Early microbial biofilm formation on marine plastic debris

Sources, interactions, influencing factors and ecological risks of microplastics and antibiotic resistance genes in soil: A review

Microplastics (MPs) and antibiotic resistance genes (ARGs) are gaining increasing attention as they pose a threat to the ecological environment and human health as emerging contaminants. MPs has been proved to be a hot spot in ARGs, and although it has been extensively studied in water environment, the results of bibliometrics statistical analysis in this paper showed that relevant studies in soil ecological environment are currently in the initial stage. In view of this, the paper provides a systematic review of the sources, interactions, influencing factors, and ecological risks associated with MPs and ARGs in soil environments. Additionally, the mechanism and influencing factors of plastisphere formation and resistance are elaborated in detail. The MPs properties, soil physicochemical properties, soil environmental factors and agricultural activities are the primarily factors affecting the interaction between MPs and ARGs in soil. Challenges and development directions of related research in the future are also prospected. It is hoped that the review could assist in a deeper comprehension and exploration of the interaction mechanism between MPs and ARGs in soil as well as the function of MPs in the transmission process of ARGs among diverse environmental media and organisms, and provide theory basis and reference for the MPs and ARGs pollution control and remediation in soil.

The combination of detection and simulation for the distribution and sourcing of microplastics in Shing Mun River estuary, Hong Kong

For the first time, combined detection and simulation was performed on microplastic (MP) debris in surface water, sediment, and oyster samples at ten coastal sites of Shing Mun River estuary, Hong Kong at different tidal conditions. The MP debris were extracted and detected using Fourier transform infrared (FT-IR) spectroscopy, and the simulation was conducted using Weather Research & Forecasting Model (WRF) / Regional Ocean Modelling System (ROMS) coupled hydro-dynamic modelling and the subsequent Lagrangian particle tracking. The results demonstrated the majority of polyethylene (with partial chlorine substitution) debris among all the MPs found, and great spatial and tidal variabilities of MP concentrations were observed. The combination of MP observation and simulations referred to the interpretation that a considerable percentage of MPs found in this study originated from South China Sea. Those MPs were probably transported to Tolo Harbour through sea currents and drifted inshore and offshore with tides. This study provided baseline measures of MP concentrations in Shing Mun River estuary and comprehensive understanding for how MPs transport and distribute within a dynamic estuarine system.

Temporal changes in microalgal biomass and species composition on different plastic polymers in nutrient-enriched microcosm experiments

Marine plastic debris (MPD) is a potential threat to marine ecosystems, but its function as a vector for the transportation of harmful microalgae and its impact on the habitats of other marine organisms are uncertain. To address this gap in knowledge, we performed month-long experiments in 30 L microcosms that contained plates made of six different plastic polymers (polypropylene [PP], low-density polyethylene [LDPE], high-density polyethylene [HDPE], polyvinyl chloride [PVC], polyethylene terephthalate [PET], and polystyrene [PS]), and examined the time course of changes in planktonic and periphytic microalgae. There were no significant differences in the composition of periphytic microalgae or biomass among the different plastic polymers (p > 0.05). Nutrient depletion decreased the abundance of planktonic microalgae, but increased the biomass of attached periphytic microalgae (p < 0.05). In particular, analysis of the plastic plates showed that the abundance of benthic species that are responsible for harmful algal blooms (HABs), such as Amphidinium operculatum and Coolia monotis, significantly increased over time (days 21-28; p < 0.05). Our findings demonstrated that periphyton species, including benthic microalgae that cause HABs, can easily attach to different types of plastic and potentially spread to different regions and negatively impact these ecosystems. These observations have important implications for understanding the potential role of MPD in the spread of microalgae, including HABs, which pose a significant threat to marine ecosystems.

Effect of Biofouling on the Sorption of Organic Contaminants by Microplastics

Microplastics in the aquatic environment are susceptible to colonization by surrounding microorganisms, which form biofilms over the microplastic's surface. These biofilm-laden microplastics can then interact with a diverse array of contaminants. In the present study, biofilms were grown on microplastics in a laboratory setting using Pseudomonas aeruginosa as a model biofilm-forming bacterium for periods of 5 to 15 days. The sorption of three organic compounds representing different levels of hydrophobicity, namely methylene blue (MB), phenanthrol, and phenanthrene, was used to evaluate the effect of biofilm biomass on the adsorption of organic contaminants to microplastics. The sorption of MB and phenanthrol was found to increase with biofouling time, indicating affinity between these contaminants and the biofilm biomass on the particle. However, the presence of a biofilm did not influence the sorption of phenanthrene on the microplastics. These results suggest that the hydrophobicity of organic contaminants plays a major role in how biofouling of microplastics will influence contaminant sorption by microplastics. For some contaminants, biofilm can enhance the role of microplastics as contaminant vectors. These findings emphasize the need to understand the biomass load on environmental microplastics and the contaminants that associate with it for an accurate representation of the risk associated with microplastics in the environment. Environ Toxicol Chem 2024;43:1973-1981. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Insights into the seasonal distribution of microplastics and their associated biofilms in the water column of two tropical estuaries

The present study describes the seasonal distribution of microplastics (MPs) and their associated biofilms in the water column of the Netravathi-Gurupura estuary, southwest India. An average abundance of 8.15 (±3.81) particles/l and 1.14 (±0.78) particles/l was observed during the wet and dry seasons, respectively. Fibres, films, and fragments accounted for majority of the microplastics. Polyethylene terephthalate, polyethylene, polyurethane, polyester, polystyrene, and high-density polyethylene were the major polymers. The risk assessment revealed a low Pollution Load Index, but the Polymer Hazard Index showed higher toxicity. Diatoms from nine genera were observed attached to the microplastic samples with Amphora and Navicula spp. reported in both estuaries during both seasons. The considerable diversity of diatoms, along with other microbial groups, in microplastic-associated biofilms in this study, highlights the urgent need to understand the structure and development of microplastic-associated biofilms and their role in the vertical and horizontal transport of microplastics in tropical estuaries.

Distribution characteristics and ecological risk analysis of microplastics in sediments and effluents related to offshore oil and gas activities in the Bohai Sea, China

Oil and gas activities are sources of marine microplastics (MPs) but have received less attention globally. This study assessed the distribution characteristics and ecological risks of MPs in 31 sediment samples and effluent samples of 5 oil and gas platforms related to offshore oil and gas activities in the Bohai Sea. The results showed that the mean abundance of MPs in sediment, produced water, and domestic sewage was 205.7 ± 151.5 items/kg d.w., 18 ± 11 items/L, and 26 ± 39 items/L, respectively. The MPs in sediments and effluents were dominated by transparent, rayon, and fibers <1 mm. Oil and gas activities may influence the abundance of MPs in the sediments. The sediments in the area were at a low level of risk, but some samples exhibited indexes beyond low levels. The mass of MPs carried by the effluents from oil and gas platforms in the Bohai Sea was less than that of other sources.

A systematic review on the impact of micro-nanoplastics on human health: Potential modulation of epigenetic mechanisms and identification of biomarkers

Epigenetic-mediated modifications, induced by adverse environmental conditions, significantly alter an organism's physiological mechanisms. Even after elimination of the stimulus, these epigenetic modifications can be inherited through mitosis, thereby triggering transgenerational epigenetics. Plastics, with their versatile properties, are indispensable in various aspects of daily life. However, due to mismanagement, plastics have become so ubiquitous in the environment that no ecosystem on Earth is free from micro-nanoplastics (MNPs). This situation has raised profound concerns regarding their potential impact on human health. Recently, both in vivo animal and in vitro human cellular models have shown the potential to identify the harmful effects of MNPs at the genome level. The emerging epigenetic impact of MNP exposure is characterized by short-term alterations in chromatin remodelling and miRNA modulation. However, to understand long-term epigenetic changes and potential transgenerational effects, substantial and more environmentally realistic exposure studies are needed. In the current review, the intricate epigenetic responses, including the NHL-2-EKL-1, NDK-1-KSR1/2, and WRT-3-ASP-2 cascades, wnt-signalling, and TGF- β signalling, established in model organisms such as C. elegans, mice, and human cell lines upon exposure to MNPs, were systematically examined. This comprehensive analysis aimed to predict human pathways by identifying human homologs using databases and algorithms. We are confident that various parallel miRNA pathways, specifically the KSR-ERK-MAPK pathway, FOXO-Insulin cascade, and GPX3-HIF-α in humans, may be influenced by MNP exposure. This influence may lead to disruptions in key metabolic and immune pathways, including glucose balance, apoptosis, cell proliferation, and angiogenesis. Therefore, we believe that these genes and pathways could serve as potential biomarkers for future studies. Additionally, this review emphasizes the origin, dispersion, and distribution of plastics, providing valuable insights into the complex relationship between plastics and human health while elaborating on the epigenetic impacts.

