Is UV-B radiation affecting charophycean algae in shallow freshwater systems?

Authors

  • Nancy V. J. De Bakker,

    Corresponding author
    1. Institute of Ecological Science, Department of Systems Ecology, Vrije Universiteit, de Boelelaan 1085, 1081 HV Amsterdam, the Netherlands;
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  • P. M. Van Bodegom,

    1. Institute of Ecological Science, Department of Systems Ecology, Vrije Universiteit, de Boelelaan 1085, 1081 HV Amsterdam, the Netherlands;
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  • W. H. Van De Poll,

    1. University of Groningen, Department of Marine Biology, PO Box 14, 9750 AA Haren, the Netherlands;
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  • P. Boelen,

    1. Institute of Ecological Science, Department of Systems Ecology, Vrije Universiteit, de Boelelaan 1085, 1081 HV Amsterdam, the Netherlands;
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  • E. Nat,

    1. National Information Centre on Charophytes, National Herbarium Netherlands Branch Leiden, Department of Algology, PO Box 9514, 2300 RA Leiden, the Netherlands
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  • J. Rozema,

    1. Institute of Ecological Science, Department of Systems Ecology, Vrije Universiteit, de Boelelaan 1085, 1081 HV Amsterdam, the Netherlands;
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  • R. Aerts

    1. Institute of Ecological Science, Department of Systems Ecology, Vrije Universiteit, de Boelelaan 1085, 1081 HV Amsterdam, the Netherlands;
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Author for correspondence: N.V.J. de Bakker Tel: +31 20 5986964 Fax: +31 20 5897123 Email: nancy.de.bakker@ecology.falw.vu.nl

Summary

  • • The objective of this study was to determine the effects of UV-B radiation on charophycean algae under natural conditions, since charophytes enhance water transparency in freshwater systems and levels of UV-B radiation have increased by ozone depletion.
  • • Potential and actual UV-B effects were studied by combining a glasshouse experiment in which plants were exposed to various levels of UV-B radiation and field measurements in two freshwater systems dominated by charophytes in the Netherlands.
  • • The glasshouse experiment showed that charophytes were sensitive to UV-B radiation. UV-B radiation negatively affected growth, while it increased levels of DNA damage in Chara aspera. Moreover, the charophytes did not seem to develop UV-B screens to protect against UV-B radiation since no increase in UV-B absorbing compounds was found.
  • • At field conditions, both spectroradiometrical measurements and DNA dosimeters showed that UV-B radiation was attenuated quickly in both freshwater systems, indicating that UV-B does not reach the submerged charophyte vegetation. However, specific conditions, like fluctuating water tables, may result in UV-B exposure to charophytes for certain periods annually.

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