Efficient inhibition of Microcystis aeruginosa using expanded perlite sustained-release pyrogallic acid: performance studies, mechanistic insights and ecological security assessment

Abstract

Allelochemicals are effective and safe for controlling cyanobacterial blooms, but their direct application suffers from rapid degradation and poor persistence. To address this limitation, we engineered a buoyant, surface-targeting delivery system to inhibit non-toxic and toxic Microcystis aeruginosa by preparing PA/Expanded perlite composites using expanded perlite as a matrix. The results showed that PA was successfully loaded onto expanded perlite, and PA/Expanded perlite could achieve long-term release of phenolic release (PA-dominant). PA/Expanded perlite was effective in removing both non-toxic and toxic M. aeruginosa, with the maximum inhibition rate of 97.60 %, and the EC₅₀ (7d) values were 15.60 and 6.90 mg/L, respectively. The PA/Expanded perlite composite achieved a 97.62 % inhibition rate against M. aeruginosa in natural landscape water. Additionally, treatment with PA/Expanded perlite significantly reduced chlorophyll a and phycobiliprotein content in both algal strains, and the photosynthetic rates of toxic and non-toxic M. aeruginosa decreased to 0.03 and 0.0043 [μmol/(mg·h)], respectively. Meanwhile, the activities of superoxide dismutase (SOD) and catalase (CAT) and the content of malondialdehyde (MDA) were significantly increased. Under current exposure levels, PA/Expanded perlite did not pose harm to Daphnia magna and Pteris vittata, while significantly reducing intracellular microcystin-LR (MC-LR) contents, which has promising application for the control of water blooms.