Effects of Inoculation Proportions and UV-B Radiation on the Growth Competition between Two Red Tide Algae Alexandrium Tamarense and Skeletonema Costatum

The potential danger from the influence and injury of UV radiation on marine organisms has been increasing. In this study, for the first time we investigated the responses of the interspecies competition between two red tide algae, Alexandrium tamarense (At) and Skeletonema costatum (Sc) to different inoculation proportions and UV-B radiation enhancement by co- culture method. Our results demonstrated that the different inoculation proportions of A. tamarense and S. costatum had apparent effects on interspecies competition between the two red tide algae. When the inoculation proportion of A. tamarense and S. costatum was Af:Sc = 1:4, S. costatum was dominant in competition. In contrast, A. tamarense was dominant when Af:Sc = 1:1 and Af:Sc = 4:1. In addition, the UV-B radiation treatment could change the nature of the competition between A. tamarense and S. costatum, and promote the competitive dominance of S. costatum. We observed that the competitive dominance of S. costatum changed more remarkably when Af:Sc=l:4, and was in predominance when Af:Sc =1:1 under UV-B radiation treatment.