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Evaluation of the toxicity of fluorine in Antarctic krill on soft tissues of Wistar rats
Get PDFAntarctic krill are a potential food source for humans and animals, but krill are known to contain high levels of fluorine (F). In this study, we investigated the toxicity of F in Antarctic krill using Wistar rats. There were three experimental groups: The control group were fed a basal diet, the krill treatment group were fed the same basal diet mixed with krill powder (150 mg∙kg-1 F), and the sodium fluoride (NaF) treatment group were fed the basal diet with added NaF (150 mg∙kg-1 F). General toxicity indicators including body weight and food intake were measured during the experiment. After three months the rats were dissected and tissue samples were collected from the liver, kidney, spleen, brain, and testis. Morphological changes in the cells of these tissues were assessed using HE staining. There were no significant differences in the body weight, the food intake, or the viscera coefficients among the three groups. In both treatment groups some pathological changes were observed in all soft tissue samples except the testis, although there were fewer and less severe pathological changes in the krill treatment group than in the NaF treatment group. The results showed that the toxicity of F in Antarctic krill was lower than for an equivalent amount of F in NaF, but it was still toxic to rats consuming large quantities of krill. The findings of this study highlight the need for further investigation into potential F toxicity if krill is to be used for human consumption
Polar Law Textbook II
Get PDF“Developments in the Arctic and Antarctica continue to be the subject of growing public interest and academic, political, scientific, and media discourse. The global magnitude of the changes that are currently taking place in the Polar Regions, also influence legal developments. Furthermore, the growing importance of both the Arctic and the Antarctica in various areas of global, regional, national and sub-national development requires further inquiry into the role of law in dealing with many of the current and emerging issues relevant to both Poles. Although law is not a panacea for all issues, it has its own role to play in dealing with many of them.” A broad overview of Polar law issues was presented in the pioneering Polar Law Textbook, N. Loukacheva ed. Copenhagen: Nordic Council of Ministers, Tema Nord 538: 2010 (www.norden.org).This textbook represents the outcome of a cooperative process between an international group of well-known experts in the area of Polar law and related studies. Polar Law Textbook II further draws upon Polar law as an evolving and developing field of studies which is gaining increasing recognition and intersects with many other areas in the social sciences and humanities. It explores a variety of legal issues in the Arctic and Antarctica (i.e., questions of human rights law, environmental law, law of the sea, continental shelf, climate change, energy law, resources, indigenous peoples’ rights, etc.,) but also covers the relevant aspects of geopolitics, security, governance, search and rescue, biodiversity, devolution, institutions (e.g., the Arctic Council) and political developments
The Super Dual Auroral Radar Network (SuperDARN): An overview of its development and science
Get PDFThe Super Dual Auroral Radar Network (SuperDARN) is a network of HF coherent scatter radars. At the end of 2012 there were 31 operational radars of which 22 were in the northern hemisphere and 9 in the southern hemisphere. The radars are operated by 17 different research groups from 11 different countries. In this paper we give an overview of the network and its development over the last twenty years, concentrating on the nature of the collaboration. We describe the data parameters that are available, radar operational modes, and the structure of the SuperDARN collaboration. A brief, “light touch” review is also given of the science achieved with the network. Finally we give a brief look to future science directions
DNA barcoding of Antarctic marine zooplankton for species identification and recognition
Get PDFPolar zooplankton are particularly sensitive to climate change, and have been used as rapid-responders to indicate climate-induced changes in the fragile Antarctic ecosystem. DNA barcoding provides an alternative approach for rapid zooplankton species identification. Ninety-four specimens belonging to 32 Antarctic zooplankton species were barcoded to construct a comprehensive reference library. An 830 to 1 050 base-pair region of the mitochondrial cytochrome c oxidase subunit I (mtCOI) gene was obtained as DNA barcodes. The intraspecific variation of the gene ranged from 0 to 2.6% (p-distance), with an average of 0.67% (SD=0.67%). The distance between species within the same genera ranged from 0.1% (Calanus) to 29.3%, with an average of 15.3% (SD=8.4%). The morphological and genetic similarities between Calanus propinquus and C. simillimus raise new questions about the taxonomic status of C. simillimus. With the exception of the two Calanus species, the intraspecific genetic divergence was much smaller than the interspecific divergence among congeneric species, confirming the existence of a barcode gap for Antarctic zooplankton. In addition, species other than Calanus sp. formed a monophyletic group. Therefore, we have confirmed DNA barcoding as an accurate and efficient approach for zooplankton identification in the Antarctic area (except for Hydromedusa, Tunicata, and other gelatinous zooplankton). Indicator vector analysis further confirmed this conclusion. The new primer sets issued here may facilitate the study of Antarctic marine zooplankton species composition by environmental metagenetic analysis
