Enhanced gut damage and microbial imbalance in bullfrog tadpoles (Lithobates catesbeiana) exposed to polystyrene microplastics under high-temperature conditions

The potential threat posed by microplastic pollution to ecosystems has garnered widespread attention. Additionally, the combined effects of climate warming and environmental pollutants may further exacerbate the negative impacts on aquatic organisms. In this study, the effects of polystyrene microplastics (PS-MPs) on the oxidative stress status, inflammatory response, and gut microbiota composition of bullfrog tadpoles (Lithobates catesbeiana) were systematically evaluated under different temperatures. Histological analysis, various biomarkers, and microbiome methods were used. Tadpoles were exposed to 0 (control), 100, and 1000 μg/L of PS-MPs at both 25 °C and 32 °C for 28 days. The results showed that compared to low-temperature conditions, PS-MP exposure under high-temperature conditions significantly increased the total antioxidant capacity, glutathione, acid phosphatase, and lysozyme levels in the gut. Additionally, PS-MP exposure under 32 °C significantly disrupted the intestinal epithelial cell structure and increased the expression levels of pro-inflammatory factor genes. Gut microbiota analysis showed that the abundance of Cetobacterium continuously increasing with the concentration of PS-MPs. Under high-temperature conditions, PS-MP exposure further led to a decrease in microbial community diversity. These findings indicate that high-temperature environments exacerbate the negative effects of PS-MP exposure and enhance the oxidative stress and inflammatory response in the intestines of bullfrog tadpoles, which may be the primary factor leading to gut microbiota dysbiosis. This study provides scientific evidence for assessing the environmental risks of microplastics and formulating corresponding environmental protection measures, highlighting the urgency of addressing combined environmental stressors in the context of global warming.