Abstract
The spatial and temporal distribution of the archaeal community and its driving factors in the sediments of large-scale regulated rivers, especially in rivers with cascade hydropower development rivers, remain poorly understood. Quantitative PCR (qPCR) and Illumina MiSeq sequencing of the 16S rRNA archaeal gene were used to comprehensively investigate the spatiotemporal diversity and structure of archaeal community in the sediments of the Lancang River cascade reservoirs (LRCR). The archaeal abundance ranged from 5.11×104 to 1.03×106 16S rRNA gene copies per gram dry sediment and presented no temporal variation. The richness, diversity, and community structure of the archaeal community illustrated a drastic spatial change. Thaumarchaeota and Euryyarchaeota were the dominant archaeal phyla in the sediments of the cascade rivers, and Bathyarchaeota was also an advantage in the sediments. PICRUSt metabolic inference analysis revealed a growing number of genes associated with xenobiotic metabolism and carbon and nitrogen metabolism in downstream reservoirs, indicating that anthropogenic pollution discharges might act as the dominant selective force to alter the archaeal communities. Nitrate and C/N ratio were found to play important roles in the formation of the archaeal community composition. In addition, the sediment archaeal community structure was also closely related to the age of the cascade reservoir and hydraulic retention time (HRT). This finding indicates that the engineering factors of the reservoir might be the greatest contributor to the archaeal community structure in the LRCR.
Highlights
The river reservoir system is an important link for the transportation of various biogenic elements to the ocean in the basin surface ecosystem [1,2,3]
The total nitrogen (TN) content in sediments ranged from 647.8 to 1888.5 mg/kg; the TN content was higher in the lake section than in the transition section, exhibiting a very high significant difference spatially (P < 0.01)
Chen et al [47] showed that the abundance of bacteria in the sediments of the nearshore zone of the Lancang River reservoir system would be increased by exogenous organic carbon, but no specific study on the archaeal community in the sediments of the deep-water area of the reservoir was conducted
Summary
The river reservoir system is an important link for the transportation of various biogenic elements to the ocean in the basin surface ecosystem [1,2,3]. Archaeal communities in the sediments of Lancang River cascade reservoirs depositing the sediments and increasing the risk of eutrophication of the reservoir water, which may lead to a change in the biogeochemical cycle of the source material and the corresponding environmental problems [8,9,10,11]. Compared with the overlying water of the reservoir, the sediment of the reservoir is considerably rich in environmental information regarding regional geological structure-activity, geological environment background, climate change, and human activities. The physical, chemical, and biological characteristics of the reservoir sediment remain relatively stable for a short period, which can allow for the "recording" of the disturbance of the reservoir [12,13,14]. Researchers aim to reveal the characteristics of the reservoir environment, biological succession, and the migration and transformation of pollutants
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