Combined environmental pressure induces unique assembly patterns of micro-plastisphere biofilm microbial communities in constructed wetlands

The characteristics and dynamics of micro-plastisphere biofilm on the surface of microplastics (MPs) within artificial ecosystems, such as constructed wetlands (CWs), remain unclear, despite these ecosystems' potential to serve as sinks for MPs. This study investigates the dynamic evolution of micro-plastisphere biofilm in CWs, utilizing simulated wastewater containing sulfamethoxazole and humic acid, through physicochemical characterization and metagenomic analysis. Two different types of commercial plastics, including non-degradable polyethylene and degradable polylactic acid, were shredded into MPs and studied. The findings reveal that the types, shape and incubation time of MPs, along with humic acid content in wastewater, affected the quantity and quality of biofilms, such as the biofilm composition, spatial structure and microbial communities. After just 15 days into incubation, numerous microbials were observed on MP samples, with increases in biofilms content and enhanced humification of extracellular polymeric substances over time. Additionally, microbial communities on polylactic acid MPs, or those incubated for longer time, exhibit higher diversity, connectivity and stability, along with reduced vulnerability. Conversely, biofilms on polyethylene MPs were thicker, with higher potential for greenhouse gas emission and increased risk of antibiotic resistance genes. The addition of humic acid demonstrated opposite effects on biofilms across environmental interfaces, possibly due to its dual potential to produce light-induced free radicals and serve as a carbon source. Binning analysis further uncovered a unique assembly pattern of nutrients cycle genes and antibiotic resistance genes, significantly correlated within micro-plastisphere microbial communities, under the combined stress of nutrition and sulfamethoxazole. These results emphasize the shaping of micro-plastisphere biofilm characteristics by unique environmental conditions in artificial ecosystems, and the need to understand how DOM and other pollutants covary with MP pollution.

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.

Nascently generated microplastics in freshwater stream are colonized by bacterial communities from stream and riparian sources

The purpose of this study was to examine bacterial colonization of different types of microplastics through time in a freshwater ecosystem. Microplastics are persistent pollutants in aquatic ecosystems. Bacteria readily colonize microplastic surfaces and may contribute to their degradation, but the taxa involved, and their degradative abilities, differ based on factors such as microplastic chemistry, plastic age, and specific ecosystem types. Four different common types of newly manufactured microplastics, high-density polyethylene, low-density polyethylene, polypropylene, and polystyrene, were incubated for 7 weeks in a freshwater stream and sampled. Sample collection was timed to examine the development of early and late bacterial biofilm communities. Microplastics were analyzed for changes to buoyancy, weight, contact angles (an indicator of surface roughness), bacterial community composition, and the number of bacterial cells. Time was the only significant contributing factor in the development of bacterial biofilm communities on microplastic disks over the 7-week study. Notably, the Comamonadaceae were abundant early in the study and decreased in abundance with time, while the Methylococcaceae demonstrated the opposite trend. Different physicochemical properties among the various types of microplastics had only a minor effect on bacterial community compositions of biofilms growing on the microplastics. Additionally, the surfaces of all microplastic disks became rougher over time in the stream. Collectively, our results show that microplastic surfaces undergo surface modification and community succession as time progresses, regardless of microplastic type, in a freshwater stream ecosystem.

Effect of particle density on microplastics transport in artificial and natural porous media

The occurrence and persistence of microplastics (MPs) in natural environments are of increasing concern. Along with this, the transport of MPs in sediments has been investigated mainly focusing on the effect of plastic size and shape, media size effect, and solution chemistry. Yet, the influence of particle density is only partially understood. Therefore, column experiments on the transport of variably buoyant MPs in saturated natural sediments and glass beads were conducted, and transport parameters were quantified using a two-site kinetic transport model with a depth-dependent blocking function (the amount of retained MPs does not decrease at a constant rate with increasing depth, the majority of MPs were retained near the column inlet). Neutral, sinking, and buoyant MPs within the same size range were selected, with stable water isotope applied as conservative tracer to explore water and MP movement in the tested sediments. The results showed that 95.5 ± 1.4% of sinking MPs remained in columns packed with gravel, followed by buoyant and neutral MPs, thus indicating that particle density does affect MP mobility. Similar recovered amounts of MPs were found in columns packed with glass beads, indicating that tested sediment types do not affect the deposition behavior of MPs. The breakthrough curves of MPs were accurately described by the selected model. However, the simulated retention profiles overestimated the observed MP amount in layers closest to the column inlet. The coupled experimental and modeled results suggest an enhanced retention of sinking MPs, while neutrally and buoyant MPs exhibit a higher mobility in comparison. Thus, neutral or buoyant MPs can potentially pose a higher contamination risk to subsurface porous media environments compared to sinking MPs. Discrepancies between observed and simulated retention profiles indicate that future model development is needed for advancing the MP deposition as affected by particle density.

Understanding and addressing microplastic pollution: Impacts, mitigation, and future perspectives

Improper disposal of household and industrial waste into water bodies has transformed them into de facto dumping grounds. Plastic debris, weathered on beaches degrades into micro-particles and releases chemical additives that enter the water. Microplastic contamination is documented globally in both marine and freshwater environments, posing a significant threat to aquatic ecosystems. The small size of these particles makes them susceptible to ingestion by low trophic fauna, a trend expected to escalate. Ingestion leads to adverse effects like intestinal blockages, alterations in lipid metabolism, histopathological changes in the intestine, contributing to the extinction of vulnerable species and disrupting ecosystem balance. Notably, microplastics (MPs) can act as carriers for pathogens, potentially causing impaired reproductive activity, decreased immunity, and cancer in various organisms. Studies have identified seven principal sources of MPs, including synthetic textiles (35%) and tire abrasion (28%), highlighting the significant human contribution to this pollution. This review covers various aspects of microplastic pollution, including sources, extraction methods, and its profound impact on ecosystems. Additionally, it explores preventive measures, aiming to guide researchers in selecting techniques and inspiring further investigation into the far-reaching impacts of microplastic pollution, fostering effective solutions for this environmental challenge.

Microplastic accumulation dynamics in Han river headwaters: Sediment interactions and environmental implication

The prevalence of microplastic (MP) contamination has become a significant environmental concern due to its pervasive nature and persistent effects. While sediments are considered major repositories for MPs, information on their spatial distribution within these matrices is insufficient. This research examined both the horizontal and vertical presence of MPs in the sediments surrounding Lake Paldang in South Korea, alongside a comprehensive evaluation of the physicochemical characteristics of the samples obtained. The total content of MPs varied from 2.15 to 122.2 particles g-1. The average contents of MPs on surface sediments were 40.47, 34.14, 5.01, and 8.19 particles g-1 in north mainstream (NM), south mainstream (SM), tributary (TB), and Tributary catchment (TC) based on Sonae Island, Gyeongan stream, respectively. The most abundant MP types were polyethylene (PE), polytetrafluoroethylene (PTFE), and polypropylene (PP), accounting for more than 70% of the total MPs. The most abundant sizes of MPs were within 45-100 µm. At all sediment depths, polymers were distributed in the order PE, PP, and polyester in NM, SM, and TC, respectively, whereas PTFE mainly occurred in the surface layer. MPs distribution also exhibited seasonal variation as larger inflows and flow rates varied with season.

