Interference of microplastics on autotrophic microbiome in paddy soils: Shifts in carbon fixation rate, structure, abundance, co-occurrence, and assembly process.

Autotrophic microorganisms play a crucial role in soil CO2 assimilation. Although microplastic pollution is recognized as a significant global concern, its precise impact on carbon sequestration by autotrophic microorganisms in agroecosystem soil remains poorly understood. This study conducted microcosm experiments to explore how conventional polystyrene (PS) and biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) microplastics affect carbon fixation rates (CFRs) and the community characteristics of soil autotrophic microorganisms in paddy agroecosystems. The results showed that compared with the control groups, 0.5 % and 1 % microplastic treatments significantly reduced soil CFRs by 11.8 - 24.5 % and 18.7 - 32.3 %, respectively. PS microplastics exerted a stronger inhibition effect on CFRs than PHBV microplastics in bulk soil. However, no significant difference was observed in the inhibition of CFRs by both types of microplastics in rhizosphere soils. Additionally, PS and PHBV microplastics altered the structure of autotrophic microbial communities, resulting in more stochastically dominated assembly and looser, more fragile coexistence networks compared to control groups. Moreover, microplastics drove the changes in autotrophic microbial carbon fixation primarily through their direct interference and the indirect effect by increasing soil organic carbon levels. Our findings enhance the understanding and predictive capabilities regarding the impacts of microplastic pollution on carbon sinks in agricultural soils.

The "Microplastome" - A Holistic Perspective to Capture the Real-World Ecology of Microplastics.

Microplastic pollution, an emerging pollution issue, has become a significant environmental concern globally due to its ubiquitous, persistent, complex, toxic, and ever-increasing nature. As a multifaceted and diverse suite of small plastic particles with different physicochemical properties and associated matters such as absorbed chemicals and microbes, future research on microplastics will need to comprehensively consider their multidimensional attributes. Here, we introduce a novel, conceptual framework of the "microplastome", defined as the entirety of various plastic particles (<5 mm), and their associated matters such as chemicals and microbes, found within a sample and its overall environmental and toxicological impacts. As a novel concept, this paper aims to emphasize and call for a collective quantification and characterization of microplastics and for a more holistic understanding regarding the differences, connections, and effects of microplastics in different biotic and abiotic ecosystem compartments. Deriving from this lens, we present our insights and prospective trajectories for characterization, risk assessment, and source apportionment of microplastics. We hope this new paradigm can guide and propel microplastic research toward a more holistic era and contribute to an informed strategy for combating this globally important environmental pollution issue.

Homogenization of bacterial plastisphere community in soil: a continental-scale microcosm study.

Microplastics alter niches of soil microbiota by providing trillions of artificial microhabitats, termed the "plastisphere." Because of the ever-increasing accumulation of microplastics in ecosystems, it is urgent to understand the ecology of microbes associated with the plastisphere. Here, we present a continental-scale study of the bacterial plastisphere on polyethylene microplastics compared with adjacent soil communities across 99 sites collected from across China through microcosm experiments. In comparison with the soil bacterial communities, we found that plastispheres had a greater proportion of Actinomycetota and Bacillota, but lower proportions of Pseudomonadota, Acidobacteriota, Gemmatimonadota, and Bacteroidota. The spatial dispersion and the dissimilarity among plastisphere communities were less variable than those among the soil bacterial communities, suggesting highly homogenized bacterial communities on microplastics. The relative importance of homogeneous selection in plastispheres was greater than that in soil samples, possibly because of the more uniform properties of polyethylene microplastics compared with the surrounding soil. Importantly, we found that the degree to which plastisphere and soil bacterial communities differed was negatively correlated with the soil pH and carbon content and positively related to the mean annual temperature of sampling sites. Our work provides a more comprehensive continental-scale perspective on the microbial communities that form in the plastisphere and highlights the potential impacts of microplastics on the maintenance of microbial biodiversity and ecosystem functioning.

Ecology and risks of the global plastisphere as a newly expanding microbial habitat.

