Taurine Alleviates Polystyrene Microplastic-Induced Growth Inhibition and Oxidative Stress in Loach (Paramisgurnus dabryanus) Larvae

Microplastics, ubiquitous emerging contaminants in diverse aquatic environments, can be ingested by aquatic organisms and trigger oxidative stress injury, suppressing growth and development. Taurine is a common functional substance with excellent anti-oxidative stress properties. This study sought to investigate whether dietary taurine could mitigate oxidative stress injury triggered by polystyrene microplastics and to analyse its underlying mechanisms in loach (Paramisgurnus dabryanus) larvae. Loach larvae were exposed to 1000 μg/L polystyrene microplastics for 28 days, with graded dietary taurine supplementation (0.2%, 0.4%, 0.8%, and 1.6%), to investigate taurine’s protective effects and regulatory mechanisms. The growth status, feeding ability, mortality, antioxidant enzyme activities (SOD, CAT, GSH-PX), MDA content, and expression of Nrf2/Keap1 pathway-related genes were determined. Following 28 days of PS-MP exposure, the MP group exhibited a cumulative mortality of 42.9%, with its average body weight reduced to 83.51% relative to the control. Dietary taurine supplementation (≥0.8%) effectively reversed these adverse phenotypes. Notably, taurine did not reduce microplastic accumulation in larvae, indicating its protection is independent of microplastic ingestion. Furthermore, taurine enhanced antioxidant enzyme activities, reduced MDA accumulation, and relieved oxidative stress. Mechanistically, taurine activated the Nrf2/Keap1 signaling pathway to upregulate downstream antioxidant gene expression, eliminate excess ROS, and maintain the stability of the antioxidant system under microplastic stress. This study provides a nutritional mitigation strategy against microplastic toxicity and advances our understanding of the ecological risks posed by microplastics to benthic fish in freshwater aquaculture ecosystems.