Arctic Ocean Basin Research Articles

A synthesis of Jurassic and Early Cretaceous crustal evolution along the southern margin of the Arctic Alaska–Chukotka microplate and implications for defining tectonic boundaries active during opening of Arctic Ocean basins

A synthesis of Late Jurassic and Early Cretaceous collision-related metamorphic events in the Arctic Alaska–Chukotka microplate clarifies its likely movement history during opening of the Amerasian and Canada basins. Comprehensive tectonic reconstructions of basin opening have been problematic, in part, because of the large size of the microplate, uncertainties in the location and kinematics of structures bounding the microplate, and lack of information on its internal deformation history. Many reconstructions have treated Arctic Alaska and Chukotka as a single crustal entity largely on the basis of similarities in their Mesozoic structural trends and similar late Proterozoic and early Paleozoic histories. Others have located Chukotka near Siberia during the Triassic and Jurassic, on the basis of detrital zircon age populations, and suggested that it was Arctic Alaska alone that rotated. The Mesozoic metamorphic histories of Arctic Alaska and Chukotka can be used to test the validity of these two approaches. A synthesis of the distribution, character, and timing of metamorphic events reveals substantial differences in the histories of the southern margin of the microplate in Chukotka in comparison to Arctic Alaska and places specific limitations on tectonic reconstructions. During the Late Jurassic and earliest Cretaceous, the Arctic Alaska margin was subducted to the south, while the Chukotka margin was the upper plate of a north-dipping subduction zone or a zone of transpression. An early Aptian blueschist- and greenschist-facies belt records the most profound crustal thickening event in the evolution of the orogen. It may have resulted in thicknesses of 50–60 km and was likely the cause of flexural subsidence in the foredeep of the Brooks Range. This event involved northern Alaska and northeasternmost Chukotka; it did not involve central and western Chukotka. Arctic Alaska and Chukotka evolved separately until the Aptian thickening event, which was likely a result of the rotation of Arctic Alaska into central and western Chukotka. In northeastern Chukotka, the thickened rocks are separated from the relatively little thickened continental crust of the remainder of Chukotka by the oceanic rocks of the Kolyuchin-Mechigmen zone. The zone is a candidate for an Early Cretaceous suture that separated most of Chukotka from northeast Chukotka and Alaska. Albian patterns of magmatism, metamorphism, and deformation in Chukotka and the Seward Peninsula may represent an example of escape tectonics that developed in response to final amalgamation of Chukotka with Eurasia.

МОНГОЛЫН ЗАГАСНЫ АЙМГИЙН ЗАРИМ ТӨРӨЛ ЗҮЙЛИЙГ МОЛЕКУЛ-ФИЛОГЕНЕТИКИЙН АРГААР СУДАЛСАН ДҮНГЭЭС

The Joint Mongolian-Russian Complex Biological Expedition is the biggest biological expedition in iterms of Water ecosystems of Mongolia. Over 40 years, large - scale integrated research has been analysis of natural and antropogenic processes and basic principles of rational exploitation. The aim is to fulfill complex hydrobiological, ichthyological and hydrological estimation of water resources state and propose measures for their protectionInterrelation of global and local geo-climatic changes in territory of Mongolia in Cenozoic Era with evolution of endemic fishes of genera Oreoleuciscus is analysed. It is shown , that all basic stages of geo-climatic transformation directly defined occurrence, formation of species, morpho-ecological specialization and formation of geographic areas of species and their population organization.Evolutionary and population characteristics of the Altai osmans are given on the basis of genetically analysis of locuses mtDNA and the nuclear locuses coding isoenzymes.According to recent findings and investigations fauna of Lampreys and fishes of Mongolia consist of about 75 species of 14 families and 2 orders. 11 new species of fish, including one new invader bream (Abramis brama) were noted in the country waters last 15 years. According to new results two species of the Altai osmans (Oreoleuciscus angusticephalus, O.dsapchynensis) and one species of graylings (Thymallus arcticus) are excluded from the list of fish fauna of Mongolia. Recently Almai osmans were found not only in the waters of the Central-Asian closed basin, but also in rivers and small lakes of the Selenga River basin (Dgebuadze, Dulmaa, Munkhbayar 2003; Dulmaa A.,Munkhbayar Kh.Nakagawa M.,2004).Esseantial climate change and increasing of human impact transformed Mongolian fish population during last 40 years. As a result bias on ratio of ecological guilds, pathology number increasing, local diversity declining, and changes in species distribution, rate of growth and fecundity of many species of fish are observed. One of the main factors, influencing on fish populations, is gold mining in the rivers Arctic Ocean basin. In new conditions more attention demand both commercially important species as taimen, lenok, Baikal and Amur graylings, Amur carp, goldfish, Amur catfish, Amur and northern pikes, minnows, burbot, dace, and endangered and endemic species as Altai osman, Mongolian upper Enisey and Kosogol graylings, stone loaches and sculpin.Anthropogenic load on the water bodies of the Central-Asian closed basin is connected, first of all, with the constraction of hydraulic structures (dams in the basin of the Kobdo and Dzavkhan rivers), increase of pullution, and intensification of fishery. Evaluation of modern condition of water ecosystems and fish population parateters of this basin remains the main purpose of research for the years immediately ahead.

