Abstract: Allelopathic effects of green tide alga Ulva prolifera on the proliferation of red tide algae Skeletonema costatum were studied. The fresh tissue, dry powder and culture medium filtrate of U. prolifera were used for inhibiting the proliferation of S. costatum. Results showed that the fresh tissue of U. prolifera could inhibit significantly the proliferation of S. costatun. In all groups with the fresh tissue, the inhibition rate was as high as 100% after co-culturing for 12 days. As for the groups with the dry powder, the inhibition rate in the 1.2 g·L^-1 group reached 50% after co-culturing for 12 days. It indicated that the inhibition of green tide algae on S. costatun proliferation presented a concentration-response relationship, and that there was not only nutrient competition inhibitory but also allelochemicals inhibition. Further studies showed that there was no significant inhibition of culture medium filtrate on the proliferation of S. costatum in the experiment with one-time adding culture medium filtrate of U. prolifera, while the proliferation of S. costatum was significantly inhibited in the experiment with semi-continuously adding culture medium filtrate of U. prolifera. The inhibition rate for semi-continuously adding culture medium filtrate of U. prolifera was 75% after culturing for 12 days. It indicated that allelochemicals in U. prolifera was gradually released to the environment. This research laid a solid foundation for further research on concentration-response relationship between U. prolifera and S. costatum.

Key words: 浒苔, 中肋骨条藻, 化感抑制作用