[Effects of Microplastics on Embryo Hatching and Intestinal Accumulation in Larval Zebrafish Danio rerio]

Microplastics have been frequently detected in aquatic environments, and there are increasing concerns about the potential effects on aquatic organisms. In this study, the effects on hatching and the intestinal accumulation in embryos and larvae exposed to two sizes of polystyrene (PS) microplastics were evaluated. The two PS were green fluorescent polyethylene microplastics with 10 μm size (10GF-PM) and red fluorescent polystyrene microplastics with 0.5 μm size (0.5RF-PM). The results showed no significant difference between hatching rates compared with that of the control group of Danio rerio embryos after exposure for three days at 10-500 mg·L^-1 10GF-PM, while the incubation rate was 37% at 500 mg·L^-1 0.5RF-PM. The average survival rates of five day post fertilization larvae exposed to 10, 100, 200, and 500 mg·L^-1 10GF-PM solutions were 80%, 54%, 44%, and 41%, and were 62%, 37%, 25%, and 12% in corresponding concentration of 0.5RF-PM solutions. A quantitative fluorescence analysis showed that the accumulation of 10GF-PM and 0.5RF-PM in larval intestines increased with the increase in the microplastic concentration, and the fluorescence values were 0.06, 0.53, and 1.84 and 0.63, 2.32, and 3.45 after exposure to 10, 100, and 500 mg·L^-1 10GF-PM and 0.5RF-PM solutions for 0.5 h, and were 0.03, 0.08, and 0.56 and 0.06, 0.41, and 1.56 after transferred larval to clear water for 24 h, respectively. The negative effect of microplastics on zebrafish was related to the concentration and particle size:the higher the concentration, the lower the embryo hatching rates; the smaller the particle size, the easier it was to accumulate in the intestines.