During a survey of freshwater diatoms in high-altitude streams of the Yarlung Zangbo River Basin, Tibet, China, a new species, Cymbella yangbajainensis sp. nov., was found. Its morphology is described in detail based on observations using light and scanning electron microscope. The new species is characterized by strongly dorsiventral valves with capitate apices, a distinct linear-elliptical central area, and the presence of 5-10 round to oval stigmata of varying sizes, which open at the ends of the central ventral striae. The striae are partly biseriate and irregularly arranged in the central and apical portions. Internally, the areolae are rounded to oblong and occluded by silica plates. Valves are 48.7-64.3 & micro;m long, 11.9-14.5 & micro;m wide, with a length-to-width ratio of 3.8-4.9 (n = 34). The striae density is 8-11 in 10 & micro;m at the valve center, increasing to 10-14 in 10 & micro;m towards the apices; the areolae density is 23-32 in 10 & micro;m. The axial area is narrow and follows the curvature of the valve. Cymbella yangbajainensis is compared with morphologically similar taxa: C. tumida, C. percapitata, C. subtruncata, C. arctissima, C. amplificata, C. cistuliformis, C. jachalensis, and C. menyuanensis. It is distinguished from these species by a combination of features including valve dimensions and outline, stria and areola density, and the number and morphology of stigmata.

Taste and odor (T&O) compounds derived from cyanobacterial blooms pose escalating threats to freshwater security worldwide, yet the drivers of specific T&O metabolites remain poorly constrained. Here, we investigated the dual effects of nitrogen (N) sources and concentrations on the production of β-cyclocitral and β-ionone, two algal-derived T&O compounds, through integrated field surveys (54 sites across lakes and rivers) in the eutrophic lower Yangtze River, China, and laboratory cultivation of typical cyanobacteria (Microcystis aeruginosa and Pseudanabaena cinerea). Our field data revealed that the concentrations of β-cyclocitral and β-ionone in lakes and rivers were not significantly different, but increased with the trophic level index. Redundancy analysis and Mantel analysis showed that Microcystis and Pseudanabaena were potentially dominant contributors to β-cyclocitral and β-ionone in the water column. Structural equation modeling and variation partitioning analysis showed that enhanced nitrate (NO3--N) significantly promoted the production of these compounds. Laboratory experiments demonstrated that inorganic N (NaNO₃) maximized total T&O yields by promoting algal biomass, whereas organic N (urea and glutamic acid) elevated the T&O production per unit biomass by 1.5- to 9.5-fold. Notably, Pseudanabaena exhibited a 2.3-fold higher β-ionone yield than Microcystis, with greater sensitivity to N concentrations. Our study highlights the critical role of nitrogen pollution, both source and concentration, in the production of T&O compounds by phytoplankton and provides reference data for managing T&O issues in rivers and shallow lakes.

Cyanobacterial blooms pose a major threat to aquatic ecosystem health and water quality. Anticyanobacterial bacteria are promising for bloom mitigation, yet their time-resolved inhibitory mechanisms in cyanobacteria remain poorly understood. Here, we isolated a potent anticyanobacterial strain, Enterobacter cloacae TL3, from the eutrophic Taihu Lake and systematically elucidated its time-dependent, multi-target inhibitory mechanism against the dominant bloom-forming cyanobacterium Microcystis aeruginosa. By integrating short-term phenotypic assays with time-resolved transcriptomic profiling, we revealed a distinct temporal cascade of cellular disruption triggered by the sterile filtrates of strain TL3. Within 6 h, sterile filtrates of TL3 triggered extensive transcriptional reprogramming in M. aeruginosa, primarily disrupting Photosystem I (PSI) function and cellular defense pathways. After 12 h, microscopic observation revealed severe structural damage, including cell wall rupture, thylakoid membrane disintegration, complete inhibition of PSI inactivation, and a significant decline in the electron transport of Photosystem II (PSII). Cyanobacterial cells exhibited marked stress responses, characterized by enlargement of intracellular poly-β-hydroxybutyrate (PHB) granules associated with osmotic balance. A substantial downregulation of genes was further revealed by transcriptomic analyses in pathways including cell wall biosynthesis (C789_RS10970), PSII structural components (psbC, psbD), as well as pigment production, self-defense, and DNA repair (cmr4, ruvA). Collectively, these multi-layered impairments ultimately led to irreversible cellular collapse. Our study elucidates a previously unrecognized multi-target anticyanobacterial mechanism in E. cloacae TL3, providing new insights for the development of sustainable strategies to mitigate cyanobacterial blooms in eutrophic waters.

