Characteristics of bacterial communities in a rural river water restored by ecological floating beds with Oenathe javanica

Abstract

Ecological floating beds (EFB) can efficiently remove nitrogen and phosphorus from eutrophic water. However, there are significant gaps in our understanding of bacterial community characteristics in water in rural rivers that have been restored by EFBs. In this study, we applied EFBs using Oenathe Javanica to restore a eutrophic rural river in southeast China from March to May in 2018. We then conducted high-throughput sequencing of 16S rRNA from river water samples to develop a comprehensive profile of the bacterial community structure in the river. The richness indices of the bacterial community were higher in the planted area than the open area (the CK area) on March 29 and April 20, as were the Shannon indices on April 20 and May 18. The proportions of Betaproteobacteria, Actinobacteria, Cyanobacteria, Sphingobacteriia, Verrucomicrobiae and Cytophagia were significantly higher in the planted area than the CK area on April 20, when plants on the EFBs were growing rapidly. Root length had stronger relationships with OTUs than plant length, Spad and dry biomass weight in the planted area, while TN, TP, SS, pH and DO had stronger relationships with OTUs than other water quality indexes in the whole river segment. The average relative abundance of genes associated with nitrogen metabolism, methane metabolism and carbon fixation pathways in the planted areas were higher than in the CK area. These findings suggest that use of ecological floating beds (EFB) with Oenathe Javanica under the relatively lower temperatures that occur during early spring has a positive impact on microbial communities that might contribute to the growth and metabolism of microorganisms and help to promote nitrogen removal from rural rivers.