Comparative developmental toxicity of eight typical organic pollutants to red sea bream (Pagrosomus major) embryos and larvae

The red sea bream (Pagrosomus major) 48-h embryo-larval bioassay was used to assess and compare the developmental toxicities of eight typical organic pollutants, including polycyclic aromatic hydrocarbons (PAHs), organophosphorus pesticides, polychlorinated biphenyls (PCBs) and alkylphenol. Toxicological endpoints such as survival rates of P. major embryos or larvae and the rates of hatching and of malformation (oedema, condensed blood, spinal curvatures or eye abnormalities) were noted and described within 48 h of exposure. The LC₅₀, EC₅₀, no-observed-effect concentration (NOEC) and lowest-observed-effect concentration (LOEC) were calculated, based on the dose-response relationship. The results showed that exposures to all of the selected organic pollutants except for methyl parathion produced acute toxic effects on P. major embryos and larvae, at different levels of exposure. The levels of acute toxicity of the eight typical organic pollutants for P. major embryos and larvae showed the following trend: benzo(a)pyrene > malathion > PCB 126 > pyrene > nonylphenol > phenanthrene > monocrotophos > methyl parathion. However, the larvae were more sensitive to these pollutants than embryos, according to the calculated LC₅₀, EC₅₀, NOEC and LOEC. This increased sensitivity of larvae could have resulted from losing the natural barrier function of the egg shell membrane. Benzo(a)pyrene, malathion, nonylphenol and monocrotophos delayed the development of P. major for both embryos and larvae, and decreased the hatching rate of the embryos. These results implied that the development of fish embryos and larvae could serve as potential biomarkers for evaluating organic contamination in the aquatic environment. The marine economic fish P. major was more sensitive to PAHs than the model fish, marine medaka (Oryzias melastigma). The estimated safe concentrations (SCs) for marine economic fish, as determined in our research, could provide a reference for the formulation of water quality criteria.