Abstract
Allelopathy has been applied to control nuisance algae in aquatic systems, but the effects of allelochemicals on the broad spectrum of algae are not well understood. We investigate algicidal effects of the allelochemical juglone on the bloom-forming, harmful algae Microcystis aeruginosa and Stephanodiscus hantzschii, and on several non-target algal species including cyanobacteria (Anabaena flos–aquae, Oscillatoria curviceps, and Phormidium subfuscum), diatoms (Asterionella formosa, Fragilaria crotonensis, and Synedra acus), and green algae (Chlorella vulgaris, Scenedesmus ecornis, and Scenedesmus quadricauda), in laboratory and field enclosure bioassays. Under three treatment concentrations (0.01, 0.1, and 1 mg L−1) of juglone, Microcystis cell density is significantly reduced by 35–93%. Concentrations of 0.1 and 1 mg L−1 inhibits Stephanodiscus growth almost equally (66% and 75%, respectively). To contrast, juglone produces a stimulatory allelopathic effect on three green algae, and other tested diatoms showed hormesis. Overall, the cyanobacteria are more sensitive to juglone than the green algae and diatoms. These results indicate that the allelopathic effects of juglone on microalgae vary depending on their characteristic cellular morphology and anatomy.
Highlights
Harmful algal blooms (HABs) are a primary concern in water management, regarding recreational and drinking water resources [1,2,3,4,5]
The present study showed that juglone inhibited the growth of various algae, harmful, bloom-forming species such as S. hantzschii, a diatom that flourishes in cold seasons, and M. aeruginosa, a cyanobacterium abundant in warm seasons
This study demonstrated that juglone produced positive stimulatory effects as well as hormetic effects on the growth of some green algae and diatoms, suggesting its differential allelopathic effects on different algal assemblages
Summary
Harmful algal blooms (HABs) are a primary concern in water management, regarding recreational and drinking water resources [1,2,3,4,5]. Algal growth and development in natural fresh waters is subject to seasonal succession, depending on growth kinetics, competition, and planktonic herbivory [8] Cyanobacteria, such as Microcystis, Anabaena, and Aphanizomenon, often proliferate during warm summers, whereas some diatoms, such as Stephananodiscus, are dominant during cold seasons in temperate regions [9,10]. Various allelochemicals have been demonstrated to inhibit the growth of toxic cyanobacteria, including that of Microcystis aeruginosa [18,21,22], whereas their effects on other algal taxa, such as diatoms and green algae, are less well studied.
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