Pollution of marine environment has become an issue of major concern in recent years. Serious environmental pollution by heavy metals results from their increasing utilization in industrial processes and because most heavy metals are transported into the marine environment and accumulated without decomposition. The aim of the present study is to investigate the effects on growth, pigments, lipid peroxidation, and some antioxidant enzyme activities of marine microalga Pavlova viridis, in response to elevated concentrations of cobalt （Co） and manganese （Mn）, especially with regard to the involvement of antioxidative defences against heavy metal-induced oxidative stress. In response to Co^2＋, lipid peroxidation was enhanced compared to the control, as an indication of the oxidative damage caused by metal concentration assayed in the microalgal cells but not Mn^2＋. Exposure of Pavlova viridis to the two metals caused changes in enzyme activities in a different manner, depending on the metal assayed： after Co^2＋ treatments, total superoxide dismutase （SOD） activity was irregular, although it was not significantly affected by Mn^2＋ exposure. Co^2＋ and Mn^2＋ stimulated the activities of catalase （CAT） and glutathione （GSH）, whereas, glutathione peroxidase （GPX） showed a remarkable increase in activity in response to Co^2＋ treatments and decreased gradually with Mn^2＋ concentration, up to 50 μmol/L, and then rose very rapidly, reaching to about 38.98% at 200 μmol/L Mn^2＋. These results suggest that an activation of some antioxidant enzymes was enhanced, to counteract the oxidative stress induced by the two metals at higher concentration.
LI MeiZHU QinHU Chang-weiCHEN LiLIU Zhi-liKONG Zhi-ming
Strontium-induced stress in growth and chlorophyll contents of Platymonas subcordiformis was investigated under laboratory condition. The results showed that strontium exposure had little influ- ences in general on growth and chlorophyll contents of the algae except for very high Sr concentrations. The maximum biosorption capacity of strontium ranged from 69.62 to 269.18 mg Sr2+/g dry weight. The algal biomass exhibited high uptake capacity of strontium. Total superoxide dismutase (SOD) activity and the content of lipid peroxidation products malondialdehyde (MDA) were significantly different in differ- ent treatments. SOD activity reached the highest level at 0.09 mmol/L that was about 55.8 % higher than that in the control. The MDA content increased significantly at 0.36 mmol/L, which was 2.15 times higher than that in the control, indicating a state of oxidative stress. With the increase of strontium concentration, the amount of fatty acids decreased.
