Prolonged Microcystis restraint through allelochemicals sustained-release microspheres regulated by carbon material (CM-AC@SM): Optimal formulation, characterization, effects and synergistic inhibition mechanisms.

ABSTRACT

The Microcystis blooms have caused serious damage to aquatic ecosystems. Microspheres containing allelochemicals with sustained-release properties have the potential to function as a cost-effective and environmentally friendly algaecide against M. aeruginosa. In the current investigation, we successfully optimized the synthesis of allelochemicals sustained-release microspheres regulated by carbon material (CM-AC@SM), which demonstrated a high embedding rate (90.17 %) and loading rate (0.65 %), with an accumulative release rate of 53.27 % on day 30. To investigate the sustained-release mechanism of CM-AC@SM, the sustained-release process of allelochemicals was determined using the Folin-Phenol method and the immersion behavior of the CM-AC@SM was characterized through SEM and XPS. Results showed that allelochemicals were released in the delayed-dissolution mode. In addition, to elucidate the synergistic mechanism of CM-AC@SM towards the inhibition of M. aeruginosa, this study comprehensively assessed the effects of allelochemicals, carbon material and CM-AC@SM on the morphology, antioxidant system activity and photosynthetic activity of M. aeruginosa. The findings indicated that allelochemicals and carbon material induced intracellular protein and nucleic acid leakage by increasing cell membrane permeability, disrupted the extracellular and intracellular morphology of algae, triggered peroxidative damage and restrained antioxidant system activity by stimulating the generation of reactive oxygen species. Simultaneously, the activity of photosystem II was inhibited by allelochemicals and carbon material, substantiated by the reduction in Fv/Fo and Fv/Fm ratios. Hence, CM-AC@SM shows promise in inhibiting M. aeruginosa, offering an efficient approach for the future large-scale control of harmful algal blooms (HABs).