Northeast Water Polynya Research Articles

Particulate matter and phytoplankton and bacterial biomass distributions in the Northeast Water Polynya during summer 1992

The patterns of particulate matter distribution (chlorophyll, phytoplankton pigmentation, biogenic silica, particulate carbon, and nitrogen, bacterial and phytoplankton abundance, and optical particle concentration) in the Northeast Water Polynya off the northern coast of Greenland are described, and their relationships to environmental conditions (hydrography, nutrients, and ice cover) are analyzed. Particulate matter concentrations were substantial in the euphotic zone, with the largest fraction consisting of phytoplankton material. Most of this phytoplanktonic material was diatomaceous during the study period (late summer). Surface chlorophyll concentrations were inversely correlated with nitrate concentrations, which were often undetectable in the surface layer, suggesting that phytoplankton standing stocks were controlled by nitrogen availability. The particulate carbon to particulate nitrogen ratio was unusual, in that elevated (approximately nine by weight) mean values were observed near the surface and reduced values (near 6 by weight) occurred at the base of the euphotic zone. These elevated C/N ratios apparently resulted from adaptation to low nutrient conditions. Other elemental ratios (particulate carbon to chlorophyll, biogenic silica to particulate carbon) appear similar to other Arctic systems. Bacterial numbers were greatest in waters with intermediate ice concentrations but in all cases contributed a small fraction (approximately 3%) of organic carbon in the particulate pool. Though variable in spatial distribution, the polynya was a source of substantial quantities of particles; resolving the fate of this material requires further analysis of these data in conjunction with rate measurements and coupled physical‐biological models.

The Northeast Water Polynya during summer 1992: Distribution and aspects of secondary production of copepods

Zooplankton ecology in the Northeast Water Polynya was investigated from July 15 to August 15, 1992. The initial hypotheses were that the polynya would be a site of enhanced secondary production and that the copepod community would be composed of varying proportions of North Atlantic and Arctic species advected onto the Greenland shelf through the Northern and Southern Troughs. Striking contrasts were observed between the northern and southern regions of the shelf. The southern region was dominated numerically by the North Atlantic species Calanus finmarchicus, while species of Arctic origin (C. glacialis, C. hyperboreus, Metridia longa) dominated in the northern region. The polynya itself contained few of the herbivorous Calanus species but, instead, was dominated by the omnivore M. longa. Secondary production of C. glacialis, represented by egg production rates, was high in all regions (55–88 eggs/female/day). However, because of low abundances of the large bodied Calanus species within the polynya, it is estimated that the herbivorous copepods were not significant consumers of primary production in the polynya. Fundamentally different pathways for the cycling of carbon may exist in the northern and southern regions. Copepod communities may utilize much of the primary production in the south but only a small proportion of the primary production in the polynya, where significant proportions may be unconsumed.

Benthic response to water column productivity patterns: Evidence for benthic‐pelagic coupling in the Northeast Water Polynya

Polynyas, recurring ice‐free areas amid pack or drift ice, are model systems for predicting the potential productivity of pelagic and benthic communities in polar regions. The Northeast Water Polynya on the northeast Greenland continental shelf and surrounding ice‐covered areas were investigated to address the influence of water column processes on the benthos. We measured infaunal density, polychaete biomass, sediment carbon concentration, and benthic pigment concentration from replicate box cores at 16 stations. Benthic pigment concentration is the most important predictor of infaunal density and polychaete biomass, explaining nearly half of the variance in these variables. Benthic pigment concentrations are strongly related to the concentrations of water column pigments, suggesting that the signal of water column productivity is received on the bottom and transmitted to the fauna. The highest densities and biomass are found near the mouth of the Northern Trough and are probably fueled by biogenic material produced by the developing phytoplankton community as it is advected down the trough. Density and biomass are also generally higher under the ice‐free water of the Northern Trough than under the ice‐covered Southern Trough. This pattern may be explained by greater primary productivity in the Northern than Southern Trough and/or by a decoupling of water column and benthic process by Zooplankton grazing in the south. Sediment organic carbon concentration is between 0.5% and 1.5%, indicating that the sediment is probably not an unusually large carbon sink relative to shelf and deep‐sea systems in temperate and polar regions. These results reinforce an emerging pattern of efficient transfer of carbon from water column to benthos in high latitudes. Owing to the abundance of small‐scale and mesoscale areas of enhanced phytoplankton production in the Arctic (e.g., leads, marginal ice zones), benthic biomass in the Arctic Ocean and surrounding seas may be higher than previously anticipated.

