Relationship Between the Vertical Distribution of Nutrients and Bacterial Community Structures in Sediment Interstitial Waters of Stratified Reservoirs with Different Water Temperatures

Abstract

In order to study the relationship between the vertical distribution of nutrients and bacterial community structures in sediment interstitial waters of stratified reservoirs with different water temperatures, MiSeq high-throughput sequencing was used to analyze and compare the structural characteristics of sediment bacterial communities after reservoirs were built. Additionally, redundancy analysis (RDA) was used to assess the bacterial communities and environmental factors with Cannoco software. The results showed that the temperature difference between the surface and bottom layer of the Xiaowan Reservoir was 3.3℃, and the maximum thermal gradient was 0.2℃·m-1; thus, it was a typical stratified reservoir. The temperature difference between the surface and bottom layer of the Manwan Reservoir was 0.1℃; thus, it was a typical mixed reservoir. The average concentrations of NH4+-N and NO3--N in sediment interstitial waters of the Xiaowan Reservoir were 2.233 mg·L-1 and 0.030 mg·L-1, while those of Manwan were 2.569 mg·L-1 and 0.016 mg·L-1, respectively. In the different reservoirs, the concentrations of NH4+-N showed upward trends, and while variation of NO3--N was not obvious, the content of NO3--N reached a minimum value in the deep layer. In comparisons between reservoirs, only NO3--N showed a significant difference, in which Xiaowan had obviously higher concentrations than Manwan. The bacterial community structures in the Xiaowan and Manwan reservoir sediments had the same dominant bacteria at the phylum, class, and genus levels. The differences of water temperature stratification had no significant effect on nutrients and microorganisms in the sediments. Under the influence of other factors, the denitrifying bacteria in the Manwan Reservoir sediments were more abundant than those in the Xiaowan Reservoir, and the nitrifying bacteria and anammox bacteria in the Xiaowan Reservoir sediments were more abundant than those in the Manwan Reservoir. In the same reservoir, the denitrifying bacteria in the bottom of the sediments were more abundant, and the organic degradation bacteria, nitrifying bacteria, anammox bacteria, and phosphate-solubilizing bacteria were less abundant in this zone. These trends contributed to the differences of nutrients vertically in the different reservoirs.