Microplastics in a freshwater mussel (Anodonta anatina) in Northern Europe

Tracking the microplastic pollution in the freshwater environments of southeastern Türkiye: Usage of Unio delicatus, Unio Terminalis and Dreissena polymorpha as bioindicators of microplastics

Microplastic (MP) pollution levels in aquatic environments raise concerns regarding the potential harm to biota and the environment. Mussel species are categorized as perfect bioindicator of pollutants due to their sessile lifestyle, and filter-feeding activity that also make them more prone to microplastic contamination. This study was designed to assess microplastic pollution levels in the soft tissues of dominant freshwater mussel species to understand general picture in microplastic contamination of the ambient environment. For that purpose, microplastic presence in the soft tissue of Unio delicatus (n:49), Unio Terminalis (n:31) and Dreissena polymorpha (n:82) was investigated. Including all examined specimens, mean microplastic abundance was found as 0.6 ± 0.8 items/ind, 0.2 ± 0.5 items/g ww with occurrence rate of 48 %. Reflecting global distribution, general morphological characteristics of MPs were fiber shape, blue colored and less than 500 μm in size. Fourier transform infrared (FTIR) spectroscopy identified the polymer type of MPs as polyethylene (40 %), polypropylene (47 %), and polystyrene (27 %). The results obtained in this study provide baseline information regarding microplastic contamination in freshwater environments and emphasize the need of protective measures.

Promotion of microplastic degradation on the conjugative transfer of antibiotic resistance genes in the gut of macrobenthic invertebrates

Microplastics and antibiotic resistance genes are two new pollutants in water environments, and they have potential risks to human health and ecological safety. On the basis of the accumulation of pollutants and microorganisms in sediment, macrobenthic invertebrates are considered as potential practitioners of microplastic degradation and antibiotic resistance gene (ARG) transfer. However, whether microplastic degradation can affect ARG transfer in aquatic environments, especially in the gut of macrobenthic invertebrates, remains unclear. In this study, we demonstrated that microplastics including polyethylene terephthalate (PET), polyvinyl chloride(PVC), polyamide (PA), polystyrene (PS), polypropylene (PP), polyethylene (PE), and polyurethane (PU), and ARGs including tetA, sul1, sul2, and sul3 were widely distributed in sediment and benthic invertebrates in Nansi lake. The distribution of ARGs was related to the number and size of microplastic particles. In particular, it was found for the first time that the content of ARGs corresponding to individual particles was linearly and negatively correlated with the size of microplastics. The results of animal feeding experiments showed that microplastic degradation in the gut of Chironomidae larvae could promote the conjugative transfer of ARGs. The underlying molecular mechanism was SOS response. This study provides a new method for the analysis of the interaction effect of multiple pollutants in freshwater environments.

Spatial patterns of microplastics in freshwater bivalves (Bivalvia: Unionidae and Sphaeriidae) relative to municipal wastewater effluent discharges

Microplastics are discharged by municipal wastewater treatment plants (WWTPs); however, their uptake by filter-feeding freshwater bivalves is poorly understood. This study examined the abundance and characteristics of microplastics in wild bivalves from five locations along a 155 km stretch of the Grand River (Ontario, Canada) in 2021-2022, including upstream and downstream of three municipal WWTPs. At each site, fingernail clams (Sphaeriidae spp., n = 5 composites), freshwater mussels (Lasmigona costata, n = 10; gill, digestive gland, and hemolymph), and surface water (n = 3) were sampled at a single timepoint. Microplastics (particles >38 μm to 5 mm) were isolated and visualized via stereomicroscopy, and a subset chemically analyzed using Fourier transform infrared spectroscopy. Fingernail clams contained the highest total blank corrected microparticle counts (35.5 ± 29.4 g-1 [mean ± SD]), mussel tissues ranged from 4.3 ± 4.2 mL-1 in hemolymph to 6.5 ± 8.1 g-1 in digestive gland, and water contained 5.5 ± 2.8 L-1. Fibers were the dominant morphology across all samples, most particles were between 80 μm and 2 mm in length and, of those analyzed chemically, 30.0% were a plastic polymer. At sites downstream of WWTP outfalls, elevated counts were only seen in mussel gills and not in other bivalve tissues or water compared with upstream samples. Although microplastics were found across all sites in both biotic and abiotic compartments, results suggest little impact of WWTP discharges on their uptake in downstream bivalves.

Microplastic accumulation in various bird species in Turkey

Plastic pollution constitutes one of the major environmental problems of our time, and in recent years, it has emerged as a significant threat to the environment and to various organisms, including bird species. In this context, this study, which provides the first data in Türkiye, aimed to determine the level of microplastic (MP) pollution in 12 bird species (Eurasian buzzard; short-toed snake-eagle; white stork; northern long-eared owl; common barn-owl; ruddy shelduck; Eurasian eagle-owl; scarlet macaw; common pheasant; Indian peafowl; common kestrel; and gray parrot). The results indicate that MPs were detected in 50% of the specimens (n = 20), with an average of one MP/item per individual. With an average of three MPs per individual, the short-toed snake-eagle was found to be the species with the highest MP accumulation. Fibers (range: 51-534 µm) were the most common type of plastic found in the gastrointestinal tract of birds, with ethylene vinyl acetate and navy blue being the most common polymer type and color, respectively. It was also found that the abundance of MPs increased with the weight of specimens, contributing to the hypothesis that there is a correlation between the size/weight of animals and increased levels of MP accumulation. These findings highlight the impact of plastic pollution on birdlife and the need for further monitoring to assess the ecological impact of pollution.

Quantifying Effects and Ingestion of Several Pristine Microplastics in Two Early Life Stages of Freshwater Mussels

Microplastics have been found in freshwater systems, and in turn have been detected in freshwater bivalves. However, there is limited research that defines the toxicity of bicroplastics to native freshwater bivalves that have long been imperiled in North America. Our objective was to determine whether a suite of pristine microplastics has an adverse effect on two early life stages of unionid freshwater mussels. Glochidia of Lampsilis fasciola (a Canadian species at risk) and Lampsilis siliquoidea (widespread across Canada) were individually exposed to spheres of polystyrene (6 and 90 μm), polyethylene (28, 90, and 1000 μm), and cellulose acetate (1000 μm), as well as fibers of polyethylene terephthalate (60 μm). After 24 h, there was no significant decrease in glochidia viability in either species. Juvenile L. siliquoidea mussels were also exposed to spheres of polystyrene (6 and 90 μm) and polyethylene (28 μm), and fibers of polyethylene terephthalate (60 μm) in individual 28-day subchronic tests followed by a 7-day depuration period. Burial was assessed weekly, and ingestion of each microplastic was compared in nondepurated and depurated mussels. There was no sustained effect on juvenile burial with any microplastic tested. Ingestion of microplastics was concentration dependent, and depuration occurred for all particles and size ranges tested. The results suggest that pristine microplastics were not acutely toxic to the early life stages of these freshwater mussels, but that the energetic costs associated with particle uptake and depuration, which were not measured in our study, may have an impact on fitness that warrants further investigation. In addition, testing with other shapes and polymers of microplastics typically detected in the environment is recommended. Environ Toxicol Chem 2024;43:2557-2568. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Biological hazards of micro- and nanoplastic with adsorbents and additives

With the increased worldwide production of plastics, interest in the biological hazards of microplastics (MP) and nanoplastics (NP), which are widely distributed as environmental pollutants, has also increased. This review aims to provide a comprehensive overview of the toxicological effects of MP and NP on in vitro and in vivo systems based on studies conducted over the past decade. We summarize key findings on how the type, size, and adsorbed substances of plastics, including chemical additives, impact organisms. Also, we address various exposure routes, such as ingestion, inhalation, and skin contact, and their biological effects on both aquatic and terrestrial organisms, as well as human health. Additionally, the review highlights the increased toxicity of MP and NP due to their smaller size and higher bioavailability, as well as the interactions between these particles and chemical additives. This review emphasizes the need for further research into the complex biological interactions and risks posed by the accumulation of MP and NP in the environment, while also proposing potential directions for future studies.

