Water Science & Technology Vol 66 No 5 pp 993–999 © IWA Publishing 2012 doi:10.2166/wst.2012.272
Polyphenols and fatty acids responsible for anti-cyanobacterial allelopathic effects of submerged macrophyte Myriophyllum spicatum
S. Nakai, G. Zou, T. Okuda, W. Nishijima, M. Hosomi and M. Okada
Graduate School of Engineering, Hiroshima University, Higashi-hiroshima 739-8527, Japan E-mail: sn4247621@hiroshima-u.ac.jp
Shanghai Academy of Agricultural Science, 2901 Beidi Rd, Shanghai 201106, China
Environmental Research Management Center, Hiroshima University, Higashi-hiroshima 739-8513, Japan
Institute of Symbiotic Science and Technology, Tokyo University of Agriculture and Technology, 2-24-16 Naka, Koganei, Tokyo 184-8588, Japan
Faculty of Liberal Arts, The Open University of Japan, 2-11 Wakaba, Mihama-ku, Chiba 261-8586, Japan
ABSTRACT
Myriophyllum spicatum is known to inhibit the growth of cyanobacteria such as Microcystis aeruginosa by releasing anti-cyanobacterial allelochemicals. The allelochemicals possibly responsible for the inhibition include five polyphenols and three fatty acids, but the extent to which these are indeed responsible for the anti-cyanobacterial effects is unclear. The goal of this research was to determine the contribution of these compounds to the allelopathic effect of M. spicatum on M. aeruginosa. We first collected information on the release rates of these compounds and then added the compounds to a cyanobacterial medium on the basis of their release rates so as to simulate their excretion by M. spicatum. Addition of the polyphenols and fatty acids inhibited the growth of M. aeruginosa, and the interaction of the polyphenols and fatty acids was additive. The EC50 of a polyphenol and fatty acid mixture was compared with that of M. spicatum itself as previously determined in a mixed culture system in which M. spicatum and M. aeruginosa were incubated. The former was about 1.9 times higher than that of the latter, the implication being that the inhibitory effect of the polyphenols and fatty acids contributed about 53% of the allelopathic effect of M. spicatum. This paper is the first to describe allelochemicals that account for a half of the anti-cyanobacterial allelopathic effect of a macrophyte.
Keywords: allelopathy; cyanobacterial growth inhibition; fatty acid; Myriophyllum spicatum; polyphenol
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