Investigating the composition and distribution of microplastics surface biofilms in coral areas

Microplastics increase the microbial functional potential of greenhouse gas emissions and water pollution in a freshwater lake: A metagenomic study

Aquatic ecosystems are being increasingly polluted by microplastics (MPs), which calls for an understanding of how MPs affect microbially driven biogenic element cycling in water environments. A 28-day incubation experiment was conducted using freshwater lake water added with three polymer types of MPs (i.e., polyethylene, polypropylene, polystyrene) separately or in combination at a concentration of 1 items/L. The effects of various MPs on microbial communities and functional genes related to carbon, nitrogen, phosphorus, and sulfur cycling were analyzed using metagenomics. Results showed that Sphingomonas and Novosphingobium, which were indicator taxa (genus level) in the polyethylene treatment group, made the largest functional contribution to biogenic element cycling. Following the addition of MPs, the relative abundances of genes related to methane oxidation (e.g., hdrD, frhB, accAB) and denitrification (napABC, nirK, norB) increased. These changes were accompanied by increased relative abundances of genes involved in organic phosphorus mineralization (e.g., phoAD) and sulfate reduction (cysHIJ), as well as decreased relative abundances of genes involved in phosphate transport (phnCDE) and the SOX system. Findings of this study underscore that MPs, especially polyethylene, increase the potential of greenhouse gas emissions (CO2, N2O) and water pollution (PO43-, H2S) in freshwater lakes at the functional gene level.

Colonization characteristics and surface effects of microplastic biofilms: Implications for environmental behavior of typical pollutants

This paper summarizes the colonization dynamics of biofilms on microplastics (MPs) surfaces in aquatic environments, encompassing bacterial characteristics, environmental factors affecting biofilm formation, and matrix types and characteristics. The interaction between biofilm and MPs was also discussed. Through summarizing recent literatures, it was found that MPs surfaces offer numerous benefits to microorganisms, including nutrient enrichment and enhanced resistance to environmental stress. Biofilm colonization changes the surface physical and chemical properties as well as the transport behavior of MPs. At the same time, biofilms also play an important role in the fragmentation and degradation of MPs. In addition, we also investigated the coexistence level, adsorption mechanism, enrichment, and transformation of MPs by environmental pollutants mediated by biofilms. Moreover, an interesting aspect about the colonization of biofilms was discussed. Biofilm colonization not only had a great effect on the accumulation of heavy metals by MPs, but also affects the interaction between particles and environmental pollutants, thereby changing their toxic effects and increasing the difficulty of MPs treatment. Consequently, further attention and research are warranted to delve into the internal mechanisms, environmental risks, and the control of the coexistence of MPs and biofilms.

Exploring the trophic transfer and effects of microplastics in freshwater ecosystems: A focus on Bellamya aeruginosa to Mylopharyngodon piceus

Microplastics (MPs) can enter aquatic food webs through direct ingestion from the environment or indirectly via trophic transfer, but their fate and biological effects within local freshwater food chains remain largely unexplored. In this study, we conducted the first investigation on the trophic transfer and impacts of fluorescently labeled polystyrene microplastics (PS-MPs) (100-nm and 10-μm) in a model freshwater food chain consisting of the snail Bellamya aeruginosa and the commercially important fish Mylopharyngodon piceus, both prevalent in Chinese freshwater ecosystems. Quantitative analysis revealed substantial accumulation of MPs in B. aeruginosa, reaching an equilibrium state within 12 h of exposure. While steady-state was not observed, a pronounced time-dependent bioaccumulation of MPs was evident in M. piceus over a five-week period following dietary exposure through the consumption of contaminated B. aeruginosa. Notably, MPs of both sizes underwent translocation from the gastrointestinal tract to the muscle tissue in M. piceus. High-throughput sequencing of the gut microbiota revealed that exposure to 100-nm MPs significantly altered the microbial community composition in M. piceus, and both particle sizes led to increased relative abundance of potentially pathogenic bacterial genera. Our findings provide novel insights into the trophic transfer, tissue accumulation, and biological impacts of MPs in a model freshwater food chain, highlighting the need for further research to assess the ecological and food safety risks associated with microplastic pollution in freshwater environments.

Exploring microbiome and plankton responses and interactions in the mangrove ecosystem through eDNA and network analysis

The comprehensive analysis of multiple biological communities is essential for assessing diversities within mangrove ecosystems, yet such studies are infrequent. Environmental DNA (eDNA) facilitates the simultaneous exploration of organisms across various levels within a single ecosystem. In this investigation, 16S rRNA, cytochrome C oxidase I (COI), and Mito-fish primers were employed to characterize the microbiome, eukaryotic plankton, and fish communities, along with their intricate interactions, across 24 samples from three Chinese mangrove reservoirs. The resulting dataset encompasses 3779 taxonomic groups (genus level), spanning from the microbiome to vertebrates. Diversity analysis unveiled a higher level of stability in the microbiome community compared to plankton, underscoring the superior site-specificity of plankton. The association analysis revealed that biodiversity was primarily affected by temperature, turbidity, and fluorescent dissolved organic matter (fDOM). Notably, the physicochemical factors, turbidity, and fDOM had a more pronounced impact on the microbiome than on plankton, explaining their distinct sensitivities to site-specific conditions. Network analysis constructed 15 biological interaction subnetworks representing various community connections. The most connected genera in each subnetwork, highly responsive to different environmental factors, could serve as potential indicators of distinct ecosystem states. In summary, our findings represent the first comparison of the response sensitivities of different communities and the construction of their interaction networks in mangrove environments. These results contribute valuable insights into marine ecosystem dynamics and the role of environmental factors in shaping biodiversity.

Prevalence and implications of microplastic contaminants in general human seminal fluid: A Raman spectroscopic study

Microplastics are ubiquitous environmental contaminants that have been detected in human semen from polluted areas, yet their prevalence and effects in the general population remain largely unexplored. To examine microplastic presence, abundance, polymer types, and associations with semen quality parameters in individuals without occupational exposures, this study was conducted by collecting semen samples from 40 participants undergoing premarital health assessments in Jinan, China. Raman microspectroscopy was employed to identify, quantify, and categorize microplastic polymers, sperm motility was assessed via computer-assisted analysis, and morphology was evaluated through Diff-Quik staining. Correlations between demographics, semen parameters, and microplastic content were examined by statistical analysis. We found that microplastics were detected in all semen samples, with 2 particles per sample (ranging from 0.72 to 7.02 μm). Eight distinct polymers were identified, with polystyrene (31 %) being most prevalent. Semen exposed to polystyrene demonstrated higher sperm progressive motility as compared to polyvinyl chloride exposure group (43.52 ± 14.21 % vs 19.04 ± 13.46 %). Sperm morphological abnormalities were observed but not significantly associated with specific plastic types. In conclusion, this study reveals microplastic contamination in semen from individuals without occupational exposure, with PS, PE, and PVC being the most prevalent and exhibiting differential correlations with sperm progressive motility, and highlight the need for further research into the potential reproductive impacts of microplastic exposure.

A platform for microplastic assessment in aquatic environments based on the protein corona-induced aggregation effect

The environmental hazards of microplastics have received widespread attention. However, the in-situ detection of microplastics, particularly in aquatic environments, has been challenged by the limitations of detection methods, the large-scale instruments, and small size. Herein, a photoelectrochemical sensor based on the protein corona-induced aggregation effect is designed for the detection of polystyrene microplastics. The sensor has advantages of high sensitivity, reproducibility, and detection capability. A linear detection range of 0.5-500 μg mL-1, a method detection limit of 0.06 μg mL-1, and a limit of quantification of 0.14 μg mL-1 are achieved. Furthermore, the relative standard deviations of intra-day and inter-day precision, ranging from 0.56% to 4.63% and 0.84%-3.36% are obtained. A digital multimeter was employed to construct a platform for the real-time detection in real water samples, streamlining the detection process and yielding clear results. We believe this sensor provides new insight for the in-situ real-time detection of microplastics and has broad applications for the analysis of microplastic pollution in aquatic environments.