Microplastic ingestion in mussels from the East Mediterranean Sea: Exploring its impacts in nature and controlled conditions

Microplastic ingestion poses a significant concern for a plethora of marine organisms due to its widespread presence in marine ecosystems. Despite growing scientific interest, the effects on marine biota are not yet well understood. This study investigates the ingestion of microplastics (MPs) by mussels from various marine environments and assesses the associated effects that can be induced by MPs and associated toxic chemicals. Biomarkers of oxidative stress (catalase, lipid peroxidation), biotransformation (glutathione S-transferase), genotoxicity (micronuclei frequency) and neurotoxicity (acetylcholinesterase) were employed. Mussels, considered reliable bioindicators of MPs pollution, were sampled by hand from diverse locations under varied anthropogenic pressures, including a highly touristic Marine Protected Area (MPA) in the Ionian Sea, a mussel farm and a fish farm in the Aegean Sea. The results revealed the highest MP ingestion in mussels from the fish farm [0.21 ± 0.04 (SE) MPs/g or 0.63 ± 0.12 (SE) MPs/Ind.], likely due to plastic aquaculture equipment use. Stereoscopic observation revealed fibers, as the predominant shape of ingested MPs across all sites, and μFTIR polymer identification revealed the presence of various types, with polyethylene (PE) and polyamide (PA) being the most abundant. Significant physiological alterations in mussels related to MP ingestion levels were observed through biomarkers indicative of oxidative stress and biotransformation, as well as the Integrated Biomarker Response (IBR index). However, laboratory experiments with mussels exposed to controlled increasing PE concentrations for four weeks, did not show significant effects triggered by the PE ingestion, possibly indicating other environmental factors, such as contaminants from aquaculture environments, may influence biomarker levels in the field. Despite the observed effects, MP ingestion rates in mussels from the field were relatively low compared to other studies. Future research should continue to investigate the interactions between MPs and marine organisms in diverse environments to better understand and mitigate their impacts.

Microplastic contamination of intertidal sediment and cockles (Cerastoderma edule)

Microplastic pollution represents a new threat to both marine environments and the species that reside within them. This study examined the temporal concentrations of microplastics found in the commercially and ecologically important bivalve, Cerasastoderma edule and the presence of microplastics in intertidal sediment from the Special Area of Conservation (SAC) and Special Protected Area (SPA) of Dundalk Bay, Ireland. A microplastic range of 1.55 ± 1.38 to 1.92 ± 1.00 g-1 and 3.43 ± 2.47 to 6.90 ± 3.68 ind-1 was reported between seasons. Microfibres dominated the shape of microplastics present in both sediment and cockles. While a wider range of polymers were identified in cockles than in sediment, microplastic concentrations recovered from both intertidal sites studied were approximately double the estimated safe loading levels for this pollutant. The potential of cockles to perform as shallow environment biomonitors of microplastic pollution was identified as they presented buoyant microplastics that were not identified in sediment samples.

Probing Long-Term Impacts: Low-Dose Polystyrene Nanoplastics Exacerbate Mitochondrial Health and Evoke Secondary Glycolysis via Repeated and Single Dosing

Nanoplastics (NPs) are omnipresent in the environment and contribute to human exposure. However, little is known regarding the long-term effects of NPs on human health. In this study, human intestinal Caco-2 cells were exposed to polystyrene nanoplastics (nanoPS) in an environmentally relevant concentration range (102-109 particles/mL) under two realistic exposure scenarios. In the first scenario, cells were repeatedly exposed to nanoPS every 2 days for 12 days to study the long-term effects. In the second scenario, only nanoPS was added once and Caco-2 cells were cultured for 12 days to study the duration of the initial effects of NPs. Under repeated dosing, initial subtle effects on mitochondria induced by low concentrations would accrue over consistent exposure to nanoPS and finally lead to significant impairment of mitochondrial respiration, mitochondrial mass, and cell differentiation process at the end of prolonged exposure, accompanied by significantly increased glycolysis over the whole exposure period. Single dosing of nanoPS elicited transient effects on mitochondrial and glycolytic functions, as well as increased reactive oxygen species (ROS) production in the early phase of exposure, but the self-recovery capacity of cells mitigated these effects at intermediate culture times. Notably, secondary effects on glycolysis and ROS production were observed during the late culture period, while the cell differentiation process and mitochondrial mass were not affected at the end. These long-term effects are of crucial importance for comprehensively evaluating the health hazards arising from lifetime exposure to NPs, complementing the extensively observed acute effects associated with prevalent short-term exposure to high concentrations. Our study underlines the need to study the toxicity of NPs in realistic long-term exposure scenarios such as repeated dosing.

Using marine mussels to assess the potential ecotoxicological effects of two different commercial microplastics

Microplastics (MPs) in the aquatic environment pose a serious threat to biota, by being confounded with food. These effects occur in mussels which are filter-feeding organisms. Mussels from the genus Mytilus sp. were used to evaluate the ecotoxicological effects of two MPs, polypropylene (PP) and polyethylene terephthalate (PET), after 4 and 28-days. Measured individual endpoints were condition index and feeding rate; and sub-individual parameters, metabolism of phase I (CYP1A1, CYP1A2 and CYP3A4) and II (glutathione S-transferases - GSTs), and antioxidant defense (catalase - CAT). MPs decreased both condition index (CI) and feeding rate (FR). No alterations occurred in metabolic enzymes, suggesting that these MPs are not metabolized by these pathways. Furthermore, lack of alterations in GSTs and CAT activities suggests the absence of conjugation and oxidative stress. Overall, biochemical markers were not responsive, but non-enzymatic responses showed deleterious effects caused by these MPs, which may be of high ecological importance.

Understanding microplastic pollution of marine ecosystem: a review

Microplastics are emerging as prominent pollutants across the globe. Oceans are becoming major sinks for these pollutants, and their presence is widespread in coastal regions, oceanic surface waters, water column, and sediments. Studies have revealed that microplastics cause serious threats to the marine ecosystem as well as human beings. In the past few years, many research efforts have focused on studying different aspects relating to microplastic pollution of the oceans. This review summarizes sources, migration routes, and ill effects of marine microplastic pollution along with various conventional as well as advanced methods for microplastics analysis and control. However, various knowledge gaps in detection and analysis require attention in order to understand the sources and transport of microplastics, which is critical to deploying mitigation strategies at appropriate locations. Advanced removal methods and an integrated approach are necessary, including government policies and stringent regulations to control the release of plastics.

Microplastics in aquatic ecosystems of Africa: A comprehensive review and meta-analysis

Microplastic pollution is a global issue of great public concern. Africa is flagged to host some of the most polluted water bodies globally, but there is no enough information on the extent of microplastic contamination and the potential risks of microplastic pollution in African aquatic ecosystems. This meta-analysis has integrated data from published articles about microplastic pollution in African aquatic ecosystems. The data on the microplastic distribution and morphological characteristics in water, sediments and biota from African rivers, lakes, oceans and seas were extracted from 75 selected studies. Multivariate statistics were used to critically analyze the effects of sampling and detection methods, ecological risks, spatial distribution and similarity of microplastics in relation to the geographical distance between sampling sites. This study found that sampling methods have significant effect on abundance and morphological characteristics of microplastics and that African aquatic ecosystems are highly contaminated with microplastics compared to global data. The most prevalent colors were white, transparent and black, the most prevalent shapes were fibres and fragments, and the most available polymers were polypropylene (PP), polystyrene (PS) and polyethene terephthalate (PET). Microplastic polymers similarity decreased with an increase in geographical distance between sites. Risk levels of microplastics in African aquatic ecosystems were comparatively high, and more than 40 % of water and sediments showed highest level of ecological risk. This review provides recent information on the prevalence, distribution and risks of microplastics in African aquatic ecosystems.

