Jing Dong

Suspended particulate matter (SPM) is a key environmental driver in aquatic ecosystems and plays a significant role in shaping microbial communities, particularly in sediment-rich rivers. Dam construction alters hydrological regimes and creates distinct SPM gradients; however, the response mechanisms of microeukaryotic plankton communities remain poorly understood. In this study, we used 18S rRNA gene high-throughput sequencing to characterize microeukaryotic plankton communities across riverine, lacustrine, and transitional zones of the Xiaolangdi Reservoir on the Yellow River (China). Our results revealed distinct community compositions in the lacustrine zone, with SPM identified as the primary factor driving community differentiation. Alpha diversity was highest in the riverine zone, while beta diversity differences among zones were dominated by species turnover. Dominant taxa included Cryptophyta (44.71% ± 30.79%), Metazoa (18.98% ± 17.71%), Perkinsea (7.97% ± 9.78%), Chlorophyta (7.06% ± 5.80%), and Dinophyta (6.06% ± 6.73%). Metazoa, Dinophyta, and Phaeophyta were enriched in high-SPM riverine waters, whereas Alveolata dominated low-SPM lacustrine zones. Community assembly was primarily deterministic, governed mainly by homogeneous selection, with stochastic processes exerting stronger influence in riverine zones. Network analysis indicated that riverine zones exhibited more complex and stable networks, lacustrine zones showed higher local but lower global connectivity, and transitional zones displayed stronger interactions but lower stability. These findings advance our understanding of microeukaryotic plankton responses to dam-induced environmental changes and provide a basis for assessing biodiversity impacts in regulated river systems.

Aquatic–terrestrial ecotones are highly dynamic biogeochemical hotspots where hydrological fluctuations profoundly influence microbial community structure and ecosystem functioning. However, the mechanisms underlying microbial community responses across hydrological gradients remain insufficiently understood. In this study, 16S rRNA gene sequencing was used to comparatively analyze bacterial communities in the waterward and landward zones of the drawdown area of the Danjiangkou Reservoir. The results showed that bacterial community composition differed significantly between the two zones, and waterlogging markedly increased bacterial α-diversity. Community variation was primarily associated with key environmental factors, including total phosphorus (TP), soil moisture content (SMC), and nitrate nitrogen (NO₃⁻-N). Compared with the landward zone, stochastic processes contributed more to community assembly in the waterward zone, which also exhibited higher network complexity and topological stability. In addition, several keystone taxa were identified, suggesting their potential roles in maintaining network structure and ecological stability. Functional prediction further revealed distinct metabolic potentials between zones, with enhanced anaerobic and redox-related functions in the waterward zone and predominantly aerobic metabolism in the landward zone. These findings suggest that hydrological fluctuations reshape bacterial community structure and potential ecological functions by jointly regulating water availability and nutrient dynamics. This study provides new insights into microbial ecological processes in reservoir riparian zones and offers a scientific basis for the management of aquatic–terrestrial ecotone ecosystems.

In recent years, the public environmental protection consciousness has improved regarding the source of drinking water. However, the risk status and sources of heavy metals (HMs) in the soil around drinking water sources remain unclear. The typical Drawdown Zone (DZ) of Danjiangkou Reservoir is taken as an example in this study. Pollution levels of HMs and associated ecological and human health risks were evaluated under four land-use types during the low-water-level period. The sources of 10 HMs were determined using the positive matrix factorization (PMF) model and correlation analysis. Quantitative source-oriented risk identification was then conducted by integrating risk characteristics with source apportionment. The results indicate that soils in the study area are generally slightly polluted, with comprehensive potential ecological risks at a medium level. Farmland soils exhibit the highest pollution and ecological risk levels, particularly for Hg and Cd. Our Monte Carlo simulation-based human health risk assessment shows that, compared with non-carcinogenic risks, carcinogenic risks should be given further attention. Farmland poses higher health risks than other land-use types, and children are more vulnerable than adults. Four main sources were identified: transportation sources (29.5%), agricultural activities (32%), natural sources (19.3%), and atmospheric deposition (19.2%). The source-oriented risk assessment indicates that agricultural activities are the priority control source for ecological risks (64.7%), with Hg as the primary control element. Transportation and agricultural sources are the primary contributors to carcinogenic risks in children (57.1%) and adults (57.1%), with Ni as the primary control element.

