Effects of microplastics on greenhouse gas emissions and microbial communities in sediment of freshwater systems

Microplastics enhanced the allelopathy of pyrogallol on toxic Microcystis with additional risks: Microcystins release and greenhouse gases emissions

Cyanobacteria blooms (CBs) caused by eutrophication pose a global concern, especially Microcystis aeruginosa (M. aeruginosa), which could release harmful microcystins (MCs). The impact of microplastics (MPs) on allelopathy in freshwater environments is not well understood. This study examined the joint effect of adding polystyrene (PS-MPs) as representative MPs and two concentrations (2 and 8 mg/L) of pyrogallol (PYR) on the allelopathy of M. aeruginosa. The results showed that the addition of PS-MPs intensified the inhibitory effect of 8 mg/L PYR on the growth and photosynthesis of M. aeruginosa. After a 7-day incubation period, the cell density decreased to 69.7 %, and the chl-a content decreased to 48 % compared to the condition without PS-MPs (p < 0.05). Although the growth and photosynthesis of toxic Microcystis decreased with the addition of PS-MPs, the addition of PS-MPs significantly resulted in a 3.49-fold increase in intracellular MCs and a 1.10-fold increase in extracellular MCs (p < 0.05). Additionally, the emission rates of greenhouse gases (GHGs) (carbon dioxide, nitrous oxide and methane) increased by 2.66, 2.23 and 2.17-fold, respectively (p < 0.05). In addition, transcriptomic analysis showed that the addition of PS-MPs led to the dysregulation of gene expression related to DNA synthesis, membrane function, enzyme activity, stimulus detection, MCs release and GHGs emissions in M. aeruginosa. PYR and PS-MPs triggered ROS-induced membrane damage and disrupted photosynthesis in algae, leading to increased MCs and GHG emissions. PS-MPs accumulation exacerbated this issue by impeding light absorption and membrane function, further heightening the release of MCs and GHGs emissions. Therefore, PS-MPs exhibited a synergistic effect with PYR in inhibiting the growth and photosynthesis of M. aeruginosa, resulting in additional risks such as MCs release and GHGs emissions. These results provide valuable insights for the ecological risk assessment and control of algae bloom in freshwater ecosystems.

Effects of microplastics on sedimentary greenhouse gas emissions and underlying microbiome-mediated mechanisms: A comparison of sediments from distinct altitudes

Microplastics (MPs) are emerging contaminants in aquatic ecosystems that can profoundly affect carbon and nitrogen cycling. However, the impact mechanisms of MPs on sedimentary greenhouse gas (GHG) emissions at distinct altitudes remain poorly elucidated. Here, we investigated the effects of polyvinyl chloride (PVC) and polylactic acid (PLA) on sedimentary CO2, CH4, and N2O emissions at distinct altitudes of the Yellow River. PVC increased the relative abundance of denitrifiers (e.g., Xanthobacteriaceae, Rhodocyclaceae) to promote N2O emissions, whereas PLA reduced the abundance of AOA gene and denitrifiers (e.g., Pseudomonadaceae, Sphingomonadaceae), impeding N2O emissions. Both PVC and PLA stimulated the growth of microbes (Saprospiraceae, Aquabacterium, and Desulfuromonadia) associated with complex organics degradation, leading to increased CO2 emissions. Notably, the concurrent inhibition of PLA on mcrA and pmoA genes led to its minimal impact on CH4 emissions. High-altitude MQ sediments, characterized by abundant substrate and a higher abundance of functional genes (AOA, AOB, nirK, mcrA), demonstrated higher GHG emissions. Conversely, lower microbial diversity rendered the low-altitude LJ microbial community more susceptible to PVC, leading to a more significant promotion on GHG emissions. This study unequivocally confirms that MPs exacerbate GHG emissions via microbiome-mediated mechanisms, providing a robust theoretical foundation for microplastic control to mitigate global warming.

Biochar immobilized hydrolase degrades PET microplastics and alleviates the disturbance of soil microbial function via modulating nitrogen and phosphorus cycles

Microplastics (MPs) pose an emerging threat to soil ecological function, yet effective solutions remain limited. This study introduces a novel approach using magnetic biochar immobilized PET hydrolase (MB-LCC-FDS) to degrade soil polyethylene terephthalate microplastics (PET-MPs). MB-LCC-FDS exhibited a 1.68-fold increase in relative activity in aquatic solutions and maintained 58.5 % residual activity after five consecutive cycles. Soil microcosm experiment amended with MB-LCC-FDS observed a 29.6 % weight loss of PET-MPs, converting PET into mono(2-hydroxyethyl) terephthalate (MHET). The generated MHET can subsequently be metabolized by soil microbiota to release terephthalic acid. The introduction of MB-LCC-FDS shifted the functional composition of soil microbiota, increasing the relative abundances of Microbacteriaceae and Skermanella while reducing Arthobacter and Vicinamibacteraceae. Metagenomic analysis revealed that MB-LCC-FDS enhanced nitrogen fixation, P-uptake and transport, and organic-P mineralization in PET-MPs contaminated soil, while weakening the denitrification and nitrification. Structural equation model indicated that changes in soil total carbon and Simpson index, induced by MB-LCC-FDS, were the driving factors for soil carbon and nitrogen transformation. Overall, this study highlights the synergistic role of magnetic biochar-immobilized PET hydrolase and soil microbiota in degrading soil PET-MPs, and enhances our understanding of the microbiome and functional gene responses to PET-MPs and MB-LCC-FDS in soil systems.

