Influence of UV-B irradiation on the interspecific growth interaction between Heterosigma akashiwo and Prorocentrum donghaiense

摘要

Enhanced solar ultraviolet-B (UV-B) irradiation resulted from the stratospheric ozone depletion has adverse impacts on the primary productivity of marine algae. The effects of UV-B enhancement on marine algae include reduction in photosynthesis and biomass, alteration in species competition, impaired chloroplast function, and damage to DNA. Harmful algal blooms (HAB) are an ubiquitous natural phenomenon caused by the excessive growth of phytoplankton. Many studies have examined the influence of supplemental UV-B irradiation on different algae, but the effects of UV-B irradiation on the interspecific growth interaction of HAB species has received little attention. In this study, Heterosigma akashiwo and Prorocentrum donghaiense were chosen to investigate the effect of UV-B irradiation on the growth interaction between two HAB species by a co-culture method. In a mixed culture experiment, H. akashiwo inhibited the growth of P. donghaiense in an inoculum dependent manner. In the absence of UV-B irradiation, H. akashiwo dominated the competition with P. donghaiense under different inoculation proportions. Surprisingly, supplemental UV-B irradiation alters the growth interaction between the two HAB species. P. donghaiense dominated the competition at the inoculation proportion of H : P = 1 : 4. Supplemental UV-B irradiation also weakens the competition dominance of H. akashiwo at the inoculation proportion of H : P = 1 : 1 or H : P = 4: 1.