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Author Gleitz, M.; Thomas, D.N. url  openurl
  Title Physiological responses of a small Antarctic diatom (Chaetoceros sp.) to simulated environmental constraints associated with sea-ice formation Type Journal Article
  Year 1992 Publication Marine Ecology Progress Series Abbreviated Journal Mar Ecol Prog Ser  
  Volume 88 Issue 2-3 Pages 271-278  
  Keywords plant physiology; abiotic factors; temperature effects; salinity effects; irradiance; sea ice; growth; photosynthesis; Chaetoceros; Psw; Weddell Sea; simulation  
  Abstract The physiological responses of a small unicellular Chaetoceros species, isolated from the Weddell Sea, Antarctica, to changes in temperature, salinity and irradiance simulating those that occur during new-ice formation were investigated. The combination of increased salinity, increased quantum irradiance and decreased temperature significantly reduced growth and photosynthetic rates compared to the control, although cellular metabolism was not inhibited. The cells retained the capacity to photoacclimate, which was observed in the variations in cellular chlorophyll a concentrations and carbon allocation patterns. In terms of photosynthesis, a doubling of quantum irradiance apparently compensated for the adverse effects of increased salinity and lowered temperature. It is thus hypothesized that at least some species of the late season phytoplankton population survive incorporation into ice and continue to photosynthesize and grow under the extreme conditions encountered during sea-ice formation.  
  Address  
  Corporate Author Thesis  
  Publisher Inter-Research Place of Publication Oldendorf/Luhe Editor (up)  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0171-8630 ISBN Medium  
  Area Expedition Conference  
  Notes Bibliogr.: 38 ref.; Marine Approved no  
  Call Number refbase @ admin @ Gleitz+Thomas1992 Serial 735  
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Author Gleitz, M.; Thomas, D.N. url  openurl
  Title Variation in phytoplankton standing stock, chemical composition and physiology during sea-ice formation in the southeastern Weddell Sea, Antarctica Type Journal Article
  Year 1993 Publication Journal of Experimental Marine Biology and Ecology Abbreviated Journal J Exp Mar Biol Ecol  
  Volume 173 Issue 2 Pages 211-230  
  Keywords Antarctic; ecophysiology; ice algae; phytoplankton; primary production; sea-ice formation; biochemical composition; plant physiology; Psw; Weddell Sea; population number; sea ice; algae; standing crop  
  Abstract Changes in physico-chemical conditions, phytoplankton biomass, biochemical composition and primary productivity were investigated during autumnal sea-ice formation in the southeastern Weddell Sea, Antarctica. During sea-ice growth, brine salinities gradually increased with decreasing temperature. Nutrient concentrations in the brine of sea ice older than 2 weeks were lower than calculated from initial surface seawater values. The concomittant accumulation of phytoplankton biomass could not be explained solely by physical enrichment. We suggest that several microalgal species retained the capacity to assimilate nutrients and continued to grow in newly formed sea ice. However, nutrient depletions were moderate, and biochemical analyses did not indicate nutrient stress of algal metabolism. Relative abundance of smaller diatom species increased during ice growth, suggesting that pore space available for colonization in conjunction with physiological acclimation capacity were major factors determining successional patterns in recently formed sea ice. Even though ice algal assemblages apparently sustained the capacity to acclimate to reduced irradiances brought about by ice growth and increasing snow cover, maximum primary production was considerably lower than values usually reported from spring and summer ice communities. Therefore, autumnal primary production in newly formed sea ice may not add greatly to total annual production, but may provide an important food source for ice-associated grazers during the winter period, when phytoplankton biomass in the water column is extremely low.  
