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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 (up) Amsterdam Editor  
  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 Granskog, M.; Kaartokallio, H.; Kuosa, H.; Thomas, D.N.; Vainio, J. url  doi
openurl 
  Title Sea ice in the Baltic Sea – A review Type Journal Article
  Year 2006 Publication Estuarine, Coastal and Shelf Science Abbreviated Journal Estuar Coast Shelf Sci  
  Volume 70 Issue 1-2 Pages 145-160  
  Keywords sea ice; Baltic Sea; biogeochemistry; plankton; seasons  
  Abstract Although the seasonal ice cover of the Baltic Sea has many similarities to its oceanic counterpart in Polar Seas and Oceans, there are many unique characteristics that mainly result from the brackish waters from which the ice is formed, resulting in low bulk salinities and porosities. In addition, due to the milder climate than Polar regions, the annual maximum ice extent is highly variable, and rain and freeze-melt cycles can occur throughout winter. Up to 35% of the sea ice mass can be composed from metamorphic snow, rather than frozen seawater, and in places snow and superimposed ice can make up to 50% of the total ice thickness. There is pronounced atmospheric deposition of inorganic nutrients and heavy metals onto the ice, and in the Bothnian Bay it is estimated that 5% of the total annual flux of nitrogen and phosphorus and 20–40% of lead and cadmium may be deposited onto the ice fields from the atmosphere. It is yet unclear whether or not the ice is simply a passive store for atmospherically deposited compounds, or if they are transformed through photochemical processes or biological accumulation before released at ice and snow melt.As in Polar sea ice, the Baltic ice can harbour rich biological assemblages, both within the ice itself, and on the peripheries of the ice at the ice/water interface. Much progress has been made in recent years to study the composition of these assemblages as well as measuring biogeochemical processes within the ice related to those in underlying waters. The high dissolved organic matter loading of Baltic waters and ice result in the ice having quite different chemical characteristics than those known from Polar Oceans. The high dissolved organic material load is also responsible in large degree to shape the optical properties of Baltic Sea ice, with high absorption of solar radiation at shorter wavelengths, a prerequisite for active photochemistry of dissolved organic matter.Land-fast ice in the Baltic also greatly alters the mixing characteristics of river waters flowing into coastal waters. River plumes extend under the ice to a much greater distance, and with greater stability than in ice-free conditions. Under-ice plumes not only alter the mixing properties of the waters, but also result in changed ice growth dynamics, and ice biological assemblages, with the underside of the ice being encased, in the extreme case, with a frozen freshwater layer.There is a pronounced gradient in ice types from more saline ice in the south to freshwater ice in the north. The former is characteristically more porous and supports more ice-associated biology than the latter. Ice conditions also vary considerably in different parts of the Baltic Sea, with ice persisting for over half a year in the northernmost part of the Baltic Sea, the Bothnian Bay. In the southern Baltic Sea, ice appears only during severe winters.  
  Address Granskog: Arctic Centre, University of Lapland, P.O. Box 122, FI-96101 Rovaniemi, Finland  
  Corporate Author Thesis  
  Publisher Elsevier Science BV Place of Publication (up) Amsterdam Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0272-7714 ISBN Medium  
  Area Baltic Sea Expedition Conference  
  Notes Review Approved no  
  Call Number refbase @ admin @ Granskog++2006 Serial 738  
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Author Thomas, D.N. url  doi
openurl 
  Title Photosynthetic microbes in freezing deserts Type Journal Article
  Year 2005 Publication Trends in Microbiology Abbreviated Journal Trends Microbiol  
  Volume 13 Issue 3 Pages 87-88  
  Keywords  
  Abstract Polar deserts are not devoid of life despite the extreme low temperature and scarcity of water. Recently, patterned stone fields – caused by periglacial activity – have been surveyed in the Arctic and Antarctic. It was found that the productivity of the cyanobacteria and algae (hypoliths) that colonise the underside of the stones is strongly related to the pattern of the stones. The hypolith assemblages were in some cases as productive as lichens, bryophytes and plants that resided nearby.  
