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Hokkaido University Collection of Scholarly and Academic Papers (135.521 recursos)

HUSCAP (Hokkaido University Collection of Scholarly and Academic Papers) contains peer-reviewed journal articles, proceedings, educational resources and any kind of scholarly works of Hokkaido University.

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Mostrando recursos 1 - 20 de 532

  1. Functional heterologous expression and characterization of mannuronan C5-epimerase from the brown alga Saccharina japonica

    Inoue, Akira; Satoh, Aya; Morishita, Mio; Tokunaga, Yuko; Miyakawa, Takuya; Tanokura, Masaru; Ojima, Takao
    Brown algae produce alginate that has various ratios and diverse sequences of two uronic acids, beta-D-mannuronic acid and alpha-L-guluronic acid, compared with those of alginate produced by bacteria. This diversity of alginate in brown algae is caused by mannuronan C5-epimerases (MC5Es), which catalyze the conversion of beta-D-mannuronic acid to alpha-L-guluronic acid. Although several bacterial MC5E enzymes have been well characterized, to date, there exists no information on the biochemical properties of eukaryotic MC5E. In this study, MC5E expression was detected in a brown alga Saccharina japonica sporophyte by immunoblot analysis. We also searched for MC5E mRNA from S. japonica by...

  2. Biogeochemical Impact of Snow Cover and Cyclonic Intrusions on the Winter Weddell Sea Ice Pack

    Tison, J.-L.; Schwegmann, S.; Dieckmann, G.; Rintala, J.-M.; Meyer, H.; Moreau, S.; Vancoppenolle, M.; Nomura, D.; Engberg, S.; Blomster, L. J.; Hendricks, S.; Uhlig, C.; Luhtanen, A.-M.; de Jong, J.; Janssens, J.; Carnat, G.; Zhou, J.; Delille, B.
    Sea ice is a dynamic biogeochemical reactor and a double interface actively interacting with both the atmosphere and the ocean. However, proper understanding of its annual impact on exchanges, and therefore potentially on the climate, notably suffer from the paucity of autumnal and winter data sets. Here we present the results of physical and biogeochemical investigations on winter Antarctic pack ice in the Weddell Sea (R. V. Polarstern AWECS cruise, June–August 2013) which are compared with those from two similar studies conducted in the area in 1986 and 1992. The winter 2013 was characterized by a warm sea ice cover...

  3. Macro-nutrient concentrations in Antarctic pack ice : overall patterns and overlooked processes

    Fripiat, François; Meiners, Klaus M.; Vancoppenolle, Martin; Papadimitriou, Stathys; Thomas, David N.; Ackley, Stephen F.; Arrigo, Kevin R.; Carnat, Gauthier; Cozzi, Stefano; Delille, Bruno; Dieckmann, Gerhard S.; Dunbar, Robert B.; Fransson, Agneta; Kattner, Gerhard; Kennedy, Hilary; Lannuzel, Delphine; Munro, David R.; Nomura, Daiki; Rintala, Janne-Markus; Schoemann, Véronique; Stefels, Jacqueline; Steiner, Nadja; Tison, Jean-Louis
    Antarctic pack ice is inhabited by a diverse and active microbial community reliant on nutrients for growth. Seeking patterns and overlooked processes, we performed a large-scale compilation of macro-nutrient data (hereafter termed nutrients) in Antarctic pack ice (306 ice-cores collected from 19 research cruises). Dissolved inorganic nitrogen and silicic acid concentrations change with time, as expected from a seasonally productive ecosystem. In winter, salinity-normalized nitrate and silicic acid concentrations (C*) in sea ice are close to seawater concentrations (Cw), indicating little or no biological activity. In spring, nitrate and silicic acid concentrations become partially depleted with respect to seawater (C*...

  4. Helicopter-borne observations with portable microwave radiometer in the Southern Ocean and the Sea of Okhotsk

    Tamura, Takeshi; Ohshima, Kay I.; Lieser, Jan L.; Toyota, Takenobu; Tateyama, Kazutaka; Nomura, Daiki; Nakata, Kazuki; Fraser, Alexander D.; Jansen, Peter W.; Newbery, Kym B.; Massom, Robert A.; Ushio, Shuki
    Accurately measuring and monitoring the thickness distribution of thin ice is crucial for accurate estimation of ocean–atmosphere heat fluxes and rates of ice production and salt flux in ice-affected oceans. Here we present results from helicopter-borne brightness temperature (TB) measurements in the Southern Ocean in October 2012 and in the Sea of Okhotsk in February 2009 carried out with a portable passive microwave (PMW) radiometer operating at a frequency of 36 GHz. The goal of these measurements is to aid evaluation of a satellite thin-ice thickness algorithm which uses data from the spaceborne Advanced Microwave Scanning Radiometer–Earth Observing System AMSR-E)...

