Microplastics-related Alterations of Gut Microbiota During Two Early Developmental Stages in Wild Great Cormorant Nestlings (Phalacrocorax carbo)

Microplastics (MPs), as a pervasive pollutant, pose a potential threat to the health of wild animals, especially during early developmental stages, and may disrupt gut microbiota. However, evidence regarding the effects of microplastics on wild birds under natural exposure conditions remains scarce. This study aimed to investigate the association between microplastics and gut microbiota in wild Great Cormorant ( Phalacrocorax carbo ) nestlings during two early developmental stages. We characterized the gut microbiota of nestlings using 16S rRNA high-throughput sequencing and detected microplastics using an Agilent 8700 laser infrared imaging spectrometer (LDIR). The α-diversity, beta-diversity structure and predicted functional profile of the gut microbiota are significantly associated with the MPs attributes (abundance, polymer diversity, particle size), and this association varies with different developmental stages. These findings indicate that early exposure to environmental microplastics can significantly impact the gut microbiota of the Great Cormorant, and this impact varies across developmental stages. Future research needs to investigate the mechanisms by which microplastics affect specific developmental stages of the gut microbiota and assess their long-term effects on individual health. • Characterized the gut microbiota in Great Cormorant nestlings using 16S rRNA sequencing, revealing dominant phyla such as Firmicutes, Proteobacteria, and Fusobacteria. • Identified microplastics (MPs) in the gut of all nestlings, with concentrations varying between developmental stages, although this variation was not significant (p > 0.05). • The MPs attributes (abundance, polymer diversity, particle size) were significantly associated with the alpha diversity and beta-diversity structure of the gut microbiota in wild Great Cormorant nestlings, and this association varies at different developmental stages (p < 0.05). • The predicted functional profile was primarily dependent on the developmental stage (p < 0.05), and the impact of microplastics depended on their interaction with the developmental stage; their individual effects were not significant (p > 0.05).