Plastic offers a new niche for microorganisms, the plastisphere. The ever-increasing emission of plastic waste makes it critical to understand the microbial ecology of the plastisphere and associated effects. Here, we present a global fingerprint of the plastisphere, analyzing samples collected from freshwater, seawater, and terrestrial ecosystems. The plastisphere assembles a distinct microbial community that has a clearly higher heterogeneity and a more deterministically dominated assembly compared to natural habitats. New coexistence patterns-loose and fragile networks with mostly specialist linkages among microorganisms that are rarely found in natural habitats-are seen in the plastisphere. Plastisphere microbiomes generally have a great potential to metabolize organic compounds, which could accelerate carbon turnover. Microorganisms involved in the nitrogen cycle are also altered in the plastisphere, especially in freshwater plastispheres, where a high abundance of denitrifiers may increase the release of nitrite (aquatic toxicant) and nitrous oxide (greenhouse gas). Enrichment of animal, plant, and human pathogens means that the plastisphere could become an increasingly mobile reservoir of harmful microorganisms. Our findings highlight that if the trajectory of plastic emissions is not reversed, the expanding plastisphere could pose critical planetary health challenges.

Different bacterial and fungal community patterns in restored habitats in coal-mining subsidence areas.

Soil microbiota, which plays a fundamental role in ecosystem functioning, is sensitive to environmental changes. Studying soil microbial ecological patterns can help to understand the consequences of environmental disturbances on soil microbiota and hence ecosystem services. The different habitats with critical environmental gradients generated through the restoration of coal-mining subsidence areas provide an ideal area to explore the response of soil microbiota to environmental changes. Here, based on high-throughput sequencing, we revealed the patterns of soil bacterial and fungal communities in habitats with different land-use types (wetland, farmland, and grassland) and with different restored times which were generated during the ecological restoration of a typical coal-mining subsidence area in Jining City, China. The α-diversity of bacterial was higher in wetland than in farmland and grassland, while that of fungi had no discrepancy among the three habitats. The ß-diversity of bacterial community in the grassland was lower than in the farmland, and fungal community was significant different in all three habitats, showing wetland, grassland, and farmland from high to low. The ß-diversity of the bacterial community decreased with restoration time while that of the fungal community had no significant change in the longer-restoration-time area. Furthermore, soil electrical conductivity was the most important driver for both bacterial and fungal communities. Based on the taxonomic difference among different habitats, we identified a group of biomarkers for each habitat. The study contributes to understand the microbial patterns during the ecological restoration of coal-mining subsidence areas, which has implications for the efficient ecological restoration of subsidence areas.

Effects of plants and soil microorganisms on organic carbon and the relationship between carbon and nitrogen in constructed wetlands.

Constructed wetland is an ideal place for studying the effects of plants and microorganisms on the nutrient cycling and carbon-nitrogen coupling in wetland for their clear background. This study examined both bare plots and others with plants (Phragmites australis or Typha angustifolia) in constructed wetlands and vegetation and soil samples were collected to investigate the effects of plants and soil microorganisms on carbon and nitrogen content. Results showed that the soil organic carbon content was high in plots with high plant biomass, and the increase of soil organic carbon driven by plant biomass was mainly from light fraction organic carbon (LFOC). Correlation analysis and redundancy analysis (RDA) suggested that plants play an important role in the cycle of carbon and nitrogen elements in constructed wetland soils, and that plant nitrogen components were key factors influencing wetland soil carbon and nitrogen. In addition, this study found that most of the main microbial taxa were significantly correlated with dissolved organic carbon (DOC), ammonium nitrogen (NH4+), and nitrate and nitrite nitrogen (NOx-) indicating that microorganisms might play an important role in regulating soil element cycles in constructed wetlands by affecting the metabolism of activated carbon and reactive nitrogen. This study has implications for increasing the carbon sink of constructed wetlands to mitigate the effects of global warming.

Habitats generated by the restoration of coal mining subsidence land differentially alter the content and composition of soil organic carbon.