Climate change and response in bottom water circulation and sediment provenance in the Central Arctic Ocean since the Last Glacial

In this study, Arctic Ocean patterns of deep water circulation and sediment provenance during the Last Glacial (LG) were compared with the recent situation by investigating the Nd and Sr isotopic composition (143Nd/144Nd, expressed as εNd, 87Sr/86Sr) of the leachable and lithogenic sediment fractions as well as the elemental composition (Mn, Ca, Mg, total inorganic carbon (TIC)) on a spatially extended scale encompassing 11 sediment cores from several Arctic Ocean basins and ridges.The leachable, authigenic signature of the surface sediments implies a North Atlantic deep water source and a late Holocene circulation regime that leads to well-mixed, mostly uniform, εNd values of −10.9 to −10.3. Sediments from the LG have overall more variable authigenic εNd values (−13.9 to −7.4). Lower values specifically occur in the Amerasian and Amundsen Basins, documenting an enhanced flow of deep waters from the Makarov Basin to the Amundsen Basin probably via the Lomonosov Ridge intra-basin.In terms of detrital provenance areas, the lithogenic material deposited at the core locations cannot be unambiguously assigned to distinct source areas based on its radiogenic isotope composition, but represents a diverse mixture. Nevertheless, the Nd and Sr isotope signatures of surface sediments from the Amerasian Basin are dominated by western Arctic sources (εNd=−12.8 to −11.0; 87Sr/86Sr=0.7214 to 0.7251), while Eurasian Basin surface sediments are dominated by Eurasian sources (εNd=−10.9 to −9.7, 87Sr/86Sr=0.7178 to 0.7299), which is in agreement with previous studies. Bulk element patterns (Ca, Mg, TIC) of the studied sediments support these differences in provenance. The LG samples show the same trends with low εNd (−16.1 to −13.7) and high 87Sr/86Sr (0.7294) in the Canada Basin, and higher εNd (−12.6 to −8.8) and lower 87Sr/86Sr (0.7154 to 0.7249) in the Eurasian Basin sediments. However, LG samples have mostly lower and more heterogenous εNd and 87Sr/86Sr values than the surface samples.Our geochemical study shows that the overall circulation pattern of the deep water masses during the LG was locally influenced by brine formation but was generally similar to today. The isotopic composition of the lithogenic material from the LG is different from modern times, presumably due to shorter transport pathways of lithogenic material to the Arctic Ocean because of a lower sea level and exposed shelves during the LG. Nevertheless, the lithogenic fraction still represents a mixture from several sources.

Concentration maxima of volatile organic iodine compounds in the bottom layer water and the cold, dense water over the Chukchi Sea in the western Arctic Ocean: a possibility of production related to the degradation of organic matter