Adding carbon sources to the substrates enhances Cr and Ni removal and mitigates greenhouse gas emissions in constructed wetlands

Constructed wetlands for wastewater treatment pose challenges related to long-term operational efficiency and greenhouse gas emissions on a global scale. This study investigated the impact of adding peat, humic acid, and biochar into the substrates of constructed wetlands and focused on Cr, and Ni removal, greenhouse gas emissions, and microbial communities in constructed wetlands. Biochar addition treatment achieved the highest removal efficiencies for total Cr (99.96%), Cr (VI) (100%), and total Ni (91.04%). Humic acid and biochar addition both significantly increased the heavy metal content in wetland plant Leersia hexandra and substrates of constructed wetlands. Further analysis of microbial community proportions by high-throughput sequencing revealed that biochar and humic acid treatments enhanced Cr and Ni removal efficiency by increasing the abundance of Bacteroidetes, Geobacter and Ascomycota. Humic acid addition treatment reduced CO2 emissions by decreasing the abundance of Bacteroidetes and increasing that of Basidiomycota. Peat treatment decreased CH4 emissions by reducing the abundance of the Bacteroidetes. Biochar treatment increased the abundance of the Firmicutes, Bacteroidetes, Proteobacteria as well as Basidiomycota, resulting in reduced N2O emissions. Biochar and humic acid treatments efficiently removed heavy metals from wastewater and mitigated greenhouse gas emissions in constructed wetlands by modifying the microbial communities.

Impacts of microplastic concentrations and sizes on the rheology properties of lake sediments

The information concerning the effects of microplastics (MPs) on lake sediment environment, particularly structural properties, is still scant. This study aimed to investigate the effect of MPs characteristics (including concentration and size) on the sediment rheological properties, which affected sediment resuspension. After 60-day experiments, it was found that (0.5-2 %) MP in sediments decreased sediment viscosity, yield stress, and flow point shear stress by 14.7-38.4 %, 3.9-24.1 % and 13.5-36.5 %. Besides, sediment (with 50 μm MP addition) yield stress and flow point shear stress also dropped by 1.1-14.1 % and 9.6-12.9 % compared to 100 and 200 μm MP addition. The instability in sediment structure could be attributed to MP-induced EPS production and cation exchange capacity (CEC) changes. Accordingly, the decreases in rheological properties induced by different sizes and concentrations MPs might facilitate the sediments resuspension with wind and wave disturbances. The study shed light on previously overlooked environmental issues caused by MPs characteristics from a new perspective, thereby enhancing our understanding about the environmental behavior of MPs in lake sediment ecosystems.

Modeling of microplastics degradation in aquatic environments using an experimental plan

The aim of this article is to apply advanced predictive modeling techniques to understand the degradation process of microplastics in aquatic environments. Utilizing a Fractional Factorial Central Composite Experimental Plan, this study seeks to develop precise predictive statistical models that enable forecasting the quantity of pollutants generated during the degradation of microplastics under various environmental conditions. This tool was applied to model changes in DOC (dissolved organic carbon) and DEHP (bis(2-ethylhexyl) phthalate) values during the degradation of microplastics in aquatic ecosystems. The methods were developed using data derived from laboratory tests conducted using the GC-MS technique. The obtained approximating functions, considering factors such as degradation time, water temperature, and particle size, significantly reduced the analysis time. A two-stage verification of the approximating functions was conducted, considering the accuracy of the function form, its adequacy, the statistical significance of input variables, and their correlation with DOC and DEHP. The employed a Fractional Factorial Central Composite Experimental Plan allowed for the simultaneous reduction in the number of experiments and prediction of the influence of variables on the output values. Precise predictive models support understanding of the microplastic degradation process, facilitating the development of effective strategies for managing this pollution.

Effects of microplastics on microbial community structure and wheatgrass traits in Pb-contaminated riparian sediments under flood-drainage-planting conditions

The coexistence of microplastics (MPs) and heavy metals in sediments has caused a potential threat to sediment biota. However, differences in the effects of MPs and heavy metals on microbes and plants in sediments under different sediment conditions remain unclear. Hence, we investigated the influence of polyethylene (PE) and polylactic acid (PLA) MPs on microbial community structure, Pb bioavailability, and wheatgrass traits under sequential incubation of sediments (i.e., flood, drainage, and planting stages). Results showed that the sediment enzyme activities presented a dose-dependent effect of MPs. Besides, 10 % PLA MPs significantly increased the F1 fractions in three stages by 11.13 %, 30.10 %, and 17.26 %, respectively, thus resulting in higher Pb mobility and biotoxicity. MPs altered sediment bacterial composition and structures, and bacterial community differences were evident in different incubation stages. Moreover, the co-exposure of PLA MPs and Pb significantly decreased the shoot length and total biomass of wheatgrass and correspondingly activated the antioxidant enzyme activity. Further correlation analysis demonstrated that community structure induced by MPs was mainly driven by sediment enzyme activity. This study contributes to elucidating the combined effects of MPs and heavy metals on sediment ecosystems under different sediment conditions.

Non-negligible impact of microplastics on wetland ecosystems

There has been much concern about microplastic (MP) pollution in marine and soil environments, but attention is gradually shifting towards wetland ecosystems, which are a transitional zone between aquatic and terrestrial ecosystems. This paper comprehensively reviews the sources of MPs in wetland ecosystems, as well as their occurrence characteristics, factors influencing their migration, and their effects on animals, plants, microorganisms, and greenhouse gas (GHG) emissions. It was found that MPs in wetland ecosystems originate mainly from anthropogenic sources (sewage discharge, and agricultural and industrial production) and natural sources (rainfall-runoff, atmospheric deposition, and tidal effects). The most common types and forms of MPs identified in the literature were polyethylene and polypropylene, fibers, and fragments. The migration of MPs in wetlands is influenced by both non-biological factors (the physicochemical properties of MPs, sediment characteristics, and hydrodynamic conditions) and biological factors (the adsorption and growth interception by plant roots, ingestion, and animal excretion). Furthermore, once MPs enter wetland ecosystems, they can impact the resident microorganisms, animals, and plants. They also have a role in global warming because MPs act as unique exogenous carbon sources, and can also influence GHG emissions in wetland ecosystems by affecting the microbial community structure in wetland sediments and abundance of genes associated with GHG emissions. However, further investigation is needed into the influence of MP type, size, and concentration on the GHG emissions in wetlands and the underlying mechanisms. Overall, the accumulation of MPs in wetland ecosystems can have far-reaching consequences for the local ecosystem, human health, and global climate regulation. Understanding the effects of MPs on wetland ecosystems is essential for developing effective management and mitigation strategies to safeguard these valuable and vulnerable environments.

