Relationship with H₂O₂ and chlorophyll a (A), H₂O₂ and POD (B), H₂O₂ and APX (C), and H₂O₂ and CAT (D) of E. densa under control (C), reduced (R), highly reduced (HR), transferred water from reduced tank (RW), and transferred water from highly reduced tank (HRW) conditions, and 0, 0.01, 0.05, 0.1, 0.2 mM H₂S concentrations. Values are the means of three replicates ± SD, n = 3.