Endpoint-dependent treatment progression and parent-cyanotoxin attenuation in freshwater bloom-forming taxa during silver-containing visible-light-assisted T-P25/Ag3PO4 treatment.

Biomass- and chlorophyll-based endpoints are widely used to evaluate algal control, but their ability to represent treatment progression across distinct bloom-forming taxa remains uncertain. In this study, four representative freshwater taxa, Microcystis aeruginosa, Cylindrospermopsis raciborskii, Chlorella vulgaris, and Cyclotella meneghiniana, were comparatively examined under a defined silver-containing, visible-light-assisted T-P25/Ag3PO4 treatment condition. Multi-endpoint tracking revealed asynchronous response trajectories among the four taxa. C. meneghiniana showed the fastest early chlorophyll a decline, with 12.65% remaining after 1 h, whereas C. vulgaris exhibited a comparable time-integrated response despite slower early pigment loss. To summarize these asynchronous responses, a module-based generalized disturbance index (GDI) and species susceptibility index (SSI) were used as protocol-specific descriptive tools. The SSI order was C. meneghiniana (0.548) > C. vulgaris (0.543) > C. raciborskii (0.515) > M. aeruginosa (0.481), indicating that early pigment loss and cumulative multidimensional physiological disturbance are related but not equivalent. For M. aeruginosa, an observation-defined interval of approximately 5 h separated near-complete Chl-a loss at 5 h from a > 90% decrease in extracellular parent MC-LR from its observed maximum at 10 h; extracellular parent CYN remained detectable at 10 h. These findings show that chlorophyll decline should not be used to infer treatment completion. Multi-endpoint evaluation provides a process-aware basis for comparing taxon-specific treatment responses and defining parent-cyanotoxin monitoring needs.