Effects of extracts of reed and cattail on the growth of a cyanobacterium, Microcystis aeruginosa

The effect of reed (Phragmites australis) and cattail (Typha angustifolia) extracts at different decomposition stages (fresh and dead) on the growth of a cyanobacterium, Microcystis aeruginosa, was investigated. Effective concentration 50 (EC50) of extracts were quantified based on dissolved organic carbon (C) concentration. The 100-day extract of fresh cattail showed the most inhibitory EC50 value of 19.3 mg C/L. We found that the fresh plant was more inhibitory than the dead plant for both species based on EC50 and the comparison of growth percentage in the maximum concentration of extracts, implying different compounds were produced during the time course of decomposition. The results of this study suggest that lake restoration efforts that include using emergent macrophytes to control nuisance algae should consider macrophyte life stage and decomposition time together with selecting macrophyte species, although further chemical identification is required to understand the allelochemical production in a variety of decomposition stages.