Control of Hydraulic Load on Bacterioplankton Diversity in Cascade Hydropower Reservoirs, Southwest China
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MICROBIOLOGY OF AQUATIC SYSTEMS
Control of Hydraulic Load on Bacterioplankton Diversity in Cascade Hydropower Reservoirs, Southwest China Meiling Yang 1 & Jie Shi 1 & Baoli Wang 1
&
Jing Xiao 1 & Wanzhu Li 1 & Cong-Qiang Liu 1
Received: 12 March 2020 / Accepted: 5 May 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Hydroelectric reservoirs are highly regulated ecosystems, where the understanding on bacterioplankton has been very limited so far. In view of significant changes in river hydrological conditions by dam construction, hydraulic load (i.e., the ratio of mean water depth to water retention time) was assumed to control bacterioplankton diversity in cascading hydropower reservoirs. To evaluate this hypothesis, we investigated bacterioplankton composition and diversity using high-throughput sequencing and related environmental variables in eleven reservoirs on the Wujiang River, Southwest China. Our results showed a decrease of bacterioplankton diversity index with an increase of reservoir hydraulic load. This is because hydraulic load governs dissolved oxygen variation in the water column, which is a key factor shaping bacterioplankton composition in these hydroelectric reservoirs. In contrast, bacterioplankton abundance was mainly affected by nutrient-related environmental factors. Therefore, from a hydrological perspective, hydraulic load is a decisive factor for the bacterioplankton diversity in the hydroelectric reservoirs. This study can improve the understanding of reservoir bacterial ecology, and the empirical relationship between hydraulic load and bacterioplankton diversity index will help to quantitatively evaluate ecological effects of river damming. Keywords Bacterioplankton diversity . Environmental factor . Hydraulic load . 16S rRNA . Oxygen stratification . Cascade reservoirs
Introduction Freshwater bacterioplankton has enormous genetic diversity across space and time [1–3], which is currently considered to be shaped by deterministic selection and stochastic processes [4–6]. There is a growing recognition that the deterministic or niche-based processes (e.g., biotic interactions and environmental filtering) mainly govern bacterioplankton community assembly, while the contribution of stochastic or ecologically neutral processes (e.g., migration, drift, and extinction) cannot be ignored [4–6]. Traditionally, deterministic processes usually consist of bottom-up regulation by resource availability (including temperature, pH, dissolved oxygen, light, and nutrients) and top-down control by phytoplankton succession, grazing, and viral lysis [2, 7–10]. Recently, studies have
* Baoli Wang [email protected] 1
Institute of Surface-Earth System Science, Tianjin University, Tianjin 300072, China
reported that water retention time and depth are closely correlated with bacterioplankton composition in some lakes [11–13], and water stratification and mixing have strong effects on microbial community structure in the water column of a subtropical deep reservoir [14
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