The Responses Of Spirulina Maxima And Chlorella Minutensis To Enchanced UVB And The Enriched Organic Substances

Effects of algae on natural environment(especiaaly aquatic environment) are obvious. On the earth, algae contributes about half of the photosynthetic productivity through CO2 assimilation, so algae play an important role in the diminishing of CO2 amount, which can induce reen house effect Increasing of incident UVB radiation (280-320nm)has been observed accompaning ozone depletion in recent years. UVB radiation has many harmful effect on algae,while algae can adapt to it within certain range. In this study, we compared the UV adaptation ability between two species of algae( Spirulina maxima and Chlorella) during short-term and longer- term UV treatments, We investigated their chlorophyll fluorescence kinetics in order to compare the maximum photochemical eficiency of PS II in the dark-adapted state (Fv/FM) and the quantum yield of PS II electron transport (A F/FM). We also investigated the secretion of UVB absorbing substance and SOD activity to compare the difference of their adaptation mechanism. The results of the short-term treatment and longer-term treatment showed: 0 FV/FM and A F/FM of the two species were both substiantially inhibited after short-term treatment under different UVB irradiance, while FV/FM and A F/FM of Spirulina maxima were inhibited more than that of Chlorella minutensis, moreover, the decreases of Fv/FM and A F/FM of Spirulia maxima was positively correlated with UVB irradiance. The results exhibited that there was no difference in the secretion of UVB absorbing substances and SOD activity in two species after short-time treatment, but the SOD activity of Spirulina maxima was higher than that of Chlorella minutensis. The FV/FM and A F/FM of the two species have apparent difference after long erm treatment in the same UVB irradiance.V/M and A F/FM of Spirulina maxima increased drastically followed by a gradual decrease, in contrast, the two parameters in Chlorella minutensis gradually decreased. Within the treatment time, the secretion of UVB absorbing substances and SOD activity increased gracually in Spirulina, while there are no change in Chlorel/a. Organic substances can affect the growth and reproduction of algae, but the responses of various algae to one kind of organec substance are different even at the same concentration. In this study, The growth of the two species affected by glucose and protein was investigated.The results demostrated that both glucose and protein can promote the growth of the two species, moreover , the promotion in Spirulina is substiantially larger than that in Chlorella.The difference of promotion may affect the algal population construction in aquatic ecosystem. Accompanied by the increasing of UVB radiation and organic pollutants, we estimate that cyanobacteria may become dominant in aquatic ecosystem. Because many species of cyanobacteria can produce cyanobacterial toxins, which have harmful effects on human health. So more reseach in this field should be conducted.