Effects of microplastics on the structure and function of bacterial communities in sediments of a freshwater lake

As an emerging pollutant, microplastics (MPs) cause widespread concern around the world owing to the serious threat they pose to ecosystems. In particular, sediments are thought to be the long-term sink for the continual accumulation of MPs in freshwater ecosystems. Polyethylene (PE) and polyethylene terephthalate (PET) have been frequently detected with large concentration variations in freshwater sediments from the lower reaches of the Yangtze River, one of the most economically developed regions in China, characterized by accelerated urbanization and industrialization, high population density and high plastics consumption. However, the impact of PE and PET on the sedimental bacterial community composition and its function has not been well reported for this specific region. Herein, PE and PET particles were added to freshwater sediments to assess the effects of different MP types on the bacterial community and its function, using three concentrations (500, 1500 and 2500 items/kg) per MP and incubations of 35, 105 and 175 days, respectively. This study identified a total of 68 phyla, 211 classes, 518 orders, 853 families and 1745 genera. Specifically, Proteobacteria, Chloroflexi, Acidobacteriota, Actinobacteriota and Firmicutes were the top five phyla. A higher bacterial diversity was obtained in control sediments than in the MP-treated sediments. The presence of MPs, whether PET or PE, had significant impact on the bacterial diversity, community structure and community composition. PICRUSt2 and FAPOTAX predictions demonstrated that MPs could potentially affect the metabolic pathways and ecologically functional groups of bacteria in the sediment. Besides the MP-related factors, such as the type, concentration and incubation time, the physicochemical parameters had an effect on the structure and function of the bacterial community in the freshwater sediment. Taken together, this study provides useful information for further understanding how MPs affect bacterial communities in the freshwater sediment of the lower reaches of the Yangtze River, China.

Simultaneous achievement of removing bensulfuron-methyl and reducing CO2 emission in paddy soil by Acinetobacter YH0317 immobilized boron-doping biochar

Herbicide residue and greenhouse gas (GHG) emission are two main problems in the paddy rice field, which have barely been considered simultaneously. Herein, a bensulfuron-methyl (BSM)-degrading bacterium named Acinetobacter YH0317 was successfully immobilized on two kinds of biochars and subsequently applied in the paddy soil. The BSM removal rate of Acinetobacter YH0317 immobilized boron-doping biochar (BBC) was 80.42% after 30 d, which was significantly higher than that of BBC (39.05%) and Acinetobacter YH0317 (49.10%) applied alone. BBC acting as an immobilized carrier could enable Acinetobacter YH0317 to work in harsh and complex environment and thus improve the BSM removal efficiency. The addition of Acinetobacter YH0317 immobilized BBC (TP5) significantly improved the soil physicochemical properties (pH, SOC, and NH4+-N) and increased the diversity of soil microbial community compared to control group (CG). Meanwhile, Acinetobacter YH0317 immobilized BBC reduced the CO2-equivalent emission by 41.0%. Metagenomic sequencing results revealed that the decreasing CO2 emission in TP5 was correlated with carbon fixation gene (fhs), indicating that fhs gene may play an important role in reducing CO2 emission. The work presents a practical and supportive technique for the simultaneous achievement on the soil purification and GHG emission reduction in paddy soil.

Effects of polypropylene microplastics on carbon dioxide dynamics in intertidal mangrove sediments

Microplastics (MPs) in soil can influence CO2 dynamics by altering organic carbon (OC) and microbial composition. Nevertheless, the fluctuation of CO2 response attributed to MPs in mangrove sediments is unclear. This study explores the impact of micro-sized polypropylene (mPP) particles on the carbon dynamics of intertidal mangrove sediments. In the high-tide level sediment, after 28 days, the cumulative CO2 levels for varying mPP dosages were as follows: 496.86 ± 2.07, 430.38 ± 3.84 and 447.09 ± 1.72 mg kg-1 for 0.1%, 1% and 10% (w/w) mPP, respectively. The CO2 emissions were found to be increased with a 0.1% (w/w) mPP level and decreased with 1% and 10% (w/w) mPP at high-tide level sediment, suggesting a tide level-specific dose dependence of the CO2 emission pattern in mangrove sediments. Overall, results indicated that the presence of mPP in mangrove sediments would potentially affect intertidal total CO2 storage under given experimental conditions.

Impacts of microplastic contamination on the rheology properties of sediments in a eutrophic shallow lake

Microplastic (MP) contamination is a growing global concern, with lake sediments serving as a significant sink for MP due to both anthropogenic and natural activities. Given the increasing evidence of MP accumulation in sediments, it was crucial to assess their influence on sediment erosion resistance, which directly affected sediment resuspension. To fill this gap, this study focused on the effect of MP on the sediments rheological properties. After 60-day experiments, it was found that MP addition into sediments reduced sediment viscosity, yield stress, and flow point shear stress. Meanwhile, MPs also significantly altered sediment properties and extracellular polymer composition. MP addition reduced extracellular polymeric substances production and cation exchange capacity, which then worked together and led to a weak sediment structure. Seemingly, MPs changed fluid sediment characteristics and caused stronger fluidity under less shear force. Consequently, the accumulation of MP might facilitate the resuspension of sediments under smaller wind and wave disturbances. This study provided novel insights into the direct impact of MPs on sediment physical properties using rheology, thereby enhancing our understanding of the environmental behavior of MPs in lake ecosystems.

Plastic Paradox in Blue Carbon Ecosystems

Plastics are rapidly accumulating in blue carbon ecosystems, i.e., mangrove forests, tidal marshes, and seagrass meadows. Accumulated plastic is diverted from the ocean, but the extent and nature of impacts on blue carbon ecosystem processes, including carbon sequestration, are poorly known. Here, we explore the potential positive and negative consequences of plastic accumulation in blue carbon ecosystems. We highlight the effects of plastic accumulation on organic carbon stocks and sediment biogeochemistry through microbial metabolism. The notion of beneficial plastic accumulation in blue carbon ecosystems is controversial, yet considering the alternative impacts of plastics on oceanic and aboveground environments, this may be the "lesser of evils". Using environmental life cycle impact assessment, we propose a research framework to address the potential positive and negative impacts of plastic accumulation in blue carbon ecosystems. Considering the multifaceted benefits, we prioritize expanding and managing blue carbon ecosystems, which may help with ecosystem conservation, as well as mitigating the negative effects of plastic.