The content and composition of soil organic carbon (SOC) can characterize soil carbon storage capacity, which varies significantly between habitats. Ecological restoration in coal mining subsidence land forms a variety of habitats, which are ideal to study the effects of habitats on SOC storage capacity. Based on the analysis of the content and composition of SOC in three habitats (farmland, wetland and lakeside grassland) generated by different restoration time of the farmland which was destroyed by coal mining subsidence, we found that farmland had the highest SOC storage capacity among the three habitats. Both dissolved organic carbon (DOC) and heavy fraction organic carbon (HFOC) exhibited higher concentrations in the farmland (20.29 mg/kg, 6.96 mg/g) than in the wetland (19.62 mg/kg, 2.47 mg/g) or lakeside grassland (5.68 mg/kg, 2.31 mg/g), and the concentrations increased significantly over time, owing to the higher content of nitrogen in the farmland. The wetland and lakeside grassland needed more time than the farmland to recover the SOC storage capacity. The findings illustrate that the SOC storage capacity of farmland destroyed by coal mining subsidence could be restored through ecological restoration and indicate that the recovery rate depends on the reconstructed habitat types, among which farmland shows great advantages mainly due to the nitrogen addition.

Foliar dust as a reliable environmental monitor of heavy metal pollution in comparison to plant leaves and soil in urban areas.

Pollution of atmospheric particulate matter carrying heavy metals has posed a great threat to various ecosystem compartments. Here, a total of 540 samples from four ecosystem compartments (plant leaves, foliar dust, surface soil, and subsoil) were collected in urban soil-plant systems to characterize the heavy metal concentration and composition of foliar dust, to verify the suitability of foliar dust as an environmental monitor, and to explore the importance of foliar dust in shaping the heavy metal composition in plant leaves. We found that the concentrations of all detected elements (lead, zinc, copper, chromium, nickel, and manganese) in foliar dust were the highest among the four ecosystem compartments. The mass of element per unit leaf area, considering both the dust retention amount and the heavy metal concentration of foliar dust, had significant positive correlations with the degree of heavy metal pollution in soil. Foliar dust could reflect ambient elemental composition most reliably among the four ecosystem compartments. The above findings show that foliar dust is more suitable for environmental monitoring than soil and plant materials in urban areas. In addition, the elemental composition of plant leaves differed significantly with different soil-plant systems although species identity dominated the leaf elemental composition. The variation partitioning model and the partial correlation analysis confirm that foliar dust plays a more important role in shaping the elemental composition of plant leaves than soil. This study provides a new way for environmental pollution monitoring and contributes to a comprehensive understanding of atmospheric particulate matter.

Warming, temperature fluctuations and thermal evolution change the effects of microplastics at an environmentally relevant concentration.

Microplastics are sometimes considered not harmful at environmentally relevant concentrations. Yet, such studies were conducted under standard thermal conditions and thereby ignored the impacts of higher mean temperatures (MT), and especially daily temperature fluctuations (DTF) under global warming. Moreover, an evolutionary perspective may further benefit the future risk assessment of microplastics under global warming. Here, we investigated the effects of two generations of exposure to an environmentally relevant concentration of polystyrene microplastics (5 µg L-1) under six thermal conditions (2 MT × 3 DTF) on the life history, physiology, and behaviour of Daphnia magna. To assess the impact of thermal evolution we thereby compared Daphnia populations from high and low latitudes. At the standard ecotoxic thermal conditions (constant 20 °C) microplastics almost had no effect except for a slight reduction of the heartbeat rate. Yet, at the challenging thermal conditions (higher MT and/or DTF), microplastics affected each tested variable and caused an earlier maturation, a higher fecundity and intrinsic growth rate, a decreased heartbeat rate, and an increased swimming speed. These effects may be partly explained by hormesis and/or an adaptive response to stress in Daphnia. Moreover, exposure to microplastics at the higher mean temperature increased the fecundity and intrinsic growth rate of cold-adapted high-latitude Daphnia, but not of the warm-adapted low-latitude Daphnia, suggesting that thermal evolution in high-latitude Daphnia may buffer the effects of microplastics under future warming. Our results highlight the critical importance of DTF and thermal evolution for a more realistic risk assessment of microplastics under global warming.

Spatio-temporal analysis of the coupling relationship between urbanization and eco-environment in backward regions of China.

