Analysis of multi-medium microbial communities in the habitat of Recurvirostra avosetta on shell bar islands

Investigations into the ecological effects of feces from Recurvirostra avosetta (Pied Avocet) are frequently restricted by sample degradation and instability. To tackle this challenge, the study adopted a multi-medium composite analytical approach that encompasses water, aquatic plants, soil, and nest sediments. This approach allows for an indirect assessment of potential associations between R. avosetta activities and microbial communities within shell ridge wetlands. The results show marked specificity in the microbial community structure across the four media, with only 12 amplicon sequence variants (ASVs) being shared among all samples. At the phylum level, Proteobacteria was the dominant phylum, while distinct differences were observed at the genus level. Soil exclusively contained the nitrogen - cycling genus Fodinibius; nest sediments were rich in unclassified Balneolaceae, a halotolerant group; and water and aquatic plant samples were predominantly composed of aquatic photosynthetic taxa. Alpha diversity analysis revealed that aquatic plants supported significantly higher microbial richness and diversity compared to the other media, acting as a core reservoir for maintaining the ecological functions of habitat microorganisms. Beta diversity, evaluated through non - metric multidimensional scaling (NMDS) and permutational multivariate analysis of variance (PERMANOVA), showed a high similarity in community composition between soil and nest sediments. Microbial source tracking indicated that among the measured sources (water, aquatic plants, soil), soil showed the highest contribution to nest sediment microbiota; however, unknown sources (likely including avian feces, which were not measured) accounted for the majority. Functional predictions showed enrichment of nitrate reduction and hydrocarbon degradation in nest sediments. Variations in Fodinibius abundance in soil corresponded with potential nitrogen input from bird activity, and fluctuations in unclassified Balneolaceae in nest sediments may indicate salinity or pollution stress. Due to the observational design without control sites or bird activity quantification, these patterns should be interpreted as habitat characteristics rather than causal evidence.