Diversity, functional potential, and assembly of bacterial communities in metal(loid)-contaminated sediments from a coastal industrial basin

A comprehensive understanding of ecological processes related to bacterial communities in these ecosystems is critical for improving the sustainability of estuarine-coastal ecosystem functions. However, the community composition, func-tional potential, and assembly mechanisms of bacterial community in metal(loid)-contaminated estuarine-coastal hab-itats remain poorly understood, especially along lotic systems extending from rivers to estuaries and to bays. Here, we collected sediment samples associated with sewage outlets from rivers (upstream/midstream of sewage outlet), estu-aries (sewage outlets), and Jinzhou Bay (downstream of sewage outlets) within Liaoning Province, China in order to evaluate the relationships between microbiome and metal(loid) contamination. Sewage discharge markedly increased the concentrations of metal(loid)s in sediments, including of As, Fe, Co, Pb, Cd, and Zn. Significant discrepancies in alpha diversity and community composition were observed among the sampling sites. The above dynamics were pri-marily caused by salinity and metal(loid) concentrations (i.e., of As, Zn, Cd, and Pb). Furthermore, metal(loid) stress significantly increased abundances of metal(loid)-resistant genes, but decreased abundances of denitrification genes. Dechloromonas, Hydrogenophaga, Thiobacillus, and Leptothrix were denitrifying bacteria present within sediments of this estuarine-coastal ecosystem. Moreover, the stochastic processes dominated the community assembly in estuary offshore sites, while deterministic processes dominated river community assembly mechanisms. Salinity and total ni-trogen concentration, rather than metal(loid) concentrations, governed the assembly processes in these sites. Overall, these elucidate mechanisms involved in constructing community diversities, functional potential, and assembly.

Automated summary

A comprehensive understanding of bacterial communities in metal(loid)-contaminated estuarine-coastal habitats is important for improving ecosystem functions. This study collected sediment samples from different sites in Liaoning Province, China to evaluate the relationship between microbial community and metal(loid) contamination. The results showed significant variations in community diversity and composition, primarily influenced by salinity and metal(loid) concentrations. Metal(loid) stress increased metal(loid)-resistant genes, but decreased denitrification genes. Stochastic processes dominated community assembly in estuary offshore sites, while deterministic processes dominated river community assembly mechanisms.