  5. Effect of glacial drainage water on the CO2 system and ocean acidification state in an Arctic tidewater-glacier fjord during two contrasting years

    Fransson, Agneta; Chierici, Melissa; Nomura, Daiki; Granskog, Mats A.; Kristiansen, Svein; Martma, Tõnu; Nehrke, Gernot
    In order to investigate the effect of glacial water on the CO2 system in the fjord, we studied the variability of the total alkalinity (AT), total dissolved inorganic carbon (CT), dissolved inorganic nutrients, oxygen isotopic ratio (δ18O), and freshwater fractions from the glacier front to the outer Tempelfjorden on Spitsbergen in winter 2012 (January, March, and April) and 2013 (April) and summer/fall 2013 (September). The two contrasting years clearly showed that the influence of freshwater, mixing, and haline convection affected the chemical and physical characteristics of the fjord. The seasonal variability showed the lowest calcium carbonate saturation state (Ω) and...

  6. Methods for biogeochemical studies of sea ice : the state of the art, caveats, and recommendations

    Miller, Lisa A.; Fripiat, Francois; Else, Brent G.T.; Bowman, Jeff S.; Brown, Kristina A.; Collins, R. Eric; Ewert, Marcela; Fransson, Agneta; Gosselin, Michel; Lannuzel, Delphine; Meiners, Klaus M.; Michel, Christine; Nishioka, Jun; Nomura, Daiki; Papadimitriou, Stathys; Russell, Lynn M.; Sørensen, Lise Lotte; Thomas, David N.; Tison, Jean-Louis; van Leeuwe, Maria A.; Vancoppenolle, Martin; Wolff, Eric W.; Zhou, Jiayun
    Over the past two decades, with recognition that the ocean’s sea-ice cover is neither insensitive to climate change nor a barrier to light and matter, research in sea-ice biogeochemistry has accelerated significantly, bringing together a multi-disciplinary community from a variety of fields. This disciplinary diversity has contributed a wide range of methodological techniques and approaches to sea-ice studies, complicating comparisons of the results and the development of conceptual and numerical models to describe the important biogeochemical processes occurring in sea ice. Almost all chemical elements, compounds, and biogeochemical processes relevant to Earth system science are measured in sea ice, with...

  7. Evidence for significant protein-like dissolved organic matter accumulation in Sea of Okhotsk sea ice

    Granskog, Mats A.; Nomura, Daiki; Müller, Susann; Krell, Andreas; Toyota, Takenobu; Hattori, Hiroshi
    Absorption and fluorescence of chromophoric dissolved organic matter (CDOM) in sea ice and surface waters in the southern Sea of Okhotsk was examined. Sea-water CDOM had featureless absorption increasing exponentially with shorter wavelengths. Sea ice showed distinct absorption peaks in the ultraviolet, especially in younger ice. Older first-year sea ice had relatively flat absorption spectra in the ultraviolet range. Parallel factor analysis (PARAFAC) identified five fluorescent CDOM components, two humic-like and three protein-like. Sea water was largely governed by humic-like fluorescence. In sea ice, protein-like fluorescence was found in considerable excess relative to sea water. The accumulation of protein-like CDOM...

  8. Winter-to-summer evolution of pCO2 in surface water and air–sea CO2 flux in the seasonal ice zone of the Southern Ocean

    Nomura, D.; Yoshikawa-Inoue, H.; Kobayashi, S.; Nakaoka, S.; Nakata, K.; Hashida, G.
    Partial pressure of CO2 (pCO2) in surface water and vertical profiles of the carbonate system parameters were measured during austral summer in the Indian sector of the Southern Ocean (64–67° S, 32–58° E) in January 2006 to understand the CO2 dynamics of seawater in the seasonal ice zone. Surface-water pCO2 ranged from 275 to 400 μatm, and longitudinal variations reflected the dominant influence of water temperature and dilution by sea ice meltwater between 32 and 40° E and biological productivity between 40 and 58° E. Using carbonate system data from the temperature minimum layer (−1.9 °C < T < −1.5...

  9. Arctic and Antarctic sea ice acts as a sink for atmospheric CO2 during periods of snowmelt and surface flooding

    Nomura, Daiki; Granskog, Mats A.; Assmy, Philipp; Simizu, Daisuke; Hashida, Gen
    In this study, we present evidence that Antarctic and Arctic sea ice act as sink for atmospheric CO2 during periods of snowmelt and surface flooding. The CO2 flux measured directly at the flooded sea ice surface (Fflood) constituted a net CO2 sink of −1.1 ± 0.9 mmol C m−2 d−1 (mean ± 1 SD), which was an order of magnitude higher than the flux measured at the snow‐air surface (Fsnow) and bare ice surface (Fice). The Fsnow/Fflood ratio decreased with increasing water equivalent of snow and superimposed‐ice, suggesting that the properties of snow and superimposed‐ice formation affect the magnitude of the CO2 flux. The...

