Comparative analysis of heavy metals, gut microbial community and metabolome between bean geese (Anser fabalis) wintering at Caizi and Shengjin lakes, China

Heavy metals are major environmental challenges with significant health implications for migratory waterbirds. Shengjin and Caizi Lakes, located along the Yangtze River, are important stopover and wintering wetlands for migratory waterbirds in the East Asia-Australasian Flyway. The heavy metal, microbial communities, and metabolites in wintering bean geese (Anser fabalis) were analysed in Shengjin (n = 15) and Caizi Lakes (n = 15). In the faecal samples, As, Cr, and Hg concentrations differed significantly between the two sites, whereas the levels of Cd and Pb were not significantly different. Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidota were the dominant gut microbial phyla in geese. The ShannonWiener’s index and PLS-DA analysis results showed significant differences between geese at the two sites. Linear discriminant analysis Effect Size (LEfSe) tests showed that Flavobacterium, Pseudomonas, and Janthinobacterium were significantly enriched in the Shengjin Lake geese, whereas Arthrobacter and Sporosarcina were significantly enriched in the Caizi Lake geese. The LC-MS results indicated that lipids, lipid-like molecules, organic acids and derivatives, and organoheterocyclic compounds were the dominant in faecal metabolic profiles. PLS-DA revealed that all Shengjin Lake and Caizi Lake geese produced distinct clusters. A total of 135 pathways were found to be different between the Shengjin and Caizi lake samples, according to the Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway. Correlation analysis revealed that heavy metals affected the gut microbial community and metabolite composition. A significant correlation was also observed between the gut metabolites and microorganisms. Therefore, our study provides early warnings of environmental pollution of wetland ecosystems for migratory waterbirds.