The Toxic Effects Of BDE-47 On Two Species Of Marine Microalgae

Polybrominated diphenyl ethers(PBDEs) are a new type of persistent organic pollutants(POPs) which have risk of ecology. Since the 1970 s, polybrominated diphenyl ethers(PBDEs) mixtures are manufactured as flame retardants and used in various products, such as electronic equipment, foam, and textiles. PBDEs has the characteristics of mobility, accumulation and persistence, and these characteristics determine the medium to long term residual and undertake bioaccumulation and biomagnification, which affects the normal physiological activities of the organism. Its impact on the marine environment also has caused the wide attention of researchers all over the world. It is necessary to evaluate the environmental behavior and the toxic effects of PBDEs. But at present, there are few reports about PBDEs on the toxicity effect of Marine microalgae. Microalgae are primary producer in the aquatic ecosystems, and their structure and quantity changes can reflect impacts of pollutants on the primary producers in sea and marine ecosystems. Microalgae are easy to get with the characteristics of sensitive to toxins and propagated rapidly. Study with the microalgae as the ideal indicator organism can get the influence of the pollutants on generations in a short period.2, 2’, 4, 4’-Tetrabromodiphenyl Ether(BDE-47) as the representative isomer of PBDEs has strong toxicity and could widely distributed in marine organisms with the high content.Regarding Dicrateria inornata, Skeletonema costatum, Phaeodactylum tricornutum and Chlorella vulgaris as testing organism, the acute toxic effects of BDE-47 on four marine microalgae are assessed. The 96 h median effect concentrations(96 h-EC50) of BDE-47 on marine microalgae are calculated for comparing toxicity of compounds on algae. Furthermore, the toxic effect of BDE-47 on Dicrateria inornata and Skeletonema costatum were studied. The parameters included chlorophyll fluorescence(Fv/Fm Fv/Fo r ETR ΦPSII), 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 were measured under the exposure of different concentrations of BDE-47. The main results are listed as follows:(1) The 96 h-EC50 values of BDE-47 on D. inornata and S. costatum are 648 μg· L-1 and 163 μg· L-1, respectively. However, the 96 h-EC50 of BDE-47 for P. tricornutum and C. vulgari could not be detected accurately in the effective concentration range under the culture condition. Results indicate that BDE-47 is very highly toxic to D. inornata and S. costatum.(2) The chlorophyll fluorescence parameters(Fv/Fm, Fv/Fo, r ETR, ΦPSII) of S.costatum are influenced by the concentration and exposure time of BDE-47. The Fv/Fm and Fv/Fo of D. inornata are stimulated at low concentrations and inhibited at high concentrations significantly lower than control group; at 24 h, the r ETR and ΦPSII of D. inornata decreased with the increasing of concentration of BDE-47 and the r ETR value returned to control levels at 48 h and 72 h, while the ΦPSII value return to the control group at 96 h.(3) Low concentrations of BDE-47 have no significant influence on the contents of Chl-a and Chl-c of S. costatum. High concentrations could stimulate the contents of Chl-a while inhibit the content of Chl-c. The Car contents of S. costatum increased with the increasing of concentration of BDE-47; Low concentrations of BDE-47 could stimulate the contents of Chl-c while high concentrations could inhibit the contents of Chl-c of D. inornata.(4) In the concentration range the soluble protein of S. costatum changed as induced- inhabited, while the soluble protein of D. inornata was induced. In the concentration range the soluble protein and SOD of two species microalgae are enhanced within 48 h and low concentrations groups return to the control group at 72 h. the high concentration BDE-47 could induce the SOD of S. costatum While could inhabite the SOD of D. inornata. Research shows, contents of MDA increase significantly with the increasing of concentrations of BDE-47.(5) From the results of the scanning electron microscopy(SEM), two kinds of algal cells are damaged with the increasing of concentration of BDE-47. The observation result showed that plasmolysis appeared together with the increasing of the number of vacuoles mitochondria and starch granule.