The Synergistic Effect of Sodium Hypochlorite (NaClO) and Organosilicone Adjuvant Enhances the Inhibition and Oxidative Damage in Cladophora sp.

<i>Cladophora</i>-dominated filamentous algal blooms constitute a growing threat to aquatic ecosystem stability and aquaculture operations. This study systematically evaluated the algicidal efficacy of sodium hypochlorite (NaClO), both individually and in combination with an organosilicone adjuvant, against <i>Cladophora</i> sp., with particular focus on induced oxidative damage mechanisms. Results demonstrated that NaClO exhibited a dose- and time-dependent inhibitory effect, achieving ≥90% inhibition at 1.20 mmol L^-1 within 48 h and >99% by 120 h, significantly surpassing the efficacy of lower concentrations (0.40 mmol L^-1) (<i>p</i> < 0.05). Physiological assessment revealed that 1.20 mmol L^-1 NaClO significantly suppressed total antioxidant capacity (T-AOC) after 96 h (<i>p</i> < 0.05). Notably, synergistic enhancement was observed with adjuvant co-application: at 0.40 mmol L^-1 NaClO, superoxide dismutase (SOD) activity reached its minimum with 0.33 ppm organosilicone adjuvant, showing significant reduction compared to higher adjuvant concentrations (<i>p</i> < 0.05). Furthermore, combinations of 0.80 and 1.20 mmol L^-1 with organosilicone adjuvant consistently maintained inhibition rates ≥ 94% across all sampling intervals, achieving control efficacy equivalent to 2.00 and 2.40 mmol L^-1 NaClO alone within 48 h. These findings demonstrate that NaClO supplemented with low-dose organosilicone adjuvant constitutes a promising and efficient strategy for mitigating <i>Cladophora</i> blooms.