Responses of the macroalga Gracilaria lemaneiformis to the stress of cypermethrin,a pyrethroid insecticide

The growth behavior and physiological responses to pyrethroid stresses were investigated through the exposure of Gracilaria lemaneiformis to different concentrations of cypermethrin.The growth of G.lemaneiformis was less sensitive to cypermethrin compared to microalgae and aquatic animals,and low cypermethrin(100 μg·L-1)did not inhibit the growth.However,quick and significant physiological responses occurred when G.lemaneiformis was experienced to cypermethrin,and all biochemical parameters varied significantly within 24 h exposure.Chlorophyll a(Chl.a),phycoerythrin,(PE),soluble protein,soluble sugar,malondialdehyde(MDA),and superoxide dismutase(SOD)activity was significant enhanced at low concentrations(5 or 10 μg·L-1)while was inhibited at high concentrations of cypermethrin(10 or 50 μg·L-1).A general dose-dependence increase in MDA level was observed under the cypermethrin concentrations of this experiment(1~100 μg·L-1),which reveals that the toxic effect of cypermethrin was probably exerted through lipid peroxidation by free radical generation.Our results suggest that the activation of SOD and promotion of protein and sugar content at early exposure under low concentrations are important to counteract the oxidative stress induced by cypermethrin,and the inactivation of SOD at high concentrations may be crucial to the growth inhibition of G.lemaneiformis by cypermethrin.