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

Cladophora-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 Cladophora 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) (p < 0.05). Physiological assessment revealed that 1.20 mmol L−1 NaClO significantly suppressed total antioxidant capacity (T-AOC) after 96 h (p < 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 (p < 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 Cladophora blooms.