Algicidal effects of Korean oak trees against the cyanobacterium Microcystis aeruginosa

Abstract

In an effort to identify a new environment-friendly algicide, we examined the ability of extracts from the leaves and stems of nine Korean oak tree species to inhibit growth of the bloom-forming cyanobacterium, Microcystis aeruginosa. At a concentration of 100 mg L-1, five of the oak tree extracts (QAT-L, QAT-S, QAS-L, QGI-S, and QSA-L) decreased the cell density of M. aeruginosa by over 90% for 7 days. At a concentration of 20 mg L-1 , the same five extracts inhibited the growth of M. aeruginosa by approximately 50%. The minimum concentration of oak tree extracts required for effective inhibition of M. aeruginosa (20 mg L-1 ) is comparable to that of the known algicide, tannic acid (17 mg L-1 ), which is thought to be one of the main active ingredients in the oak tree extract. These findings suggest that oak extracts may be useful as an environment-friendly algicide to control the bloomforming cyanobacterium, M. aeruginosa, in eutrophic waters.