Potential synergy of microplastics and nitrogen enrichment on plant holobionts in wetland ecosystems

Wetland ecosystems are global hotspots for environmental contaminants, including microplastics (MPs) and nutrients such as nitrogen (N) and phosphorus (P). While MP and nutrient effects on host plants and their associated microbial communities at the individual level have been studied, their synergistic effects on a plant holobiont (i.e., a plant host plus its microbiota, such as bacteria and fungi) in wetland ecosystems are nearly unknown. As an ecological entity, plant holobionts play pivotal roles in biological nitrogen fixation, promote plant resilience and defense chemistry against pathogens, and enhance biogeochemical processes. We summarize evidence based on recent literature to elaborate on the potential synergy of MPs and nutrient enrichment on plant holobionts in wetland ecosystems. We provide a conceptual framework to explain the interplay of MPs, nutrients, and plant holobionts and discuss major pathways of MPs and nutrients into the wetland milieu. Moreover, we highlight the ecological consequences of loss of plant holobionts in wetland ecosystems and conclude with recommendations for pending questions that warrant urgent research. We found that nutrient enrichment promotes the recruitment of MPs-degraded microorganisms and accelerates microbially mediated degradation of MPs, modifying their distribution and toxicity impacts on plant holobionts in wetland ecosystems. Moreover, a loss of wetland plant holobionts via long-term MP-nutrient interactions may likely exacerbate the disruption of wetland ecosystems' capacity to offer nature-based solutions for climate change mitigation through soil organic C sequestration. In conclusion, MP and nutrient enrichment interactions represent a severe ecological risk that can disorganize plant holobionts and their taxonomic roles, leading to dysbiosis (i.e., the disintegration of a stable plant microbiome) and diminishing wetland ecosystems' integrity and multifunctionality.

Microplastic pollution interaction with disinfectant resistance genes: research progress, environmental impacts, and potential threats

The consumption of disposable plastic products and disinfectants has surged during the global COVID-19 pandemic, as they play a vital role in effectively preventing and controlling the spread of the virus. However, microplastic pollution and the excessive or improper use of disinfectants contribute to the increased environmental tolerance of microorganisms. Microplastics play a crucial role as vectors for microorganisms and plankton, facilitating energy transfer and horizontal gene exchange. The increase in the use of disinfectants has become a driving force for the growth of disinfectant resistant bacteria (DRB). A large number of microorganisms can have intense gene exchange, such as plasmid loss and capture, phage transduction, and cell fusion. The reproduction and diffusion rate of DRB in the environment is significantly higher than that of ordinary microorganisms, which will greatly increase the environmental tolerance of DRB. Unfortunately, there is still a huge knowledge gap in the interaction between microplastics and disinfectant resistance genes (DRGs). Accordingly, it is critical to comprehensively summarize the formation and transmission routes of DRGs on microplastics to address the problem. This paper systematically analyzed the process and mechanisms of DRGs formed by microbes. The interaction between microplastics and DRGs and the contribution of microplastic on the diffusion and spread of DRGs were expounded. The potential threats to the ecological environment and human health were also discussed. Additionally, some challenges and future priorities were also proposed with a view to providing useful basis for further research.

Regulation of ARGs abundance by biofilm colonization on microplastics under selective pressure of antibiotics in river water environment

Interactions of microplastics (MPs) biofilm with antibiotic resistance genes (ARGs) and antibiotics in aquatic environments have made microplastic biofilm an issue of keen scholarly interest. The process of biofilm formation and the degree of ARGs enrichment in the presence of antibiotic-selective pressure and the impact on the microbial community need to be further investigated. In this paper, the selective pressure of ciprofloxacin (CIP) and illumination conditions were investigated to affect the physicochemical properties, biomass, and extracellular polymer secretion of polyvinyl chloride (PVC) microplastic biofilm. In addition, relative copy numbers of nine ARGs were analyzed by real-time quantitative polymerase chain reaction (qPCR). In the presence of CIP, microorganisms in the water and microplastic biofilm were more inclined to carry associated ARGs (2-3 times higher), which had a contributing effect on ARGs enrichment. The process of pre-microplastic biofilm formation might have an inhibitory effect on ARGs (total relative abundance up to 0.151) transfer and proliferation compared to the surrounding water (total relative abundance up to 0.488). However, in the presence of CIP stress, microplastic biofilm maintained the abundance of ARGs (from 0.151 to 0.149) better compared to the surrounding water (from 0.488 to 0.386). Therefore, microplastic biofilm act as abundance buffer island of ARGs stabilizing the concentration of ARGs. In addition, high-throughput analyses showed the presence of antibiotic-resistant (Pseudomonas) and pathogenic (Vibrio) microorganisms in biofilm under different conditions. The above research deepens our understanding of ARGs enrichment in biofilm and provides important insights into the ecological risks of interactions between ARGs, antibiotics, and microplastic biofilm.

Recognition and detection technology for microplastic, its source and health effects

Microplastic (MP) is ubiquitous in the environment which appeared as an immense intimidation to human and animal health. The plastic fragments significantly polluted the ocean, fresh water, food chain, and other food items. Inadequate maintenance, less knowledge of adverse influence along with inappropriate usage in addition throwing away of plastics items revolves present planet in to plastics planet. The present study aims to focus on the recognition and advance detection technologies for MPs and the adverse effects of micro- and nanoplastics on human health. MPs have rigorous adverse effect on human health that leads to condensed growth rates, lessened reproductive capability, ulcer, scrape, and oxidative nervous anxiety, in addition, also disturb circulatory and respiratory mechanism. The detection of MP particles has also placed emphasis on identification technologies such as scanning electron microscopy, Raman spectroscopy, optical detection, Fourier transform infrared spectroscopy, thermo-analytical techniques, flow cytometry, holography, and hyperspectral imaging. It suggests that further research should be explored to understand the source, distribution, and health impacts and evaluate numerous detection methodologies for the MPs along with purification techniques.