Abstract. We conducted a shipboard observation over the Chukchi Sea and the Canada Basin in the western Arctic Ocean in September and October 2012 to obtain vertical distributions of four volatile organic iodine compounds (VOIs) in seawater. The VOIs observed in this study were iodomethane (CH3I), iodoethane (C2H5I), diiodomethane (CH2I2), and chloroiodomethane (CH2ClI). Maximum concentrations of the four VOIs were found in the bottom layer water over the Chukchi Sea shelf, in which layer the maximum concentration of ammonium (NH4+) also occurred. A significant correlation was observed between C2H5I and NH4+ (correlation coefficient R = 0.93, P < 0.01, n = 64) and between CH3I and NH4+ (R= 0.77, P < 0.01, n = 64), suggesting that the production of these VOIs increased with the degradation of organic matter. Over the northern Chukchi Sea shelf–slope area, concentration maxima of CHI2, CH2ClI, and CH3I were found in the subsurface cold, dense water (CDW). A large nitrogen deficit (N deficit = NH4++ NO3−+ NO2−−16PO43−) occurred simultaneously in this water, suggesting the production of the three VOIs in the sediment or the bottom layer water over the shelf, probably in association with the degradation of organic matter. We conclude that VOI production over the Chukchi Sea shelf can be largely attributed to the degradation of organic matter that is produced in the highly productive shelf water. High concentrations of CH2ClI were also found in the Alaskan Coastal Water (ACW) from the Bering Strait to the surface of the northern Chukchi slope. The VOIs that originated at the Chukchi Sea shelf are expected to be laterally transported to the Arctic Ocean basin through the CDW and the surface ACW.

Seasonal variation of fluxes of dispersed sedimentary matter in the White Sea (Arctic ocean basin)

The monthly and seasonal quantity estimates of vertical fluxes of sedimentary matter from the White Sea performed during studies are the basis for the direct calculations of incoming chemical components, minerals, and various pollutants to the surface layer of bottom sediments. The White Sea, one of six Russian Arctic seas, may be considered as a megapolygon for further modern research using the new regularities of arctic sedimentogenesis established. This study focuses on the development of new technologies for complex studies of marine water areas using underwater sedimentation observatories, regular observations onboard vessels, and satellite oceanological data. The first priority task is year-round monitoring along the Northern Sea Route.

Predictions replaced by facts: a keystone species' behavioural responses to declining arctic sea-ice.

Since the first documentation of climate-warming induced declines in arctic sea-ice, predictions have been made regarding the expected negative consequences for endemic marine mammals. But, several decades later, little hard evidence exists regarding the responses of these animals to the ongoing environmental changes. Herein, we report the first empirical evidence of a dramatic shift in movement patterns and foraging behaviour of the arctic endemic ringed seal (Pusa hispida), before and after a major collapse in sea-ice in Svalbard, Norway. Among other changes to the ice-regime, this collapse shifted the summer position of the marginal ice zone from over the continental shelf, northward to the deep Arctic Ocean Basin. Following this change, which is thought to be a 'tipping point', subadult ringed seals swam greater distances, showed less area-restricted search behaviour, dived for longer periods, exhibited shorter surface intervals, rested less on sea-ice and did less diving directly beneath the ice during post-moulting foraging excursions. In combination, these behavioural changes suggest increased foraging effort and thus also likely increases in the energetic costs of finding food. Continued declines in sea-ice are likely to result in distributional changes, range reductions and population declines in this keystone arctic species.

Flood zone biogeochemistry of the Ob River middle course

The flood zone of the Ob River, the largest (in watershed area) river of the Arctic Ocean basin, is tens of km wide and, after the Amazon's Varzea, is the world's second largest flooding territory. To better understand the biogeochemistry of the Ob River and adjacent surface waters, we studied, in May and July 2014, the dissolved and colloidal organic carbon and trace metals in small rivers, lakes, and flooded water bodies connected and disconnected with the mainstream as well as the Ob River itself. All major and trace elements were distributed among two major categories depending on their pattern of dependence on the dissolved organic carbon (DOC) concentration. Dissolved inorganic carbon (DIC), Na, Mg, Ca, sulfate, Sr, Mo, Sb and U exhibited a general decrease in concentration with the increase of the [DOC]. The lowest concentration of these elements was observed in DOC-rich humic, acidic (4.9 ≤ pH ≤ 6.1) upland lakes fed by surrounding bogs. These elements marked the influence of underground feeding in July during summer baseflow, which was most visible in flood lakes in the Ob riparian zone and the Ob River itself. In May, the flood lakes were statistically similar to the Ob River. The elevated concentration of DOC (up to 60 mg/L) in the upland lakes was not correlated with groundwater-related elements, suggesting a lack of significant groundwater feeding in these lakes. In contrast, insoluble, usually low mobile elements (Al, Fe, other trivalent hydrolysates, Ti, Zr, Hf) and some metals (Cr, Zn, Ni, Pb) demonstrated a steady increase in concentration with increasing DOC, with the lowest values observed in the Ob River and the highest values observed in small tributaries and organic-rich upland lakes in July. It follows that these elements are limited by their main carriers – organic and organo-ferric colloids, rather than by the availability of the source, peat and mineral soil or plant litter. While for the majority of non-colloidal, groundwater-fed elements with high mobility (DIC, Na, Mg, Ca, K, Sr…) the small tributaries can be used as representatives of the Ob main stream, this is not the case for low mobility “insoluble” elements, such as Fe, Al, trivalent and tetravalent hydrolysates, and metal micronutrients (Cu, Zn, and Mn). The low soluble elements and divalent metals exhibited a much lower concentration in the river mainstream compared to that in the flood lakes, upland lakes and small rivers. This difference is significantly more pronounced in the baseflow in July compared to the spring flood in May. Presumably, autochthonous processes, such as the photo-oxidation and bio-oxidation of organo-ferric colloids and phytoplankton uptake are capable decreasing the concentration of these elements in the river mainstream.

