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  • 2000-2004  (3)
  • 1
    Electronic Resource
    Electronic Resource
    The Effect of Bioaccumulated Selenium on Mortalities and Deformities in the Eggs, Larvae, and Fry of a Wild Population of Cutthroat Trout (Oncorhynchus clarki lewisi) (2000)
    Springer
    Archives of environmental contamination and toxicology 39 (2000), S. 46-52 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract To determine if elevated concentrations of waterborne selenium (Se), caused by coal mining, in the Elk River in southeastern British Columbia, may be causing reproductive or teratogenic effects in wild cutthroat trout (Oncorhynchus clarki lewisi), fertilized eggs from exposed and reference fish were raised in the laboratory. Eggs from each female were reared separately and the percent mortalities and deformities were related to the selenium content of the eggs. Selenium concentrations in females from the exposed site were highest in the liver (36.6 ± 22.5 μg/g dry weight, range: 18.3 to 114), followed by the eggs (21.0 ± 18.3 μg/g, range: 8.7 to 81.3) and the muscle (12.5 ± 7.7 μg/g, range: 6.7 to 41). Despite these elevated egg Se concentrations, there was no significant effect on fertilization; time to hatch; percent hatch; or egg, larvae, and fry deformities or mortalities. Reproductive failure and embryonic terata have been reported at much lower egg Se concentrations in other fish species. The lack of any toxic response in this study may be due to an evolved tolerance to higher tissue Se concentrations in a population of fish living in a seleniferous river system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002440010078
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The Energy Supply to X-ray Bright Points (2000)
    Springer
    Solar physics 196 (2000), S. 137-156 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract X-ray bright points (XBPs) are usually assumed to be isolated structures in the solar atmosphere that are powered exclusively by magnetic reconnection. We analyse a large XBP that does not satisfy this assumption. The XBP is observed to be connected to an active region approximately 280 000 km away by a magnetic loop. We find that the soft X-ray intensity and thermal energy of the XBP are very sensitive to the existence of the magnetic loop. Both the intensity and energy decrease significantly at the times when the loop disappears, indicating that the loop is a medium for energy transfer from the active region to the XBP. We deduce that the mechanism for the energy transfer is most likely to be Alfvén or fast-mode magnetoacoustic waves created by photospheric motions in the active region. These waves can dissipate energy at the density gradient between the XBP and the loop via phase mixing or resonant absorption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005218932680
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Comparative regeneration ecology of three leguminous timber species in a Bolivian tropical dry forest (2000)
    Springer
    New forests 20 (2000), S. 45-64 
    Details
    ISSN: 1573-5095
    Keywords: Anadenanthera ; Bolivia ; Centrolobium ; Copaifera ; regeneration ; tropical dry forests
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A comparative study of the regeneration ecology ofthree lesser-known leguminous timber species wasconducted in the seasonally dry forests of SantaCruz, Bolivia to determine species regenerationstrategies and make silvicultural recommendationsfor these species. The study included arepresentative from each subfamily of Leguminosae:Anadenanthera colubrina (Vell. Conc.) Benth.(Mimosaceae), Copaifera chodatiana Kunth.(Caesalpinaceae), and Centrolobium microchaeteC. Martius (Fabaceae). After production in themid-late dry season, seeds of all species sufferedhigh (〉30%) rates of predation. For seedssurviving predation, Anadenanthera germinatedwithin three days after the first rains and a highgermination capacity (82%), but most seedlings diedfrom inadequate light or during subsequent periodsof drought. Copaifera germinated more slowlybut had high germination capacity (85%). Centrolobium had very low germination capacity(4%) and germinative energy. Most successfulregeneration of Centrolobium occurred viasprouting from damaged roots on or near loggingroads where it had a density of 261 root sprouts/ha.Anadenanthera regenerated best from seedin areas with soil disturbance or burning. Theregeneration of these species will likely increaseunder more intensive logging and/or post-harvestcompetition control treatments in logging gaps. Themore shade-tolerant Copaifera is most suitedto the current regime of light selective logging,but all three species are likely to be responsive topost-harvest competition control treatments. Impacts of controlled and natural fire were mixed,but generally seedling regeneration and growth wereeither not significantly affected or were increasedby fire.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006735819449
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    Paper (German National Licenses)
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