The use of human and veterinary drugs has led to the accumulation of pharmaceuticals in various aquatic environments at progressively increasing levels, exhibiting strong ecological risks. Metformin is widely used as a first-line prescription drug for the treatment of type 2 diabetes mellitus as well as a livestock drug. Unlike other drugs, metformin is not metabolized in the body, and almost all of its intake is excreted and released into the aquatic environment via urine and feces, causing adverse effects on aquatic ecosystems. This review provides an overview of the occurrence and detection of metformin in the aquatic environment and its toxic effects on different aquatic organisms (fish, daphnia, rotifers, chlorella). Metformin has been documented in a variety of aqueous environments such as wastewater, surface water, and groundwater as well as drinking water. The wide distribution of metformin in the aqueous environment calls for the development of more accurate detection methods. This paper reviews detection methods for metformin in the aqueous environment and evaluates their advantages and disadvantages. Toxicity studies have shown that metformin can cause adverse reactions in fish, such as oxidative stress, genotoxicity, disruption of intestinal flora, and morphological alterations; it also affects the growth and reproduction of small aquatic organisms. Knowledge gaps in the field of metformin research were assessed, and future research priorities were identified.

Tourism development influenced the ecological network of microbial communities. ● Regulating mechanism of intra- and inter-domain networks was clarified. ● Macrophyte coverage reduces microbial network complexity and stability. ● Landscaping may promote nitrogen and phosphorus cycle in wetland watershed. Numerous urban wetland parks have been established, yet the understanding of microbial interactions in response to tourism development is still limited. This study aims to elucidate the impact of tourism development on the complexity and stability of molecular ecological networks within the microbial communities of wetland sediments. Through an analysis of sediments properties, microorganism intra- and inter-domain co-occurrence characteristics in three different wetland functional areas (conservation, landscaping, and recreation areas), we found that tourism development influenced sediment physicochemical properties. These changes regulated the diversity and ecological networks of archaeal and bacterial communities. Specifically, areas with landscaping (LA) exhibited reduced network connectivity and robustness, suggesting that macrophyte coverage diminishes the complexity and stability of microbial communities in wetland parks. Notably, the transition from conservation areas (CA) to LA strengthened the correlations between microbial network modules and sediment total nitrogen (TN) and total phosphorus (TP), potentially enhancing the nitrogenand phosphorus cycles in wetlands. Structural equation modeling analysisrevealed that both abiotic factors (TC, TP, TN, K, Mg, pH) and biotic factors (archaeal and bacterial α-diversity) can influence interdomain network complexity, accounting for 42% of the variation. Among these factors, sediment TN exerted the largest positive effect on network complexity (37.9%), while Mg had the most negative impact (59.8%). This study provides valuable insights for ecological assessments of urban wetlands and can inform strategies for effective wetland ecosystem management.

Microorganisms are integral to freshwater ecological functions and, reciprocally, their activity and diversity are shaped by the ecosystem state. Yet, the diversity of bacterial community and its driving factors at a large scale remain elusive. To bridge this knowledge gap, we delved into an analysis of 16S RNA gene sequences extracted from 929 water samples across China. Our analyses revealed that inland water bacterial communities showed a weak latitudinal diversity gradient. We found 530 bacterial genera with high relative abundance of hgcI clade. Among them, 29 core bacterial genera were identified, that is strongly linked to mean annual temperature and nutrient loadings. We also detected a non-linear response of bacterial network complexity to the increasing of human pressure. Mantel analysis suggested that MAT, HPI and P loading were the major factors driving bacterial communities in inland waters. The map of taxa abundance showed that the abundant CL500-29 marine group in eastern and southern China indicated high eutrophication risk. Our findings enhance our understanding of the diversity and large-scale biogeographic pattern of bacterial communities of inland waters and have important implications for microbial ecology.

