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Author |
Gomez, I.; Thomas, D.N.; Wiencke, C. |
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Title |
Longitudinal profiles of growth, photosynthesis and light independent carbon fixation in the Antarctic brown alga Ascoseira mirabilis |
Type |
Journal Article |
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Year |
1995 |
Publication |
Botanica Marina |
Abbreviated Journal |
Bot Mar |
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Volume |
38 |
Issue |
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Pages |
157-164 |
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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 |
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de Gruyter |
Place of Publication |
Berlin, New York |
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Call Number |
refbase @ admin @ Gomez++1995 |
Serial |
736 |
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Author |
Granskog, M.A.; Virkkunen, K.; Thomas, D.N.; Ehn, J.; Kola, H.; Martma, T. |
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Title |
Chemical properties of brackish water ice in the Bothnian Bay, the Baltic Sea |
Type |
Journal Article |
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Year |
2004 |
Publication |
Journal of Glaciology |
Abbreviated Journal |
J Glaciol |
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Volume |
50 |
Issue |
169 |
Pages |
292-302 |
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Keywords |
Dependent Solute Redistribution; Dissolved Organic Matter; Phase Boundary; Sulfate; Binding; Summer; Oxygen; Core; Gulf |
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Abstract |
The behavior of majors, δ18O, dissolved organic carbon (DOC) and trace elements was studied during the initial freezing of low-saline water (3 practical salinity units) in a freezing experiment. Samples were also collected from first-year sea ice from pack ice in the Bothnian Bay, northern Baltic Sea. During initial ice formation, the major-ion ratios in sea ice indicated variable behavior, with some ions showing relative enrichment (sulfate, calcium and magnesium), conservative behavior (sodium) or relative depletion (potassium) compared to sea water at the same salinity DOC, iron and aluminum showed enrichment in the ice, while zinc was depleted to salinity. Lead was detected in surface snow-ice layers only, implying atmospheric accumulation. First-year sea ice, with a variable growth and thermal history, showed behavior for major ions similar to that observed in new ice. However, for trace elements the picture was much more complicated, most likely due to active secondary processes such as atmospheric supply and biological activity. Ice growth has a potential impact on the chemical budgets and cycling of some elements, especially those which are selectively rejected/retained during sea-ice formation, particularly in the shallow parts of the Bothnian Bay covered with a land-fast ice cover. |
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Address |
Granskog: Univ Helsinki, Dept Phys Sci, Div Geophys, FIN-00014 Helsinki, Finland |
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International Glaciological Society |
Place of Publication |
Cambridge |
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0022-1430 |
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Baltic Sea; Bothnian Bay |
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ISI:000227720900014 |
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no |
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Call Number |
refbase @ admin @ Granskog++2004 |
Serial |
741 |
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Author |
Kennedy, H.; Thomas, D.N.; Kattner, G.; Haas, C.; Dieckmann, G.S. |
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Title |
Particulate organic matter in Antarctic summer sea ice: concentration and stable isotopic composition |
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Journal Article |
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Year |
2002 |
Publication |
Marine Ecology Progress Series |
Abbreviated Journal |
Mar Ecol Prog Ser |
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Volume |
238 |
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Pages |
1-13 |
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Keywords |
Pom; Anarctic sea ice; ice microalgae; carbon isotopic composition |
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Abstract |
The chemical and isotopic data from sea ice collected over a wide area of the Weddell Sea, Antarctica, during the austral summer/early autumn illustrate the range of environmental conditions under which ice algae grow. A range of ice types and features were sampled including intact and layered ice floes and surface ponds. Sea ice communities were found in all these environments but the highest biomasses were found either at the base of ice floes, or in the interior of layered floes with quasi-continuous horizontal gaps at or shortly below the water level. In the layered floes, particulate organic carbon (POC) measured in the ice layer immediately overlying the gap water (280 to 6014 µmol dm?³) was in excess of what would be predicted if algal growth had occurred in a closed environment. The chemical composition of the gap water was strongly affected by biological activity in the overlying ice, which acts as a physical support for the algae retained within its matrix. The lowest range of POC (27 to 739 µmol dm?³) conformed to predictions of algal growth in a closed system and samples were collected from the interior of ice floes where there was essentially no potential for nutrient exchange. The surface ponds displayed nitrate (NO³?) exhaustion and total dissolved inorganic carbon (?CO?) reductions consistent with nutrient limited algal growth. The stable carbon isotopic composition of the particulate organic matter (POM) across all habitat types sampled (?¹³CPOC -10.0 to -27.3?) displayed a wide range but was much less variable than the range of POC concentrations might have implied. The assumption that the highest biomass of algae in sea ice will result in the most positive ?¹³CPOC values cannot be generally applied. The isotopic composition of dissolved inorganic carbon (?¹³C?CO?) in gap waters and surface ponds varied from 0.15 to 3.0? and was shown to be commensurate with the changes predicted from NO³? deficits caused by algal growth. |
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Inter-Research |
Place of Publication |
Oldendorf/Luhe |
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0171-8630 |
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no |
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Call Number |
refbase @ admin @ Kennedy++2002 |
Serial |
746 |
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Author |
Stedmon, C.A.; Thomas, D.N.; Granskog, M.; Kaartokallio, H.; Papadimitriou, S.; Kuosa, H. |
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Title |
Characteristics of dissolved organic matter in Baltic coastal sea ice: allochthonous or autochthonous origins? |
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Journal Article |
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Year |
2007 |
Publication |
Environmental Science & Technology |
Abbreviated Journal |
Environ Sci Technol |
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Volume |
41 |
Issue |
21 |
Pages |
7273-7279 |
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Keywords |
Carbon/analysis; *Humic Substances; Ice Cover/*chemistry; Nitrogen/analysis; Oceans and Seas; Spectrometry, Fluorescence |
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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. |
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Address |
Department of Marine Ecology, National Environmental Research Institute, University of Aarhus, Frederiksborgvej 399, 4000 Roskilde, Denmark. cst@dmu.dk |
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English |
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0013-936X |
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Notes |
PMID:18044499 |
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Call Number |
refbase @ user @ |
Serial |
12979 |
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Author |
Thomas, D.N.; Dieckmann, G.S. |
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Title |
Antarctic sea ice – a habitat for extremophiles |
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Journal Article |
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Year |
2002 |
Publication |
Science |
Abbreviated Journal |
Science |
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Volume |
295 |
Issue |
5555 |
Pages |
641-644 |
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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 |
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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. |
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American Association for the Advancement of Science |
Place of Publication |
Washington, DC |
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0036-8075 |
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Review |
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no |
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Call Number |
refbase @ admin @ Thomas+Dieckmann2002_2 |
Serial |
759 |
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