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Herborg, L.-M.; Thomas, D.N.; Kennedy, H.; Haas, C.; Dieckmann, G.S. |
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Title |
Dissolved carbohydrates in Antarctic sea ice |
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Journal Article |
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Year |
2001 |
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Antarctic Science |
Abbreviated Journal |
Antarct Sci |
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13 |
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2 |
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119-125 |
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Doc; Mcho; Pcho; sea ice; bacteria; carbon cycling; diatoms; dissolved organic carbon; monocarbohydrates; polycarbohydrates |
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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. |
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no |
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Call Number |
refbase @ admin @ Herborg++2001 |
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743 |
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Kaartokallio, H.; Kuosa, H.; Thomas, D.N.; Granskog, M.A.; Kivi, K. |
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Title |
Biomass, composition and activity of organism assemblages along a salinity gradient in sea ice subjected to river discharge in the Baltic Sea |
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Journal Article |
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2006 |
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Polar Biology |
Abbreviated Journal |
Polar Biol |
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30 |
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2 |
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183-197 |
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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. |
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Springer-Verlag |
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Heidelberg |
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0722-4060 |
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Sampling: Nine stations along a 40km salinity gradient from inner Pojo Bay through the Archipelago to the edge of the open sea |
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refbase @ admin @ Kaartokallio++2006 |
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744 |
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Schnack-Schiel, S.B.; Thomas, D.N.; Haas, C.; Dieckmann, G.S.; Alheit, R. |
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The occurrence of the copepods Stephos longipes (Calanoida) and Drescheriella glacialis (Harpacticoida) in summer sea ice in the Weddell Sea, Antarctica |
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Journal Article |
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Year |
2001 |
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Antarctic Science |
Abbreviated Journal |
Antarctic Sci |
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13 |
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2 |
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150-157 |
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copepods; Drescheriella glacialis; sea ice; seasonality; Stephos longipes |
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In January to March 1997, a RV Polarstern cruise that transected the Weddell Sea resulted in samples being taken in thick pack ice in the south-eastern Weddell Sea and then along the marginal ice edge towards the Antarctic Peninsula. Several ice types were thus sampled over a wide geographic area during late summer/early autumn. Common features of the first warm period was the occurrence of surface ponds, and that many floes had quasi-continuous horizontal gaps, underlying a layer of ice and metamorphic snow. With the onset of cold air temperatures in late February the gaps rapidly refroze. The calanoid copepod Stephos longipes occurred in all habitats encountered and showed highest numbers in the surface ice in summer, in the gap water during both seasons and in the refrozen gap water in autumn. Nauplii outnumbered copepodids in the surface ice and refrozen gap water, while in the gap water copepodids, mainly stages CI-CIII in summer and CII-CIV in autumn, comprised about 70% of the total population. The harpacticoid species Drescheriella glacialis did not occur in all habitats and was missing in surface ponds and new ice. Nauplii of D. glacialis were rarely found in gapwater, but predominated in the refrozen gaps. |
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0954-1020 |
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refbase @ admin @ Schnack-Schiel++2001_2 |
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753 |
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Thomas, D.N.; Baumann, M.E.M.; Gleitz, M. |
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Title |
Efficiency of carbon assimilation and photoacclimation in a small unicellular Chaetoceros species from the Weddell Sea (Antarctica): Influence of temperature and irradiance |
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1992 |
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Journal of Experimental Marine Biology and Ecology |
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J Exp Mar Biol Ecol |
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157 |
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2 |
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195-209 |
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photosynthesis; Psw; Weddell Sea; Chaetoceros; temperature effects; irradiance; light effects; acclimation; respiration; carbon fixation; low temperature; polar waters; Antarctica; water temperature |
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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. |
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Elsevier Science B.V. |
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Amsterdam |
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0022-0981 |
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Call Number |
refbase @ admin @ Thomas++1992 |
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757 |
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Author |
Gleitz, M.; Thomas, D.N. |
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Title |
Physiological responses of a small Antarctic diatom (Chaetoceros sp.) to simulated environmental constraints associated with sea-ice formation |
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Journal Article |
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1992 |
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Marine Ecology Progress Series |
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Mar Ecol Prog Ser |
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88 |
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2-3 |
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271-278 |
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plant physiology; abiotic factors; temperature effects; salinity effects; irradiance; sea ice; growth; photosynthesis; Chaetoceros; Psw; Weddell Sea; simulation |
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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. |
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Inter-Research |
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Oldendorf/Luhe |
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0171-8630 |
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Notes |
Bibliogr.: 38 ref.; Marine |
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Call Number |
refbase @ admin @ Gleitz+Thomas1992 |
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735 |
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