Abundance and distribution of small microplastics (≤ 3 μm) in sediments and seaworms from the Southern Mediterranean coasts and characterisation of their potential harmful effects

Environmental microplastics compromise reproduction of the marine invertebrate Mytilus galloprovincialis: A holistic approach

The extensive presence of microplastics (MPs) in marine ecosystems constitutes a major threat to aquatic environments. The gametes of the marine invertebrate Mytilus galloprovincialis, which is essential for coastal ecosystems, are released directly into the water, potentially exposing them to environmental microplastics (EMPs). This study examined the effects of exposing M. galloprovincialis gametes to 50 or 100 µg/L EMP for 1 h on fertilization rates, larval quality, and the molecular mechanisms underlying the induction of apoptosis and shell growth. Our findings show that increased EMP concentrations correlate with reduced fertilization success and higher rates of larval malformations, indicating negative impacts on embryonic development. Additionally, DNA degradation in larvae is related to the EMP concentration. The apoptosis-associated proteins Bax, P53, and Cas-3 are upregulated, whereas Bcl-2 and DNA-ligase are downregulated with increasing EMP concentrations. Prothymosin-ɑ (PTMA), which is crucial for cell proliferation, also decreases with increasing EMP concentrations, contributing to impaired cell proliferation and growth imbalances. Reduced HRG gene expression is correlated with decreased shell growth and larval malformations. This study underscores the detrimental impact of EMPs on bivalve gametes, which impacts fertilization success and larval quality and highlights the potential risks to species survival and marine ecosystem stability.

Detection and quantification of microplastics in Posidonia oceanica banquettes in the Gulf of Gabes, Tunisia

Plastic pollution and microplastic (MP) debris are some of the most significant solid waste pollutants, threatening the marine environment and causing sediment accumulation. Coastal seagrass areas are usually important habitats that support multiple living species and provide several ecosystem services. This study aimed to determine the abundance, characteristics, and composition of microplastics on the southern side of the Tunisian Mediterranean Sea by using Posidonia oceanica (P. oceanica) as a crucial trap for microplastics. Samples of Posidonia leaves were collected from the Tunisian coastal area of Gabes-City. The characterization of microplastic detritus was carried out by stereomicroscopy, and acid digestion of Posidonia tissue leaves was performed for qualitative and quantitative analysis of MPs using NMR spectroscopy. The study revealed pellets, threads, and fragments of polymers as the frequent forms found in MPs. Polyethylene, polystyrene, and bis(2-ethyl-hexyl) phthalates were the most abundant materials detected. P. oceanica leaves contributed notably to microplastic subsidence, seafloor horizontal migration, and sediment burial. Thus, marine flora appeared to be a good tool to detect and monitor plasticizers, and further studies of the P. oceanica seagrass areas will help in developing a more comprehensive knowledge of chemicals spreading over a geographical zone. The results obtained will be used for developing baseline data on plasticizer contamination on the wide-ranging marine coast.

Metabolomic and biochemical disorders reveal the toxicity of environmental microplastics and benzo[a]pyrene in the marine polychaete Hediste diversicolor

Recently, the abundance of environmental microplastics (MPs) has become a global paramount concern. Besides the danger of MPs for biota due to their tiny size, these minute particles may act as vectors of other pollutants. This study focused on evaluating the toxicity of environmentally relevant concentrations of MPs (10 and 50 mg/kg sediment) and benzo[a]pyrene (B[a]P, 1 µg/kg sediment), alone and in mixture, for 3 and 7 days in marine polychaete Hediste diversicolor, selected as a benthic bioindicator model. The exposure period was sufficient to confirm the bioaccumulation of both contaminants in seaworms, as well as the potential capacity of plastic particles to adsorb and vehiculate the B[a]P. Interestingly, increase of acidic mucus production was observed in seaworm tissues, indicative of a defense response. The activation of oxidative system pathways was demonstrated as a strategy to prevent lipid peroxidation. Furthermore, the comprehensive Nuclear Magnetic Resonance (NMR)-based metabolomics revealed significant disorders in amino acids metabolism, osmoregulatory process, energetic components, and oxidative stress related elements. Overall, these findings proved the possible synergic harmful effect of MPs and B[a]P even in small concentrations, which increases the concern about their long-term presence in marine ecosystems, and consequently their transfer and repercussions on marine fauna.

Toxicity assessment of animal manure composts containing environmental microplastics by using earthworms Eisenia andrei

Nowadays, animal manure composting constitutes a sustainable alternative for farmers to enhance the level of nutrients within soils and achieve a good productivity. However, pollutants may be present in manures. This study focuses on the detection of environmental microplastics (EMPs) into composts, as well as on the assessment of their potential toxicity on the earthworm Eisenia andrei. To these aims, animals were exposed to two types of compost, namely bovine (cow) and ovine (sheep) manure, besides to their mixture, for 7 and 14 days. The presence and characterization of EMPs was evaluated in all the tested composts, as well as in tissues of the exposed earthworms. The impact of the tested composts was assessed by a multi-biomarker approach including cytotoxic (lysosomal membrane stability, LMS), genotoxic (micronuclei frequency, MNi), biochemical (activity of catalase, CAT, and glutathione-S-transferase, GST; content of malondialdehyde, MDA), and neurotoxic (activity of acetylcholinesterase, AChE) responses in earthworms. Results indicated the presence of high levels of EMPs in all the tested composts, especially in the sheep manure (2273.14 ± 200.89 items/kg) in comparison to the cow manure (1628.82 ± 175.23 items/kg), with the size <1.22 μm as the most abundant EMPs. A time-dependent decrease in LMS and AChE was noted in exposed earthworms, as well as a concomitant increase in DNA damages (MNi) after 7 and 14 days of exposure. Also, a severe oxidative stress was recorded in animals treated with the different types of compost through an increase in CAT and GST activities, and LPO levels, especially after 14 days of exposure. Therefore, it is necessary to carefully consider these findings for agricultural good practices in terms of plastic mitigation in compost usage, in order to prevent any risk for environment health.

