Observations on diatoms inhabiting natural and artificial substrates in Kongsfjorden,Svalbard, the Arctic

Polar Biology - The most dramatic effects of global climate change are predicted for the Arctic, and there is a raising concern about the lack of baseline information on microalgal biodiversity....     

Population genetic structure of the ascidian Styela rustica at Kongsfjorden, Svalbard, Arctic

The actual Arctic biota shows a strong affinity with that of the Boreal Atlantic and Pacific ones, as a result of an active recolonization process after the Quaternary glaciations. The geographic distribution of sessile species is usually linked to larvae dispersive capabilities which can be directly related with time spent in the plankton. Ascidians larvae are lecitothorphic and short-lived, which suggest that ascidians could be not efficient dispersers. However, the solitary ascidian Styela rustica (Linnaeus, 1767) (Tunicata, Ascidiacea) shows a wide distribution pattern from the North Atlantic to the Arctic that, together with the relatively recent colonization of the Arctic system could indicate that this species efficiently disperses and colonizes new habitats. In this study we used ISSR-PCR markers to study the genetic structure of five populations of the ascidian Styela rustica at Kongsfjorden, west Spitsbergen (Svalbard archipelago). We analyzed whether this species presents a low genetic structure, as can be expected due to the historical process of recent post glaciations colonization, or if there is genetic differentiation at a local scale, caused by short-lived larvae and limited dispersal potential. The genetic diversity in each population assessed using the marker diversity index (M) ranged from 0.288 to 0.324. Population HN, situated close to a fast retreating glacier, showed the lowest diversity. Processes associated with deglatiation (icebergs calving from the glacier that scour the benthos and the increment of inorganic particulate matter on the water column) would drive to reduced population sizes and explain the reduced genetic variability observed in the HN population with respect to the others in the fjord. This suggests a possible linkage with the global warming process. Although the weak genetic structure found among the studied populations could indicate a founder effect, the genetic landscape shape analysis together with a positive relationship between genetic and geographic distances also suggest possible current gene flow among populations in the fjord.     

Diversity of microbial eukaryotes in Kongsfjorden,Svalbard

Microbial eukaryote diversity was assessed in Arctic Kongsfjorden (Svalbard), by constructing SSU rDNA clone libraries. Samples were collected from different depths at the outer basin in summer (2006), plus an additional one glacial and one sediment sample. The libraries displayed diversity based on 284 full-length sequences. Four main phyla, namely, Alveolates, Stramenopiles, Cercozoans, and Metazoans were often screened in this fjord. Alveolate occupied the highest percentage of taxa in the library of surface sea water, besides the Metazoan-related clones. Moreover, dinoflagellates, diatoms, and pico-Prasinophytes were detected as prevalent phytoplankton through the analysis of libraries. Questions related to the quantity of these phytoplankton and their roles in the microbial food loop arose from an ecological viewpoint.     

Decadal change in macrobenthic soft-bottom community structure in a high Arctic fjord (Kongsfjorden, Svalbard)

Marine benthic macrofauna communities are considered a good indicator of subtle environmental long-term changes in an ecosystem. In 1997/1998 and 2006, soft-bottom fauna of an Arctic glacial fjord Kongsfjorden was extensively sampled and major communities were identified along the fjord axis, which were related to the diminishing influence of glacial activity. Spatial patterns in community structure and species diversity were significantly different in the central basin of Kongsfjorden between periods while there was no change in the inner part of the fjord. In 1997/98, three faunal associations were distinguished with significant differences in species richness and diversity (H′) while in 2006 only two faunal associations were identified and there were no differences any more between the two formerly distinct associations in the central fjord. The increased input of Atlantic water due to a stronger West Spitsbergen Current may be the reason for unification of previous clear faunal division. The faunal association in the inner, well separated glacial part of the fjord, characterized by strong glacier influence, was protected from Atlantic water inflow and, hence, the macrobenthic fauna essentially remained unaffected. Reduced abundance of species typical for glacial bays in the central part of the fjord in 2006 may result from the decreasing effect of Blomstrandbreen glacier, strong increase of input of Atlantic water into the fjord and increased temperature of West Spitsbergen Current. Higher values of POC in 2006 than in 1998 are likely the effect of increased primary production resulting from warmer water temperatures.     