  10. Characterization of ikaite (CaCO3·6H2O) crystals in first-year Arctic sea ice north of Svalbard

    Nomura, Daiki; Assmy, Philipp; Nehrke, Gernot; Granskog, Mats A.; Fischer, Michael; Dieckmann, Gerhard S.; Fransson, Agneta; Hu, Yubin; Schnetger, Bernhard
    We identified ikaite crystals (CaCO3 ·6H2O) and examined their shape and size distribution in first-year Arctic pack ice, overlying snow and slush layers during the spring melt onset north of Svalbard. Additional measurements of total alkalinity (TA) were made for melted snow and sea-ice samples. Ikaite crystals were mainly found in the bottom of the snowpack, in slush and the surface layers of the sea ice where the temperature was generally lower and salinity higher than in the ice below. Image analysis showed that ikaite crystals were characterized by a roughly elliptical shape and a maximum caliper diameter of 201.0±115.9...

  11. An artificial pool experiment in Antarctic sea ice : effects of sea ice melting on physical and biogeochemical components of pool water

    Nomura, Daiki; Simizu, Daisuke; Chavanich, Suchana; Shinagawa, Hideo; Fukuchi, Mitsuo
    We performed an artificial pool experiment in the Antarctic multi-year land-fast ice to examine and simulate the effect of sea ice melting on physical and biogeochemical components of the sea ice field. The input of snow and ice meltwater resulted in warmer, low salinity water at the surface of the pool and probably stratification of the less dense water. Current speed measurements also pointed to water stratification within the pool. Rapid phytoplankton growth in the pool resulted in drastic decreases in concentrations of dissolved inorganic carbon and nutrients (NO3- and Si(OH)4) in the surface waters of the pool, particularly depleted...

  12. Direct measurements of DMS flux from Antarctic fast sea ice to the atmosphere by a chamber technique

    Nomura, Daiki; Koga, Seizi; Kasamatsu, Nobue; Shinagawa, Hideo; Simizu, Daisuke; Wada, Makoto; Fukuchi, Mitsuo
    We present the first direct measurements of dimethylsulfide (DMS) emissions from Antarctic sea ice to the atmosphere during the seasonal warming period obtained using a chamber technique. Estimated DMS fluxes measured over the snow and superimposed ice (ice formed by the freezing of snow meltwater) were from 0.1 to 0.3 μmol m−2 d−1. The DMS fluxes measured directly over the sea‐ice slush layer after removal of the snow and superimposed ice, ranged from 0.1 to 5.3 μmol m−2 d−1, were large compared to those measured over the snow and superimposed ice. The DMS concentrations in slush water ranged from 1.0...

  13. Incorporation of nitrogen compounds into sea ice from atmospheric deposition

    Nomura, Daiki; McMinn, Andrew; Hattori, Hiroshi; Aoki, Shigeru; Fukuchi, Mitsuo
    Temporal measurements of temperature, salinity, water–oxygen isotopic ratio and nutrient concentrations at Saroma-ko Lagoon, southern Sea of Okhotsk, were made in February–March 2008 to examine the processes by which nitrogen compounds from the atmosphere were incorporated via snowfall into sea ice. Granular ice made up more than half the ice thickness, and the mass fraction of snow in the snow-ice layer on top of the ice ranged from 0.8% to 46.9%. The high concentrations of NO3− + NO2− and NH4+ observed in the snow and snow-ice throughout the study period were likely due to the proximity of the study site,...

  14. 「しらせ」搭載用コンテナ実験室の概要

    和田, 誠; 古賀, 聖治; 野村, 大樹; 小達, 恒夫; 福地, 光男
    2009年に就航した新「しらせ」には,改造した20 ftコンテナを船上実験室として搭載するスペースが確保された.第51次日本南極地域観測隊では,このコンテナ実験室の内部に大気中の硫化ジメチル濃度を測定するためのプロトン移動反応質量分析計を収納し,観測を実施した.本稿では,コンテナ実験室の概要と今後改良すべき点等について報告する.