Unraveling the interplay between environmental microplastics and salinity stress on Mytilus galloprovincialis larval development: A holistic exploration

The rise of plastic production has triggered a surge in plastic waste, overwhelming marine ecosystems with microplastics. The effects of climate change, notably changing salinity, have shaped the dynamics of coastal lagoons. Thus, understanding the combined impact of these phenomena on marine organisms becomes increasingly crucial. To address these knowledge gaps, we investigated for the first time the interactive effects of environmental microplastics (EMPs) and increased salinity on the early development of Mytilus galloprovincialis larvae. Morphological assessments using the larval embryotoxicity test revealed larval anomalies and developmental arrests induced by EMPs and increased salinity. Transcriptomic analyses targeting 12 genes involved in oxidative stress, apoptosis, DNA repair, shell formation, and stress proteins were conducted on D-larvae uncovered the potential effects of EMPs on shell biomineralization, highlighting the role of Histidine Rich Glycoproteine (HRG) and tubulin as crucial adaptive mechanisms in Mytilus sp. in response to environmental shifts. Furthermore, we explored oxidative stress and neurotoxicity using biochemical assays. Our findings revealed a potential interaction between EMPs and increased salinity, impacting multiple physiological processes in mussel larvae. Our data contribute to understanding the cumulative effects of emerging anthropogenic pollutants and environmental stressors, emphasizing the need for a holistic approach to assessing their impact on marine ecosystems.

Selection, identification and evaluation of optimal reference genes in Chinese sturgeon (Acipenser sinensis) under polypropylene microplastics stress

Polypropylene microplastics (PP-MPs) are emerging environmental contaminants that have the potential to cause adverse effects on aquatic organisms. Reverse transcriptase quantitative real-time polymerase chain reaction (RT-qPCR) is a valuable tool for assessing the gene expression profiles under PP-MPs stress. To obtain an accurate gene expression profile of tissue inflammation and apoptosis that reflects the molecular mechanisms underlying the impact of PP-MPs on Chinese sturgeon, identifying reliable reference genes is crucial for RT-qPCR analysis. In this study, we constructed an experiment model of Chinese sturgeon exposed to PP-MPs, assessed the pathological injury, metabolic profile responses and oxidative stress in liver, evaluated the reliability of 8 reliable reference genes by 4 commonly used algorithms including GeNorm, NormFinder, BeatKeeper, Delta Ct, and then analyzed the performance of inflammatory response genes in liver, spleen and kidney with the best reference gene. HE staining revealed that the cytoplasm full small vacuoles and nucleus diameter increased were occurred in the liver cell of PP-MPs in treatment groups. Additionally, oxidative and biochemical parameters were significantly changes in the liver of treatment groups. For the reference genes in PP-MPs exposure experiments, this study screening the optimal reference genes including: EF1α and GAPDH for liver and spleen, and GAPDH and RPS18 for kidney. Besides, 2 inflammatory response genes (NLRP3, TNF-α) were chosen to assess the optimal reference genes using the least stable reference gene (TUB) as a control, verified the practicality of the select reference genes in different tissues. We also found that the low concentration of PP-MPs could induce the liver tissue damage and inflammatory response in Chinese sturgeon. Our study initially evaluated the impact of short-time exposure with PP-MPs in Chinese sturgeon and provided 3 sets of validated optimal reference genes in Chinese sturgeon exposure to PP-MPs.

Diverse and high pollution of microplastics in seasonal snow across Northeastern China

Snow scavenging is recognized as one of the major sinks for atmospheric microplastics (MPs). However, little is known about the properties of MPs in large-scale surface snow. Using Nile Red staining and micro-Fourier transform infrared spectroscopy, we identified the shapes, sizes, and polymer components of MPs in seasonal snow across northeastern (NE) China, a major industrial area. The average concentration of MPs was (4.52 ± 3.05) × 104 MPs L-1, and the highest contamination (6.65 ± 3.89) × 104 MPs L-1 was observed in Changbai Mountains, which was the highest concentration observed in surface snow to the extent of literature. The majority of snow MPs were smaller than 50 μm and composed primarily of fragments. Ethylene vinyl acetate and polyethylene were the dominant contributors to their chemical components. Investigation with positive matrix factorization revealed that the MPs were primarily generated by debris from packaging materials, followed by industrial and construction activities. In addition, the winter atmospheric circulation over the northwestern Siberian and Mongolian plateaus likely dominated the wide-range dispersion and deposition of the MPs across NE China. These results provide a first comprehensive perspective of MPs from sources to removal associated with snow in a large geographic region.