A tale of two basins: An integrated physical and biological perspective of the deep Arctic Ocean

A tale of two basins: An integrated physical and biological perspective of the deep Arctic Ocean

Genetic variation of the mtDNA cyt b locus in graylings (Thymalus sp.: Thymalidae, Pisces) introduced into the Baydrag Gol River of the Valley of Lakes basin (Mongolia)

Based on sequence variation of the mtDNA cyt b gene, an analysis of graylings introduced from the Arctic Ocean basin (Selenga River basin) into one of the rivers of Central Asian inland basin (Baydrag Goal River of the Valley of Lakes basin) was carried out. Morphological and molecular genetic identification was performed, and it was established that the introduced species corresponded to the Baikal grayling. The relationships among Central Asian grayling species are discussed.

Sensitivity study of subgrid scale ocean mixing under sea ice using a two-column ocean grid in climate model CESM

Brine drainage from sea ice formation plays a critical role in ocean mixing and seasonal variations of halocline in polar oceans. The horizontal scale of brine drainage and its induced convection is much smaller than a climate model grid and a model tends to produce false ocean mixing when brine drainage is averaged over a grid cell. A two-column ocean grid (TCOG) scheme was implemented in the Community Earth System Model (CESM) using coupled sea ice-ocean model setting to explicitly solve the different vertical mixing in the two sub-columns of one model grid with and without brine rejection. The fraction of grid with brine rejection was tested to be equal to the lead fraction or a small constant number in a series of sensitivity model runs forced by the same atmospheric data from 1978 to 2009. The model results were compared to observations from 29 ice tethered profilers (ITP) in the Arctic Ocean Basin from 2004 to 2009. Compared with the control run using a regular ocean grid, the TCOG simulations showed consistent reduction of model errors in salinity and mixed layer depth (MLD). The model using a small constant fraction grid for brine rejection was found to produce the best model comparison with observations, indicating that the horizontal scale of the brine drainage is very small compared to the sea ice cover and even smaller than the lead fraction. Comparable to models using brine rejection parameterization schemes, TCOG achieved more improvements in salinity but similar in MLD.

Deep water masses and sediments are main compartments for polychlorinated biphenyls in the Arctic Ocean.