Microphytobenthos of Arctic Kongsfjorden (Svalbard, Norway): biomass and potential primary production along the shore line

During summer 2007, Arctic microphytobenthic potential primary production was measured at several stations around the coastline of Kongsfjorden (Svalbard, Norway) at ≤5 m water depth and at two stations at five different water depths (5, 10, 15, 20, 30 m). Oxygen planar optode sensor spots were used ex situ to determine oxygen exchange in the overlying water of intact sediment cores under controlled light (ca. 100 μmol photons m⁻² s⁻¹) and temperature (2–4°C) conditions. Patches of microalgae (mainly diatoms) covering sandy sediments at water depths down to 30 m showed high biomass of up to 317 mg chl a m⁻². In spite of increasing water depth, no significant trend in “photoautotrophic active biomass” (chl a, ratio living/dead cells, cell sizes) and, thus, in primary production was measured at both stations. All sites from ≤5 to 30 m water depth exhibited variable rates of net production from −19 to +40 mg O₂ m⁻² h⁻¹ (−168 to +360 mg C m⁻² day⁻¹) and gross production of about 2–62 mg O₂ m⁻² h⁻¹ (17–554 mg C m⁻² day⁻¹), which is comparable to other polar as well as temperate regions. No relation between photoautotrophic biomass and gross/net production values was found. Microphytobenthos demonstrated significant rates of primary production that is comparable to pelagic production of Kongsfjorden and, hence, emphasised the importance as C source for the zoobenthos.     

Marine Group-II archaea dominate particle-attached as well as free-living archaeal assemblages in the surface waters of Kongsfjorden,Svalbard, Arctic Ocean

Antonie van Leeuwenhoek - Marine archaea are a significant component of the global oceanic ecosystems, including the polar oceans. However, only a few attempts have been made to study archaea in...     

Trophic variability of Arctic fishes in the Canadian Beaufort Sea: a fatty acids and stable isotopes approach

Trophic ecology of most demersal Arctic fishes remains one of the major knowledge gaps for understanding food web dynamics and connectivity among ecosystems. In this study, fatty acids (FA) and stable isotopes (SI) were used to study the feeding ecology of seven species (n = 106) of the most abundant benthic fishes (eelpouts, sculpins and agonids) in the Canadian Beaufort Sea from shallow (20–75 m), slope (200–350 m) and deep (500–1000 m) habitats. Both FA and SI results revealed among- and within-species variability in diet composition. Correspondence analysis of FA signatures identified high within-species variability in diet, resulting in high overlap among species. Calanus-derived FA were present in all species (Calanus markers up to 13 % of total FA) and were particularly important in Ribbed Sculpin, Adolf’s and Longear Eelpout collected in deep habitats, suggesting a strong contribution of pelagic-derived FA to benthic fish communities. Incorporation of this signal in the benthos may result from either direct consumption of deep overwintering copepods (i.e., off-bottom feeding) or through detrital accumulation in benthic invertebrate prey. Mean SI values differed among species and indicated that a large range of trophic positions (δ¹⁵N varied from 14.09 to 17.71 ‰ for Canadian Eelpout and Adolf’s Eelpout, respectively) and carbon dietary sources are preyed upon (δ¹³C range from ?21.13 to ?23.85 ‰ for Longear Eelpout and Ribbed Sculpin, respectively). SI analyses suggested that most species examined were low- to mid-trophic generalist benthic carnivores, with the exception of Ribbed Sculpin, which was a low-trophic pelagic predator.     