Unveiling the impact of environmental microplastics on mussel spermatozoa: First evidence of prothymosin-α detection in invertebrate's male gametes

Mytilus galloprovincialis mussels, like many other marine invertebrates, employ external fertilization as a mating strategy, exposing their gametes to various contaminants upon release into seawater. Environmental microplastics (EMP) are prevalent marine pollutants that pose a significant threat to aquatic biota. In this regard, our study aimed to investigate the potential effects of exposing mussels' male gametes to increasing concentrations of EMP (1, 10, 50, and 100 μg/l) collected from a Mediterranean sandy beach. We focused on assessing gamete quality by analysing physiological parameters such as viability, mitochondrial membrane potential, oxidative status, and motility. Additionally, we evaluated DNA integrity and activation of apoptosis. Furthermore, our study aimed to detect the presence of the prothymosin-α (PTMA) protein, which has never been previously investigated in invertebrate spermatozoa. Our data revealed that exposure of mussel spermatozoa to EMPs altered their oxidative status and mitochondrial membrane potential, induced a decrease in motility, DNA integrity, and an increased apoptotic occurrence, leading to a decline in overall viability. The localization of PTMA into the head and flagellum of spermatozoa further supported its presence and susceptibility to the effects of microplastics. These findings raise concerns about the reproductive capacity of mussels under environmental microplastic pollution and highlight potential long-term threats to population sustainability.

Microplastics in inland and offshore sediments in the Apulo-Lucanian region (Southern Italy)

Inland and offshore sediments from Southern Italy were studied in order to evaluate the occurrence and nature of microplastics (MPs). Inland sediments were collected in the Bradano and Basento rivers (Apulo-Lucanian region, Southern Italy), while offshore sediments were collected on the continental shelf near Bari (Adriatic Sea) and Metaponto (Ionian Sea). MPs were detected and characterized using optical microscopy, micro-Fourier-Transform Infrared spectroscopy (μ-FTIR) and micro-Raman analyses. The number of MPs present varied between 144 and 1246 kg-1 of dry sediment (468.8 ± 410,7 MPs kg-1) with a predominance of black fibers; no correlation emerged between MPs and sediment grain size. In river sediments, the occurrence of MPs is associated with local pollution, whereas the offshore occurrence of MPs depends on seasonal river flow and submarine canyons. Compositional analyses suggest that the main source of MPs in the studied sediments is sewage discharge from residential areas.

The comparative study by Raman spectroscopy of the plastic tide in the three ports of the Mediterranean Sea

This paper summarizes the field studies on marine microplastics (MPs) carried out in the autumn season in four various localisations within three ports chosen at the Mediterranean Sea near the French Riviera and the West Coast of Italy (within the Ligurian Sea). It considers the transport problem and the fate of the MPs introduced to the sea by analysing beach debris found on the shore after the stormy weather. Monitored ports included Saint-Tropez, Portoferraio and Porto Ercole, in which two different places were monitored. The aim is to approach the plastic tide phenomena by concentrating on a selected fraction of all MPs presented on the seashore. The final identification of debris was performed using Raman spectroscopy, providing a high-resolution signal. The PE, PP and PS contents were compared as the most frequent and representative polymers. Finally, we tackle the pending issue of the compound leakage from the MPs taking the environmentally aged particles from Portoferraio for further laboratory experiments and discuss an innovative approach with a low detection limit based on the electrochemical methods.

First attempt to quantify microplastics in Mediterranean Sabellaria spinulosa (Annelida, Polychaeta) bioconstructions

This work focuses on the arenaceous reefs by the polychaete Sabellaria spinulosa and addresses microplastics pollution. The main aim is to assess microplastics amount in a bioconstruction located in the Adriatic coast of Italy (Mediterranean Sea) through a comparative approach: sea-floor sediment and bioconstruction samples were analysed to quantify microplastics absolute abundance in both substrates. A total of 431 MPs were found in the investigated substrates: respectively 85 % fibers and 15 % fragments. Multivariate analysis indicates that MPs within bioconstruction occur in higher abundances and with different morphologies than in sediment samples. The analysis of bioconstruction polished sections allowed for observation of MPs agglutinated in their original position: higher concentration is reported in inter-tube areas. Results suggest that physical characteristics of MPs could play a key-role in bioconstruction inclusion processes and raise questions on effective role of sabellariid bioconstructions as a trap for this pollutant in the littoral environment.

Microplastics (≤ 10 μm) bioaccumulation in marine sponges along the Moroccan Mediterranean coast: Insights into species-specific distribution and potential bioindication

Microplastics (MPs) are pervasive in marine environments and widely recognized as emerging environmental pollutants due to the multifaceted risks they exert on living organisms and ecosystems. Sponges (Phylum Porifera) are essential suspension-feeding organisms that may be highly susceptible to MPs uptake due to their global distribution, unique feeding behavior, and sedentary lifestyle. However, the role of sponges in MP research remains largely underexplored. In the present study, we investigate the presence and abundance of MPs (≤10 μm size) in four sponge species, namely Chondrosia reniformis, Ircinia variabilis, Petrosia ficiformis, and Sarcotragus spinosulus collected from four sites along the Mediterranean coast of Morocco, as well as their spatial distribution. MPs analysis was conducted using an innovative Italian patented extraction methodology coupled with SEM-EDX detection. Our findings reveal the presence of MPs in all collected sponge specimens, indicating a pollution rate of 100%. The abundance of MPs in the four sponge species ranged from 3.95×105 to 1.05×106 particles per gram dry weight of sponge tissue, with significant differences observed among sampling sites but no species-specific differences. These results imply that the uptake of MPs by sponges is likely influenced by aquatic environmental pollution rather than the sponge species themselves. The smallest and largest MPs were identified in C. reniformis and P. ficiformis, with median diameters of 1.84 μm and 2.57 μm, respectively. Overall, this study provides the first evidence and an important baseline for the ingestion of small MP particles in Mediterranean sponges, introducing the hypothesis that they may serve as valuable bioindicators of MP pollution in the near future.

