[Mixture effects to vitellogenin induction by four environmental estrogens in freshwater fish].

Combined effects of estrogenic compounds to high risk life-form were demonstrated, and the study method on combined effects of environmental contaminant mixture and environmental risk assessment were also discussed. A nonlinear aggression was determined on the changes of plasma vitellogenin concentration in crucian carp via the environmental pollutant exposure concentration, and the concentration-response relationship was determined for the single chemical of estradiol, ethynylestradiol, bisphenol A, and octylphenol, and that of the mixed compounds at equipotent concentrations. The combined effects of the four xenoestrogens were tested using indices of mixture toxicity and the biomathematical models of concentration addition or independent action. Weibull function was indicated as the best-fit function (R2 > or = 0.92) with curve estimation, the 95% confidence limits of effect concentration was achieved using the bootstrap method, the media effective concentration (EC50) with 95% confidence interval was 0.007 9 (0.006 8-0.010 0), 0.098 7 (0.090 0-0.111 0), 63.50 (56.58-70.62) and 250.59 (228.46-271.99) Mg x L(-1) respectively. Results suggested that estrogenic chemicals acted together in an additive manner and the combined effects can be accurately predicted in whole range of exposure concentration by the concept of similar joint action or concentration addition.It is proved as a scientific and feasible method to apply the model of joint action whereas the outcome of indices with a great deal of indetermination.

[Comparison of overwintering and rrecruitment of cyanobacteria in Taihu Lake and Chaohn Lake].

Dynamics of overwintering and recruitment of cyanobacteria were studied in Taihu Lake and Chaohu Lake. The results demonstrated that cyanobacteria sank to the sediment in autumn (November) and recruited to water column in May in Taihu Lake. From November to next May, the cyanobacteria kept growing with an increased growth rate from March to May in the sediment. A similar pattern of overwintering and recruitment of cyanobacteria was found in Chaohu Lake, which showed the cyanobacteria sinking in November and recruitment in spring with the cyanobacteria growing in the sediment, while the cyanobacteria recruited to water column from March to April. Our results showed there was typical overwintering and recruitment of cyanobacteria in Taihu Lake and Chaohu Lake. The numbers of cyanobacteria in sediment represented by the almost same pigments content in different lake areas of Taihu Lake according to nutrient levels probably implied the little relationships of the numbers in sediments with the summer bloomed biomass of cyanobacteria.