In this study, we describe a new epiphytic diatom species, Tryblionella chongmingensis sp. nov., discovered in the Nanheng Diversion Canal and surrounding small waterways on Chongming Island, Shanghai, China. Observations using light and scanning electron microscopy reveal key morphological features: longitudinal valve undulation with its lowest point on the proximal side and the absence of an axial sternum served as the diagnostic basis for its placement within the aphyletic group. The species is characterized by a relatively large cell size and is distinguished from similar taxa by distinct traits: the presence of a central nodule and valve constriction compared to T. rabenhorstii; the absence of a marginal ridge and reticulate thickenings on the axial sternum compared to T. plana var. fennica; and unique mantle poration (with three types) and pronounced grooves compared to T. scalaris. Ecologically, T. chongmingensis exhibits moderate halotolerance, aligning with the brackish preferences of other Tryblionella species, suggesting its potential as an indicator for brackish waters.

Understanding the assembly mechanisms of bacterial communities is pivotal for deciphering biogeochemical cycles and ecosystem functioning in lacustrine systems. However, systematic comparisons of community assembly processes between free-living (FL) and particle-attached (PA) bacterioplankton across distinct geographic regions remain limited. Here, we employed high-throughput 16S rDNA sequencing, null models, and Raup-Crick analyses to investigate bacterial communities in plateau (Yunnan) and plain (Yangtze River Delta) lakes in China, characterized by contrasting anthropogenic pressures. Results revealed that stochastic processes, particularly homogenizing dispersal, dominated FL bacterial assembly in both regions. In contrast, PA communities exhibited spatial divergence: stochastic processes prevailed in plateau lakes, while deterministic processes governed anthropogenically impacted plain lakes. Mantel tests identified mineral ions (e.g., Co, V, Pb) as critical regulators of PA community assembly, alongside traditional factors like nutrients, phytoplankton (chlorophyll a), and submerged macrophytes. Notably, stochasticity increased with trophic status, driven by enhanced drift in eutrophic waters. Our findings underscore the interplay between bacterial lifestyle, environmental heterogeneity, and anthropogenic impacts in shaping microbial assembly, providing critical insights for predicting ecological responses to environmental change.

Biodiversity has become a central focus in ecological research, playing a critical role in biological conservation and environmental management. Beta diversity can be partitioned into Local Contributions to Beta Diversity (LCBD), a metric used to evaluate the site-specific conservation value of ecosystems. This study applied the LCBD framework to identify watersheds of high conservation value across spatial gradients in the U.S. freshwater fish communities, comparing compositional uniqueness before and after species invasions. Based on an extensive dataset spanning more than 800 freshwater fishes across 1873 communities, we employed Boosted Regression Trees (BRT) to quantify the key drivers underlying changes in LCBD. Our findings provide spatially explicit insights for invasion-related biodiversity conservation and management. The results revealed that, despite only minor shifts occurring in most watershed-level contributions, significant regional disparities emerged, notably in the western and eastern coast U.S. This was reflected in the sesLCBD range, which shifted from (-4.33, 4.95) historically to (-4.53, 6.68) at present. Watersheds with high nonnative species exhibited reduced LCBD. Boosted Regression Trees (BRTs) explained 69.12% of the deviance in sesLCBD changes and identified the percentage of nonnative species as the dominant driver. This relationship was nonlinear, with sesLCBD declines intensifying at higher invasion levels. Notably, the two watersheds with the highest proportions of nonnative species (83.3% and 82.9%) exhibited the substantial sesLCBD decreases of -3.71 and -3.79, respectively. These findings illuminate how nonnative species reshape freshwater biodiversity by modifying LCBD patterns, offering critical insights for conservation planning. We recommend prioritizing high-LCBD watersheds to maintain ecosystem functionality.

