Effects of water stratification and mixing on microbial community structure in a subtropical deep reservoir

Abstract

Microorganisms play pivotal roles within aquatic ecosystems, affecting their structure, functioning and services. However, little is known about the effects of water stratification and mixing on the aquatic microbial community dynamics in subtropical reservoirs. In this study, we explored vertical and seasonal patterns of microbial diversity in the Dongzhen Reservoir (southeast China). Quantitative PCR, quantitative RT-PCR, and 454 pyrosequencing were used for an in-depth characterization of the bacterial community across time (every three months for one year) and space (five different water depths). Our results indicated that thermal and oxygen stratification shaped the phylogenetic composition of microbial communities in the reservoir. There were significant differences in physical, chemical and microbiological parameters between epilimnion and hypolimnion (P < 0.05). The RNA: DNA ratios were significantly lower in epilimnion and metalimnion but rapidly increased in hypolimnion (P < 0.05), suggesting that microorganisms were more active at low temperatures, low dissolved oxygen concentrations and high TN/TP ratios. Redundancy analysis and pathway analysis revealed a complex interplay of various environmental and biological factors by explaining the spatiotemporal variations in bacterial communities. Adaptive reservoir management strategies should consider carefully the effects of water stratification and mixing, together with the distribution patterns of aquatic microorganisms.

Effects of Seasonal Thermal Stratification on the Functional Diversity and Composition of the Microbial Community in a Drinking Water Reservoir

“…As expected, the BCC of the Jinpen Reservoir resembled the composition of some reported freshwater ecosystems, with Proteobacteria, Actinobacteria, Cyanobacteria, and Bacteroidetes as the major bacterial groups [5,18,50]. However, the percentage of each bacterial group was distinct at the level of phylum after stratification.…”

“…The sequences were then binned into operational taxonomic units (OTUs) based on a 97% sequence similarity using Mothur software package (Version 1.7.0). The OTUs which contained one read were removed to avoid possible sequencing error at this step [5,17]. Taxonomic classification of the reads was performed in the Ribosomal Database Project (RDP) database [37,38].…”

“…Thermal regime is strongly associated with the hydrodynamics of these reservoirs, and the water column becomes seasonally thermally stratified and divided into the epilimnion, metalimnion, and hypolimnion [1][2][3]. The metalimnion would limit the transfer of oxygen from the surface to the deeper waters during the stratified period [4,5]. Additionally, an extended period of anoxic condition in the hypolimnion may intensify the deterioration of the water quality [6,7].…”

“…However, the microbial communities in stratified freshwater ecosystems have not been studied to the same extent as those in marine or saline lakes, with different trophic status and morphology. Limited previous research has suggested that each thermal layer in the stratified lakes and reservoirs harbors different bacterial communities [5,18,19]. In addition, other studies based on functional genes, such as the adenosine 5'-phosphosulfate reductase (aprA) and the ammonia monooxygenase A (amoA) genes, showed the strong vertical differentiation of sulfate reducers, sulfur oxidizers, and archaeal ammonia oxidizers along environmental gradients [20,21].…”

The effects of pig manure application on the spread of tetracycline resistance in bulk and cucumber rhizosphere soils: a greenhouse experiment

“…The amplification efficiency (E) was estimated from the slope of the standard curve using the following formula: E = (10 −1/slope ) -1. The efficiency of PCR between 95% and 105% was used for further analysis (Yu et al 2014). …”