Organic amendment in climate change mitigation: Challenges in an era of micro- and nanoplastics

As a global strategy for mitigating climate change, organic amendments play critical roles in restoring stocks in carbon (C) depleted soils, preserving existing stocks to prevent further soil organic carbon (SOC) loss, and enhancing C sequestration. However, recent emerging evidence of a significant proportion of micro- and nanoplastics (M/NPs) occurrence in most organic substrates (e.g., compost manure, farmyard manure, and sewage sludge) compromises its role in climate change mitigation. Given the predicted surge of soil M/NPs proliferation in the coming years, we argued whether organic amendment remains a reliable climate change mitigation strategy. Toxicity effects of M/NPs influx within the soil matrix disrupt plants and their associated key microbial taxa responsible for crucial biogeochemical processes and restructuring of SOC, leading to increasing emissions of potent greenhouse gases (GHGs, e.g., CO2, CH4, and N2O) that feedback to aggravate the rapidly changing climate. Here, we summarize evidence based on literature that the discovery of M/NPs in organic substrates compromises its role in the climate change mitigation strategy. We briefly discuss the overview of synthetic fertilizers and their impact on SOC and atmospheric emissions. We discuss the role of organic amends in climate change mitigation and the emergence of M/NPs in it. We discuss M/NPs-induced damages to SOC and subsequent emissions of GHGs. We briefly highlight management approaches to clean organic substrates of M/NPs to improve their use in agrosystems and provide recommendations for future research studies. We found that organic amendment plays pivotal role in modulating the biotic and abiotic drivers responsible for climate mitigation. However, M/NPs in organic amendments weaken the regulatory mechanisms of organic amendments in plant-soil systems. We conclude that organic amendments of soils are critical for restoring SOC and mitigating the rapidly changing climate; yet, the discovery of M/NPs in organic substrates put their usage in a dilemma.

Lake plastisphere as a new biotope in the Anthropocene: Potential pathogen colonization and distinct microbial functionality

The not-homogenous microplastics (MPs) distribution in freshwaters results in distinct microbial communities. Yet knowledge regarding plastisphere in metabolic pathways and element cycling behaviors remains limited. In this study, we collected MPs from 15 sampling sites in the Taihu Lake in China, and found that MPs were widely distributed in this freshwater lake, and dominantly composed of fibrous polyethylene terephthalate. Based on the metagenomic analysis, we found that MPs were colonized by Bacteroidia, Alpha-Proteobacteria, and Bacilli as a filter, but depleted in Verrucomicrobiae. Potential pathogens of plant eudicots and monocots were significantly enriched in plastisphere. Predicted functional profiles involved in the metabolism of other amino acids, biosynthesis of other secondary metabolites, and glycan biosynthesis and metabolism were overrepresented in plastisphere. Regarding elemental cycling, functional genes related to nitrogen fixation and nitrification showed 39.6% and 67.5% decline in plastisphere, whereas the genes involved in denitrification and nitrate reduction were significantly enriched. For sulfur cycles, the plastisphere exhibited higher sulfate reduction and sulfur oxidation system activities. Additionally, the taxonomic compositions and predicted functions in the plastispheres were mainly driven by the stochastic processes, while the deterministic processes were more important for the planktonic communities. The distinctions in the microbial composition, the predicted functionality, and the underly mechanisms between plastisphere and planktonic communities illustrated the unique ecology of the new anthropogenic-related plastisphere ecosystems.

Effects of microplastics on functional genes related to CH4 and N2O metabolism in bacteriophages during manure composting and its planting applications

Microplastics (MPs), as a new type of pollutant, widely exist in livestock and poultry breeding and agricultural soils. However, research on MPs pollution on greenhouse gas emissions in combined planting and breeding systems is lacking, especially from the perspective of phage horizontal gene transfer. Therefore, this paper explores the effects of MPs on functional genes related to CH4 and N2O metabolism in bacteriophages during manure composting and its planting applications. The results of the study indicated that the addition of MPs had an impact on both the physicochemical properties and microbial community structure of manure during the composting process and on the compost-applied rhizosphere soil of lactuca (Lactuca sativa). Specifically, on day 7 of composting, mcrA/pmoA and (nirS+nirK) levels in bacteria in the MP group significantly increased. Additionally, it was observed that the MP group had higher average temperatures during the high-temperature period of composting, which led to a rapid reduction in phages. However, the phage levels quickly recovered during the cooling period. Furthermore, the addition of MPs to the rhizosphere soil resulted in higher levels of nirK. These changes may affect greenhouse gas emissions.

Interaction between microplastic biofilm formation and antibiotics: Effect of microplastic biofilm and its driving mechanisms on antibiotic resistance gene

As two pollutants with similar transport pathways, microplastics (MPs) and antibiotics (ATs) inevitably co-exist in water environments, and their interaction has become a topic of intense research interest for scholars over the past few years. This paper comprehensively and systematically reviews the current interaction between MPs and ATs, in particular, the role played by biofilm developed MPs (microplastic biofilm). A summary of the formation process of microplastic biofilm and its unique microbial community structure is presented in the paper. The formation of microplastic biofilm can enhance the adsorption mechanisms of ATs on primary MPs. Moreover, microplastic biofilm system is a diverse and vast reservoir of genetic material, and this paper reviews the mechanisms by which microplastics with biofilm drive the production of antibiotic resistance genes (ARGs) and the processes that selectively enrich for more ARGs. Meanwhile, the enrichment of ARGs may lead to the development of microbial resistance and the gradual loss of the antimicrobial effect of ATs. The transfer pathways of ARGs affected by microplastic biofilm are outlined, and ARGs dependent transfer of antibiotic resistance bacteria (ARB) is mainly through horizontal gene transfer (HGT). Furthermore, the ecological implications of the interaction between microplastic biofilm and ATs and perspectives for future research are reviewed. This review contributes to a new insight into the aquatic ecological environmental risks and the fate of contaminants (MPs, ATs), and is of great significance for controlling the combined pollution of these two pollutants.

