Algae. 1999; 14(2): 117-126.

UV-B Effect on Antarctic Diatom Strains

Jae-Shin Kang, Sung-Ho Kang, Jin Hwan Lee

Polar Research Center, Korea
Ocean Research and Development Institute, Department of Biology, Sangmyung University

The flux of biologically harmful mid-ultraviolet radiation (UV-B) increases to the surface of ocean during austral spring and summer time in Antarctica. Consequently, marine microalgae have been adversely affected by UV radiation. Three Antarctic diatoms(Chaetoceros neogracile VanLandingham, Thalassiosira antarctica Comber and Fragilariopsis cylindrus (Grunow) Kridger) were cultured in order to examine change of fluorescence by irradiation time of UV radiation. The fluorescence of C. neogracile and F. cylindrus were inversely correlated with UV radiation time. The fluorescence of T. antarctica unexpectedly increased when the strain was irradiated by UV-B radiation during one hour. It seems that photosynthesis of T. antarctica may be not affected by UV radiation within the first one hour, however the fluorescence repidly decreased when irradiation time is longer than two hours. The three strains which were exposed with UV-B radiation during one to four hours have cultured in normal culture condition during four days. In all cases the fluorescence of UV exposed sample was more decreased than control sample. The increase of UV radiation resulted in the decrease of fluorescence four days later. Our results show that the effects of UV radiation on three diatom species were serious in that photosynthetic organ may be damaged by UV exposure. That is, an effect which the fluorescence is decreased by UV radiation is not a temporal phenomenon but photosynthetic organ is permanently damaged by UV radiation. This experimental evidence shows that exposure to UV-B radiation decreases diatom productivity and causes damage to various forms on species level. Furthermore, evidence suggests that phytoplankton communities confined to near-surface waters in Antarctica will be harmed by increased UV-B radiation, thereby altering the dynamics of Antarctic marine ecosystems.

Keywords : Chaetoceros neogracile, fluorescence, Fragilariopsis cylindrus, mid-ultraviolet radiation(UV-B), Thalassiosira antarctica