Late Pleistocene and Holocene distribution of Mytilus edulis in the Barents Sea region and its palaeoclimatic implications

Aim For decades, subfossil shells of the bivalve Mytilus edulis Linnaeus, 1758 in Svalbard have been taken as evidence of higher surface temperatures during the early Holocene because the modern northern occurrence of this mollusc was, until recently, in the southern Barents Sea. Here, we elucidate and discuss the spatial and temporal Late Pleistocene and Holocene distribution of the species within the entire Barents Sea region. Location The Barents Sea region. Methods Radiocarbon dates of Mytilus shells from the Barents Sea region and information about the present distribution of the species were compiled, including two new radiocarbon dates from north‐eastern Spitsbergen. The dataset was divided into time slices, each covering 1000 years, and compared with Holocene temperature variations, ocean current systems and present‐day temperature patterns. Results Maps show the Late Pleistocene and Holocene spatial and temporal distribution of Mytilus edulis in the Barents Sea region. M. edulis was already present in northern Norway about 14,000 cal. yr bp . It appeared at western Spitsbergen about 11,000 cal. yr bp , and slowly spread to the rest of the archipelago. The maximum distribution in the region was reached 10,000–7000 cal. yr bp , coinciding with the Holocene climatic optimum. The species gradually disappeared in the late Holocene and became absent from the northern and eastern parts of the region 3000–1000 cal. yr bp . Today, M. edulis lives in the southern part and has begun to recolonize the northern parts. Main conclusions The time slices illustrate strong connections between the ocean current regimes, the climate and the distribution of M. edulis. The species settled in the southern part of the Barents Sea region several thousand years before it spread to the northern part during the Holocene climatic optimum. It may even have been completely absent from the region for a short time during the late Holocene cold period. The Holocene distribution of Mytilus implies that the underlying pattern of coastal sea surface temperatures in the region was very stable.     

Distribution of the under-ice mesozooplankton in the Kara Sea in February 2002

Mesozooplankton distribution was investigated under the sea ice in the Kara Sea at five stations in February of 2002 by Juday net hauls. Copepods dominated the mesozooplankton community, accounting for 46–88% of the total abundance and 68–99% of the biomass. Oithona similis was the most abundant species in Yenisei Bay, being present with all age stages (including egg-carrying females). For the first time, Oithona atlantica (CIII–CV copepodites, females and males) were found in the southeastern Kara Sea. In the southern part, Copepoda nauplii prevailed in terms of total abundance while the mesozooplankton in the northwestern part was entirely dominated by older stages of Pseudocalanus minutus. The mesozooplankton structure appears to be determined by available food resources and increased water temperature due to a strong influence of warm Atlantic waters.     

Some aspects of the biology of the amphipods <Emphasis Type="Italic">Ischyrocerus anguipes</Emphasis> associated with the red king crab, <Emphasis Type="Italic">Paralithodes camtschaticus,</Emphasis> in the Barents Sea

This paper describes size composition, morphometric, and reproductive parameters of the summer generation of the amphipod Ischyrocerus anguipes (Krǿyer, 1838) associated with the red king crab Paralithodes camtschaticus (Tilesius, 1815) in Dalnezelenetskaya Bay (southern Barents Sea, Russia). In summer 2004–2007, prevalence and mean number of I. anguipes per host were 15.0% and 6.9 ± 1.1 specimens, respectively. The majority of amphipods were found on the host carapace (47.4%) and the limbs (43.9%). High infestation indices and absence of negative impacts for the host indicate that I. anguipes is a facultative commensal of the red king crab. The amphipods sex ratio was significantly biased toward females (F:M = 2:1). Females had a greater size than males. The size at 50% maturity of I. anguipes females was estimated to be 3.37 mm. The number of eggs laid is linearly correlated with the size of a female. Some differences in biological features of symbiotic and free-living amphipods (data obtained in 1940–1950) may be explained by climatic changes in the Barents Sea or advantages of living on the crab.     