Overuse of antibiotics such as sulfonamide (SA) has led to their excess existence in water environment, which would threaten water ecological security and human health. In this study, the resistance of three plants to SA was systematically studied. The relative growth rate (RGR) of Pistia stratiotes L. remained around 55 % without significant changes when the SA concentration increased from 0 to 30 mg/L, which in Canna indica L. and Eichhornia crassipes has significant decrease, showing the best resistance of Pistia stratiotes L. to SA stress This property will be beneficial for relieving SA toxicity in wastewater treatment. This study identified that aquatic plants promoted the removal of SA through the action of microorganisms rather than absorption and decomposition by the plant itself. Additionally, the presence of SA inhibited the growth of aquatic plants, which resulted in significant increases in peroxidase, catalase, superoxide dismutase activities, and hydrogen peroxide contents in the leaves. The relative abundance of Pedobacter was greater when the SA concentration was high. Pedobacter glucosidilyticus was tolerant to high concentrations of SA. Overall, this study provides insight into ecological antibiotic removal and screening of aquatic plants with SA stress.

In our study, chemical investigation of the marine fungus Penicillium sp. led to the isolation of four isocoumarin derivatives, including two new compounds (1 and 2) and two known analogues (3 and 4). The structures of 1 and 2 were determined by comprehensive analysis of the 1D (1H and 13C NMR spectra) and 2D NMR data (COSY, HSQC, HMBC, and NOESY spectra). The structure of 1 was confirmed by comparing the calculated and experimental 13C NMR data. Compounds 1 and 2 are isocoumarins that lack substitution at the C-5, C-6, and C-7 positions, a structural feature that is uncommon among this class of natural products. The current study enriched the chemical diversity of fungus-derived isocoumarin derivatives.

Zooplankton play pivotal roles in aquatic ecosystems, yet the mechanisms by which species interactions shape their community structure remain poorly understood, particularly in urbanized river networks. Here, we investigated the assembly processes of zooplankton communities across 44 sites in Shanghai’s megacity river network during winter. Using canonical correspondence analysis (CCA) and variance partitioning analysis (VPA), we identified water temperature (WT), Secchi depth (SD), and pH as significant environmental drivers, albeit with limited explanatory power (11.10%). Neutral community model (NCM) analysis revealed that deterministic niche processes dominated community assembly, emphasizing the critical role of biotic interactions. Co-occurrence network analysis further identified 29 keystone species, predominantly generalist rotifers (58.62%), which exhibited broad niche breadth and strong competitive traits (e.g. pollution resistance and omnivory). High modularity (0.55) and interspecific competition (18.67% niche overlap > 0.5) indicated structural instability within the community. These findings highlight the interplay of environmental filtering and species interactions in shaping urban zooplankton communities, offering insights for biodiversity conservation and ecological monitoring in anthropogenically impacted aquatic systems.

Platessa congqiancuoensis sp. nov., a new freshwater diatom from Lake Congqiancuo (Sichuan, China), is described using light and scanning electron microscopy. Diagnostic features include an elliptical-lanceolate valve outline, narrowly linear axial area, and a rhombic to oval central area bordered by 4-5 shortened striae. Striae transition radially from the valve center to convergent apices, with hooked terminal raphe ends deflected in opposite directions. The species is distinguished from morphologically similar taxa (P. mugecuoensis, P. stewartii, P. bahlsii, and P. brevicostata) by valve dimensions, shape, striae density, and ultrastructural details. We further contextualize Platessa within related genera and discuss potential taxonomic linkages.

