Using Biomarkers To Study Toxic Effects Of Shengli Crude Oil On Cynoglossus Semilaevis

In order to investigate the feasibility of antioxidate system enzymes and several kinds of immune enzymes as the biomarkers of petroleum pollution, the juvenile Cynoglossus semilaevis was exposed to Shengli crude oil at different levels (0.1, 0.2, 0.4, 0.8, 1.6 and 3.2mg/L). Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), Glutathione S-transferase (GST), Peroxidase (POD), lysozyme (LSZ) in liver and Na~+-K~+-ATPase in gill of juvenile Cynoglossus semilaevis were measured in exposure time of 1, 2, 4, 8 , 15 days and removed pollution time of 1, 3 days. The mainly results is following.1. In the 15-day oil exposure period, the activity of SOD and CAT had the trend of increase-decrease-increase with time. The GPx activity increased to the maximum on the 4th day and then decreased. The GST activity had the similar trendency with GPx, and there was no significant change in the GST activity of lower concentration groups (0.1 and 0.2mg/L). The time when antioxidate enzymes activity reached the high values was shorter with exposed concentration increasing. In addition, the time when GPx and CAT activity was significantly induced was earlyer than GST and SOD, so GPx and CAT are more sensitive to oil pollution stress than GST and SOD. Antioxidant enzymes are not suitable alone as a biomarker of oil pollution, because changes in the activity of them are affected by many factors. Several antioxidant enzymes should be combined and integrated with other indicators for analysis.2. In the 15-day oil exposure period, the POD and LSZ activity of lower concentration groups had the trend of increase-decrease with time, and the higher concentration groups had the opposite trend. The gill Na~+-K~+-ATPase decreased at first and then increased gradually. The liver LSZ and gill Na~+-K~+-ATPase activity had significantly differences with the control group, and the liver POD activity of group 3.2mg/L was significantly inhibited on the fourth day. So the liver POD, LSZ, gill Na~+-K~+-ATPase can be used as biochemical indexes that reflecte the adversity physiological condition of the juvenile Cynoglossus semilaevis in the oil pollution stress. Liver LSZ and gill Na~+-K~+-ATPase are more sensitive than liver POD, and more suitable as biomarkers of petroleum pollution.3. Toxic effects of pollutants on organisms have a certain threshold. Under this threshold toxic reaction has not occurred to the body, and the Physiological conditions can return to the normal level quickly. If beyond this threshold, toxic reactions occur to the organisms. Even after the lifting of pollution stress, the activity of organisms can not be restored to normal levels. From the recovery of the enzymes activity in juvenile Cynoglossus semilaevis after the lifting of the petroleum pollution stress, the following conclutions can be drawed. The threshold of Shengli crude oil on liver CAT, GPx and LSZ is between 0.2 and 0.4mg/L. The threhold of GST is between 0.8 and1.6mg/L, that of SOD is between 1.6 and 3.2 mg/L, the threholds of POD and Na~+-K~+-ATPase are 3.2 mg/L or more.4. This paper established the comprehensive evaluation index of multiple biomarkers based on the integrated biomarker responses (IBR). Between IBR value of each experimental group and the exposure time is a positive correlation in the previous period of oil exposure, and is a negative correlation in the later stage. There is no obvious rule between IBR value and oil exposure concentration.