Fig. 2. Effects of control, his, ace, uro with EC₅₀ value, (1 TU, 23, 16, 8 μg mL⁻¹, respectively) uro + ace (1 : 1 TU, 8 : 16 μg mL⁻¹) and uro + his (1 : 1 TU, 8 : 23 μg mL⁻¹) on (a) ROS level after 72 h and (b) protein contents of Phaeocystis globosa. One toxic unit (TU) means the toxic concentration is nearly EC₅₀. All error bars indicate standard error of three replicates. *Indicates significant difference (P < 0.05) with respect to control. Letters above the bars indicate significant differences (P < 0.05).