Allelopathic Effects of Two Organic Acids on Microcystis Aeruginosa

We selected two organic acids, heptanoic acid and benzoic acid, with the same carbon length but with different molecular structures to study their mechanisms of algal inhibition and to examine their combined algal inhibition ability. The results showed that the algal inhibition ability of benzoic acid was greater than that of heptanoic acid. The median lethal concentrations of benzoic acid and heptanoic acid were 55.02 mg/L and 83.90 mg/L, respectively. Heptanoic acid and benzoic acid could decrease the Total Superoxide Dismutase (T-SOD) and Catalase(CAT) activities of Microcystis aeruginosa and cause increased Malondialdehyde(MDA) production. The T-SOD and CAT activities initially increased and then decreased. The MDA content quickly decreased after reaching a maximum value. Benzoic acid had a greater effect on the antioxidant enzyme system of Microcystis aeruginosa than heptanoic acid. A hybrid evaluation was performed on the combined algal inhibition effect of heptanoic acid and benzoic acid. The results indicated that benzoic acid and heptanoic acid showed a synergistic effect and that their compound algal inhibition effect was superior to the separate effects of the two organic acids acting independently.