Microplastics in the River Ganga and its fishes: Study of a Himalayan River

The River Ganga has been explored for microplastics (MPs) majorly in the lower or middle course, while the upper course from where the river starts its journey remains untouched. This study investigates the occurrence and distribution of MPs in the river environment (water and sediment) and common fishes inhabiting the upper stretch of River Ganga in the Uttarakhand state of India. A volume-reduce method by using sieve filtration was used to take water and sediment samples from the study area while fish samples were collected using net method. The samples underwent alkali digestion, microscopic examination, and chemical analysis using Fourier Transformed Infrared Spectroscopy (FTIR). An average of 118.5 ± 49.65 particles per 1000 L and 131.5 ± 53.60 particles/kg dry weight were found in water and sediment respectively. While in the fishes, Tor tor, Schizothorax richardsonii, Labeo dero and Gara gotyla gotyla MPs were 53.13 ± 63.77, 36.33 ± 22.34, 15.42 ± 9.33 and 12.63 ± 5.93 particles/individual respectively. A positive correlation was observed between the number of MPs in fish and their body length, weight, and gut weight, while no correlation was found between feeding habit and MP accumulation. The majority of MPs detected were fibers ranging from 100 μm to 1 mm in size. Polymer types varied among water, sediment, and fish samples, with polyethylene (PE) predominant in water, polypropylene (PP) dominant in sediment, and polyethylene terephthalate (PET) and polystyrene (PS) most abundant in fish samples.

Size-selective microplastic uptake by freshwater organisms: Fish, mussel, and zooplankton

Microplastics, as an emergent pollutant, have garnered substantial attention within aquatic environments, yet a significant knowledge gap persists regarding the interplay of organism size and pollution impacts on microplastic uptake in freshwater ecosystems. The main aim of the current study is to assess the microplastic ingestion by aquatic organisms across diverse trophic levels. To achieve this objective, zooplankton, mussels (Anodonta anatina), and fish (Carassius gibelio) were collected from the highly polluted Susurluk River Basin in Türkiye. The size distribution encompassed 160.8 ± 56.9 μm for the prevailing zooplankton, 6.9 ± 2.2 cm for mussel, and 20.4 ± 3.1 cm for fish, respectively. While no microplastic ingestion was observed among zooplankton, the finding highlights the influence of body-size and pollution on microplastic ingestion. In contrast, A. anatina and C. gibelio contained 617 and 792 microplastic particles, respectively. Predominantly, fibers emerged as the most prevalent microplastic type across trophic levels (except zooplankton) followed by films. Notably, only fish exhibited fragments within their gastrointestinal tract. A substantial correlation emerged between microplastic abundance and mussel size and weight, but no such correlation manifested for fish. The study also revealed a positive link between microplastic count and turbidity (phosphate and high Chl a level), impacting mussel ingestion capacity due to the variability in the food availability and potential shifts in feeding preferences. Conversely, no distinct pattern emerged for fish concerning water quality parameters and ingested microplastics. Consequently, our study underscores diverse microplastic uptake patterns in freshwater ecosystems, with a predominant frequency of microplastics falling with the 0.3 mm-3.0 mm range, emphasizing the significance of size-selective uptake by organisms.

Characteristics and seasonal variation of microplastics in the wastewater treatment plant: The case of Bursa deep sea discharge

Microplastics (MPs) are an emerging pollutant that can be detected in all ecosystems, especially aquatic ecosystems. Wastewater treatment plants (WWTPs) are important point sources of MP release into the sea. In this study, the characteristics of MPs in wastewater and sludge samples taken from different units of WWTP in Bursa-Gemlik district for 12 months were investigated. Wastewater and sludge samples collected from 7 different points were classified as size, shape, color, and counted. The amount of MP in the influent and effluent of the WWTP, respectively; 107.1 ± 40.2 MP/L and 4.1 ± 1.1 MP/L. Although the MP removal efficiency of the WWTP is 96.17 %, approximately 74,825,000 MP is discharged into the Marmara Sea every day. The amount of MP in the sludge is 14.3 ± 7.1 MP/g. The amount of MP accumulated in 22tons of waste sludge formed daily in WWTP was calculated as 314,600,000 MP, and the annual accumulated amount was calculated as approximately 1.15 × 1011 MP. The MPs in the WWTP were mainly 1-0.5 mm in size. Fibers were the dominant MP shape in both the wastewater and sludge samples. Black and transparent were the dominant MP colors. Seven different polymer types of MPs were detected, which were mainly types of polyethylene, polypropylene, and polyethylene terephthalate. Despite the high removal efficiency in the investigated WWTP, it has been shown that it acts as an important source of MPs to the sea ecosystem due to the high discharge rates.

The impact of amine and carboxyl functionalised microplastics on the physiology of daphnids

Plastic waste is considered a major threat for terrestrial, marine and freshwater ecosystems. Ingestion of primary or secondary microparticles resulting from plastic degradation can lead to their trophic transfer raising serious health concerns. In this study, the effect of amine and carboxy functionalized polystyrene microparticles on the physiology of daphnids was investigated with a combination of phenotypic and metabolic endpoints. Carboxy functionalized microparticles showed higher toxicity in acute exposures compared to their amine counterparts. Accumulation of both microparticles in animal gut was confirmed by stereo-microscopy as well as fluorescent microscopy which showed no presence of particles in the rest of the animal. Fluorescence based quantification of microparticles extracted from animal lysates validated their concentration-dependent uptake. Additionally, exposure of daphnids to amine and carboxy functionalized microparticles resulted in increased activities of key enzymes related to metabolism and detoxification. Finally, significant metabolic perturbations were discovered following exposure to microplastics. These findings suggest that polystyrene microparticles can hinder organism performance of the freshwater species and highlight the importance of seeking for holistic and physiological endpoints for pollution assessment.

Microplastic pollution in riverine ecosystems: threats posed on macroinvertebrates

Microplastics (MPs) are pollutants of emerging concern that have been reported in terrestrial and aquatic ecosystems as well as in food items. The increasing production and use of plastic materials have led to a rise in MP pollution in aquatic ecosystems. This review aimed at providing an overview of the abundance and distribution of MPs in riverine ecosystems and the potential effects posed on macroinvertebrates. Microplastics in riverine ecosystems are reported in all regions, with less research in Africa, South America, and Oceania. The abundance and distribution of MPs in riverine ecosystems are mainly affected by population density, economic activities, seasons, and hydraulic regimes. Ingestion of MPs has also been reported in riverine macroinvertebrates and has been incorporated in caddisflies cases. Further, bivalves and chironomids have been reported as potential indicators of MPs in aquatic ecosystems due to their ability to ingest MPs relative to environmental concentration. Fiber and fragments are the most common types reported. Meanwhile, polyethylene, polypropylene, polystyrene, polyethylene terephthalate (polyester), polyamide, and polyvinyl chloride are the most common polymers. These MPs are from materials/polymers commonly used for packaging, shopping/carrier bags, fabrics/textiles, and construction. Ingestion of MPs by macroinvertebrates can physically harm and inhibit growth, reproduction, feeding, and moulting, thus threatening their survival. In addition, MP ingestion can trigger enzymatic changes and cause oxidative stress in the organisms. There is a need to regulate the production and use of plastic materials, as well as disposal of the wastes to reduce MP pollution in riverine ecosystems.

Toxicity and Biodistribution of Fragmented Polypropylene Microplastics in ICR Mice

Currently, polypropylene (PP) is used in various products, thus leading to high daily exposure in humans. Thus, it is necessary to evaluate the toxicological effects, biodistribution, and accumulation of PP microplastics in the human body. In this study, administration of two particle sizes of PP microplastics (approximately 5 and 10-50 µm) did not lead to any significant changes in several toxicological evaluation parameters, including body weight and pathological examination, compared with the control group in ICR mice. Therefore, the approximate lethal dose and no-observed-adverse-effect level of PP microplastics in ICR mice were established as ≥2000 mg/kg. Furthermore, we manufactured cyanine 5.5 carboxylic acid (Cy5.5-COOH)-labeled fragmented PP microplastics to monitor real-time in vivo biodistribution. After oral administration of the Cy5.5-COOH-labeled microplastics to the mice, most of the PP microplastics were detected in the gastrointestinal tract and observed to be out of the body after 24 h in IVIS Spectrum CT. Therefore, this study provides a new insight into the short-term toxicity, distribution, and accumulation of PP microplastics in mammals.

