The Effectiveness of Ulva fasciata and U. pertusa (Ulvales, Chlorophyta) as Algicidal Substances on Harmful Algal Bloom Species

The algicidal activity of fresh tissue, dry powder and methanol extracts of Ulva fasciata and U. pertusa were evaluated against harmful algal blooms (HAB) species. The results indicate that sporophyle of fresh tissue from U. fasciata and U. pertusa induced the growth inhibition and lethal effects on Heterosigma akashiwo and Alexandrium catenella higher than their gametophyte strains. The dry powder of sporophyte of U. fasciata and U. pertusa induced significantly high rate of reduced growth and cell death than gametophyte strains on H. akashiwo species. On the contrary, the dry powder of Ulva spp. had low effect on A. catenella species. Furthermore, the methanol extracts of sporophyte of U. fasciata and U. pertusa showed higher algicidal effects than their gametophyte strains on HABs. It was also demonstrated that microalgae respond differentially to the methanol extracts of Vlva spp. These assays were most effective against the cells of Chattonella marina, H. akashiwo, and were moderately effective against Fibrocapsa japonica and Karenia mikimotoi cells. Meanwhile, the methanol extracts were lowest effective against A. catenella cells. The difference of the response among these microalgae species tested suggests that algicidal effects of Ulva spp. could be utilized for selective control on HAB species.