Large-Scale Integration of Amplicon Data Reveals Massive Diversity within Saprospirales, Mostly Originating from Saline Environments

The order Saprospirales, a group of bacteria involved in complex degradation pathways, comprises three officially described families: Saprospiraceae, Lewinellaceae, and Haliscomenobacteraceae. These collectively contain 17 genera and 31 species. The current knowledge on Saprospirales diversity is the product of traditional isolation methods, with the inherited limitations of culture-based approaches. This study utilized the extensive information available in public sequence repositories combined with recent analytical tools to evaluate the global evidence-based diversity of the Saprospirales order. Our analysis resulted in 1183 novel molecular families, 15,033 novel molecular genera, and 188 K novel molecular species. Of those, 7 novel families, 464 novel genera, and 1565 species appeared in abundances at ≥0.1%. Saprospirales were detected in various environments, such as saline water, freshwater, soil, various hosts, wastewater treatment plants, and other bioreactors. Overall, saline water was the environment showing the highest prevalence of Saprospirales, with bioreactors and wastewater treatment plants being the environments where they occurred with the highest abundance. Lewinellaceae was the family containing the majority of the most prevalent species detected, while Saprospiraceae was the family with the majority of the most abundant species found. This analysis should prime researchers to further explore, in a more targeted way, the Saprospirales proportion of microbial dark matter.

Microplastics Reshape the Fate of Aqueous Carbon by Inducing Dynamic Changes in Biodiversity and Chemodiversity

The interactions among dissolved organic matter (DOM), microplastics (MPs) and microbes influence the fate of aqueous carbon and greenhouse gas emissions. However, the related processes and mechanisms remain unclear. Here, we found that MPs determined the fate of aqueous carbon by influencing biodiversity and chemodiversity. MPs release chemical additives such as diethylhexyl phthalate (DEHP) and bisphenol A (BPA) into the aqueous phase. The microbial community, especially autotrophic bacteria such as Cyanobacteria, showed a negative correlation with the additives released from MPs. The inhibition of autotrophs promoted CO₂ emissions. Meanwhile, MPs stimulated microbial metabolic pathways such as the tricarboxylic acid (TCA) cycle to accelerate the DOM biodegradation process, and then the transformed DOM presented low bioavailability, high stability, and aromaticity. Our findings highlight an urgent need for chemodiversity and biodiversity surveys to assess ecological risks from MP pollution and the impact of MPs on the carbon cycle.

Concurrence of microplastics and heat waves reduces rice yields and disturbs the agroecosystem nitrogen cycle

Microplastic pollution and heat waves, as damaging aspects of human activities, have been found to affect crop production and nitrogen (N) cycling in agroecosystems. However, the impacts of the combination of heat waves and microplastics on crop production and quality have not been analyzed. We found that heat waves or microplastics alone had slight effects on rice physiological parameters and soil microbial communities. However, under heat wave conditions, the typical low-density polyethylene (LDPE) and polylactic acid (PLA) microplastics decreased the rice yields by 32.1% and 32.9%, decreased the grain protein level by 4.5% and 2.8%, and decreased the lysine level by 91.1% and 63.6%, respectively. In the presence of heat waves, microplastics increased the allocation and assimilation of N in roots and stems but decreased those in leaves, which resulted in a reduction in photosynthesis. In soil, the concurrence of microplastics and heat waves induced the leaching of microplastics, which resulted in decreased microbial N functionality and disturbed N metabolism. In summary, heat waves amplified the disturbance induced by microplastics on the agroecosystem N cycle and therefore exacerbated the decreases in rice yield and nutrients induced by microplastics, which indicates that the environmental and food risks of microplastics deserve to be reconsidered.

Recent advances in the research on effects of micro/nanoplastics on carbon conversion and carbon cycle: A review

Massive production and spread application of plastics have led to the accumulation of numerous plastics in the global environment so that the proportion of carbon storage in these polymers also increases. Carbon cycle is of fundamental significance to global climate change and human survival and development. With the continuous increase of microplastics, undoubtedly, there carbons will continue to be introduced into the global carbon cycle. In this paper, the impact of microplastics on microorganisms involved in carbon transformation is reviewed. Micro/nanoplastics affect carbon conversion and carbon cycle by interfering with biological fixation of CO₂, microbial structure and community, functional enzymes activity, the expression of related genes, and the change of local environment. Micro/nanoplastic abundance, concentration and size could significantly lead to difference in carbon conversion. In addition, plastic pollution can further affect the blue carbon ecosystem reduce its ability to store CO₂ and marine carbon fixation capacity. Nevertheless, problematically, limited information is seriously insufficient in understanding the relevant mechanisms. Accordingly, it is required to further explore the effect of micro/nanoplastics and derived organic carbon on carbon cycle under multiple impacts. Under the influence of global change, migration and transformation of these carbon substances may cause new ecological and environmental problems. Additionally, the relationship between plastic pollution and blue carbon ecosystem and global climate change should be timely established. This work provides a better perspective for the follow-up study of the impact of micro/nanoplastics on carbon cycle.

Interactions between dissolved organic matter and the microbial community are modified by microplastics and heat waves

Dissolved organic matter (DOM) exists widely in natural waters and plays an important role in river carbon cycles and greenhouse gas emissions through microbial interactions. However, information on DOM-microbe associations in response to environmental stress is limited. River environments are the main carriers of microplastic (MP) pollution, and global heat waves (HWs) are threatening river ecology. Here, through MP exposure and HW simulation experiments, we found that DOM molecular weight and aromaticity were closely related to initial microbial communities. Moreover, MP-derived DOM regulated microbial community abundance and diversity, influenced microorganism succession trajectories as deterministic factors, and competed with riverine DOM for microbial utilization. SimulatedHWs enhanced the MP-derived DOM competitive advantage and drove the microbial community to adopt a K-strategy for effective recalcitrant carbon utilization. Relative to single environmental stressor exposure, combined MP pollution and HWs led to a more unstable microbial network. This study addresses how MPs and HWs drive DOM-microbe interactions in rivers, contributes to an in-depth understanding of the fate of river DOM and microbial community succession processes, and narrows the knowledge gap in understanding carbon sinks in aquatic ecosystems influenced by human activities and climate change.