The abundance of benthic calcareous foraminifera and other meiofauna at a time series station in the Northeast Water Polynya, Greenland

Abundance and vertical distribution of living calcareous Foraminifera and associated meiofauna have been estimated during the ice‐free period in 1992 and 1993 at a time series station in the Northeast Water Polynya off eastern Greenland. Calcareous forams (>150 μm) represented on average 28–39% of the meiofaunal size class. The mean abundance for both years was 574 individuals/100 cm2, and the variability of the estimates (Standard deviation = ±140) was relatively modest for benthic samples (Standard error=8.7% of the mean, number of samples=8). The abundance in 1992 was lower than in 1993 (probability <0.05), reflecting a smaller polynya, with less surface water productivity. While 41% of the variation in abundance in 1993 could be explained as a function of time (the estimated mean doubled between May 30 (387 ind/100 cm2) and July 24 (734 ind/100 cm2)), supporting earlier observations elsewhere that Foraminifera respond rapidly to seasonal or pulsed food inputs, the relationship was not statistically significant. The number of species present was low, a characteristic observed in other foram biofacies associated with open water shelf regions of the Arctic. This assemblage was dominated by a few calcareous forms: Elphidium excavatum, Melonis barleeanum, Nonionella labradorica, and Bucella frigida. Green and brown material, which we suspect was freshly settled phytodetritus, was found in numerous individuals of the dominant calcareous species located as deep as 6 cm within the sediment. The dominant species, including those containing “pigments,” were encountered at specific, fairly narrow depth ranges within the sediment, with maximum abundances being common below, rather than at the sediment surface. Other meiofauna (nematodes, agglutinated forams, and ostracods) occurred to depths as great as 10 cm in all cores, but their greatest densities were generally confined to surface sediments.

The 1992 summer circulation in the Northeast Water Polynya from acoustic Doppler current profiler measurements

A July–August 1992 snapshot of the circulation in the Northeast Water Polynya located off the coast of Greenland is presented using data collected with an acoustic Doppler current profiler (ADCP) during the cruise of the USCGC Polar Sea. The data reveal anticyclonic circulation with velocity and transport cores aligned with the local topographic trough. Transport through the trough is between 0.5 and 0.9 Sv. The total ADCP measured velocities are generally less than 10 cm s−1, but some regions have velocities larger than 20 cm s−1. The ratio of the average velocity of the upper 100 m to the average velocity below 100 m shows surface layer flows faster by a factor of between 1.2 and 2. This ratio in the ice‐free northwest portion of the polynya is smaller (≈1.5) than found over the adjacent continental shelf (≈2.0), indicating smaller vertical shear. The data show northward flow along the coast, supporting the idea that ice carried by this flow is blocked from entering the polynya by a persistent ice wedge to the south that extends from the coast, east over the topographic trough, to a shallow central bank. By blocking ice advecting from the south, the ice wedge enhances the polynya, supporting the idea that the Northeast Water Polynya is a latent heat polynya.

On the generation of the Northeast Water Polynya

In spring and summer of 1993 a multidisciplinary survey of the Northeast Water (NEW) Polynya, located on the continental shelf northeast of Greenland, was undertaken by R/V Polarstern. Hydrographic and remotely sensed data from this expedition are analyzed with respect to the generation and the seasonal development of the NEW. Its formation is concluded to result from the combined effect of a fast ice barrier, extending perpendicular from the coast and bridging a trough system, and a northward flowing coastal current. The fast ice barrier protects the region downstream of it from ice import while current driven ice export continues. The temporal development and spatial distribution of hydrographie parameters in the NEW is primarily controlled by its generation mechanism. Continental and sea ice melt induce vertical stability in certain parts of the polynya, giving rise to enhanced primary production there.

