Chemical pollution drives taxonomic and functional shifts in marine sediment microbiome, influencing benthic metazoans.

Microbial communities in marine sediments contribute significantly to the overall health and resiliency of marine ecosystems. However, increased human disturbance undermines biodiversity and, hence, natural functionality provided by marine sediments. Here, through a deep shotgun metagenomics sequencing of the sediment microbiome and COI metabarcoding of benthic metazoans, we demonstrate that >50% of the microorganisms' and metazoan's taxonomic variation can be explained by specific chemical pollution indices. Interestingly, there was a significant correlation between the similarity in microbiome communities' taxonomical and functional attributes and the similarity of benthic metazoans community composition. Furthermore, mediation analysis was conducted to evaluate the microbiome-mediated indirect effect, suggesting that microbial species and functions accounted for 36% and 26%, respectively, of the total effect of pollution on the benthic metazoans. Our study introduces a multi-level perspective for future studies in urbanized coastal areas to explore marine ecosystems, revealing the impact of pollution stress on microbiome communities and their critical biogeochemical functions, which in turn may influence macrofaunal composition.