Freshwater mussel conservation: A global horizon scan of emerging threats and opportunities

We identified 14 emerging and poorly understood threats and opportunities for addressing the global conservation of freshwater mussels over the next decade. A panel of 17 researchers and stakeholders from six continents submitted a total of 56 topics that were ranked and prioritized using a consensus-building Delphi technique. Our 14 priority topics fell into five broad themes (autecology, population dynamics, global stressors, global diversity, and ecosystem services) and included understanding diets throughout mussel life history; identifying the drivers of population declines; defining metrics for quantifying mussel health; assessing the role of predators, parasites, and disease; informed guidance on the risks and opportunities for captive breeding and translocations; the loss of mussel-fish co-evolutionary relationships; assessing the effects of increasing surface water changes; understanding the effects of sand and aggregate mining; understanding the effects of drug pollution and other emerging contaminants such as nanomaterials; appreciating the threats and opportunities arising from river restoration; conserving understudied hotspots by building local capacity through the principles of decolonization; identifying appropriate taxonomic units for conservation; improved quantification of the ecosystem services provided by mussels; and understanding how many mussels are enough to provide these services. Solutions for addressing the topics ranged from ecological studies to technological advances and socio-political engagement. Prioritization of our topics can help to drive a proactive approach to the conservation of this declining group which provides a multitude of important ecosystem services.

Microplastic pollution in small rivers along rural-urban gradients: Variations across catchments and between water column and sediments

The aquatic ecosystems of the world are highly burdened with microplastics (MPs; particles <5 mm). There is a great need for better understanding of patterns of MP pollution across catchments and rivers of different sizes, anthropogenic pressures and hydrogeomorphological features. In this study, we investigated the MP concentrations including their characteristics (polymer type, shape, size and colour), and MP distribution in water and sediments of two hydrogeomorphologically different small-scale catchments (< 800 km²), namely Kamniška Bistrica (KB) and Ljubljanica (LJ), Slovenia. The main objective of this study was to gain a better understanding of how WWTP effluents and catchment urbanisation together with the diversity of natural hydrogeomorphology, affect the quantity and quality of MP pollutants in the rivers with smaller catchments. Significantly different mean MP concentrations were found in the water columns (KB: 59 ± 16 items m^-3; LJ: 31 ± 14 items m^-3), but not in the sediments (KB: 22 ± 20 items kg^-1; LJ: 23 ± 25 items kg^-1). A longitudinal gradient with increasing particle concentration was observed in both water and sediment samples and in both catchments. Polyethylene (PE) and polypropylene (PP) particles dominated in all samples. Fibres were predominant in the water column samples, while fragments were more common in the sediment samples. MP particles were mostly coloured, and most of them were smaller than 2 mm in both water and sediment samples. The critical evaluation of the results and previous studies suggest that the characteristics of the catchment (anthropogenic pressures, size, climate, etc.), the hydrogeomorphology of the river (sediment type, discharge, flow velocity etc.), the sampling location along the river, the sampled compartment (water, sediment), the sampling method, and the hydrometeorological characteristics at the time of sampling, are important factors for observed MP concentrations and other characteristics.

Microplastic in freshwater ecosystem: bioaccumulation, trophic transfer, and biomagnification

Plastic wastes in the environment ultimately reach to the aquatic habitats and become available to aquatic organisms. The pathway of microplastic in aquatic ecosystem is very less investigated specially in freshwater. There have been evidences of MPs ingestion by freshwater biota but the fate of these MPs further in the food chain is unexplored. Thus, we reviewed the status of MPs in freshwater biota and tried to compare the studies to merge the available information, concepts, and perspectives in order to draw a conclusion on bioaccumulation potential, trophic transfer possibilities, biomagnification, and trends of ingesting MPs by the biota. In this review, the previously available information about MPs in aquatic biota is arranged, analyzed, and interpreted to understand all possible routes of MPs in freshwater habitats. The review further provides a better understanding about the lack of information and research gaps that are needed to be explored to develop a solution to the problem of MPs in near future.

A versatile approach to evaluate the occurrence of microfibers in mussels Mytilus galloprovincialis

Microplastics of fibrous shape are esteemed to be the most abundant micro-debris form present in the environment. Despite the occurrence of microfibers in fish may pose a risk to human health, the literature is scarce regarding studies on the contamination in commercial marine fish mostly due to methodological issues. In this study, a versatile approach, able to discriminate among natural and synthetic microfibers according to the evaluation of specific morphological features, is proposed in farmed mussels (Mytilus galloprovincialis). The approach was useful to determine that microfibers were present in 74% of mussel samples, with a mean number of 14.57 microfibers/individual, corresponding to 3.13 microfibers/g w.w. A negative correlation between the size of analysed mussels and the amount of microfibers/g w.w. was detected, showing that smaller specimens contained more microfibers than the larger ones. This work paves the way to further studies aimed to adequately assess the risk that microfibers may pose to marine biota, also considering the commercial value as seafood items of many species of the Mytilus genus and the potential implication for human exposure.

Seasonal change of microplastics uptake in the Pacific oysters Crassostrea gigas cultured in the Yellow Sea and Bohai Sea, China

This study investigated seasonal microplastics (MPs) pollution characteristics in oysters and surrounding surface seawater from five aquaculture farms located at the Yellow Sea and Bohai Sea. MPs abundances in oysters were 2.40 ± 0.14 (winter) to 3.28 ± 0.19 (autumn) items/individual, and 0.22 ± 0.02 (spring) to 0.45 ± 0.06 (summer) items/g (ww). In surface seawater, average seasonal MPs abundances were 3.41 ± 1.06-8.86 ± 2.48 items/L. Fibers were dominant shape, and cellophane and polyethylene terephthalate (PET) were dominant polymers in oysters and surface seawater. Positive correlation was found between oysters' MPs abundance (items/individual) and environmental factors (NO₂-N (r = 0.466), and temperature (r = 0.485)) by Spearman correlation analysis in four seasons. Main environmental factor affecting seasonal MPs abundance of oysters and surface seawater was NH₃-N and SiO₃-Si in summer and winter respectively. In conclusion, seasonal change of MPs uptake in cultured oysters was relatively small.

Microplastic prevalence in anatolian water frogs (Pelophylax spp.)

Frogs are on the verge of extinction due to various biotic and abiotic stressors. Rivers, lakes, ponds, wetlands, and ditches that make up their habitats are exposed to different anthropogenic pollutants. Today, plastics stand out among these pollutants due to their widespread use; however, the information on microplastic (MP) accumulation in frogs is insufficient. In the present study, adult frog samples were collected from 19 different stations in Türkiye, including marsh frogs (Pelophylax ridibundus) from 18 stations and levantine frogs (Pelophylax bedriagae) from 1 station. MP was found in 147 (82.4%) of the 176 frogs that were analyzed. MP abundance in frogs varied between 0.20 and 18.93 MP individual^-1. The characterization of MPs was determined predominantly as follows; PET (70.1%) in polymer type, fiber (92.2%) in shape, navy blue/blue (76.1%) in color, and >90% were smaller than 300 μm. No significant relationship with frog's weight (correlation coefficient = 0.01, P = 0.812) or length (correlation coefficient = 0.06, P = 0.473) and MP abundance was detected. The outcomes of this survey might be a baseline to assess the ecological risks posed by MPs and to guide future experimental research.

Biokinetics of fluorophore-conjugated polystyrene microplastics in marine mussels

Biokinetic information on microplastics in bivalves is required to reduce the human exposure, but little is known about the time-course and size effect on tissue absorption and clearance. The biokinetics of fluorophore-labeled polystyrene microbeads with diameters 10 µm (PL10) and 90 µm (PL90) in Mytilus galloprovincialis marine mussels was investigated in the present study. It was found that both PL10 and PL90 showed a biphasic tissue distribution pattern in digestive and non-digestive tissues, highlighting the significant tissue distribution starting from 48 h post-treatment. The differential size effect on tissue distribution was observed only in the gills, which suggests that PL10 accumulates more than PL90. The depuration kinetics show that particles of both sizes can be cleared in any tissue, but non-digestive tissue requires a longer duration for depuration than digestive tissue. The differential size effect on depuration was observed for both digestive and non-digestive tissues, suggesting that PL10 needed a longer duration for depuration than PL90. More than seven days were needed for depuration of microplastics in mussels, which is an exceptionally longer period compared to conventional depuration of bivalves. The most significant improvement of this study is providing the biokinetics of two different-sized microplastics in mussels and the differential time for purging microplastics from mussels.

