Summer bacterio- and zooplankton in coastal waters of Svalbard

The distribution of bacterio- and zooplankton was studied in West Spitsbergen (Svalbard) coastal waters in August 2009. The bacterial abundance and biomass varied from 110 to 3360 × 10³ cells/ml and from 0.66 to 44.93 mg C/m³, respectively. These values were the highest in the surface water layers and decreased with depth. The greatest abundance of bacteria (5099 individuals/m3) was found in the freshened and warm water layer in Isfjorden. The highest biomass of zooplankton (182.41 mg C/m³) was registered in the zone of interaction of coastal and transformed Atlantic waters in the archipelago inner shelf. The spatial variations of abundance and biomass of the planktonic communities were related to the thermohaline characteristics of the water masses and, probably, to microalgal blooms.     

Megabenthic commmunities in the waters around Svalbard

 Composition and distribution of megabenthic communities around Svalbard were investigated in June/July 1991 with 20 Agassiz trawl and 5 bottom trawl hauls in depths between 100 and 2100 m. About 370 species, ranging from sponges to fish, were identified in the catches. Species numbers per station ranged from 21 to 86. Brittle stars, such as Ophiacantha bidentata, Ophiura sarsi and Ophiocten sericeum, were most important in terms of constancy and relative abundance in the catches. Other prominent faunal elements were eunephthyid alcyonarians, bivalves, shrimps, sea stars and fish (Gadidae, Zoarcidae, Cottidae). Multivariate analyses of the species and environmental data sets showed that the spatial distribution of the megabenthos was characterized by a pronounced depth zonation: abyssal, bathyal, off-shore shelf and fjordic communities were discriminated. However, a gradient in sediment properties, especially the organic carbon content, seemed to superimpose on the bathymetric pattern. Both main factors are interpreted as proxies of the average food availability, which is, hence, suggested to have the strongest influence in structuring megabenthic communities off Svalbard. Received: 28 April 1995/Accepted: 18 November 1995     

At-sea distribution of seabirds and marine mammals around Svalbard,summer 1991

At-sea distribution of seabirds and marine mammals was quantitatively determined during the Arctic EPOS cruise of RV Polarstern, from 21 June till 28 July 1991, during 377 half-an-hour counts. Data were expressed as numbers per count and as density, and daily food intake was calculated using allometric equations from literature. Mean densities for the whole expedition were 29 seabirds per km² (mainly little auk,Alle alle: 8.7, kittiwake,Rissa tridactyla: 8.2, Brünnich’s guillemot,Uria lomvia: 6.5 and fulmar,Fulmarus glacialis: 3.4), 0.06 pinnipeds, 0.01 cetaceans and 0.002 polar bears. Total food intake by seabirds and marine mammals was 3.9 kg fresh weight/km² per day, with extreme values of 6.6 in the northern west-to-east transect and 2.5 in the Storfjorden. The major ecological influence were fish eaters (1.7), and more especially Brünnich’s guillemot (1.2). Geographic differences were also detected: food intake by Brünnich’s guillemot represented 62% of total intake in Storfjorden, and by the kittiwake, 45% in the first eastern transect. The first and last transects in the western Barents Sea are described and discussed in more detail. Within different sectors, high concentrations of seabirds were noted, corresponding to hydrological features such as fronts between Atlantic and polar waters, as well as ice edges. Values of seabirds’ density and food intake are higher than in the Greenland Sea, even than at the biologically very active ice edge there. Figures for pinnipeds and cetaceans are similar; numbers of polar bears were higher around Spitsbergen. The data presented were collected during the European “Polarstern” Study (Arctic EPOS) sponsored by the European Science Foundation     

