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 31 P-nuclear magnetic resonance ( 31 P-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 NaHCO 3 -P o 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.