Effects of Human Activity on Markers of Oxidative Stress in the Intestine of Holothuria tubulosa, with Special Reference to the Presence of Microplastics

Pollution in the seas and oceans is a global problem, which highlights emerging pollutants and plastics, specifically microplastics (MPs), which are tiny (1 μm to 5 mm) ubiquitous plastic particles present in marine environments that can be ingested by a wide range of organisms. Holothurians are benthic organisms that feed on sediment; therefore, they can be exposed to contaminants present in the particles they ingest. The objective was to evaluate the effects of human activity on Holothuria tubulosa through the study of biomarkers. Specimens were collected in three different areas throughout the island of Eivissa, Spain: (1) a highly urbanized area, with tourist uses and a marina; (2) an urbanized area close to the mouth of a torrent; (3) an area devoid of human activity and considered clean. The results showed a higher presence of microplastics (MPs) in the sediments from the highly urbanized area in relation to the other two areas studied. Similarly, a higher number of MPs were observed in the digestive tract of H. tubulosa from the most affected area, decreasing with the degree of anthropic influence. Both in the sediment and in the holothurians, fibers predominated with more than 75% of the items. In the three areas, mesoplastics were analyzed by means of FTIR, showing that the main polymer was polypropylene (27%) followed by low-density polyethylene (17%) and polystyrene (16%). Regarding the biomarkers of oxidative stress, the intestine of H. tubulosa from the most impacted areas showed higher catalase, superoxide dismutase (SOD), glutathione reductase (GRd), and glutathione S-transferase (GST) activities and reduced glutathione (GSH) levels compared to the control area. The intermediate area only presented significant differences in GRd and GST with respect to the clean area. The activities of acetylcholinesterase and the levels and malondialdehyde presented similar values in all areas. In conclusion, human activity evaluated with the presence of MPs induced an antioxidant response in H. tubulosa, although without evidence of oxidative damage or neurotoxicity. H. tubulosa, due to its benthic animal characteristics and easy handling, can be a useful species for monitoring purposes.

Quantification of differential tissue biomarker responses to microplastic ingestion and plasticizer bioaccumulation in aquaculture reared sea bream Sparus aurata

Marine aquaculture is considered a potential source of microplastics (MPs). MPs can induce oxidative stress and damage in marine species. In this study we evaluated the impact of MPs intake in the commercial fish, Sparus aurata, from aquaculture facilities and the antioxidant response associated to this MPs ingestion in caged specimens for 120 days. Sampling was carried out at the beginning of the study (T₀), at 60 days (T₆₀) and at 120 days (T₁₂₀). At each sampling stage, gastrointestinal tract, blood, plasma, liver and muscle samples were obtained to analyse MPs intake (gastrointestinal tract), oxidative stress markers (blood, plasma and liver) and plasticizers bioaccumulation (muscle). Fish sampled at T₆₀ presented the highest MPs intake and plasticizers accumulated in muscle over time, but with a different pattern according to type: bisphenols and phthalates. This indicates MPs ingestion induces a differential tissue response in S. aurata. Similarly, stress biomarkers presented a differential response throughout the study, depending on the analysed tissue. In the case of oxidative damage markers, for malondialdehyde (MDA) an increase throughout the study was observed both in liver and blood cells but with a progressive decrease in plasma. In the case of phase I detoxifying enzyme activities in liver, 7-ethoxyresorufin O-deethylase (EROD), 7-benzyloxy-4-[trifluoromethyl]-coumarin-O-debenzyloxylase (BFCOD) and carboxylesterases (CE), showed a comparable decrease at T₆₀ with a slight recovery at T₁₂₀. In contrast, glutathione-S-transferase (GST) activity was significantly enhanced at T₆₀ compared to the other sampling stages. In conclusion, MPs ingestion occurs in aquaculture reared seabream where potentially associated plasticizers accumulate in the muscle and both could be responsible for plasma and liver oxidative stress damage and alterations on detoxifying biomarkers responses.

Are We Underestimating Anthropogenic Microfiber Pollution? A Critical Review of Occurrence, Methods, and Reporting

Anthropogenic microfibers, a ubiquitous environmental contaminant, can be categorized as synthetic, semisynthetic, or natural according to material of origin and production process. Although natural fibers, such as cotton and wool, originated from natural sources, they often contain chemical additives, including colorants (e.g., dyes, pigments) and finishes (e.g., flame retardants, antimicrobial agents, ultraviolet light stabilizers). These additives are applied to textiles during production to give textiles desired properties like enhanced durability. Anthropogenically modified "natural" and semisynthetic fibers are sufficiently persistent to undergo long-range transport and accumulate in the environment, where they are ingested by biota. Although most research and communication on microfibers have focused on the sources, pathways, and effects of synthetic fibers in the environment, natural and semisynthetic fibers warrant further investigation because of their abundance. Because of the challenges in enumerating and identifying natural and semisynthetic fibers in environmental samples and the focus on microplastic or synthetic fibers, reports of anthropogenic microfibers in the environment may be underestimated. In this critical review, we 1) report that natural and semisynthetic microfibers are abundant, 2) highlight that some environmental compartments are relatively understudied in the microfiber literature, and 3) report which methods are suitable to enumerate and characterize the full suite of anthropogenic microfibers. We then use these findings to 4) recommend best practices to assess the abundance of anthropogenic microfibers in the environment, including natural and semisynthetic fibers. By focusing exclusively on synthetic fibers in the environment, we are neglecting a major component of anthropogenic microfiber pollution. Environ Toxicol Chem 2022;41:822-837. © 2021 SETAC.

Microplastics: A review of analytical methods, occurrence and characteristics in food, and potential toxicities to biota

Microplastics (MPs) are ubiquitous in various environment compartments, including food. Here, we collected research reports of MPs in food published during 2010-2020, and summarized the analytical methods developed and utilized by researchers (e.g., digestion, separation and identification, as well as related QA/QC measures implemented), the occurrence, and the characteristics of MPs in six kinds of food. The potential effects on biota from exposure to MPs were also reviewed. The results showed that most researchers digested food samples using chemical solutions such as HNO₃, H₂O₂, KOH, or NaOH. FT-IR and Raman spectroscopy were the main technique for identifying MPs, and microscopes were used to count MP particles. The abundances MPs were in the ranges of 0-5860, 2.00-1100, 0-698, 4.00-18.7, 0-5.68 × 10⁴ and 900-3000 particles/kg in beverages, condiments, honey, meat, seafood and vegetables, respectively. The "maximum" annual human intake of MPs from these foods is approximately 1.42 × 10⁵-1.54 × 10⁵ particles/capita, equivalent to the consumption of 50 plastic bags (size: 0.04 mm × 250 mm × 400 mm, density: 0.98 g/cm³) each year. Blue-colored and fiber-shaped MP particles were the most commonly observed in food, predominated by PA, PE, PES, PET and PP types. Toxicity studies indicated that MPs, additives of MPs and adsorbents or microorganisms on the surfaces of MPs were all somewhat toxic to cells or biota. Exposure to MPs may induce oxidative stress, inflammation, neurotoxicity, and reproductive toxicity, and change the structure of intestinal microflora in cells or biota. Therefore, we call for more investigation into the residual, excretion and bioavailability of MPs or related absorbents/additives in biota and humans.