Aquatic worms: relevant model organisms to investigate pollution of microplastics throughout the freshwater-marine continuum

Plastic pollution has become a global and emergency concern. Degradation processes of plastic macrowaste, either at the millimetre- and micrometre-size scales (microplastics, MP) or a nanometre one (nanoplastic, NP), is now well documented in all environmental compartments. It is hence necessary to study the environmental dynamic of MNP (micro(nano)plastic) on aquatic macrofauna considering their dispersion in different compartments. In this context, worms, having a large habitat in natural environments (soil, sediment, water) represent a relevant model organism for MNP investigations. In aquatic systems, worms could be used to compare MNP contamination between freshwater and seawater. The aim of this review was to discuss the relevance of using worms as model species for investigating MNP pollution in freshwater, estuarine, and marine systems. In this context, studies conducted in the field and in laboratory, using diverse classes of aquatic worms (polychaete and clitellate, i.e. oligochaete and hirudinea) to assess plastic contamination, were analysed. In addition, the reliability between laboratory exposure conditions and the investigation in the field was discussed. Finally, in a context of plastic use regulation, based on the literature, some recommendations about model species, environmental relevance, and experimental needs related to MNP are given for future studies.

Abundance of microplastic in different coastal areas using Phragmatopoma caudata (Kroyer in Morch, 1863) (Polychaeta: Sabelariidae) as an indicator

Plastic debris has been reported in the marine environment since the '70s. These plastic materials are introduced into the marine environment in several sizes, one of them microplastics (MP), and they have drawn great interest and concern in the past decades. Consumption of MP can cause weight loss, feeding rate decrease, reproductive activity decrease, and several other negative effects. Ingestion of MPs has already been reported for some species of polychaetes but the use of these annelids in MP studies is still poorly reported. Costa et al. (2021) was the first study to investigate the capability of the reef-building polychaete Phragmatopoma caudata to incorporate microplastic in its colony's structures. This makes the colonies a reservoir of MP and thus they reflect the environment's quality regarding MP presence. Consequently, this specie becomes an important asset to MP pollution investigation in coastal areas. Therefore, this work aims to investigate the abundance of MPs on the coastline of Espírito Santo using P. caudata as an indicator of MP presence. For this, we collected samples of P. caudata colonies in 12 sampling sites along the Espírito Santo coast (three replicates at each site). These colony samples were processed to extract the MPs particles from the colony surface, its inner structure, and tissues from the individuals. These MPs were counted using a stereomicroscope and sorted according to their color and type (filament, fragment, and other). Statistical analysis was performed using GraphPad Prism 9.3.0. Significant values followed p < 0.05. We found MP particles in all 12 sampled beaches, configuring a pollution rate of 100 %. The number of filaments was notably greater than the number of fragments and others. The most impacted beaches were found inside the metropolitan region of the state. Finally, P. caudata is an efficient and trustable indicator of microplastic in coastal areas.

Combined toxic effects of nanoplastics and norfloxacin on mussel: Leveraging biochemical parameters and gut microbiota

Antibiotics and nanoplastics (NPs) are among the two most concerned and studied marine emerging contaminants in recent years. Given the large number of different types of antibiotics and NPs, there is a need to apply efficient tools to evaluate their combined toxic effects. Using the thick-shelled mussel (Mytilus coruscus) as a marine ecotoxicological model, we applied a battery of fast enzymatic activity assays and 16S rRNA sequencing to investigate the biochemical and gut microbial response of mussels exposed to antibiotic norfloxacin (NOR) and NPs (80 nm polystyrene beads) alone and in combination at environmentally relevant concentrations. After 15 days of exposure, NPs alone significantly inhibited superoxide dismutase (SOD) and amylase (AMS) activities, while catalase (CAT) was affected by both NOR and NPs. The changes in lysozyme (LZM) and lipase (LPS) were increased over time during the treatments. Co-exposure to NPs and NOR significantly affected glutathione (GSH) and trypsin (Typ), which might be explained by the increased bioavailable NOR carried by NPs. The richness and diversity of the gut microbiota of mussels were both decreased by exposures to NOR and NPs, and the top functions of gut microbiota that were affected by the exposures were predicted. The data fast generated by enzymatic test and 16S sequencing allowed further variance and correlation analysis to understand the plausible driving factors and toxicity mechanisms. Despite the toxic effects of only one type of antibiotics and NPs being evaluated, the validated assays on mussels are readily applicable to other antibiotics, NPs, and their mixture.

Combined toxic effects of cadmium and environmental microplastics in Aphanius fasciatus (Pisces, Cyprinodontidae)

Microplastics (MPs), plastic particles smaller than 5 mm in diameter, have received extensive attention as new environmental pollutants with still unexplored potential ecological risks. The main objective of the present study is to see if the concomitant exposure to MPs and Cd is more toxic than that to MPs or Cd separately in Aphanius fasciatus. Immature female were exposed to Cd and/or MPs for 21 days, and the subsequent effects were monitored by a combination of biochemical, histological and molecular toxicity markers. Exposure to Cd, but not to MPs, increased metallothioneins content and mRNA levels of the metallothioneins gene MTA both in liver and gills. In addition, we observed a significant oxidative stress response at histological, enzymatic (Catalase and Superoxide dismutase), non-enzymatic (proteins sulfhydryl and malondialdehyde) and gene expression levels to both toxicants in both tissues, particularly in gills, but no clear evidence for interaction between the two factors. Our results indicate a major effect of MPs on gills at different organizational levels. Finally, exposure to both MPs and Cd induced spinal deformities, although bone composition was only altered by the latter, whereas MTA mRNA bone levels were only increased realtive to controls in doubly-exposed samples. Interestingly, the simultaneous use of both pollutants produced the same effects as Cd and MPs alone, probably due to reduced bioavailability of this heavy metal.

