The interaction between Ulva pertusa (chlorophyta) and Heterosigma akashiwo (xanthophyta) and its responses to UV-B radiation

Effects of UV-B (280–320 nm) radiation on the interaction of Ulva pertusa Kjellman and Heterosigma akashiwo (Hada) Hada was studied in order to provide the fundamental to clarify the effects of UV-B radiation on marine ecosystems and the biological mechanisms of red tide occurrence. The result showed as follows: Heterosigma akashiwo could inhibit the growth of Ulva pertusa, and Ulva pertusa could inhibit the growth of Heterosigma akashiwo as well as. On the day 12, the growth inhibitory rate of Heterosigma akashiwo was 51.81%, but the growth inhibitory rate of Ulva pertusa was only 7.24%. Ulva pertusa gained an advantage over Heterosigma akashiwo in the growth interaction. UV-B radiation could inhibit the growth of Ulva pertusa and Heterosigma akashiwo when they were mono-cultured, and the growth inhibition was more significant with the increased doses of UV-B radiation treatment. The effects of UV-B radiation on the growth of Ulva pertusa were not significant when they were mixed-cultured. But UV-B radiation could inhibit the growth of Heterosigma akashiwo, and the growth inhibition was more significant with the increased doses of UV-B radiation treatment.