Thorium‐234/uranium‐238 disequilibrium as an indicator of scavenging rates and participate organic carbon fluxes in the Northeast Water Polynya, Greenland

Analyses of particulate and dissolved distributions of the naturally occurring radionuclide 234Th (half‐life=24.1 days) in the water column of the Northeast Water Polynya (Greenland continental shelf) show deficiencies relative to equilibrium with 238U that are related to uptake onto sinking particles. The deficiencies are generally enhanced in the upper 50 m of the water column (Polar Water), a zone of high suspended particle, particulate organic carbon, and pigment concentrations. In July–August 1992, residence times of dissolved Th relative to uptake onto particles ranged from 52 to 293 days and those of particulate Th relative to sinking ranged from 6 to 52 days in the upper 50 m. In contrast, removal was enhanced in July–August 1993, with dissolved and particulate 234Th residence times ranging from 45 to 167 days and 4 to 57 days, respectively. The assumption of steady state used in these calculations is not strictly valid, in that both years showed progressive increases in 234Th removal at stations reoccupied several weeks apart. Spatial variation in 234Th removal from the water column also is evident and may be due, in part, to progressive 234Th removal associated with the inferred anticyclonic circulation within the polynya. Inventories of particulate 234Th in the upper 50 m correlate well with inventories of suspended particulate matter and particulate organic carbon (POC). Using the ratio of POC/234Th on suspended particles and the 234Th fluxes obtained from disequilibrium with respect to 238U to calculate POC fluxes gives values of 12 to 45 (mean = 25±14) mmol C m−2 d−1 in 1992 and 17 to 45 (mean = 35±10) mmol m−2 d−1 in 1993. A direct comparison of the Th‐derived POC fluxes from the 1992 data is possible with those obtained independently based on depletions of dissolved nutrients (29.2±23.5 mmol m−2 d−1 (Wallace et al., this issue)) and dissolved inorganic carbon (14±7.4 mmol m−2 d−1 (Yager et al., this issue)). The good agreement reflects the fact that during the summer, particle cycling and flux in the surface water of the polynya are apparently dominated by biogenic particles. Removal of 234Th from the water column is balanced, within the uncertainties, by inventories of excess 234Th in bottom sediments, with both water column deficiencies and sediment inventories greater in 1993 than 1992. This indicates that on the timescale of several half‐lives of 234Th (∼100 days) the polynya is in balance with respect to 234Th (and probably the particles with which it is associated).

Nutrients, oxygen, and inferred new production in the Northeast Water Polynya, 1992

Nutrient and oxygen distributions were measured during a hydrographic survey of the Northeast Water Polynya off the northeast coast of Greenland (77–81°N, 6–17°W) during July–August 1992 and were interpreted in the context of satellite imagery of the region. Satellite imagery revealed a convoluted plume of cold water flowing along isobaths from underneath fast ice in the southwestern portion of the polynya toward the northeast. This plume carried relatively high nutrient and low oxygen inventories. Nitrate to phosphate ratios were low in the polar water, consistent with an ultimate source of this water mass in the Pacific sector of the Arctic Ocean. It is hypothesized that the low N:P Arctic outflow might be the cause of nitrate limitation along the east coast of America as far as Cape Hatteras. Gradients of both nutrients and oxygen inventories in the euphotic zone were observed along and across the axis of mean flow within the polynya and are shown to be due to net production of organic matter. On the basis of these spatial gradients of nitrate and oxygen, an assumed along‐axis current velocity of 10 cm s−1, and the observed relationships of biologically removed inorganic carbon with nitrate and oxygen, the net organic matter production was estimated to be 40–60 mmol(C) m−2 d−1. This represents the organic carbon available for export from the polynya euphotic zone. Nutrient‐deficient and oxygen‐rich waters were observed merging with the southward flowing East Greenland Current, suggestive of possible export, however, the ultimate fate of organic carbon produced within the polynya requires further study.

On the hydrography of the Northeast Water Polynya

The water masses and circulation in the area of the Northeast Water Polynya, located on the East Greenland Shelf north of 79°N, are described on the basis of an R/V Polarstern cruise during spring and summer 1993. The baroclinic flow shows northward components close to the East Greenland coast and eastward components at the northern limit of the polynya. An anticyclonic half circle is formed by this and the southward flowing East Greenland Current. In the south the circle is not closed. The upper water column, occupied by Polar Water, is affected by this circulation pattern, while deeper waters in the trough system of the area seem to spread independently. Different types of deep waters are found in different troughs, all being of Atlantic origin, though they seem not to be directly connected to Return Atlantic Water. It is shown that what is called Polar Water must be formed, at least partly, on the Greenland Shelf and that deepwater formation does not occur in the investigated area.

