Search

Network analysis has contributed to studies of the interactions of microorganisms and the identification of key populations. However, such analysis has rarely been conducted in the study of reservoir bacterioplankton communities. This study investigated the bacterioplankton community composition in the surface water of the Danjiangkou Reservoir using the Illumina MiSeq sequencing platform. We observed that the bacterioplankton community primarily consisted of 27 phyla and 336 genera, including Actinobacteria, Proteobacteria, and Bacteroidetes, demonstrating the richness of the community composition. Redundancy analysis of the bacterioplankton communities and environmental variables showed that the total nitrogen (TN), pH, chemical oxygen demand (COD), and permanganate index (CODMn) were important factors affecting the bacterioplankton distribution. Network analysis was performed using the relative abundances of bacterioplankton based on the phylogenetic molecular ecological network (pMEN) method. The connectivity of node i within modules (Zi), the connectivity of node i among modules (Pi), and the number of key bacteria were high at the Taizishan and Heijizui sites, which were associated with higher TN contents than at the other sites. Among the physicochemical properties of water, TN, ammonia nitrogen (NH4-N), pH, COD, and dissolved oxygen (DO) might have great influences on the functional units of the bacterial communities in bacterioplankton molecular networks. This study improves the understanding of the structure and function of bacterioplankton communities in the Danjiangkou Reservoir.

Reservoir/lake sediments are potential pollutant acceptors and sources of pollution. The Danjiangkou Reservoir, as the largest drinking water source in China, is the source water area for the Mid-route Project of the South-North Water Diversion. To illustrate the temporal and spatial changes in the environmental risks of both nutrients and heavy metals in the surface sediments of Danjiangkou Reservoir, the levels of pH, OM, TP, TN, and six kinds of metal elements during the period 2011-2016 were measured at five ecological sites. Canadian freshwater sediment quality guidelines for aquatic environments (from the CCME) were used to assess the potential ecological risks. The results showed that the contents of OM, TP, and TN in the surface sediments were 25.85, 0.57, and 1.34 g·kg

Excessive water level fluctuation may affect physico-chemical characteristics, and consequently ecosystem function, in lakes and reservoirs. In this study, we assessed the changes of phytoplankton assemblages in response to water level increase in Danjiangkou Reservoir, one of the largest drinking water reservoirs in Asia. The water level increased from a low of 137 m to 161 m in 2014 as a part of the South–North Water Diversion Project. Phytoplankton assemblages were sampled four times per year before, during and after the water level increase, at 10 sites. Environmental variables such as total nitrogen as well as phytoplankton biomass decreased after the water level increase. Non-metric multi-dimensional scaling analysis indicated that before the water level increase, phytoplankton assemblages showed distinct seasonal variation with diatom dominance in both early and late seasons while such seasonal variation was much less evident after the water level increase. Month and year (before and after) explained 13% and 6% of variance in phytoplankton assemblages (PERMANOVA, p < 0.001) respectively, and phytoplankton assemblages were significantly different before and after the water level increase. Both chlorophytes and cyanobacteria became more abundant in 2015. Phytoplankton compositional change may largely reflect the environmental changes, such as hydrodynamics mediated by the water level increase.

Drinking water safety is increasingly perceived as one of the top global environmental issues. Plankton has been commonly used as a bioindicator for water quality in lakes and reservoirs. Recently, DNA sequencing technology has been applied to bioassessment. In this study, we compared the effectiveness of the 16S and 18S rRNA high throughput sequencing method (HTS) and the traditional optical microscopy method (TOM) in the bioassessment of drinking water quality. Five stations reflecting different habitats and hydrological conditions in Danjiangkou Reservoir, one of the largest drinking water reservoirs in Asia, were sampled May 2016. Non-metric multi-dimensional scaling (NMDS) analysis showed that plankton assemblages varied among the stations and the spatial patterns revealed by the two methods were consistent. The correlation between TOM and HTS in a symmetric Procrustes analysis was 0.61, revealing overall good concordance between the two methods. Procrustes analysis also showed that site-specific differences between the two methods varied among the stations. Station Heijizui (H), a site heavily influenced by two tributaries, had the largest difference while station Qushou (Q), a confluence site close to the outlet dam, had the smallest difference between the two methods. Our results show that DNA sequencing has the potential to provide consistent identification of taxa, and reliable bioassessment in a long-term biomonitoring and assessment program for drinking water reservoirs.

Danjiangkou reservoir is the water resource area of the mid-line project of south to north water division. Zooplanktons are monitored at thirteen ecological stations in Danjiangkou reservoir and its typical branch rivers in August 2010 in order to establish the scientific foundation of the databank of the long-term ecological research and the layout of ecological project of the water resource. The water samples are collected using standard methods. Saprobic system is used to evaluate the trophic status of the water resource area of the min-line project. The samples contained 154 species (varieties), 110 genera of zooplankton, of which rotifea is the most, accounting for 35%, followed by copepods, protozoa and cladoceran. There are 6 species (varieties) saprobic indicators, of which β-mesosaporbic indicators account for 66.7%. No hyper-mesotrophic indicators of zooplankton occurred in the water samples. Therefore, Danjiangkou reservoir is under β-mesosaporbic status and suitable for the requirement of the water quality of the mid-line project.

The subject of the paper is to study the effect of the different river habitat on biological diversity of microalgae in order to reveal the status of algae indicators in the evaluation of river ecosystem health. The study is conducted to compare planktonic algae and epilithic algae in Shendinghe rive (SR) and Qihe river (QR) of Danjiangkou reservoir in August 2010. The trophic status is evaluated by saprobic system. There are 193 species (varieties) belonging to 98 genera and 7 phylums of planktonic algae and 61 species (varieties) belonging to 36 genera and 3 phylums of epilithic algae in the samples of SR. There exist 165 species (varieties) belonging to 82 genera and 7 phylums of planktonic algae and 48 species (varieties) belonging to 10 genera and 4 phylums of epilithic algae in the samples of QR. 15 genera instructions 21 species (varieties) of saprobic indicators are identified in the monitored rivers. The number of oligonucleotide indicators in QR is higher than that in SR, and the number of eutrophication indicators in QR is lower than that in SR. The water quality of QR is Biologically superior to that of SR.