Study On Physiological Changes Of Different Algae Under UV-B Radiation Treatment

UV-B radiation enhancement can cause many environmental problems. Algae have different mechanisms to adapt UV-B enhancement. In this study, 5 algae were chosen as experimental materials, their physiological and biochemical responses were studied under both short time and longer period of UV-B treatment. Results showed that these algae have different ability in resisting UV-B enhancement: Spirulina plalensis >Nanochloropsis sp>Chaetoceros gracilis> Proroceatrum micans >Phaeocystis globosa scherffel.UV can destroy Ch1a, making Ch1a content decrease. Carotenoids content increased in algae Spirulina plalensis and Nanochloropsis sp under lower dosage of UV-B treatment. The result proved that Carotenoids maybe play important roles in photoprotection of algae. Carotenoids can make Chla return from excited state to ground state by direct or un-direct quenching, in order to prevent algae from photooxidation. On the other hand, it was indicated that polysaccharides have functions in resisting UV. Spirulina plalensis can accumulate both cellular and extracellular polysaccharides during UV treatment, it showed highest UV resistant ability; Nanochloropsis sp also can accumulate cellular polysaccharides, while extracellular polysaccharides reduced; the cellular polysaccharides content of Phaeocystis globosa scherffel decreased and extracellular polysaccharides content did not increased markedly, showing lowest UV resistant ability. Spirulina plalensis showed no cellular damage during the longer period of UV-B enhancement treatment, that may provide a new way for polysaccharides production. From results, we can presume that UV-B enhancement may be one of factors, which cause red tide. When weather changes, causing UV-B decreased, some UV-susceptible algae would become dominant, it grow fast and eventually resulting in red tide formation.