Associations among Antarctic seabirds in mixed-species feeding flocks

We studied ten mixed-species feeding flocks of seabirds and seals off South Georgia (55̀S, 35̀W) to assess the factors that influenced the species composition of the flocks. The ten flocks were distributed between two oceanographic regions; four flocks were observed off the northwestern end of South Georgia, and six off the island's southeastern end. The flocks differed dramatically in size and species composition. The northwestern flocks were ten to 20 times larger and contained more seals and penguins. We tested whether these differences were a consequence of location, because the two regions were populated by different assemblages of species, and determined that this was not the case. Differences in flock size and species composition reflected differences in the depth distribution of the birds' and seals' prey. The northwestern flocks were associated with deep swarms of Antarctic krill Euphausia superba with a significant quantity of krill also present at the surface. We also tested for differential flock participation by the species found in the surrounding waters and classified species by their proclivity to participate in the flocks. Our results indicate that Black-browed Albatross Diomedea melanophris have a strong tendency to join, and diving-petrels Pelecanoides spp. to avoid, mixed-species feeding flocks. We postulate that Black-browed Albatrosses serve as visual cues to the presence of food for one another and for other species, and that diving-petrels avoid mixed-species flocks in part because of the risk of predation.     

Sympagic macro-fauna from multiyear sea-ice near Svalbard

Summary The object of the present investigation was to map the distribution and abundance of sympagic fauna (= ice fauna) (>350 m) within the perennial sea ice zone near Svalbard and to study relations between the sympagic fauna and the age and history of its ice substrate. The sampling took place in July/August 1986 and September 1988 using SCUBA-operated sampling gear (suction samplers, plankton nets with especially designed frames for sampling at the sea-ice/seawater interface, and underwater cameras). The amphipods Apherusa glacialis, Onisimus sp., and Gammarus wilkitzkii were the most conspicuous sympagic species both years. Scattered individuals of the amphipods Gammaracanthus loricatus, Weyprechtia penguis and the polychaete Harmathoinae indet. were also recorded. A. glacialis was the most numerous and contributed near 65% of the collected specimens in both years, with a maximum density exceeding 2000 individuals/m². However, G. wilkitzkii was on average larger, and contributed most to the biomass (1986: 80%; 1988: 77%). The average biomass of sympagic fauna in 1986 and 1988 was estimated to be 4.7 g/m² and 8.3 g/m² respectively. Biomass values reported here are ten to hundred times higher than what is found within the seasonal sea ice zone. Autochthonous sympagic species, like A. glacialis, Onisimus sp. and G. wilkitzkii, have a permanent association with ice. The seasonal sea ice zone will thus have to be recolonized every year resulting in lower densities compared to multiyear ice. It is suggested that the speed of the ice leaving the Polar Basin through the Fram Strait is too high for the sympagic fauna to remain its position in the sea ice zone. The result is an annual loss in the order of 7^*10⁵ tons of sympagic fauna from the perennial sea ice zone.     

Mesozooplankton distribution in northern Svalbard waters in relation to hydrography

We investigated the distribution of mesozooplankton in waters north of Svalbard (north of 78°50′N) at 38 stations in August and September of 2002, 2003 and 2004. The zooplankton community was numerically dominated by copepods (58–98% of the total abundance). Zooplankton abundance ranged from 115 individuals m⁻³ at the northern most location to 12,296 individuals m⁻³ on the shelf. Cluster analysis revealed four different groups with distinct geographic integrity that were identified by variation in species densities rather than by variation in taxonomic composition. Water temperature and salinity differed significantly between the different cluster groups indicating that part of the observed variations in species distribution relate to differences in hydrography. Numerous significant regressions between zooplankton abundance at species level and hydrographical parameters suggest that variability in water masses has measurable effects on zooplankton distribution and species composition in the study area.     

Which components of diet quality affect retention time of digesta in seabirds?