Spatial distribution and life-cycle timing of zooplankton in the marginal ice zone of the Barents Sea during the summer melt season in 1995

The marginal ice zone (MIZ) in the northern Barents Sea is ecologically important because it represents a highly productive area in Arctic water masses north of the Polar Front. During a multi-disciplinary cruise in 1995, ecological and oceanographic processes were investigated at four stations located in a north-south transect in the MIZ. This study was carried out in Arctic water masses north of the Polar Front where ice conditions varied from dense first-year pack ice to open water. Also, the phytoplankton development varied along the transect from a pre-bloom situation at the northern-most station to a post-bloom situation in the open water. This paper includes a study of the zooplankton community and population structure of some of the dominant copepod species. Numerically, the most important mesozooplankton components were the copepods Calanus glacialis, Pseudocalanus minutus and Oithona similis. Copepods of Atlantic origin, such as Calanus finmarchicus and Oithona atlantica, gave evidence of an advection of Atlantic water masses into the area. It is concluded that the occurrence of new cohorts of Arctic copepods coincides with the onset of the phytoplankton bloom in the MIZ, and, that therefore, the spawning relies on stored energy.      

Northern glacial refugia for the pygmy shrew Sorex minutus in Europe revealed by phylogeographic analyses and species distribution modelling

The southern European peninsulas (Iberian, Italian and Balkan) are traditionally recognized as glacial refugia from where many species colonized central and northern Europe after the Last Glacial Maximum (LGM). However, evidence that some species had more northerly refugia is accumulating from phylogeographic, palaeontological and palynological studies, and more recently from species distribution modelling (SDM), but further studies are needed to test the idea of northern refugia in Europe. Here, we take a rarely implemented multidisciplinary approach to assess if the pygmy shrew Sorex minutus, a widespread Eurasian mammal species, had northern refugia during the LGM, and if these influenced its postglacial geographic distribution. First, we evaluated the phylogeographic and population expansion patterns using mtDNA sequence data from 123 pygmy shrews. Then, we used SDM to predict present and past (LGM) potential distributions using two different training data sets, two different algorithms (Maxent and GARP) and climate reconstructions for the LGM with two different general circulation models. An LGM distribution in the southern peninsulas was predicted by the SDM approaches, in line with the occurrence of lineages of S. minutus in these areas. The phylogeographic analyses also indicated a widespread and strictly northern‐central European lineage, not derived from southern peninsulas, and with a postglacial population expansion signature. This was consistent with the SDM predictions of suitable LGM conditions for S. minutus occurring across central and eastern Europe, from unglaciated parts of the British Isles to much of the eastern European Plain. Hence, S. minutus likely persisted in parts of central and eastern Europe during the LGM, from where it colonized other northern areas during the late‐glacial and postglacial periods. Our results provide new insights into the glacial and postglacial colonization history of the European mammal fauna, notably supporting glacial refugia further north than traditionally recognized.     

East Greenland and Barents Sea polar bears (Ursus maritimus): adaptive variation between two populations using skull morphometrics as an indicator of environmental and genetic differences

A morphometric study was conducted on four skull traits of 37 male and 18 female adult East Greenland polar bears (Ursus maritimus) collected 1892-1968, and on 54 male and 44 female adult Barents Sea polar bears collected 1950-1969. The aim was to compare differences in size and shape of the bear skulls using a multivariate approach, characterizing the variation between the two populations using morphometric traits as an indicator of environmental and genetic differences. Mixture analysis testing for geographic differentiation within each population revealed three clusters for Barents Sea males and three clusters for Barents Sea females. East Greenland consisted of one female and one male cluster. A principal component analysis (PCA) conducted on the clusters defined by the mixture analysis, showed that East Greenland and Barents Sea polar bear populations overlapped to a large degree, especially with regards to females. Multivariate analyses of variance (MANOVA) showed no significant differences in morphometric means between the two populations, but differences were detected between clusters from each respective geographic locality. To estimate the importance of genetics and environment in the morphometric differences between the bears, a PCA was performed on the covariance matrix derived from the skull measurements. Skull trait size (PC1) explained approx. 80% of the morphometric variation, whereas shape (PC2) defined approx. 15%, indicating some genetic differentiation. Hence, both environmental and genetic factors seem to have contributed to the observed skull differences between the two populations. Overall, results indicate that many Barents Sea polar bears are morphometrically similar to the East Greenland ones, suggesting an exchange of individuals between the two populations. Furthermore, a subpopulation structure in the Barents Sea population was also indicated from the present analyses, which should be considered with regards to future management decisions.     