The strategy of the Silk Road Economic Belt in China has promoted the urban development of the backward regions in the west, but it might also cause serious eco-environmental concerns. Studying the coupling relationship between urbanization and the eco-environment (UEE) is essential to promote the sustainable development in backward regions. This study developed a combined method of coupling coordination degree (CCD) model, linear regression, and gray relational analysis (GRA) model to investigate the spatio-temporal coupling relationship and the influencing factors between UEE in Ningxia Hui Autonomous Region (NHAR), a typical backward region along the Silk Road Economic Belt. Results show that (1) the economic urbanization and eco-environmental pressure made the largest contribution to the system of urbanization and eco-environment, respectively. (2) The overall CCD in NHAR showed a linear upward trend from 2001 to 2018, while the CCD of each district presented significant spatial difference. The CCDs in the more developed northern regions were generally higher than those in southern mountainous regions. (3) Furthermore, population factors were the main mechanism imposing stress on the eco-environment, and the factors of eco-environmental status had higher restrictive effect on urban development in NHAR. This study could provide theoretical basis for investigating the interaction between UEE in backward regions, which might enable policymakers to formulate targeted sustainable development plans.

The ecology of the plastisphere: Microbial composition, function, assembly, and network in the freshwater and seawater ecosystems.

Microplastics provide a unique habitat for microorganisms, forming the plastisphere. Yet the ecology of the plastisphere, including the microbial composition, functions, assembly processes, and interaction networks, needs to be understood. Here, we collected microplastics and their surrounding water samples in freshwater and seawater ecosystems. The bacterial and fungal communities of the plastisphere and the aquatic environment were studied based on 16S and internal transcribed spacer (ITS) high-throughput sequencing. We found that the plastisphere had a distinct microbial community and recruited a noteworthy proportion of unique species compared to the aquatic environment community, potentially altering ecosystem microbial community and causing microbial invasion. Using a random-forest machine-learning model, we identified a group of biomarkers that could best distinguish the plastisphere from the aquatic environment. Significant differences exist in microbial functions between the plastisphere and the aquatic environment, including functions of pathogenicity, compound degradation, as well as functions related to the cycling of carbon, nitrogen, and sulfur. And these functional differences were expressed differently in freshwater and seawater ecosystems. The oxidation-reduction potential, salinity, the concentrations of nitrogen-related ions (NO3-, NO2-, and NH4+), and the concentration of dissolved organic carbon in the surrounding environment drive the variation of the plastisphere. But environmental physicochemical properties explain less of the microbial community variation in the plastisphere than that in the aquatic environment. Niche-based processes govern the assembly of the plastisphere community, while neutral-based processes dominate the community assembly of the aquatic environment. Furthermore, compared to the aquatic environment, the plastisphere has a network of less complexity, more modules, higher modularity, and more competitive links in freshwater ecosystems, but the pattern is reversed in seawater ecosystems. Altogether, the microbial ecology of the new anthropogenic ecosystem-plastisphere-is unique and exerts different effects in freshwater and seawater ecosystems.

Circ_0001821 knockdown suppresses growth, metastasis, and TAX resistance of non-small-cell lung cancer cells by regulating the miR-526b-5p/GRK5 axis.

Non-small-cell lung cancer (NSCLC) remains a huge obstacle to human health. Certain circular RNAs endow with crucial regulatory roles in NSCLC progression. Here, we investigated the functional effects of circ_0001821 on cellular behaviors of NSCLC cells and explored the possible mechanism. The expression of circ_0001821, microRNA (miR)-526b-5p, and G protein-coupled receptor kinase 5 (GRK5) was determined by quantitative real-time polymerase chain reaction or Western blot assay. Clonogenicity in NSCLC cells was detected via colony formation assay. Cell migration and invasion were monitored by Transwell assay. Cell sensitivity to paclitaxel (TAX) evaluated by Cell Counting Kit-8 assay. Cell apoptosis was assessed by flow cytometry, caspase-3 activity, and caspase-9 activity. The targeted relationship between miR-526b-5p and circ_0001821 or GRK5 was confirmed by dual-luciferase reporter or RNA pull-down assay. Moreover, the role of circ_0001821 in vivo was examined by xenograft model assay. The results presented that the expression of circ_0001821 and GRK5 was increased, while miR-526b-5p expression was decreased in NSCLC tissues and cells. Circ_0001821 knockdown reduced colony formation ability and metastasis ability but enhanced TAX sensibility and apoptosis of NSCLC cells, which was attenuated by miR-526b-5p inhibition or GRK5 overexpression. Circ_0001821 targeted miR-526b-5p, and miR-526b-5p targeted GRK5. Circ_0001821 could upregulate GRK5 expression by sponging miR-526b-5p. Depletion of circ_0001821 also blocked tumor growth in vivo. In conclusion, the depletion of circ_0001821 inhibited NSCLC progression, at least in part, by modulating the miR-526b-5p/GRK5 axis.