1. The nature of the diet can affect the gut retention time of food consumed by an animal, and a theoretical framework has been developed to explain this in terms of optimal digestion rates. However, diets may differ in a number of different attributes, all of which may separately affect the optimal length of time that they are retained in the gut.
2. Here an attempt is made to elucidate which of these features are important in determining gut retention time of different fish species when fed to nine north Atlantic seabird species, and discuss the different potential optimization criteria for retention time in seabirds.
3. Retention times of Lesser Sandeel ( Ammodytes marinus Raitt.) were shortest, and this species was also rapidly broken down in vitro . Sprat ( Sprattus sprattus (L.)) took longer to be broken down in vitro than Whiting ( Merlangius merlangus (L.)), and also had a high energy and lipid content, which might be expected to result in slow digestion; yet retention times of the two species were similar.
4. Meal size also had an important effect on gut retention times, large meals being retained for longer in the gut than small meals, apparently because of an upper limit on the peak excretion rate.
5. Diet and meal-size related characteristics are important factors influencing prey profitability, prey selection and foraging patterns in seabirds.     

Importance of the large copepod Paraeuchaeta antarctica (Giesbrecht, 1902) in coastal waters and the diet of seabirds at Kerguelen, Southern Ocean

The importance of the euchaetid copepod Paraeuchaeta antarcticain the subantarctic pelagic ecosystem was quantified in thecoastal waters of the Golfe du Morbihan at Kerguelen Islandsby comparing food samples from two diving seabirds with concurrentnet samples taken within the predator foraging area. Paraeuchaetaantarctica occurred in very high densities (up to 30 individualsm^-3 and 96 mg dry weight m^-3) in the water column, being moreabundant in the deepest part of the gulf than in shallow watersor at the more offshore shelf stations. The common diving petrelfeeds almost exclusively on crustaceans, its diet being dominatedby the amphipod Themisto gaudichaudii (52% by number and 84%by reconstituted mass) and P. antarctica (33% and 16%, respectively).Rockhopper penguins preyed upon crustaceans and fish, with fourtaxa being important, namely T. gaudichaudii (37% and 23%, respectively),Euphausia vallentini (24% and 41%), postlarval fish (10% and24%), and P. antarctica (13% and 3%). Paraeuchaeta antarcticadominated numerically in 21% of the diving-petrel food samplesand in 12% of penguin samples. The two bird species segregatedby preying upon different developmental stages of P. antarctica,diving petrels fed equally on CV of both sexes and CVI, whilepenguins fed on CVI only. Comparison of P. antarctica foundin net and food samples indicated no prey selection by commondiving petrels that caught the different copepod stages in proportionto their availability in the water column. On the other hand,the diving performance of penguins, which is better than thatof the petrels (mean maximum dive depths 69 m for penguins versus32 m in petrels), allows them to catch CVI in deeper waters,probably near the bottom. Our study shows that P. antarcticais a major component of the coastal macrozooplankton communityand a significant prey for two species of diving seabirds inhabitingKerguelen. This is also the first record of a copepod speciesas a prey for penguin, and the first to highlight P. antarcticain the food of austral seabirds.     

Lipid indicators of the diet of the sympagic amphipod Gammarus wilkitzkii in the Marginal Ice Zone and in open waters of Svalbard (Arctic)

Triacylglycerols were the major lipid and wax esters a minor lipid in the Arctic autochthonous, sympagic amphipod, Gammarus wilkitzkii, from less than 1 year old to 3 years old in the Marginal Ice Zone around Svalbard. The fatty acids of the triacylglycerols, especially in young G. wilkitzkii, were mainly characteristic of diatoms and, to a lesser extent, flagellates. Small amounts of 20:1n-9 and 22:1n-11 fatty acids characteristic of calanoid copepods were also present in the triacylglycerols in young G. wilkitzkii from the Marginal Ice Zone and the amounts of both of these fatty acids increased in the triacylglycerols as the animals matured. G. wilkitzkii in open waters in Kongsfjord had minor amounts of triacylglycerols rich in 20:1n-9 and 22:1n-11 and major amounts of wax esters characteristic of calanoid copepods. We conclude that young G. wilkitzkii in the Marginal Ice Zone feed predominantly on ice algae and that they consume increasing amounts of calanoid copepods as they mature, albeit with ice algae remaining a prominent component of their diet. In open waters, young G. wilkitzkii consume mainly calanoid copepods.     