Human activities have long impacted the health of Earth's rivers and lakes. These inland waters, crucial for our survival and productivity, have suffered from contamination which allows the formation and spread of antibiotic-resistant genes (ARGs) and consequently, ARG-carrying pathogens (APs). Yet, our global understanding of waterborne pathogen antibiotic resistance remains in its infancy. To shed light on this, our study examined 1240 metagenomic samples from both open and closed inland waters. We identified 22 types of ARGs, 19 types of mobile genetic elements (MGEs), and 14 types of virulence factors (VFs). Our findings showed that open waters have a higher average abundance and richness of ARGs, MGEs, and VFs, with more robust co-occurrence network compared to closed waters. Out of the samples studied, 321 APs were detected, representing a 43 % detection rate. Of these, the resistance gene 'bacA' was the most predominant. Notably, AP hotspots were identified in regions including East Asia, India, Western Europe, the eastern United States, and Brazil. Our research underscores how human activities profoundly influence the diversity and spread of resistome. It also emphasizes that both abiotic and biotic factors play pivotal roles in the emergence of ARG-carrying pathogens.

Cyanobacterial blooms have emerged as a significant environmental issue worldwide in recent decades. However, the toxic effects of microcystin-LR (MC-LR) on aquatic organisms, such as frogs, have remained poorly understood. In this study, frogs (Pelophylax nigromaculatus) were exposed to environmentally relevant concentrations of MC-LR (0, 1, and 10 μg/L) for 21 days. Subsequently, we assessed the impact of MC-LR on the histomorphology of the frogs' livers and conducted a global MS-based nontarget metabolomics analysis, followed by the determination of substances involved in lipid metabolism. Results showed that MC-LR significantly induced histological alterations in the frogs' hepatopancreas. Over 200 differentially expressed metabolites were identified, primarily enriched in lipid metabolism. Biochemical analysis further confirmed that MC-LR exposure led to a disorder in lipid metabolism in the frogs. This study laid the groundwork for a mechanistic understanding of MC-LR toxicity in frogs and potentially other aquatic organisms.

Tetrabromobisphenol A (TBBPA) has become a topic of public attention due to its pervasive detection in the environment and organisms in recent decades. However, limited information is available regarding the toxicity of TBBPA on reproductive ability of male mammals. Herein, the reproductive toxicity of TBBPA was investigated in male rats to fill the knowledge gap. In this study, male rats were exposed to TBBPA (0, 10, 100, and 1000mg/kg) for 6 weeks. Subsequently, body and organ indexes, histopathological evaluation of testis and epididymis, ultrastructural observation of sperm, testosterone and progesterone levels, and oxidative stress indicators were conducted to reveal corresponding mechanisms. Results obtained showed that compare to the control group, the body weight, testes weight, epididymis weight, seminal vesicle and coagulation glands weight of rats in the 1000mg/kg group lost 8.30%, 16.84%, 20.16%, 19.72% and 26.42%, respectively. Intriguingly, exposure to TBBPA (10, 100, 100mg/kg) resulted in substantial pathological damage in testis, epididymis and sperm. TBBPA exposure also increased malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents, as well as superoxide dismutase (T-SOD) and catalase (CAT) activities in testicular tissue. What’s more, the testosterone and progesterone levels in male rat serum were significantly decreased after exposure to TBBPA for 6 weeks. Meanwhile, results of molecular docking showed that TBBPA has a strong affinity with estrogen receptors (ERs). These findings demonstrated that TBBPA exposure negatively impacts the reproductive ability of male rats, thus providing new insights for risk assessment for reproductive health under TBBPA exposure.

Antibiotic overuse and the subsequent environmental contamination of residual antibiotics poses a public health crisis via an acceleration in the spread of antibiotic resistance genes (ARGs) through horizontal gene transfer. Although the occurrence, distribution, and driving factors of ARGs in soils have been widely investigated, little is known about the antibiotic resistance of soilborne pathogens at a global scale. To explore this gap, contigs from 1643 globally sourced metagnomes are assembled, yielding 407 ARG-carrying pathogens (APs) with at least one ARG; APs are detected in 1443 samples (sample detection rate of 87.8%). The richness of APs is greater in agricultural soils (with a median of 20) than in non-agricultural ecosystems. Agricultural soils possess a high prevalence of clinical APs affiliated with Escherichia, Enterobacter, Streptococcus, and Enterococcus. The APs detected in agricultural soils tend to coexist with multidrug resistance genes and bacA. A global map of soil AP richness is generated, where anthropogenic and climatic factors explained AP hot spots in East Asia, South Asia, and the eastern United States. The results herein advance this understanding of the global distribution of soil APs and determine regions prioritized to control soilborne APs worldwide.

