Ecological risk assessment of migratory bird feces in plateau wetland: Phosphorus speciation, ARGs, and pathogens

Plateau wetlands are critical habitats for migratory birds, but the potential ecological risks from the large-scale accumulation of migratory bird feces (MBF) remain poorly understood. This study focused on seven wintering waterbird species, including the Grus nigricollis, Grus grus, Fulica atra, Anas strepera, Anas zonorhyncha, Mareca penelope, and Tadorna ferruginea at Caohai Plateau Wetland, sampling across March 2024, January 2025 and March 2025. The phosphorus (P) speciation, antibiotic resistance genes (ARGs), pathogens, and their interactions were assessed using sequential phosphorus extraction, solution 31P-nuclear magnetic resonance (31P-NMR), and shotgun metagenomic sequencing. Results showed that MBF was enriched in nutrients and heavy metals, with Gruiformes feces containing high total P (0.65% dry weight). Orthophosphate accounted for 90.68% of total P and labile NaHCO3-Po constituted the dominant organic P fraction, collectively indicating strong guanotrophication potential. Metagenomic annotation recovered 231 potential pathogens with Staphylococcus aureus, Salmonella enterica, and Pseudomonas aeruginosa as dominant taxa; 21 ARG classes were identified, dominated by multidrug resistance genes (32.14-39.29%). Heavy metal (Cu, Cd, Zn) selection pressure enriched MGEs in avian gut microbiota, thereby facilitating horizontal transfer of ARGs and virulence factors (VFs) and ultimately driving the enrichment of multi-drug resistant pathogens. The low-temperature plateau environment further extended the environmental persistence of these hazardous biological contaminants. This study provides a synergistic risk network linking nutrient loading, heavy metal pollution, antimicrobial resistance, and pathogenic proliferation in MBF-impacted plateau wetlands, providing scientific support for plateau wetland ecological restoration and targeted public health risk mitigation under the One Health framework.