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  • 1
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    The occurrence of the copepods Stephos longipes (Calanoida) and Drescheriella glacialis (Harpacticoida) in summer sea ice in the Weddell Sea, Antarctica (2001)
    Cambridge University Press
    Details
    Publication Date: 2001-06-01
    Description: In January to March 1997, a RV Polarstern cruise that transected the Weddell Sea resulted in samples being taken in thick pack ice in the south-eastern Weddell Sea and then along the marginal ice edge towards the Antarctic Peninsula. Several ice types were thus sampled over a wide geographic area during late summer/early autumn. Common features of the first warm period was the occurrence of surface ponds, and that many floes had quasi-continuous horizontal gaps, underlying a layer of ice and metamorphic snow. With the onset of cold air temperatures in late February the gaps rapidly refroze. The calanoid copepod Stephos longipes occurred in all habitats encountered and showed highest numbers in the surface ice in summer, in the gap water during both seasons and in the refrozen gap water in autumn. Nauplii outnumbered copepodids in the surface ice and refrozen gap water, while in the gap water copepodids, mainly stages CI–CIII in summer and CII–CIV in autumn, comprised about 70% of the total population. The harpacticoid species Drescheriella glacialis did not occur in all habitats and was missing in surface ponds and new ice. Nauplii of D. glacialis were rarely found in gap water, but predominated in the refrozen gaps.
    Print ISSN: 0954-1020
    Electronic ISSN: 1365-2079
    Topics: Biology , Geography , Geosciences
    Published by Cambridge University Press
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  • 2
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    Behaviour of dissolved organic matter and inorganic nutrients during experimental sea-ice formation (2001)
    Cambridge University Press
    Details
    Publication Date: 2001-01-01
    Description: It is well established that during sea-ice formation, crystals aggregate into a solid matrix, and dissolved sea-water constituents, including inorganic nutrients, are rejected from the ice matrix. However, the behaviour of dissolved organic matter (DOM) during ice formation and growth has not been studied to date. DOM is the primary energetic substrate for microbial heterotrophic activity in sea water and sea ice, and therefore it is at the base of the trophic fluxes within the microbial food web. The aim of our study was to compare the behaviour of DOM and inorganic nutrients during formation and growth of sea ice. Experiments were conducted in a large indoor ice-tank facility (Hamburg Ship Model Basin, Germany) at −15°C. Three 1 m3 tanks, to which synthetic sea water, nutrients and dissolved organic compounds (diatom-extracted DOM) had been added, were sampled over a period of 5 days during sea-ice formation. Samples were collected throughout the experiment from water underlying the ice, and at the end from the ice as well. Brine was obtained from the ice by centrifuging ice cores. Inorganic nutrients (nitrate and phosphate) were substantially enriched in brine in comparison to water and ice phases, consistent with the processes of ice formation and brine rejection. Dissolved organic carbon (DOC) was also enriched in brine but was more variable and enriched in comparison to a dilution line. No difference in bacteria numbers was observed between water, ice and brine. No bacteria growth was measured, and this therefore had no influence on the measurable DOC levels. We conclude that the incorporation of dissolved organic compounds in newly forming ice is conservative. However, since the proportions of DOC in the brine were partially higher than those of the inorganic nutrients, concentrating effects of DOC in brine might be different compared to salts.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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  • 3
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    Dissolved organic matter in Antarctic sea ice (2001)
    Cambridge University Press
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    Publication Date: 2001-01-01
    Description: It has been hypothesized that there are significant dissolved organic matter (DOM) pools in sea-ice systems, although measurements of DOM in sea ice have only rarely been made. The significance of DOM for ice-based productivity and carbon turnover therefore remains highly speculative. DOM within sea ice from the Amundsen and Bellingshausen Seas, Antarctica, in 1994 and the Weddell Sea, Antarctica, in 1992 and 1997 was investigated. Measurements were made on melted sea-ice sections in 1994 and 1997 and in sea-ice brines in 1992. Dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) concentrations in melted ice cores were up to 1.8 and 0.78 mM, respectively, or 30 and 8 times higher than those in surface water concentrations, respectively. However, when concentrations within the brine channel/pore space were calculated from estimated brine volumes, actual concentrations of DOC in brines were up to 23.3 mM and DON up to 2.2 mM, although mean values were 1.8 and 0.15 mM, respectively. There were higher concentrations of DOM in warm, porous summer second-year sea ice compared with colder autumn first-year ice, consistent with the different biological activity supported within the various ice types. However, in general there was poor correlation between DOC and DON with algal biomass and numbers of bacteria within the ice. The mean DOC/DON ratio was 11, although again values were highly variable, ranging from 3 to highly carbon-enriched samples of 95. Measurements made on a limited dataset showed that carbohydrates constitute on average 35% of the DOC pool, with highly variable contributions of 1−99%.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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  • 4
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    Vertical zonation and community transition of sea-ice diatoms in fast ice and platelet layer, Weddell Sea, Antarctica (2001)
    Cambridge University Press
    Details
    Publication Date: 2001-01-01
    Description: Changes in the taxonomic composition of diatoms in fast ice as well as in the underlying platelet layer were followed from June to December 1995 in Atka Bay Antarctica. Four communities were clearly distinguished: (1) an interior community dominated by flagellates in spring; (2) a bottom community dominated by a small form of Fragilariopsis cylindrus; (3) a platelet-ice layer dominated by Amphiprora Kufferathii and Thalassionema sp. growing attached to the ice platelets; and (4) an interstitial community dominated by Chaetoceros neglectus growing in the water between the platelets. Species composition distribution and succession in these communities were related to changes in silicate concentration, pore space and ice-formation processes and the ability of some cells to grow attached to ice platelets. The presence of the platelet-layer communities may have implications for paleoglaciology
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
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