Inhibitory effects of marine alga enteromorpha intestinalis on the growth of the red tide microalga prorocentrum micans

The inhibitory effects of the marine green macroalga Enteromorpha intestinalis on the growth of the red tide microalga Prorocentrum micans were studied and the possible algicidal mechanisms was investigated by analysis of the activities of antioxidant enzymes, alteration of membrane permeability and ultrstructure of P. micans cells. Results indicated that the growth of P. micans was significantly inhibited by high concentrations of fresh tissues of Enteromorpha or their water phase extracts. The IC50 of the fresh tissue of E. intestinalis on P. micans for six days was 6.23 mg.mL⁻¹ and the water phase extracts was 18.17 µg·mL⁻¹. The activity of SOD, CAT and GSH-PX significantly elevated through 4 h to 24 h. The level of MDA was significantly elevated indicating lipid peroxidation and oxidation stress by Enteromorpha extracts treatment. The membrane permeability was altered by Enteromorpha extracts treatment as the intracellular concentration of Na⁺, K⁺, Mg²⁺ and Ca²⁺ decreased significantly after 36 h treatment. The cellular organelles including chloroplasts and Golgi complex were seriously damaged.