| As new kinds of persistent organic pollutants (POPs), polybrominated diphenyl ethers (PBDEs) are lipid soluble and can be accumulated in lipid and proteins. The bio-accumulation of PBDEs indicates a potential damage to organisms. Their potential threats to the equilibrium and sustainability of marine ecosystems have raised worldwide concerns. Rotifers, widely distributed in coastal waters, are ideal bioassay animals for ecotoxicological tests because of their sensitivity, short generation time, high assimilation efficiency and relative low requirement for culturing and maintenance in the laboratory. Here, two kinds of PBDEs, tetra-BDE (BDE-47) and Deca-BDE (BDE-209) were applied, and their toxic effects on the survivorship, morphological changes, swimming behavior, population growth, reproduction, antioxidant enzymes, lipid peroxidation and DNA damage of Brachiomis plicatilis were investigated. Systematically analyses of effects on the individuals and population of rotifers were made to find their response to the PBDEs stress. The experiment was also aimed to research the antioxidant defense system responses, lipid peroxidation, DNA damage of the rotifer under the two PBDEs sublethal stress. The objective of this study is to derive toxicological information related to the effects of BDE-47 and BDE-209 on rotifers from different levels of population, individual, molecular, physiological and biochemical of biological organization. The possible effective mechanism and the application of zooplankton for detecting environmental contaminants were discussed. This study is aiming to provide a better understanding of the toxicity and ecotoxicological evaluations of PBDEs, and to assess these indicators for monitoring PBDEs toxicity.The main methods and results are listed as follows:1. Acute toxic effects of BDE-47 and BDE-209 on B. plicatilis(1) The 96h-NOEC was calculated by Probit analysis. The 96h-NOEC value resulted in an estimate of 1.01% for larval B. plicatilis.(2) The 24h-LC50 was estimated by Probit analysis, and the value of BDE-47 was beyond 22 mg/L and that of BDE-209 was beyond 80 mg/L for larval B. plicatilis. The sea water solution of them showed low toxicity in a short time.(3) In accordance with the 24-96 h acute tests, the LC50 value of BDE-47 was always lower than that of BDE-209, suggesting BDE-47 is more toxic than BDE-209.(4) The morphological structure of B. plicatilis were examined by Olympus inverted microscope. The results showed that the morphological structure was damaged by BDE-47 after 96-h exposure, while BDE-209 group changed little.2. Joint toxic effects of BDE-47 and BDE-209 on rotifer BrachionusplicatilisThe joint toxic effects of BDE-47 and BDE-209 were examined while the concentration was 1:1 and the toxicity was 1:1. The Marking additive index method was used to evaluate the joint toxicity and the results of the two ways were similar. The joint toxic effects of BDE-47 and BDE-209 were synergistic at 24 h and 48 h, while the joint toxic effects of those two were antagonistic at 72 h and 96 h.3. Subacute toxic effects of BDE-47 and BDE-209 on population growth and reproduction of B. plicatilisAccording to the 3-day population growth and 4-day resting egg production test results, both BDE-47 and BDE-209 had a significant influence on the population growth and reproduction parameters of B. plicatilis including population growth rate, the ratio of ovigerous females/non-ovigerous females (OF/NOF), the ratio of mictic females/amictic females (MF/AF), resting egg production and the mictic rate, which indicate that these parameters in B. plicatilis population were suitable for monitoring and assessing PBDEs. The relative amounts of BDE-47 were much higher than those of BDE-209 in rotifers after 7-day exposure, which was obtained by GC-MS analysis.4. Effects of BDE-47 and BDE-209 on demographic parameters from life tables, population growth parameters and reproductive costRotifer population demographic parameters from life tables, including age-specific survivorship (lx), age-specific fecundity (mx), net reproductive rate (R0), intrinsic rate of increase (rm), finite rate of increase (A), life expectancy (Eq) and generation time (7), were used as measures of treatment effects. Results from this study have revealed increasingly intense negative effects on many of the rotifer demographic parameters with elevated PBDE concentrations. The two PBDEs have caused the carrying capacity (K) suppressed and the negative influence turned more serious as the concentration rose. Results also revealed that the time to reach growth curve inflection point (Tp) was shortened by PBDEs to different degrees. In general, increased levels of BDE-47 had a more adverse effect on B. plicatilis than BDE-209. In addition, the reproductive cost of B. plicatilis overall decreased when exposed to PBDEs compared to the control.5. Effects of BDE-47 and BDE-209 on the activities of several antioxidant enzyme, lipid peroxidation and DNA damage of B. plicatilisThe study investigated the antioxidant response and DNA damage of BDE-47 and BDE-209 on B. plicatilis. The activities of SOD, CAT, POD, the content of MDA and the degree of DNA alkaline unwinding were selected as the sublethal endpoints. The 48-h exposure showed that in the rotifer, the activity of CAT was restrained throughout the test and the activities of SOD and POD were promoted first and restrained later. Increasing concentration of BDE-47 and BDE-209 could cause the distinct promotion of the content of MDA. The declined F value of DNA alkaline unwinding indicated that, the activities of SOD, CAT and POD were both very sensitive to the two PBDEs. The results above reflected the two PBDEs could significantly undermine the antioxidant capacity of B. plicatilis and cause some degree of damage on DNA of B. plicatilis. Those can be used as biological indicators to detect PBDEs pollution, and correlation analysis showed that there was some correlation among the indicators of B. plicatilis. |
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