Program

Microbes in coastal ecosystems provide fundamental eco-services such as nutrient cycling and pollutants degradation. The abundant and diverse microorganisms harbored in coastal sediment are able to respond rapidly to environmental stresses caused by both hydrodynamic flows and anthropogenic disturbances, resulting in the variation in community diversity as well as ecosystem functioning. However, how microbial diversity and function shift along natural physicochemical gradients and anthropogenic disturbances are not clear. Hangzhou Bay locates in the northern Zhejiang Province and Eastern China Sea. It becomes one of the most seriously polluted coastal areas in China due to the rapid urbanization and intensive development of industry around the bay. In this study, we performed both shotgun metagenomic sequencing and 16S rRNA gene sequencing of sediment samples from nearshore to offshore Hangzhou Bay to study the shifts in microbial community composition and function. Both bacterial and archaeal communities differentiated spatially with significant distance-decay of similarity patterns, while these patterns were mainly strengthen by low-abundance members but weakened by dominant ones. The dominant bacterial species all affiliated with pollution tolerant species of Bacllli, and the dominant archaeal species all affiliated with the potential ammonia-oxidizing archaeal from Marine Group I (MGI). Notably, we found key bacterial OTUs, affiliated to Deltaproteobacteria, Gammaproteobacteria, Phycisphaerae, and Fusobacteriia, increased consistently from nearshore to offshore. The bacterial and archaeal community shifts were mainly correlated with the shifts in seawater salinity, inorganic nitrogen, and sediment nitrate and sulfate contents. Annotation of unassembled metagenomic sequences against KEGG Orthology (KO) database revealed higher gene abundance involving in nitrogen and sulfur metabolisms in offshore than in nearshore. While, metabolic pathways for some xenobiotic chemicals, including benzoate, chlorobenzene, xylene, and phenanthrene, were significantly enriched in the nearshore sites. Most of these compounds are known as intermediates and widely used in pharmacy industry, dye production, and other fine chemical industries. This finding reflects the influence of coastal anthropogenic activities to the microbial communities. Overall, our results provide insights in simultaneous influence of natural and anthropogenic impact on microbial ecology in a highly urbanized coastal ecosystem.