Colonies of Northern Fulmars and Black-legged Kittiwakes Associated with the Northeast Water Polynya, Northeast Greenland

The first census of cliff-nesting seabirds dependent on the resources of the Northeast Water polynya was carried out in 1993. We made direct counts in six known colonies of the northern fulmar ( Fulmarus glacialis ) and used a combination of direct and photo counts in one colony of black-legged kittiwakes ( Rissa tridactyla ). Glaucous gulls ( Larus hyperboreus ) occurring at these colonies were also surveyed. A total of 1887 apparently occupied fulmar sites were counted, and a subjective attempt to correct for missed sites gave a total of 2550 apparently occupied sites, in which an estimated 1475 pairs laid eggs. The cliffs at Mallemukfjeld and a neighbouring unnamed cliff held 80% of the fulmar sites. Kittiwakes nested only at Mallemukfjeld, which held 873 apparently occupied sites in which an estimated 733 pairs initiated laying. The minimum glaucous gull population present in the six fulmar colonies was estimated at 22 occupied sites. The fulmar and kittiwake colonies at the Northeast Water polynya were larger than previously assumed. We present estimates based on daily variation in colony attendance of the effort required to detect annual differences in population size. There is now a basis for evaluating any future population changes in some of the most extreme high-arctic seabird populations. Key words: northern fulmar, Fulmarus glacialis , black-legged kittiwake, Rissa tridactyla , seabirds, population monitoring, polynya, high Arctic, Greenland

Sources of primary production, benthic-pelagic coupling, and trophic relationships within the Northeast Water Polynya:insights from delta13C and delta15N analysis

Sources of primary production, benthic-pelagic coupling, and trophic relationships within the Northeast Water Polynya:insights from delta13C and delta15N analysis

The North East Water polynya (Greenland Sea)

The nutrient and phytoplankton distributions in the North East Water polynya (NEW) were determined in June 1991. At Norske Oeer Ice Barrier (the polynya's southern boundary), water was upwelled, but vertical instability precluded the development of phytoplankton blooms. Along the length of the northward coastal current, part of the anticyclonic circulation in this area, the vertical stability increased to the north by the input of melt water and solar heating. This caused a gradual increase in phytoplankton biomass and a decrease in nutrient concentrations until, in the northernmost area, nitrate was depleted at the surface, and sub-surface maxima of chlorophyll a were observed. The band of high chlorophyll a concentrations extending from this area to the south along the eastern margin of the polynya was interpreted as the presence of phytoplankton advected by the local circulation. The phytoplankton communities, consisting mainly of flagellates and diatoms, were typical for the beginning of phytoplankton development in ice-covered areas. They seemed to be partially released from melting ice. Three communities were distinguished, which represented, firstly, the upwelled water and its northern extension, secondly, an area of high phytoplankton biomass in the northwestern part of the polynya, and thirdly, the pack-ice region. The major taxa co-occurred at all stations, with only their relative importance changed. The nutrient concentrations in the NEW were different from those in the adjacent areas. The low nitrate values of about 4 mu M in the upper 70 m, found to be representative for the beginning of the growth season, imposed limitations on the overall phytoplankton production. Therefore, fertilization mechanisms such as upwelling along the Norske Oeer Ice Barrier are important for local nutrient replenishment during the period of active phytoplankton growth. Eventually, silicate and phosphate supplied in higher concentrations by jets of the Arctic outflow may also support phytoplankton production, although these nutrients were not limiting during this study. The high nutrient jets were detected in the upper 100 m of the water column at the eastern boundary of the polynya.