There is a wealth of studies of polychlorinated biphenyls (PCB) in surface water and biota of the Arctic Ocean. Still, there are no observation-based assessments of PCB distribution and inventories in and between the major Arctic Ocean compartments. Here, the first water column distribution of PCBs in the central Arctic Ocean basins (Nansen, Amundsen, and Makarov) is presented, demonstrating nutrient-like vertical profiles with 5-10 times higher concentrations in the intermediate and deep water masses than in surface waters. The consistent vertical profiles in all three Arctic Ocean basins likely reflect buildup of PCBs transported from the shelf seas and from dissolution and/or mineralization of settling particles. Combined with measurement data on PCBs in other Arctic Ocean compartments collected over the past decade, the total Arctic Ocean inventory of ∑7PCB was estimated to 182 ± 40 t (±1 standard error of the mean), with sediments (144 ± 40 t), intermediate (5 ± 1 t) and deep water masses (30 ± 2 t) storing 98% of the PCBs in the Arctic Ocean. Further, we used hydrographic and carbon cycle parametrizations to assess the main pathways of PCBs into and out of the Arctic Ocean during the 20th century. River discharge appeared to be the major pathway for PCBs into the Arctic Ocean with 115 ± 11 t, followed by ocean currents (52 ± 17 t) and net atmospheric deposition (30 ± 28 t). Ocean currents provided the only important pathway out of the Arctic Ocean, with an estimated cumulative flux of 22 ± 10 t. The observation-based inventory of ∑7PCB of 182 ± 40 t is consistent with the contemporary inventory based on cumulative fluxes for ∑7PCB of 173 ± 36 t. Information on the concentration and distribution of PCBs in the deeper compartments of the Arctic Ocean improves our understanding of the large-scale fate of POPs in the Arctic and may also provide a means to test and improve models used to assess the fate of organic pollutants in the Arctic.

Arctic Ocean basin liquid freshwater storage trend 1992–2012

Freshwater in the Arctic Ocean plays an important role in the regional ocean circulation, sea ice, and global climate. From salinity observed by a variety of platforms, we are able, for the first time, to estimate a statistically reliable liquid freshwater trend from monthly gridded fields over all upper Arctic Ocean basins. From 1992 to 2012 this trend was 600±300 km3 yr−1. A numerical model agrees very well with the observed freshwater changes. A decrease in salinity made up about two thirds of the freshwater trend and a thickening of the upper layer up to one third. The Arctic Ocean Oscillation index, a measure for the regional wind stress curl, correlated well with our freshwater time series. No clear relation to Arctic Oscillation or Arctic Dipole indices could be found. Following other observational studies, an increased Bering Strait freshwater import to the Arctic Ocean, a decreased Davis Strait export, and enhanced net sea ice melt could have played an important role in the freshwater trend we observed.

Distribution of Ephemeroptera, Plecoptera, and Trichoptera assemblages in relation to environmental variables in headwater streams of Mongolia

Effects of stream environmental variables on the distribution and abundance of Ephemeroptera, Plecoptera and Trichoptera (EPT) assemblages in the headwaters of rivers and streams of Mongolia were investigated in this broad scale survey aimed to provide a baseline for future research and management of the country’s aquatic ecosystems. The survey was carried out in the first-, second- and third-order streams of 80 rivers selected from the three main watersheds of Mongolia, namely the Arctic Ocean Basin (AOB), Pacific Ocean Basin (POB) and Central Asian Internal Basin (CAIB). We sampled larvae of EPT by kick and d-nets from the headwater sites during summers of 2007–2009. Chemical and hydrological variables of the sites were measured, and habitat of those sites was assessed. We recorded 89 taxa belonging to 34 families of EPT orders during the survey. The family Baetidae (Ephemeroptera) was the dominant taxon among all sites. Taxon richness was higher in the POB and AOB than CAIB, while total EPT abundance was higher in the CAIB. Significant differences in the community variables, such as taxon richness, Shannon’s diversity index and evenness of EPT assemblages were observed among the basins. Results of canonical correspondence analysis suggested that altitude, dissolved oxygen, order and width of streams were the most important factors explaining the variability in EPT larval distribution in the headwater streams in Mongolia.

Precise determination of seawater calcium using isotope dilution inductively coupled plasma mass spectrometry

We describe a method for rapid, precise and accurate determination of calcium ion (Ca(2+)) concentration in seawater using isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS). A 10 μL aliquot of seawater was spiked with an appropriate (43)Ca enriched solution for (44)Ca/(43)Ca ID-ICP-MS analyses, using an Element XR (Thermo Fisher Scientific), operated at low resolution in E-scan acquisition mode. A standard-sample bracketing technique was applied to correct for potential mass discrimination and ratio drift at every 5 samples. A precision of better than 0.05% for within-run and 0.10% for duplicate measurements of the IAPSO seawater standard was achieved using 10 μL solutions with a measuring time less than 3 minutes. Depth profiles of seawater samples collected from the Arctic Ocean basin were processed and compared with results obtained by the classic ethylene glycol tetra-acetic acid (EGTA) titration. Our new ID-ICP-MS data agreed closely with the conventional EGTA data, with the latter consistently displaying 1.5% excess Ca(2+) values, possibly due to a contribution of interference from Mg(2+) and Sr(2+) in the EGTA titration. The newly obtained Sr/Ca profiles reveal sensitive water mass mixing in the upper oceanic column to reflect ice melting in the Arctic region. This novel technique provides a tool for seawater Ca(2+) determination with small sample size, high throughput, excellent internal precision and external reproducibility.