Selective enrichment of bacteria and antibiotic resistance genes in microplastic biofilms and their potential hazards in coral reef ecosystems

Microplastics become hotspots for bacteria to trigger a series of ecological effects, but few studies have focused on the potential impacts of microplastic biofilms in coral reef ecosystems. Here, we measured the bacterial communities and antibiotic resistance genes (ARGs) in the seawater and microplastic biofilms. Results showed that microbial biofilms were formed on the surface of microplastics. The alpha diversity of the bacterial community in the microplastic biofilms was lower than that in the seawater, and the bacterial communities were distinct between the two. Further analysis revealed that several bacteria in the microplastic biofilms carried ARGs, and the proportion of which was correlated to the concentration of antibiotics in the seawater. Specifically, Vibrio was positively correlated to sul1 in the microplastic biofilms under higher concentrations of sulfonamides. Pathway analysis reflected significant overrepresentation of human disease related pathways in the bacterial community of microplastic biofilms. These results suggest that the microplastic biofilms could selectively enrich bacteria from the reef environments, causing the development of ARGs under antibiotic driving. This may pose a serious threat to coral reef ecosystems and human health. Our study provides new insights into the ecological impacts of microplastic biofilms in coral reef ecosystems.

Photodegradation of biodegradable plastics in aquatic environments: Current understanding and challenges

Direct and indirect photolysis are important abiotic processes in aquatic environments through which plastics can be transformed physically and chemically. Transport of biodegradable plastics in water is influenced by vertical mixing and turbulent flow, which make biodegradable plastics remain susceptible to sunlight and photolysis despite their high density. In general, biodegradable plastics are composed of ester containing polymers (e.g., poly(butylene succinate), polyhydroxyalkanoate, and polylactic acid), whereas non-biodegradable plastics are composed of long chains of saturated aliphatic hydrocarbons in their backbones (e.g., polyethylene, polypropylene, and polystyrene). Based on the reviewed knowledge and discussion, we may hypothesize that 1) direct photolysis is more pronounced for non-biodegradation than for biodegradable plastics, 2) smaller plastics such as micro/nano-plastics are more prone to photodegradation and photo-transformation by direct and indirect photolysis, 3) the production rate of reactive oxygen species (ROS) on the surface of biodegradable plastics is higher than that of non-biodegradable plastics, 4) the photodegradation of biodegradable plastics may be promoted by ROS produced from biodegradable plastics themselves, and 5) the subsequent reactions of ROS are more active on biodegradable plastics than non-biodegradable plastics. Moreover, micro/nanoplastics derived from biodegradable plastics serve as more effective carriers of organic pollutants than those from non-biodegradable plastics and thus biodegradable plastics may not necessarily be more ecofriendly than non-biodegradable plastics. However, biodegradable plastics have been largely unexplored from the viewpoint of direct or indirect photolysis. Roles of reactive oxygen species originating from biodegradable plastics should be further explored for comprehensively understanding the photodegradation of biodegradable plastics.

Effects of microplastics on microbial community dynamics in sediments from the Volturno River ecosystem, Italy

In this study, the sources, abundance, and ecological implications of microplastic (MP) pollution in Volturno, one of the main rivers in southern Italy, were explored by investigating the MP concentration levels in sediments collected along the watercourse. The samples were sieved through 5- and 2-mm sieves and treated with selective organic solvents. The polymer classes polystyrene (PS), polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polycarbonate (PC), nylon 6 (PA6), and nylon 6,6 (PA66) were quantified using pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) and high-performance liquid chromatography (HPLC). Furthermore, a 16S rRNA metagenomic analysis was performed using next-generation sequencing in Ion Torrent™ to explore the bacterial taxonomy and ecological dynamics of sediment samples. The MPs were detected in all samples collected from the study area. PP and PET were the most abundant and frequently detected polymer types in the analysed samples. The total MP concentration ranged from 1.05 to 14.55 ppm (parts per million), identifying two distinct data populations: high- and low-MP-contaminated sediments. According to the Polymer Hazard Index (PHI), MP pollution was categorised as hazard levels III and IV (corresponding to the danger category). Metagenomic data revealed that the presence of MPs significantly affected the abundance of bacterial taxa; Flavobacteraceae and Nocardiaceae, which are known to degrade polymeric substances, were present in high-MP-contaminated sediments. This study provides new insights into the ecological relevance of MP pollution and suggests that microorganisms may serve as biomarkers of MP pollution.

Exposure to pentachlorophenol destructs the symbiotic relationship between zooxanthellae and host and induces pathema in coral Porites lutea

Stress from chemical pollutants is among the key issues that have adverse impacts on coral reefs. As a persistent organic pollutant, pentachlorophenol (PCP) has been detected in the seawater of Weizhou Island and was proved to have significant adverse effects on aquatic animals. However, little is known about its effects on scleractinian coral. Therefore, we investigated the response of the coral Porites lutea to PCP stress. Coral bleaching, photosynthesis parameters and antioxidant enzyme activities of P. lutea under PCP exposure were documented. After 96 h of exposure, significant tissue loss and bleaching occurred when the PCP concentration exceeded 100 μg/L. The density of symbiotic zooxanthellae decreased from 2.06 × 106 cells/cm2 to 0.93 × 106 cells/cm2 when the PCP concentration increased from 1 μg/L- 1000 μg/L. Long-term exposure of 120 days to PCP at 0.1 μg/L also led to coral bleaching, the maximum photochemical quantum yield of PSII in P. lutea nubbins significantly decreased to 0.482. The analysis of microbial community distribution indicated that the increase of the pathogenic bacterium Citrobacter may be one of the inducers of coral bleaching. Conjoint analysis of transcriptomics and proteomics showed that the metabolism of amino acids and carbohydrates in zooxanthellae was abnormal, leading to the destruction of its symbiotic relationship with the host. The immune system of the host was disrupted, which could be linked to the prevalence of coral pathema. The toxic responses of PCP on both zooxanthellae and its host were further confirmed by the upregulation of the differential metabolites including 1-naphthylamine and phosphatidylcholine, etc.

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.

The effect of polystyrene nanoplastics on arsenic-induced apoptosis in HepG2 cells

Microplastics are detrimental to the environment. However, the combined effects of microplastics and arsenic (As) remain unclear. In this study, we investigated the combined effects of polystyrene (PS) microplastics and As on HepG2 cells. The results showed that PS microplastics 20, 50, 200, and 500 nm in size were taken up by HepG2 cells, causing a decrease in cellular mitochondrial membrane potential. The results of lactate dehydrogenase release and flow cytometry showed that PS microplastics, especially those of 50 nm, enhanced As-induced apoptosis. In addition, transcriptome analysis revealed that TP53, AKT1, CASP3, ACTB, BCL2L1, CASP8, XIAP, MCL1, NFKBIA, and CASP7 were the top 10 hub genes for PS that enhanced the role of As in HepG2 cell apoptosis. Our results suggest that nano-PS enhances As-induced apoptosis. Furthermore, this study is important for a better understanding of the role of microplastics in As-induced hepatotoxicity.

Surface functional groups and biofilm formation on microplastics: Environmental implications

Microplastics (MPs) contamination is becoming a significant environmental issue, as the widespread omnipresence of MPs can cause many adverse consequences for both ecological systems and humans. Contrary to what is commonly thought, the toxicity-inducing MPs are not the original pristine plastics; rather, they are completely transformed through various surface functional groups and aggressive biofilm formation on MPs via aging or weathering processes. Therefore, understanding the impacts of MPs' surface functional groups and biofilm formation on biogeochemical processes, such as environmental fate, transport, and toxicity, is crucial. In this review, we present a comprehensive summary of the distinctive impact that surface functional groups and biofilm formation of MPs have on their significant biogeochemical behavior in various environmental media, as well as their toxicity and biological effects. We place emphasis on the role of surface functional groups and biofilm formation as a means of influencing the biogeochemical processes of MPs. This includes their effects on pollutant fate and element cycling, which in turn impacts the aggregation, transport, and toxicity of MPs. Ultimately, future research studies and tactics are needed to improve our understanding of the biogeochemical processes that are influenced by the surface functional groups and biofilm formation of MPs.

