Screening And Application Of Bivalve Biomarkers In Organic Pollution Assessment In Benthic Environment Of Dongshan Bay

Dongshan Bay, located in the southeast of Fujian Province, is the largest bay inall of southern Fujian. With the continuous exploitation of Dongshan Bay, anincreasing number of pollutants have been discharged into this area, among whichtoxin orginic pollutants receives wide attention due to their characteristics ofpersistance, hydrophobicity, adsorptivity in sediments and high-toxicity to marinebenthos. Contents and distributions of the organic contaminants in the demersalenvironment of Dongshan Bay can be obtained using traditional chemical analysismethods. However, these monitoring datas only could not reflect the comprehensiveenvironmental effects of the organic contaminants very well. Therefore, it is necessaryto find a fast and accurate method to evaluate the integrated organic pollution pressurein the benthic environment of Dongshan Bay.Molecular biomarkers, which possess characteristic of high sensitivity, canreflect interactions between external pollutants and cellular targetsdirectly. They aresuitable for the early warning of environmental pollution. Responses of biomarkers topollutants can be transformed into environmental messages using integratedbiomarker response （IBR） index, which is widely used in the evaluation of marineenvironment quality.In this paper, marine bivalve Paphia undulatawasselected as the indicatororganism, and IBR was applied to estimate the organic pollution pressure in thebenthic environment of Dongshan Bay. Paphia undulata and sediment samples werecollected from10sampling sites in aquiculture area of Dongshan Bay. Contents ofpolychlorinated biphenyls （PCBs）, total petroleum hydrocarbon （TPHs） andnonylphenol （NP） in the soft tissue of Paphia undulataand sediments were measured.Meanwhile,10biomarkers of superoxide （SOD）, catalase （CAT）, glutathione-S-transferase （GST）, glutathione peroxidase （GPx）, reduced glutathione （GSH）,oxidized glutathione （GSSG）, glutathione reductase （GR）, acetylcholinesterase （AChE）,7-ethoxyresorufin-O-deethylase （EROD） and thiobarbituric acidreactivesubstances （TBARS） were assayed in gill and digetive gland of Paphia undulata. Abettery of biomarkers sensitive to the pollutants was screened using correlationanalysis and discriminatory analysis methods. Based on the results above, indicatorsystems for the Dongshan Bay benthic environmental organic pollution assessmentwere established.Main results for this study are as follows:（1） Contents of PCBs, TPHs and NP in sediments of Dongshan Bay were0.117⁰.810μg·kg^-1,3.70¹1.66mg·kg^-1and14.01²5.74μg·kg^-1, respectively.Compared to other marine areas, PCBs and TPHs contents in Dongshan Baysediments are at a relatively low level, while NP on the lower middle level. Contentsof PCBs, TPHs and NP in the soft tissue of Paphia undulata were0.286³.351μg·kg^-1,61.85¹01.31mg·kg^-1and41.45⁶2.02μg·kg^-1, respectively. Compared with othermarine bivalves, Paphia undulata in Dongshan Bay presented relatively lowconcentration for PCBs and NP, but a high adsorption for NP.（2） There were significant difference between biomarers in gills and digestivegland: levels of CAT, SOD, AChE, GSH, GSSG, GR and TBARS were higher in gillwhile GST activity was higher in digestive gland.There was little difference for GPxand EROD between the two organizations. Biomarker responses differed greatlyamong all sites because of the environmental pressure discrepancy.（3） Biomarkers inPaphia undulataresponsed differently to organic pollutants.PCBs stimulated the expression of oxidative stress biomarkers （SOD, CAT et al.） andthe biomarkers above in gills were more sensitive. TPHs had an inhibitory effect onoxidative stress biomarkers especially on those in digestive gland. PCBs and TPHsheightened the synthesisof EROD in Paphia undulata while TPHs inhibited theactivity of AChE. According to Pearson correlation analysis and discriminatoryanalysis, GR in gill and SOD, GSH, GST, GSSG, EROD in digestive gland wereselected as the indicator system to evaluate the organic pollution levels of benthicenvironment in Dongshan Bay. CAT, GPx, AChE, EROD in gill and GSH, EROD in digestive gland were selected as the indicator system to assess the organic pollutionpressure on Paphia undulata.（4） IBR index for each site was calculated according to the indicator systemsabove. Benthic environment organic pollution levels in Dongshan Bay ranked fromhigh to low as follows: DS3（2.30）>DS1（1.92）>DS2（1.85）>YX2（1.17）>YX1（0.87）>DS4（0.77）>YX3（0.75）>YX6（0.27）>YX5（0.14）>YX4（0.02）,DS2and DS3were the most seriously polluted area, with TPHs as the maininfluencing factor. The order of organic pollution pressure on Paphia undulata fromhigh to low was: YX（42.90）>YX（61.94）>DS2（1.11）>YX（50.97）>DS（10.96）>DS3（0.86）>YX3（0.57）>DS4（0.44）>YX1（0.34）>YX2（0.21）. PCBs and NP causedhigher pollution pressure on Paphia undulata.