Molecular biomarker responses in the freshwater mussel Anodonta anatina exposed to an industrial wastewater effluent

Using a selection of molecular biomarkers, we evaluated responses in freshwater mussels (Anodonta anatina) exposed to effluent from an industrial wastewater treatment facility. The aims of this work were to (1) assess biomarkers of general toxicity under sublethal exposure to an anthropogenic mixture of chemicals, represented by an arbitrary effluent, and (2) evaluate the potential of A. anatina as a bioindicator of pollution. Adult mussels (n = in total 32; 24 males and 8 females) were exposed (96 h) in the laboratory to a fixed dilution of effluent or to a control treatment of standardized freshwater. Metal concentrations were in general higher in the effluent, by an order of magnitude or more, compared to the control. Toxic unit estimates were used as proxies of chemical stress, and Cu, Ni, and Zn were identified as potential major contributors (Cu> Ni > Zn). Six transcriptional (cat, gst, hsp70, hsp90, mt, sod) and two biochemical (AChE, GST) biomarkers were analyzed in two tissues, gills, and digestive glands. Out of the 16 responses (eight biomarkers × two tissues), 14 effect sizes were small (within ± 28 % of control) and differences non-significant (p > 0.05). Results did however show that (1) AChE activity increased by 40% in gills of exposed mussels compared to control, (2) hsp90 expression was 100% higher in exposed female gills compared to control, and (3) three marker signals (AChE in both tissues, and hsp70 in gills) differed between sexes, independent of treatment. Results highlight a need for further investigation of molecular biomarker variability and robustness in A. anatina.

Anthropogenic fibres in white clams, Meretrix lyrata, cultivated downstream a developing megacity, Ho Chi Minh City, Viet Nam

Anthropogenic fibres are an emerging pollutant worldwide. The Can Gio mangrove area is located downstream of the Saigon River, and is characterised by high level of anthropogenic fibres originating from domestic and industrial textile and apparel manufacturing. In this area, biota is thus subjected to a high potential risk of anthropogenic fibre contamination. This study aims to characterise the accumulation of anthropogenic fibres in different tissues, i.e. gills, digestive systems, and remaining tissues, of white clams (Meretrix lyrata) cultivated in the Can Gio beach sand, during a seven-month sampling period. The results showed an average concentration of 3.6 ± 2.1 fibres individual^-1 or 2.7 ± 2.4 fibres g^-1 ww. Higher fibre accumulation was observed in remaining tissues than in gills and digestive systems, and no temporal variation was observed in all clam tissues. The intake of fibres by humans consuming clams was estimated to be 324 fibres inhabitant^-1 yr^-1.

Concentration of microplastics in bivalves of the environment: a systematic review

The aim of this review was to identify the current knowledge regarding the concentration of microplastics in bivalves in the marine, estuarine, and freshwater environments. For this purpose, researches were conducted from September 2020 to February 2021 in the Scopus, Web of Science, and Google scholar databases, following a meticulous selection of articles. To comprehensively understand the selected articles, an extensive review was carried out in order to identify the methodologies employed, sampling sites, species evaluated, characteristics of the microplastics (concentrations, shapes, sizes, and polymers) and their relationship with the concentration of this particles in the environment. A total of 93 articles were selected, with an exponential growth in the number of articles from April 2014 to February 2021. Worldwide, 80 articles were realized in the Northern Hemisphere and thirteen in the Southern Hemisphere. The samplings of organisms were carried out in 36 countries, besides one in Antarctica. The concentration of microplastics were studied in 70 species, with mussels Mytilus spp. and the oysters Crassostrea spp. being the main genus studied. Due to the different methodologies used to digest the tissues of organisms and identify microplastics and species, it is difficult to make comparisons between the results of different studies. In addition, data on the concentrations of microplastics in the environment, as well as their composition and characteristics, are needed, enabling the verification of relationships with the concentrations identified in organisms, which does not occur in most studies. Thus, we suggest an increase in the number of studies to be realized in the southern hemisphere, future studies use the same methodology of digestion, the polymer identification of microplastics and samplings of the surrounding environment, enabling a greater comparison between studies.

Microplastic intake and enzymatic responses in Mytilus galloprovincialis reared at the vicinities of an aquaculture station

Aquaculture is a potential source of microplastics (MPs) that could be strong stressors for marine organisms. In this study, we evaluated the effects of MPs derived from aquaculture in antioxidant defences and oxidative stress markers in gills of Mytilus galloprovincialis. Mussels were distributed in three areas with different impacts: inside aquaculture cages, Control 1 (located inside Andratx harbour) and Control 2 (located in a no-anthropized area). Samples were obtained along three different time periods in May (T₀), July (T₆₀) and in September (T₁₂₀). At each sampling period, mussels' biometric measurements were taken, and tissue samples were kept frozen for biochemical determinations and to determine the intake of MPs. An increase in MPs intake was detected throughout the study, and this increase was significantly higher in samples from the aquaculture cages. Similarly, antioxidant enzyme activities (catalase, superoxide dismutase, glutathione reductase and glutathione peroxidase) were significantly higher in samples from cages at T₁₂₀. Additionally, a similar tendency was observed in glutathione-s-transferase, with a higher activity in the aquaculture cages at T₆₀ and T₁₂₀. Malondialdehyde and carbonyl protein derivates as a marker of oxidative damage were also measured and samples from aquaculture cages presented higher oxidative stress markers, mainly in T₁₂₀. In conclusion, living in environments exposed to aquaculture activities at sea may imply a higher intake of MPs which in turn might cause an antioxidant response in M. galloprovincialis which is not enough to avoid oxidative damage.

Microplastics Contamination in Commercial Green Mussels from Selected Wet Markets in Thailand

Mussels have been identified as sentinel organisms (around the world) that indicate microplastic (MP) pollution. Since they are filter feeders, they easily uptake MPs. Mussels sold in commercial markets have been identified as an ideal way to directly quantify human exposure to MPs through seafood consumption. There are no studies reported on MP contamination of market-sold species in Thailand. This study investigates the level of MP contamination in market-sold green mussels, which is a popular seafood in Thailand. A total of 90 green mussels (Perna viridis) collected from three markets were analyzed for the number, polymer types, and morphology of the MPs. Fourier-Transform Infrared Micro-Spectroscopy (micro-FTIR) analysis was used for polymer identification. Nile Red (NR) tagging was used for the enumeration of MPs. MPs were widely discovered in green mussels from all three markets with 100% detection frequency. The average abundance of MPs in green mussels was quantified as 7.32 ± 8.33 items/mussel and 1.53 ± 2.04 items/g (wet weight). Ethylene/propylene copolymer followed by low-density polyethylene (PE-LD), polypropylene (PP), and polyethylene terephthalate (PET) were found. Fragments (75.4%) were the most common morphotype, followed by fibers (24.6%). Results indicate that the consumption of green mussels as a food can be one of the exposure pathways for the Thai population. Moreover, smaller size MPs were predominant, which are reported to cause higher impacts.

Where are we? Towards an understanding of the selective accumulation of microplastics in mussels

Mussels are suggested as bioindicators of marine microplastic pollution. However, they are selective in regards to accumulation of microplastics. To make studies more targeted and comparable, ultimately helping to determine the suitability of the mussel as a bioindicator species for microplastic exposure, we review the published literature that has directly or indirectly demonstrated particle selection in mussels. The reported difference between microplastic levels in mussel tissues and environmental matrices provides evidence for their selective uptake characteristics. Both the organ-specific fate characteristics of microplastics, and the different movement patterns of microplastics in the same organ, show that selective translocation processes take place. The selective elimination is reflected in multiple aspects which include (1) the different characteristics of microplastics in excretion and mussel body; (2) the different retention time of various microplastics in mussels; and (3) the tissue-specific change in the numbers of microplastics during the depuration process. This selectivity is affected by the characteristics of the microplastics, the environmental, or laboratory exposure concentrations, feeding status, and other factors. There are still many research gaps and contradictory viewpoints in this field due to this complexity. The current methodology needs improvement and a breakthrough in standardization.

Microplastics and Nanoplastics: Emerging Contaminants in Food

As current concerns about food safety issues around the world are still relatively serious, more and more food safety issues have become the focus of people's attention. What's more serious is that environmental pollution and changes in human lifestyles have also led to the emergence of contaminants in food, microplastics (MPs) and nanoplastics (NPs) being typical representatives. MPs and NPs (M/NPs) in food are gradually becoming recognized by regulatory authorities and the public. Most published reviews on M/NPs have been focused on the environmental ecosystems. In those papers, it is only sporadically mentioned that M/NPs can also appear in food. As far as we know, there has not been a systematic review of the pollution and existing status of M/NPs in food. This Review focuses on the harmfulness of M/NPs, the ways in which M/NPs contaminate food, the residual amount of M/NPs in food, and the current analysis and detection methods for M/NPs in food. Current analysis and detection methods have problems such as being time-consuming, involving cumbersome operation, and giving poor accuracy. In the future, it will be necessary to increase the research on methods for efficient and sensitive separation and detection of M/NPs in food. Finally, it is hoped that this Review will arouse more people's awareness of and attention to the seriousness of M/NPs in food.