Impact of microplastics on lead-contaminated riverine sediments: Based on the enzyme activities, DOM fractions, and bacterial community structure

Microplastics (MPs) are able to interact with diverse contaminants in sediments. However, the impacts of MPs on sediment properties and bacterial community structure in heavy metal-contaminated sediments remain unclear. In this study, we investigated the adsorption of Pb(II) by sediment-MPs mixtures and the effects of different concentration MPs on sediment enzyme activities, DOM fractions, and Pb bioavailability in riverine sediments, and further explored the response of sediment microbial community to Pb in the presence of MPs. The results indicated that the addition of MPs significantly decreased the adsorption amount of Pb(II) by sediments, especially decreased by 12.6% at 10% MPs treatment. Besides, the changes in enzyme activities, DOM fractions exhibited dose-dependent effects of MPs. The higher level of MPs (5% and 10%) tends to transform Pb into more bioavailable fractions in sediments. Also, MPs amendment was observed to alter sediment bacterial community structures, and community differences were evident in the uncontaminated and lead-contaminated sediments. Therein, significant increase of Bacteroidota, Proteobacteria and decrease of Firmicutes abundance in Pb-contaminated sediment at the phylum level were observed. These findings are expected to provide comprehensive information for assessing the combined ecological risks of heavy metals and MPs in riverine sediments.

Effects of microplastics on nitrogen and phosphorus cycles and microbial communities in sediments

Sediments are the long-term sinks of microplastics (MPs) and nutrients in freshwater ecosystems. Therefore, understanding the effect of MPs on sediment nutrients is crucial. However, few studies have discussed the effects of MPs on nitrogen and phosphorus cycles in freshwater sediments. Herein, 0.5% (w/w) polyvinyl chloride (PVC), polylactic acid (PLA), and polypropylene (PP) MPs were added to freshwater sediments to evaluate their effects on microbial communities and nitrogen and phosphorus release. The potential biochemical functions of the bacterial communities in the sediments were predicted and assessed via 16S rRNA gene sequencing. The results showed that MPs significantly affected the microbial community composition and nutrient cycling in the sediments. PVC and PP MPs can promote microbial nitrification and nitrite oxidation, while PP can significantly promote alkaline phosphatase (ALP) activity and the abundance of the phosphorus-regulation (phoR) gene. PLA MPs had the potential to promote the abundance of microbial phosphorus transporter (ugpB), nitrogen fixation (nifD, nifH, and nifX), and denitrification (nirS, napA, and norB) genes and inhibit nitrification, resulting in massive accumulation and release of ammonia nitrogen. Although PLA MPs inhibited the activity of ALP and the abundance of the organophosphorus mineralization (phoD) gene, it could enhance dissimilatory iron and sulfite reduction, which may promote the release of sedimentary phosphorus. Our findings may help understand the mechanisms of nitrogen and phosphorus cycles and microbial communities driven by MPs in sediments and provide a basis for future assessments of the environmental behavior of MPs in freshwater ecosystems.

Microplastics pollution in freshwater sediments: The pollution status assessment and sustainable management measures

Microplastics (MPs) pollution in freshwater sediments has brought hidden dangers to food and drinking water supply. Implementing sustainable management measures for MPs pollution in freshwater sediments has become an inevitable trend for sustainable development of society. Existing studies still lacked sufficient discussion in sustainable management of MPs pollution in freshwater sediments. This makes it difficult to formulate sustainable management measures for MPs pollution in freshwater sediments. This study analyzed the pollution status of MPs in freshwater sediments from 84 study areas. The results showed that current studies on MPs pollution in freshwater sediments were mainly concentrated in densely populated and economically developed areas. The average abundance of MPs in freshwater sediments from collected study areas was 1290.88 items/kg, this brought a potential threat to sustainable development in surrounding areas. The pollution load level and potential ecological risk level of MPs in freshwater sediments from these study areas were low. Reducing MPs discharge and restricting the use of high-risk polymers are effective ways to prevent the deterioration of MPs pollution status in freshwater sediments. The abundance and types of MPs in freshwater sediments from these study areas were affected by human activities. Sustainable management of MPs pollution in freshwater sediments from collected study areas requires establishing a lifecycle management system for plastic products, and the industrial structures should be optimized. In addition, legislation and market regulation are effective ways to restrict the discharge of plastic wastes. Sustainable management of MPs in freshwater sediments requires the synergy of legislation and market regulation.

Atmospheric microplastics and nanoplastics as vectors of primary air pollutants - A theoretical study on the polyethylene terephthalate (PET) case

Polyethylene terephthalate (PET) microplastics and nanoplastics are ubiquitously present in the atmosphere as atmospheric and airborne forms (PET-aMPs). Using first-principles calculations, we analyze the uptake of primary air pollutants onto PET-aMPs, focusing on their stabilities, adsorption mechanisms, and thermochemistry. The results show that PET-aMPs are selective for the spontaneous adsorption of CO, CO₂, NO, N₂O, NO₂, NH_3, and SO₂, reaching stable adsorption energies of 6-20 kcal/mol per molecule, with comparable uptake ability than carbon-based materials, metals/metalloids, and metal oxide surfaces. Then, PET-aMPs become a vector for coexisting air pollutants in the atmosphere, which adsorb by inner or outer adsorption depending on the molecular polarity (dipole moment) and atomic constitution (electronegativity) of gaseous molecules. Also, atmospheric H₂O and O₂ are not competitive molecules, and ozone could enhance adsorption due to surface oxidation and structure breakdown. The interplay of electrostatic (46-61%) and dispersion forces (21-58%) drives the adsorption mechanism, where low-polar pollutants display almost a balanced electrostatic vs. dispersion contribution, while high polar molecules display a higher electrostatic stabilization. The outer adsorption is reached by strong dispersion, hydrogen bonding, and dipole-dipole-induced pairs, while lone-pair-π interactions appear in the inner adsorption regime. These results expand the understanding of the hazards and risks of atmospheric and airborne microplastics/nanoplastics, their impacts, co-transport ability, and interaction with the environment.

