stocks and the relationships between its various size fractions during the polar night.

The annual routines and seasonal ecology of herbivorous zooplankton species are relatively well known due to their tight coupling with their pulsed food source, the primary production. For higher trophic levels of plankton, these seasonal interactions are less well understood. Here, we study the mid-winter feeding of chaetognaths in high-Arctic fjord ecosystems. Chaetognaths are planktivorous predators which comprise high biomass in high-latitude seas. We investigated the common species Parasagitta elegans around the Svalbard archipelago (78–81°N) during the winters of 2012 and 2013. Our samples consisted of individuals (body lengths 9–55 mm) from three fjords, which were examined for gut contents (n = 903), stable isotopes, fatty acid composition, and maturity status (n = 352). About a quarter of the individuals contained gut contents, mainly lipid droplets and chitinous debris, whilst only 4 % contained identifiable prey, chiefly the copepods Calanus spp. and Metridia longa. The δ15N content of P. elegans, and its average trophic level of 2.9, confirmed its carnivorous position and its fatty acid profile [in particular its high levels of 20:1(n-9) and 22:1(n-11)] confirmed carnivory on Calanus. Observations of undeveloped gonads in many of the larger P. elegans, and the absence of small individuals

Diel vertical migration (DVM) of zooplankton is a global phenomenon, characteristic of both marine and limnic environments. At high latitudes, patterns of DVM have been documented, but rather little knowledge exists regarding which species perform this ecologically important behaviour. Also, in the Arctic, the vertically migrating components of the zooplankton community are usually regarded as a single sound scattering layer (SSL) performing synchronized patterns of migration directly controlled by ambient light. Here, we present evidence for hitherto unknown complexity of Arctic marine systems, where zooplankton form multiple aggregations through the water column seen via acoustics as distinct SSLs. We show that while the initiation of DVM during the autumnal equinox is light mediated, the vertical positioning of the migrants during day is linked more to the thermal characteristics of water masses than to irradiance. During night, phytoplankton biomass is shown to be the most important factor determining the vertical positioning of all migrating taxa. Further, we develop a novel way of representing acoustic data in the form of a Sound Image (SI) that enables a direct comparison of the relative importance of each potential scatterer based upon the theoretical contribution of their backscatter. Based on our comparison of locations with contrasting hydrography, we conclude that a continued warming of the Arctic is likely to result in more complex ecotones across the Arctic marine system.

The daubed shanny (Leptoclinus maculatus) is considered an ecologically significant species in Svalbard waters. It is an abundant and energy-rich food source for predatory fishes and sea birds, and has an important role in the transfer of energy from Calanus spp. to higher trophic levels. This study presents the first description of caudal length (CL), gutted weight (GW) and age distribution, CL–GW relationships (condition) and growth performance index of L. maculatus from Svalbard. Our findings show that L. maculatus was sexually dimorphic in most aspects of growth. The sex ratio was skewed towards males (65 %), and sexes showed similar CL–GW relationships with positive allometric growth (b > 3). However, males had significantly deeper bodies than females at CL > 120–125 mm. Males had shorter asymptotic CL and higher growth rate than females. Females had lower asymptotic GW than males, although the growth rate for GW was similar for both sexes. Males had significantly higher growth performance than females for both CL and GW with age. Males had a slightly higher obtained growth index (OGI) than females, although both sexes had OGI values ≈1, indicating that they utilize their full growth potential in Svalbard waters.