Oxidative stress induced by nanoplastics in the liver of juvenile large yellow croaker Larimichthys crocea

There are many toxicological studies on microplastics, but little is known about the effect of nanoplastics (NPs). Here, we evaluated the oxidative stress responses induced by NPs (10, 10⁴ and 10⁶ particles/l) in juvenile Larimichthys crocea during 14-d NPs exposure followed by a 7-d recovery. After exposure, the activities of antioxidant enzymes (SOD, CAT, GPx) and MDA levels increased in the liver of fish at the highest NPs concentration. SOD and CAT activities remained elevated above the baseline after recovery under high-concentration NPs but returned to the baseline in two other NP treatments. Although lipid peroxidation in liver was reversible, juvenile fish in NPs treatments exhibited a lower survival rate than the control during both exposure and recovery. Furthermore, IBR value and PCA analysis showed the potential adverse effects of NPs. Considering that NPs can reduce the survival of fish juveniles, impacts of NPs on fishery productivity should be considered.

Freshwater wild biota exposure to microplastics: A global perspective

Current understanding on the exposure of freshwater organisms to microplastics (plastics sized between 1 µm and 5 mm) has arisen mostly from laboratory experiments-often conducted under artificial circumstances and with unrealistic concentrations. In order to improve scientific links through real ecosystem exposure, we review field data on the exposure of free-living organisms to microplastics.We highlight that the main outputs provided by field research are an assessment of the occurrence and, at times, the quantification of microplastics in different animal taxa. Topics of investigation also include the causes of contamination and the development of biological monitoring tools. With regard to taxa, fish, mollusks, and arthropods are at the center of the research, but birds and amphibians are also investigated. The ingestion or occurrence of microplastics in organs and tissues, such as livers and muscles, are the main data obtained. Microorganisms are studied differently than other taxa, highlighting interesting aspects on the freshwater plastisphere, for example, related to the structure and functionality of communities. Many taxa, that is, mammals, reptiles, and plants, are still under-examined with regard to exposure to microplastics; this is surprising as they are generally endangered.As biota contamination is acknowledged, we contribute to an interdisciplinary scientific discussion aimed at a better assessment of knowledge gaps on methodology, impact assessment, and monitoring.

A One Health perspective of the impacts of microplastics on animal, human and environmental health

Microplastics contamination is widespread in the environment leading to the exposure of both humans and other biota. While most studies overemphasize direct toxicity of microplastics, particle concentrations, characteristics and exposure conditions being used in these assays needs to be taken into consideration. For instance, toxicity assays that use concentrations over 100,000 times higher than those expected in the environment have limited practical relevance. Thus, adverse effects on animal and human health of current environmental concentrations are identified as a knowledge gap. Conversely, this does not suggest the lack of any significant effects of microplastics on a global scale. The One Health approach provides a novel perspective focused on the intersection of different areas, namely animal, human, and environmental health. This review provides a One Health transdisciplinary approach to microplastics, addressing indirect effects beyond simple toxicological effects. Microplastics can, theoretically, change the abiotic properties of matrices (e.g., soil permeability) and interfere with essential ecosystem functions affecting ecosystem services (e.g., biogeochemical processes) that can in turn impact human health. The gathered information suggests that more research is needed to clarify direct and indirect effects of microplastics on One Health under environmentally relevant conditions, presenting detailed knowledge gaps.

Long-term exposure to virgin and seawater exposed microplastic enriched-diet causes liver oxidative stress and inflammation in gilthead seabream Sparus aurata, Linnaeus 1758

Plastics accumulation in marine ecosystems has notable ecological implications due to their long persistence, potential ecotoxicity, and ability to adsorb other pollutants or act as vectors of pathogens. The present work aimed to evaluate the physiological response of the gilthead seabream (Sparus aurata) fed for 90 days with a diet enriched with virgin and seawater exposed low-density polyethylene microplastics (LDPE-MPs) (size between 100 and 500 μM), followed by 30 days of depuration, applying oxidative stress and inflammatory markers in liver homogenates. No effects of LDPE-MPs treatments on fish growth were observed throughout this study. A progressive increase in antioxidant enzyme activities was observed throughout the study in both treatments, although this increase was higher in the group treated with seawater exposed MPs. This increase was significantly higher in catalase (CAT), glutathione reductase (GRd), and glutathione-s-transferase (GST) in the seawater exposed MPs group, with respect to the virgin group. In contrast, no significant differences were recorded in superoxide dismutase (SOD) and glutathione peroxidase (GPx) between both groups. Exposure to MPs also caused an increase in the oxidative damage markers (malondialdehyde and carbonyls groups). Myeloperoxidase activity significantly increased because of MPs treatments. After 30 days of depuration, antioxidant, inflammatory enzyme activities and oxidative damage markers returned to values similar to those observed in the control group. In conclusion, MPs exposure induced an increase of antioxidant defences in the liver of S. aurata. However, these elevated antioxidant capabilities were not enough to prevent oxidative damage in the liver since, an increased oxidative damage marker was associated with MPs ingestion. The treatment with seawater exposed MPs caused a more significant antioxidant response (CAT, GRs, and GST). Although after a depuration period of 30 days a tendency to recover the initial values of the biomarkers was observed this does not seem to be time enough for a complete normalization.

Effect of microplastics in water and aquatic systems

Surging dismissal of plastics into water resources results in the splintered debris generating microscopic particles called microplastics. The reduced size of microplastic makes it easier for intake by aquatic organisms resulting in amassing of noxious wastes, thereby disturbing their physiological functions. Microplastics are abundantly available and exhibit high propensity for interrelating with the ecosystem thereby disrupting the biogenic flora and fauna. About 71% of the earth surface is occupied by oceans, which holds 97% of the earth's water. The remaining 3% is present as water in ponds, streams, glaciers, ice caps, and as water vapor in the atmosphere. Microplastics can accumulate harmful pollutants from the surroundings thereby acting as transport vectors; and simultaneously can leach out chemicals (additives). Plastics in marine undergo splintering and shriveling to form micro/nanoparticles owing to the mechanical and photochemical processes accelerated by waves and sunlight, respectively. Microplastics differ in color and density, considering the type of polymers, and are generally classified according to their origins, i.e., primary and secondary. About 54.5% of microplastics floating in the ocean are polyethylene, and 16.5% are polypropylene, and the rest includes polyvinyl chloride, polystyrene, polyester, and polyamides. Polyethylene and polypropylene due to its lower density in comparison with marine water floats and affect the oceanic surfaces while materials having higher density sink affecting seafloor. The effects of plastic debris in the water and aquatic systems from various literature and on how COVID-19 has become a reason for microplastic pollution are reviewed in this paper.

A new strategy for using lint-microfibers generated from clothes dryer as a sustainable source of renewable energy

Lint-microfibers (LMs) generated during clothes drying are classified as primary microplastics and consist mainly of cotton, polyester and lignin. This research aims to convert LMFs into energy products using a pyrolysis treatment. The pyrolysis experiments were performed using a pilot pyrolysis plant. SEM-EDS was used to observe the morphology and elemental composition of the feedstock and the obtained biochar, while a digital unit of Instantaneous Gas analyzer and Gas chromatography (GC) were used to observe the concentration of O₂, N₂, CO₂, CO, H₂, CH₄ gases during the whole conversion process. Finally, a simple mathematical model was developed to evaluate the economic and environmental performance of the suggested strategy based on the LMFs generated by one million persons. Based on the results of the developed model and yield of pyrolysis process, around 45 tons of LMFs are generated by one million persons annually and this amount is enough to produce 13.8 tons of oil (~31%), 21.5 tons of gas (47.7%), and 9.7 ton of char (21.6%) with estimated profitability of 120,400$ and reduction in carbon footprint estimated at -42,039,000kg CO2-eq/t of LMFs.