Periodic weighing and the assessment of meal mass and feeding frequency in seabirds

Although periodic weighing of chicks is used widely as a means to assess meal mass and feeding frequency in seabirds, there have been few critical assessments of its effectiveness. Using established methods, we were able to predict whether feeding had occurred with an accuracy of over 96% at nests where adult attendance was being monitored independently. This was despite the occasional provision of small meals which did not result in positive mass increments of chicks between weighings. However, information from repeat weighing could not be used to distinguish food delivery by both rather than a single parent within the weighing interval according to the relative sizes of mass increments. This may be because chicks are unable to cope with large meals from both adults because of gut capacity constraints. In addition, adults occasionally return from foraging trips with no food for the chick. These results have important implications for studies in which adult foraging trip durations are estimated solely using periodic weighing data, particularly in species with relatively short feeding intervals.     

Summer feeding habits of the Pacific pomfret Brama japonica in the transitional and subarctic waters of the central North Pacific

Feeding habits of the Pacific pomfret Brama japonica , ranging from 30 to 40 cm in standard length, were quantitatively evaluated using the index of relative importance and were compared between the transitional domain and subarctic region in the central North Pacific. In the transitional domain (between the subarctic boundary and the subarctic front), this species fed mainly on subarctic and transitional‐water gonatid squids such as Berryteuthis anonychus , Gonatus middendorffi and Gonatopsis borealis , the transitional‐water squid Onychoteuthis borealijaponica , and a subtropical and transitional‐water amphipod, Phronima sedentaria . These prey items accounted for 52·8% by wet mass of total stomach contents. In the subarctic region (north of the subarctic front), Pacific pomfrets preyed primarily on subarctic and transitional‐water squids, such as B. anonychus and G. middendorffi , and secondarily on subarctic amphipods such as Hyperia medusarum and Hyperia glaba . These four prey items comprised 71·6% by mass of total stomach contents. Major transitional domain prey items, such as G. borealis, O. borealijaponica and P. sedentaria , were almost non‐existent in stomachs of fish from the subarctic region. The mean wet stomach content mass expressed as a percentage of body mass was significantly higher in the subarctic region (2·35%) than in the transitional domain (0·75%), suggesting that, for this fish, prey items are more readily available in the subarctic region during summer and their northward migration is a feeding migration. Feeding strategy of the Pacific pomfret was discussed in relation to their seasonal south‐north migration.     

Food, feeding ecology and ecological segregation of seabirds at South Georgia

At the sub-Antarctic island of South Georgia 25 of the 29 breeding species are seabirds. Fifteen of these have recently been studied in some detail. By examining the timing of their breeding seasons and their diet and feeding ecology (especially feeding techniques and potential foraging ranges), the nature of their ecological isolating mechanisms, and in particular the way in which they partition the resources of the marine environment, are reviewed.
Although breeding season adaptations occur (winter breeding in Wandering Albatross and King Penguin; out of phase breeding in two species-pairs of small petrels) these are less important than dillerences in food and feeding ecology. There is a fundamental distinction between the niche of pursuit-diving species (mainly penguins) and the remainder which are basically surface-feeders. The two abundant krill-eating penguins show clear differences in feeding zones. Three albatrosses and a petrel feed mainly on squid and there are differences in both the species and size of the prey of each. The remaining seabirds chiefly take krill (although the giant petrels are extensive scavengers and some smaller petrels specialize on copepods) and utilize different feeding methods and areas to do so.
Various adaptations related to inshore and offshore feeding zones are discussed. Although most species possess a combination of ecological isolating mechanisms additional evidence for the particular importance of dietary differences is presented.     

