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Author Stedmon, C.A.; Thomas, D.N.; Granskog, M.; Kaartokallio, H.; Papadimitriou, S.; Kuosa, H. url  openurl
  Title Characteristics of dissolved organic matter in Baltic coastal sea ice: allochthonous or autochthonous origins? Type Journal Article
  Year 2007 Publication Environmental Science & Technology Abbreviated Journal Environ Sci Technol  
  Volume 41 Issue (up) 21 Pages 7273-7279  
  Keywords Carbon/analysis; *Humic Substances; Ice Cover/*chemistry; Nitrogen/analysis; Oceans and Seas; Spectrometry, Fluorescence  
  Abstract The origin of dissolved organic matter (DOM) within sea ice in coastal waters of the Baltic Sea was investigated using parallel factor (PARAFAC) analysis of DOM fluorescence. Sea ice DOM had distinctly different fluorescence characteristics than that of the underlying humic-rich waters and was dominated by protein-like fluorescence signals. PARAFAC analysis identified five fluorescent components, all of which were present in both sea ice and water. Three humic components were negatively correlated to salinity and concluded to be terrestrially derived material. Baltic Sea ice DOM was found to be a mixture of humic material from the underlying water column incorporated during ice formation and autochthonous material produced by organisms within the ice. Dissolved organic carbon (DOC) and nitrogen (DON) concentrations were correlated to the humic fluorescence, indicating that the majority of the organic carbon and nitrogen in Baltic Sea ice is bound in terrestrial humic material trapped within the ice. This has implications for our understanding of sea ice carbon cycling in regions influenced by riverine input (e.g., Baltic and Arctic coastal waters), as the susceptibility of DOM to degradation and remineralization is largely determined by its source.  
  Address Department of Marine Ecology, National Environmental Research Institute, University of Aarhus, Frederiksborgvej 399, 4000 Roskilde, Denmark. cst@dmu.dk  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0013-936X ISBN Medium  
  Area Expedition Conference  
  Notes PMID:18044499 Approved no  
  Call Number refbase @ user @ Serial 12979  
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Author Hulatt, C.J.; Thomas, D.N. url  doi
openurl 
  Title Dissolved organic matter (DOM) in microalgal photobioreactors: a potential loss in solar energy conversion? Type Journal Article
  Year 2010 Publication Bioresource Technology Abbreviated Journal Bioresour Technol  
  Volume 101 Issue (up) 22 Pages 8690-8697  
  Keywords Bioreactors/*microbiology; Chlorella vulgaris/*physiology; Culture Media/chemistry; *Electric Power Supplies; Energy Transfer; Organic Chemicals/*chemistry/*metabolism; Photochemistry/*instrumentation; Solubility  
  Abstract Microalgae are considered to be a potential alternative to terrestrial crops for bio-energy production due to their relatively high productivity per unit area of land. In this work we examined the amount of dissolved organic matter exuded by algal cells cultured in photobioreactors, to examine whether a significant fraction of the photoassimilated biomass could potentially be lost from the harvestable biomass. We found that the mean maximum amount of dissolved organic carbon (DOC) released measured 6.4% and 17.3% of the total organic carbon in cultures of Chlorellavulgaris and Dunaliella tertiolecta, respectively. This DOM in turn supported a significant growth of bacterial biomass, representing a further loss of the algal assimilated carbon. The release of these levels of DOC indicates that a significant fraction of the photosynthetically fixed organic matter could be lost into the surrounding water, suggesting that the actual biomass yield per hectare for industrial purposes could be somewhat less than expected. A simple and inexpensive optical technique, based on chromophoric dissolved organic matter (CDOM) measurements, to monitor such losses in commercial PBRs is discussed.  
  Address School of Ocean Sciences, College of Natural Sciences, Bangor University, Menai Bridge, Anglesey, UK. osp418@bangor.ac.uk  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language English Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0960-8524 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:20634058 Approved no  
  Call Number refbase @ user @ Serial 12981  
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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 Aquat Microb Ecol  
  Volume 29 Issue (up) 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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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 (up) 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 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 Underwood, G.J.C.; Aslam, S.N.; Michel, C.; Niemi, A.; Norman, L.; Meiners, K.M.; Laybourn-Parry, J.; Paterson, H.; Thomas, D.N. url  doi
openurl 
  Title Broad-scale predictability of carbohydrates and exopolymers in Antarctic and Arctic sea ice Type Journal Article
  Year 2013 Publication Proceedings of the National Academy of Sciences of the United States of America Abbreviated Journal Proc Natl Acad Sci U S A  
  Volume 110 Issue (up) 39 Pages 15734-15739  
  Keywords Antarctic Regions; Arctic Regions; Biopolymers/*analysis; Carbohydrates/*analysis; Ice Cover/*chemistry; Models, Chemical; Molecular Weight; Solubility; algae; biogeochemistry; global relationships; microbial  
  Abstract Sea ice can contain high concentrations of dissolved organic carbon (DOC), much of which is carbohydrate-rich extracellular polymeric substances (EPS) produced by microalgae and bacteria inhabiting the ice. Here we report the concentrations of dissolved carbohydrates (dCHO) and dissolved EPS (dEPS) in relation to algal standing stock [estimated by chlorophyll (Chl) a concentrations] in sea ice from six locations in the Southern and Arctic Oceans. Concentrations varied substantially within and between sampling sites, reflecting local ice conditions and biological content. However, combining all data revealed robust statistical relationships between dCHO concentrations and the concentrations of different dEPS fractions, Chl a, and DOC. These relationships were true for whole ice cores, bottom ice (biomass rich) sections, and colder surface ice. The distribution of dEPS was strongly correlated to algal biomass, with the highest concentrations of both dEPS and non-EPS carbohydrates in the bottom horizons of the ice. Complex EPS was more prevalent in colder surface sea ice horizons. Predictive models (validated against independent data) were derived to enable the estimation of dCHO concentrations from data on ice thickness, salinity, and vertical position in core. When Chl a data were included a higher level of prediction was obtained. The consistent patterns reflected in these relationships provide a strong basis for including estimates of regional and seasonal carbohydrate and dEPS carbon budgets in coupled physical-biogeochemical models, across different types of sea ice from both polar regions.  
  Address School of Biological Sciences, University of Essex, Colchester, Essex CO4 3SQ, United Kingdom  
  Corporate Author Thesis  
  Publisher National Academy of Sciences Place of Publication Washington, DC Editor  
  Language English Summary Language English Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0027-8424 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:24019487; PMCID:PMC3785782 Approved no  
  Call Number refbase @ user @ Serial 17491  
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