Effects of the macroalga Corallina pilulifera on the growth of red tide microalga Prorocentrum micans under laboratory conditions

Allelopathic effects of several concentrations of fresh tissue and dry powder of three macroalgae, Grateloupia turuturu, Corallina pilulifera and Gelidium amansii, on the red tide microalga Prorocentrum micans were evaluated in microcosms. Preliminary studies on the algicidal effects of one aqueous and four organic solvent extracts from C. pilulifera on the P. micans were carried out to confirm the existence of allelochemicals in the tissues of the macroalga. The results of the microcosm assay showed that the growth of P. micans was strongly inhibited by using fresh tissues and dry powder of the three macroalgae, the inhibitory effect of C. pilulifera is the best. Both aqueous and methanol extracts of C. pilulifera had strong growth inhibitory effects on P. micans, while the other three organic solvent extracts (acetone, ether and chloroform) had no apparent effect on its growth, this suggested that the allelochemicals from C. pilulifera had relatively high polarities. The dry powder of C. pilulifera was extracted with methanol, and the methanol extracts were partitioned to petroleum ether phase, ethyl acetate phase, butanol phase and distilled phase by liquid-liquid fractionation. The bioassays of the activity of every fraction were carried out on P. micans, indicated that petroleum ether phase and ethyl acetate phase had strong algicidal effect on P. micans.