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Author Thomas, D.N.; Kattner, G.; Engbrodt, R.; Giannelli, V.; Kennedy, H.; Haas, C.; Dieckmann, G.S. url  openurl
  Title Dissolved organic matter in Antarctic sea ice Type Journal Article
  Year 2001 Publication Annals of Glaciology Abbreviated Journal (up) Ann Glaciol  
  Volume 33 Issue 1 Pages 297-303  
  Keywords  
  Abstract 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%.  
  Address  
  Corporate Author Thesis  
  Publisher International Glaciological Society Place of Publication Cambridge Editor Intl. Symp. on Sea Ice and its Interaction with the Ocean, A. and B., Fairbanks, Alaska(USA), 19-23 Jun 2000,  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0260-3055 ISBN Medium  
  Area Expedition Conference  
  Notes Conference Approved no  
  Call Number refbase @ admin @ Thomas++2001 Serial 761  
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Author Arrigo, K.R.; Thomas, D.N. url  openurl
  Title Large scale importance of sea ice biology in the Southern Ocean Type Journal Article
  Year 2004 Publication Antarctic Science Abbreviated Journal (up) Antarct Sci  
  Volume 16 Issue 4 Pages 471-486  
  Keywords algae; Antarctic; biogeochemistry; carbon cycle; primary production; Full Data Records  
  Abstract Despite being one of the largest biomes on earth, sea ice ecosystems have only received intensive study over the past 30 years. Sea ice is a unique habitat for assemblages of bacteria, algae, protists, and invertebrates that grow within a matrix dominated by strong gradients in temperature, salinity, nutrients, and UV and visible radiation. A suite of physiological adaptations allow these organisms to thrive in ice, where their enormous biomass makes them a fundamental component of polar ecosystems. Sea ice algae are an important energy and nutritional source for invertebrates such as juvenile krill, accounting for up to 25% of total annual primary production in ice-covered waters. The ability of ice algae to produce large amounts of UV absorbing compounds such as mycosporine-like amino acids makes them even more important to organisms like krill that can incorporate these sunscreens into their own tissues. Furthermore, the nutrient and light conditions in which sea ice algae thrive induce them to synthesize enhanced concentrations of polyunsaturated fatty acids, a vital constituent of the diet of grazing organisms, especially during winter. Finally, sea ice bacteria and algae have become the focus of biotechnology, and are being considered as proxies of possible life forms on ice-covered extraterrestrial systems. An analysis of how the balance between sea ice and pelagic production might change under a warming scenario indicates that when current levels of primary production and changes in the areas of sea ice habitats are taken into account, the expected 25% loss of sea ice over the next century would increase primary production in the Southern Ocean by approximately 10%, resulting in a slight negative feedback on climate warming.  
  Address  
  Corporate Author Thesis  
  Publisher Cambridge University Press Place of Publication Cambridge Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0954-1020 ISBN Medium  
  Area Expedition Conference  
  Notes Review Approved no  
  Call Number refbase @ admin @ Arrigo+Thomas2004 Serial 729  
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Author Herborg, L.-M.; Thomas, D.N.; Kennedy, H.; Haas, C.; Dieckmann, G.S. url  openurl
  Title Dissolved carbohydrates in Antarctic sea ice Type Journal Article
  Year 2001 Publication Antarctic Science Abbreviated Journal (up) Antarct Sci  
  Volume 13 Issue 2 Pages 119-125  
  Keywords Doc; Mcho; Pcho; sea ice; bacteria; carbon cycling; diatoms; dissolved organic carbon; monocarbohydrates; polycarbohydrates  
  Abstract Concentrations of dissolved monocarbohydrates (MCHO) and polycarbohydrates (PCHO) were analysed in a variety of ice habitats from summer Weddell Sea sea ice (surface ponds, ice cores, gap layers and platelet ice). The dissolved organic carbon (DOC) pool in these habitats was also measured and the contribution of carbohydrate to this pool was assessed. The DOC concentrations within all sea ice habitats were high compared to surface seawater concentrations with values up to 958µMC being measured. Total carbohydrates (TCHO) were highest in the ice cores and platelet ice samples, up to 3 1% of the DOC pool, a reflection of the high algal biomass in these two habitat classes. TCHO in the other habitats ranged between 10% and 29% of DOC. The ratios of MCHO to PCHO varied considerably between the ice habitats: in surface ponds and ice cores MCHO was 70% of the TCHO pool, whereas in gap layers and platelet ice there were lower PCHO concentrations resulting in MCHO being 88% of TCHO.  
