Environmental Assessment Of Beibu Bay Intertidal Zone Based On Multiple Biomarkers

Beibu Bay is a big semi-closed bay located at the northwest of the South ChinaSea. At present, environmental quality assessment of Beibu Bay is limited on thedetermination of contaminants in the sediment or the biology. Due to the variety ofcontaminants, there are antagonist or coordination effects among them. According tothe existing environmental quality assessment methods, it is difficult to assess thecomprehensive environmental effects. Molecular biomarkers, which are characteristicof high specificity and sensitivity, can reflect the interaction between externalpollutants and cellular targets directly. They are suitable for the early warning ofenvironmental pollution. Integrated biomarker response (IBR) index can reflect theintegral contamination conditions, and visualization is possible between sites forcomparison with pollution gradient.Marine bivalve Paphia undulata and sediment samples are collected from9sampling sites distributed in the intertidal zone along the Beibu Bay in the spring of2011. Contents of several contaminants are determined, such as seven types of heavymetal (Hg, Cd, Pb, Cr, Cu, Zn, As), sulfide (measured in the sediment only), totalpetroleum hydrocarbon (TPH), polychlorinated biphenyls (PCBs), Nonylphenol (NP)and Benzo(a)pyrene (B[a]P) in the soft tissue of bivalve and sediment. Meanwhile,9biomarkers are assayed in the gills and viscus of Paphia undulata. They areglutathione (GSH)、 oxidized glutathione(GSSG), superoxide dismutase(SOD),catalase (CAT), glutathione peroxidase(GPx), glutathione-S-transferases(GST),thibabituric acid reactive substance(TBARS), acetylcholinesterase(AChE) andmetallothionein(MTs). The above determination results are integrated in order toscreen a set of biomarkers sensitive to the pollutants’ toxic effects by correlationanalysis and discriminatory analysis. Based on the multiple biomarkers screenedabove, an indicator system and an integrated environmental quality assessment modelfor the Beibu Bay benthic environmental quality assessment are established. The results show that, distribution characteristics of the contaminants determinedin the sediment and biology collected in the intertidal zone of Beibu Bay differ greatly.This distribution status depends on several factors, such as the sedimentcharacteristics of the sampling areas and pollution emission sources. The responses of9biomarkers in the gills and viscera of Paphia undulata to the contaminants arediverse, with significant difference between tissues and regions. According to thePearson correlation analysis, except for AChE the in gills, the rest biomarkers all havesignificant correlations with at least one contaminant in the sediment or P. aphiaundulata. Biomarkers correlated to2or3contaminants are selected in priority; theyare GSSG, GSH and GST in the gills, TBARS, GPx in the viscera. In addition to this,Discriminatory analysis is used to screen one kind of biomarker within the rest12biomarkers correlated with one pollutant. GPx in the gills is selected for its strongestdistinguish ability between stations, the above6biomarkers are more sensitive to thetoxic effects of the pollutants, and constitute the indicator system for Beibu Bayintertidal zone environmental assessment together.IBR index for each station is calculated to assess the pollution gradient. The IBRindex of9sampling stations ranges from0.12to2.89. S3(Lemin shipside inZhanjiang, Guangdong) and S7(eastern of Fangchenggang, Guangxi) station are theleast and most contaminated respectively. The pollution gradient sequence is:S7(eastern of Fangchenggang, Guangxi), S1(Beigang shipside, Guangdong),S6(Laorensha shoal of Qinzhou Bay, Guangxi), S8(western of Fangchenggang city,Guangxi)、S5(Xichang in Beihai, Guangxi)、S2(Jianghong shipside, Guangdong)、S4(Beitan shipside, Guangdong)、S9(Yueliang Bay in Fachenggang, Guangxi)、S3(Lemin shipside, Guangdong). The assessment results are in accordance withchemical determination results. The IBR index could be used to assess the benthicenvironment quality of Beibu Bay.