Distribution of Calanus species in Kongsfjorden, a glacial fjord in Svalbard

The distribution of Calanus species was investigated in Kongsfjordenin summer of 1996 and 1997. In both years Calanus finmarchicusand Calanus glacialis dominated, although the boreal C. finmarchicuswas more abundant than the Arctic C. glacialis in 1997. Thiscoincided with a 2°C higher water temperature at 50 m in1997, indicating stronger influence of Atlantic origin waterthat year. Advected Calanus finmarchicus occurred in deep andsubsurface layers of the outer fjord in 1996 (200 ind. m^-3,mainly CIII). A less abundant local population aggregated insurface layers of the inner fjord (100 ind. m^-3). Similarly,advected C. finmarchicus occurred in subsurface layers in 1997(446 ind. m^-3, mainly CIII and CIV) and a local population insurface layers (183 ind. m^-3, mainly CI). Calanus glacialisin 1996 aggregated as CII and CIII in the deep layers of theouter fjord (272 ind. m^-3), whereas CIII–CV were abundant(216 ind. m^-3) in cold surface waters of the inner fjord. In1997 C. glacialis (mostly CIII–CV) was more abundant inthe outer than in the inner part of the fjord (40 and 192 ind.m^-3, respectively). Within Kongsfjorden, Calanus finmarchicusneeds one year to complete its life cycle, whereas Calanus glacialisneeds two. Calanus hyperboreus seems to be an expatriate inthe fjord system.     

Yolk carotenoids and stable isotopes reveal links among environment, foraging behavior and seabird breeding success

Nutrients that are limited in availability, such as carotenoids, are potentially involved in trade-offs between homeostasis and reproduction. Despite their importance, factors that affect the capacity of female birds to meet their carotenoid requirements are poorly understood. We used δ¹⁵N stable isotope analysis to relate foraging behavior to yolk carotenoid deposition in two seabirds, Cassin’s auklet (Ptychoramphus aleuticus) and rhinoceros auklet (Cerorhinca monocerata), during each of five years. As expected from their narrower trophic range, Cassin’s auklets produced yolks with fewer carotenoid types than did rhinoceros auklets (one vs. three). Cassin’s auklets also fed on a lower trophic level diet richer in carotenoids, yet had lower total yolk carotenoid levels, which suggests a role for species-specific adaptations for carotenoid uptake and utilization. Within both species, lower trophic-level feeding was linked to higher yolk carotenoid levels, but through different mechanisms. In Cassin’s auklets, it was due to a population-wide response to environmental variation: in warm-water years, all females fed at a low trophic level and produced carotenoid-rich yolks. In rhinoceros auklets, it was due to individual differences similarly expressed in all years: females fed across a wide trophic range, and those that fed at a low trophic level produced carotenoid-rich yolks. Rhinoceros auklets bred more successfully in years when their yolks were rich in carotenoids, probably due to a correlated response to stronger marine primary production. Our results are novel because they link avian yolk carotenoid deposition to behavioral and environmental variations.     

The invertebrate fauna of High Arctic seabird nests: the microarthropod community inhabiting nests on Spitsbergen,Svalbard

The invertebrate fauna of the nests of three seabird species, black-legged kittiwakes (Rissa tridactyla), common eider (Somateria mollissima) and glaucous gull (Larus hyperboreus), were sampled in Kongsfjorden, Spitsbergen, Svalbard. The invertebrate community was species poor, consisting predominantly of the flea, Mioctenopsylla arctica arctica (Insecta: Siphonaptera), but with six species of oribatid mite (Acari: Oribatida), Diapterobates notatus, Oribatula tibialis, Ameronothrus lineatus, Hermannia reticulata, Trichoribates trimaculatus and Ceratoppia bipilis, plus an occasional mesostigmatid mite. No Collembola or ticks (Acari: Ixodidae) were observed. With the exception of M. arctica arctica, the fauna of seabird nests consisted of opportunistic microarthropod species rather than specialised nest-dwelling or bird parasitic species. Species diversity of soil oribatid mites was greater in nests of the common eider than compared to nests of the black-legged kittiwake, which may be related to the ground nesting behaviour of the common eiders. No rare or unusual microarthropod species for Svalbard were found in the seabird nests. The contentions that nests may facilitate microarthropod colonisation of High Arctic regions via bird phoresy by providing a high-quality habitat at the point of arrival, or that there might be a specialised microarthropod fauna exploiting this habitat, were not supported in this study. These are amongst the first data on the microarthropod community of seabird nests in the High Arctic.     

