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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Environmental science & technology 26 (1992), S. 1486-1495 
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The influence of temperature on NO 3 - and NH 4 + uptake, and the activity of the assimilatory enzyme NO 3 - reductase (NR) was compared to inorganic C uptake (photosynthesis) in natural assemblages of Antarctic sea-ice microalgae. NO 3 - and NH 4 + uptake reached a maximum between 0.5°–2.0°C and 2.0°–3.0°C, respectively, which was close to that for photosynthesis (2.5°–3.0°C). NR showed a distinctly higher temperature maximum (10.0°–12.0°C) and a lower Q10 value than inorganic N and C transport. Our data imply that, owing to differential temperature characteristics between N transport and N assimilation at in situ temperature (-1.9°C), the incorporation of extracellular NO 3 - into cellular macromolecules, may be limited by transport of NO 3 - into the cell rather than the intracellular reduction of NO 3 - to NH 4 + . Despite differences in temperature maxima between N transport and N assimilation, the overall low temperature maxima of inorganic N metabolism characterizes Antarctic sea-ice microalgae as psychrophilic. Our study is the first to examine the temperature dependence of inorganic N uptake and assimilation in sea-ice microbial communities.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Polar biology 7 (1987), S. 145-151 
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Spectral downwelling irradiance (400–700 nm) was determined in the ice-covered Lake Hoare located in the dry valleys near McMurdo Sound, Antarctica. Full waveband PAR beneath the ice was 〈44μE·m-2·s-1 or 〈3% of surface downwelling irradiance. Maximum light transmission just beneath the 2.6–4 m ice cover, which contained sediments and air bubbles, occurred between 400–500 nm. In the water column below, attenuation of light by phytoplankton in the 400–500 nm region and between 656–671 nm suggested absorption of light by algal pigments.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-5117
    Keywords: Antarctic ; cyanobacteria ; diatoms ; carotenoids ; chlorophylls
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The benthos of a perennially ice-covered Antarctic lake, Lake Hoare, contained three distinct ‘signatures’ of lipophilic pigments. Cyanobacterial mats found in the moat at the periphery of the lake were dominated by the carotenoid myxoxanthophyll; carotenoids: chlorophyll a ratios in this high light environment ranged from 3 to 6.8. Chlorophyll c and fucoxanthin, pigments typical of golden-brown algae, were found at 10 to 20 m depths where the benthos is aerobic. Anaerobic benthic sediments at 20 to 30 m depths were characterized by a third pigment signature dominated by a carotenoid, tentatively identified as alloxanthin from planktonic cryptomonads, and by phaeophytin b from senescent green algae. Pigments were not found associated with alternating organic and sediment layers. As microzooplankton grazers are absent from this closed system and transformation rates are reduced at low temperatures, the benthos beneath the lake ice appears to contain a record of past phytoplankton blooms undergoing decay.
    Type of Medium: Electronic Resource
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