Abstract
Increased eutrophication in the recent years has resulted in considerable research focus on identification of methods for preventing cyanobacterial blooms that are rapid and efficient. The objectives of this study were to investigate the effects of dihydroartemisinin and artemether on the growth of Microcystis aeruginosa and to elucidate its mode of action. Variations in cell density, chlorophyll a, soluble protein, malondialdehyde, extracellular alkaline phosphatase activity (APA), and chlorophyll fluorescence parameters (Fv/Fm, ΦPSII, ETR, rapid light curves, fast chlorophyll fluorescence curves on fluorescence intensity, and relative variable fluorescence) were evaluated by lab-cultured experiments. Our results demonstrated that both dihydroartemisinin and artemether inhibited the growth of M.aeruginosa by impairing the photosynthetic center in photosystem II and reducing extracellular APA, with a higher sensitivity exhibited toward artemether. The inhibitory effects of dihydroartemisinin on M.aeruginosa increased with concentration, and the maximum growth inhibitory rate was 42.17% at 24 mg·L-1 after 120h exposure, whereas it was 55.72% at 6 mg·L-1 artemetherafter 120h exposure. Moreover, the chlorophyll fluorescence was significantly inhibited (p<0.05) after 120h exposure to 12 and 24 mg·L-1 dihydroartemisinin. Furthermore, after 120h exposure to 6 mg·L-1 artemether, Fv/Fm, ΦPSII, ETR and rETRmax showed a significant decrease (p<0.01) from initial values of 0.490, 0.516, 17.333, and 104.800, respectively, to 0. One-way analysis of variance showed that 6 mg·L-1 artemether and 24 mg·L-1 dihydroartemisinin had significant inhibitory effects on extracellular APA (p<0.01). The results of this study would be useful to further studies to validate the feasibility of dihydroartemisinin and artemether treatment to inhibit overall cyanobacterial growth in water bodies, before this can be put into practice.
Highlights
Worldwide, harmful algal blooms (HABs) of freshwater aquatic ecosystems, especially Microcystis aeruginosa (M. aeruginosa) blooms, have resulted in the reduction of biodiversity, ecosystem functions, and deterioration of surface water quality [1]
After 24 h growth of M. aeruginosa became inhibited after exposure to dihydroartemisinin and artemether
Results from the present investigation showed the trends in Chlorophyll a (Chl-a) content under various doses of dihydroartemisinin and artemether followed asimilar pattern to cell density
Summary
Harmful algal blooms (HABs) of freshwater aquatic ecosystems, especially Microcystis aeruginosa (M. aeruginosa) blooms, have resulted in the reduction of biodiversity, ecosystem functions, and deterioration of surface water quality [1]. Several approaches have been proposed and studied for the removal of HABs. Currently, several approaches have been proposed and studied for the removal of HABs These methods include mechanical, physical (ultrasonication, coagulation/flocculation and centrifugal separation), biological (Traditional biomanipulation and Non-Traditional biomanipulation), and chemical (oxidants and metal-ion compounds) methods [4,5]. These approaches can efficiently remove cyanobacteria from polluted surface water, most of them have operational, economic, and environmental limitations [6]. Taking these limitations into account, it is necessary to develop a new generation of algal inhibitors to only target HAB communities. These new inhibitors will still have to be effective, applicable, economical, and environmentally benign
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