Response and contribution of bacterial and archaeal communities to eutrophication in urban river sediments.

Excessive loading of nitrogen (N) and phosphorus (P) that leads to eutrophication mutually interacts with sediment microbial community. To unravel the microbial community structures and interaction networks in the urban river sediments with the disturbance of N and P loadings, we used high-throughput sequencing analysis and ecological co-occurrence network methods to investigate the responses of diversity and community composition of bacteria and archaea and identify the keystone species in river sediments. The alpha-diversity of archaea significantly decreased with the increased total nitrogen (TN), whereas the operational taxonomic unit (OTU) number of bacteria increased with the increase of available phosphorus (AP). The beta-diversity of archaea and bacteria was more sensitive to N content than P content. The relative abundance of predominant bacterial and archaeal taxa varied differently in terms of different N and P contents. Complexity and connectivity of bacteria and archaea interaction networks showed significant variations with eutrophication, and competition between bacteria became more significant with the increase of N content. The sensitive and the highest connective species (keystone species) were identified for different N and P loadings. Total carbon (TC), water content (WC), microbial alpha-diversity and interaction networks played pivotal roles in the N and P transformation in urban river sediments.