Biodegradation of polyurethanes by Staphylococcus warneri and by microbial co-culture

With the increasing production and use of polyurethanes (PUs), it is necessary to develop sustainable techniques for the remediation of plastic pollution. The use of microorganisms capable of biodegrading PUs may be an environmentally desirable solution for controlling these plastic contaminants. To contribute to the discovery of alternatives for the mitigation of plastics in the environment, this study aimed to explore the potential of StaphylococcuswarneriUFV_01.21, isolated from the gut of Galleria mellonellalarvae, for biodegradation of PU in pure culture and microbial co-culture with Serratia liquefaciensL135. S. warneri grew using Impranil® PU as the sole carbon source in pure culture and co-culture. With six days of incubation, the biodegradation of Impranil® in Luria Bertani broth was 96, 88 and 76%, while in minimal medium, it was 58, 54 and 42% for S. warneri, S. liquefaciens, and co-culture, respectively. In addition, S. warneri in pure culture or co-culture was able to biodegrade, adhere and form biofilms on the surfaces of Impranil® disks and poly[4,4'-methylenebis (phenyl isocyanate)-alt-1,4-butanediol/di(propylene glycol)/polycaprolactone] (PCLMDI) films. Scanning electron microscopy also revealed biodegradation by detecting the formation of cracks, furrows, pores, and roughness on the surfaces of inoculated PU, both with pure culture and microbial co-culture. This study is the first to demonstrate the potential of S. warneriin PU biodegradation.

Reviewing the role of microplastics as carriers for microorganisms in absorbing toxic trace elements

The pervasive presence of microplastics in various settings, such as freshwater and marine ecosystems, has sparked serious concerns. Microplastics can operate as possible transporters for hazardous trace elements or microbes, even though they are not naturally able to actively absorb these compounds. The binding sites on the plastic's surface or the complexes that are formed with the organic material on the plastic are how this adsorption process takes place. Microplastics' surfaces also seem to be attractive to microorganisms, such as bacteria and algae. Microorganisms can adhere to the rough surface of microplastics, which facilitates their colonization and formation of biofilms. Numerous bacteria, including ones that have the ability to absorb hazardous trace elements, can be found in these biofilms. Microplastics and microbes can interact in ways that are advantageous and detrimental. Microplastics have the ability to act as a substrate for microbial growth, which could lead to an increase in the quantity of microorganisms in the surrounding environment. On the other hand, microplastics may make it easier for microbes to spread to new areas, which could help dangerous or deadly species proliferate. Research is still ongoing to determine the degree to which microplastics serve as carriers of microbes and hazardous trace elements. Comprehending the implications of microplastics, pollutants, and microorganisms in a variety of environmental conditions is difficult due to their complex interplay. This review provides a detailed description of the complexity of the problem and used the examples related to microplastics, its environmental effects, and impacts on human health.

Vehicle transmission of antibiotic-resistant pathogens mediated by plastic debris in aquatic ecosystems

Plastic materials are emerging environmental pollutants acting as potential vehicles for accumulation and spread of multidrug-resistant bacteria. The current study investigates the role of plastics in favoring the dispersal of specific pathogens and their associated antibiotic resistant genes (ARGs). Artificial plastic substrates (APSs) were submerged in seven sampling points of Lake Bracciano (Italy), and after one-month both APSs and raw water (RW) samples were collected. Through the combination of standard microbiological and biochemical techniques, 272 bacterial strains were identified and characterized for antibiotic resistant profiling. Our results revealed a notable difference in terms of diversity and abundance of pathogenic bacteria recovered from APSs, compared to RW. In addition, higher resistance patterns were detected in APSs isolates, with frequent appearance of relevant ARGs and class 1 integrons. These findings reinforce the idea that plastic materials in aquatic ecosystems serve as a reservoir for superbugs, significantly contributing to the dissemination of ARGs.

A review focusing on mechanisms and ecological risks of enrichment and propagation of antibiotic resistance genes and mobile genetic elements by microplastic biofilms

Microplastics (MPs) are emerging ubiquitous pollutants in aquatic environment and have received extensive global attention. In addition to the traditional studies related to the toxicity of MPs and their carrier effects, their unique surface-induced biofilm formation also increases the ecotoxicity potential of MPs from multiple perspectives. In this review, the ecological risks of MPs biofilms were summarized and assessed in detail from several aspects, including the formation and factors affecting the development of MPs biofilms, the selective enrichment and propagation mechanisms of current pollution status of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) in MPs biofilms, the dominant bacterial communities in MPs biofilms, as well as the potential risks of ARGs and MGEs transferring from MPs biofilms to aquatic organisms. On this basis, this paper also put forward the inadequacy and prospects of the current research and revealed that the MGEs-mediated ARG propagation on MPs under actual environmental conditions and the ecological risk of the transmission of ARGs and MGEs to aquatic organisms and human beings are hot spots for future research. Relevant research from the perspective of MPs biofilm should be carried out as soon as possible to provide support for the ecological pollution prevention and control of MPs.

Microplastics and PAHs mixed contamination: An in-depth review on the sources, co-occurrence, and fate in marine ecosystems

Microplastics (MPs) and polycyclic aromatic hydrocarbons (PAHs) are toxic contaminants that have been found in marine ecosystems. This review aims to explore the sources and mechanisms of PAHs and MPs mixed contamination in marine environments. Understanding the released sources of PAHs and MPs is crucial for proposing appropriate regulations on the release of these contaminants. Additionally, the mechanisms of co-occurrence and the role of MPs in distributing PAHs in marine ecosystems were investigated in detail. Moreover, the chemical affinity between PAHs and MPs was proposed, highlighting the potential mechanisms that lead to their persistence in marine ecosystems. Moreover, we delve into the various factors influencing the co-occurrence, chemical affinity, and distribution of mixed contaminants in marine ecosystems. These factors, including environmental characteristics, MPs properties, PAHs molecular weight and hydrophobicity, and microbial interactions, were critically examined. The co-contamination raises concerns about the potential synergistic effects on their degradation and toxicity. Interesting, few studies have reported the enhanced photodegradation and biodegradation of contaminants under mixed contamination compared to their individual remediation. However, currently, the remediation strategies reported for PAHs and MPs mixed contamination are scarce and limited. While there have been some initiatives to remove PAHs and MPs individually, there is a lack of research specifically targeting the removal of mixed contaminants. This deficiency highlights the need for further investigation and the development of effective remediation approaches for the efficient remediation of PAHs and MPs from marine ecosystems.

Biodegradation Mechanism of Polystyrene by Mealworms (Tenebrio molitor) and Nutrients Influencing Their Growth

A degradation mechanism of polystyrene (PS) in mealworms reared on expanded PS (EPS) was investigated by its decrease in molecular weight and change in chemical structure. A 33% decrease in molecular weight was observed for the digested PS in the frass after 1 week of feeding to mealworms. The FT-IR and py-GC/MS spectra of the digested PS showed radical oxidative reactions taking place in the mealworm body. The presence of hydroperoxide, alcohol and phenol groups was confirmed, and dimer fragments of styrene with quinone and phenol groups were obtained. The decrease in molecular weight and the alternation of benzene rings indicated that autoxidation and quinonization via phenolic intermediates occurred simultaneously in the mealworm body. The survival rate of mealworms reared on EPS was higher than that of starved worms, indicating that EPS was a nutrient source. However, no weight gain was observed in mealworms fed EPS alone. Comparison with the mixed diets with bran or urethane foams (PU) indicated that protein, phosphorus and magnesium components absent from EPS were required for mealworm growth.

Colonization characteristics and dynamic transition of archaea communities on polyethylene and polypropylene microplastics in the sediments of mangrove ecosystems

Microplastics are a growing concern in mangrove ecosystems; however, their effects on archaeal communities and related ecological processes remain unclear. We conducted in situ biofilm-enrichment experiments to investigate the ecological influence of polyethylene (PE) and polypropylene microplastics on archaeal communities in the sediments of mangrove ecosystems. The archaeal community present on microplastics was distinct from that of the surrounding sediments at an early stage but became increasingly similar over time. Bathyarchaeota, Thaumarchaeota, Euryarchaeota, and Asgardaeota were the most abundant phyla. Methanolobus, an archaeal biomarker, was enriched in PE biofilms, and significantly controlled by homogeneous selection in the plastisphere, indicating an increased potential risk of methane emission. The dominant archaeal assembly process in the sediments was deterministic (58.85%-70.47%), while that of the PE biofilm changed from stochastic to deterministic during the experiment. The network of PE plastispheres showed less complexity and competitive links, and higher modularity and stability than that of sediments. Functional prediction showed an increase in aerobic ammonia oxidation during the experiment, whereas methanogenesis and chemoheterotrophy were significantly higher in the plastisphere. This study provides novel insights into the impact of microplastic pollution on archaeal communities and their mediating ecological functions in mangrove ecosystems.