Dongting Lake is the second largest freshwater lake in China, supports high biodiversity and many endemic or endangered species, such as finless porpoise (Neophocaena phocaenoides), Baer's pochard (Aythya baeri), and east Asian minnow (Ochetobius elongatus), and is thus a global biodiversity hotspot. It is located within an important aquaculture and agricultural region, and many non-native species were introduced into the lake for aquaculture and the ornamental trade. However, information about these non-native species is scarce. We sampled the lake and updated a list of the lake's non-native species, reviewed their status, and threat to biodiversity, as well as their contribution to aquaculture and fisheries. A total of 157 non-native species, including 14 fishes, 136 vascular plants, 1 amphibian, 2 crustacea, 2 mollusca, and 2 reptile species have been imported into Dongting Lake. The main pathways of introduction are through the ornamental trade (97 species, 62%), followed by unintentional introductions (23 species, 15%), aquaculture (13 species, 8%), herbal medicine uses (8 species, 5%), forage grasses (7 species, 4%), food (5 species, 3%), timber (2 species, 1%) and biocontrol and oil (1 species each, 1% respectively). The non-native species origins are North America (43 species, 27%), South America (42 species, 27%), Asia (29 species, 18%), Europe (28 species, 18%), Africa (13 species, 8%), and Oceania (2 species, 1%). Some non-native species, such as red swamp crayfish (Procambarus clarkii), channel catfish (Ictalurus punctatus), and parrot's feather (Myriophyllum aquaticum), are valuable for aquaculture and horticulture. However, other non-native species, such as Alternanthera philoxeroides, Pomacea canaliculate, and Trachemys scripta elegans, pose a potential threat to local biodiversity, human health, and sustainable development. Better management and control of non-native species in Dongting Lake are needed.

Extreme drought events, intensified by climate change, critically threaten aquatic ecosystem stability by restructuring phytoplankton communities. However, the mechanisms underlying drought-driven community assembly remain poorly understood. This study investigated the impacts of extreme drought on phytoplankton community dynamics in the aquatic reserves of Jiujiang City, China, a critical ecotone of the Yangtze River and Poyang Lake. Through multi-temporal sampling (2022–2023) across 12 sites, we integrated taxonomic, functional group, and co-occurrence network analyses with environmental driver assessments. The results revealed that extreme drought significantly reduced phytoplankton species diversity and triggered a functional shift from disturbance-adapted (e.g., MP group) to pollution-tolerant taxa (e.g., W1 group). Deterministic processes dominated community assembly, driven by drought-induced environmental filtering through water temperature, dissolved oxygen, and nutrient fluctuations. Copper emerged as a key stressor, correlating with the abundance of Cryptophyta. Co-occurrence networks, cohesion, and robustness exhibited heightened complexity and stability under extreme drought, emphasizing stress-induced mutualistic interactions. Our findings elucidate how drought reshapes phytoplankton communities via nutrient dynamics and deterministic species interactions, offering critical insights for managing aquatic ecosystems under escalating climatic extremes.

Harmful Raphidiopsis raciborskii blooms threaten aquatic ecosystems via toxin production, hypoxia induction, and biodiversity loss. To elucidate the synergistic regulatory mechanisms of Fe3+ and phosphorus (P) in cyanobacterial growth, we used a sterile pure culture system under laboratory conditions. We set different phosphorus sources (organic phosphorus and inorganic phosphorus) and low phosphorus concentration of R. raciborskii culture medium for culture, and set different Fe3+ addition amount to determine the basic growth index of cyanobacteria cells and the phosphorus content of different components. The results revealed that under conditions of sufficient inorganic phosphorus, there was a logarithmic relationship between ferric ammonium citrate (Fe3+) and the specific growth rate of R. raciborskii. Fe3+ > 2 mg/L enhanced IPS enrichment and biomass accumulation. However, in oligotrophic or mesotrophic environments with low inorganic phosphorus concentrations, the effect of Fe3+ on the growth of R. raciborskii contrasted with that observed in high-IP (eutrophic) environments, exhibiting a pattern of 'low promotion and high inhibition'. Under organic phosphorus conditions, R. raciborskii converted phosphorus by increasing alkaline phosphatase activity (APA), but this metabolic compensation failed to restore physiological functions, resulting in growth suppression and enhanced cellular phosphorus reserves. Our results establish quantitative linkages between Fe3+-P co-limitation thresholds and algal adaptive responses, providing mechanistic insights for controlling bloom dynamics through targeted manipulation of Fe-P bioavailability.

