Abstract：T he effects of various concentrations and exposure time of beneze ,toluene ,ethylbenzene ,and xylene (BTEX) on lipid peroxidation and malonaldehyde (MDA) content were studied in the coelomic fluid of sea cucumber A postichopus j aponicus with body weight of (5 .00 ± 0 .25) g exposed to the BTEX for 0 h ,24 h ,36 h ,48 h ,60 h ,72 h ,84 h and 96 h at water temperature of (17 ± 0 .5) ℃ and a salinity of 32 ± 0 .5 .Results showed that there were no significant changes in MDA content between low concentration benzene (0 .81 mg/L ) and toluene (0 .47 mg/L ) and the control group in the coelomic fluid of the sea cucumber during the experiment .In mid and high concentration of benzene (4 .06 mg/L and 20 .32 mg/L) and toluene (2 .33 mg/L and 11 .66 mg/L) ,and three concentrations of p-xylene (0 .28 mg/L ,1 .38 mg/L and 6 .92 mg/L) ,m-xylene (0 .22 mg/L ,1 .09 mg/L and 5 .44 mg/L) ,o-xylene (0 .16 mg/L ,0 .81 mg/L and 4 .05 mg/L) and ethylbenzen (0 .35 mg/L ,1 .74 mg/L and 8 .68 mg/L) ,however ,the MDA contents were found to be gradually decreased with increase in exposure time ,being inhibited significantly by both p-xylene and m-xylene contents .The findings indicate that BTEX might cause lipid peroxidation injury of the sea cucumber and that the MDA content might be used as biomarkers to evaluate the effects of BTEX on marine environment .