  15. Biogeochemical properties of water in surface ponds on Antarctic fast ice and their relationship with underlying sea-ice properties

    Nomura, Daiki; Simizu, Daisuke; Shinagawa, Hideo; Oouchida, Chinatsu; Fukuchi, Mitsuo
    Surface ponds on Antarctic fast ice were examined by measuring temperature, salinity and concentrations of chlorophyll a (Chl-a), dissolved inorganic carbon (DIC) and nutrients (NO3 + NO2, PO4 and SiO2) in the surface pond water and under-ice water. Sea-ice cores were also collected from the bottom of a surface pond (pond-ice core) and from a site away from the pond (bare-ice core). Time-series measurements of surface pond water temperature showed that it varied with solar radiation rather than with air temperature. Comparison of water properties between surface pond water and under-ice water suggested that DIC and nutrients were consumed by...

  16. Bromoform concentrations in slush-layer water in Antarctic fast ice

    Nomura, Daiki; Ooki, Atsushi; Simizu, Daisuke; Fukuchi, Mitsuo
    Bromoform concentrations in water of the slush layer that developed at the interface between snow and sea ice were measured during the seasonal warming in Lützow-Holm Bay, East Antarctica. Mean bromoform concentration was 5.5 ± 2.4 pmol l-1, which was lower than that of the under-ice water (10.9 ± 3.5 pmol l-1). Temporal decrease in bromoform concentrations and salinity with increasing temperature of the slush water suggest that the bromoform concentrations were reduced through dilution with meltwater input from the upper surface of sea ice. In contrast, bromoform concentrations in the under-ice water increased during this period while the salinity...

  17. DMSP and DMS in coastal fast ice and under-ice water of Lützow-Holm Bay, eastern Antarctica

    Nomura, Daiki; Kasamatsu, Nobue; Tateyama, Kazu; Kudoh, Sakae; Fukuchi, Mitsuo
    The combined concentration of total dimethylsulfoniopropionate and dimethylsulfide (DMSP+DMS) were measured in Antarctic fast ice on the coast of Lützow-Holm Bay, eastern Antarctica. High bulk-ice DMSP+DMS and chlorophyll a concentrations were found at the bottom of the sea ice, and these concentrations were higher than those in the under-ice water. The bulk-ice DMSP+DMS and chlorophyll a concentrations were highly correlated (r2=0.68, P<0.001), suggesting that the high bulk-ice DMSP+DMS concentrations were caused mainly by the presence of algae assemblages in the ice. The calculated brine DMSP+DMS concentrations were as high as 1100 nM in the bottom ice layer, and the vertical...

  18. Transport of chemical components in sea ice and under-ice water during melting in the seasonally ice-covered Saroma-ko Lagoon, Hokkaido, Japan

    Nomura, Daiki; Takatsuka, Toru; Ishikawa, Masao; Kawamura, Toshiyuki; Shirasawa, Kunio; Yoshikawa-Inoue, Hisayuki
    Physico-chemical properties in the brine and under-ice water were measured in Saroma-ko Lagoon on the northeastern coast of Hokkaido, Japan, which is connected to the Sea of Okhotsk, during the period from mid-February through mid-March 2006. The brine within brine channels of the sea ice was collected with a new sampling method examined in this study. Salinity, dissolved inorganic carbon (DIC), total alkalinity (TA), dissolved oxygen (DO), nutrients and oxygen isotopic ratio (δ18O) contained in the brine within brine channels of the sea ice and in the under-ice water varied largely in both time and space during the ice melt...

  19. The effect of sea-ice growth on air–sea CO2 flux in a tank experiment

    Nomura, Daiki; Yoshikawa-Inoue, Hisayuki; Toyota, Takenobu
    In order to clarify the CO2 exchange between the seawater and the overlying air during the sea-ice formation, we have carried out tank experiments in a low-temperature room. CO2 concentration above the sea-ice began to increase since the beginning of the sea-ice formation, and increased at larger rates with time and the decrease in air temperature. This increase of CO2 concentration in air was mainly caused by the increase in dissolved inorganic carbon concentration in the brine of the upper part of sea-ice, changes in CO2 solubility and dissociation constants of carbonic acid. The CO2 flux increased logarithmically with time,...

  20. Behavioral assay and chemical characters of female sex pheromones in the hermit crab Pagurus filholi

    Okamura, Saori; Kawaminami, Takuma; Matsuura, Hiroshi; Fusetani, Nobuhiro; Goshima, Seiji
    Males of the hermit crab Pagurus filholi perform assessment behavior toward females, as a preliminary step of precopulatory guarding, during the reproductive season. It is known that such behavior is elicited by female sex pheromones, but the compounds involved have never been characterized in this species. Several experiments were conducted to develop a reliable bioassay along with purification procedures to identify potential compounds with pheromonal activity in Pagurus filholi. We developed a bioassay protocol to assess pheromonal activity by using an empty shell with cotton containing either artificial seawater (control) or test water. We measured and compared the time duration...

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