Plastic production on a global scale is instrumental in advancing modern society. However, plastic can be broken down by mechanical and chemical forces of humans and nature, and knowledge of the fate and effects of plastic, especially nanoplastics, in the aquatic environment remains poor. We provide an overview of current knowledge on the environmental occurrence and toxicity of nanoplastics, and suggestions for future research. There are nanoplastics present in seas, rivers, and nature reserves from Asia, Europe, Antarctica, and the Arctic Ocean at levels of 0.3-488 microgram per liter. Once in the aquatic environment, nanoplastics accumulate in plankton, nekton, benthos through ingestion and adherence, with multiple toxic results including inhibited growth, reproductive abnormalities, oxidative stress, and immune system dysfunction. Further investigations should focus on chemical analysis methods for nanoplastics, effect and mechanism of nanoplastics at environmental relevant concentrations in aquatic organisms, as well as the mechanism of the Trojan horse effect of nanoplastics.

Freshwater microorganisms and their interactions are important drivers of nutrient cycling that are in turn affected by nutrient status, causing shifts in microbial community diversity, composition, and interactions. However, the impact of water trophic status on bacterial-archaeal interdomain interactions remains poorly understood. This study focused on the impact of trophic status, as characterized by trophic state index (TSI), on the interdomain interactions of freshwater microbial communities from 45 ponds in Hangzhou. Our results showed that the mesotrophic wetland bordering on lightly eutrophic (Hemu: TSI of 49; lightly eutrophic is defined as 50 ≤ TSI <60) harbored a much more complex bacterial-archaeal interdomain network, which showed significantly (P < 0.05) higher connectivity than the wetlands with lower (TSI of 38) or higher (TSI of 57) trophic levels. Notably, light eutrophication strengthened the network modules’ negative associations with organic carbon through some network hubs, which could trigger carbon loss in wetlands. We also detected a non-linear response of interdomain network complexity to the increasing of nutrients with a turning point of approximately TSI 50. Quantitative estimates of community assembly processes and structural equation modelling analysis indicated that chlorophyll-a, total nitrogen, and total phosphorus could regulate interdomain network complexity (50% of the variation explanation rate) by driving microbial community assembly. This study demonstrates that microbial interdomain network complexity could be used as a bioindicator for ecological changes, which would helpful for improving ecological assessment of the freshwater eutrophication.

Small ponds have become a hotspot of greenhouse gas emissions, but our understanding of methane (CH4) cycling and its biological regulation in small polluted ponds remains limited. To assess how pollution affects CH4 content, we investigated dissolved CH4 concentrations, water and sediments properties, methanogenic and methanotrophic communities in two types of small polluted ponds. Compared with low pollution (LP) ponds, high pollution (HP) ponds showed significantly (P < 0.05) higher dissolved CH4 in water. Sequencing of methyl coenzyme M reductase (mcrA) and particulate methane monooxygenase (pmoA) genes showed that HP led to significant (P < 0.05) shifts of CH4-cycling microbial communities, with increased Shannon index of sediment methanogenic communities and water methanotrophic communities. There were also strong negative associations (P < 0.05) between dissolved CH4 concentrations and interdomain methanogen-methanotroph network connectivity in water and sediments, respectively. The partial least squares path modeling indicated that dissolved oxygen, total organic carbon, ammonium nitrogen and nitrate nitrogen of water, and total nitrogen and total carbon of sediment, and CH4-cycling microbes could regulate the CH4 content. This study clarified the effects of environmental deterioration on CH4 cycling in small ponds, highlighting the use of methanogen-methanotroph network connectivity to assess the CH4 production.

