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  • 1
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    Biogeochemical characterization of pennate diatom and Melosira arctica ice algal aggregates in the Central Arctic Ocean collected in summer 2011 and 2012 (2014)
    PANGAEA
    In:  Supplement to: Fernández-Méndez, Mar; Wenzhöfer, Frank; Peeken, Ilka; Sørensen, Heidi L; Glud, Ronnie N; Boetius, Antje; Vopel, Kay (2014): Composition, Buoyancy Regulation and Fate of Ice Algal Aggregates in the Central Arctic Ocean. PLoS ONE, 9(9), e107452, https://doi.org/10.1371/journal.pone.0107452
    Details
    Publication Date: 2024-03-22
    Description: Sea-ice diatoms are known to accumulate in large aggregates in and under the sea ice including melt ponds. In the Arctic, they can contribute substantially to particle export when sinking from the ice. The role and regulation of microbial aggregation in the highly seasonal, nutrient- and light-limited Arctic sea-ice ecosystem is not yet well understood, and may vary in relation to the fate of the Arctic sea-ice cover. To elucidate the mechanism controlling the formation and export of algal aggregates from sea ice, we investigated samples taken in late summer 2011 and 2012, during two cruises to the Eurasian Basin of the Central Arctic Ocean. Dense, spherical aggregates composed mainly of pennate diatoms, and filamentous aggregates formed by Melosira arctica were found in different degradation stages, with carbon to Chlorophyll a ratios ranging from 110 to 66700, and carbon to nitrogen molar ratios of 8-35 and 9-40, respectively. Fresh sub-ice algal aggregate densities ranged between 1 and 17 aggregates/m**2, corresponding to a net primary production of 0.4-40 mg C/m**2/d, contributing 3-80% of total biomass and up to 94% of total production at a local scale. A key factor controlling buoyancy of the aggregates was light intensity, regulating photosynthetic oxygen production and flotation by gas bubbles trapped within the mucous matrix, even at low ambient nutrient concentrations. Our data was used to evaluate the factors regulating the distribution and importance of the Arctic algal aggregates as carbon source for pelagic and benthic communities.
    Keywords: ABYSS; Algae aggregate, size; Arctic Ocean; ARK-XXVI/3; ARK-XXVII/3; Assessment of bacterial life and matter cycling in deep-sea surface sediments; AWI_BioOce; Bacterial organic carbon normalized to particulate organic carbon; Biological Oceanography @ AWI; Carbon, organic, dissolved normalized to particulate organic carbon; Carbon, organic, particulate; Carbon/Chlorophyll a ratio; Carbon/Nitrogen ratio; Chlorophyll a/chloroplastic pigment equivalents ratio; Chlorophyll a normalized to particulate organic carbon; Color description; Comment; Date/Time of event; Description; Event label; Gear; Habitat; ICE; Ice station; Ice station #1; Ice station #2; Ice station #3; Ice station #4; Ice station #5; Ice station #7; Irradiance; Latitude of event; Life stage; Longitude of event; Melt pond coverage on sea ice; Melt pond depth; Method comment; Net primary production of carbon normalized to particulate organic carbon; Nitrate; Normalized to particulate organic carbon; Number of measurements; Optional event label; Partical organic nitrogen normalized to particulate organic carbon; Phosphate; Polarstern; Prokaryotes, abundance as single cells normalized to particulate organic carbon; PS78/203-1; PS78/209-1; PS78/212-1; PS78 TransArc; PS80/224-1; PS80/237-1; PS80/255-1; PS80/323-1; PS80/349-1; PS80 IceArc; Replicates; Salinity; Sample ID; Silicate; Standard deviation; Taxon/taxa; Temperature, water; Transparent exopolymer particles/Carbon, organic, particulate ratio; Transparent exopolymer particles normalized to particulate organic carbon; Type
    Type: Dataset
    Format: text/tab-separated-values, 388 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 2
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    Oxygen fluxes beneath Arctic land-fast ice and pack ice: towards estimates of ice productivity (2018)
    Springer
    In:  EPIC3Polar Biology, Springer, ISSN: 0722-4060
    Details
    Publication Date: 2018-06-14
    Description: Sea-ice ecosystems are among the most extensive of Earth’s habitats; yet its autotrophic and heterotrophic activities remain poorly constrained. We employed the in situ aquatic eddy-covariance (AEC) O2 flux method and laboratory incubation techniques (H14CO3−, [3H] thymidine and [3H] leucine) to assess productivity in Arctic sea-ice using different methods, in conditions ranging from land-fast ice during winter, to pack ice within the central Arctic Ocean during summer. Laboratory tracer measurements resolved rates of bacterial C demand of 0.003–0.166 mmol C m−2 day−1 and primary productivity rates of 0.008–0.125 mmol C m−2 day−1 for the different ice floes. Pack ice in the central Arctic Ocean was overall net autotrophic (0.002–0.063 mmol C m−2 day−1), whereas winter land-fast ice was net heterotrophic (− 0.155 mmol C m−2 day−1). AEC measurements resolved an uptake of O2 by the bottom-ice environment, from ~ − 2 mmol O2 m−2 day−1 under winter land-fast ice to~ − 6 mmol O2 m−2 day−1 under summer pack ice. Flux of O2-deplete meltwater and changes in water flow velocity masked potential biological-mediated activity. AEC estimates of primary productivity were only possible at one study location. Here, productivity rates of 1.3 ± 0.9 mmol O2 m−2 day−1, much larger than concurrent laboratory tracer estimates (0.03 mmol C m−2 day−1), indicate that ice algal production and its importance within the marine Arctic could be underestimated using traditional approaches. Given careful flux interpretation and with further development, the AEC technique represents a promising new tool for assessing oxygen dynamics and sea-ice productivity in ice-covered regions.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
    Location Call Number Limitation Availability
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    PAPER (OA)
  • 3
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    Oxygen fluxes beneath Arctic land-fast ice and pack ice: towards estimates of ice productivity (2018)
    Springer
    In:  Polar Biology, 41 (10). pp. 2119-2134.