Occurrence and risks of microplastics in the ecosystems of the Middle East and North Africa (MENA)

The ubiquitous nature of microplastics (MPs) in nature and the risks they pose on the environment and human health have led to an increased research interest in the topic. Despite being an area of high plastic production and consumption, studies on MPs in the Middle East and North Africa (MENA) region have been limited. However, the region witnessed a research surge in 2021 attributed to the COVID-19 pandemic. In this review, a total of 97 studies were analyzed based on their environmental compartments (marine, freshwater, air, and terrestrial) and matrices (sediments, water columns, biota, soil, etc.). Then, the MP concentrations and polymer types were utilized to conduct a risk assessment to provide a critical analysis of the data. The highest MP concentrations recorded in the marine water column and sediments were in the Mediterranean Sea in Tunisia with 400 items/m³ and 7960 items/kg of sediments, respectively. The number of MPs in biota ranged between 0 and 7525 per individual across all the aquatic compartments. For the air compartment, a school classroom had 56,000 items/g of dust in Iran due to the confined space. Very high risks in the sediment samples (Erⁱ > 1500) were recorded in the Caspian Sea and Arab/Persian Gulf due to their closed or semi-closed nature that promotes sedimentation. The risk factors obtained are sensitive to the reference concentration which calls for the development of more reliable risk assessment approaches. Finally, more studies are needed in understudied MENA environmental compartments such as groundwater, deserts, and estuaries.

Binational survey using Mytilus galloprovincialis as a bioindicator of microplastic pollution: Insights into chemical analysis and potential risk on humans

Microplastic (MP) contamination in edible mussels has raised concerns due to their potential risk to human health. Aiming to provide valuable insights regarding the occurrence, physicochemical characteristics, and human health implications of MP contamination, in the present study, two nationwide surveys of MP contamination in mussels (Mytilus galloprovincialis) were conducted in Morocco and Tunisia. The results indicated that MP frequency ranged from 79 % to 100 % in all the analyzed samples. The highest MP density was detected in mussels from Morocco (gills "GI": 1.88 MPs/g ww^-1; digestive glands "DG": 0.92 MPs/g ww^-1) compared to mussels of Tunisia (GI: 1.47 MPs g^{- 1}; DG: 0.79 MPs g^{- 1}). No significant differences in MP density were found between the two organs (GI and DG) for both countries. MPs were predominantly blue and black fibers, and smaller than 1000 μm. Seven polymeric types were identified, of which PET, PP, and PE were the most abundant, accounting for >87 % of all samples. Scanning Electron Microscopy (SEM) coupled with Energy dispersive X-ray (EDX) showed that most MPs have noticeable signs of weathering and inorganic components on their surface. The highest MP daily intake was found in children, while the lowest was estimated in women and men. Moreover, the annual dietary exposure of MPs through mussel consumption was estimated to be 1262.17 MPs/year in Morocco and 78.18 MPs/year in Tunisia. The potential risk assessment of MPs in mussels based on the polymer hazard index (PHI) was estimated in the high-risk levels, implying that MPs may pose health risks to humans. Overall, this research suggests that the consumption of mussels represents a considerable MP exposure route for the Moroccan and Tunisian populations.

A global snapshot of microplastic contamination in sediments and biota of marine protected areas

Microplastics (MPs) become ubiquitous contaminants in Marine Protected Areas (MPA) that have been planned as a conservation strategy. The present study provides a comprehensive overview of the occurrence, abundance, and distribution of MPs potentially affecting MPA worldwide. Data on MP occurrence and levels in sediment and biota samples were collected from recent peer-reviewed literature and screened using a GIS-based approach overlapping MP records with MPA boundaries. MPs were found in 186 MPAs, with levels ranging from 0 to 9187.5 items/kg in sediment and up to 17,461.9 items/kg in organisms. Peaked MPs concentrations occurred within multiple-use areas, and no-take MPAs were also affected. About half of MP levels found within MPA fell into the higher concentration quartiles, suggesting potential impacts on these areas. In general, benthic species were likely more affected than pelagic ones due to the higher concentrations of MP reported in the tissues of benthic species. Alarmingly, MPs were found in tissues of two threatened species on the IUCN Red List. The findings denote urgent concerns about the effectiveness of the global system of protected areas and their proposed conservation goals.

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

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

Harmful algae and pathogens on plastics in three mediterranean coastal lagoons

Plastic is now a pervasive pollutant in all marine ecosystems. The microplastics and macroplastic debris were studied in three French Mediterranean coastal lagoons (Prevost, Biguglia and Diana lagoons), displaying different environmental characteristics. In addition, biofilm samples were analyzed over the seasons to quantify and identify microalgae communities colonizing macroplastics, and determine potentially harmful microorganisms. Results indicate low but highly variable concentrations of microplastics, in relation to the period and location of sampling. Micro-Raman spectroscopy analyses revealed that the majority of macroplastic debris corresponded to polyethylene (PE) and low-density polyethylene (LDPE), and to a far lesser extent to polypropylene (PP). The observations by Scanning Electron Microscopy of microalgae communities colonizing macroplastic debris demonstrated differences depending on the seasons, with higher amounts in spring and summer, but without any variation between lagoons and polymers. Among the Diatomophyceae, the most dominant genera were Amphora spp., Cocconeis spp., and Navicula spp.. Cyanobacteria and Dinophyceae such as Prorocentrum cordatum, a potentially toxic species, were also found sporadically. The use of Primer specific DNA amplification tools enabled us to detect potentially harmful microorganisms colonizing plastics, such as Alexandrium minutum or Vibrio spp. An additional in situ experiment performed over one year revealed an increase in the diversity of colonizing microalgae in relation to the duration of immersion for the three tested polymers PE, LDPE and polyethylene terephthalates (PET). Vibrio settled durably after two weeks of immersion, whatever the polymer. This study confirms that Mediterranean coastal lagoons are vulnerable to the presence of macroplastic debris that may passively host and transport various species, including some potentially harmful algal and bacterial microorganisms.