The substorm current wedge and midnight sector partial ring current near substorm onset: A synthesis based on a magnetotail magnetic field geometry model
Get PDFThe Substorm Current Wedge (SCW) occurrence in the late growth and onset phases of substorms was proposed as the current system which disrupts cross-tail current by diverting it to the ionosphere. The closure current for the SCW originally was suggested to be the strong westward auroral electrojet (WEJ). However, the SCW-WEJ system has no viable generator current. Similarly, the asymmetric or Partial Ring Current (PRC) increases in strength during the growth phase, and is sometimes associated with an enhanced Region 2 field-aligned current (FAC) closing to the ionosphere, but specifics of that closure have been lacking. Here we present a unifying picture which includes the SCW post- and pre-midnight (AM and PM, respectively) currents and a generator current in the midnight portion of the PRC system, with these currents based upon a model of the nightside magnetotail magnetic geometry. That geometry consists of open north and south lobe regions surrounding a plasmasheet with two types of closed field line regions-stretched lines in the central part of the plasmasheet (SPS) and dipolar lines (DPS) between the low latitude boundary layer (LLBL) regions and the SPS. There is also an important plasmasheet transition region (TPS) in which the dipolar field near the plasmapause gradually transforms to stretched lines near the earthward edge of the SPS, and in which the midnight part of the PRC flows. We propose that our proposed near-onset current system consists of a central current which becomes part of the midnight sector PRC and which is the generator, to which are linked two three-part current systems, one on the dawnside and one on the duskside. The three-part systems consist of up and down FACs closing as Pedersen currents in the ionosphere. These 3-part systems are not activated until near-onset is reached, because of a lack of ionospheric conductivity in the appropriate locations where the Pedersen current closure occurs. The initial downward FAC of the 3-part dawnside system and the final upward FAC of the 3-part duskside system correspond to the AM and PM current segments, respectively, of the originally proposed SCW
Progress of Chinese research in physical oceanography of the Southern Ocean
Get PDFOceanographic surveying has been one of the key missions of the Chinese National Antarctic Research Expedition since 1984. Using the field data obtained in these surveys and the results from remote sensing and numerical models, Chinese physical oceanographers have investigated the water masses, fronts and circulation patterns in the Southern Ocean. The results of nearly 30 years of research are summarized in this paper. Most oceanographic observations by Chinese researchers have been conducted in Prydz Bay and the adjacent seas. CTD (Conductivity Temperature and Depth) data, collected during the past 20 years, have been applied to study several features of the water masses in this region: The spatial variation of warm summer surface water, the northward extension of shelf water, the flow of ice shelf water from the cavity beneath the Amery Ice Shelf, the upwelling of the Circumpolar Deep Water, and the formation of the Antarctic Bottom Water. The circulation and its dynamic factors have been analyzed with dynamic heights calculated from CTD data as well as by numerical models. The structure and strength of the fronts in the southeast Indian Ocean and the Drake Passage were investigated with underway XBT/XCTD (Expendable Bathythermograph/ Expendable CTD) and ADCP (Acoustic Doppler Current Profiler) data. Their interannual variations have been determined and the factors of influence, especially the atmospheric forcing and mesoscale oceanic processes, were studied using remote sensing data. The dynamic mechanism of the Antarctic Circumpolar Current (ACC) was analyzed by theoretical models. The transport and pattern of the ACC have been well reproduced by coupled sea ice-ocean models. Additional details of ACC variability were identified based on satellite altimeter data. The response of the ACC to climate change was studied using reanalysis data. Prospects for future research are presented at the end of this paper
Diatom distribution of surface sediment in the Bering Sea and Chukchi Sea
Get PDFDiatoms from surface sediment samples in the Bering and Chukchi seas were analyzed to reveal the distribution patterns and their relationship with the ocean environment. A low abundance was found to the north of the Arctic Sea Ice Minimum (ASIMin), indicating that diatom growth is strongly inhibited by perennial sea ice. Between the ASIMin and the Arctic Sea Ice Maximum (ASIMax) which experiences seasonal sea ice, the sea ice related diatoms (mainly Fragilariopsis oceanica and Fragilariopsis cylindrus) were dominant, thereby confirming that sea ice is an important influencing factor. The Chaetoceros resting spores were more abundant in the Chukchi Sea, which corresponds well with the active phytoplankton distribution in the water column, and is possibly attributed to the stronger hydrodynamic conditions present in the Bering Sea. The abundances of Chaetoceros resting spores were the lowest on the northeast Bering Shelf, possibly because of lower water depth, stronger coastal currents, river influx, coarser particle sizes and stronger winds and bottom currents. The Arctic Diatom Group (dominated by Bacterosira bathyomphala, Thalassiosira antarctica v. borealis and Thalassiosira antarctica resting spores) was more abundant in the Bering Basin and the areas central of and to the north of Chukchi Plateau, while the Coastal Benthic Diatoms (including Paralia sulcata and Delphineis surirella) were mainly found on the northeast Bering Shelf and nearby Cape Lisburne in the Chukchi Sea. Thalassiosira nordenskioeldii was found to be the most abundant around the Bering Strait, while Neodenticula seminae was only found in the Bering Sea and mainly distributed in the Bering Basin, indicating its close correlation with the Pacific waters
