The Toxic Effects Of Hexabromocyclododecane(HBCD)and Tetrabromobisphenol A(TBBPA) On Four Species Of Marine Microalgae

Hexabromocyclododecane （HBCD） and Tetrabromobisphenol A （TBBPA） areused as bromine flame retardants primarily in polystyrene foams, electricalequipments and acrylonitrile butadiene styrene copolymers （ABS）. The migration,accumulation and persistence characeristics of HBCD and TBBPA determine thecompounds will not only remain in the environment, but also for bioaccumulation andamplification to affect the normal physiological activities of organisms. Therefore, thestudy on behavior of HBCD and TBBPA in the environment is very necessary.Reports show that HBCD and TBBPA have neurotoxicity, liver toxicity andendocrine disturbance on the organisms. However, their toxic effects on marinemicroalgae are rarely reported, so it could not give an objective evaluation of themarine ecological risk of such compounds.Microalgae, as primary producers in the aquatic ecosystems, its structure andquantity changes can reflect impacts of pollutants on the primary producers in sea andmarine ecosystems.Regarding Dicrateria inornata, Skeletonema costatum, Phaeodactylumtricornutum and Chlorella vulgaris as testing organism, the acute toxic effects ofHBCD and TBBPA on four marine microalgae are assessed. The96h median effectconcentrations (96h-EC₅₀) of HBCD and TBBPA on marine microalgae arecalculated for comparing toxicity of compounds on algae. On the basis of this, D.inornata and S. costatum are chosen as research materials for the followingexperiments. The variations of photosynthetic pigments （chloraphyll-a （Chl-a）,chlorophyll-c （Chl-c） and Carotenoid （Car））, soluble proteins, Superoxide dismutase（SOD）, Malondialdehyde （MDA） of D. inornata and S. costatum are studied under theexposure of different concentrations of HBCD and TBBPA. Base on the above research, toxic mechanisms of HBCD and TBBPA to marine algae are investigated.The main results are listed as follows:（1） The96h-EC₅₀values of HBCD on D. inornata and S. costatum are0.90and0.45mg·L^-1, respectively. While those of96h-EC₅₀of TBBPA on inhibition of thegrowth of D. inornata, S. costatum and C. vulgaris are calculated as5.71,18.08and4.71mg·L^-1, respectively. However, the96h-EC₅₀of HBCD for P. tricornutum and C.vulgari and TBBPA for P. tricornutum could not be detected accurately in theeffective concentration range under the culture condition. Results indicate that HBCDis very highly toxic to D. and S. costatum, while TBBPA is highly toxic to D. inornata,C. vulgaris and median toxic to S. costatum. So the toxicity orders of HBCD andTBBPA on four marine microalgae are S. costatum> D. inornata> C. vulgari> P.tricornutum, C. vulgari> D. inornata> S. costatum> P. tricornutum, respectively.（2） The photosynthetic pigments of D. inornata and S. costatum are influencedby the concentration and exposure time of HBCD and TBBPA. The contents of Chl-a,Chl-c and Car are stimulated at low concentrations and inhibited at highconcentrations and then recovered to the control levels. The Car is most sensitive tolow concentrations of HBCD and TBBPA among three photosynthetic pigments,while Chl-a and Chl-c are sensitive to high HBCD and TBBPA treatments.（3） The soluble protein contents and SOD activities of D. inornata and S.costatum are both induced at low exposure concentrations, and inhibited at highexposure concentrations within the initial24hours. However, contents of MDAincrease significantly with the increasing of concentrations of HBCD and TBBPA.The study reveals SOD-protein relationships occur a long time. There presents asignificant effect-dosage relationships of MDA, indicating the potential of usingMDA as the biomarker for HBCD and TBBPA pollution.