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Author Thomas, D.N.; Gleitz, M. url  openurl
  Title Allocation of photoassimilated carbon into major algal metabolite fractions: Variation between two diatom species isolated from the Weddell Sea (Antarctica) Type Journal Article
  Year 1993 Publication Polar Biology Abbreviated Journal Polar Biol  
  Volume 13 Issue 4 Pages 281-286  
  Keywords carbon fixation; metabolites; biomass; Nitzschia curta; Chaetoceros; Psw; Weddell Sea  
  Abstract Distribution of photoassimilated carbon into major metabolite classes differed between two Antarctic diatom species, Nitzschia curta and a small unicellular Chaetoceros sp.. Time course uptake studies (over 54 h) revealed that¹?C allocation appeared to be equilibrated after approximately 8 h at light saturated photosynthesis. During short term dark periods (6 h), polysaccharides as well as low-molecular-weight compounds were catabolised to sustain protein synthesis in the dark, whilst lipid reserves were not mobilised for this process. Experiments with these two species were conducted at 0 and -1.5 degree C, although no difference in the distribution of radiolabel was measured between the two temperatures. It is hypothesised that under near-optimal conditions fast growing species are characterised by a high carbon turnover associated with a rapid flow of newly assimilated carbon into polymeric compound classes. On the other hand, slower growing species (such as N. curta) may store a significant amount of surplus carbon in the low-molecular-weight metabolite fraction. Species specific preferences were observed when comparing the accumulation of radiolabel into the lipid pools.  
  Address  
  Corporate Author Thesis  
  Publisher Springer-Verlag Place of Publication Heidelberg Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0722-4060 ISBN Medium  
  Area Expedition Conference  
  Notes Bibliogr.: 48 ref.; Marine Approved no  
  Call Number refbase @ admin @ Thomas+Gleitz1993 Serial 760  
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Author Thomas, D.N.; Lara, R.J.; Eicken, H.; Kattner, G.; Skoog, A. url  openurl
  Title Dissolved organic matter in Arctic multi-year sea ice during winter: major components and relationship to ice characteristics Type Journal Article
  Year 1995 Publication Polar Biology Abbreviated Journal Polar Biol  
  Volume 15 Issue 6 Pages 447-483  
  Keywords sea ice; Arctic; Dom  
  Abstract Ice cores were collected between 10.03.93 and 15.03.93 along a 200 m profile on a large ice floe in Fram Strait. The ice was typical of Arctic multi-year ice, having a mean thickness along the profile of 2.56 ±0.53 m. It consisted mostly of columnar ice (83%) grown through congelation of seawater at the ice bottom, and the salinity profiles were characterized by a linear increase from 0 psu at the top to values ranging between 3 and 5 psu at depth. Distributions of dissolved organic carbon (DOC) and nitrogen (DON) and major nutrients were compared with ice texture, salinity and chlorophyll a. DOC, DON, dissolved inorganic nitrogen (DIN), NH?? and NO?? were present in concentrations in excess of that predicted by dilution curves derived from Arctic surface water values. Only NO?? was depleted, although not exhausted. High DOC and DON values in conjunction with high NH?? levels indicated that a significant proportion of the dissolved organic matter (DOM) was a result of decomposition/grazing of ice algae and/or detritus. The combination of high NH?? and NO?? points to regeneration of nitrogen compounds. There was no significant correlation between DOC and Chl a in contrast to DON, which had a positively significant correlation with both salinity and Chl a, and the distribution of DOM in the cores might best be described as a combination of both physical and biological processes. There was no correlation between DOC and DON suggesting an uncoupling of DOC and DON dynamics in multi year ice.  
  Address  
  Corporate Author Thesis  
  Publisher Springer-Verlag Place of Publication Heidelberg Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0722-4060 ISBN Medium  
  Area Expedition Conference  
  Notes D Approved no  
  Call Number refbase @ admin @ Thomas++1995 Serial 763  
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Author Kaartokallio, H.; Kuosa, H.; Thomas, D.N.; Granskog, M.A.; Kivi, K. url  openurl
  Title Biomass, composition and activity of organism assemblages along a salinity gradient in sea ice subjected to river discharge in the Baltic Sea Type Journal Article
  Year 2006 Publication Polar Biology Abbreviated Journal Polar Biol  
  Volume 30 Issue 2 Pages 183-197  
  Keywords  
  Abstract A study was undertaken to examine the activity and composition of the seasonal Baltic Sea land-fast sea-ice biota along a salinity gradient in March 2003 in a coastal location in the SW coast of Finland. Using a multi-variable data set, the less well-known algal and protozoan communities, and algal and bacterial production in relation to the physical and chemical environment were investigated. Also, the first coincident measurements of bacterial production and dissolved organic matter (DOM) in a sea-ice system are reported. Communities in sea ice were clearly autotrophy-dominated with algal biomass representing 79% of the total biomass. Protozoa and rotifers made up 18% of biomass in the ice and bacteria only 3%. Highest biomasses were found in mid-transect bottom ice. Water column assemblages were clearly more heterotrophic: 39% algae, 12% bacteria and 49% for rotifers and protozoa. Few significant correlations existed between DOM and bacterial variables, reflecting the complex origin of ice DOM. Dynamics of dissolved organic carbon, nitrogen and phosphorus (DOC, DON and DOP) were also uncoupled. A functional microbial loop is likely to be present in the studied ice. Existence of an under-ice freshwater plume affects the ecosystem functioning: Under-ice water communities are influenced directly by river-water mixing, whereas the ice system seems to be more independent–the interaction mainly taking place through the formation of active bottom communities.  