The decomposition process and nutrient release of invasive plant litter regulated by nutrient enrichment and water level change.

Wetlands are vulnerable to plant invasions and the decomposition of invasive plant litter could make impacts on the ecosystem services of wetlands including nutrient cycle and carbon sequestration. However, few studies have explored the effects of nutrient enrichment and water level change on the decomposition of invasive plant litter. In this study, we conducted a control experiment using the litterbag method to compare the decomposition rates and nutrient release in the litter of an invasive plant Alternanthera philoxeroides in three water levels and two nutrient enrichment treatments. This study found that the water level change and nutrient enrichment showed significant effects on the litter decomposition and nutrient dynamic of A. philoxeroides. The increase of water level significantly reduced the decomposition rate and nutrient release of litter in the nutrient control treatment, whereas no clear relationship was observed in the nutrient enrichment treatment, indicating that the effect of water level change on litter decomposition might be affected by nutrient enrichment. At the late stage of decomposition, the increase of phosphorus (P) concentration and the decrease of the ratio of carbon to P suggested that the decomposition of invasive plant litter was limited by P. Our results suggest that controlling P enrichment in water bodies is essential for the management of invasive plant and carbon sequestration of wetlands. In addition, the new index we proposed could provide a basis for quantifying the impact of invasive plant litter decomposition on carbon cycle in wetlands.

Magnitudes and environmental drivers of greenhouse gas emissions from natural wetlands in China based on unbiased data.

Whether natural wetlands serve as the source or sink of greenhouse gases (GHGs) remains uncertain. Wetlands in China are diverse in type and abundant in quantity and differ greatly in spatial distribution, environmental conditions, and GHG fluxes. However, few studies focused on the differences in GHG emissions from different types of natural wetlands. Here, we adopted strict data collection criteria to create comprehensive and detailed datasets of fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from the marsh, coastal, lake, and river wetlands in China, and relevant environmental variables. Our study synthesized 265 field observations on GHGs that lasted at least one year (covering both the growing season and non-growing season) from 109 studies, among which CO2 measurements using the opaque chamber method were not included for eliminating the influence of absence of photosynthesis on net CO2 accounting. We found that CH4 contributed the largest warming effect among the three types of GHGs, and coastal and river wetlands respectively acted as the mitigators and motivators of global warming among the four types of wetlands. Correlation and regression analyses suggested that geographic location, soil moisture and organic carbon, and contents of nitrogen, phosphorus, and dissolved oxygen jointly drove wetland GHG fluxes. The comprehensive global warming potential of Chinese natural wetlands was estimated as 427 Tg CO2-equivalents year-1, which might result from increased wetland drainage, reclamation, and external nutrient inputs. This study highlights the incorporation of the full year-round GHG monitoring data without using opaque chambers to measure CO2 flux when extrapolating net GHG emissions and gives implications for natural wetland management and global warming mitigation strategies.

A combined method for the source apportionment of sediment organic carbon in rivers.

