Broad spectrum and species specificity of plant allelochemicals 1,2-benzenediol and 3-indoleacrylic acid against marine and freshwater harmful algae

Allelochemicals derived from plants have shown great potential in mitigating harmful algal blooms (HABs), although different algal species can respond differently to these chemicals. Therefore, we first investigated the allelopathic effects of two newly identified plant-derived allelochemicals, 1,2-benzenediol (1,2-BD) and 3-indoleacrylic acid (3-IDC), on six algal species. Then we further evaluated the allelopathic responses of two bloom-forming species, Microcystis aeruginosa FACHB-905 and Heterosigma akashiwo to 1,2-BD. Results showed that 1,2-BD had a broader antialgal spectrum than 3-IDC. Allelopathic response analysis indicated that 1,2-BD consistently and stably inhibit the growth of M. aeruginosa FACHB-905, with inhibitory mechanism being disruption of photosynthetic activity, overwhelming of the antioxidant system and activation of programmed cell death (PCD). H. akashiwo displayed resistance to 1,2-BD during exposure, and the growth inhibition was mainly attributed to PCD. Therefore, the species-specific allelopathic responses provide new insights for controlling HABs using 1,2-BD and 3-IDC.