Distribution of <Emphasis Type="Italic">Calanus</Emphasis> populations in a glaciated fjord in the Arctic (Hornsund,Spitsbergen)—the interplay between biological and physical factors

The distribution and diversity of copepods of the genus Calanus were investigated in Hornsund Fjord (on the southwest coast of Spitsbergen) in summer 2001. The Bhattacharya method was used to sort individuals by species based on their prosome length. The established prosome length boundary values for the Calanus copepodid stages coincided with those defined for the Calanus species from Kongsfjorden (on the northwest coast of Spitsbergen). The predominant species in the main and inner fjord basins was Calanus glacialis, whereas Calanus finmarchicus was the prevailing species outside Hornsund. Younger copepodid stages (CI–CIII) of both species concentrated in the surface water layers (0–50∼70 m), while older copepodids (CIV–CVI females) that were ready for wintering stayed in deep layers (50∼70 m to bottom). Calanus hyperboreus was present in low numbers, predominantly as CIV, and in Hornsund deep water layers. The distribution and diversity of Calanus species complied with the notion that the marine fauna in Hornsund is of a more Arctic character than in Kongsfjorden, a fjord 260 km to the north on the west coast of Spitsbergen.     

Stable oxygen and carbon isotope information on the establishment of a new, opportunistic foraminiferal fauna in a Swedish Skagerrak fjord basin, in 1979/1980

Significant faunal changes reported from recent, coastal environments, which are not directly influenced by urban and industrial impact, are rarely seen. In Gullmar Fjord on the Swedish west coast, a significant foraminiferal fauna change occurred in connection with severe low-oxygen conditions that evolved in the winter of 1979/1980. A foraminiferal fauna marked by common Skagerrak–Kattegat species, which had previously characterised the deep fjord basin, was replaced by the opportunistic, low-oxygen tolerant species Stainforthia fusiformis (Williamsson).To study this phenomenon further we performed stable oxygen and carbon isotope analyses on the indicator species itself, S. fusiformis, both on specimens from sediment cores representing approximately the last 85 years and on living (stained) individuals taken from a transect across the deep fjord basin. Our purpose was to detail how and why S. fusiformis, came to dominate the fauna.The oxygen isotope results suggest that salinities and temperatures in the deep basin have been relatively constant over the last c. 85 years, while the carbon isotopes show a significant change towards more negative values in association with the faunal shift of 1979/1980. The combined results from both the cores and the surface sediments suggest that S. fusiformis did not inhabit the deep basin until 1980. Before then, almost all specimens of S. fusiformis were small sized and their carbon isotope values suggest they were re-deposited shallow-water specimens that had been transported down to the central, deep basin as part of a suspension load. After a major faunal extinction in 1979–1980, S. fusiformis of all sizes suddenly appeared in large numbers and their carbon isotopic values were similar to the signal from registered in the recent, living fauna within the deep basin. This suggests that the opportunistic S. fusiformis established itself in the deep basin as a consequence of the severe low-oxygen event and the faunal crash of the previously dominating Skagerrak–Kattegat fauna.     

Diversity estimates of microeukaryotes below the chemocline of the anoxic Mariager Fjord, Denmark

Microbial communities of extreme environments have often been assumed to have low species richness. We analysed 18S rRNA gene signatures in a sample collected below the chemocline of the anoxic Mariager Fjord in Denmark, and from these data we computed novel parametric and standard nonparametric estimates of protistan phylotype richness. Our results indicate unexpectedly high richness in this environment: at the 99.5% phylotype definition, our most conservative estimate was 568 phylotypes (+/-114, standard error). Phylogenetic analyses revealed that the sequences collected cover the majority of described lineages in the eukaryotic domain. Out of 384 sequences analysed, 307 were identified as protistan targets, none of which was identical to known sequences. However, based on what is known about species that are phylogenetically related to the Mariager sequences, most of the latter seem to belong to strictly or facultative anaerobe organisms. We also found signatures that together with other environmental 18S rRNA gene sequences represent environmental clades of possibly high taxonomic levels (class to kingdom level). One of these clades, consisting exclusively of sequences from anoxic sampling sites, branches at the base of the eukaryotic evolutionary tree among the earliest eukaryotic lineages. Assuming eukaryotic evolution under oxygen-depleted conditions, these sequences may represent immediate descendants of early eukaryotic ancestors.     