Recent advances in the relationships between biofilms and microplastics in natural environments

Plastic pollution in the form of microplastics (MPs), poses a significant threat to natural ecosystems, with detrimental ecological, social, and economic impacts. This review paper aims to provide an overview of the existing research on the interaction between microbial biofilms and MPs in natural environments. The review begins by outlining the sources and types of MPs, emphasizing their widespread presence in marine, freshwater, and terrestrial ecosystems. It then discusses the formation and characteristics of microbial biofilms on MPs surfaces, highlighting their role in altering the physicochemical properties of MPs and facilitating processes such as vertical transport, biodegradation, dispersion of microorganisms, and gene transfer. Different methods used to assess these interactions are discussed, including microbiological and physicochemical characterization. Current gaps and challenges in understanding the complex relationships between biofilms and MPs are identified, highlighting the need for further research to elucidate the mechanisms underlying these complex interactions and to develop effective mitigation strategies. Innovative solutions, including bioremediation techniques and their combination with other strategies, such as nanotechnology, advanced filtration technologies, and public awareness campaigns, are proposed as promising approaches to address the issue of MPs pollution. Overall, this review underscores the urgent need for a multidisciplinary approach to combating MPs pollution, combining scientific research, technological innovation, and public engagement to safeguard the health and integrity of natural ecosystems.

Bisphenol A sorption on commercial polyvinyl chloride microplastics: Effects of UV-aging, biofilm colonization and additives on plastic behaviour in the environment

Chemical additives are important components in commercial microplastics and their leaching behaviour has been widely studied. However, little is known about the potential effect of additives on the adsorption/desorption behaviour of pollutants on microplastics and their subsequent role as vectors for pollutant transport in the environment. In this study, two types of commercial polyvinyl chloride (PVC1 and PVC2) microplastics were aged by UV irradiation and biotic modification via biofilm colonization to investigate the adsorption and desorption behaviour of bisphenol A (BPA). Surface cracks and new functional groups (e.g., O-H) were found on PVC1 after UV irradiation, which increased available adsorption sites and enhanced H‒bonding interaction, resulting in an adsorption capacity increase from 1.28 μg/L to 1.85 μg/L. However, the adsorption and desorption capacity not showed significant changes for PVC2, which might be related to the few characteristic changes after UV aging with the protection of light stabilizers and antioxidants. The adsorption capacity ranged from 1.28 μg/L to 2.06 μg/L for PVC1 and PVC2 microplastics, and increased to 1.62 μg/L-2.95 μg/L after colonization by biofilms. The increased adsorption ability might be related to the N-H functional group, amide groups generated by microorganisms enhancing the affinity for BPA. The opposite effect was observed for desorption. Plasticizers can be metabolized during biofilm formation processes and might play an important role in microorganism colonization. In addition, antioxidants and UV stabilizers might also indirectly influence the colonization of microorganisms' on microplastics by controlling the degree to which PVC microplastics age under UV. The amount of biomass loading on the microplastics would further alter the adsorption/desorption behaviour of contaminants. This study provides important new insights into the evaluation of the fate of plastic particles in natural environments.

Deleterious effects of polypropylene released from paper cups on blood profile and liver tissue of Clarias gariepinus: bioremediation using Spirulina

Despite numerous studies on microplastics, the biological impacts of polypropylene microplastics (PP-MPs) and its toxicity on freshwater fish have yet to be fully revealed. The purpose of this research was to look at the potentially harmful effects of PP-MPs in freshwater African catfish Clarias gariepinus and bioremediation using Spirulina. After acclimatization to laboratory conditions, 108 fish (125 ± 3 gm and 27 ± 2 cm) were assigned into triplicate six experimental groups (12 fish/group), a control group, Spirulina group (SP), PP-MP-treated groups (0.14 and 0.28 mg/l PP-MPs), and PP-MP + Spirulina-treated groups (0.14 mg/l PP-MPs + 200 mg/L SP and 0.28 mg/l PP-MPs +200 mg/L SP) for 15-day exposure and 45-day recovery after that. The hematological parameters exhibiting significance (RBCs, Hct, Hb, and MCV) or non-significance (MCH and MCHC) either decreased with the increase in PP-MP doses from 0.0 in the control to 0.28 mg/L red blood cells (RBCs), hematocrit (Hct), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), hemoglobin (Hb) and platelets or increased with such an increase in doses (mean corpuscular volume (MCV)). The liver enzyme activity, aspartate aminotransferase (AST), alkaline phosphatase (ALP), and alanine aminotransferase (ALT) exhibited non-significant (p ≥ 0.05) or significant (p < 0.05) increases in (0.14 and 0.28 mg/L) PP-MP-exposed groups, respectively, except ALP. Furthermore, there was a significant (p < 0.05) or non-significant (p ≥ 0.05) increase in 0.14 and 0.28 mg/l PP-MP +200 mg/L-exposure groups, respectively, compared to the control group and the same exposure group without Spirulina. In comparison to the control group, PP-MPs (0.14 and 0.28 mg/L) induced a significant (p < 0.05) increase in the percentage of poikilocytosis and nuclear abnormalities of RBCs. The liver tissue from fish exposed to PP-MPs exhibited varying degrees of pathological changes. These results indicated that these pathological changes increased with PP-MP concentration, suggesting that the effect of PP-MPs was dose-dependent. After 45 days of recovery under normal conditions, it was obvious that there was a significant improvement in the percentage of poikilocytosis and nuclear abnormalities of RBCs, as well as a non-significant improvement in hemato-biochemical parameters and liver tissue.

Assessing biofilm formation and resistance of vibrio parahaemolyticus on UV-aged microplastics in aquatic environments

UV degradation of marine microplastics (MPs) could increase their vector potential for pathogenic bacteria and threaten human health. However, little is known about how the degree of UV aging affects interactions between MPs and pathogens and how various types of MPs differ in their impact on seafood safety. This study investigated five types of UV-aged MPs and their impact on Vibrio parahaemolyticus, a seafood pathogen. MPs exposed to UV for 60 days showed similar physicochemical changes such as surface cracking and hydrophobicity reduction. Regardless of the type, longer UV exposure of MPs resulted in more biofilm formation on the surface under the same conditions. V. parahaemolyticus types that formed biofilms on the MP surface showed 1.4- to 5.0-fold upregulation of virulence-related genes compared to those that did not form biofilms, independently of UV exposure. However, longer UV exposure increased resistance of V. parahaemolyticus on MPs to chlorine, heat, and human gastrointestinal environment. This study implies that the more UV degradation occurs on MPs, the more microbial biofilm formation is induced, which can significantly increase virulence and environmental resistance of bacteria regardless of the type of MP.

Ingestion and adherence of microplastics by estuarine mysid shrimp

Microplastics have been reported to be present in zooplankton, yet questions persist regarding their fate and dynamics within biota. We selected the commercial mysid shrimp, Mesopodopsis orientalis, as the focal zooplankton for this study due to their crucial role in our study area, the Inner Gulf of Thailand in January 2022. We investigated the presence of microplastics in mysid bodies and fecal pellets, examining both attached microplastics on external body parts and those ingested. In addition, we conducted microplastic feeding experiments, exposing mysids to various treatments of microplastics. The results of the field investigation indicate that mysids exhibited an average of 0.12 ± 0.03 microplastic items/mysid from whole-body samples. The shape, type, and color of microplastics found in mysids were similar to those present in seawater, with blue PET microfibers being the most prevalent. Our observations on live mysids revealed that microplastics were acquired through ingestion and adherence to appendages and exoskeletons. Microplastics were observed in mysid's fecal pellets at 0.09 ± 0.03 items/mysid, while microplastics adhering to the mysid's body and appendages were observed at 0.10 ± 0.04 items/mysid. The sizes of microplastics extracted from preserved mysids ranged from 58 μm to 4669 μm, with median of 507 μm. The laboratory experiments revealed that the presence of microalgae enhanced microplastic ingestion in mysids; microplastics incubated with a cyanobacterium, Oscillatoria sp., and diatom Navicula sp. significantly increased the number of microplastic particles ingested by mysids. This study showed that microplastics can be more ingested in mysids, especially when food items are present. Microplastic fate in these animals may involve expulsion into the environment or adherence, potentially facilitating their transfer up the marine food web.

