Growth inhibition of blue–green algae by allelopathic effects of macrophytes

Abstract

Inhibitory effects of macrophytes on the growth of blue-green algae (i.e. Microcystis oeruginosa, Anoboena flos-aquae, or Phormidium tenue) were evaluated in a coexistence culture system in which concentrations of different macrophyte species were varied ( i.e. Egeria densa, Cabomba caroliniana. Myriophyllutn spicatum, Ceratophyllum demersum, Eleocharis acicularis, Potamogeton oxyphyllus, Potamogeton crispus, Limnophila sessilifloro, or Vallisneria denseserrulata). Coexistence assay results showed that only the macrophytes C. caroliniana or M. spicutum inhibited the growth of all blue-green algae, with the inhibitory effects of M. spicutum being stronger than those of C. caroliniana and being produced by the release of allelopathic compounds. In subsequent initial addition assays using M. spicatum with the alga M. aeruginosa, no significant growth inhibition was observed; whereas, in contrast, quasi-continuous addition assays showed strong growth inhibition by M. spicatum. These results provide the first evidence that unstable, growth-inhibiting allelopathic compounds are continuously secreted by M. spicatum