Microorganism-based biocontrol strategies for harmful cyanobacterial blooms have gained increasing attention due to their ecological compatibility and species-specific targeting. Despite this, research on algicidal bacteria effectiveness against the invasive cyanobacterium Raphidiopsis raciborskii remains limited. Research has been conducted on the Bacillus subtilis strain CH21, which was isolated from Chaohu Lake in China. exhibiting potent indirect anticyanobacterial activity against R. raciborskii. Within 48 h of exposure, the cell-free filtrate of strain CH21 achieved 96.2 % removal efficiency of R. raciborskii cells. Physiological and morphological analyses revealed severe disruption of the photosynthetic apparatus (Fv/Fm and Yield values reduced to zero within 16 h), oxidative stress (elevation in malondialdehyde content and reactive oxygen species, reduction in superoxide dismutase and catalase activity), and cellular damage, including pseudovacuole collapse, the degradation of polyphosphate granules and cytoplasmic leakage. Metabolomic profiling identified surfactin-class lipopeptides as putative bioactive agents, which demonstrated exceptional stability across a wide thermal (25-121 °C) and pH (3-13) range. These findings highlight B. subtilis CH21 as a promising candidate for targeted biocontrol of R. raciborskii blooms, supporting the development of environmentally mitigation technologies to be used in cases where it is difficult to control R. raciborskii by external nutrient loading reduction or if the response to such loading reductions are slow.

The escalating salinization of lakes and wetlands is reducing the ecological functions of these ecosystems and undermines the survival and diversity of aquatic macrophytes. Although the application of amendments has been shown to efficiently alleviate the salinization of terrestrial ecosystems, their improvement effects on saline aquatic ecosystems are yet to be fully understood. We conducted mesocosms experiment to investigate the effects of three soil amendment treatments—biochar, desulfurized gypsum, and zeolite powder—on saline sediment and the submerged macrophyte Myriophyllum spicatum. The results showed that all three amendments effectively reduced salinity and pH in both the sediment and water column, thereby alleviating salt stress on M. spicatum, decreased the levels of antioxidant enzymes and significantly enhanced the growth of M. spicatum. The biochar treatment showed the most pronounced improvements, with a 34

Global change stressors, including climate warming, eutrophication, and small-sized omnivorous fish, may exert interactive effects on the food webs and functioning of shallow lakes. Periphyton plays a central role in the primary production and nutrient cycling of shallow lakes but constitutes a complex community composed of eukaryotes and prokaryotes that may exhibit different responses to multiple environmental stressors with implications for the projections of the effects of global change on shallow lakes. We analyzed the effects of warming, nutrient enrichment, small omnivorous fish and their interactions on eukaryotic and prokaryotic periphyton structures in shallow lake mesocosms. We performed 16S and 18S rRNA high-throughput sequencing to elucidate the effect of the abovementioned stressors. We found that warming promoted periphytic alpha diversity and network complexity, with multi-tolerant genera becoming dominating (e.g. Spirosomaceae and Azospirillaceae). Contrastingly, nutrient enrichment led to reduced prokaryotic diversity and network complexity and stability, with weak disruption of the eukaryotic structure. Small omnivorous fish were major drivers of changes eukaryotic periphyton, facilitating diversity and network complexity, and increasing prokaryotic and eukaryotic biomarker diversity. Omnivorous fish reduced the grazing pressure on periphyton mainly through selective grazing on zooplankton, contributing to periphytic structural stability and functional diversity, especially the proliferation of prokaryotic biomarkers. Nutrient enrichment counteracted the positive effects of warming on periphyton, while concerted action with omnivorous fish led to high TN and TP concentrations and accelerated the negative development of periphytic alpha diversity and network structure. The co-occurrence of the three environmental pressures ultimately resulted in a disruption of periphytic biodiversity and community structure and weakened connectivity with the environment. Our study provided new insights into the understanding of the response of prokaryotic and eukaryotic community structure and ecological functions of freshwater periphyton to global environmental change.