The sustainable management of microplastics pollution in sediments from China: Promulgating relevant laws and implementing targeted management

Microplastics (MPs) pollution in sediments brings a huge challenge to the sustainable development of society. China is one of the countries with the largest production and application of plastic products in the world. The sustainable management of MPs pollution in sediments from China has important implications for achieving the United Nations Sustainable Development Goals. There is a lack of targeted management measures for the sustainable management of MPs pollution in sediments from China. In this study, 74 study areas were collected to analyze the pollution status of MPs in sediments from China. The results showed that the study on MPs pollution in sediments from China was concentrated in the Bohai Rim Economic Circle (n = 12), the Yangtze River Delta Economic Circle (n = 16) and the Pearl River Delta Economic Circle (n = 13). And the average abundance of MPs in sediments from China showed a decreasing trend from coastal to inland. Fiber had the highest centrality degree in the correlation network of MPs types. The reduction of fiber in sediments can reduce the diversity of MPs in sediments from China. Population density, economic level, urbanization level and industrial structure were significantly correlated with MPs types in sediments from China. The targeted management measures can be formulated based on the contribution of different human activities to MPs types. Managing pollution sources and cutting off transmission pathways are effective means for the targeted management of MPs in sediments. In addition, legislation can effectively restrict the application of plastic products. Promulgating relevant laws and implementing targeted management are conducive to the sustainable management of MPs pollution in sediments from China. In future studies, a big data platform for MPs pollution should be established to obtain a comprehensive understanding in the pollution status of MPs in sediments from China.

Dual regulatory effects of microplastics and heat waves on river microbial carbon metabolism

Rivers play a critical role in the global carbon cycle, but the processes can be affected by widespread microplastic (MP) pollution and the increasing frequency of heat waves (HWs) in a warming climate. However, little is known about the role of river microbes in regulating the carbon cycle under the combined action of MP pollution and HWs. Here, through seven-day MP exposure and three cycles of HW simulation experiments, we found that MPs inhibited the thermal adaptation of the microbial community, thus regulating carbon metabolism. The CO₂ release level increased, while the carbon degradation ability and the preference for stable carbon were inhibited. Metabonomic, 16 S rRNA and ITS gene analyses further revealed that the regulation of carbon metabolism was closely related to the microbial r-/K- strategy, community assembly and transformation of keystone taxa. The random forest model revealed that dissolved oxygen and ammonia-nitrogen were important variables influencing microbial carbon metabolism. The above findings regarding microbe-mediated carbon metabolism provide insights into the effect of climate-related HWs on the ecological risks of MPs.

Effects of polylactic acid (PLA) and polybutylene adipate-co-terephthalate (PBAT) biodegradable microplastics on the abundance and diversity of denitrifying and anammox bacteria in freshwater sediment

Microplastics (MPs) have been widely distributed on Earth and have drawn global concern for freshwater and marine ecosystems. Biodegradable plastics have risen in popularity to replace nonbiodegradable plastics all over the world. The effects of biodegradable plastics on denitrifying and anammox bacteria in freshwater sediment remain largely unknown. In this study, water column reactors containing polylactic acid (PLA) or polybutylene adipate-co-terephthalate (PBAT) MPs in sediment were established to simulate lake ecosystems and analyze the effects of biodegradable MPs on sedimentary nitrogen transformation microorganisms. The total organic carbon (TOC) concentrations in the PLA and PBAT groups were slightly higher than those in the control group, which might be related to the slow degradation of these two plastics. Denitrifying and anammox bacterial diversities decreased after adding MPs to sediments for 30 days, and the dominant OTUs of these two bacteria were differentiated from the control. The abundance levels of nirS denitrifying and anammox bacteria on the PLA MP surface were significantly higher than those in the other groups (P < 0.05), but they were lower in the PBAT groups than in the other groups. As an excellent electron donor for the denitrification process, lactic acid release from PLA degradation resulted in the enrichment of denitrifying and anammox bacteria on the MP surfaces. However, PBAT led to various responses of bacteria in an anaerobic environment. In addition, the redundancy analysis results indicated that total phosphorus, TOC and nitrate were strongly negatively correlated with the abundance levels of denitrifying and anammox bacteria. Our findings provided insight into the effects of MPs, especially the biodegradable ones, on sedimentary nitrogen-transformation bacteria.

The microbial community and functional indicators response to flow restoration in gradient in a simulated water flume

Flow reduction has greatly affected the river ecological systems, and it has attracted much attention. However, less attention has been paid to response to flow restoration, especially flow restoration in gradient. Flow regime of rivers may affect river functional indicators and microbial community structure. This study simulated the ecological restoration of the flow-reduced river reach by gradiently controlling the water flow and explores the ecological response of environmental functional indicators and microbial community structure to the water flow. The results showed that gross primary productivity (GPP), ecosystem respiration rate (ER) and some water quality indices such as chemical oxygen demand, total nitrogen, and total phosphorus (TP), exhibited positive ecological responses to flow restoration in gradient. GPP and ER increased by 600.1% and 500.2%, respectively. The alpha diversity indices of the microbial community increased significantly with a flow gradient restoration. Thereinto, Shannon, Simpson, Chao1, and Ace indices, respectively, increased by 16.4%, 5.6%, 8.6%, and 6.2%. Canonical correspondence analysis indicated that water flow, Dissolved oxygen and TP were the main influencing factors for changes in bacterial community structure. Microbial community structure and composition present a positive ecological response to flow restoration in gradient. This study reveals that the main variable in the restoration of the flow-reduced river reach is the flow discharge, and it provides a feasible scheme for its ecological restoration.