  Address  
  Corporate Author Thesis  
  Publisher Springer-Verlag Place of Publication Heidelberg Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0722-4060 ISBN Medium  
  Area Expedition Conference  
  Notes Sampling: Nine stations along a 40km salinity gradient from inner Pojo Bay through the Archipelago to the edge of the open sea Approved no  
  Call Number refbase @ admin @ Kaartokallio++2006 Serial 744  
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Author Krell, A.; Schnack-Schiel, S.B.; Thomas, D.N.; Kattner, G.; Zipan, W.; Dieckmann, G.S. url  openurl
  Title Phytoplankton dynamics in relation to hydrography, nutrients and zooplankton at the onset of sea ice formation in the eastern Weddell Sea (Antarctica) Type Journal Article
  Year 2005 Publication Polar Biology Abbreviated Journal Polar Biol  
  Volume 28 Issue 9 Pages 700-713  
  Keywords Weddell Sea; Asf; Hydrography; Phytoplankton; Seasonal change; Community composition; Primary production; Zooplankton  
  Abstract The quantitative and qualitative distribution of phytoplankton was investigated along five North–South transects in the eastern Weddell Sea during the transition from late autumn to winter. Relationships with the regional hydrography, progressing sea ice coverage, nutrient distribution and zooplankton are discussed and compared with data from other seasons. To the north of the Antarctic Slope Front (ASF) a remnant temperature minimum layer was found above the primary pycnocline throughout summer. Surface waters had not entirely acquired typical winter characteristics. While temperature was already in the winter range, this was not the case for salinity. Highest biomass of phytoplankton, with the exception of the first transect, was found in the region adjoining the ASF to the north. Absolute chlorophyll a (Chl a) concentrations dropped from 0.35 to 0.19 µg/1. Nutrient pools exhibited a replenishing tendency. Ammonium concentrations were high (0.75–2 µmol/1), indicating extensive heterotrophic activity. The phytoplankton in the ASF region was dominated by nanoflagellates, particularly Phaeocystis spp.. North of the ASF the abundance of diatoms increased, with Fragilariopsis spp., F. cylindrus and Thalassiosira spp. dominating. Community structure varied both due to hydrographical conditions and the advancing ice edge. The phytoplankton assemblage formed during late autumn were very similar to the ones found in early spring. A POC/PON ratio close to Redfield, decreasing POC concentration and a high phaeophytin/ Chl a ratio, as well as a high abundance of mesozooplankton indicated that a strong grazing pressure was exerted on the phytoplankton community. A comparison between primary production (PP) in the water column and the sea ice showed a shift of the major portion of PP into the ice during the period of investigation.  
  Address  
  Corporate Author Thesis  
  Publisher Springer-Verlag Place of Publication Heidelberg Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0722-4060 ISBN Medium  
  Area Expedition Conference  
  Notes Isi:000231421200006 Approved no  
  Call Number refbase @ admin @ Krell++2005 Serial 747  
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Author Thomas, D.N.; Dieckmann, G.S. url  openurl
  Title Antarctic sea ice – a habitat for extremophiles Type Journal Article
  Year 2002 Publication Science Abbreviated Journal Science  
  Volume 295 Issue 5555 Pages 641-644  
  Keywords Microorganisms; Sea ice; Ecosystems; Polar zones; Antarctic zone; Epontic organisms; Sea ice ecology; Antarctic sea ice; Marine microorganisms; Marine ecosystems; Bacteria; Algae; Psychrophilic bacteria; extremophiles; Ps; Antarctica  
  Abstract The pack ice of Earth's polar oceans appears to be frozen white desert, devoid of life. However, beneath the snow lies a unique habitat for a group of bacteria and microscopic plants and animals that are encased in an ice matrix at low temperatures and light levels, with the only liquid being pockets of concentrated brines. Survival in these conditions requires a complex suite of physiological and metabolic adaptations, but sea-ice organisms thrive in the ice, and their prolific growth ensures they play a fundamental role in polar ecosystems. Apart from their ecological importance, the bacterial and algae species found in sea ice have become the focus for novel biotechnology, as well as being considered proxies for possible life forms on ice- covered extraterrestrial bodies.  
  Address  
  Corporate Author Thesis  
  Publisher American Association for the Advancement of Science Place of Publication Washington, DC Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0036-8075 ISBN Medium  
  Area Expedition Conference  
  Notes Review Approved no  
  Call Number refbase @ admin @ Thomas+Dieckmann2002_2 Serial 759  
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