Impacts of extracellular polymeric substances on the behaviors of micro/nanoplastics in the water environment

Increasing pollution of microplastics (MPs) and nanoplastics (NPs) has caused widespread concern worldwide. Extracellular polymeric substances (EPS) are natural organic polymers mainly produced by microorganisms, the major components of which are polysaccharides and proteins. This review focuses on the interactions that occur between EPS and MPs/NPs in the water environment and evaluates the effects of these interactions on the behaviors of MPs/NPs. EPS-driven formation of eco-corona, biofilm, and "marine snow" can incorporate MPs and NPs into sinking aggregates, resulting in the export of MPs/NPs from the upper water column. EPS coating greatly enhances the adsorption of metals and organic pollutants by MPs due to the larger specific surface area and the abundance of functional groups such as carboxyl, hydroxyl and amide groups. EPS can weaken the physical properties of MPs. Through the synergistic action of different extracellular enzymes, MPs may be decomposed into oligomers and monomers that can enter microbial cells for further mineralization. This review contributes to a comprehensive understanding of the dynamics of MPs and NPs in the water environment and the associated ecological risks.

Microplastics enrichment characteristics of antibiotic resistance genes and pathogens in landfill leachate

Microplastics (MPs) pollution is a pressing environmental issue for aquatic ecosystems. Landfill leachate is an important contributor of MPs and antibiotic resistant genes (ARGs). However, there are few studies on the colonization of ARGs and pathogens on MPs in leachate. This study conducted incubation experiments with polyethylene terephthalate (PET) and polypropylene (PP) MPs in landfill leachate which were about 3-5 years old (PL) and 5-10 years old (AL). After incubation, the bacterial cells colonized and grew on the surface of MPs, inducing the increase of oxygenated oxygen functional groups (e.g., hydroxyl, carbonyl) on the MPs surface. Real-time PCR indicated that MPs selectively enriched ARGs, such as genes tetM, tetC, mcr-1, aac(6')-Ib-cr, blaTEM and blaSHV in leachate. The diversity of bacterial communities on MPs was significantly increased in AL leachate, but decreased in PL leachate. The differences in bacterial communities in MPs biofilms were related to the type of MPs. Compared with AL leachate, the abundance of Chloroflexi increased by 15.7% on the PET, and the abundance of Acidobacteriota increased by 6.23 fold on the PP. The abundance of Firmicutes increased from 20.7% in PL leachate to 65.8% and 60.7% on PET and PP, respectively. Additionally, pathogens were observed to be more abundant on MPs compared to leachate. In particular, pathogens (Staphylococcus, Streptococcus, Enterobacter and Rhodococcus) associated with sul1 and sul2 were generally present at higher levels on MPs than in the surrounding leachate. These results provide significant implications for understanding the health risk of MPs in the environment.

The hidden risk of microplastic-associated pathogens in aquatic environments

Increasing studies of plastisphere have raised public concern about microplastics (MPs) as vectors for pathogens, especially in aquatic environments. However, the extent to which pathogens affect human health through MPs remains unclear, as controversies persist regarding the distinct pathogen colonization on MPs as well as the transmission routes and infection probability of MP-associated pathogens from water to humans. In this review, we critically discuss whether and how pathogens approach humans via MPs, shedding light on the potential health risks involved. Drawing on cutting-edge multidisciplinary research, we show that some MPs may facilitate the growth and long-range transmission of specific pathogens in aquatic environments, ultimately increasing the risk of infection in humans. We identify MP- and pathogen-rich settings, such as wastewater treatment plants, aquaculture farms, and swimming pools, as possible sites for human exposure to MP-associated pathogens. This review emphasizes the need for further research and targeted interventions to better understand and mitigate the potential health risks associated with MP-mediated pathogen transmission.

New insight into the effect of microplastics on antibiotic resistance and bacterial community of biofilm

Microplastics (MPs) could serve as substrates for microbial colonization and biofilm formation. However, research on the effects of different types of microplastics and natural substrates on biofilm formation and community structure in the presence of antibiotic-resistant bacteria (ARB) is limited. In this study, we employed by means of microcosm experiments to analyze the situation of biofilms conditions, bacterial resistance patterns, antibiotic resistance genes (ARGs) distribution, and bacterial community on different substrates using microbial cultivation, high throughtput sequencing and PCR. The result showed that biofilms on different substrates markedly increased with time, with MPs surfaces formed more biofilm than stone. Analyses of antibiotic resistant showed negligible differences in the resistance rate to the same antibiotic at 30 d, but tetB would be selectively enriched on PP and PET. The microbial communities associated with biofilms on MPs and stones exhibited variations during different stages of formation. Notably, phylum WPS-2 and Epsilonbacteraeota were identified as the dominant microbiomes of biofilms on MPs and stones at 30 d, respectively. Correlation analysis suggested that WPS-2 could potentially be a tetracycline-resistant bacterium, while Epsilonbacteraeota did not correlate with any detected ARB. Our results emphasized the potential threat posed by MPs as attachment carriers for bacteria, particularly ARB, in aquatic environments.

Microbiological Characterization of the Biofilms Colonizing Bioplastics in Natural Marine Conditions: A Comparison between PHBV and PLA

Biodegradable polymers offer a potential solution to marine pollution caused by plastic waste. The marine biofilms that formed on the surfaces of poly(lactide acid) (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were studied. Bioplastics were exposed for 6 months to marine conditions in the Mediterranean Sea, and the biofilms that formed on their surfaces were assessed. The presence of specific PLA and PHBV degraders was also studied. PHBV showed extensive areas with microbial accumulations and this led to higher microbial surface densities than PLA (4.75 vs. 5.16 log CFU/cm²). Both polymers' surfaces showed a wide variety of microbial structures, including bacteria, fungi, unicellular algae and choanoflagellates. A high bacterial diversity was observed, with differences between the two polymers, particularly at the phylum level, with over 70% of bacteria affiliated to three phyla. Differences in metagenome functions were also detected, revealing a higher presence of proteins involved in PHBV biodegradation in PHBV biofilms. Four bacterial isolates belonging to the Proteobacteria class were identified as PHBV degraders, demonstrating the presence of species involved in the biodegradation of this polymer in seawater. No PLA degraders were detected, confirming its low biodegradability in marine environments. This was a pilot study to establish a baseline for further studies aimed at comprehending the marine biodegradation of biopolymers.

Biomass formation and organic carbon migration potential of microplastics from a PET recycling plant: Implication of biostability

The growth of the polyethylene terephthalate (PET) mechanical recycling industry has resulted in the challenge of generating microplastics (MPs). However, little attention has been given to investigating the release of organic carbon from these MPs and their roles in promoting bacterial growth in aquatic environments. In this study, a comprehensive method is proposed to access the potential of organic carbon migration and biomass formation of MPs generated from a PET recycling plant, and to understand its impact on the biological systems of freshwater habitats. Various MPs sizes from a PET recycling plant were selected to conduct a series of tests, including the organic carbon migration test, biomass formation potential test, and microbial community analysis. The MPs smaller than 100 µm, which are difficult to remove from the wastewater, exhibited greater biomass in the observed samples (1.05 × 10¹¹ bacteria per gram MPs). Moreover, PET MPs altered the microbial diversity, with Burkholderiaceae becoming the most abundant, while Rhodobacteraceae was eliminated after being incubated with MPs. This study partly revealed that organic matter adsorbed on the surface of MPs was a significant nutrient source that increased biomass formation. PET MPs acted not only as carriers for microorganisms but also for organic matter. As a result, it is crucial to develop and refine recycling methods in order to decrease the production of PET MPs and minimize their adverse effects on the environment.

