The Joint Effects Of Triclocarban And Estradiol On Daphnia Magna

Environmental hormones are exogenous chemicals which could disturb endogenoushormones in normal physiological processes, thus can destroy the maintainability ofhomeostasis and regulation of growth and development in organisms. Combined effects are atoxicity phenomenon which contain at least two chemicals acting on the organismssimultaneously. Triclocarban (TCC) are antibacterial agents widely used in the international.Due to stable chemical properties, TCC are present in various environmental media. Estradiol(E2) are mainly found in the aquatic environment, considered to be the strongest effects ofenvironmental estrogen hormone. TCC and E2have the properties of hydrophobicity,lipidsolubility and bioaccumulation, posing a seriously threat to ecological environment andhuman health. In order to explore the synergistic toxic effects of E2and TCC on cladocerans,the acute and chronic toxic effects of Daphnia magna, E2or TCC or a combination of themon Daphnia magna, were studied in laboratory. The results showed that:(1) The24h-EC50value was5.2μg·L-1for TCC. Under the exposure of TCC, the body length after firstreproduction of D. magna, the body length of first generation after born and the averagebreeding times were decreased by2%-19.6%,3.5%-24.2%and3%-22%. SOD and CAT wereinduced at low concentration, inhibited at high concentrations. MDA content was graduallyincreased with the increased concentration of TCC.(2) The24h-EC50value was2.57mg·L-1for E2. E2had no significant effect on survival, growth and reproduction. Under the exposureof E2, compared to control group, the body length after first reproduction of D. magna, thebody length of first generation after born and the average breeding times were decreased by0.8-10%,-1.5-9%and4.9-37.2%.SOD and CAT was induced at low concentration, inhibitedat high concentrations. MDA content had a positive correlation relation with E2concentration.(3) Combined exposure of E2and TCC caused pronounced fluctuations on the growth andreproduction of D.magna, showed a synergistic effect, the24h-EC50value was0.8TU.Compared to single exposure (E2and TCC), combined exposure showed more toxicity toD.magna,the body length after first reproduction of D.magna were decreased by2.5%-13.3%,1.3%-3.7%,the body length of first generation after born were decreased by10.5%-24.3%,5.5%-9.1%, the average breeding times were decreased by8.7%-25%, 6.8%-9.8%,the mortality rate(9th day) were increased by33.2%-44.6%,33.2%-24.6%,SODand GST were significantly inhibited,the content of MDA were increased significantly. Ourresult can provide scientific reference for the joint effects of environmental hormones onzooplankton.