Abstract: By the method of co-culture and using cell density as the main indicator, this paper studied the allelopathic effect of Corallina pilulifera on
Heterosigma akashiwo and its responses to UV-B irradiation. Under normal condition, the fresh tissue and aqueous extracts of C. pilulifera had significant inhibitory effects on the growth of H. akashiwo (P<0.05), indicating their allopathic effect on H. akashiwo, while the dry power and culture media filtrate of C. pilulifera had less effect (P>0.05). After pre-treated with different dose UV-B radiation and then co-cultured with H. akashiwo, C. pilulifera had some changes in the allelopathic activity of its fresh tissue, dry powder, and aqueous extracts. High-dose UV-B radiation (3.0 J·m^-2) induced the decrease of the allelopathic effect, whereas low-dose UV-B radiation (0.9 J·m^-2) was in adverse (P<0.05).

Key words: allelopathic effect, UV-B radiation, Corallina pilulifera, Heterosigma akashiwo, inhibition effect, snow evaporation in forest, measurement and estimation methods, influential factor.