Plastic wastes and surface antibiotic resistance genes pollution in mangrove environments

Mangroves are located at the intersection of land and sea and are also heavily affected by plastic wastes. Biofilms of plastic wastes in mangroves are reservoirs for antibiotic resistance genes (ARGs). In this study, plastic wastes and ARG pollution were investigated from three typical mangrove areas in Zhanjiang, South China. Transparent was the dominant colors of plastic wastes in three mangroves. Fragment and film shape accounted for 57.73-88.23% of plastic waste samples in mangroves. In addition, 39.50% of plastic wastes in protected area mangroves are PS. The metagenomic results shows that the 175 ARGs were found on plastic wastes of the three mangroves, the abundance accounting for 91.11% of the total ARGs. The abundance of Vibrio accounted for 2.31% of the total bacteria genera in aquaculture pond area mangrove. Correlation analysis shows that a microbe can carry multiple ARGs that may improve resistance to antibiotics. Microbes are the potential hosts of most ARGs, suggesting that ARGs can be transmitted by microbes. Because the mangroves are closely related to human activities and the high abundance of ARGs on plastic increases the ecological risks, people should improve plastic waste management and prevent the spread of ARGs by reducing plastic pollution.

Plastisphere microbiome: Methodology, diversity, and functionality

Broad topics of the plastisphere in various environments are reviewed, including its methodologies, diversity, functionality, and outlook.

Microplastic as an invisible threat to the coral reefs: Sources, toxicity mechanisms, policy intervention, and the way forward

Microplastic (MP) pollution waste is a global macro problem, and research on MP contamination has been done in marine, freshwater, and terrestrial ecosystems. Preventing MP pollution from hurting them is essential to maintaining coral reefs' ecological and economic benefits. However, the public and scientific communities must pay more attention to MP research on the coral reef regions' distribution, effects, mechanisms, and policy evaluations. Therefore, this review summarizes the global MP distribution and source within the coral reefs. Current knowledge extends the impacts of MP on coral reefs, existing policy, and further recommendations to mitigate MPs contamination on corals are critically analyzed. Furthermore, mechanisms of MP on coral and human health are also highlighted to pinpoint research gaps and potential future studies. Given the escalating plastic usage and the prevalence of coral bleaching globally, there is a pressing need to prioritize research efforts on marine MPs that concentrate on critical coral reef areas. Such investigations should encompass an extensive and crucial understanding of the distribution, destiny, and effects of the MPs on human and coral health and the potential hazards of those MPs from an ecological viewpoint.

Distribution and risk assessment of microplastics in typical ecosystems in the South China Sea

Microplastic pollution in the marine environment has attracted worldwide attention. The South China Sea is considered a hotspot for microplastic pollution due to the developed industries and high population density around the South China Sea. The accumulation of microplastics in ecosystems can adversely affect the health of the environment and organisms. This paper reviews the recent microplastic studies conducted in the South China Sea, which novelty summarizes the abundance, types, and potential hazards of microplastics in coral reef ecosystems, mangrove ecosystems, seagrass bed ecosystems, and macroalgal ecosystems. A summary of the microplastic pollution status of four ecosystems and a risk assessment provides a more comprehensive understanding of the impact of microplastic pollution on marine ecosystems in the South China Sea. Microplastic abundances of up to 45,200 items/m³ were reported in coral reef surface waters, 5738.3 items/kg in mangrove sediments, and 927.3 items/kg in seagrass bed sediments. There are few studies of microplastics in the South China Sea macroalgae ecosystems. However, studies from other areas indicate that macroalgae can accumulate microplastics and are more likely to enter the food chain or be consumed by humans. Finally, this paper compared the current risk levels of microplastics in the coral reef, mangrove, and seagrass bed ecosystems based on available studies. Pollution load index (PLI) ranges from 3 to 31 in mangrove ecosystems, 5.7 to 11.9 in seagrass bed ecosystems, and 6.1 to 10.2 in coral reef ecosystems, respectively. The PLI index varies considerably between mangroves depending on the intensity of anthropogenic activity around the mangrove. Further studies on seagrass beds and macroalgal ecosystems are required to extend our understanding of microplastic pollution in marine environments. Recent microplastic detection in fish muscle tissue in mangroves requires more research to further the biological impact of microplastic ingestion and the potential food safety risks.

Impacts of marine debris on coral reef ecosystem: A review for conservation and ecological monitoring of the coral reef ecosystem

Coral reefs are the most spectacular underwater creation of nature. It enhances ecosystem functioning and marine biodiversity while also ensuring the livelihood of millions of coastal communities worldwide. Unfortunately, marine debris poses a serious threat to ecologically sensitive reef habitats and their associated organisms. Over the past decade, marine debris has been regarded as a major anthropogenic threat to marine ecosystems and gained scientific attention around the globe. However, the sources, types, abundance, distribution, and potential consequences of marine debris on reef ecosystems are hardly known. The goal of this review is to provide an overview of the current status of marine debris in various reef ecosystems across the world, with special emphasis on its sources, abundance, distribution, species impacted, major categories, potential impacts and management strategies. Furthermore, the adhesion mechanisms of microplastics to coral polyps, diseases caused by microplastics and are also highlighted.

Macro- and microplastics as complex threats to coral reef ecosystems

The impacts of macroplastics (macro-), microplastics (MPs, <5mm), and nanoplastics (NPs, <100 nm) on corals and their complex reef ecosystems are receiving increased attention and visibility. MPs represent a major, contemporary, sustainability challenge with known and unknown effects on the ocean, and coral reef ecosystems worldwide. However, the fate and transport processes of macro-, MPs, and NPs and their direct and indirect impacts on coral reef ecosystems remains poorly understood. In this study, we verify and briefly summarize MPs distribution and pollution patterns in coral reefs from various geographical regions and discuss potential risks. The main interaction mechanisms show that MPs may substantially affect coral feeding performance, proper skeletal formation, and overall nutrition and, thus, there is an urgent need to address this rapidly growing environmental problem. From a management perspective, macro-, MPs, and NPs should, ideally, all be included in environmental monitoring frameworks, as possible, to aid in identifying those geographical areas that are most heavily impacted and to support future prioritization of conservation efforts. The potential solutions to the macro-, MP, and NP pollution problem include raising public awareness of plastic pollution, developing robust, environmental, conservation efforts, promoting a circular economy, and propelling industry-supported technological innovations to reduce plastic use and consumption. Global actions to curb plastic inputs, and releases of macro-, MP, and NP particles, and their associated chemicals, to the environment are desperately needed to secure the overall health of coral reef ecosystems and their inhabitants. Global scale horizon scans, gap analyses, and other future actions are necessary to gain and increase momentum to properly address this massive environmental problem and are in good accordance with several relevant UN sustainable development goals to sustain planetary health.

Bioremediation of microplastics in freshwater environments: A systematic review of biofilm culture, degradation mechanisms, and analytical methods

Microplastics, defined as particles <5 mm in diameter, are emerging environmental pollutants that pose a threat to ecosystems and human health. Biofilm degradation of microplastics may be an ecologically friendly approach. This review systematically summarises the factors affecting biofilm degradation of microplastics and proposes feasible methods to improve the efficiency of microplastic biofilm degradation. Environmentally insensitive microorganisms were screened, optimized, and commercially cultured to facilitate the practical application of this technology. For strain screening, technology should focus on microorganisms/strains that can modify the hydrophobicity of microplastics, degrade the crystalline zone of microplastics, and metabolise additives in microplastics. The biodegradation mechanism is also described; microorganisms secreting extracellular oxidases and hydrolases are key factors for degradation. Measuring the changes in molecular weight distribution (MWD) enables better analysis of the biodegradation behaviour of microplastics. Biofilm degradation of microplastics has relatively few applications because of its low efficiency; however, enrichment of microplastics in freshwater environments and wastewater treatment plant tailwater is currently the most effective method for treating microplastics with biofilms.