Winter condition of marine plankton populations in Saanich Inlet,B.C., Canada. III. Meso-zooplankton

Seasonal changes in the species abundance of surface meso-zooplankton was monitored during spring, winter, and fall in Saanich Inlet, British Columbia. Small copepods were the dominant organisms during winter (Pseudocalanus minutus (Kröyer), Paracalanus parvus (Claus), Oithona helgolandica Claus, and Corycaeus anglicus Lubbock) while Calanus spp. were relatively rare. Pseudocalanus minutus was able to graze the flagellates which dominate winter phytoplankton populations but Calanus glacialis Jaschnov was not. There appeared to be active movement of small copepods towards the shallower depths where phytoplankton concentrations were highest. Pseudocalanus minutus was able to obtain its minimum energy requirement during winter by filter-feeding. Reproduction continued throughout the winter but at reduced rates. Growth was slowed at stages C-IV and C-V during winter with moulting to adult beginning immediately after a late winter increase in primary production.     

Pattern of morphological variation of Salicornia in north Europe

Among the few available morphological traits in the genus Salicornia L. (Amaranthaceae/Chenopodiaceae), most are extremely variable within species probably due to high levels of plasticity. In addition, identifying Salicornia taxa is further complicated by that these plants lose many of their diagnostic characters upon drying. Morphological studies of fresh (or liquid preserved) specimens is thus important in taxonomical studies. The objective of this study was a numerical morphological analyses of Salicornia populations in the Nordic countries and an adjacent Russian region with the aim to ascertain whether taxonomic division of this genus based on morphology is feasible. In all, 666 plants were collected for morphometric measurements from 31 localities and 52 populations or subpopulations of the North Sea coasts, Danish straits, Baltic Sea, the Norwegian Sea, Barents Sea, and the White Sea areas. For practical reasons, part of the samples was studied fresh, and part preserved in FAA pending measurements. Data were analyzed by principal component analysis (PCA) and hierarchical cluster analysis. The main taxonomical division was found between the diploid S. europaea s.l. and the tetraploid S. procumbens Sm., and was mainly based on fertile segment and flower morphology characteristics. Data also show ecological differences: diploids inhabit the upper part of salt marshes, whereas tetraploids grow in the hydrolittoral zone and are restricted to areas of regular tidal influence. It was not possible to make a morphological distinction between the two cryptic diploid species S. europaea s.s. and S. perennans Willd. in the present study. North Norwegian S. europaea clearly deviated from more southern populations, but taxonomical conclusions based only on morphology were avoided. In contrast, the division of S. procumbens into two geographical races/subspecies, the southern subsp. procumbens and the northern subsp. pojarkovae was supported.     

The mortality of the planktonic copepod <Emphasis Type="Italic">Oithona similis</Emphasis> Claus, 1866 (Copepoda: Cyclopoida) in the Barents and White Seas

The mortality rates of the copepodite IV-copepodite V and copepodite V-adult individuals pairs in the populations of one of the most common species of planktonic copepod, Oithona similis, were estimated for the first time in the Barents and White seas. The average parameters were 0.060 and 0.082/day, respectively, in the Barents Sea and 0.166 and 0.120/day in the White Sea. In the Barents Sea, the mortality rates of O. similis significantly increased with an increase in water temperature and in the White Sea a significant decrease occurred with an increase in salinity. It was concluded that the mortality rate of this species is determined first by abiotic factors and that biotic factors are of secondary significance.     