Application of transcriptome profiling to inquire into the mechanism of nanoplastics toxicity during Ciona robusta embryogenesis

The growing concern on nanoplastics (<1 μm) impact on marine life has stimulated a significant amount of studies aiming to address ecotoxicity and disclose their mechanisms of action. Here, we applied an integrative approach to develop an Adverse Outcome Pathway (AOP) upon acute exposure to amino-modified polystyrene nanoparticles (PS-NH₂ NPs, 50 nm), as proxy for nanoplastics, during the embryogenesis of the chordate Ciona robusta. Genes related to glutathione metabolism, immune defense, nervous system, transport by aquaporins and energy metabolism were affected by either concentration tested of 10 or 15 μg mL^-1 of PS-NH₂. Transcriptomic data and in vivo experiments were assembled into two putative AOPs, identifying as key events the adhesion of PS-NH₂ as (molecular) initiating event, followed by oxidative stress, changes in transcription of specific genes, morphological defects, increase in reactive oxygen species level, impaired swimming behavior. As final adverse outcomes, altered larval development, reduced metamorphosis and inhibition of hatching were identified. Our study attempts to define AOPs for PS-NH₂ without excluding that chemicals leaching from them might also have a potential role in the observed outcome. Overall data provide new insights into the mechanism of action of PS-NH₂ NPs during chordate embryogenesis and offer further keys for a better knowledge of nanoplastics impact on early stages of marine life.

Uptake of microplastics by marine worms depends on feeding mode and particle shape but not exposure time

The uptake of microplastics into marine species has been widely documented across trophic levels. Feeding mode is suggested as playing an important role in determining different contamination loads across species, but this theory is poorly supported with empirical evidence. Here we use the two distinct feeding modes of the benthic polychaete, Hediste diversicolor (The Harbour Ragworm) (O.F. Müller, 1776), to test the hypothesis that filter feeding will lead to a greater uptake of microplastic particles than deposit feeding. Worms were exposed to both polyamide microfragments and microfibres in either water (as filter feeders) or sediment (as deposit feeders) for 1 week. No effect of exposure time was found between 1 day and 1 week (p > 0.19) but feeding mode was found to significantly affect the number of microfibres recovered from each worm (p < 0.001). When exposed to microfibers, filter feeding worms took up ≈15,000 % more fibres than deposit feeding worms (p < 0.001), whereas when feeding on microfragments there was no difference between feeding modes. Our data demonstrate that both feeding mode and particle characteristics significantly influence the uptake of microplastics by H. diversicolor. Using imaging flow cytometry, filter feeders were found to take up a broader size range of particles, with significantly more smaller and larger particles than deposit feeders (p < 0.05), commensurate with the range of plastics isolated from the guts of ragworms recovered from the environment. These results demonstrate that biological traits are useful in understanding the uptake of plastics into marine worms and warrant further exploration as a tool for understanding the bioaccessibility of plastics to marine organisms.

First assessment of microplastics in offshore sediments along the Lebanese coast, South-Eastern Mediterranean

Few studies on microplastics (MPs) in the marine environment have been conducted along the Eastern part of the Mediterranean Sea and even fewer along the Lebanese coast. This study aims to determine MPs contamination for the first-time in coastal and continental shelf sediments collected along the Lebanese shores, South-Eastern Mediterranean Sea. Sediments were collected as transects in 10 sites with a total of 23 samples between 2 and 120 m depth and suspected MPs were assessed by moving farther from land-based sources. Microplastics concentrations ranged between 0 and 4500 MPs/kg of dry sediment (1126 ± 1363 MPs/kg). Polypropylene, polyethylene, polyethylene terephthalate and polystyrene were the polymers identified on micro-Raman. Coastal landfills and raw sewage effluents were identified as the main sources and routes for MPs into the Lebanese coastal marine environment. This study serves as the first database reporting MPs in continental shelf sediments in the South-Eastern Mediterranean.

Micro(nano)plastics and plastic additives effects in marine annelids: A literature review

Plastic debris are dispersed in the marine environment and are consequently available to many organisms of different trophic levels, including sediment-dwelling organisms such as polychaetae. Plastic degradation generates micro (MPs) and nanoplastics (NPs) and as well as releases bounded plastic additives, increasing the ecotoxicological risk for marine organisms. Therefore, this review summarizes current knowledge on the accumulation and effects of MPs and NPs and plastic additives in polychaetes, derived from laboratory and field evidences. Thirty-six papers (from January 2011 to September 2021) were selected and analysed: about 80% of the selected works were published since 2016, confirming the emerging role of this topic in environmental sciences. The majority of the analysed manuscripts (68%) were carried out in the laboratory under controlled conditions. These studies showed that polychaetes accumulate and are responsive to this contaminant class, displaying behavioural, physiological, biochemical and immunological alterations. The polychaetes Hediste diversicolor and Arenicola marina were the most frequent used species to study MPs, NPs and plastic additive effects. The consideration of field studies revealed that MP accumulation was dependent on the plastic type present in the sediments and on the feeding strategy of the species. Polychaetes are known to play an important role in coastal and estuarine food webs and exposure to MPs, NPs and plastic additives may impair their behavioural, physiological, biochemical and immunological responses. Thus, the estimated global increase of these contaminants in the marine environment could affect the health of these benthic organisms, with consequences at population and ecosystem levels.

