Vertical Distribution of Bacterial Community Diversity and Water Quality during the Reservoir Thermal Stratification

Abstract

Reservoir thermal stratification drives the water temperature and dissolved oxygen gradient, however, the characteristic of vertical water microbial community during thermal stratification is so far poorly understood. In this work, water bacterial community diversity was determined using the Illumina Miseq sequencing technique. The results showed that epilimnion, metalimnion and hypolimnion were formed steadily in the JINPEN drinking water reservoir. Water temperature decreased steadily from the surface (23.11 °C) to the bottom (9.17 °C). Total nitrogen ranged from 1.07 to 2.06 mg/L and nitrate nitrogen ranged from 0.8 to 1.84 mg/L. The dissolved oxygen concentration decreased sharply below 50 m, and reached zero at 65 m. The Miseq sequencing revealed a total of 4127 operational taxonomic units (OTUs) with 97% similarity, which were affiliated with 15 phyla including Acidobacteria, Actinobacteria, Armatimonadetes, Bacteroidetes, Caldiserica, Chlamydiae, Chlorobi, Chloroflexi, Cyanobacteria, Firmicutes, Gemmatimonadetes, Nitrospirae, Planctomycetes, Proteobacteria, and Verrucomicrobia. The highest Shannon diversity was 4.41 in 45 m, and the highest Chao 1 diversity was 506 in 5 m. Rhodobacter dominated in 55 m (23.24%) and 65 m (12.58%). Prosthecobacter dominated from 0.5 to 50 m. The heat map profile and redundancy analysis (RDA) indicated significant difference in vertical water bacterial community composition in the reservoir. Meanwhile, water quality properties including dissolved oxygen, conductivity, nitrate nitrogen and total nitrogen have a dramatic influence on vertical distribution of bacterial communities.

Community Compositions of Phytoplankton and Eukaryotes during the Mixing Periods of a Drinking Water Reservoir: Dynamics and Interactions

“…Field sampling was conducted at Jinpen reservoir (34 • 42 -34 • 13 N; 107 • 43 -108 • 24 E) [2], located in the city of Xi'an, Shaanxi province, Northwest China. It is a canyon-shaped reservoir with strong thermal stratification (during summer and autumn), and serves as an important drinking water source with a daily water-supply capacity of 8.0 × 10 5 m 3 , which accounts for 76% of the total water supply for about 8.58 million inhabitants of Xi'an [2,7,41]. The total storage capacity of Jinpen reservoir is nearly 2.0 × 10 8 m 3 [2,7,41].…”

“…It is a canyon-shaped reservoir with strong thermal stratification (during summer and autumn), and serves as an important drinking water source with a daily water-supply capacity of 8.0 × 10 5 m 3 , which accounts for 76% of the total water supply for about 8.58 million inhabitants of Xi'an [2,7,41]. The total storage capacity of Jinpen reservoir is nearly 2.0 × 10 8 m 3 [2,7,41]. It has a water surface area of approximately 4.55 km 2 and a catchment area of 1418 km 2 , with a mean depth of 40 m and a maximum depth of 95 m [2,7].…”

“…Each of the samples was 2.0 L and used for chemical parameter, algal biomass, and water microbial community analyses, respectively. For microbial community analysis, All samples were collected in triplicate by a sterilized water-sampling device [2,41], stored in sterile polyethylene containers (2.0 L), kept at 4 °C, and immediately transferred to the laboratory within 24 h for further processing. Each of the samples was 2.0 L and used for chemical parameter, algal biomass, and water microbial community analyses, respectively.…”

“…The highest OTUs were observed at adepth of 5 m in November, and the lowest were at adepth of 0 m in December (415 and 132, respectively). Similarly, on the basis of the Illumina Miseq sequencing technique, Zhang et al [41] investigated the vertical distribution of bacterial communities during thermal stratification in a drinking water reservoir and observed that the highest and lowest OTUs were found in 5 and 0.5 m, respectively. To explore the dynamic of water eukaryotic community structures, we utilized species-richness estimates (Chao 1) and diversity indices (Shannon, Simpson).…”

Gene copy normalization of the 16S rRNA gene cannot outweigh the methodological biases of sequencing

“…Logically we suggest that GCN in communities of low Shannon diversity (≪2.7) could be beneficial. However, the Shannon diversity of bacterial communities typically range between 3 and 6 in both terrestrial 16–19 and aquatic ecosystems 20,21 , which are likely too diverse for GCN to have an impact as shown for Mock-2 and Mock-20.…”