EFFECT OF UV-B RADIATION ON CILIATED PROTOZOA - Environmental UV Radiation: Impact on Ecosystems and Human Health and Predictive Models - page 237

radiation, so that we cannot exclude the hypothesis that in natural conditions the repair
mechanisms could work more efficiently. However, it was observed that light-
dependent photolyase DNA repair can take place under an irradiance of 15 W/m 238 ,
comparable to that reported above.

1.E+02

1.E+01

1.E+00

1.E-01

1.E-02

1.E-03

270 290 310 330 350

Wavelength [nm]

Fig. 14. UV action spectrum (determined under polychromatic irradiation conditions) for the
inhibition of positive phototaxis in Ophryoglena flava .

The UV action spectrum for the phototaxis inhibition in Ophryoglena flava (see
Fig. 14) clearly shows that the damage increases exponentially with decreasing
wavelength. Thus, a further depletion of the ozone hole, causing shorter wavelengths to
reach the Earth surface, could significantly increase the risk of damage to aquatic
microorganisms in natural ecosystems.

References

1. Marangoni R, Martini B, Colombetti G (1997) Effects of UV on ciliates. In The Effects of Ozone
Depletion in Aquatic Ecosystems (D-P Häder, ed.), R.G. Landes Company, Georgetown, and Academic
Press, San Diego, pp. 229-246.
2. Dahlback A, Henriksen T, Larsen SH, Stamnes K (1989) Biological UV-doses and the effect of an ozone
layer depletion. Photochem. Photobiol., 49: 621-625.
3 Frederick JE (1990) Trends in atmospheric ozone and ultraviolet radiation: mechanisms and observations
for the northern hemisphere. Photochem Photobio. 51: 757-763.
4. Frederick JE (1993) Ultraviolet sunlight reaching the earth's surface: a review of recent research.
Photochem Photobiol 57: 175-178.
5. Giese AC (1938) Differential scusceptibility of a number of protozoans to ultraviolet radiations. J Cell
Comp Physiol 12: 129-138.
6. Giese AC (1945) The ultraviolet action spectrum for retardation of division of Paramecium . J Cell Comp
Physiol 26: 47-55.
7. Hirshfield H, Giese AC (1953) Ultraviolet radiation effects on growth processes of Blepharisma
undulans . Exp Cell Res 4: 283-294.