Toxicological impact of environmental microplastics and benzo[a]pyrene in the seaworm Hediste diversicolor under environmentally relevant exposure conditions

Nowadays, marine ecosystems are under severe threat from the simultaneous presence of multiple stressors, including microplastics (MPs) and polycyclic aromatic hydrocarbons (PAHs) such as benzo[a]pyrene (B[a]P). In addition to their presence in various marine compartments, there are increasing concerns on the potential capacity of MPs to sorb, concentrate and transfer these pollutants in the environment. Although their ecotoxicological impacts are currently evident, few works have studied the combined effects of these contaminants. Therefore, the major purpose of this work was to assess the toxicity of environmental relevant concentrations of MPs (<30 μm) and B[a]P, alone and in mixture, in the seaworm Hediste diversicolor by exploring their accumulation and hazardous biological effects for 3 and 7 days. Environmental MPs were able to increase B[a]P in a time-dependent manner. The obtained results showed that individual treatments, as well as co-exposure to contaminants, caused cytotoxicity and genotoxicity in the cœlomic fluid cells, while oxidative stress effects were observed at tissue and gene levels associated with alteration in neurotransmission. Overall, our findings provide additional clues about MPs as organic pollutant vectors in the marine environment, and contribute to a clearer understanding of their toxicological risk to aquatic invertebrates.

Seasonal and spatial distribution of microplastics in sediments by FTIR imaging throughout a continuum lake - lagoon- beach from the Tunisian coast

Plastics pollution in marine environment has become an issue of increasing scientific concern. This work aims to study the temporal and spatial distribution of plastics in sediments from three different Tunisian ecosystems; Rimel Beach, Bizerta lagoon and Ichkeul lake. Sediment sampling was conducted in surface (2 cm) and depth (15 cm) during spring, summer and winter. Plastics debris were separated by size fractions: macro (>5 mm), meso (1-5 mm) and microplastics (<1 mm) to optimize the time necessary for their characterisation. Macroplastics and mesoplastics were identified using an IR Attenuated total reflectance (ATR) and microplastics with Imaging Fourier transform infrared spectroscopy (FTIR) spectroscopy after an optimized extraction protocol. Results indicate that, the lowest contamination degree with macroplastics was recorded in Ichkeul lake, 2 macro debris/m² (marine protected area, national parc of Ichkeul). Mesoparticles were only detected in lagoon of Bizerte in large quantities (4900 item/kg of sediment in surface and 680 item/kg of sediment in depth) and were identified principally as paint products. For microplastics, the repartition was quite homogeneous between the three sites with an average abundance was 130.55 ± 65.61 items/kg for all seasons. The variations of microplastics abundances on the three sites could not be clearly related to the seasons. Whereas the polymer characterisation in the surface and depth sediments of the three studied areas were principally due to eight types of polymers (PVC, PET, PP, PE PS, Polyamide (PA) and polymeric methyl methacrylate (PMMA)) as reported in many other studies, surprisingly all MPs recovered in the study were smaller than 300 μm, >70 % being fragments. This study brings new results as regards to the state of plastic contamination in Tunisian coast and shows the importance of investigating different ecosystems in such studies.

Metabolomic disorders unveil hepatotoxicity of environmental microplastics in wild fish Serranus scriba (Linnaeus 1758)

Coastal areas are worldwide subject to large inputs of anthropogenic wastes that are discharged directly into inshore waters, where they will be weathered into small microplastics (MPs) of up to a size <20 μm. This study provides information about the presence of small environmental MPs (≤3 μm) in the liver of adult benthopelagic fish Serranus scriba (Linnaeus 1758), caught from three coastal regions in Tunisia distinguished by different patterns of human activity. Polymer composition in fish liver was identified using Raman microspectroscopy. Results revealed differences in the abundance, size distribution and presence of plastic additives over the investigated sites. Polyethylene-vinyl acetate (PEVA: 34% particles/g of tissue), high density polyethylene (HDPE: 24.4%) and the two smaller size classes, i.e. 3-1.2 μm and 1.2-0.45 μm, were the most abundant MPs types and size distribution found, respectively, in Bizerte channel (BC) site (Bizerte city, Tunisia). Moreover, at hepatic level data showed a significant site-dependent cytotoxicity expressed by changes in malondialdehyde (MDA) content, presence of reactive oxygen species (ROS) expressed by altered level of catalase (CAT) and glutathione-S-transferase (GST) activities and in the content of metallothioneins (MTs), as well as genotoxicity by changes in the amount of micronucleus (MN), and neurotoxicity by altered activity of acetylcholinesterase (AChE). A innovative metabolomics analysis was also performed to further investigate the distinct patterns of key metabolite changes in the liver of Serranus scriba. A total of 36 metabolites were significantly affected, mainly involved in energy, amino acid and osmolyte metabolism. These findings emphasised for the first time a close relationship between the source, abundance and size ranges of environmental MPs ≤ 3 μm and their hepatotoxicity in wild organisms.