A diatom-based reconstruction of Early Holocene hydrographic and climatic change in a southwest Greenland fjord

A diatom-based reconstruction of surface-water paleoclimatic and paleoceanographic changes in Ameralik Fjord, southwest Greenland, is presented for the Holocene interval 8800 to 3600 cal yrs B.P. A minor episode of cold surface-water conditions is found at ca. 8000–7800 cal yrs B.P. This may be due to the local conditions in the fjord and linked to the culmination of a strong melt-water outflow rather than reflecting the widespread North Atlantic (8.2 ka) cooling event. Warming of surface-water condition from 7800 to 7100 cal yrs B.P., probably corresponding to the early and warmest part of the Holocene Thermal Maximum (HTM) in this region, is reflected in the diatom assemblages and supported by other proxies. The West Greenland Current (WGC) influences the fjord strongly during this interval, indicating enhanced advection of Atlantic water-masses derived from the Irminger Current (IC). A major sedimentary change with a hiatus between 6800 and 4400 cal yrs B.P. prevents a reconstruction of mid-Holocene paleoceanograpy. The final and less prominent part of the HTM is found after 4400 cal yrs B.P. Previous studies from the same site have shown this final stage of the HTM to end at 3200 cal yrs B.P. with the onset of the ‘Neoglaciation’. Our study provides further evidence that the marine sedimentary record from West Greenland fjords yields paleoenvironmental information reflecting a significant link between local and large scale North Atlantic oceanographic and climatic changes.     

Fouling community of the red king crab, <Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis> (Tilesius 1815), in a subarctic fjord of the Barents sea

We examined the species composition of red king crab (Paralithodes camtschaticus) fouling communities in Dolgaya Bay, a small fjord of the Barents Sea, in August 2005 and 2006. In total, there were 13 species observed on 301 crabs collected from water depths of 5–90 m. Barnacles (Balanus crenatus; prevalence 42.9%) and blue mussels (Mytilus edulis; 11.6%) were the most common epibionts, while amphipods (Ischyrocerus commensalis) were the most common symbionts (28.6%). Infestation rates in Dolgaya Bay were different from those in an “open” area of the Barents Sea (Dalnezelenetskaya Bay), probably due to differences in hydrodynamic conditions. Differences in infestation prevalence and intensity were detected neither between male and female crabs nor between crabs collected at 5–35 m versus 90 m depths. Prevalence of common fouling species increased with host size. Amphipods I. commensalis colonized the carapace and limbs in Dolgaya Bay less frequently than in Dalnezelenetskaya Bay, probably due to interspecific competition with barnacles occupying the dorsal parts of the host. Juvenile barnacles and mussels dominated the fouling communities on the crabs. The age of barnacles did not exceed 2–4 months. However, the presence of 4-year-old mussels suggests that these older mollusks have been directly transferred from mussel beds to the hosts. Our results indicate that colonization by epibionts and symbionts is generally not disadvantageous for the crab hosts, except for some possible negative impacts of amphipods occupying the gills.     

SEASONAL VARIABILITY IN POLYUNSATURATED ALDEHYDE PRODUCTION POTENTIAL AMONG STRAINS OF SKELETONEMA MARINOI (BACILLARIOPHYCEAE)1

The cosmopolitan bloom‐forming diatom Skeletonema marinoi Sarno et Zingone is known to produce toxic polyunsaturated aldehydes (PUAs) in response to cell damage that can affect a diverse suite of organisms, including grazing species and competitor plankton species. The production of PUAs in nine different S. marinoi strains isolated at three different times of the year (spring, summer, and autumn) was assessed in relation to the predominant conditions at the time of isolation from Gullmar Fjord, Skagerrak. During the initial stages of growth, PUA production potential of S. marinoi was generally the highest in summer strains, although there was a substantial variation among strains isolated at the same time. Spring strains, however, showed a strong capacity for increased PUA production potential in later stage cultures with diminishing nutrient levels, reaching amounts similar to those observed in summer strains. In contrast, PUA production potentials of summer and autumn strains did not change significantly from the original values. There is negligible grazing pressure during the spring bloom in Gullmar Fjord, but a potential for high competition for resources, such as nutrients, toward the later stages of the bloom. In contrast, grazing pressure is much greater during summer and autumn, and there may also be nutrient limitation at this time. The PUA production potentials of S. marinoi appear to reflect the ecological conditions at the time of isolation with higher production potentials in strains isolated when conditions were likely to be less beneficial for survival.     

Aspects of winter primary production in the upstream section of Saguenay Fjord

From August 1985 to May 1986, experiments on primary production were carried out bi-weekly in the superficial waters (1–10 m) at one representative station (maximum depth of 260 m) located at the head of the Saguenay Fjord. During the winter season (January–March), the microalgal cells are abundant but their productivity is low. At the beginning of the snow-ice cover (January) the cells are mainly concentrated in the ice-cover interface and in the surface waters whereas in February–March, the cells are much more abundant in the ice. Results showed that the physico-chemical conditions are unfavourable for high productivity. The quantity and the quality of light under the ice cover are not the only factors limiting the photosynthetic activity of epontic community. The ice interior and epontic communities during the winter are mostly composed of the two euryhaline speciesAsterionella formosa andTabellaria fenestrata.     