Scale morphometry allows discrimination of European sardine Sardina pilchardus and round sardinella Sardinella aurita and among their local populations

Landmark‐based geometric morphometric analysis revealed differences in scale shape between European sardine Sardina pilchardus and round sardinella Sardinella aurita as well as among the local populations of each species. Fish scale measurements from four different areas in the central and eastern Mediterranean Sea showed that the mean scale shape of the two species using landmark data could be differentiated with high certainty. Populations of S. aurita from the central and eastern Mediterranean Sea could be separated reliably (P < 0·001) with an average discrimination rate of 91%, whereas the average discrimination of the S. pilchardus populations was lower (80%), albeit still high.     

Interannual fluctuations of zooplankton in the Kola Section (Barents Sea) in relation to environmental factors

An analysis of interannual variations of zooplankton composition and biomass in the Kola Section (Barents Sea) in summer was conducted based on the data of 2003–2010. Maximum values of the mean water temperature and temperature anomaly were found in 2006 and in 2007. Variations in the zooplankton composition and relative biomass of common species were studied in relation to climatic factors. It is discussed which parameters may be used as indicators of climatic changes in the southern Barents Sea.     

mtDNA evidence for a local northern latitude Pleistocene refugium for the root vole (Microtus oeconomus,Arvicolinae, Rodentia) from Eastern Poland

We analysed the genetic structure of 33 populations of the root vole (tundra vole, Microtus oeconomus, Pallas, 1776) inhabiting their typical habitats, located at different distances from the southern boundary of the species’ range (52°14′–53°56′ N) in eastern Poland. We determined its phylogeographic pattern as well as the possible occurrence of a small, local high‐latitude refugium of this species in southern Poland, previously suggested in palaeontological studies. 908 bp of cytochrome b sequences were analysed from 439 root voles, and 21 mtDNA cytb haplotypes belonging to the Central European (CE) phylogroup were found. Haplotype diversity in the examined populations varied between 0 and 0.872 (mean: 0.425 ± 0.332), while nucleotide diversity ranged between 0 and 0.62% (mean: 0.235% ± 0.217). Within the CE phylogroup of M. oeconomus, we identified with high bootstrap support a newly separated group of M. oeconomus that evolved from CE, denoted CE‐PL S. This group is located in the southern and central part of eastern Poland and most likely diverged from phylogroup CE in a small, cryptic refugium situated in southern Poland, in the Kraków‐Cz?stochowa Upland and/or the Holy Cross Mountains during the LGM and Younger Dryas.     

Reproduction and larval ecology of the Arctic fish speciesArtediellus atlanticus (Cottidae)

 State of maturity, egg numbers, as well as gonadosomatic index (GSI), and relative fecundity were determined in 209 females of the cottid species Artediellus atlanticus. Specimens were caught by Agassiz and bottom trawls during two expeditions of RV “Polarstern” to the shelf off northeast Greenland (ARK VII/2; July/ August 1990) as well as to the Barents Sea and the shelf areas surrounding Svalbard (ARK VIII/2 – Arctic EPOS; June/July 1991). Analysis of the state of maturity showed that A. atlanticus spawns from late summer to autumn. Individuals from northern populations spawn later (November) than those from more southern locations (July to September). The total number of eggs (40–216) was small due to their large diameter and the small size of the fish. The mean GSI of females from the central Barents Sea (36.9±6.5%; n=24) was significantly higher (P<0.001) than the GSI of females caught off eastern Svalbard (18.7±4.0%; n=14), compared at stage IV of maturity. The mean relative fecundity was significantly higher (P<0.001) for females of the central Barents Sea (17.9±2.3; n=19) than for females caught on more northern stations east of Svalbard (6.9±1.8; n=17) and north of Svalbard (6.4±0.5; n=7). Individuals of A. atlanticus that were maintained at 0°C spawned in the aquaria, allowing observation of the development of their eggs and larvae for 1 year. The eggs needed more than 200 days to develop. The larvae hatched at a very advanced stage and were similar to the adults in appearance and behaviour. The larvae grew at a rate of 0.02 mm per day and showed a benthic mode of life. Received: 7 April 1995/Accepted: 30 July 1995     