Summary Microbial sulfate reduction and sulfur oxidation are vital processes to enhance organic matter degradation in sediments. However, the diversity and composition of sulfate‐reducing bacteria (SRB) and sulfur‐oxidizing bacteria (SOB) and their environmental driving factors are still poorly understood in aquaculture ponds, which received mounting of organic matter. In this study, bacterial communities, SRB and SOB from sediments of aquaculture ponds with different sizes of grass carp (Ctenopharyngodon idellus) were analysed using high‐throughput sequencing and quantitative real‐time PCR (qPCR). The results indicated that microbial communities in aquaculture pond sediments of large juvenile fish showed the highest richness and abundance of SRB and SOB, potentially further enhancing microbial sulfur cycling. Specifically, SRB were dominated by Desulfobulbus and Desulfovibrio, whereas SOB were dominated by Dechloromonas and Leptothrix. Although large juvenile fish ponds had relatively lower concentrations of sulfur compounds (i.e. total sulfur, acid‐volatile sulfide and elemental sulfur) than those of larval fish ponds, more abundant SRB and SOB were found in the large juvenile fish ponds. Further redundancy analysis (RDA) and linear regression indicated that sulfur compounds and sediment suspension are the major environmental factors shaping the abundance and community structure of SRB and SOB in aquaculture pond sediments. Findings of this study expand our current understanding of microbial driving sulfur cycling in aquaculture ecosystems and also provide novel insights for ecological and green aquaculture managements.

Protists in aquaculture ponds are key components associated with primary productivity, nutrient cycling, and fish healthy. However, the protist metacommunity diversity, as well as the ecological and environmental factors that structure protist metacommunity in aquaculture ponds remain poorly understood. This study examined protist metacommunities in water and sediment of larval, small juvenile and large juvenile grass carp ponds. The results indicated sediment resuspension became stronger with the increased fish size, which led to high levels of total suspended solids and nitrogen but low levels of phosphate, chlorophyll a and transparency in water. Moreover, sediment resuspension subsequently increased the alpha diversity indexes (i.e., OTU number, Shannon index and Simpson index) of protist communities in water and sediment. Meanwhile, sediment resuspension increased the relative abundance of heterotrophic Ciliophora and Cercozoa, but decreased the relative abundance of autotrophic Chlorophyta, Stramenopiles X, and Ochrophyta. Besides, some mixotrophic and heterotrophic protists showed competitive advantages in the turbidity water, which led to the increase of negative interactions in the protist co-occurrence networks. Based on the null model, sediment resuspension strengthened homogeneous selection (deterministic process) and weakened dispersal limitation (stochastic process) processes of protist community assembly. Indeed, protist community dissimilarity within each local community and each habitat (water or sediment) both decreased while the community dissimilarity between habitats increased with the increase of fish size. Therefore, sediment resuspension did not enhance the dispersal path between water and sediment, but decreased the dispersal limitation within sediment and water coupled with the strengthening of environmental selection. These results indicated that grass carp could restructure the protist metacommunity in aquaculture ponds through bottom up way of sediment resuspension. This study advances our understanding of the relationship between fish and protist metacommunity assembly in aquaculture systems.

The human activity introduces strong environmental stresses, and results in great spatiotemporal heterogeneity for the environment. Although the effects of environmental factors on the microbial diversity and succession have been widely studied, knowledge about how keystone taxa respond to environmental stresses remains poorly understood. We examined bacterial and archaeal communities from 45 wetland ponds covering a wide range of waters in Hangzhou. We found that shifts in bacterial and archaeal communities were strongly correlated with water pollution as indicated by the comprehensive water quality identification (CWQI). The SEGMENTED analysis suggested that there were non-linear responses of microbial communities and keystone taxa to the water pollution gradient. Moreover, these significant tipping points (e.g., CWQI > 4.0) would afford a warning line for urban wetland management. Notably, keystone taxa of bacterial communities could be used to successfully (~88.9% accuracy) predict water contamination levels. This study provides new insights into the potential for keystone bacterial taxa to predict water contamination.