The Northeast Water polynya, Greenland Sea

During a pilot study in June 1991 meso-and macrozooplankton investigations were carried out in the region of the Northeast Water (NEW), a polynya located off Northeast Greenland at about 80°N. The mesozooplankton collected by bongo net was dominated by the large herbivorous copepods Calanus glacialis, C. hyperboreus and C. finmarchicus. At most stations the Calanus populations consisted of overwintering stages, except for an ice-free site in the northwestern corner of the study area, where young copepodids of C. hyperboreus and C. glacialis occurred. Young C. finmarchicus were only found at stations influenced by Atlantic water masses, whereas C. glacialis was the prevailing species on the East Greenland shelf. Egg production of this species was variable, but spawning activity appeared to be related to ambient chlorophyll a concentrations. Carbon requirements of herbivorous Zooplankton were estimated from egg production rates of C. glacialis. Due to low mesoplankton biomass, a mean of only 10% (ranging from <1% to 53%) of the phytoplankton carbon were grazed. Macrozooplankton was collected at three stations by a Rectangular Midwater Trawl (RMT 1+8). Major components were chaetognaths, hyperiid amphipods and large copepods. Macroplankton biomass was extremely low (1–3 mg AFDW m−3), about one order of magnitude less than that of the mesoplankton. Based on these limited data we hypothesize that macroplankton plays only a minor role as food for higher trophic levels and as predators controlling mesoplankton in the NEW polynya. These findings seem todisprove the concept of a rich pelagic community in the polynya amongst “a desert of ice”. They do, however, fit well with the notion of strong pelago-benthic coupling of primary production supporting a rich benthos within the polynya area.

The North East Water polynya (Greenland Sea)

Physical observations of the North East Water (NEW) polynya, located near the north-eastern corner of Greenland, are presented. Data were collected in June 1991 by RV Polarstern. An idea is put forward to explain how the NEW is generated. A northward coastal current interacts with a persistent shelf ice barrier under which water can flow but that retains ice floes and therefore protects the NEW area from ice advection. Since in summer, the combination of currents, barrier and air-sea heat balance gives rise to a polynya. The distribution of upper water column vertical stability in the NEW is also influenced by its generation process. Surface melt water is retained by the shelf ice barrier, causing neutral vertical stability in its lee. Sea ice melting and land runoff then act as two distinct sources of vertical stability enabling the development of plankton blooms, especially in the northern part of the NEW.

Extracellular enzyme activity in the Arctic Northeast Water polynya

We studied extracellular enzyme activity (EEA) in samples of the water column and sediments of the Northeast Water polynya (77 to 81 N, 6 to 17' W) during July-August 1992 in order to determine controls on bacterial hydrolytic activity and possible roles of EEA in the fates of particulate organic matter (POM) on an arctic continental shelf. Samples were taken by Niskin bottle, floating sediment trap and box corer from the USCGC 'Polar Sea' at stations throughout the polynya and icecovered surroundings. Fluorogenic substrate analogs were used to estimate potential maximal rates of peptidase, chitobiase and lipase EEA in time course experiments over incubation periods of 1.3 to 14 h at -1, 2 , 5 , 10, and 16OC. Increasing incubation temperature typically increased EEA, but psychrophilic rates (little to no increase upon warming) were detected in several samples, usually for peptidase activity. Rates adjusted to in situ temperature (EEAIS) and normalized to bacterial abundance were compared to similarly determined rates reported previously for other (including temperate) environments and to each other. In general, EEAls rates in polynya waters were lower than in other pelagic environments, while rates in polynya sediments were comparable to those in other sediments. The whole polynya data set, which allows the first comparison between pelagic and benthic rates within a given environment, revealed that EEA, rates (usually peptidase activity), whether normalized to bacterial abundance or to sample dry weight, were generally higher in pelagic samples, particularly in samples from sediment traps deployed in the subzero Polar Surface Water mass. Although relationships between EEAls and temperature or several other environmental parameters (measured by other researchers on the Polar Sea) could not be identified, chitobiase and lipase EEA, did correlate positively, and peptidase activity negatively, with indicators of POM supply to the benthos (pigment concentrations). Observed differences in the effects of incubation temperature and environmental POM supply between enzymes may be explained by differences in location and regulation of peptidase and other EEA.

Northeast water polynya: Polar sea cruise results

Motivated in part by model predictions that Arctic regions will be subject to disproportionate warming as the Earth's radiative balance shifts, the National Science Foundation recently established a new Global Change Research Program known as Arctic System Science (ARCSS). While ARCSS recognizes the Arctic system as a central element of global climate, it also acknowledges that there is insufficient data on physical, chemical, and biological processes in the Arctic to understand its role in climate change.In the same time frame, the Arctic Ocean Science Board created the International Arctic Polynya Program to focus on critical roles that polynyas may play in the dynamics of the Arctic environment. Although they comprise only a small part of the Arctic region, these open bodies of water in sea ice can account for a significant fraction of the midwinter energy exchange between atmosphere and ocean. Polynyas are also believed to be sites of dense‐water formation and elevated biological activity. The concept of physical, chemical, and biological processes occurring at enhanced rates in an Arctic region small enough to be studied directly has focused attention on polynyas as potentially excellent models of the consequences of global change at high latitudes.

