Is UV-B radiation affecting charophycean algae in shallow freshwater systems?
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.
de Bakker
Nancy V J
NV
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
van Bodegom
P M
PM
van de Poll
W H
WH
Boelen
P
P
Nat
E
E
Rozema
J
J
Aerts
R
R
D044784:Chara / Q000528:radiation effects*; D017753:Ecosystem; D004780:Environment, Controlled; D005618:Fresh Water; D014466:Ultraviolet Rays