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 rapidly 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.

The effects of acidification on growth of Spirogyra spp. (S, crassa, S. setiformis and S. ternata) have been investigated under the range of pH (4.0-10.0) and temperatures (10-30℃) in the laboratory. All the filaments exposed to pH 4.0 showed abnormal morphology, such as bulging or chloroplast deterioration, after two days of incubation. However, the plants exhibited some variations in the survival rate under the culture conditions of pH 5.0-10.0. Maximum growth of S. crassa was at pH 9.0 and 25℃, S. setiformis at pH 7.0-8.0 and 20℃, and S. ternata at pH 7.0 and 25℃, respectively. Maximum elongation of filaments after 14 days of incubation were different among species: 70 ㎜ of S. crassa, 45 ㎜ of S. setiformis and 88 ㎜ of S. ternata. In general, the plants showed decreased filament growth with decreasing pH. Our results indicated that acid water of pH 4-5 greatly inhibits the growth of Spirogyra spp.

An antihypercholesterolemic effect was observed by the intraperitoneal injection of the seaweed extract into mouse. Hypercholesterolemia was induced by intraperitoneal injection of Triton WR-1339 (600 ㎍/g-body weight) into a mouse. Maximum level of blood cholesterol was reached at 20 hours after Triton injection. By simultaneous injection of the seaweed extract (30 ㎍/ g-body weight) with the Triton into each right and left sides of the peritoneal cavity, five of the 27 seaweed species showed antihypercholesterolemic effect. Among them, the Colpomenia bullosa extract has been found to decrease the levels of total cholesterol and low density lipoprotein to 38% and 21%, compared to Triton injection only. For histochemical changes, hepatic tissues obtained at 40 hours after injection of the Triton and C. bullosa extract were fixed in fromol-calcium solution. In C. bullosa extract group, numbers of cholesterol particles decreased in the portal space of the liver. This indicates that the accumulation of cholesterol, caused by Triton, was prevented by the antihypercholesterolemic effect of the seaweed C. bullosa extract.