Bioaccumulation of trace metals in the plastisphere: Awareness of environmental risk from a European perspective

The term "Plastisphere" refers to the biofilm layer naturally formed by microorganisms attaching to plastic surfaces. This layer possesses the capability to adsorb persistent organic and inorganic pollutants, particularly trace metals, which are the focus of this research study. Immersion experiments were concurrently conducted in five locations spanning four European countries (France, Ireland, Spain, and Italy) utilising eight distinct polymers. These immersions, repeated every three months over a one-year period, aimed to evaluate the baseline bioaccumulation of 12 trace metals. The study underscores the intricate nature of metal bioaccumulation, influenced by both micro-scale factors (such as polymer composition) and macro-scale factors (including geographical site and seasonal variations). Villefranche Bay in France exhibited the lowest metals bioaccumulation, whereas Naples in Italy emerged as the site where bioaccumulation was often the highest for the considered metals. Environmental risk assessment was also conducted in the study. The lightweight nature of certain plastics allows them to be transported across significant distances in the ocean. Consequently, evaluating trace metal concentrations in the plastisphere is imperative for assessing potential environmental repercussions that plastics, along with their associated biota, may exert even in locations distant from their point of emission.

Polyester biodegradability: importance and potential for optimisation

To reduce global CO2 emissions in line with EU targets, it is essential that we replace fossil-derived plastics with renewable alternatives. This provides an opportunity to develop novel plastics with improved design features, such as better reusability, recyclability, and environmental biodegradability. Although recycling and reuse of plastics is favoured, this relies heavily on the infrastructure of waste management, which is not consistently advanced on a worldwide scale. Furthermore, today's bulk polyolefin plastics are inherently unsuitable for closed-loop recycling, but the introduction of plastics with enhanced biodegradability could help to combat issues with plastic accumulation, especially for packaging applications. It is also important to recognise that plastics enter the environment through littering, even where the best waste-collection infrastructure is in place. This causes endless environmental accumulation when the plastics are non-(bio)degradable. Biodegradability depends heavily on circumstances; some biodegradable polymers degrade rapidly under tropical conditions in soil, but they may not also degrade at the bottom of the sea. Biodegradable polyesters are theoretically recyclable, and even if mechanical recycling is difficult, they can be broken down to their monomers by hydrolysis for subsequent purification and re-polymerisation. Additionally, both the physical properties and the biodegradability of polyesters are tuneable by varying their building blocks. The relationship between the (chemical) structures/compositions (aromatic, branched, linear, polar/apolar monomers; monomer chain length) and biodegradation/hydrolysis of polyesters is discussed here in the context of the design of biodegradable polyesters.

Microplastics affect soil-plant system: Implications for rhizosphere biology and fitness of sage (Salvia officinalis L.)

A mesocosm experiment was set-up to investigate the effects of low-density polyethylene (LDPE) fragments deriving from plastic film on soil ecology, rhizosphere and plant (Salvia officinalis L.) fitness. The internal transcribed spacer (ITS) and 16S metagenomic analysis was adopted to evaluate taxonomic and functional shifts of both soil and rhizosphere under the influence of microplastics (MPs). Photosynthetic parameters and enzymes involved in oxidative stress were assessed to unveil the plant physiological state. MP fragments were analysed by scanning electron microscope (SEM) and metagenomics to investigate the plastisphere. Microbial biomarkers of MPs pollution were identified in soil and rhizosphere, reinforcing the concept of molecular biomonitoring. Overall, Bacillus, Nocardioides and Streptomyces genera are bacterial biomarkers of MPs pollution in soil whereas Aspergillus, Fusarium and Trichoderma genera, and Nectriaceae family are fungal biomarkers of MPs polluted soil. The data show that the presence of MPs promotes the abundance of taxa involved in the soil N cycle, but simultaneously reduces the endophytic interaction capability and enhances pathogen related functions at the rhizosphere level. A significant decrease in chlorophyll levels and increase of oxidative stress enzymes was observed in plants grown in MPs-polluted soil. The SEM observations of MPs fragments revealed a complex colonisation, where bacteria (Bacillus in MPSo and Microvirga in MPRz) and fungi (Aspergillus in MPSo and Trichoderma in MPRz) represent the main colonisers. The results demonstrate that the presence of MPs causes changes in the soil and rhizosphere microbial community and functions leading to negative effects on plant fitness.

Microplastics: A potential proxy for tracing extreme flood events in estuarine environments

The transport of microplastics (MPs) is susceptible to being influenced by catchment hydrology; however, there is a notable lack of research on their retention and responses to flood events in estuarine sedimentary records. Herein, we collected two cores in the Yangtze Estuary to explore their microplastic pollution, influencing factors and linkage to flood events. MP abundance exhibited a decreasing trend from the top to the bottom in both cores. Both plastic production and sediment mean grain size showed a significant positive correlation with MP abundance. The sedimentary record displayed a marked surge in MP abundance during the extreme flood period, suggesting a direct influence of flooding on MP deposition. The resuspension of upstream MPs and erosion of land-based MPs by heavy rain might be responsible for this increase. Furthermore, our study identified significant periodicities in MP abundance, closely aligned with the hydrological patterns of the Yangtze River. This study highlights the role of floods in fluvial MP distribution and proposes MPs as a proxy of extreme floods from the 20th century in estuarine environments.

Revealing the long-term impact of photodegradation and fragmentation on HDPE in the marine environment: Origins of microplastics and dissolved organics

The extensive usage of high-density polyethylene (HDPE) materials in marine environments raises concerns about their potential contribution to plastic pollution. Various factors contribute to the degradation of HDPE in marine environments, including UV radiation, seawater hydrolysis, biodegradation, and mechanical stress. Despite their supposed long lifespans, there is still a lack of understanding about the long-term degradation mechanisms that cause weathering of seawater-exposed HDPE products. In this research, the impact of UV radiation on the degradation of HDPE pile sleeves was studied in natural as well as laboratory settings to isolate the UV effect. After nine years of exposure to the marine environment in natural settings, the HDPE pile sleeves exhibited an increase in oxygen-containing surface functional groups and more morphological changes compared to accelerated UVB irradiation in the laboratory. This indicated that combined non-UV mechanisms may play a major role in HDPE degradation than UV irradiation alone. However, UVB irradiation was found to release dissolved organic carbon and total dissolved nitrogen from HDPE pile sleeves, reaching levels of up to 15 mg/L and 2 mg/L, respectively. Our findings underscore the significance of taking into account both UV and non-UV degradation mechanisms when evaluating the role of HDPE in contributing to marine plastic pollution.

Traditional and biodegradable plastics host distinct and potentially more hazardous microbes when compared to both natural materials and planktonic community

Microplastic particles are persistent micropollutants that provide a substrate for the growth of bacterial biofilms, posing a threat to the environment. This study explores the changes in commercially available food containers made of conventional (polypropylene PP, polyethylene terephthalate PET), innovative biodegradable (Mater-Bi) and natural (wood and cellulose) materials, when introduced in the surface waters of Lake Maggiore for 43 days. Spectral changes revealed by FT-IR spectroscopy in PET and Mater-Bi, and changes in thermal properties of all human-made material tested indicated a degradation process occurred during environmental exposure. Despite similar bacterial richness, biofilms on PET, PP, and Mater-Bi differed from natural material biofilms and the planktonic community. Human-made material communities showed a higher proportion of potential pathogens, with PET and PP also exhibiting increased abundances of antibiotic resistance genes. Overall, these findings stress the need for dedicated strategies to curb the spread of human-made polymers in freshwaters, including innovative materials that, due to their biodegradable properties, might be perceived less hazardous for the environment.

