Algicidal activity of the seaweed Corallina pilulifera against red tide microalgae

Extracts of seaweeds from the coast of Korea have been tested in vitro for algicidal activity against the growth of the toxic microalga Cochlodinium p olykrikoides. Blooms of C. polykrikoides and the ensuing mass mortalities o f farmed fish and shellfish are an escalating and worrisome trend. Cell gro wth of C. polykrikoides was inhibited by the addition to the culture medium of several seaweed extracts. Inhibition of growth resulted from methanol-s oluble extracts of the seaweeds Corallina pilulifera, Ulva pertusa, Ishige foliacea and Endarachne binghamiae. Growth inhibition also resulted from th e water-soluble extract of C. pilulifera. Powder and dry tissue from the se aweed C. pilulifera also inhibited cell growth of C. polykrikoides. The act ive algicidal products of C. pilulifera showed stable activity when boiled, exposed to light, or when treated under alkaline condition. Corallina pilu lifera had no regional and seasonal variations in this algicidal activity. A powder of the seaweed C. pilulifera, the most potent species, showed algi cidal activity against several red tide microalgae, especially C. polykriko ides, Gymnodinium mikimotoi, G. sanguineum, Heterosigma akashiwo, Prorocent rum triestinum and Pyraminonas sp.