Approximately 60% of Svalbard's land areas are glaciated at the present time. The Archipelago has more than 1100 glaciers (> 1 km2) and 163 of these are “tidewater glaciers” — that is glaciers that terminate (with their calving front) at the sea. It has been known for a long time that these glacier front areas are important feeding areas for seabirds and marine mammals. Herein, we review current knowledge regarding the importance of these areas for these animals and reflect upon the processes that create these apparent “hotspots”. Kittiwakes Rissa tridactyla, routinely dominate avian assemblages in front of glaciers in Svalbard, but fulmars Fulmarus glacialis, ivory gulls Pagophila eburnea and glaucous gulls Larus hyperboreus also contribute to aggregations, which can sometimes comprise many thousands of individuals. The birds are often found in the so-called “brown zone”, which is an area in front of tidewater glaciers that is ice-free due to currents and muddy due to suspended sediments. Animals at these sites typically have their stomachs full of large zooplankton or fish. These brown zones are also foraging hotspots for Svalbard's ringed seals (Pusa hispida) and white whales (Delphinapterus leucas). Prime breeding habitat for ringed seals in Svalbard occurs deep in the fjords where ice pieces calved from the glacier fronts become frozen into land-fast sea-ice, promoting the accumulation of snow to a depth suitable for ringed seal females to dig out birth lairs above breathing holes in the ice. These pupping areas are important hunting areas for polar bears (Ursus maritimus) in spring, especially female bears with cubs of the year during the period following emergence from the winter/birthing den. Glacier-ice pieces floating in coastal areas are also important for all seal species in the region as dry platforms during moulting and also as general resting platforms for both birds and seals. During the last decade there have been several years with a complete lack of spring sea ice in many of the fjords along the west coast of Spitsbergen. During the spring periods in these years, bearded seals (Erignathus barbatus) have replaced their regular sea-ice platform with glacier ice, using it as a solid substrate for both birthing and nursing as well as general resting. The mechanisms that create foraging hotspots at the fronts of tidewater glaciers are related to the massive subsurface plumes of freshwater discharged from the glacier fronts. As these plumes rise towards the surface they entrain large volumes of ambient water, tens to hundreds of times the original discharge volume. This water is drawn from all depth levels as the plume ascends. This entrainment ensures a continuous resupply of intermediate depth waters from the outer parts of the fjords towards the glacier front and greatly amplifies the general estuarine circulation. The intermediate water masses carry plankton from a broad area, including the outer fjord, into the glacier front area, where they get entrained in the plume rising towards the surface, and often become stunned or die from freshwater osmotic shock. These small animals fall as an easy prey to the surface feeding predators. Large, strong swimming marine zooplankton species can sometimes escape by swimming below the inflow of marine water. But, they then become concentrated in a water layer near the bottom, making them of interest and susceptible to predators. The intermediate water masses also bring nutrients towards the glacier fronts where they are transported up to the surface layer where they can subsequently be utilized for post-bloom primary production. However, this tends to have greatest influence some distance away from the glacier front, when much of the outflow sediment has settled out. Currently, the mass balance for Svalbard glaciers is negative and climate change predictions for the future suggest continued warming, and hence continued glacial retreat. This will result in a reduction in both the number of glaciers calving into the ocean in Svalbard and the total length of calving fronts around the Archipelago. Similar to the retraction of the northern sea-ice edge (which is another diminishing foraging hotspot for these same arctic vertebrates), the climate-warming-induced changes in glaciers will likely lead to substantial distributional shifts and abundance reductions for many arctic species.

The daubed shanny, Leptoclinus maculatus (Fries 1838), is an arctic-boreal fish species and widely distributed in Svalbard waters. The ecological role of L. maculatus is determined by its complex life cycle—adults are bottom-dwelling while the young are pelagic—which indicates its place in the Arctic trophic food webs, both pelagic and benthic. As an intermediate link between lipid-rich copepods on which the young of L. maculatus feed, while juvenile L. maculatus are the prrey of Arctic birds and mammals, the species can be considered as an important reservoir and host for Arctic marine parasites. In the present study, we examined fish for parasites by total necropsy. This paper reports, for the first time, data on the parasite fauna of L. maculatus in the waters around Svalbard. L. maculatus is considered an ecologically significant species in this area, and an important link in the transfer of matter and energy from primary producers to higher-order consumers in the Arctic food chains. Peritrichianciliates Scyphidia sp., adult trematodes Helicometrainsolita Polyansky 1955, encysted metacercariae Neophasis sp., juvenile anisakid nematodes, and dyhyllobothriid larvae were found in L. maculatus. The most frequent findings were Neophasis sp. (64%). The data obtained in this study indicate the involvement of L. maculatus in certain transfers of parasites in Arctic waters, between hosts at the same stage of development and between hosts at different stages of development.

Macrozooplankton (e.g. krill, amphipods and jellyfish) and nekton (e.g. decapod shrimp, squid and fish) are integral parts of pelagic ecosystems, but knowledge of their vertical distributions and migrations during winter at high latitudes is lacking. This study provides the quantification of macrozooplankton and nekton distributions during the polar night in a partially ice-covered high Arctic fjord. In January 2012, mid-water trawls and MIK nets were deployed in Rijpfjorden, Svalbard (80° 18′ N, 22° 15′ E) at three depths (20, 75 and 200 m) day and night. Simultaneously, acoustic volume backscattering strength (a measure of biomass) was recorded using 18-, 38- and 120-kHz echosounders. We observed that the majority of nekton were below the thermocline (>100 m) day and night. A diverse fish community (10 species present) dominated the nekton biomass closely followed by shrimp and squid. Macrozooplankton, mostly large Calanus spp. copepods and gelatinous zooplankton, were found throughout the water column, but the majority were above the thermocline day and night. A general additive model with depth, time and moonlight predicted biomass to increase with depth for both macrozooplankton (over the top 100 m) and nekton, but revealed no patterns in biomass over time. The model also indicated that full moon presence increased depth of macrozooplankton backscatter. Our findings suggest a diverse and to some degree active pelagic community during the polar night, and provide some support for the hypothesis that moonlight induces downward vertical migrations of macrozooplankton.

During a research cruise to the Arctic Ocean in January 2012, we observed high occurrence of carcasses of Calanus spp. We analysed live samples to separate living from dead individuals. In Rijpfjorden, an Arctic fjord in north-eastern Svalbard, 9–14% of the Calanus population were observed to be dead. At Sofiadjupet, an oceanic basin located at 81.4N at the southern edge of the Arctic Ocean, 94% of the Calanus at depth (between 300 and 2000 m) were dead. This is the first estimation of the contribution of carcasses to high Arctic copepod populations. Lipid sacs were preserved in part of the observed carcasses and the lipid sac area was significantly smaller in dead Calanus than in living individuals. We discuss possible causes for the observed mortality, its implication for population dynamics and energy transfer and review previous accounts of non-predatory mortality of marine copepods. In our case, partial consumption by predators and death after reproduction are unlikely causes of mortality, thus other stressors (starvation, environmental conditions, parasitic or viral infection) may be responsible. Our analysis shows that we have a poor understanding of factors other than predation causing mortality in copepod populations.

