Toxicity Of Crude Oil And Four Kinds Of Dispersants To P.helgolandica And N.closterium

In recent years, with the development of marine transportation and exploitation,which has lead to more and more petroleum pollution accident.oil pollution hasbecame a type of endanger marine pollution, which has severely affected the globalmarine ecological environment. At present, as the the main component of thedispersants is surfactant, the dispersants has widely used in many petroleum pollutionaccident. As its main components are surfactant and solvent, so extensive use of thedispersants may produce toxic effect on the growth of marine organisms.Marine microalgae play an important role in the regulating of global climate,Chlorophyll is not only the basis of photosynthesis but also an important indicator todescribe the conversion capacity of marine microalgae. SOD is an importantcomponent of the antioxidant system of marine microalgae, the effect of pollutants onantioxidant system of microalgae can be measured by the activity of SOD. This paperselects crude oil, four kinds of dispersants （1^#,2^#,3^#,4^#） and four kinds of DWAF （1^#,2^#,3^#,4^#） as pollution factor and studies the response of P.helgolandica andNitzschia closterium f.minutissima on the cell density, chlorophyll, SOD, populationgrowth level.The results showed that the96h EC₅₀values of WAF against the growth ofP.helgolandica and N.closterium were9.4963and6.7856mg/L, respectively; The96hEC₅₀-chlvalues of DWAF against the Chlorophyll-a levels of P.helgolandica andN.closterium were4.4086and3.2223mg/L; The96h EC_50-chl-bwere4.6027mg/L.The96h EC₅₀values of four dispersants（1^#,2^#,3^#,4^#）against the growth ofP.helgolandica and N.closterium were0.0722,0.1852,0.1889,0.7198g/L and0.0511,0.2592,0.2939,0.5816g/L, respectively. In addition, the96h EC₅₀-chlvalues of fourdispersants （1^#,2^#,3^#,4^#）against the Chlorophyll-a and Chlorophyll-b levels ofP.helgolandica were0.0433,0.1325,0.1517,0.5121g/L and0.0503,0.1719,0.1212, 0.3091g/L; The96h EC₅₀-chlvalues of four dispersants（1^#,2^#,3^#,4^#） againstChlorophyll-a of N.closterium were0.0425,0.1365,0.1470and0.4215g/L. The96hEC₅₀values of four DWAF（1^#,2^#,3^#,4^#）against the growth of P.helgolandica andN.closterium were4.6170,76.8304,34.0626,26.2128g/L and1.0283,9.0848,3.9091,4.5301g/L, respectively. In addition, the96h EC₅₀-chlvalues of four DWAF（1^#,2^#,3^#,4^#）against the Chlorophyll-a and Chlorophyll-b levels of P. helgolandicawere3.9478,11.4044,29.0582,12.9695g/L and2.7998,37.3899,11.9007,13.835g/L;The96h EC₅₀-chlvalues of four DWAF（1^#,2^#,3^#,4^#）against Chlorophyll-a ofN.closterium were0.5084,6.9154,1.8430and2.4300g/L; The activity of SOD isincreased firstly and then decreased. In subacute toxicity test, exposure to4^#DWAFthe tolerance of N.closterium is poor in single culture system; P.helgolandica is morecompetitive in the bi-algal culture system.The results showed that:（1） According to EC₅₀values, exposure to WAF,dispersants and DWAF,the cell density and chlorophyll of N.closterium are moresensitive than P. helgolandica, for2^#and3^#dispersants, P.helgolandica are moresensitive than N.closterium;（2） According to EC₅₀values, the chlorophyll are moresensitive than the cell density of the two microalgae, which is more suitable forresponse the pollution situation timely;（3） According to EC₅₀values, The toxicityof the four kinds of dispersants are1^#>2^#>3^#>4^#;（4） The toxicity of the WAF reducesignificantly,as added dispersants in crude oil WAF;（5） P.helgolandica is morecompetitive in the co-culture system.