Microalgal-bacterial granular sludge (MBGS) efficiently removes conventional contaminants, but its potential for estrogen transformation and detoxification remains unclear, which is a concerning topic for biological wastewater treatment of endocrine-disrupting contaminants. This study comprehensively investigated the fate, transformation, and detoxification of 17α-ethinylestradiol (EE2) in MBGS. Results demonstrated that MBGS showed superior performance to standalone Chlorella vulgaris and aerobic granular sludge, achieving 80.5% EE2 removal and 76.3% estrogenicity reduction. MBGS maintained robust performance and structural stability under various conditions. The primary EE2 removal pathways were biodegradation (58.2%) and photodegradation (30.5%). By leveraging both pathways, MBGS transformed photodegraded transformation products (TPs) into less estrogenic sulfate and glucuronide conjugates, resulting in a TP profile with significantly reduced endocrine, bioaccumulation, and developmental toxicity potentials. Therefore, MBGS represents a robust and sustainable solution for treating estrogenic wastewater, leveraging bacterial-algal synergy to eliminate both parent compound and the ecological risks from its TPs.

Sediment properties have a crucial effect on the growth and recovery of aquatic plants in lakes. Addition of various chemical substances has been proposed to reinforce the recovery of plants after a nutrient loading reduction. However, the effects of such sediment amendments on plant growth, especially those from rhizosphere microorganisms, is limited. We added Kaolin clay to sediments in different concentrations to explore its impact on the growth of Vallisneria natans and Ottelia acuminate and the concurrent shift in rhizosphere microorganisms using high-throughput sequencing technology. We found that the addition of low doses (10 % and 20 % in mass ratio) of Kaolin significantly modified sediment conditions (oxidation reduction potential and pH), with implications also for the composition, diversity, and stability of rhizosphere microorganisms. LEfSe analysis revealed that low-dose addition of Kaolin increased the abundances of functional microbial groups that benefit plant nutrient absorption and enhance plant stress resistance, such as Spirillaceae, Rhodocyclaceae, and Burkholderiales. Moreover, low doses of Kaolin significantly promoted the photosynthesis and nutrient absorption of submerged macrophytes, thereby facilitating plant growth. A structural equation model (SEM) indicated that the direct impact of Kaolin on the growth of submerged plants was relatively minor, while the indirect effect through modulation of rhizosphere microorganisms was important. Our study suggests that low doses of Kaolin may be used to promote the growth of submerged macrophytes when lakes with a high organic content in the sediment are recovering after nutrient loading reduction.

Harmful Raphidiopsis raciborskii blooms threaten aquatic ecosystems via toxin production, hypoxia induction, and biodiversity loss. To elucidate the synergistic regulatory mechanisms of Fe3+ and phosphorus (P) in cyanobacterial growth, we used a sterile pure culture system under laboratory conditions. We set different phosphorus sources (organic phosphorus and inorganic phosphorus) and low phosphorus concentration of R. raciborskii culture medium for culture, and set different Fe3+ addition amount to determine the basic growth index of cyanobacteria cells and the phosphorus content of different components. The results revealed that under conditions of sufficient inorganic phosphorus, there was a logarithmic relationship between ferric ammonium citrate (Fe3+) and the specific growth rate of R. raciborskii. Fe3+ > 2 mg/L enhanced IPS enrichment and biomass accumulation. However, in oligotrophic or mesotrophic environments with low inorganic phosphorus concentrations, the effect of Fe3+ on the growth of R. raciborskii contrasted with that observed in high-IP (eutrophic) environments, exhibiting a pattern of ‘low promotion and high inhibition’. Under organic phosphorus conditions, R. raciborskii converted phosphorus by increasing alkaline phosphatase activity (APA), but this metabolic compensation failed to restore physiological functions, resulting in growth suppression and enhanced cellular phosphorus reserves. Our results establish quantitative linkages between Fe3+-P co-limitation thresholds and algal adaptive responses, providing mechanistic insights for controlling bloom dynamics through targeted manipulation of Fe-P bioavailability.

In this study, we describe a new diatom, Navicula congqiancuoensis sp. nov., which was found in epilithon samples collected from a small mountain lake, at Lake Congqiancuo, Sichuan Province, China. A detailed morphological description of the new species is provided based on light and scanning electron micrographs. Navicula congqiancuoensis sp. nov. valve is linear to linear-lanceolate, with a slight elevation in the center and broadly rounded at both apices. The striae are radiate and convergent at the apices. The axial area is narrow and linear, and the central area is small and elliptical in the middle. This new species is compared with similar species, such as Navicula angusta, N. leptostriata, N. piercei, N. heimansioides which differ in size, valve shape, striae density and ultrastructure.