title: Is UV-B radiation affecting charophycean algae in shallow freshwater systems?
abstract: 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.
authors.affiliation: Institute of Ecological Science, Department of Systems Ecology, Vrije Universiteit, de Boelelaan 1085, 1081 HV Amsterdam, the Netherlands. nancy.de.bakker@ecology.falw.vu.nl
authors.forename: Nancy V J
authors.initials: NV
authors.lastname: de Bakker
authors.forename: P M
authors.initials: PM
authors.lastname: van Bodegom
authors.forename: W H
authors.initials: WH
authors.lastname: van de Poll
authors.forename: P
authors.initials: P
authors.lastname: Boelen
authors.forename: E
authors.initials: E
authors.lastname: Nat
authors.forename: J
authors.initials: J
authors.lastname: Rozema
authors.forename: R
authors.initials: R
authors.lastname: Aerts
mesh_terms: D044784:Chara / Q000528:radiation effects*; D017753:Ecosystem; D004780:Environment, Controlled; D005618:Fresh Water; D014466:Ultraviolet Rays