Organic carbon sources apportionment in river sediments is crucial to the output management of organic carbon. We conducted a source apportionment of sediment organic carbon in four rivers in Shaanxi Province, China, with a novel method that combined environmental scanning electron microscopy and energy dispersive X-ray spectrometry (ESEM-EDAX), principal component analysis (PCA), 16S rRNA sequencing, microbial community metabolic prediction, and positive matrix factorization (PMF). According to the ESEM-EDAX results, the sources of light fraction organic carbon (LFOC) were the vegetation residues and the organic carbon adsorbed on them; and the source of heavy fraction organic carbon (HFOC) was organic carbon wrapped in particles. Moreover, 16S rRNA sequencing results of LFOC and HFOC concerning microbes demonstrated that LFOC was mainly composed of carbohydrate, cellulose, and alky-aromatic compounds, and that carbohydrate with high molecular weight might be a part of HFOC. Based on the results of microbial community metabolic prediction, PCA, and PMF, we found dissolved organic carbon (DOC) was mainly from lipopolysaccharide biosynthesis, apoptosis, and decomposition of carboxylic acids. And it might be mainly composed of lipopolysaccharide, carbohydrates, and organic acid with low molecular. To reflect the appearance of a specific DOC type, three biomarkers were proposed based on the microbial relative abundance and specificity. This research proposed a new method to trace the sources of organic carbon and established microbial biomarkers for the appearance of specific DOC, which would promote the understanding of organic carbon sources into microbes. Thus, this research provides new perspectives in the source apportionment and the life cycle of organic carbon in rivers.

"Microplastic communities" in different environments: Differences, links, and role of diversity index in source analysis.

Microplastics have been detected in various environments, yet the differences between microplastics in different environments are still largely unknown. Scientists have proposed the concept of the "microplastic cycle," but the evidence for the movement of microplastics between different environments is still scarce. By screening the literature and extracting information, we obtained microplastic data from 709 sampling sites in freshwater, seawater, freshwater sediment, sea sediment, and soil in China. Based on the similarity between microplastics and biological communities, here we propose the concept of a "microplastic community" and examine the differences, links, and diversity of microplastic communities in different environments. Wilcoxon sign-ranks test, Kruskal-Wallis test, and analysis of similarities (ANOSIM) showed that there were significant differences in abundance, proportion of small microplastics, and community composition (shape, color, and polymer types) of microplastics in different environments. The Mantel test showed that there were significant correlations between microplastic community composition in different environments. Network analysis based on community similarity further confirmed the links between microplastic communities. The distance decay models revealed that the links weakened with the increase of geographic distance, suggesting that sampling sites with closed geographical locations had similar pollution sources and more easily to migrate or exchange microplastics. The microplastic diversity integrated index (MDII) was established based on the diversity of microplastic shape, color, and polymer types, and its indication of the number of microplastic pollution sources was verified by the statistical fitting relationship between the number of industrial pollution sources and MDII. Our study provides new insight into the differences and links between microplastics in different environments, which contributes to the microplastic risk assessment and demonstrates the "microplastic cycle." The establishment of the microplastic diversity integrated index could be used in source analysis of microplastics.

Effects of heavy metals on microbial communities in sediments and establishment of bioindicators based on microbial taxa and function for environmental monitoring and management.

Heavy metals have always been a research hotspot due to their persistence, hazard and bioaccumulation. Microorganisms are highly sensitive to heavy metal pollution and play an important role in the material cycling and energy flow of the ecosystem. In order to further explore the influence of heavy metals on the diversity, composition, and function of microbial communities in the wetland sediment ecosystem, and to find suitable indicators to reflect heavy metal pollution status, we collected sediments from Huangjinxia nature reserve and determined the physicochemical properties, heavy metal (Cu, Cr, Ni, Pb, Zn, and Mn) concentrations, and microbial information. We found that: the contamination status of the study area stood at a moderate level evaluated by the pollution load index (PLI); heavy metals explained more of microbial community variation than the sediment physicochemical properties; in particular, Cr and Mn negatively affected microbial α-diversity; heavy metals significantly affected the structure of microbial communities, elements Cr, Pb, and Zn showed uniformly negative associations with the relative abundance of bacteria Nitrospirae (including class Nitrospira and order Nitrospirales), Bacteroidetes (including class Bacteroidia), and Verrucomicrobia; moreover, heavy metals affected predicted functions of microbial communities, including metabolic functions, genetic information processes, and functions related to the carbon cycle and the nitrogen cycle. Based on the relative abundance of sensitive microbial taxa and predicted functions, bioindicators [Bacteroidia], 1/[Nitrospira], 1/[Nitrification], and 1/[Aerobic nitrite oxidation] were established to reflect and predict the contamination status of heavy metals in sediments. Our in-depth research on the effects of heavy metals on microorganisms and the establishment of bioindicators provide references and new perspectives for environmental monitoring and management.