Sampling, pre-treatment, and identification methods of microplastics in sewage sludge and their effects in agricultural soils: a review

Microplastics are widely detected in wastewater treatment plants. They can remove microplastics from wastewaters with a high yield, but it means that microplastics are transferred and accumulated to sewage sludge. Lately, increasing attention has been paid to microplastics in raw and treated wastewaters. However, studies about quantification and identification of microplastics in sewage sludge are very scarce and need to be further investigated. Since the sludge-based microplastics are newly studied and are a challenging matrix due to high organic content, there is limited knowledge of sampling, pre-treatment methods, identification techniques, and expression units. Besides, treated sewage sludge is mostly used for soil amendment to improve soil fertility and it gives economic advantages. This situation creates a pathway for microplastics entering the soil environment with unknown consequences. To the best of our knowledge, microplastics have a large specific surface area, small size, and hydrophobicity which makes it a good adsorbent for other pollutants. Therefore, the combined effect of microplastics with adsorbed pollutants such as heavy metals, antibiotics, and persistent organic pollutants could give serious harm to soil safety and soil organisms. Herein, new developments in the methods for sampling, pre-treatment, and identification techniques of microplastics in sewage sludge were reviewed. Then, the abundance of microplastics, major polymer types, and shapes in sewage sludge were examined. Finally, the effects and ecological risks of microplastic pollution as a result of agricultural usage of sewage sludge in the soil environment have been summarized. Also, the main points for future research were highlighted.

Seasonal variation and risk assessment of microplastics in surface water of the Manas River Basin, China

The ubiquity of microplastics in the environment has caused great influence to ecosystems and seriously threatened human health. To better understand the variation in microplastics in different seasons in an inland freshwater environment and determine the sources of microplastic pollution and its migration features, this study investigated the characteristics of microplastic pollution during dry (April) and wet (July) seasons in surface water of the Manas River Basin, China. The size, color, shape, area distribution and compound composition of microplastics were studied. Moreover, the risk of microplastic contamination was explored based on risk assessment models. The results demonstrated that the degree of pollution caused by microplastic abundance was minor in this study area. The average abundance of microplastics in April (17 ± 4 items/L) was higher than that in July (14 ± 2 items/L). The range in the abundance of microplastics in April and July were 22 ± 5-14 ± 3 items/L and 19 ± 2-10 ± 1 items/L, respectively. Highly hazardous polymers such as Polyvinyl chloride (PVC) and Polycarbonate (PC) have a significant impact on the results of the evaluation of the presence of microplastics. This study is an important reference for understanding the characteristics of the seasonal variation in microplastics in inland freshwater environments and has practical significance, as it will allow relevant agencies to accurately assess the pollution level of microplastics in different seasons. It is of practical significance to understand the sources and sinks of microplastics in inland freshwater environment.

Preliminary indoor evidences of microplastic effects on freshwater benthic macroinvertebrates

Plastics are to date considered one of the main detrimental drivers for the health of aquatic ecosystems, both in marine and inland waters. Regarding the latter habitat, it seems surprising how the plastic effects on benthic invertebrates are neglected since macroinvertebrates have a long tradition in the water quality assessment activities. In this context, we propose timely indoor observations on the exposure of caddisfly Odontocerum albicorne and mayfly Ephemera danica to various microplastic polymers (ABS, PET, PP, PS, PVDF). Three different experimental designs were performed on caddisflies and mayflies by exposing their larvae to natural and microplastic substrates. Our findings highlighted how microplastics affected both caddisflies in rebuilding its own case (after having removed the natural one) and mayflies burrowing. Particularly, all caddisflies rebuilt cases using the microplastic polymers provided instead of natural items only. Moreover, we provide the first evidence that mayflies burrow mainly in microplastic substrates rather than in natural ones. Our research highlights that macroinvertebrate larvae would use naturally occurring microplastics and this could be of particular concern in freshwaters with high contamination by plastics. Indeed, larvae appear to not necessarily perceive microplastics as a direct stressor. Further studies ought to be conducted to understand the chronic perturbation on larvae fitness and for example, on drift behaviour. Also, further investigations are needed to understand the potentialities of using plastics by benthic macroinvertebrates.

Microplastic pollution profile of Mediterranean mussels (Mytilus galloprovincialis) collected along the Turkish coasts

Plastics profoundly threatens ecological balance in marine ecosystems across the globe in the current era of industrialization. Microplastics (MP), in particular, can pose risks reaching humans through the food web via various marine organisms. Among these organisms, since they are consumed as a whole, mussels are vital vectors of MP transfer during human consumption. Hence, here we analyzed MP pollution in Mediterranean mussel (Mytilus galloprovincialis) sampled from 23 different locations all along the Turkish coasts of the Black Sea, Sea of Marmara, and the Aegean Sea. After digestion of the mussels with H₂O₂, the micro-particles were determined under a stereomicroscope and characterized by confirming with FTIR analyses. 48% of the sampled mussels were found to have MPs. The average MP abundance was 0.69 item/mussel and 0.23 item/g fresh weight (fw) of soft tissue. Morphology was ordered as follows: fragments (67.6%)> fibers (28.4%)> films (4.05%). The dominant size of MPs was detected less than 0.5 mm (26.58%). 12 different polymers have been identified by FTIR and PET (32.9%), PP (28.4%), and PE (19.4%) were found to constitute 80% of the total MPs. The annual average exposure amount for mussel consumers in Turkey was estimated as 1918 MPs item/per year. Even though international organizations such as FAO, JECFA, or EU have not declared permissible limits, our data may inform human health uptake of MP ingestion via mussels. This data might also serve as a reference data-set for further MP monitoring research in Turkish and European Seas.

Detection of Metal-Doped Fluorescent PVC Microplastics in Freshwater Mussels

The large-scale production of plastic and the resulting release of waste is leading to a huge accumulation of micro-sized particles in the environment that could have an impact on not only aquatic organisms but also on humans. Despite the extensive literature on the subject, there is still an insufficient harmonization of methodologies for the collection and analysis of microplastics (MPs) in complex matrices; especially for high density polymers; such as polyvinyl chloride (PVC), which tend to sink and accumulate in sediments, becoming available to benthonic organisms. In this article, mussels have been chosen as model for microplastic accumulation due to their extensive filtering activity and their wide distribution in both fresh and salt water basins. To facilitate the identification and quantification of microplastics taken up by mussels, novel fluorescent and metal-doped PVC microplastics (PVC-Platinum octaethylporphyrin (PtOEP) MPs in the size range of 100 µm) have been synthesized and characterized. For the analysis of the mussels following exposure, an enzymatic protocol using amylase, lipase, papain, and SDS for organic material digestion and a sucrose-ZnCl₂ density gradient for the selective separation of ingested microplastics has been developed. The final identification of MPs was performed by fluorescence microscopy. This work can greatly benefit the scientific community by providing a means to study the behavior of PVC MPs, which represent an example of a very relevant yet poorly studied high density polymeric contaminant commonly found in complex environmental matrices.

Microplastic Contamination in Freshwater Environments: A Review, Focusing on Interactions with Sediments and Benthic Organisms

Plastic is one of the most commonly produced and used materials in the world due to its outstanding features. However, the worldwide use of plastics and poor waste management have led to negative impacts on ecosystems. Plastic degradation in the environment leads to the generation of plastic particles with a size of <5 mm, which are defined as microplastics (MPs). These represent a global concern due to their wide dispersion in water environments and unclear potential ecotoxicological effects. Different studies have been performed with the aim of evaluating the presence and impacts of MPs in the marine environment. However, the presence of MPs in freshwater systems is still poorly investigated, making data retrieval a difficult task. The purpose of this review is to identify the main aspects concerning MPs pollution sources in lakes and rivers, with a focus on freshwater sediments as a site of accumulation and as the habitat of benthic organisms, which are key components of food webs and play a fundamental role in energy/contaminant transfer processes, but are still poorly considered. Through this review, the sources and fate of MPs in freshwater are analysed, ecotoxicological studies focused on sediments and benthic fauna are exposed, the most frequently used sampling and analysis strategies are reported, and future trends of MPs analysis in this field are proposed.