Bacterial community response to chronic heavy metal contamination in marine sediments of the East China Sea

Marine sediments act as a sink for various heavy metals, which may have profound impact on sedimentary microbiota. However, our knowledge about the collaborative response of bacterial community to chronic heavy metal contamination remains little. In this study, concentrations of seven heavy metals (As, Cd, Cr, Cu, Hg, Pb, and Zn) in sediments collected from the East China Sea were analyzed and Illumina Miseq 16 S rRNA sequencing was applied to characterize the structure of bacterial community. Microbiota inhabiting sediments in the East China Sea polluted with heavy metals showed different community composition from relatively pristine sites. The response of bacterial community to heavy metal stress was further interrogated with weighted correlation network analysis (WGCNA). WGCNA revealed ten bacterial modules exhibiting distinct co-occurrence patterns and among them, five modules were related to heavy metal pollution. Three of them were positively correlated with an increase in at least one heavy metal concentration, hubs (more influential bacterial taxa) of which were previously reported to be involved in the geochemical cycling of heavy metals or possess tolerance to heavy metals, while another two modules showed opposite patterns. Our research suggested that ecological functional transition might have occurred in East China Sea sediments by shifts of community composition with sensitive modules majorly involved in the meaningful global biogeochemical cycling of carbon, sulfur, and nitrogen replaced by more tolerant groups of bacteria due to long-term exposure to low-concentration heavy metals. Hubs may serve as indicators of perturbations of benthic bacterial community caused by heavy metal pollution and support monitoring remediation of polluted sites in marine environments.