[Bacterial Community Composition in Channel Sediment in Response to Mariculture Wastewater Drainage]

The impact of mariculture on the ecological environment of sediments in surrounding waters is intensely debated. Microbial communities are considered to be keystone indicators of lineage responses to changes in environmental quality. To examine the mariculture effects, we collected channel sediment from four sites in the culture area including oneintake canal, one outfall, and two outlet canals. On the basis of bacterial 16S rRNA gene and phospholipid fatty acid (PLFA) technology, we used Illumina MiSeq sequencing applied to the analysis results to explore the effects of mariculture wastewater drainage on the bacterial community structures in the sediment. The results revealed that Proteobacteria, including γ-Proteobacteria, δ-Proteobacteria, and α-Proteobacteria, were the dominant lineages of bacteria at the four sites. The microbial biomass of the sediment increased significantly owing to the effects of mariculture wastewater drainage. The relative abundance of Actinobacteria and ammoniated microorganisms decreased, whereas the relative abundance of Bacteroidetes increased. The results of non-metric multidimensional scaling (NMDS) analysis indicated that most of the sediment bacterial communities clustered by influent and effluent. The diversity indicated that the mariculture wastewater drainage decreased the bacterial diversity, and redundancy analysis (RDA) indicated that the most obvious correlation occurred between ammonia nitrogen and bacterial community structures. In summary, the mariculture wastewater drainage resulted in significant changes in the physical and chemical properties and structures of bacterial communities in the aquaculture channel sediment. This indicates that the long-term direct discharge of aquaculture wastewater would excessively contaminate a channel environment and might further pose a threat to the offshore ecological environment.