The daubed shanny, Leptoclinus maculatus, is a common fish species in Arctic and North Atlantic waters and has an important role in high-latitude ecosystems as a link between lower trophic levels and many fish, marine mammal and seabird species. Its biology and ecology have, however, remained largely unstudied. The primary aim of this study was to increase the knowledge about the daubed shanny by analysing total lipids, lipid-classes and the fatty acid composition of liver, muscle and female gonads in adults from the high Arctic archipelago of Svalbard. In female gonads, the triacylglycerols and wax esters in addition to cholesterol esters were dominant among the stored lipids. Triacylglycerols dominated in the liver, whereas structural lipids, such as phospholipids and cholesterols, were the most important lipids in muscles. Phosphatidylcholine and phosphatidylethanolamine were major phospholipids in all organs studied. The fatty acid spectrum of the investigated organs was characterized by a high amount of monounsaturated fatty acids, particularly in the liver. Polyunsaturated fatty acids, particularly 22:6(n-3) and 20:4(n-6), were prevalent in muscle tissues. The lipid and fatty acid spectra in the organs during this period of life are tightly connected with the activation of the liver metabolism and the storage of lipids in the developed female gonads. Lipid accumulation and distribution in gonads are transferred to optimal development of embryos and larvae in Arctic waters.

The timing of reproductive events of Calanus glacialis is closely coupled to the two major marine primary production events in the Arctic: the ice algal and phytoplankton blooms. Reproductive strategies vary between different physical and biological environments of the European and Canadian Arctic. In the Canadian Beaufort Sea and the high Arctic Rijpfjorden on Svalbard, C. glacialis utilized the ice algae bloom to fuel spawning in spring, while growth and development of the new generation was primarily supported by the phytoplankton bloom. In the predominantly ice-free Arctic Kongsfjorden (Svalbard), C. glacialis was mainly a capital breeder spawning early in the season in the absence of food. This enabled the offspring to synchronize their growth and development with the phytoplankton bloom and, thus, reproduce successfully despite the lack of an early ice algal bloom. The variability in life history traits observed in the Canadian and European Arctic is compared with data from other Arctic regions to present a pan-Arctic perspective on life cycle strategies of C. glacialis.

A comparative study of the lipid status (i.e., the total lipid and phospholipid concentrations and the percentage of fatty acids of the total lipids) of adult specimens of daubed shanny (Leptoclinus maculatus) from Svalbard waters (Isfjord) and slender eel blenny (Lumpenus fabricii) from the White Sea (Onega Bay and Tersky shore) was performed to study the metabolism and functions of lipids of these fishes in ontogeny and under various ecological conditions. Slender eel blenny from both areas of the White Sea were distinguished by a high level of sphingomyelin compared with the daubed shanny from Svalbard, and the amount of total phospholipids was higher in slender eel blenny from Onega Bay than in slender eel blenny from the Tersky shore. The extent of saturation and the signature of polyenic fatty acids varied according to the specific species of the Stichaeidae family under study. These results demonstrate the differences in the trophoecological and hydrobiological conditions of habitations of these species and highlighted the importance of considering certain trends in the lipid profiles of these fishes as specific features of the organization of the ecological and biochemical mechanisms of adaptation.

The Greenland shark (Somniosus microcephalus) is the only shark species known to inhabit ice-covered seas in the North Atlantic, but remains a missing component in most studies of Arctic food webs. In the present study, stable isotopes (SIs) of nitrogen (δ15N) and carbon (δ13C) and fatty acids (FAs) were analyzed to identify the role of Greenland sharks (sampled during June 2008-2009) in Kongsfjorden, a productive fjord on the west coast of Svalbard, Norway (~79oN, 12-13oE). The Greenland shark fed at a high trophic position (4. 8) based on δ15N values, and δ13C confirmed that most (70 %) of their carbon was derived from phytoplankton-based food chains, which is consistent with a heavy reliance on pelagic teleosts and seals. Greenland sharks from Kongsfjorden had fatty acid profiles in both muscle and plasma (e. g., low 20:1n-9, high 22:5n-3) that suggested a low portion of Greenland halibut (Reinhardtius hippoglossoides) and high proportion of gadoids and seals in their diet compared to Greenland sharks sampled in Cumberland Sound, Canada, during April 2008, which were previously shown to derive much of their energy from Greenland halibut. The high proportions of seal fatty acids in both slow- (muscle) and fast- (plasma) turnover tissues indicate that trophic interactions between Greenland sharks and seals in Kongsfjorden are a common occurrence. Results from the present study suggest that Greenland sharks likely play a unique and significant role in Arctic marine food webs as a top predator of fishes and marine mammals. © 2013 Springer-Verlag Berlin Heidelberg.