Marine plastisphere selectively enriches microbial assemblages and antibiotic resistance genes during long-term cultivation periods

Several studies have focused on identifying and quantifying suspended plastics in surface and subsurface seawater. Microplastics (MPs) have attracted attention as carriers of antibiotic resistance genes (ARGs) in the marine environment. Plastispheres, specific biofilms on MP, can provide an ideal niche to spread more widely through horizontal gene transfer (HGT), thereby increasing risks to ecosystems and human health. However, the microbial communities formed on different plastic types and ARG abundances during exposure time in natural marine environments remain unclear. Four types of commonly used MPs (polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC)) were periodically cultured (46, 63, and 102 d) in a field-based marine environment to study the co-selection of ARGs and microbial communities in marine plastispheres. After the first 63 d of incubation (p < 0.05), the initial 16S rRNA gene abundance of microorganisms in the plastisphere increased significantly, and the biomass subsequently decreased. These results suggest that MPs can serve as vehicles for various microorganisms to travel to different environments and eventually provide a niche for a variety of microorganisms. Additionally, the qPCR results showed that MPs selectively enriched ARGs. In particular, tetA, tetQ, sul1, and qnrS were selectively enriched in the PVC-MPs. The abundances of intl1, a mobile genetic element, was measured in all MP types for 46 d (5.22 × 10-5 ± 8.21 × 10-6 copies/16s rRNA gene copies), 63 d (5.90 × 10-5 ± 2.49 × 10-6 copies/16s rRNA gene copies), and 102 d (4.00 × 10-5 ± 5.11 × 10-6 copies/16s rRNA gene copies). Network analysis indicated that ARG profiles co-occurred with key biofilm-forming bacteria. This study suggests that the selection of ARGs and their co-occurring bacteria in MPs could potentially accelerate their transmission through HGT in natural marine plastics.

Microplastic (MP) occurrence in pelagic and demersal fishes of Gujarat, northwest coast of India

Microplastics (MPs) are globally observed in marine as well as freshwater habitats, and laboratory studies have shown that marine organisms can accidentally ingest them. Monitoring the MP ingestion by fish in the environment is very crucial for understanding the risk of consuming MP-contaminated fish for human health. In this study, we investigated MP ingestion in 400 fish individuals from the Veraval Coast, in the state of Gujarat, India. There was 100% MP occurrence in the inedible tissues of fish, and 68% of the analyzed fishes presented MPs in edible tissues. The most dominant MPs based on their size in fishes were 0.05-0.1 mm. One hundred percent presence of only fibres in edible tissue was observed, while in inedible tissue, it was 77%, 20.42% and 2.58% of fibre, fragment and film respectively. The most common MP colour was blue. The predominant polymers were low-density polyethylene (LDPE) followed by polypropylene, high-density polyethylene (HDPE) and polystyrene. This is the first study performed on MPs in marine fishes from this region. Our findings suggest that the abundance of MPs observed in this area is higher than in other states of the country.

Metagenomics reveals the influence of small microplastics on microbial communities in coastal sediments

The ecological impact of microplastics (MPs) in coastal environments has been widely studied. However, the influence of small microplastics in the actual environment is often overlooked due to measurement challenges. In this study, Hangzhou Bay (HZB), China, was selected as our study area. High-throughput metagenomic sequencing and micro-Raman spectrometry were employed to analyze the microbial communities and microplastics of coastal sediment samples, respectively. We aimed to explore the ecological impact of MPs with small sizes (≤ 100 μm) in real coastal sediment environments. Our results revealed that as microplastic size decreased, the environmental behavior of MPs underwent alterations. In the coastal sediments, no significant correlations were observed between the detected MPs and the whole microbial communities, but small MPs posed potential hazards to eukaryotic communities. Moreover, these small MPs were more prone to microbial degradation and significantly affected carbon metabolism in the habitat. This study is the first to reveal the comprehensive impact of small MPs on microbial communities in a real coastal sediment environment.

Biofilms on plastic litter in an urban river: Community composition and activity vary by substrate type

In aquatic ecosystems, plastic litter is a substrate for biofilms. Biofilms on plastic and natural surfaces share similar composition and activity, with some differences due to factors such as porosity. In freshwaters, most studies have examined biofilms on benthic substrates, while little research has compared the activity and composition of biofilms on buoyant plastic and natural surfaces. Additionally, the influence of substrate size and successional stage on biofilm composition has not been commonly assessed. We incubated three plastics of distinct textures that are buoyant in rivers, low-density polyethylene (rigid; 1.7 mm thick), low-density polyethylene film (flexible; 0.0254 mm thick), and foamed polystyrene (brittle; 6.5 mm thick), as well as wood substrates (untreated oak veneer; 0.6 mm thick) in the Chicago River. Each material was incubated at three sizes (1, 7.5, and 15 cm2 ). Substrates were incubated at 2-10 cm depths and removed weekly for 6 weeks. On each substrate we measured chlorophyll concentration, biofilm biomass, respiration, and flux of nitrogen gas. We sequenced 16S and 23S rRNA genes at Weeks 1, 3, and 6 to capture biofilm community composition across successional stages. Chlorophyll, biomass, and N2 flux were similar across substrates, but respiration was greater on wood than plastics. Bacterial and algal richness and diversity were highest on foam and wood compared to polyethylene substrates. Bacterial biofilm community composition was distinct between wood and plastic substrates, while the algal community was distinct on wood and foam, which were different from each other and polyethylene substrates. These results indicate that polymer properties influence biofilm alpha and beta diversity, which may affect transport and distribution of plastic pollution and associated microbes, as well as biogeochemical processes in urban rivers. This study provides valuable insights into the effects of substrate on biofilm characteristics, and the ecological impacts of plastic pollution on urban rivers. PRACTITIONER POINTS: Plastic physical and chemical properties act as forces of selection for biofilm. Biofilm activity was similar among three different types of plastic. Community composition between plastic and wood was different.

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.

Temporal dynamics of bacterial colonization on five types of microplastics in a freshwater lake

Microplastics (MPs), as a new substrate, provide a unique niche for microbial colonization in the freshwater ecosystems; however, the impacts of long-term MP exposure on colonized bacteria are still unclear. In this study, five MP types were exposed in a freshwater lake for approximately one year, and the MP particles, together with the surrounding water, were collected on days 60, 150, 250 and 330 during the in situ field experiment. Bacteria on the MP surface, as well as free-living bacteria in the surrounding water, were analyzed to evaluate the temporal dynamics of these bacterial communities. Results show that all five MP types exhibited signs of degradation during the exposure process. Additionally, the alpha diversity, community structure and composition of MP-attached bacteria significantly differed from that of the free-living bacteria in the surrounding water, indicating that the five MP types could provide a preferable niche for bacterial colonization in a freshwater environment. Proteobacteria, Chloroflexi, Verrucomicrobiota, Actinobacteriota and Firmicutes were the top five dominant phyla. Some plastic-degrading bacteria included in these phyla were detected, verifying that MP-attached biofilms had a certain degree of MP degradation potential. Some potentially pathogenic bacteria were also detected, suggesting an ecological threat for spreading disease in the aquatic ecosystem. Furthermore, the bacterial community and some metabolic pathways were significantly affected by the MP type (P < 0.01) and exposure time (P < 0.01), indicating that the presence of MPs not only alters the bacterial community structure and composition, but also influences their potential functional properties in freshwater ecosystems. Multiple factors, including the physicochemical properties related to MPs and the environmental parameters of the surrounding water, affect the community composition and the function of MP-attached bacteria to different degrees. Our findings indicate that the presence of MPs has a potential ecological impact on freshwater ecosystems.