Plankton distribution and the impact of copepod grazing on primary production in Fram Strait, Greenland Sea

Two hydrobiological transects across the East Greenland Shelf and the open waters of Fram Strait in summer were chosen to illustrate the distribution and production of phyto- and zooplankton in relation to water masses and ice cover. The parameters used were temperature and salinity, inorganic nutrients, chlorophyll a, primary production, phytoplankton species composition, abundance of the dominant herbivorous copepods Calanus finmarchicus, C. glacialis, C. hyperboreus, Metridia longa and egg production of C. finmarchicus and C. glacialis. Grazing impact of copepodites and adults of these four species was modelled for each station by using egg production rates as an index of growth. Seasonal development of plankton communities was closely associated with the extent of the ice cover, hydrographic conditions and the water masses typical of the different hydrographic domains. Four regions were identified from their biological activities and physical environment: The Northeast Water polynya on the East Greenland Shelf, with a springbloom of diatoms and active reproduction of herbivorous copepods. The pack ice region, dominated by small flagellates and negligible grazing activities. The marginal ice zone, with high variability and strong gradients of autotroph production related to eddies and ice tongues, an active microbial loop and low egg production. The open water, with high station-to-station variability of most of the parameters, probably related to hydrographic mesoscale activities. Here, Phaeocystis pouchetii was a prominent species in the phytoplankton communities. Its presence may at least partly be responsible for the generally low egg production in the open waters. Grazing impact on primary production was always small, due to low zooplankton biomass in the polynya and due to low ingestion in the remaining regions.

Wax ester composition of the dominant calanoid copepods of the Greenland Sea/Fram Strait region

The composition of the intact wax esters of Calanus hyperboreus, C. finmarchicus, and C. glacialis from the Fram Strait area of the Greenland Sea was studied. In addition the fatty acid and alcohol composition of the wax esters was analysed. All copepods were rich in wax esters, especially C. hyperboreus in which long-chain wax esters were generally more abundant than in the other species. The wax ester composition was species dependent but strongly overlapped by spatial variabilities. Because phytoplankton fatty acids were partially incorporated directly into wax esters, the composition of the wax esters was widely influenced by the phytoplankton community which itself varied considerably in the Fram Strait region. Thus, the wax esters of the polar species, collected in the North East Water Polynya near Greenland, were dominated by diunsaturated compounds in the range from C32 to C44. The shorter chain components resulted from a combination of palmitoleic acid which is typical of diatom lipids with long-chain alcohols. In the marginal ice zone, higher levels of polyunsaturated wax esters were detected due to the presence of the 18:4 fatty acid, typical of a summer phytoplankton population.

Spatial variability in lipid composition of calanoid copepods from Fram Strait, the Arctic

The calanoid copepods Calanus hyperboreus and C. finmarchicus were investigated in view of their lipid and wax ester content and their fatty acid and alcohol composition. Analyses were performed in females and copepodid stages V and IV from the Fram Strait region between Greenland and Spitsbergen in 1984. This region offers different food conditions like diatom blooms in the North East Water Polynya, food shortage in areas with very close ice cover, high phytoplankton biomass in the marginal ice zone and lower biomass in the open Atlantic water. Lipids contained generally more than 70% wax esters. Highest levels were found in C. hyperboreus with more than 90%. This percentage was not very variable, in spite of large differences in dry weight and lipid content. Copepods with particularly high weight and lipid content were found in the North East Water Polynya. The lightest individuals were found under the pack ice. Lipid proportions per unit dry weight were higher in C. hyperboreus than in C. finmarchicus, whose lowest values were found in the open Atlantic water. Spatial variability in fatty acid composition was much higher than in alcohol composition. The principle alcohols, 20:1 and 22:1, generally accounting for more than 80% of total alcohols. In the North East Water Polynya, the predominant monounsaturated fatty acid was 16:1, while under the ice 20:1 and 22:1 dominated. In the marginal ice zone and in the open water, the 18:4 acid reached percentages up to 30% of total fatty acids. These changes were related to the different food conditions. C. hyperboreus appears to be best adapted to the cold water and unfavourable conditions of polar regions because of its high lipid and wax ester store with long-chain wax esters of high calorific value.