Assessment of sediment quality of Yangtze River estuary using zebrafish (Danio rerio) embryos

Abstract

Yangtze River estuary is one of the largest estuaries worldwide. In this study, the sediment quality of Yangtze River estuary was evaluated using zebrafish (Danio rerio) embryos. Freshly fertilized zebrafish eggs (2 h after fertilization) were exposed to the whole sediment and its organic phase of extract, respectively. The parameters, including survival rate, abnormality, hatching rate, and heart rate of the zebrafish embryos, were recorded during the 96-h exposure. The results demonstrated that the concentrations of heavy metals (Zn, Cu, Cd, Ni, Cr, and As) and low-molecular weight PAHs (Fluorene) in the sediment of Yangtze River estuary exceeded their corresponding effects range low values. The maximum concentrations of Zn and Fluorene in the sediment samples were 239.6 microg/g and 45.9 ng/g, respectively. In both whole sediment test and organic extract test, the survival rate and heart rate of zebrafish embryos were reduced, as well as abnormalities and delayed hatching were induced. For example, the highest mortality of the embryos was 39% in the whole sediment exposure. Overall, the occurrence of toxic compounds in the sediment of Yangtze River estuary may have potentially teratogenic effect on biota. The sediment from the upstream of Yangtze River estuary have more observed toxic effects on zebrafish embryos than that form the downstream. Therefore, more attention should be paid to control these pollutants, especially heavy metals in the Yangtze River estuary.