Mangrove degradation retarded microplastics weathering and affected metabolic activities of microplastics-associated microbes

Currently, information on microplastics (MPs) weathering characteristics and ecological functions driven by MPs-associated microbes in mangrove ecosystems remains unclear, especially in the degraded areas. Herein, we compared the weathering characteristics of MPs in both undegraded and degraded mangrove sediments, and then explored the potential interactions between their weathering characteristics and microbially-driven functions. After 70 days of incubation, different MPs (including polyethylene PE, polystyrene PS, and polylactic acid PLA) were strongly weathered in mangrove sediments, with significant erosion features. Interestingly, more obvious weathering characteristics were found for MPs in the undegraded mangrove sediments. O/C ratio value of MPs in the undegraded sediments was 2.3-3.0 times greater than that in the degraded ones. Besides, mangrove degradation reduced network complexity among MPs-associated microorganisms and affected their metabolic activities. Bacteria involved in carbon cycle process enriched on nondegradable MPs, whereas abundant bacteria responsible for sulphur cycle were observed on PLA-MPs. Moreover, these relevant bacteria were more abundant on MPs in the undegraded mangrove sediments. Mangrove degradation could directly and indirectly affect MPs weathering process and microbially-driven functions through regulating sediment properties and MPs-associated microbes. During weathering, contact angle and roughness of MPs were key factors influencing the colonisation of hydrocarbon degradation bacteria on MPs.

Identification of quorum sensing-regulated Vibrio fortis as potential pathogenic bacteria for coral bleaching and the effects on the microbial shift

Coastal pollution, global warming, ocean acidification, and other reasons lead to the imbalance of the coral reef ecosystem, resulting in the increasingly serious problem of coral degradation. Coral bleaching is often accompanied by structural abnormalities of coral symbiotic microbiota, among which Vibrio is highly concerned. In this study, Vibrio fortis S10-1 (MCCC 1H00104), isolated from sea cucumber, was used for the bacterial infection on coral Seriatopora guttatus and Pocillopora damicornis. The infection of S10-1 led to coral bleaching and a significant reduction of photosynthetic function in coral holobiont, and the pathogenicity of V. fortis was regulated by quorum sensing. Meanwhile, Vibrio infection also caused a shift of coral symbiotic microbial community, with significantly increased abundant Proteobacteria and Actinobacteria and significantly reduced abundant Firmicutes; on genus level, the abundance of Bacillus decreased significantly and the abundance of Rhodococcus, Ralstonia, and Burkholderia-Caballeronia-Paraburkholderia increased significantly; S10-1 infection also significantly impacted the water quality in the micro-ecosystem. In contrast, S10-1 infection showed less effect on the microbial community of the live stone, which reflected that the microbes in the epiphytic environment of the live stone might have a stronger ability of self-regulation; the algal symbionts mainly consisted of Cladocopium sp. and showed no significant effect by the Vibrio infection. This study verified that V. fortis is the primary pathogenic bacterium causing coral bleaching, revealed changes in the microbial community caused by its infection, provided strong evidence for the "bacterial bleaching" hypothesis, and provided an experimental experience for the exploration of the interaction mechanism among microbial communities, especially coral-associated Vibrio in the coral ecosystem, and potential probiotic strategy or QS regulation on further coral disease control.

From marine to freshwater environment: A review of the ecotoxicological effects of microplastics

Microplastics (MPs) have been widely detected in the world's water, which may pose a significant threat to the ecosystem as a whole and have been a subject of much attention because their presence impacts seas, lakes, rivers, and even the Polar Regions. There have been numerous studies that report direct adverse effects on marine organisms, but only a few have explored their ecological effects on freshwater organisms. In this field, there is still a lack of a systematic overview of the toxic effects and mechanisms of MPs on aquatic organisms, as well as a consistent understanding of the potential ecological consequences. This review describes the fate and impact on marine and freshwater aquatic organisms. Further, we examine the toxicology of MPs in order to uncover the relationship between aquatic organism responses to MPs and ecological disorders. In addition, an overview of the factors that may affect the toxicity effects of MPs on aquatic organisms was presented along with a brief examination of their identification and characterization. MPs were discussed in terms of their physicochemical properties in relation to their toxicological concerns regarding their bioavailability and environmental impact. This paper focuses on the progress of the toxicological studies of MPs on aquatic organisms (bacteria, algae, Daphnia, and fish, etc.) of different trophic levels, and explores its toxic mechanism, such as behavioral alternations, metabolism disorders, immune response, and poses a threat to the composition and stability of the ecosystem. We also review the main factors affecting the toxicity of MPs to aquatic organisms, including direct factors (polymer types, sizes, shapes, surface chemistry, etc.) and indirect factors (persistent organic pollutants, heavy metal ions, additives, and monomer, etc.), and the future research trends of MPs ecotoxicology are also pointed out. The findings of this study will be helpful in guiding future marine and freshwater rubbish studies and management strategies.

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.

Is there a significant difference in microbiota between water and microplastic surfaces in winter? The possibility of spreading offshore into the ocean

Environmental problems caused by microplastics (MPs) are attracting global attention. The ecological risks of bacteria attached to MPs have not been studied in detail under low temperature conditions. Here, MPs in surface water were sampled in winter from the Changjiang (or Yangtze) River Estuary. The physical and chemical characteristics of the MPs were identified, and the diversity and species composition of bacteria on the surface water MPs were analyzed. Phenotypic prediction analysis was used to analyze the potential risk of bacteria in the biofilm on the surfaces of MPs. The main chemical composition in the MPs in the surface water were PP (polypropylene), PE (polyethylene), PS (polystyrene) and other light weight MPs. Sampling sites played a decisive role in the bacterial species composition. The potential plastic-degrading bacterium Acinetobacter and the potential pathogenic bacterium Pseudomonas showed significant differences across different sampling sites. Microbial communities on the surfaces of MPs in winter were not significantly different from planktonic bacteria in the water body. Phenotypic prediction results showed that bacteria on the surface of MPs had a marked capacity to form biofilms, but a low pathogenicity risk. Based on the results of biodiversity analysis and phenotypic prediction, the potential ecological risk of bacteria in biofilms on MP surfaces is lower at low temperatures. In addition, the numerical simulation results show that the possibility of bacteria attached to MPs from the Changjiang River entering the Pacific Ocean in winter is small. MPs attached bacteria in the Changjiang estuary have low ecological risk to the estuary and the Pacific Ocean in winter.

Effects of the Desiccation Duration on the Dynamic Responses of Biofilm Metabolic Activities to Rewetting

Global climate changes have increased the duration and frequency of river flow interruption, affecting the physical and community structure of benthic biofilms. However, the dynamic responses of biofilm metabolism during the dry-wet transition remain poorly understood. Herein, the dynamic changes in biofilm metabolic activities were investigated through mesocosm experiments under short-term (25 day) and long-term drought (90 day), followed by a 20 day rewetting. The biofilm ecosystem metabolism, as measured by gross primary production and community respiration, was significantly inhibited and turned heterotrophic during the desiccation phase and then recovered, becoming autotrophic during the rewetting period regardless of the desiccation periods due to the high resilience of the autotrophic community. However, long-term drought decreased the recovery rate of the ecosystem metabolism and also caused irreparable damage to the biofilm carbon metabolism, measured using Biolog Eco Plates. Specifically, the recovery of the total carbon metabolic activity is related to the specific carbon source utilized by biofilm microorganisms, such as polymers, carbohydrates, and carboxylic acids. However, the divergent changes of amino acids caused the failure of the total carbon metabolism in long-term drought treatments to recover to the control level even after 20 days of rewetting. This research provides direct evidence that the increased duration of non-flow periods affects biofilm-mediated carbon biogeochemical processes.