The present study systematically explored the purification effects and response of submerged plants, Ceratophyllum demersum and Myriophyllum spicatum, on toxic and non-toxic strains of Microcystis aeruginosa via indoor co-culture experiments. The results showed that: (1) Both plants significantly inhibited the growth of Microcystis and reduced the concentration of chlorophyll-a (Chla) in the water by rapidly absorbing nutrients such as nitrogen and phosphorus, with no significant differences in the inhibition between toxic and non-toxic strains, indicating that nutrient competition might be the dominant mechanism for algal suppression. (2) C. demersum had higher nitrogen and phosphorus removal efficiency than M. spicatum, but the microcystins (MCs) released by toxic M. aeruginosa inhibited the nutrient removal capacity of both plants. (3) The plants promoted cell lysis of toxic M. aeruginosa and reduced extracellular MCs in the water while accumulating MCs internally, with C. demersum showing stronger MC accumulation and removal ability. (4) Microcystis stress activated the plants’ antioxidant defense systems, increased activities of SOD (Superoxide Dismutase) and CAT (Catalase), and caused membrane lipid peroxidation, increased content of MDA (Malondialdehyde), with toxic M. aeruginosa inducing stronger oxidative stress, and M. spicatum being more severely affected. (5) Plant species and algal toxicity jointly drove changes in the attached microbial community structure. The rhizosphere of M. spicatum specifically enriched Bdellovibrionota, suggesting a potential microbial predation pathway for algal suppression, while C. demersum was more associated with Bacillus and other microbes with allelopathic potential. In summary, C. demersum performed better in nutrient removal, toxin accumulation, and physiological tolerance. This study provides further theoretical support for using submerged plants to regulate cyanobacterial blooms and remediate eutrophic water bodies.

Phytoplankton communities play a crucial role in riverine ecosystems, yet their assembly mechanisms in high-silt environments remain poorly understood. This study investigated seasonal variations in phytoplankton community structure and assembly mechanisms in a riverine environment with high silt loads. Phytoplankton and physicochemical water quality factors were analyzed in the middle and lower reaches of the Yellow River during two seasons: November 2023 (autumn) and April 2024 (spring). A total of 110 algal species from seven phyla were identified, with Chlorophyta being predominant in species richness and Cyanophyta in cell density. Both species richness and abundance were lower in autumn than in spring. The α-diversity analysis revealed that the Pielou’s eveness index was significantly higher in spring compared to autumn. Non-metric multidimensional scaling (NMDS) based on Bray–Curtis distances showed significant seasonal differences in phytoplankton community composition. Furthermore, β-diversity decomposition analysis revealed that turnover was the dominant component in both seasons, but the proportion of nestedness was significantly higher in spring compared to autumn (p < 0.05). Based on the analyses of the dispersal–niche continuum index (DNCI) and the modified stochasticity ratio (MST), this study demonstrates pronounced seasonal variations in the assembly mechanisms governing phytoplankton communities in the middle and lower reaches of the Yellow River. In autumn, stochastic processes, primarily driven by dispersal, accounting for 58.85% of the community assembly. In contrast, deterministic processes, largely shaped by niche selection, contributing 65.05% to the community assembly in spring. The community structure of phytoplankton in this region is shaped by the combined effects of geographical factors, elevation, and environmental variables, with particularly pronounced seasonal variations in environmental drivers—total nitrogen (TN) emerges as the primary factor influencing autumn community assembly, while spring community structure is mainly regulated by silica (SiO₂) and pH. This study deepens the understanding of phytoplankton assembly mechanisms in sediment-rich rivers and provides fundamental data for phytoplankton construction mechanisms and aquatic biodiversity conservation in the middle and lower reaches of the Yellow River.

The effects of toxic and non-toxic Microcystis aeruginosa on the Ceratophyllum demersum–Scenedesmus obliquus system were simulated in the laboratory, and some parameters in relation to these organisms were measured. In this experiment, C. demersum increased the biomass of S. obliquus, and both toxic and non-toxic M. aeruginosa significantly inhibited the colony formation of S. obliquus and inhibited the promotion of S. obliquus biomass. On the 14th day, the soluble polysaccharide content of C. demersum decreased when it was coexisted with S. obliquus, but it rose again because of M. aeruginosa, which significantly increased the protein content of C. demersum. The species composition and diversity of epiphytic microorganisms also vary with different treatments. Proteobacteria is dominant in all the groups, especially in the Toxic_SMC group. In addition, bacteria that can degrade organic pollutants are more abundant in Toxic_SMC group. This study focuses on the defense response of S. obliquus induced by C. demersum under the pressure of toxic or non-toxic M. aeruginosa and evaluates the changes to C. demersum and its epiphytic microorganisms, which provides insights for the study of aquatic plant–algae integrated action systems in eutrophic or cyanobacterial blooms.

Three common floating bed plants, Eichhornia crassipes, Pistia stratiotes, and Ipomoea aquatica, were selected in the present study to investigate their inhibitory effects on toxic Microcystis aeruginosa. The results showed that all three types of floating-bed plants could considerably inhibit the growth of M. aeruginosa and effectively remove the microcystins (MCs) from water systems, among which, E. crassipes and P. stratiotes were more effective in resisting M. aeruginosa, and the removal rate of the intracellular MCs could be up to 100%. In addition, the roots and leaves of the three plants were enriched with a large number of MCs and demonstrated significant antioxidant responses, as evidenced by the increase in the content of catalase (CAT), glutathione peroxidase (GSH-PX), superoxide dismutase (SOD), and malondialdehyde (MDA) in the roots, stems, and leaves of the plants. Furthermore, this study also showed that Proteobacteria, Bacteroidota, Myxococcota, Verrucomicrobiota, and Actinobacteriota dominated the root microorganisms of the three plants. Moreover, a variety of MC-degrading bacteria, including Sphingomonas, Acinetobacter, Novosphingobium, and Pseudomonas, were found at the genus level, which further provides important basic data for the regulation of eutrophic water bodies and the removal of MCs.