Temporal and Spatial Characterization of Sediment Bacterial Communities From Lake Wetlands in a Plain River Network Region

Sediment bacterial communities are a vital component of microbial communities in aquatic and terrestrial ecosystems and they play a critical role in lake wetlands. To investigate the effect of season, depth and regional environmental factors on the composition and diversity of bacterial communities in lake wetland sediments, the millions of Illumina reads (16S rRNA gene amplicons) from sediment bacterial communities in different seasons were examined using a technically consistent approach. Results from diversity index, relative abundance, principal component analysis (PCA), redundancy analysis (RDA) and linear discriminant analysis effect size (LEfSe) analysis indicated that the diversity of the bacterial community in summer was generally higher than in other seasons. Proteobacteria was the most abundant phylum in the sediment samples in different seasons (43.15%–57.41%) and different layers (39.66%–77.97%); the autumn sediments were enriched with Firmicutes (5.67%) and Chloroflexi (12.5%); in all four seasons the sediments were enriched with Betaproteobacteria (14.98%–23.45%), Gammaproteobacteria (11.98%–14.36%) and Deltaproteobacteria (8.68%–14.45%). In the bottom sediments (10–25 cm) Chloroflexi were abundant (average value 10.42%), while Bacteroidetes was the dominant phylum in the surface sediments; and redundancy analysis found that total phosphorus (TP) (P = 0.036) was the main environmental factor influencing the sediment bacterial community in different layers. This study provides a reference for further understanding the effects of seasonal changes on sediment microorganisms in lake wetlands.

Characteristics of planktonic and sediment bacterial communities in a heavily polluted urban river

Urban rivers represent a unique ecosystem in which pollution occurs regularly, altering the biogeochemical characteristics of waterbodies and sediments. However, little is presently known about the spatiotemporal patterns of planktonic and sediment bacterial community diversities and compositions in urban rivers. Herein, Illumina MiSeq high-throughput sequencing was performed to reveal the spatiotemporal dynamics of bacterial populations in Liangtan River, a heavily polluted urban river in Chongqing City (China). The results showed the richness and diversity of sediment bacteria were significantly higher than those of planktonic bacteria, whereas a strong overlap (46.7%) in OTUs was identified between water and sediment samples. Bacterial community composition remarkably differed in waters and sediments. Planktonic bacterial communities were dominated by Proteobacteria, Bacteroidetes, Cyanobacteria and Actinobacteria, while sediment bacterial communities mainly included Proteobacteria, Actinobacteria, Chloroflexi and Bacteroidetes. Additionally, several taxonomic groups of potential bacterial pathogens showed an increasing trend in water and sediment samples from residential and industrial areas (RI). Variation partition analysis (VPA) indicated that temperature and nutrient were identified as the main drivers determining the planktonic and sediment bacterial assemblages. These results highlight that bacterial communities in the polluted urban river exhibit spatiotemporal variation due to the combined influence of environmental factors associated with sewage discharge and hydropower dams.