A large number of urban wetland parks have been established, but knowledge about the effects of tourism development on the microbial diversity and ecosystem functioning remains limited. This study aimed to clarify the responses of bacterial communities to tourism development targeted the Xixi National Wetland Park, China. By analyzing the diversity, composition, assembly pattern, and environmental drivers of bacterial communities, we found that tourism development considerably affected the water quality, which further decreased the α-diversity but increased the β-diversity in open areas for landscaping and recreation. Specifically, there was higher Simpson dissimilarity across functional wetland areas, indicating that species replacement mainly explained β-diversity patterns of bacterial communities. RDA analysis and ecological processes quantification further suggested that TOC and TC were the major factors in the open areas driving bacterial communities in water and sediment, respectively. Also, typical anti-disturbance taxa (Gammaproteobacteria) and potential pathogens (Bacillus) were enriched in the wetlands under more anthropogenic disturbances. Findings of the present study highlighted the effects of tourism development on bacterial communities resulted in obvious spatial variation in the Xixi National Wetland Park. This study gives us useful information for ecological assessments of urban wetlands, and further can provide references in making appropriate strategies to manage wetland ecosystems.

随着有机氟化物在各领域的广泛应用,含氟有机废水处理面临巨大挑战。活性污泥作为有机废水处理的核心技术之一,微生物在其中发挥着极其重要的作用。本综述首先聚焦在活性污泥微生物群落多样性、组成、结构和功能及其与含氟废水类型、处理工艺和处理效率之间的关系,进而讨论了功能微生物降解/转化有机氟化物的途径和作用机制,最后展望了结合分离培养降解有机氟化物的关键微生物,以及微生物组学技术解析活性污泥微生物群落构建、互作、代谢等核心问题,以提高对含氟有机废水微生物降解机理的认识,优化含氟有机废水处理工艺。

Algal blooms not only damage the ecological structure of water bodies,but also produce algal toxins which can be divided into liver toxin (represented by microcystin-LR) and neuro-toxin (represented by anatoxin-a) according to the chemical structure and toxic mechanism.This paper summarizes two kinds of toxins,i.e.anatoxin-a (ANTX-a) and microcystin-LR (MC-LR),in terms of the production,distribution and structure,and from the perspective of immunology illustrates the toxic effects and toxic mechanisms of two toxins on the aquatic organisms.

Due to the high toxicity,high organic loading,poor biodegradability and complicated components of fluorine chemical wastewater,it is a key issue to treat fluorine containing wastewater by the functional microbe.In this study,three kinds of activated sludge named S1,S2 and S3 were used to study the toxicity-tolerance abilities and microbial community characteristics.Both S1 and S2 were collected from the fluorine chemical industrial wastewater treatment units,while S3 was collected from a domestic wastewater treatment unit.Respiration rates of activated sludge were measured by means of a Strathtox Respirometer.The results show that the optimal respiration rates of sludge S1,S2,S3 in glucose wastewater were (174.00±1.14),(189.20± 1.11) and (134.50±2.30) mg· L-1· h-1,respectively.In fluorine chemical wastewater,their optimal respiration rates were only (5.60±0.70),(8.87±0.97) and (5.83±0.25) mg· L-1· h-1,respectively.It was clearly indicated that there were harmful substances in wastewater that were toxic to activated sludge.Furthermore,by the solid-phase-extraction (SPE) purification method,mixed organic fluorine chemical wastewater was made.It was found that the optimal respiration rates of sludge in such kind of wastewater were (53.02±0.79),(68.60±0.96) and (38.10±1.06) mg· L-1· h-1,respectively.It was implied that the microbes in all the sludge had the adaptabilities for the purified organic fluorine chemical wastewater.The PCR-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) analyses illustrated that the microbe diversities of all these sludge were significant and the Shannon-Brown index of S1 was even 1.69.By cloning and sequencing analyses,6 kinds of dominant functional microorganisms such as Kineococcus gynurae were identified.It was found that they can adapt the fluoride chemicals containing organic wastewater.The verification experimental results further proved that the total organic carbon (TOC) degradation rate by sludge S2 was above 70％ for the fluorine chemical organic wastewater with the initial TOC content of 250 mg·L-1.It was demonstrated that after the desalination and the elimination of heavy metals the biodegradability of the fluoride chemical raw wastewater can be greatly enhanced.All the results can provide the theoretical basis of the technique development for the treatment of the fluoride chemical wastewater.