Biodegradation of polystyrene (PS) by marine bacteria in mangrove ecosystem

Plastics pollution poses a new threat to marine ecosystems. Mangrove locating at estuary worldwide is probably the most heavily polluted area trapping various plastics transported from terrestrial and nearby marine aquaculture. Expanded polystyrene (EPS) is one of most common plastic debris therein and even in the plastic garbage. Here we showed the bacterial diversity of the polystyrene-degrading microbial community from EPS waste sites from a subtropical mangrove area. After enrichment with EPS, the degradation consortia were obtained. They shared a similar community structure dominated by bacteria of Sphingomonadaceae, Rhodanobacteraceae, Rhizobiaceae, Dermacoccaceae, Rhodocyclaceae, Hyphomicrobiaceae, and Methyloligellaceae. Diverse bacteria standing for the first member of the genera of Novosphingobium, Gordonia, Stappia, Mesobacillus, Alcanivorax, Flexivirga, Cytobacillus, Thioclava, and Thalassospira showed PS degradation capability as a pure culture. Further, PS biodegradation of Gordonia sp. and Novosphingobium sp. was quantified by weight loss, in addition to obvious morphological and structural changes of the PS films observed by SEM, ATR-FTIR, and contact angle analysis. The formation of new oxygen-containing functional groups implied the degradation pathway of oxidation. Although the degradation rates ranged from 2.7% to 7.7% after one month in lab and possibly lower in situ, their role in EPS removal is unneglectable.

A review on enhanced microplastics derived from biomedical waste during the COVID-19 pandemic with its toxicity, health risks, and biomarkers

The COVID-19 pandemic led to the explosion of biomedical waste, a global challenge to public health and the environment. Biomedical waste comprising plastic can convert into microplastics (MPs, < 5 mm) by sunlight, wave, oxidative and thermal processes, and biodegradation. MPs with additives and contaminants such as metals are also hazardous to many aquatic and terrestrial organisms, including humans. Bioaccumulation of MPs in organisms often transfers across the trophic level in the global food web. Thus, this article aims to provide a literature review on the source, quantity, and fate of biomedical waste, along with the recent surge of MPs and their adverse impact on aquatic and terrestrial organisms. MPs intake (ingestion, inhalation, and dermal contact) in humans causing various chronic diseases involving multiple organs in digestive, respiratory, and reproductive systems are surveyed, which have been reviewed barely. There is an urgent need to control and manage biomedical waste to shrink MPs pollution for reducing environmental and human health risks.

Impacts of hydraulic conditions on microplastics biofilm development, shear stresses distribution, and microbial community structures in drinking water distribution pipes

Both microplastic and biofilm are contamination sources in drinking water, but their integrated impacts on water quality have been rarely studied, especially in drinking water distribution pipes with complex hydraulic conditions. This study explored the impacts of hydraulic conditions (0-2 m/s) on microplastic biofilm (MP-BM) development, shear stresses distribution, and microbial community structures. The research was conducted for two weeks using a pilot test device to simulate practical water pipes. The following were the primary conclusions: (1) According to morphology analysis, clusters (>5 μm) significantly increased in the plastisphere when the flow velocity ranged from 0.55 m/s to 0.95 m/s, and average size of clusters decreased when the flow velocity ranged from 1.14 m/s to 1.40 m/s (2) Characteristics of MP-BM impact shear stress on both plastisphere and pipe wall biofilm. Shear stresses were positively correlated with flow velocity, number of MP-BM, and size of MP-BM, while negatively correlated with diameters of pipes. (3) 31 genera changed strictly and monotonously with the fluid velocity, accounting for 15.42%. Opportunistic pathogens in MP-BM such as Sediminibacterium, Curvibacter, and Flavobacterium were more sensitive to hydraulic conditions. Moreover, microplastics (<100 μm) deserve more attention to avoid human ingestion and to prevent mechanical damage and bio-chemical risks.

Ecotoxicological and health implications of microplastic-associated biofilms: a recent review and prospect for turning the hazards into benefits

Microplastics (MPs), over the years, have been regarded as a severe environmental nuisance with adverse effects on our ecosystem as well as human health globally. In recent times, microplastics have been reported to support biofouling by genetically diverse organisms resulting in the formation of biofilms. Biofilms, however, could result in changes in the physicochemical properties of microplastics, such as their buoyancy and roughness. Many scholars perceived the microplastic-biofilm association as having more severe consequences, providing evidence of its effects on the environment, aquatic life, and nutrient cycles. Furthermore, other researchers have shown that microplastic-associated biofilms have severe consequences on human health as they serve as vectors of heavy metals, toxic chemicals, and antibiotic resistance genes. Despite what is already known about their adverse effects, other interesting avenues are yet to be fully explored or developed to turn the perceived negative microplastic-biofilm association to our advantage. The major inclusion criteria for relevant literature were that it must focus on microplastic association biofilms, while we excluded papers solely on biofilms or microplastics. A total of 242 scientific records were obtained. More than 90% focused on explaining the environmental and health impacts of microplastic-biofilm association, whereas only very few studies have reported the possibilities and opportunities in turning the microplastic biofilms association into benefits. In summary, this paper concisely reviews the current knowledge of microplastic-associated biofilms and their adverse consequences and further proposes some approaches that can be developed to turn the negative association into positive.

Marine litter and climate change: Inextricably connected threats to the world's oceans

The global issues of climate change and marine litter are interlinked and understanding these connections is key to managing their combined risks to marine biodiversity and ultimately society. For example, fossil fuel-based plastics cause direct emissions of greenhouse gases and therefore are an important contributing factor to climate change, while other impacts of plastics can manifest as alterations in key species and habitats in coastal and marine environments. Marine litter is acknowledged as a threat multiplier that acts with other stressors such as climate change to cause far greater damage than if they occurred in isolation. On the other hand, while climate change can lead to increased inputs of litter into the marine environment, the presence of marine litter can also undermine the climate resilience of marine ecosystems. There is increasing evidence that that climate change and marine litter are inextricably linked, although these interactions and the resulting effects vary widely across oceanic regions and depend on the particular characteristics of specific marine environments. Ecosystem resilience approaches, that integrate climate change with other local stressors, offer a suitable framework to incorporate the consideration of marine litter where that is deemed to be a risk, and to steer, coordinate and prioritise research and monitoring, as well as management, policy, planning and action to effectively tackle the combined risks and impacts from climate change and marine litter.

Impact of the surrounding environment on antibiotic resistance genes carried by microplastics in mangroves

The pollution of antibiotic resistance genes (ARGs) carried by microplastics (MPs) is a growing concern. Mangroves are located at the intersection of land and sea and are seriously affected by MP pollution. However, few studies have systematic research evaluating the transmission risk of ARGs carried by MPs in mangroves. We conducted in situ experiments by burying five different MPs (polypropylene, high-density polyethylene, polystyrene, polyethylene glycol terephthalate, and polycaprolactone particles) in mangroves with different surrounding environments. A total of 10 genes in the MPs of mangroves were detected using quantitative real-time polymerase chain reactions, including eight ARGs and two mobile genetic elements (MGEs). The abundance of ARGs in Guanhai park mangroves in living areas (GH) was higher than that of Gaoqiao mangroves in protected areas (GQ) and Beiyue dike mangroves in aquaculture pond areas (BY). Pathogenic bacteria, such as Acinetobacter, Bacillus, and Vibrio were found on the MP surfaces of the mangroves. The number of ARGs carried by multiple drug-resistant bacteria in the GH mangroves was greater than that in the GQ and BY mangroves. Moreover, the ARGs carried by MPs in GH mangroves had the highest potential transmission risk by horizontal gene transfer. Sociometric and environmental factors were the main drivers shaping the distribution characteristics of ARGs and MGEs. Polypropylene and high-density polyethylene particles are preferred substrates for obtaining diffuse ARGs. This study investigated the drivers of ARGs in the MPs of mangroves and provided essential guidance on the use and handling of plastics.