U–Pb geochronology of Cretaceous magmatism on Svalbard and Franz Josef Land, Barents Sea Large Igneous Province

AbstractThe opening of the Arctic oceanic basins in the Mesozoic and Cenozoic proceeded in steps, with episodes of magmatism and sedimentation marking specific stages in this development. In addition to the stratigraphic record provided by sediments and fossils, the intrusive and extrusive rocks yield important information on this evolution. This study has determined the ages of mafic sills and a felsic tuff in Svalbard and Franz Josef Land using the isotope dilution thermal ionization mass spectrometry (ID-TIMS) U–Pb method on zircon, baddeleyite, titanite and rutile. The results indicate crystallization of the Diabasodden sill at 124.5 ± 0.2 Ma and the Linnévatn sill at 124.7 ± 0.3 Ma, the latter also containing slightly younger secondary titanite with an age of 123.9 ± 0.3 Ma. A bentonite in the Helvetiafjellet Formation, also on Svalbard, has an age of 123.3 ± 0.2 Ma. Zircon in mafic sills intersected by drill cores in Franz Josef Land indicate an age of 122.7 Ma for a thick sill on Severnaya Island and a single grain age of ≥122.2 ± 1.1 Ma for a thinner sill on Nagurskaya Island. These data emphasize the importance and relatively short-lived nature of the Cretaceous magmatic event in the region.

210Pb and 137Cs in margin sediments of the Arctic Ocean: Controls on boundary scavenging

210Pb and 137Cs were measured in 25 sediment cores collected during the International Polar Year from a transect spanning the North American Arctic margin, from the North Bering Sea to Baffin Bay/Davis Strait. Profiles and inventories of the radioisotopes were used to determine sediment mixing and accumulation at each site and to assess the intensity of scavenging and burial. Sediment accumulation rates derived from 210Pb and validated using 137Cs are between ≤0.04 and 0.23 g cm−2 yr−1. 210Pb cannot be used to derive sedimentation rates for vigorously biomixed sediments from the North Bering‐Chukchi shelf. Elevated 137Cs activities and inventories in recently deposited sediments imply delayed inputs of particle‐associated 137Cs to the sediments, likely transported from the watershed to the coast and subsequently redistributed to shelf/slope sediments. Inventories of 210Pbex in all cores meet or exceed the estimated supply of 210Pbex from atmospheric deposition and decay of 226Ra in the water column. This implies that in contrast to the deep Arctic Ocean basin, there is a sufficient supply of suspended particulates along the North American Arctic margin to scavenge the supply of 210Pbex. 210Pbex inventories in sediments are up to 21‐fold greater than the in situ supply at some sites. Large inventories of 210Pbex in sediments along the North Bering‐Chukchi shelf result primarily from focusing, while those along the north Chukchi slope (Barrow Canyon) and in Baffin Bay/Davis Strait reflect strong boundary scavenging, likely supported by lateral exchanges with deep/interior Atlantic‐origin waters.

Remote climate forcing of decadal‐scale regime shifts in Northwest Atlantic shelf ecosystems

Decadal‐scale regime shifts in Northwest Atlantic shelf ecosystems can be remotely forced by climate‐associated atmosphere‐ocean interactions in the North Atlantic and Arctic Ocean Basins. This remote climate forcing is mediated primarily by basin‐ and hemispheric‐scale changes in ocean circulation. We review and synthesize results from process‐oriented field studies and retrospective analyses of time‐series data to document the linkages between climate, ocean circulation, and ecosystem dynamics. Bottom‐up forcing associated with climate plays a prominent role in the dynamics of these ecosystems, comparable in importance to that of top‐down forcing associated with commercial fishing. A broad perspective, one encompassing the effects of basin‐ and hemispheric‐scale climate processes on marine ecosystems, will be critical to the sustainable management of marine living resources in the Northwest Atlantic.

