Toxicity of Organic Extracts in Water from Qiantang River to Zebrafsh Embryos

Objective To assess the mutagenicity of organic pollutants extracted from water in Qiantang River during wet and dry seasons and the teratogenic effects on early development of zebrafish embryos of organic pollutants exacted during dry season in 2010.

Methods Water samples(100 L) were each collected from 18 spots in Qiantang River during wet and dry seasons. Organic pollutants in water samples were extracted using XAD-2 resin. The mutagenicity of the organic extracts sampled at wet and dry seasons at concentrations of 0.6, 1.25, 2.5, and 5 L/dish was examined by Ames assay. Zebrafish embryos at 6 h post fertilization(hpf) were exposed by microinjection to the organic extracts in water collected in dry season(5 L/mL). The injection volume was 5 nL. Embryos were observed under microscope every 24 h throughout 5 days, and the mortality and deformity rates were recorded.

Results A higher level of mutagenicity was found in extracts from water collected in dry season than in wet season. Apart from sampling site 3, water samples from section A located in the upstream of Qiantang River showed strong mutagenicity in both wet and dry seasons. In wet season, the organic extracts of water in sampling sites 9 and 14 showed mild positive mutagenicity in the sections B and D, while no obvious mutagenicity was observed in the samples of sections C and E. Compared with wet season, in dry season the mutagenicity of organic extracts was elevated in water collected in sections B, C, and E, while in section D the mutagenicity was relatively lower with positive samples detected in sampling site 14. In the zebrafish embryo test, the organic extracts in water collected in dry season led to lethality in all treatment groups with less than 10%, and primarily disrupted the development of heart, brain, liver, as well as swim bladder inflation and yolk sac absorption. The deformity rates were 30%-90% in zebrafish embryos exposed to the organic extracts from sections A and B and 50%-100% for section C. Comparatively, the teratogenic effects were lower in sections D and E, and the deformity rates were 20%-50% and 40%-60% respectively.

Conclusion The organic extracts in water from Qiantang River present mutagenicity and teratogenic effects on zebrafish embryos. The mutagenicity of the water organic extracts in dry season is greater than that in wet season.