Ecological responses of coral reef to polyethylene microplastics in community structure and extracellular polymeric substances

The relationships and interactions between extracellular polymeric substances (EPS) and microplastics (MPs) in coral reef ecosystems were symmetrically investigated. The current study aims to investigate the responses of scleractinian coral (Goniopora columna) to exposure of model MPs, exemplified by polyethylene (PE), in the size range of 40-48 μm as affected by MPs concentration of MP in the range between 0 and 300 mg L^-1 for 14 days. The structure of EPS-associated microbial community was studied using a series of techniques including high-throughput sequencing of 16 S rRNA, transmission electron microscopy (TEM), hydrodynamic diameter, surface charge (via zeta potential), X-ray diffraction (XRD), attenuated total reflectance‒Fourier transform infrared (ATR‒FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and fluorescence excitation-emission matrix (FEEM) spectroscopy. Microbial interactions between PE-MPs and coral caused aggregation and formation of EPS matrix, which resulted in increase and decrease in the relative abundance of Donghicola (Proteobacteria phylum) and Marivita (Proteobacteria phylum) in PE-MP-associated EPS, respectively. Particle size, electrostatic interactions, and complexation with the functional groups of the EPS-based matrix affected the humification index. FEEM spectroscopy analyses suggested the presence of humic- and fulvic-like fluorophores in EPS and dissolved organic matter (DOM) in PE-MP-derived DOM. The findings provided insights into the potential environmental implications of coral-based EPS and co-existing microbial assemblages due to EPS-PE-MP-microbiome interactions throughout the dynamic PE-MP exposure process.

Microplastics act as a carrier for wastewater-borne pathogenic bacteria in sewage

Microplastic pollution, a pressing global environmental problem, has a severe impact on both aquatic ecosystems and public health worldwide. Due to the small size of microplastics, they are able to pass through the filtration systems of municipal wastewater treatment works (WWTWs). In recent years, studies have focused on the environmental abundance and ecotoxicological effects of microplastics, but there are limited studies investigating the colonization of microplastics by bacteria, especially those pathogenic ones. In this study, we examined the colonization and composition of the bacterial communities on polyethylene microbeads after incubation in raw sewage collected from three municipal WWTWs in Hong Kong (Sha Tin Sewage Treatment Works, Stonecutters Island Sewage Treatment Works, and Shek Wu Hui Sewage Treatment Works). Scanning electron microscopy (SEM) results indicate that bacterial cells were colonized on the surfaces of the microbeads and formed biofilms after sewage incubation. Metagenomic sequencing data demonstrated an increase in bacterial diversity after 21 days of sewage incubation when compared to shorter incubation periods of 6, 11 and 16 days. Importantly, human and fish pathogens such as Arcobacter cryaerophilus, Aeromonas salmonicida, Vibrio areninigrae and Vibrio navarrensis were found in the resident bacterial communities. Taken together, our results demonstrate that microplastics could act as a carrier for wastewater-borne pathogenic bacteria in municipal sewage.

Concentrations and risk assessment of metals and microplastics from antifouling paint particles in the coastal sediment of a marina in Simon's Town, South Africa

Maintenance of maritime vessels includes the removal of paint from hulls that are sources of metals, antifouling paint particles (APPs) and microplastics (MPs) that end up in the coastal environment. Simon's Town is a small urban town in False Bay, Cape Town, South Africa, where maritime activities take place (there is a naval harbour, marina and shipyard). The aim of this study was to measure metals, APPs and MPs in Simon's Town, to assess the impact of maritime activities and a storm water pipe in a sheltered marina. Sediment samples were collected from six sites during winter 2018. Sediment and extracted APPs were analysed for metal concentrations (Al, As, B, Ba, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, Se, Sb, Sn, Sr, V and Zn) and MPs characterised based on type (shape and polymer), colour and size. Highest average metal concentrations in sediment for all sites were Fe (32228 ± SEM 4024), Al (12271 ± 1062) and Cu (1129 ± 407). Metals in paint particles were highest for Fe (80873 ± 19341), Cu (66762 ± 13082) and Zn (44910 ± 1400 µg/g). Metal and MP fragment concentrations were highest at the slipway of the shipyard, decreasing with increased distance from the slipway. MP filaments were highest close to the storm water outfall pipe. Our results suggest that shipyards are potential sources of metals and MP fragments (mainly APPs), with storm water pipes potential sources of MP filaments. Various indices applied to assess the potential impacts of metals and MPs suggest that these contaminants have the potential to adversely impact the intertidal ecosystem investigated.

Interactive impacts of microplastics and chlorine on biological stability and microbial community formation in stagnant water

Possibility of human exposure to microplastics (MPs) in water environment has been escalating, and subsequent challenges of MPs to biostability and biosafety in drinking water deserve more attention, especially in stagnant water. The present study explored the integrated impacts of MPs and chlorine on disinfection kinetics, microbial growth, and microbial community formation in drinking water, by setting MPs or microplastic-biofilm (MP-BM) under different disinfection conditions. The following were the primary conclusions: (1) The presence of MP and MP-BM led to the deterioration of water indices (especially turbidity) when chlorine was less than 1 mg/L. (2) MP/MP-BM accelerated the decay of disinfectants and MP-BM consumed more rapidly. Meanwhile, chlorine contributed to the level of BRP, ranging from 4.78 × 10⁵ CFU/mL to 1.42 × 10⁷ CFU/mL. (3) MP/MP-BM and chlorine integrally shaped microbial communities in water samples and biofilm samples. Microbial dissimilarity between isolated and hybrid MP-BM indicated manners of microbial field or non-contact communication. Microbial abundance and OPs were effectively controlled when chlorine was over 1 mg/L. (4) According to time-lag differential equations simulation, impulsive chlorination contributed to controlling microbial risks and DBPs induced by MP/MP-BM and water stagnation.

Seasonal heterogeneity and a link to precipitation in the release of microplastic during COVID-19 outbreak from the Greater Jakarta area to Jakarta Bay, Indonesia

To reduce microplastic contamination in the environment, we need to better understand its sources and transit, especially from land to sea. This study examines microplastic contamination in Jakarta's nine river outlets. Microplastics were found in all sampling intervals and areas, ranging from 4.29 to 23.49 particles m^-3. The trend of microplastic contamination tends to increase as the anthropogenic activity towards Jakarta Bay from the eastern side of the bay. Our study found a link between rainfall and the abundance of microplastic particles in all river outlets studied. This investigation found polyethylene, polystyrene, and polypropylene in large proportion due to their widespread use in normal daily life and industrial applications. Our research observed an increase in microplastic fibers made of polypropylene over time. We suspect a relationship between COVID-19 PPE waste and microplastic shift in our study area. More research is needed to establish how and where microplastics enter rivers.

Microplastics a Novel Substratum for Polyhydroxyalkanoate (PHA)-Producing Bacteria in Aquatic Environments

Polyhydroxyalkanoates (PHA) being biological polymers have attracted great attention. PHA have similar properties to that of synthetic plastic and are biodegradable. To discourage plastic pollution in the environment alternative solutions to the plastic pollution has to be readily available. High cost in production of PHA limits the production of these polymers at industrial scale. Bacteria are screened for PHA from diverse niches to meet the current requirements of cheap PHA production at industrial level. The microbial biofilm formed on the surface of microplastic could be a potential source in providing bacteria of economic importance. This paper is an attempt to search microplastic niche for potential PHA producers. PHA production variation was observed with different parameters such as type of carbon source, nitrogen source concentration and also time of incubation. Bacillus sp. CM27 showed maximum PHA yield up to 32.1% among other isolates at 48 h with 2% glucose as carbon source. Optimization of media leads to increase in PHA yield (37.69%) of CDW in Bacillus sp. CM27. Amino acid sequence of Bacillus sp.CM27 showed the presence of PhaC box with sequence, G-Y-C-M-G-G having cysteine in the middle of the box. The extracted polymer was confirmed by FTIR spectroscopy.