  Address  
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  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number refbase @ admin @ Herborg++2001 Serial 743  
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Author Schnack-Schiel, S.B.; Thomas, D.N.; Haas, C.; Dieckmann, G.S.; Alheit, R. url  openurl
  Title The occurrence of the copepods Stephos longipes (Calanoida) and Drescheriella glacialis (Harpacticoida) in summer sea ice in the Weddell Sea, Antarctica Type Journal Article
  Year 2001 Publication Antarctic Science Abbreviated Journal (up) Antarctic Sci  
  Volume 13 Issue 2 Pages 150-157  
  Keywords copepods; Drescheriella glacialis; sea ice; seasonality; Stephos longipes  
  Abstract 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 gapwater, but predominated in the refrozen gaps.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0954-1020 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number refbase @ admin @ Schnack-Schiel++2001_2 Serial 753  
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Author Mock, T.; Dieckmann, G.S.; Haas, C.; Krell, A.; Tison, J.-L.; Belem, A.L.; Papadimitriou, S.; Thomas, D.N. url  openurl
  Title Micro-optodes in sea ice: a new approach to investigate oxygen dynamics during sea ice formation Type Journal Article
  Year 2002 Publication Aquatic Microbial Ecology Abbreviated Journal (up) Aquat Microb Ecol  
  Volume 29 Issue 3 Pages 297-306  
  Keywords Fragilariopsis cylindrus; Oxygen; Methods; Micro-optodes; Sea ice; Biogeochemistry; Diatoms; Algae; Chlorophyll; Photosynthesis; Salinity effects; Sea water; Marine ecosystems; Chlorophylls; Dissolved oxygen; Gases; Epontic environment; Electrodes; Sensors; Brines; Ice-water interface; Ice formation; Bacillariophyceae  
  Abstract Oxygen micro-optodes were used to measure oxygen dynamics directly within the microstructure of sea ice by freezing the sensors into the ice during its formation. The experiment was conducted in a 4 m³ mesocosm filled with artificial seawater and inoculated with a unialgal culture of the common Antarctic ice diatom Fragilariopsis cylindrus (Bacillariophyceae) to a final chlorophyll a (chl a) concentration of 11 µg 1?¹. Ice growth was initiated 7 d after inoculation by reducing the air temperature to -10 plus or minus 2 degree C and terminated 17 d later. The final ice thickness was 27 cm. One optode was frozen into grease ice and 2 others into the skeletal layer of the growing ice sheet. Increasing oxygen concentrations during ice crystal formation at the water surface and the ice-water interface revealed a strong inclusion of oxygen, which was either physically trapped and/or the result of photosynthesising diatoms. The major portion of oxygen was present as gas bubbles due to super-saturation as a result of increasing salinity and oxygen production by diatoms. An increase in salinity due to a concurrent decrease in ice temperatures during subsequent sea ice development reduced the maximum concentration of dissolved oxygen within brine. Thus, dissolved oxygen concentrations decreased over time, whereas gaseous oxygen was released to the atmosphere and seawater. The sensors are a significant advance on more conventional microelectrodes, because the recordings can be temperature and salinity compensated in order to obtain precise measurements of oxygen dynamics with regard to total (dissolved and gaseous) and dissolved oxygen in sea ice. Optodes do not consume oxygen during measuremnet over a long period under extreme conditions, which is another advantage for long-term deployment in the field.  
  Address  
  Corporate Author Thesis  
  Publisher Inter-Research Place of Publication Oldendorf/Luhe Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0948-3055 ISBN Medium  
  Area Expedition Conference  
  Notes Marine Approved no  
  Call Number refbase @ admin @ Mock++2002 Serial 749  
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