We developed a biologically-derived substance naphthoquinone (NQ) derivate for the eco-safe mitigation of harmful cyanobacteria blooms such as Microcystis and Dolichospermum. NQ was reacted with various substituents (Rn) to produce different NQ derivatives. We tested a total of 92 algicidal compounds based on the algicidal activity of Microcystis and Dolichospermum. 22 compounds of NQ were selected as candidates (algicidal activity >80% at 1 µM). Among them, NQ 40 compound showed the highest algicidal activity of 99.6% and 100% at the optimal concentration of 1 µM on Microcystis and Dolichospermum, respectively. No algicidal effects of NQ 40 (1 µM) were observed against non-target algae such as Stephanodiscus, Cyclotella and Peridinium. According to the results of acute eco-toxicity assessment, the EC50 values of NQ 40 compound for Selenastrum capricornutum and Daphnia magna were 3.2 and 14.5 µM, respectively, and the LC50 for Danio rerio was 15.7 µM. In addition, for D. magna chronic eco-toxicity assessment, no toxicity toward survival, growth and reproduction was observed. Therefore, we suggested the NQ 40 (1 µM) compound as an alternative eco-safe algicidal substance to effectively mitigate harmful cyanobacteria blooms.

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