Current status and catch of Siberian taimen (Hucho taimen) in the lower Amur River

Siberian taimen, Hucho taimen (Pall.), is a common species in the Khabarovsk region, and it occurs nearly throughout the Amur River watershed (Pacific Ocean basin) and the upper tributaries of the Lena River (Arctic Ocean basin). Taimen only inhabits two coastal rivers - the Uda and Tugur. Commercial fishing for taimen has never been prohibited in the lower and central Amur River drainage basin. This species is a valuable food fish, and is especially attractive to recreational and sport fishing. Before the Second World War, taimen catches in the lower part of the Amur River were as high as 20 tons per year, but during the war, all bans on fishing were lifted, and the taimen catch increased to 100 tons per year. The period that is probably the most revealing for estimating the taimen population in the lower Amur River watershed is 1946-1969 when harvests ranged from 15 to 35 tons. In the 1970s, taimen catches declined probably because water temperatures in the Amur River increased. In the 1980-2005 period, illegal fishing increased, commercial fishing decreased, and catch statistics became unreliable. The best taimen rivers now are located in unpopulated areas in the Amur River drainage basin and inaccessible upper regions of the Lena River drainage basin.

Phylogeography of Altai osmans fishes (Oreoleuciscus sp., Cyprinidae, Pisces) inferred from nucleotide variation of the mitochondrial DNA cytochrome b gene

In this study, analyses based on cytochrome b gene (Cyt-b) mtDNA sequences were undertaken to clarify phylogenetic and phylogeographical relationships among populations Oreoleuciscus sp. (Pisces: Cyprinidae) from Western Mongolia. Two major clusters, designated clusters A and B, and minor clusters were discriminated. Cluster A comprised specimens of Oreoleuciscus from the Valley of Lakes. The cluster B consists of two subclusters; one of them (B1) including populations Oreoleuciscus of the Hollow of the Big Lakes and lakes Big Altai Range. Second subclusters (B2) combines specimens of Oreoleuciscus from Hollow of the Lake Uvs, some isolated lakes of the North-Western Khangay and waterbodies of the Arctic Ocean Basin (Selenge and Orchon basins). On the basis of estimations of sizes genetic and time of a divergence of the revealed genetikal-geographical groups existence of three allopatric species of the within genera Oreoleuciscus is proved.

Life at the top of the greenhouse Eocene world--A review of the Eocene flora and vertebrate fauna from Canada's High Arctic

Early–middle Eocene (ca. 53–38 Ma) sediments of the Eureka Sound Group in Canada’s Arctic Archipelago preserve evidence of lush mixed conifer-broadleaf rain forests, inhabited at times by alligators, turtles, and diverse mammals, including primates, tapirs, brontotheres, and hippo-like Coryphodon. This biota reflects a greenhouse world, offering a climatic and ecologic deep time analog of a mild ice-free Arctic that may be our best means to predict what is in store for the future Arctic if current climate change goes unchecked. In our review of the early–middle Eocene Arctic flora and vertebrate fauna, we place the Arctic fossil localities in historic, geographic, and stratigraphic context, and we provide an integrated synthesis and discussion of the paleobiology and paleoecology of these Eocene Arctic forests and their vertebrate inhabitants. The abundance and diversity of tapirs and plagiomenids (both rare elements in midlatitude faunas), and the absence of artiodactyls, early horses, and the hyopsodontid “condylarth” Hyopsodus (well represented at midlatitude localities) are peculiar to the Eocene Arctic. The Eocene Arctic macrofloras reveal a forested landscape analogous to the swamp-cypress and broadleaf floodplain forests of the modern southeastern United States. Multiple climate proxies indicate a mild temperate early–middle Eocene Arctic with winter temperatures at or just above freezing and summer temperatures of 20 °C (or higher), and high precipitation. At times, this high precipitation resulted in freshwater discharge into a nearly enclosed Arctic Ocean basin, sufficient to cause surface freshening of the Arctic Ocean, supporting mats of the floating fern Azolla . Fluctuating Arctic Ocean sea level due to freshwater inputs as well as tectonics produced temporary land bridges, allowing land plants and animals to disperse between North America and both Europe and Asia.