Comparison of plastic pollution between waters and sediments in four Po River tributaries (Northern Italy)

The monitoring of plastic contamination in freshwaters is still pioneering in comparison with marine environments, and few studies analyzed the distribution of these pollutants in both aqueous and bottom compartments of continental waters. Therefore, the aim of this study was the comparison of plastic pollution in both waters and sediments of four Po River tributaries (Ticino, Adda, Oglio and Mincio Rivers), which outflow from the main Italian sub-alpine Lakes, in order to establish the strengths and weaknesses of both matrices. The main results pointed out a heterogeneous plastic contamination, with the lowest values in Ticino (0.9 ± 0.5 plastics/m3 in waters and 6.8 ± 4.5 plastics/kg dry weight - d.w. - in sediments) and the highest in Mincio (62.9 ± 53.9 plastics/m3 in waters and 26.5 ± 13.3 plastics/kg d.w in sediments), highlighting a plastic amount in sediments four times higher than waters. Plastic pollution, mainly due to microplastics, was associated principally to a domestic input in both waters and sediments of Ticino and Adda Rivers, as well as in sediments of Oglio, while an industrial pollution was found in waters and sediments of Mincio and Oglio waters. Our data clearly highlighted as the monitoring of both matrices provide complementary information for a holistic risk assessment of these emerging contaminants in freshwaters: the aqueous matrix provides an instantaneous picture of contamination, while sediments the history of pollution.

Realistic microplastics harness bacterial presence and promote impairments in early zebrafish embryos: Behavioral, developmental, and transcriptomic approaches

The plastisphere is a newly recognized ecosystem. However, its interaction with early life stages of aquatic vertebrates is a multifaceted issue that requires further research. This study investigated the involvement of bacteria in shaping realistic microplastics hazards in zebrafish Danio rerio embryos. Fish were exposed to bottle micro-fragments (FR) and textile micro-fibers (FI) of polyethylene terephthalate (5-15 μm), concomitant with Aeromonas salmonicida achromogenes challenge from 2h post-fertilization for 3 days. Egg chorion showed affinity for FR and FI, inducing earlier embryo hatching. However, this effect was masked by biofilm invasion. Fragments were more detrimental than fibers on developmental parameters, while bacterial presence compromised body length, eye, and yolk sac surface area. In a further finding, MPs alone increased locomotor activity in zebrafish larvae, without synergistic effect when combined with bacteria. Data showed that realistic MPs had no significant effects except for downregulated sod and cyp1a gene expression, whereas bacterial challenge inhibited larval potency for most of the evaluated mRNA levels (mpx (immune system), apoeb (lipid metabolism), nfkb and tfa (inflammation), cyp and sod (oxidative stress)). This study provides new insights into realistic microplastic effects under relevant conditions when combined with environmental pathogen within the first life stages of aquatic vertebrates.

Microplastic-specific biofilm growth determines the vertical transport of plastics in freshwater

Understanding the sinking behavior of microplastics in freshwater is essential for assessing their environmental impact, guiding research efforts, and formulating effective policies to mitigate plastic pollution. Sinking behavior is a complex process driven by plastic density, environmental factors and particle characteristics. Moreover, the growth of biological entities on the plastic surface can affect the total density of the microplastics and thus influence the sinking behavior. Yet, our understanding of these processes in freshwater is still limited. Our research thus focused on studying biofilm growth on microplastics in freshwater. Therefore, we evaluated biofilm growth on five different polymer types (both microplastic particles and plates) which were incubated in freshwater for 63 days in a controlled laboratory setting. Biofilm growth (mass-based) was used to compare biofilm growth between polymer types, surface roughness and study the changes over time. Understanding the temporal aspect of biofilm growth enabled us to refine calculations on the predicted effect of biofilm growth on the settling behavior in freshwater. The results showed that biofilm formation is polymer-specific but also affected by surface roughness, with a rougher surface promoting biofilm growth. For PET and PS, biofilm tended to grow exponentially during 63 days of incubation. Based on our calculations, biofilm growth did affect the sinking behavior differently based on the polymer type, size and density. Rivers can function as sinks for some particles such as large PET particles. Nevertheless, for others, the likelihood of settling within river systems appears limited, thereby increasing the probability of their transit to estuarine or oceanic environments under hydrometeorological influences. While the complexity of biofilm dynamics on plastic surfaces is not fully understood, our findings help to elucidate the effect of biofilms on the vertical behavior of microplastics in freshwater systems hereby offering knowledge to interpret observed patterns in environmental plastic concentrations.

Quantifying microplastic dispersion due to density effects

An experimental study was conducted on how polymer density affects the transport and fate of microplastics in aquatic flows. For the first time, polypropylene (PP), polyethylene (PE), polymethyl methacrylate (PMMA), polyetheretherketone (PEEK), and polyvinyl chloride (PVC) were chemically stained and tested using solute transport techniques and velocities found among rivers in the natural environment (0.016 - 0.361 m/s). The movement of 3D-polymers with densities ranging from 0.9 - 1.4 g/cm³ was quantified in a laboratory flume scaled to simulate open-channel flows in fluvial systems. Except for PP, in most conditions microplastics exhibited similar transport characteristics to solutes regardless of density and established solute transport models were successfully implemented to predict their transport and fate. Mass recoveries and ADE routing model demonstrated microplastic deposition and resuspension was associated with polymer density below critical velocity thresholds ≤ 0.1 m/s. When density becomes the dominant force at these slower velocities, concentrations of denser than water microplastics will be momentarily or permanently deposited in channel beds and microplastics follow the classical Shields sediment transport methodology. This data is the first to provide microplastic suspension and deposition thresholds based on river velocity and polymer density, making a key contribution to research predicting microplastic fate and organismal exposure.

Effect of microplastic particles on the population growth rate and clearance rate of selected ciliates (Protista, Ciliophora)

Microplastics (MPs), due to their micro size, which overlaps with the typical food size of various aquatic organisms, can be ingested and move up the food chain, accumulating in the bodies of organisms at higher trophic levels. Few studies have focused on the uptake of MPs by ciliates, which are an important element of the microbial cycle. Three different ciliate species were used in this study: Blepharisma japonicum, Euplotes sp., and Spirostomum teres, as well as polystyrene beads with diameters of 1 and 2 µm at two concentrations (106 and 107 beads × mL-1). The results of the experiments showed that MPs have a variable, species-specific effect on the population growth rate of ciliates, which is directly dependent on their concentration in the environment (P < 0.01). It was also observed that the number of MPs ingested changed over time depending on their concentration and size. On average, the highest number of ingested MPs (883.11 ± 521.47) was recorded at 60 min of exposure to a low concentration of small beads in B. japonicum. The lowest number of beads was ingested after 5 min of exposure to a low concentration of large beads in the same species. The rate of MP uptake by the ciliate species was significantly dependent on their concentration, exposure time, and size (P < 0.001). The highest clearance rate was observed in the fifth minute of the experiment in the environment with the lowest MP concentration.

Microbes and microplastics: Community shifts along an urban coastal contaminant gradient

Plastic substrates introduced to the environment during the Anthropocene have introduced new pathways for microbial selection and dispersal. Some plastic-colonising microorganisms have adapted phenotypes for plastic degradation (selection), while the spatial transport (dispersal) potential of plastic colonisers remains controlled by polymer-specific density, hydrography and currents. Plastic-degrading enzyme abundances have recently been correlated with concentrations of plastic debris in open ocean environments, making it critical to better understand colonisation of hydrocarbon degraders with plastic degradation potential in urbanised watersheds where plastic pollution often originates. We found that microbial colonisation by reputed hydrocarbon degraders on microplastics (MPs) correlated with a spatial contaminant gradient (New York City/Long Island waterways), polymer types, temporal scales, microbial domains and putative cell activity (DNA vs. RNA). Hydrocarbon-degrading taxa enriched on polyethylene and polyvinyl chloride substrates relative to other polymers and were more commonly recovered in samples proximal to New York City. These differences in MP colonisation could indicate phenotypic adaptation processes resulting from increased exposure to urban plastic runoff as well as differences in carbon bioavailability across polymer types. Shifts in MP community potential across urban coastal contaminant gradients and polymer types improve our understanding of environmental plastic discharge impacts toward biogeochemical cycling across the global ocean.

