Nanoplastic pollution changes the intestinal microbiome but not the morphology or behavior of a freshwater turtle

• Published in: The Science of the total environment 2024-07, Vol.934, p.173178, Article 173178
• Main Authors: Gao, Shuo, Zhang, Shufang, Sun, Jiahui, He, Xinni, Xue, Shaoshuai, Zhang, Wenyi, Li, Peng, Lin, Longhui, Qu, Yanfu, Ward-Fear, Georgia, Chen, Lian, Li, Hong
• Format: Article
• Language: English
• Subjects: Behavioral traits; egg shell; embryogenesis; environment; environmental exposure; freshwater; Freshwater turtle; Growth; Gut microbiota; heart rate; intestinal microorganisms; Nanoplastic; nanoplastics; Pelodiscus sinensis; pollution; polystyrenes; probiotics; toxicity; turtles; viability; wastes
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.173178

Humans produce 350 million metric tons of plastic waste per year, leading to microplastic pollution and widespread environmental contamination, particularly in aquatic environments. This subsequently impacts aquatic organisms in myriad ways, yet the vast majority of research is conducted in marine, rather than freshwater systems. In this study, we exposed eggs and hatchlings of the Chinese soft-shelled turtle (Pelodiscus sinensis) to 80-nm polystyrene nanoplastics (PS-NPs) and monitored the impacts on development, behavior and the gut microbiome. We demonstrate that 80-nm PS-NPs can penetrate the eggshell and move into developing embryos. This led to metabolic impairments, as evidenced by bradycardia (a decreased heart rate), which persisted until hatching. We found no evidence that nanoplastic exposure affected hatchling morphology, growth rates, or levels of boldness and exploration, yet we discuss some potential caveats here. Exposure to nanoplastics reduced the diversity and homogeneity of gut microbiota in P. sinensis, with the level of disruption correlating to the length of environmental exposure (during incubation only or post-hatching also). Thirteen core genera (with an initial abundance >1 %) shifted after nanoplastic treatment: pathogenic bacteria increased, beneficial probiotic bacteria decreased, and there was an increase in the proportion of negative correlations between bacterial genera. These changes could have profound impacts on the viability of turtles throughout their lives. Our study highlights the toxicity of environmental NPs to the embryonic development and survival of freshwater turtles. We provide insights about population trends of P. sinensis in the wild, and future directions for research. [Display omitted] •80-nm PS-NPs were able to penetrate the eggshell and enter the developing embryo, resulting in a decrease in the embryo's heart rate.•No significant changes were observed in the morphology or behavior of the hatchlings after exposure to polystyrene.•Nanoplastic exposure led to a decrease in the diversity and homogeneity of the intestinal microbiome in hatchlings.•Thirteen core genera shifted after nanoplastic treatment: pathogenic bacteria increased, beneficial probiotic bacteria decreased, and there was an increase in the proportion of negative correlations between bacterial genera.