Microplastic pollution in fragile coastal ecosystems with special reference to the X-Press Pearl maritime disaster, southeast coast of India

Microplastics (MPs) are a global environmental concern and pose a serious threat to marine ecosystems. This study aimed to determine the abundance and distribution of MPs in beach sediments (12 beaches), marine biota (6 beaches) and the influence of microbes on MPs degradation in eco-sensitive Palk Bay and Gulf of Mannar coast. The mean MP abundance 65.4 ± 39.8 particles/m² in beach sediments; 0.19 ± 1.3 particles/individual fish and 0.22 ± 0.11 particles g^-1 wet weight in barnacles. Polyethylene fragments (33.4%) and fibres (48%) were the most abundant MPs identified in sediments and finfish, respectively. Histopathological examination of fish has revealed health consequences such as respiratory system damage, epithelial degradation and enterocyte vacuolization. In addition, eight bacterial and seventeen fungal strains were isolated from the beached MPs. The results also indicated weathering of MPs due to microbial interactions. Model simulations helped in tracking the fate and transboundary landfall of spilled MPs across the Indian Ocean coastline after the X-Press Pearl disaster. Due to regional circulations induced by the monsoonal wind fields, a potential dispersal of pellets has occurred along the coast of Sri Lanka, but no landfall and ecological damage are predicted along the coast of India.

Enrichment and dissemination of bacterial pathogens by microplastics in the aquatic environment

Microplastic pollution and associated impacts in the aquatic environment are spreading at an alarming rate worldwide. Plastic waste is increasing in the environment, and microplastics (MPs) are becoming a growing issue because they serve as vectors for pathogen transmission. This is the first comprehensive review that specifically addresses MPs as a source and vector of pathogenic bacteria, mainly associated with genera Vibrio, Pseudomonas, Acinetobacter, and so on, which are discovered to be more abundant on the aquatic plastisphere than that in the surrounding wastewater, freshwater, and marine water ecosystems. The horizontal gene transfer, chemotaxis, and co-selection and cross-selection could be the potential mechanism involved in the enrichment and dissemination of bacterial pathogens through the aquatic plastisphere. Further, bacterial pathogens through aquatic plastisphere can cause various ecological and human health impacts such as disrupted food chain, oxidative stress, tissue damages, disease transmission, microbial dysbiosis, metabolic disorders, among others. Last but not least, future research directions are also described to find answers to the challenging questions about bacterial pathogens in the aquatic plastisphere to ensure the integrity and safety of ecological and human health.

An appraisal of early stage biofilm-forming bacterial community assemblage and diversity in the Arabian Sea, India

The community composition and distribution of early-stage (24 h) biofilm-forming bacteria on two different surfaces (glass slide and polystyrene plastic slide) at three different locations (Diu, Alang and Sikka) were studied using a culture-dependent and next-generation sequencing (NGS) approach in the Arabian Sea, Gujarat, India. The most dominant phyla observed using the NGS approach were the Proteobacteria among the sampling sites. Gammaproteobacteria class dominated both the surfaces among the sites and accounted for 46.7% to 89.2% of total abundance. The culture-dependent analysis showed Proteobacteria and Firmicutes as the dominant phyla on the surfaces within the sampling sites. During the initial colonization, hydrocarbon-degrading bacterial strains have also attached to the surfaces. The outcome of this study would be of great importance for targeting the early stage biofilm-forming and hydrocarbon-degrading bacterial isolates may help to degrade plastic in the marine environment.

Biofilm Structural and Functional Features on Microplastic Surfaces in Greenhouse Agricultural Soil

Microplastics (MPs) enter the soil through a variety of pathways, including plastic mulching, sludge, and organic manure application. In recent years, domestic and foreign experts and scholars have been concerned about the residues and contamination of MPs in the soil of greenhouse agriculture. In this investigation, five types of MPs including low-density polyethylene (LDPE), high-density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), and polyethylene terephthalate (PET), and two concentrations (1% and 5%, w/w) were used in a 30-day external exposure test. Evidence of microbial enrichment was found on the surface of the MPs. The total amount of biofilm on the surface of MPs increased dramatically with increasing exposure time and MP concentrations. The polysaccharide content of extracellular polymers (EPS) in biofilms was significantly different, and the maximum PS1 (1% (w/w) PS) concentration was 50.17 mg/L. However, EPS protein content did not change significantly. The dominant bacteria on the surface of MPs with different types and concentrations were specific, and the relative abundance of Patescibacteria was significantly changed at the phylum level. At the genus level, Methylophaga, Saccharimonadales, and Sphingomonas dominated the flora of LDPE1 (1% (w/w) LDPE), PS1, and PET5 (5% (w/w) PET). The dominant bacteria decompose organic materials and biodegrade organic contaminants. According to the FAPROTAX functional prediction study, chemoheterotrophy and aerobic chemoheterotrophyplay a role in ecosystem processes such as carbon cycle and climate regulation. The application of LDPE1 has a greater impact on the carbon cycle. Plant development and soil nutrients in greenhouse agriculture may be influenced by the interaction between MPs and microorganisms in the growing area, while MP biofilms have an impact on the surrounding environment and pose an ecological hazard.

Microplastics benefit bacteria colonization and induce microcystin degradation

Microplastics (MPs) can sorb toxic substances and be colonized by microorganisms. However, the interactions between the adsorbed toxic substances and the MPs biofilm remains inadequately understood. Here, a 37-days microcosm experiment was conducted to investigate the influence of polystyrene microplastics (PS-MPs) on microcystin (MC-LR) behavior in turbulent scenarios. The results revealed that adsorption by PS-MPs was the primary process that led to a quick reduction of aquatic MC-LR concentrations. With the colonization of microorganisms on the PS-MPs, the attached biofilm altered the surface properties of PS-MPs, which enhanced the bio-adsorption of MC-LR. Meanwhile, microcystins degrading bacteria, such as Sphingomonadaceae and Methylophilaceae, inhabited in the biofilm, which facilitated the MC-LR biodegradation; this was also demonstrated by the identified MC-LR degradation products. Thus, the MC-LR concentration in water was constantly decreased, with a maximum removal capability of 35.8% in PS-MPs added groups. In addition, a 25% reduction of MC-LR was recorded in PS-MPs added static water. This suggested that the interaction between PS-MPs, biofilm, and MC-LR may be prevalent in natural waters. Our results indicate MPs as vectors for toxic substances could be a double-edged sword (adsorption and biodegradation), which provides new insights for understanding the ecological risks of microplastics.

Microplastic pollution in the surface seawater in Zhongsha Atoll, South China Sea

The prevalence of microplastics in the marine environment has attracted extensive attention. So far, no information is known regarding the temporal and spatial variations of microplastics in Zhongsha Atoll. This study, for the first time, comprehensively investigated the occurrence and distribution of microplastics in the surface seawater in Zhongsha Atoll based on two ocean cruises. The abundances of microplastics measured in the surface seawater of Zhongsha Atoll were in the ranges of not detected (ND) to 67 items/m³, and ND to 160 items/m³ in 2019 and 2020, respectively. All microplastics detected in Zhongsha Atoll were fibers, most of which were transparent and less than 2 mm. Polyethylene terephthalate was the dominating composition of microplastics. These results suggested that sewage, surface runoff, atmospheric deposition by neighboring land, and fishing activities may be the primary pollution sources. This study provides critical information on microplastic pollution in Zhongsha Atoll for the first time, calling for more research in the management of marine plastic debris in the future.