    Details
    Publication Date: 2021-02-08
    Description: Sea-ice ecosystems are among the most extensive of Earth’s habitats; yet its autotrophic and heterotrophic activities remain poorly constrained. We employed the in situ aquatic eddy-covariance (AEC) O2 flux method and laboratory incubation techniques (H14CO3−, [3H] thymidine and [3H] leucine) to assess productivity in Arctic sea-ice using different methods, in conditions ranging from land-fast ice during winter, to pack ice within the central Arctic Ocean during summer. Laboratory tracer measurements resolved rates of bacterial C demand of 0.003–0.166 mmol C m−2 day−1 and primary productivity rates of 0.008–0.125 mmol C m−2 day−1 for the different ice floes. Pack ice in the central Arctic Ocean was overall net autotrophic (0.002–0.063 mmol C m−2 day−1), whereas winter land-fast ice was net heterotrophic (− 0.155 mmol C m−2 day−1). AEC measurements resolved an uptake of O2 by the bottom-ice environment, from ~ − 2 mmol O2 m−2 day−1 under winter land-fast ice to~ − 6 mmol O2 m−2 day−1 under summer pack ice. Flux of O2-deplete meltwater and changes in water flow velocity masked potential biological-mediated activity. AEC estimates of primary productivity were only possible at one study location. Here, productivity rates of 1.3 ± 0.9 mmol O2 m−2 day−1, much larger than concurrent laboratory tracer estimates (0.03 mmol C m−2 day−1), indicate that ice algal production and its importance within the marine Arctic could be underestimated using traditional approaches. Given careful flux interpretation and with further development, the AEC technique represents a promising new tool for assessing oxygen dynamics and sea-ice productivity in ice-covered regions.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00300-018-2350-1
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Unknown
    Composition, buoyancy regulation and fate of ice algal aggregates in the central Arctic Ocean (2014)
    Public Library of Science
    In:  PLoS ONE, 9 (9). e107452.
    Details
    Publication Date: 2015-03-12
    Description: Sea-ice diatoms are known to accumulate in large aggregates in and under sea ice and in melt ponds. There is recent evidence from the Arctic that such aggregates can contribute substantially to particle export when sinking from the ice. The role and regulation of microbial aggregation in the highly seasonal, nutrient- and light-limited Arctic sea-ice ecosystem is not well understood. To elucidate the mechanisms controlling the formation and export of algal aggregates from sea ice, we investigated samples taken in late summer 2011 and 2012, during two cruises to the Eurasian Basin of the Central Arctic Ocean. Spherical aggregates densely packed with pennate diatoms, as well as filamentous aggregates formed by Melosira arctica showed sign of different stages of degradation and physiological stoichiometries, with carbon to chlorophyll a ratios ranging from 110 to 66700, and carbon to nitrogen molar ratios of 8–35 and 9–40, respectively. Sub-ice algal aggregate densities ranged between 1 and 17 aggregates m−2, maintaining an estimated net primary production of 0.4–40 mg C m−2 d−1, and accounted for 3–80% of total phototrophic biomass and up to 94% of local net primary production. A potential factor controlling the buoyancy of the aggregates was light intensity, regulating photosynthetic oxygen production and the amount of gas bubbles trapped within the mucous matrix, even at low ambient nutrient concentrations. Our data-set was used to evaluate the distribution and importance of Arctic algal aggregates as carbon source for pelagic and benthic communities.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1371/journal.pone.0107452
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Engineering of a membrane-triggered activity switch in coagulation factor VIIa [Biochemistry] (2017)
    National Academy of Sciences
    Details
    Publication Date: 2017-11-22
    Description: Recombinant factor VIIa (FVIIa) variants with increased activity offer the promise to improve the treatment of bleeding episodes in patients with inhibitor-complicated hemophilia. Here, an approach was adopted to enhance the activity of FVIIa by selectively optimizing substrate turnover at the membrane surface. Under physiological conditions, endogenous FVIIa engages its...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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    PAPER CURRENT
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