Factors controlling organic carbon distributions in a riverine wetland.

As a significant reservoir of organic carbon (OC), natural wetlands play an important role in mitigating greenhouse effects. To determine what factors might influence OC, we analyzed the distributions of dissolved organic carbon (DOC), light fraction organic carbon (LFOC), and heavy fraction organic carbon (HFOC) in sediments taken from the Yanghe River Wetland (YRW) and assessed the effects of several environmental variables on the distribution of the different carbon types. The microbial community abundances and compositions of the sampled sediments were analyzed by 16S rRNA amplicon sequencing. Redundancy analysis (RDA) was used to reveal the environmental factors that affect the distribution of OC. The DOC and LFOC contents varied significantly in the research area, while HFOC content showed no variation. The DOC content was significantly affected by sediment pH, vegetation height, and microbial abundances, and the LFOC content was significantly affected by water pH. We also proposed a novel indicator to study the microbial effect on the distribution of OC content in wetlands: weighted abundance of related microbes (WARM). This study identifies the environmental factors that could affect the distribution of OC in a riverine wetland and outlines the calculation of a novel indicator.

Impact of microplastics on microbial community in sediments of the Huangjinxia Reservoir-water source of a water diversion project in western China.

Microplastics have been of great concern in recent years due to bioaccumulation and their toxic effects on organisms. However, few studies have focused on microplastics in the natural river ecosystem and the relationship between microplastics and microbes. Therefore, to understand the concentration and characteristics of microplastics and explore the impact of microplastics on the microbial community, sediment samples were collected from the Huangjinxia Reservoir, which is the water source of a water diversion project in western China. Results showed that the concentration of microplastics in the study area ranged from 233.33 ± 70.24 items·kg-1 to 870 ± 238.12 items·kg-1, with an average of 558.10 ± 291.45 items·kg-1. After clustering the sediments according to the microplastic concentration, there was a significant difference in the Chao1 index of microbial community between groups, indicating that microplastics might have affected microbial diversity of the sediments. Additionally, Anosim, MRPP, and Amova analyses indicated that microplastics might have an impact on the structure and composition of microbial communities. Moreover, function prediction assays suggested that microplastics might have differential impacts on various microbial community functions. To our knowledge, this is the first study to explore the impact of microplastics on microbes in sediments of a natural river ecosystem, providing a basis for further study of the interaction between microplastics and microbes in similar habitats.

Differences of the microbial community structures and predicted metabolic potentials in the lake, river, and wetland sediments in Dongping Lake Basin.

In freshwater ecosystems, wetlands are generally distinguished from deep-water ecosystems by 2-m water level as boundary. However, the difference of sediment microbial communities between wetlands and deep-water ecosystems is still unclear. We combined 16S rRNA gene sequencing and community metabolic prediction to compare sediment microbial communities and predicted metabolic genes of wetlands (natural and constructed wetlands) and deep-water ecosystems (river and lake) along with environmental factors in summer and autumn in Dongping Lake Basin. Results showed that the deep-water ecosystems had significantly higher community richness than the wetlands in autumn in the freshwater basin, which was mostly related to the pH of sediments. However, no significant difference in community richness was found in summer. Besides, the composition of both predicted metabolic genes and microbial communities was significantly affected by dissolved organic carbon (DOC) and dissolved oxygen (DO). The wetlands exhibited high predicted gene abundances related to xenobiotic biodegradation possibly due to the high DOC or DO level. Compared with the wetlands, most of the deep-water ecosystems exhibited high predicted gene abundances related to element (carbon, nitrogen, and sulfur) metabolism possibly due to the low DOC and DO levels in the freshwater basin. This study can expand the knowledge of ecological function distribution and detoxification mechanism of microbial communities in freshwater ecosystems.