  Address  
  Corporate Author Thesis  
  Publisher Elsevier Science B.V. Place of Publication (up) Amsterdam Editor  
  Language English Summary Language English Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0966-842X ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number refbase @ admin @ Thomas2005 Serial 755  
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Author Thomas, D.N.; Baumann, M.E.M.; Gleitz, M. url  openurl
  Title Efficiency of carbon assimilation and photoacclimation in a small unicellular Chaetoceros species from the Weddell Sea (Antarctica): Influence of temperature and irradiance Type Journal Article
  Year 1992 Publication Journal of Experimental Marine Biology and Ecology Abbreviated Journal J Exp Mar Biol Ecol  
  Volume 157 Issue 2 Pages 195-209  
  Keywords photosynthesis; Psw; Weddell Sea; Chaetoceros; temperature effects; irradiance; light effects; acclimation; respiration; carbon fixation; low temperature; polar waters; Antarctica; water temperature  
  Abstract It is well established that Antarctic phytoplankton and sea-ice algae are able to thrive at low temperatures and it has been proposed that a reduction in respiration may be important in enabling them to do this. This possibility was studied in an Antarctic clone of a small unicellular Chaetoceros species isolated from the Weddell Sea (Antarctica), using comparative measurements of C assimilation during long- and short-term incubation series over a range of temperatures (-1.5 to 4 °C) at two irradiances (5 and 55 µmol m?²/s). Even though doubling times varied considerably, the total amount of C assimilated per cell per generation time was similar at each of the temperature and light conditions. However, over one cell cycle, significant respiratory C losses were determined by divergences in C assimilation patterns between cumulative and long-term incubations at both light intensities at 0 and 4 °C. At -1.5 °C, insignificant C losses were recorded. No significant extracellular release of dissolved organic material (DOC) was observed.  
  Address  
  Corporate Author Thesis  
  Publisher Elsevier Science B.V. Place of Publication (up) Amsterdam Editor  
  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 @ Thomas++1992 Serial 757  
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Author Gomez, I.; Thomas, D.N.; Wiencke, C. openurl 
  Title Longitudinal profiles of growth, photosynthesis and light independent carbon fixation in the Antarctic brown alga Ascoseira mirabilis Type Journal Article
  Year 1995 Publication Botanica Marina Abbreviated Journal Bot Mar  
  Volume 38 Issue Pages 157-164  
  Keywords  
  Abstract Thallus growth, photoynthetic oxygen evolution and rates of carbon fixation were determinedalong the lamina of the endemic Antarctic brown alga Ascoseira mirabilis (Ascoseirales), grown under simulated Antarctic condtions. The meristem is basally located and forms new blade tiddue under spring-conditions. Light saturated net photosynthesis (P,ax), measures as O? production, was higher in ther intermediate region of the plant (9..8 µmol O? g?¹ fw h?¹). In general, photosynthetic parameters such as dark respiration, gross photosynthesis, photosynthetic efficiency (?) and photosynthetic light compensation (Ic) increased significantly towards the distal region. Carbon-fixation in A. mirabilis also showed thllus-dependent variation. Rates of light and light independent (dark) carbon fixation increased towards the distal regions ranging between 7.6-9.5 and 1.2-2.0 µmol C g?¹ fw h?¹ respectively. The percentage of light independent carbon fixation (in relation to light ¹?C-fixation) also increased from the basal to the distal parts reaching 24% in the distal region of the thallus. he contents of Chl a and Chl c, were close to 0.37 and 0.14 mg g?¹ fw respectively and were notably uniform along the lamina. The results indicate that the formation of the blade by a basal meristem and the increase of light carbon fixation rates from base to the distal regions in A. mirabilis are similar compared with certain Laminariales, especially members of the genus Laminaria. However, light independent carbon fixation is highest in the meristem of Laminaria, opposite to the results obtained here for A. mirabilis  
  Address  
  Corporate Author Thesis  
  Publisher de Gruyter Place of Publication (up) Berlin, New York 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 @ Gomez++1995 Serial 736  
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