Scale and scope of maritime cargoes through the Arctic Passages
Get PDFThis paper investigates the sources of goods being shipped through the Arctic passages, and trade generated in the Arctic, including oil and gas exploitation. Furthermore, it assesses the present situation for maritime cargo shipped from the Far East to Northwestern Europe and North America. Two main types of cargo are predicted to pass through the Arctic passages in the future. First, about 10 million t of liquefied natural gas will be delivered from Russia and the Nordic Arctic to the Far East by 2030. Second, there will be two-way trade flow of containerized cargo from the Far East to Europe and the United States through the Northeast, Central and Northwest Passages. This will relieve pressure on present routes from the Far East to Northwestern Europe and North America. If Arctic navigation is technically possible in all seasons and shipping costs fall to those of ordinary ships, then assuming an equal share of shipping volume with the traditional canal routes, the maximum container freight passing through the Arctic passages by 2030 will be approximately 17.43 million TEUs (Twenty-foot Equivalent Units) per year, which is 85% of the volume transported on traditional canal routes in 2011. We conclude that there will be large-scale gas transportation through the Northeast Passage in the near future, and transit shipping across the Arctic will focus more on container transportation. The differences in shipping costs between Arctic routes and traditional canal routes are also compared
Remote sensing backscattering model for sea ice: Theoretical modelling and analysis
Get PDFRemote sensing has been used in Antarctic studies as an earth observation technique to study the polar region. A remote sensing forward model is an important tool in polar research to study and understand scattering mechanisms and sensitivity of physical parameters of snow and sea ice. In this paper, a reliable theoretical model to study sea ice is developed. The theoretical model in a prior work was improved by including multiple-surface scattering, based on an existing integral equation model and additional second-order surface-volume scattering. This model is applied to a desalinated ice layer above thick saline ice and analyzed using different frequencies, bottom surface roughness and sea-ice layer thickness. Improvement in calculation of the backscattering coefficient of the sea-ice layer is investigated for both co-polarized and cross-polarized returns. The effect on each scattering mechanism is also investigated, to understand in more detail the effect of surface multiple scattering and second-order surface-volume scattering. Comparisons are also made with field measurement results, to validate the theoretical model. Results show improvement in the total backscattering coefficient for cross-polarized return in the studied range, suggesting that multiple-surface scattering and surface-volume scattering up to second order are important scattering mechanisms in the sea-ice layer and should not be ignored in polar research
Hydrochemistry and sediment characteristics of polar periglacial lacustrine environments on Fisher Island and Broknes Peninsula, East Antarctica
Get PDFFisher Island and Broknes Peninsula in the Larsemann Hills constitute part of a polar lowland periglacial environment between marine and glacial ecosystems. The landscape is characterized by gently rolling hills and broad valleys interspersed with lakes formed in glacially scoured basins. We analyzed the physicochemical parameters and the ionic constituents of water samples from 10 lakes in each of these two locations. Our results showed considerable differences between the two regions and demonstrated the influence of lithology and processes including weathering, evaporation, and atmospheric precipitation. All major cations and anions in the lake waters showed positive correlations indicating balanced ionic concentrations. Unconsolidated sediments were sparsely distributed and scattered over glacial deposits, valley fills, and occasional moraine ridges. The type and rate of sedimentation was mainly controlled by surface run-off and aeolian influx. The sediment samples from lake beds and the catchment area on Fisher Island were immature and poorly to very poorly sorted, consisting of gravelly sand with negligible silt and finer fractions. Sediments had a polymodal grain size distribution with the two major populations lying between −2 and −1 phi and between 0 and 1.5 phi. The sediments were lithic arenite to arkosic in composition and the microtextures imprinted over quartz grains were dominated by mechanical textures resulting from several stages of glacial crushing and grinding. The presence of deep dissolution cavities, cryptocrystalline precipitation, and euhedral crystal growth signified the effect of chemical activity after the deposition of grains in the lacustrine environment