Growth Inhibition of Blue-green Algae by Allelopathic Effects of Macrophytes

Abstract

Inhibitory effects of macrophytes on the growth of blue-green algae (Microcystis aeruginosa, Anabaena flos-aquae, Phormidium tenue) were assayed in a mixed culture system with various concentrations of macrophytes, (i.e., coexistence assay) . Egeria densa, Cabomba caroliniana, Myriophyllum spicatum, Ceratophyllum demersum, Eleocharis acicularis, Potamogeton oxyphyllus, Potamogeton crispus, Limnophila sessiliflora and Vallisneria denseserrulata were used as macrophytes. The coexistence assay showed the inhibitory effects of the macrophytes on algal growth and that, among the 9 macrophytes, C. caroliniana and M. spicatum were the only species to inhibit growth of all the species of blue green algae. The inhibitory effects of M. spicatum were stronger than those of C. caroliniana.
Due to its strong inhibition, we used the cultured solution of M. spicatum for an algal assay to confirm that the inhibitory effect of M. spicatum is caused by allelopathic compounds secreted by M. spicatum. The growth of M. aeruginosa was significantly inhibited by the quasi-continuous addition of the cultured solution of M. spicatum, whereas the initial addition did not inhibit their growth. Such results provide the evidence of the allelopathic compounds, which must be continuously secreted by M. spicatum.