Plankton assemblages from microplastics of tropical coastal environments reveal high diversity and evidence of toxic species

Microplastics are a major constituent of plastic waste and are of an increasing global concern. Although microplastics are prevalent in marine ecosystems, the characterisation of plankton communities has been largely neglected in this aspect, especially in tropical ecosystems. To better understand the role of microplastics as a carrier of harmful plankton in marine ecosystems, epiplastic plankton communities in tropical marine ecosystems were studied from beach sediments along the Johor and Singapore Straits. Complementary analysis of microscopy and high throughput sequencing of the 16S rRNA (V3-V4) and 18S (V4) rRNA regions provided evidence that the plastisphere provided an appropriate environment to host a wide range of planktonic organisms. An average of 781 OTUs were identified across the three sampling sites. The structures of plankton communities were distinct across the sampling sites and were generally dominated by dinoflagellates, fungi and chlorophytes. We demonstrate that marine microplastics serve as microhabitats that are a host to harmful phytoplankton species, including viable resting cysts of dinoflagellates. Furthermore, plastics isolated from the location with the greatest anthropogenic influence demonstrated the greatest plankton diversity. This study presents evidence of diverse toxic plankton species present on the plastisphere and highlights its importance as a vector of the transport of harmful opportunistic species in relation to anthropogenic influence, in the marine environment.

Impacts of net cages on pollutant accumulation and its consequence on antibiotic resistance genes (ARGs) dissemination in freshwater ecosystems: Insights for sustainable urban water management

There has been increasing interest in the role of human activities in disseminating antibiotic-resistance genes (ARGs) in aquatic ecosystems. However, the influence of pollutant accumulation on anthropogenic pollutant-ARG synergistic actions is limited. This study explored the association of net cages with the propagation of anthropogenic pollutants and their consequences for influencing the enrichment of ARGs using high-throughput metagenomic sequencing. We showed that net cages could substantially impact the ecology of freshwater systems by enhancing i) ARG diversity and the tendency for ARG-horizontal gene transfer and ii) the overlap of mobile genetic elements (MGEs) with biocide-metal resistance genes (BMRGs) and ARGs. These findings suggested that the cotransfer of these three genetic determinants would be favored in net cage plots and that nonantibiotic factors such as metal(loid)s, particularly iron (Fe), displayed robust selective pressures on ARGs exerted by the net cage. The resistome risk scores of net cage sediments and biofilms were higher than those from off-net cage plots, indicating that the net cage-origin antibiotic resistome should be of great concern. The combination of deterministic and stochastic processes acting on bacterial communities could explain the higher ARG variations in cage plots (8.2%) than in off-cage plots (3.4%). Moreover, MGEs and pollutants together explained 43.3% of the total variation in ARG communities, which was higher than that of off-cage plots (8.8%), considering pollutants, environmental variables, MGEs, and assembly processes. These findings will inform the development of policies and guidelines to more effectively limit the spread of antimicrobial resistance and achieve the goal of sustainability in freshwater systems in urban areas.

The effect of polyvinyl chloride (PVC) color on biofilm development and biofilm-heavy metal chemodynamics in the aquatic environment

Plastic surfaces are colonized by microorganisms and biofilms are formed in the natural aquatic environment. As the biofilm develops, it changes the density and buoyancy of the plastic-biofilm complex, results in plastic sinking, and increases the heavy metals accumulated by biofilm's mobility and availability in aquatic ecosystems. In this experiment, biofilms were cultured on five colors of polyvinyl chloride (PVC; transparent, green, blue, red, black) in an aquatic environment to investigate the effects of plastic color on biofilm formation and development (Phase 1) and to study the effects of being sunk below the photic zone on biofilm (Phase 2). The PVC color significantly affected the biofilm formation rate but had no impact on the final biofilm biomass. After sinking the biofilm-PVC below the photic zone in Phase 2, the layer of diatoms on the biofilm surface began to disintegrate, and the biomass and Chlorophyll-a (Chla) content of the biofilm decreased, except on the red PVC. Below the photic zone, the microbial community of the biofilm changed from primarily autotrophic microbes to mostly heterotrophic microbes. Microbial diversity increased and extracellular polymeric substances (EPS) content decreased. The primary factor leading to microbial diversity and community structure changes was water depth rather than PVC color. The changes induced in the biofilm led to an increase in the concentration of all heavy metals in the biofilm, related to the increase in microbial diversity. This study provides new insights into the biofilm formation process and the effects on a biofilm when it sinks below the photic zone.

Zooplankton as a suitable tool for microplastic research

In recent years, significant efforts have been dedicated to measuring and comprehending the impact of microplastics (MPs) in the ocean. Despite harmonization guidelines for MPs research, discrepancies persist in the applied methodologies and future challenges, mostly for the smaller fractions (< 100 μm). Whether intentional or accidental, ingesting plastic particles by zooplankton can lead to incorporating this pollutant into aquatic food chains. Therefore, zooplankton can serve as a suitable proxy tool for assessing the presence of plastic particles in ocean waters. However, reliable information is essential for conducting experimental laboratory studies on the impact of MPs ingestion by zooplankton organisms. Using zooplankton as a research tool for MPs offers numerous advantages, including similar sampling methodologies and study techniques as MPs and particle data integration over space and time. The scientific community can gain novel perspectives by merging zooplankton studies with MPs research. This review explores key aspects of using zooplankton as a tool for MPs research in water samples, encompassing various views such as particles ingestion in natural environments, particle quantification in zooplankton samples (past and future), ecotoxicological and toxicology model studies. By leveraging the potential of zooplankton research, advancements can be made in developing innovative techniques for MPs analysis.

Degradation and lifetime prediction of plastics in subsea and offshore infrastructures

Engineering and civil developments have relied on synthetic polymers and plastics (including polyethylene, polypropylene, polyamide, etc.) for decades, especially where their durability protects engineering structures against corrosion and other environmental stimuli. Offshore oil and gas infrastructure and renewable energy platforms are typical examples, where these plastics (100,000 s of metric tonnes worldwide) are used primarily as functional material to protect metallic flowlines and subsea equipment against seawater corrosion. Despite this, the current literature on polymers is limited to sea-surface environments, and a model for subsea degradation of plastics is needed. In this review, we collate relevant studies on the degradation of plastics and synthetic polymers in marine environments to gain insight into the fate of these materials when left in subsea conditions. We present a new mathematical model that accounts for various physicochemical changes in the oceanic environment as a function of depth to predict the lifespan of synthetic plastics and the possible formation of plastic debris, e.g., microplastics. We found that the degradation rate of the plastics decreases significantly as a function of water depth and can be estimated quantitatively by the mathematical model that accounts for the effect (and sensitivity) of geographical location, temperature, light intensity, hydrostatic pressure, and marine sediments. For instance, it takes a subsea polyethylene coating about 800 years to degrade on ocean floor (as opposed to <400 years in shallow coastal waters), generating 1000s of particles per g of degradation under certain conditions. Our results demonstrate how suspended sediments in the water column are likely to compensate for the decreasing depth-corrected degradation rates, resulting in surface abrasion and the formation of plastic debris such as microplastics. This review, and the complementing data, will be significant for the environmental impact assessment of plastics in subsea infrastructures. Moreover, as these infrastructures reach the end of their service life, the management of the plastic components becomes of great interest to environmental regulators, industry, and the community, considering the known sizeable impacts of plastics on global biogeochemical cycles.

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.

Microplastic Effect Tests Should Use a Standard Heterogeneous Mixture: Multifarious Impacts among 16 Benthic Invertebrate Species Detected under Ecologically Relevant Test Conditions

Microplastics require a risk assessment framework that takes their multidimensionality into account while exclusively considering robust data. Therefore, effect tests should use a diverse, environmentally relevant microplastic (ERMP) standard material that adheres to high-quality requirements. In this study, we provide chronic dose-effect relationships and effect thresholds for 16 benthic species exposed to ERMP. The ERMP was created from plastic items collected from natural sources and cryogenically milled to represent the diversity of microplastics. The test design met 20 previously published quality assurance and quality control criteria. Adverse effect thresholds (EC10) were determined at ERMP concentrations of 0.11 ± 0.17% sediment dry weight (Gammarus pulex, growth), 0.49 ± 0.68% sediment dry weight (Lumbriculus variegatus, growth), and 1.90 ± 1.08% sediment dry weight (L. variegatus, reproduction). A positive effect of microplastics, such as decreased mortality, was observed for Cerastoderma edule (EC10 = 0.021 ± 0.027% sediment dry weight) and Sphaerium corneum (EC10 = 7.67 ± 3.41% sediment dry weight), respectively. Several of these laboratory-based single-species effect thresholds for ERMP occurred at concentrations lower than those found in the environment. For other species, no significant effects were detected up to an ERMP dose of 10% dry weight.