Checklist of fauna found in zooplankton samples from the Barents Sea

We present a list of zooplankton taxa occurring in the Barents Sea based on our analysis of 360 samples from the upper 100 m of the water column as well as on reports from published sources. Moreover, we provide information on adult size, ecological and geographical distribution, habitat preference and frequency of occurrence of each taxon. The list encompasses a total of 374 species and higher taxa. Most are mesozooplankton, with Copepoda prevailing (153 species), and belong to the holoplankton. However, pseudoplankton, organisms only circumstantially occurring in the water column, also comprise a significant part of the fauna (86 taxa). The coastal zooplankton (264 neritic species) was richer than the fauna of the open sea. In our samples, the majority of the zooplankton taxa were rarely found (94 of 157 taxa, equivalent of 60%), 46 taxa (29%) were moderate and only 17 taxa (11%) were common (found in >80% of the samples). Among these, the copepods Calanus finmarchicus, C. glacialis, Oithona similis and Pseudocalanus minutus were most frequent.     

The translocated <Emphasis Type="Italic">Liza haematocheila</Emphasis> (Teleostei: Mugilidae) as a new host of four species of <Emphasis Type="Italic">Saturnius</Emphasis> Manter, 1969 (Digenea: Hemiuridae) within its invasive range in the Black Sea

This paper presents the first documented record of four species of Saturnius Manter, 1969 in Liza haematocheila (Temminck & Schlegel) in its invasive Pontic range. S. papernai Overstreet, 1977, S. dimitrovi Blasco-Costa, Pankov, Gibson, Balbuena, Raga, Sarabeev & Kostadinova, 2006, S. minutus Blasco-Costa, Pankov, Gibson, Balbuena, Raga, Sarabeev & Kostadinova, 2006 and Saturnius sp. are described and compared with existing data by means of multivariate morphometric analysis. The morphological and morphometric similarities between the specimens of Saturnius sp. from L. haematocheila and a small form of S. papernai from L. aurata indicate the possible existence of another, cryptic species. Although having acquired at least three species of Saturnius since its establishment in the Black Sea region, there is no evidence that a Pacific congener has been introduced with this fish. This is the first report of S. minutus from the Black Sea.     

Species composition,distribution, and specific features of feeding of Fish Larvae,and fry in the Sea of Okhotsk from October to December 2007

Ichthyoplankton of the Sea of Okhotsk from October to December 2007 comprised larvae and fry of eight fish species belonging to five families. The larvae of lord Hemilepidotus gilberti, white-spotted greenling Hexagrammos stelleri, and Atka mackerel Pleurogrammus monopterygius were the most widespread and numerous in the study period. Fish larvae from October to December 2007 were seined over the vast water area of the Sea of Okhotsk, maximum catches were made in waters of western Kamchatka. The food spectrum of larvae of five fish species (H. gilberti, Hexagrammos octogrammus, H. stelleri, P. monopterygius, and Bathymaster signatus) included approximately 20 plankters. Irrespective of species belonging, copepods Pseudocalanus minutus and Oithona similis, eggs and nauplii of copepods, as well as juveniles of pteropods were common food items for all fish. Larvae of all considered fish species in the Sea of Okhotsk fed mainly during the light hours of the day.     

Geographic variations of the mottled skate,Beringraja pulchra (Liu, 1932) (Rajidae) in the Yellow and East seas based on molecular and morphometric data

In order to prove the fisheries‐related hypothesis of the presence of two local populations of the mottled skate, Beringraja pulchra in the Yellow Sea (Sensu Jo et al., 2011 ), the geographic variations of 90 individuals (in molecule) and 129 individuals (in morphology) were investigated. The skates were collected from the middle Yellow Sea (Daechungdo), southern Yellow Sea (Heuksando), and the middle East Sea (Ulleungdo) using gill nets, bottom trawls and longlines. Comparing 471 base pairs of mitochondrial DNA cytochrome c oxidase subunit I (mtDNA COI) sequences, only three haplotypes (BR1–BR3) were found. The Daechungdo and Heuksando individuals displayed all three haplotypes, whereas the Ulleungdo individuals displayed a single haplotype (BR3). Pairwise fixation indices (FST) showed that the Daechungdo and Heuksando individuals were not genetically distinguishable (with a value of ?0.0344), whereas the Ulleungdo individuals were clearly distinct from both the Daechungdo and Heuksando individuals (with values of 0.6875 and 0.6871, respectively). Similar to the molecular result, a canonical discriminant analysis based on seven morphometric characters showed that the Ulleungdo individuals had positive values on the first axis, whereas those from the other two locations had negative values, slightly differentiating the two populations (East Sea population vs Yellow Sea population). This study is the first to identify two populations of mottled skate in the northwest Pacific.     