Fjord migration and survival of wild and hatchery-reared Atlantic salmon and wild brown trout post-smolts

The behaviour of wild (n = 43, mean L_T = 152 mm) and hatchery-reared (n = 71, mean L_T = 198 mm) Atlantic salmon and wild anadromous brown trout (n = 34, mean L_T = 171 mm) post-smolts with acoustic transmitters was compared in a Norwegian fjord system. There was no difference in survival between wild and hatchery reared salmon from release in the river mouth to passing receiver sites 9.5 km and 37.0 km from the release site. Mortality approached 65% during the first 37 km of the marine migration for both groups. There was no difference between wild and hatchery-reared salmon either in time from release to first recording at 9.5 km (mean 135 and 80 h), or in the rate of movement through the fjord (mean 0.53 and 0.56 bl s⁻¹). Hatchery-reared salmon reached the 37 km site sooner after release than the wild salmon (mean 168 and 450 h), but rate of movement in terms of body lengths per second did not differ (mean 0.56 and 0.77 bl s⁻¹). The brown trout remained a longer period in the inner part of the fjord system, with much slower rates of movement during the first 9.5 km (mean 0.06 bl s⁻¹).     

Ostracods in a cold-temperate coastal environment, Western Troms, Northern Norway: Sedimentary aspects and assemblages

Summary This study presents sedimentological and micropaleontological data on ostracods from a cold-temperate inner shelf setting in the Troms District, northern Norway. The coarse fraction analyses carried out on sediment surface samples from coastal platforms and adjacent outer fjord troughs reveal a considerable contribution from ostracods to the accumulation of skeletal carbonates in distinct depositional settings. Ostracod accumulation is highest along wave-sheltered areas of coastal platforms where fleshy seaweed and coralline algal communities thrive in 10 to 30 m water depth. Current-exposed slopes of outer fjord troughs show a highly mixed ostracod assemblage consisting of imported species from the shallow coastal platform which is mixed with the trough assemblage. The hydrodynamic transport of ostracods into deeper areas results from the strong tidal current regime. Because of this mixing process, only the end members, the coastal platform and the fjord trough assemblages can be defined. The former is characterized byBaffinicythere emarginata, Cythere lutea, Finmarchinella angulata, Hemicytherura clathrata, Robertsonites tuberculatus, Sclerochilus rudjakovi, Semicytherura undata andXestoleberis cf.depressa. The outer fjord trough assemblage is characterized byCluthia cluthae, Cytherella abyssorum, Cytheropteron alatum, Krithe cf.adelspergi, Muellerina abyssicola, Cytherella cf.vulgatella andCytheropteron testudo. Members of the northern Norwegian trough assemblage are known to occur in deeper open shelf environments of the NE-Atlantic.     

Late Weichselian and Holocene sedimentary environments and ice rafting in Isfjorden, Spitsbergen

Multi-proxy analyses of two sediment cores from central Isfjorden were used to reconstruct the glacial history in central Spitsbergen during the Late Weichselian and the Holocene, and to relate iceberg rafting and sea-ice rafting to climatic and oceanographic changes in the north Atlantic region. A basal till was deposited beneath an ice stream prior to 12,700 cal. years BP (calendar years before the present). Several tidewater glaciers influenced the sedimentary environment during the Younger Dryas and probably already during the Allerød. The Younger Dryas cooling might be reflected by enhanced sea-ice formation and suspension settling, as well as reduced iceberg rafting. The final deglaciation was dominated by intense iceberg rafting. It terminated around 11,200 cal. years BP. Optimum Holocene climatic and oceanographic conditions with significantly reduced ice rafting occurred between c. 11,200 and 9000 cal. years BP. Ice rafting occurred almost exclusively from icebergs after 10,200 cal. years BP. The icebergs most probably originated from tidewater glaciers on east Spitsbergen, indicating the presence of a strong east–west temperature gradient at this time. An increase of iceberg rafting around 9000 cal. years BP, followed by enhanced sea-ice rafting, reflects the onset of a general cooling in the western Barents Sea–Svalbard region. Comparatively intense rafting from icebergs and sea ice between 9000 and 4000 cal. years BP is related to this cooling. A general reduction in ice rafting after 4000 cal. years BP is most probably the result of the enhanced formation of shore-fast and/or more permanent sea-ice cover, reducing the drift of icebergs and sea ice in the fjord. The results indicate that the palaeoenvironmental conditions on central Spitsbergen to a large degree depended on the oceanographic conditions in the western Barents Sea and west off Spitsbergen. However, climatic trends affecting Greenland and the entire north Atlantic region can also be identified.