Effect of exercise on protein metabolism in humans as explored with stable isotopes

Exercising for 3.75 h on a treadmill at 50% VO2 max in the fed state induced an increased excretion of 71 mg nitrogen/kg over the 18 h after exercise. However, measurements of the time course of changes in 13CO2 excretion from ingested [1-13C]leucine indicated that all of this increased nitrogen production occurs during the exercise period. Because of the reduced renal clearance and slow turnover of the urea pool, urea excretion lags behind urea production. Measurements of nitrogen flux from the plateau labeling of urinary ammonia achieved by repeated oral doses of 15N-labeled glycine indicated that the nitrogen loss resulted from an increase in protein degradation and a decrease in protein synthesis. Further studies with [1-13C]leucine indicated that a 2-h treadmill exercise induced an increase in the nitrogen loss from 5.4 to 16 mg . kg-1 . h-1 measured with a primed constant infusion of [1-13C]leucine. This resulted from a fall in whole-body protein synthesis. Glucose given at the rate of 0.88 g . kg-1 . h-1 depressed the rate of whole-body protein degradation and appeared to suppress the exercise-induced increase in nitrogen excretion. When leucine oxidation rates were measured at increasing work rates, a linear relationship between percentage of VO2 max and leucine oxidation was observed up to 89% VO2 max when 54% of the flux of leucine was oxidized. These changes may involve nonmuscle as well as muscle tissue. Thus the source of the increased nitrogen losses is probably liver. In muscle, protein degradation is actually decreased judged by methylhistidine excretion, whereas in liver, protein degradation may be increased. Also the fall in whole-body protein synthesis may reflect changes in nonmuscle tissues because in running rats protein synthesis in muscle is maintained. As far as leucine metabolism is concerned, because the increase in leucine oxidation occurs when leucine and its keto acid concentration falls, exercise must specifically activate the 2-oxoacid dehydrogenase.     

Soft bottom species richness and diversity as a function of depth and iceberg scour in Arctic glacial Kongsfjorden (Svalbard)

Macrozoobenthic soft-sediment communities of central Arctic Kongsfjorden inhabiting six depth zones between 5 and 30 m were sampled using SCUBA-diving during June–August 2003 and analysed comparatively. About 63 taxa were found, nine of which had not been reported for Kongsfjorden and four for Svalbard. Suspension feeding or surface and sub-surface detritivorous polychaetes and deposit-feeding amphipods were dominant. Only 11 of the 63 taxa (45 species and additional 18 families not further identified) inhabited the complete depth range. Biomass ranged from 3.5 to 25.0 g ash free dry mass m⁻² and mean Shannon diversity (Log e) was 2.06. Similarity clustering from abundance and biomass data showed a significant difference between the shallow station (5 m) and the rest. The latter formed two sub-groups (10–20 and 25–30 m). Depth is irrevocably correlated with ice-scouring. Thus the differences in diversity together with the predicted iceberg scour intensity support the ‘intermediate disturbance hypothesis’ indicating that habitats impacted by moderate iceberg scouring enable higher diversity. In contrast, biotopes frequently affected only host pioneer communities, while mature, less diverse assemblages dominate depths of low impact.     

Spring bloom dynamics in Kongsfjorden,Svalbard: nutrients,phytoplankton, protozoans and primary production

The marine ecosystem in Kongsfjorden (79°N), a glacial fjord in Svalbard, is to a large extent well known with regard to hydrography, mesozooplankton and higher trophic levels. Research on primary production and lower trophic levels is still scare and especially investigations from winter and spring periods. The spring bloom dynamics in Kongsfjorden were investigated in 2002. The development in nutrient conditions, phytoplankton, protozoans and primary production were followed from 15 April until 22 May. The winter/spring in 2002 was categorized as a cold year with sea ice cover and water masses dominated by local winter-cooled water. The spring bloom started around 18 April and lasted until the middle of May. The bloom probably peaked in late April, but break-up of sea ice made it impossible to sample frequently in this period. Diatoms dominated the phytoplankton assemblage. We estimated the total primary production during the spring bloom in 2002 to range 27–35 g C m⁻². There was a mismatch situation between the mesozooplankton and the phytoplankton spring bloom in 2002.     