  Address  
  Corporate Author Thesis  
  Publisher Elsevier Science B.V. Place of Publication Amsterdam Editor (up)  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0022-0981 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number refbase @ admin @ Gleitz+Thomas1993 Serial 734  
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Author Gomez, I.; Wiencke, C.; Thomas, D.N. url  openurl
  Title Variations in photosynthetic characteristics of the Antarctic marine brown alga Ascoseira mirabilis in relation to thallus age and size Type Journal Article
  Year 1996 Publication European Journal of Phycology Abbreviated Journal Eur J Phycol  
  Volume 31 Issue 2 Pages 167-172  
  Keywords photosynthesis: thallus: carbon fixation; growth curves; algae; age; Thalli; marine flora; Ascoseira mirabilis; Antarctica  
  Abstract Growth, photosynthesis, dark respiration, chlorophyll a (Chl a) content and dry weight were measured in 2- and 3-year-old plants of Ascoseira mirabilis (Ascoseirales), cultivated in the laboratory under changing daylengths which matched the seasonal variations in the Antarctic. Determinations were made in four thallus regions. Growth of A. mirabilis was seasonal, with higher rates in spring. Parameters such as net photosynthesis (P sub(max)), photosynthetic efficiency ( alpha ), both measured on a fresh weight (FW) basis, and dry weight content, showed significant age- and size-dependent variations. In contrast, no variations were observed in dark respiration, initial light-saturating point of photosynthesis (I sub(k)) and Chl a contents. P sub(max) had maximum values close to 16.5 mu mol O sub(2)/g super(1) FW/h in 2-year-old plants, whereas in 3-year-old plants maximum values of 8 mu mol O sub(2)/g FW/h were determined. The alpha -values reached maximum rates of 1.4 and 0.6 mu mol O sub(2)/g FW/h/( mu mol photons/m super(2)/s) in 2- and 3-year-old plants, respectively. Light compensation point (I sub(c)), dry weight ratios and Chl a contents varied significantly along the length of the blade. Maximum dry:fresh weight ratios were observed in the basal region, with values close to 18%. Distal regions of the 3-year-old plants had significantly higher dry weight content than 2-year-old plants (17.5% and 13%, respectively). Chl a concentrations increased towards the middle regions of the thallus to values close to 0.35 mg Chl a/g FW. The results indicate that some morpho-functional processes in A. mirabilis, especially net photosynthesis and photosynthetic efficiency, are governed by age of the plant, thereby reflecting differences in biomass allocation and size. Our data also confirm the previously demonstrated relationship between growth and seasonal physiological activity that allows A. mirabilis to survive under the low light conditions prevailing in the Antarctic.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor (up)  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0967-0262 ISBN Medium  
  Area Expedition Conference  
  Notes growth curves; size; Thalli; marine flora; thallus Approved no  
  Call Number refbase @ admin @ Gomez++1996 Serial 737  
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Author Haas, C.; Thomas, D.N.; Bareiss, J. url  openurl
  Title Surface properties and processes of perennial Antarctic sea ice in summer Type Journal Article
  Year 2001 Publication Journal of Glaciology Abbreviated Journal J Glaciol  
  Volume 47 Issue 159 Pages 613-625  
  Keywords  
  Abstract Ice-core and snow data from the Amundsen, Bellingshausen and Weddell Seas, Antarctica, show that the formation of superimposed ice and the development of seawater-filled gap layers with high algal standing stocks is typical of the perennial sea ice in summer. The coarse-grained and dense snow had salinities mostly below 0.1ppt. A layer of fresh superimposed ice had a mean thickness of 0.04-0.12 m. Gap layers 0.04-0.08 m thick extended downwards from 0.02 to 0.14 m below the water level. These gaps were populated by diatom standing stocks up to 439 ?g L?¹ chlorophyll a. We propose a comprehensive heuristic model of summer processes, where warming and the reversal of temperature gradients cause major transformations in snow and ice properties. The warming also causes the reopening of incompletely frozen slush layers caused by flood-freeze cycles during winter. Alternatively, superimposed ice forms at the cold interface between snow and slush in the case of flooding with negative freeboard. Combined, these explain the initial formation of gap layers by abiotic means alone. The upward growth of superimposed ice above the water level competes with a steady submergence of floes due to bottom and internal melting and accumulation of snow.  
  Address  
  Corporate Author Thesis  
  Publisher International Glaciological Society Place of Publication Cambridge Editor (up)  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0022-1430 ISBN Medium  
  Area Expedition Conference  
  Notes IPØ/Tvärrminne Approved no  
  Call Number refbase @ admin @ Haas++2001 Serial 742  
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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 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  
  Corporate Author Thesis  
  Publisher Place of Publication Editor (up)  
  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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