Observations of blue whales feeding in Antarctic waters

There are no published accounts of blue whales (Balaenoptera musculus) feeding in Antarctic waters. This note describes the behaviour of two groups of blue whales feeding in Antarctic pelagic waters. Whales were observed during the 18th IWC/IDCR southern hemisphere minke whale assessment cruise. Feeding behaviour in both cases resembled those described previously for both northern hemisphere blue whales and fin whales (B. physalus). These observations suggest that a programme of comparative behavioural observations could be developed to test the “feeding competition” hypothesis, which suggests that recovery of populations of blue whales will be impeded by feeding competition with sympatric minke whales. Accepted: 29 April 1999     

A major feeding ground for cetaceans and seabirds in the south-western Greenland Sea

In the frame of our long-term study of the distribution of seabirds and marine mammals in polar seas, observers from this team participated in the European Arctic expeditions of icebreaking RV Polarstern during summer 2008. The main aims were to obtain more information on the mechanisms underlying the at-sea distribution of the ??higher trophic levels?? and to detect possible temporal and spatial changes in numbers, especially in function of climatic changes and decreasing ice coverage in the Arctic. In total, 1,175 half-an-hour transect counts were devoted to seabird and marine mammal distribution in the Greenland and Norwegian Seas, from 14 June to 15 August, 2008. A major feeding ground for cetaceans and seabirds was detected in the south-western Greenland Sea and the Denmark Strait in the Polar Front between Polar and Arctic Water masses. For the main cetacean and seabird species, almost all individuals recorded during the whole expedition were encountered in this limited zone of 33 counts: 135 humpback whales Megaptera novaeangliae and 1,940 common guillemots Uria aalge. Moreover, 4,400 fulmars Fulmarus glacialis light morph were observed in this zone, i.e. close to half of the total. All were actively feeding, making this zone the major feeding ground for the higher trophic levels in the European Arctic Seas and so confirming the great importance of fronts (upwellings) for the biological productivity of the oceans. Such data are essential for a successful conservation and management of the Denmark Strait and adjacent areas.     

Lipids in the daubed shanny (Teleostei: Leptoclinus maculatus) in Svalbard waters

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.     

Influence of diet and foraging strategy on reproductive success in two morphologically similar sympatric seabirds

Capsule: Morphologically similar sympatrically breeding species differ in diet and foraging strategies, which could explain interspecific variation in breeding success and reproductive output.

Aims: To compare provisioning rate and diet of nestling Arctic (Sterna paradisaea) and Common Terns (Sterna hirundo), and examine how variation in provisioning behaviour influences reproductive parameters.

Methods: Arctic and Common Tern nests were observed from June to July 2011 on Coquet Island, northeast England. We compared chick provisioning rate, diet and energy delivery rate between species, and examined whether these parameters were associated with interspecific differences in chick growth and survival, and total number of chicks fledged.

Results: Arctic Terns delivered higher percentages of smaller Sandeels (Ammodytes marinus) and juvenile fish to chicks than did Common Terns, which delivered comparatively high percentages of larger Sprats (Sprattus sprattus). Although chick growth rate and survival were not significantly different between species, Common Terns fledged more chicks than Arctic Terns due to a tendency for larger clutch sizes.

Conclusion: Our study suggests that interspecific differences in diet and foraging strategies can support total reproductive output in morphologically similar species.     

Summer seawater tolerance of small-sized Arctic charr, Salvelinus alpinus, on Svalbard

Migrating Arctic charr (Salvelinus alpinus) parr (118 ± 34.4 mm) were caught close to the rivermouth of the Dieset river on Spitsbergen (79°10′N), Svalbard. When subjected to a seawater tolerance test (34 ppt at 6°C) their blood plasma osmolality and sodium and magnesium concentrations increased significantly. After 90 h of exposure, average plasma osmolality was 410 (±54.1) mOsmol. Corresponding sodium and magnesium concentrations were 207 (±35.9) mmol l⁻¹ and 2.7 (±1.36) mmol l⁻¹, respectively. Survival at this time was only 12.5%. When smaller fish (96 ± 26.6 mm) were exposed to seawater, mortality was 100% within 72 h. We conclude that small-sized Svalbard charr may survive only short periods in seawater. Therefore, the lack of adequate hypoosmoregulatory capacity limits their access to marine food resources. Received: 29 December 1997 / Accepted: 12 April 1998