The distribution of picoplankton and nanoplankton in Kongsfjorden,Svalbard during late summer 2006

Abundance and biomass of pico- (<2 μm) and nanoplankton (2–20 μm) were investigated in relation to hydrography in Kongsfjorden, Svalbard (79°N, 12°E) during late summer 2006. Autotrophic and heterotrophic picoplankton abundance ranged from 0.1 × 10⁶ to 35.2 × 10⁶ cells L⁻¹ and from 0.4 × 10⁶ to 20.3 × 10⁶ cells L⁻¹, respectively. The highest number of bacteria in the entire water column was recorded at station 2 at 10 m (22.3 × 10⁸ cells L⁻¹); the lowest concentration was observed at station 1 (6.0 × 10⁸ cells L⁻¹). The abundance of autotrophic and heterotrophic nanoplankton varied from 0.4 × 10⁵ cells L⁻¹ to 46 × 10⁵ cells L⁻¹ and from 0.3 × 10⁶ to 9.1 × 10⁶ cells L⁻¹, respectively. Our results demonstrated that heterotrophic nanoflagellates and bacteria in Kongsfjorden microbial community were relatively important. The structure of plankton communities integrated with environmental variables could act as indicators of the variability of the inflow of Atlantic Water into Kongsfjorden.     

Effect of dietary fatty acid composition on food intake, triglycerides, and hypothalamic peptides

While a high-fat diet when compared to low-fat diet is known to produce overeating and health complications, less is known about the effects produced by fat-rich diets differing in their specific composition of fat. This study examined the effects of a high-fat diet containing relatively high levels of saturated compared to unsaturated fatty acids (HiSat) to a high-fat diet with higher levels of unsaturated fatty acids (USat). A HiSat compared to USat meal caused rats to consume more calories in a subsequent chow test meal. The HiSat meal also increased circulating levels of triglycerides (TG) and expression of the orexigenic peptides, galanin (GAL) in the hypothalamic paraventricular nucleus (PVN) and orexin (OX) in the perifornical lateral hypothalamus (PFLH). A similar increase in TG levels and PVN GAL and PFLH OX was also seen in rats given chronic access to the HiSat compared to USat diet, while neuropeptide Y (NPY) and agouti-related protein (AgRP) in the arcuate nucleus showed decreased expression. The importance of TG in producing these changes was supported by the finding that the TG-lowering medication gemfibrozil as compared to vehicle, when peripherally administered before consumption of a HiSat meal, significantly decreased the expression of OX, while increasing the expression of NPY and AgRP. These findings substantiate the importance of the fat composition in a diet, indicating that those rich in saturated compared to unsaturated fatty acids may promote overeating by increasing circulating lipids and specific hypothalamic peptides, GAL and OX, known to preferentially stimulate the consumption of a fat-rich diet.     

Temporal patterns of benthic community development in an Arctic fjord (Kongsfjorden, Svalbard): results of a 24-year manipulation study

We investigated temporal patterns of recolonisation and disturbance in a benthic hard bottom community in high-arctic Kongsfjorden from 1980 to 2003 through annual photographic surveys. A manipulative sampling design was applied, where half of the study area (treatment areas) was cleared at the beginning of the study. Twenty-three different taxa and groups of benthic epifauna were found in the photographs. The benthic community structures of treatments and controls converged within the first decade, but significant differences prevailed until ≤13 years after the start of the study. We could distinguish between three different time intervals with increased inter-annual changes. While the observed differences during the first two intervals could be attributed to recolonisation and succession, the changes in interval 3 were mostly due to increased external forcing and characterised by low inter-group and high inter-annual differences. During this interval, brown algae (mainly Desmarestia) and the sea urchin Strongylocentrotus droebachiensis emerged in high densities, while sea anemone populations declined. Different recolonisation patterns for individual species were related to life span, rate of maturity, predators and larval settlement. We could not find a climax stage in the succession for the benthic community at Kvadehuken, presumably due to the constant level of disturbances at the site.     

Intertidal meiofauna of a high-latitude glacial Arctic fjord (Kongsfjorden, Svalbard) with emphasis on the structure of free-living nematode communities

