Dietary exposure to microplastic fibers alters physiology, fatty acid profiles, and gut microbiota in Carassius auratus

ABSTRACT Microplastic fibers (MPFs) are a prevalent form of microplastic pollution and pose an emerging threat to aquatic organisms, particularly through dietary exposure in aquaculture systems. However, the biological mechanisms underlying the effects of MPFs introduced via formulated feed remain poorly understood. In this study, we investigated the physiological and microbial consequences of chronic MPFs exposure in Carassius auratus through two distinct pathways: waterborne exposure and feed-mediated exposure via an MPFs-containing diet. These two exposure routes resulted in distinct locomotor impairments, depending on the duration of exposure. Notably, feed-mediated exposure induced progressive physiological disruptions and established a distinct gut microbial community characterized by an increased abundance of pathogenic taxa, such as Aeromonas , suggesting potential risks associated with prolonged MPFs intake through feed. Moreover, integrated analyses of gut microbiota composition and fatty acid profiles revealed significant correlations between specific bacterial taxa and lipid alterations under each exposure condition, highlighting that MPFs-contaminated feed might compromise host metabolic homeostasis. Collectively, our findings underscore that dietary MPFs exposure represents a critical and underrecognized vector of microplastic toxicity, with important implications for fish health and the sustainability of aquaculture practices.