Geographical variability in life‐history traits of a midslope dogfish: the brier shark Deania calcea

Deania calcea (n = 420) were collected from the catch of deep‐water trawlers in the southern and eastern scalefish and shark fishery in southern Australia during the years 2008–2011. The total length (L_T) range varied between sexes, females being larger (n = 264; 280–1530 mm) than males (n = 156; 310–921 mm). The reproductive cycle in this population is non‐continuous and asynchronous. The estimated L_T at which 50% of males are mature is 807 mm and is 914 mm for females. Populations of D. calcea in higher latitudes appear to mature at a larger size than conspecifics in lower latitudes, in both the northern and southern hemispheres. Litters ranged from three to 10 embryos with a 1:1 sex ratio, but litter size does not increase with maternal L_T. Deania calcea shows geographical variability in its biological parameters and gathering information on life‐history traits of populations is vital to understand the trade‐offs made by this species in response to environmental conditions and to predict intraspecific spatial differences. Such information is a basis for specific spatial management to protect populations from excessive fishing.     

Climate-Driven Ichthyoplankton Drift Model Predicts Growth of Top Predator Young

Climate variability influences seabird population dynamics in several ways including access to prey near colonies during the critical chick-rearing period. This study addresses breeding success in a Barents Sea colony of common guillemots Uria aalge where trophic conditions vary according to changes in the northward transport of warm Atlantic Water. A drift model was used to simulate interannual variations in transport of cod Gadus morhua larvae along the Norwegian coast towards their nursery grounds in the Barents Sea. The results showed that the arrival of cod larvae from southern spawning grounds had a major effect on the size of common guillemot chicks at fledging. Furthermore, the fraction of larvae from the south was positively correlated to the inflow of Atlantic Water into the Barents Sea thus clearly demonstrating the mechanisms by which climate-driven bottom-up processes influence interannual variations in reproductive success in a marine top predator.     

Structure and specific features of formation of aggregations of deepwater redfish <Emphasis Type="Italic">Sebastes mentella</Emphasis> (Scorpaenidae) in the Norwegian Sea pelagial

Results of studies of the structure and specific features of formation of aggregations of deepwater redfish Sebastes mentella in the Norwegian Sea pelagial are provided. Data on the biological characteristics of S. mentella from different regions of the Norwegian Sea pelagial do not allow us to consider its aggregations as separate populations. On the basis of comparative analysis of the structure of aggregations in the Norwegian Sea and of population parameters and specific features of the life cycle of S. mentella in different parts of the Atlantic Ocean, its complex intraspecies organization at sites of overlapping of two largest populations—North Atlantic and Norwegian-Barents Sea-was established. The formation of pelagic aggregations in the water area of the Norwegian Sea occurs due to migration of maturing and mature individuals from the adjoining water areas. In the southern areas of the Norwegian Sea, dominant recruitment comes from the pelagial of the northeastern part of the Irminger Sea, which is promoted by the direction of streams of the North-Atlantic Current; it is not excluded either that fish can migrate to the southern part of the sea from the slopes of the Faeroes, Faeroes-Icelandic threshold, and the western coast of Norway. Migration to the northern areas of the sea is mainly performed by rapidly maturing fish from the rearing region from the western slopes of the Barents Sea and Spitsbergen Archipelago. The presence of seasonal migrations hinders the formation in the pelagial of perch isolated groups and promotes their migration.