Meiofauna communities of four intertidal sites, two sheltered and two more exposed, in Kongsfjorden (Svalbard) were investigated in summer 2001 at two different tidal levels (i.e. the low-water line and close below the driftline, referred to as mid-water (MW) level). A total of seven meiofaunal higher taxa were recorded with nematodes, oligochaetes and turbellarians being numerically dominant. Mean total meiofaunal densities ranged between 50 ind. 10 cm⁻² and 903 ind. 10 cm⁻². Our data showed a clear decrease in total meiofaunal densities with increasing coarseness of the sediment. Total meiofaunal biomass varied from 0.2 g dwt m⁻² to 2 g dwt m⁻² and, in general, was high even at low meiofaunal densities, i.e. larger interstitial spaces in coarser sediments supported larger meiofauna, especially turbellarians. The results on the vertical distribution of meiofauna contrasted sharply with typical meiobenthic depth profiles on other beaches, probably in response to ice-scouring and concomitant salinity fluctuations. Oligochaetes were the most abundant taxon, with a peak density of 641 ind. 10 cm⁻² at Breoyane Island. They were mainly comprised of juvenile Enchytraeidae, which prohibited identification to species/genus level. Nematode densities ranged between 4 ind. 10 cm⁻² and 327 ind. 10 cm⁻². Nematodes were identified up to genus level and assigned to trophic guilds. In total, 28 nematode genera were identified. Oncholaimus and Theristus were the most abundant genera. The composition of the nematode community and a dominance of predators and deposit feeders were in agreement with results from other arctic and temperate beaches. Nematode genus diversity was higher at the more sheltered beaches than at the more exposed ones. Low-water level stations also tended to harbour a more diverse nematode communities than stations at the MW level. Differences in nematode community structure between low- and MW stations of single beaches were more pronounced than community differences between different beaches and were mainly related to resources quality and availability.     

Population dynamics and body composition of the Arctic hyperiid amphipod Themisto libellula in Svalbard fjords

Population structure, growth and body composition (wet-, dry-, ash weight and total lipid) of the Arctic pelagic amphipod Themisto libellula were studied in four fjords on West Spitsbergen, Svalbard, from July to December 2000 and in April 2002. In one of the fjords, Kongsfjorden, growth of T. libellula was calculated as the change in mean length of the 0+ cohort from July to December. The young were released from the brood pouches in early spring (March–April). Summer growth was 3.5 mm month⁻¹, whereas growth during the autumn was only 0.6 mm month⁻¹. The size frequency distributions indicated a 2–2.5 year life-span. The size structure of the population in Hornsund, the southernmost fjord on Spitsbergen, indicated a delayed time of spawning. The storage of lipids in T. libellula occurred during late summer and towards the winter, when the food items contain the maximum amount of stored lipids.     

Differentiation of benthic marine primary producers using stable isotopes and fatty acids: Implications to food web studies

A two-dimensional biomarker approach, using stable isotopes (δ¹³C, δ¹⁵N) and fatty acids, was used to evaluate differences both amongst and within benthic primary producer types (seagrass, fleshy red algae, calcareous red algae, brown algae, and seagrass periphyton) that are typical of the nearshore, temperate Australian region. The primary source of variance (as examined by permutational ANOVA) for all biomarkers examined was amongst primary producer types, as opposed to amongst species within type. δ¹³C showed a clear separation (Monte Carlo p < 0.05) between seagrass (range of means = −10.1 to −14.0‰) and macroalgae (−14.6 to −25.2‰), but could not differentiate amongst the algal types examined. Similarly, distinct δ¹⁵N signatures (p < 0.05) were found only for seagrass (range of means = 3.6-4.1‰) versus calcareous red algae (4.6-5.5‰), with all other types overlapping in their mean δ¹⁵N values. In contrast, multivariate analysis of fatty acid data (using Canonical Analysis of Principal coordinates; CAP) distinguished not only between seagrass and macroalgae, but also between red and brown algae (and to a limited extent between the calcareous and fleshy red algal types). The principal unsaturated fatty acids in the samples were C₂₀ polyunsaturates (found primarily in the macroalgae and periphyton), and C₁₈ mono- and polyunsaturates, with high proportions of 18:2n-6 and 18:3n-3 typical of the seagrasses. The C₁₈ monounsaturate 18:1n-7 was one of the most diagnostic compounds for the red algae examined, being present in very low amounts in seagrass and virtually absent in the brown algae. Conversely, brown algae were high in 18:4n-3, with 20:4n-3 particularly diagnostic of the kelp Ecklonia radiata. In contrast to stable isotopes, fatty acids helped distinguish different algal groups, thereby providing support that a two-dimensional approach using stable isotopes and fatty acids is likely to provide the most useful tool to distinguish primary producers in food web structure.