Fig. 1.

Composition and diversity of pier surface microbiomes. a Top 10 phyla across the four surface types. Other phyla were grouped into “Minor/Unclassified.” b The three phyla that were differentially enriched between different surface types and materials. c The mean relative abundances of the corrosion-related bacteria identified on the metal and concrete surfaces. The full names of the microbial corrosion mechanism abbreviations are indicated in the “Materials and methods” section. The Mann–Whitney test was applied to determine the differential enrichment of corrosion-related bacteria between concrete and metal surfaces (***p < 0.001, **0.001 < p < 0.01, *0.01 < p < 0.05). d Contributions by local marine and human skin sources to pier surface microbiomes. e Shannon diversity of microbiomes across different surface types. f Principal coordinate analysis of surface microbiomes based on the species-level abundance matrix ordinated by the Bray–Curtis dissimilarity metric. The normal confidence ellipses indicate the confidence level at 95%