Fractal analysis highlights analogies in arenaceous tubes of Sabellaria alveolata (Metazoa, Polychaeta) and agglutinated tests of foraminifera (Protista)

Bioconstructions of Sabellaria alveolata (Polychaeta Sabellariidae) from southern Sicily (Central Mediterranean) were sampled and analysed through a multidisciplinary approach in order to unravel the construction pattern of arenaceous tubes and explore possible analogies existing between the worm tubes and the agglutinated tests of benthic foraminifera (Protista). Scanning Electron Microscopy and Energy Dispersive Spectroscopy analyses were carried out on entire tubes as well as sectioned ones. Results show that arenaceous tubes are built following a rigorous architectural framework, based on selection and methodical arrangement of the agglutinated grains, and show surprising analogies with the test microstructure previously observed in agglutinated foraminifera. The grain distribution detected in both model species bioconstructions was analysed using a fractal numerical model (Hausdorff fractal dimension). Collected data show that in both organisms the grains were distributed according to a fractal model, indicating that the evolutionary process may have led to finding the same optimal constructive strategy across organisms with an independent evolutionary history, notwithstanding different geometrical scales. Furthermore, in sectioned tubes we observed microplastic fragments agglutinated within the arenaceous wall and in the inter-tube area. This unexpected finding shows that marine animals can be affected by microplastic pollution not only in soft tissues, but also engineered hard structures, and suggests the problem is more pervasive than estimated so far.

Impact of environmental microplastics alone and mixed with benzo[a]pyrene on cellular and molecular responses of Mytilus galloprovincialis

The hazard of microplastic (MP) pollution in marine environments is a current concern. However, the effects of environmental microplastics combined with other pollutants are still poorly investigated. Herein, impact of ecologically relevant concentrations of environmental MP alone (50 µg/L) or combined with B[a]P (1 µg/L) was assessed in mussel Mytilus galloprovincialis after a short-term exposure (1 and 3 days) to environmental MP collected from a north-Mediterranean beach. Raman Microspectroscopy (RMS) revealed bioaccumulation in mussel hemolymph of MP, characterized by polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), polyethylene vinyl acetate (PEVA) and high-density polyethylene (HDPE), with abundance of MP sized 1.22-0.45 µm. An increase of B[a]P was detected in mussels after 3-day exposure, particularly when mixed with MP. Both contaminants induced cytotoxic and genotoxic effects on hemocytes as determined by lysosomal membrane stability (LMS), micronuclei frequency (FMN), and DNA fragmentation rate by terminal dUTP nick-end labeling (TUNEL). About apoptosis/DNA repair processes, P53 and DNA-ligase increased at 1-day exposure in all conditions, whereas after 3 days increase of bax, Cas-3 and P53 and decrease of Bcl-2 and DNA-ligase were revealed, suggesting a shift towards a cell apoptotic event in exposed mussels. Overall, this study provides new insights on the risk of MP for the marine ecosystem, their ability to accumulate xenobiotics and transfer them to marine biota, with potential adverse repercussion on their health status.

pH-responsive magnetic artificial melanin with tunable aggregation-induced stronger magnetism for rapid remediation of plastic fragments

The global occurrence of plastic fragment pollutants in water resources has raised concerns about food safety, drinking water security, and long-term ecological impacts worldwide. The different chemical nature, the persistence, and the smaller size make micro-plastics accumulators for toxins that pose a potential threat to human health. Generally, the smaller the size of the plastic fragments is, the more difficult it is to remove them from the aquatic environment. Methods to remove plastics from water or other media are highly needed. Here, we develop core-shell superparamagnetic melanin nanoparticles, which can put magnetism on nano-/micro-plastics within 30 s and then rapidly remove them from water by applying an external magnetic field. The shell material (artificial nano-melanin) provides simultaneously attractive electrostatic, hydrophobic interaction, and van der Waals' forces to attract nano-/micro-plastics, which plays a key role in the rapid remediation of the plastic fragments. With this principle applied to a simple method, the average removal efficiency achieves 89.3%. We show a method for high-throughput remediation of various micro-plastics with simple materials and processes, which have the potential for rapid, green, and large-scale remediation in the future.

Microplastics in seawater and marine organisms: Site-specific variations over two-year study in Giglio Island (North Tyrrhenian Sea)

Geographical and temporal differences of microplastic occurrence were documented in water and fish collected in 2017 and 2019 from the Giglio Island (North Tyrrhenian Sea) close to the area where the Costa Concordia sank in January 2012. Results on water samples showed a site-dependent difference, suggesting the role of surface current dynamics in the microplastic local distribution, while tested Neuston nets (200 μm and 330 μm mesh size) did not influence microplastic retention efficiency. Fish exhibited in 2019 a higher frequency of specimens positive to microplastic ingestion with respect to 2017, with an occurrence higher than those typically observed in other Mediterranean areas. Both in water and fish, fragments were the dominating shape, polypropylene and polyethylene were the prevalent polymers, without particular difference between sites and years. This study highlights the importance of applying microplastic investigation in biotic and abiotic matrices for an effective monitoring of this pollution in the marine environment.

Determination of the microplastic content in Mediterranean benthic macrofauna by pyrolysis-gas chromatography-tandem mass spectrometry

The Mediterranean Sea water bodies are ones of the most polluted, especially with microplastics. As the seafloor is the ultimate sink for litter, it is considered a hotspot for microplastic pollution. We provide an original analytical development based on the coupling of tandem mass spectrometry to pyrolysis-gas chromatography to improve the detection of plastic contamination in marine organisms. Due to the high selectivity of the mass spectrometer, a straightforward sample preparation consists uniquely of potassium hydroxide digestion. The quantification of six common polymers is possible in one run. The method was applied to analyze the plastic content from 500 μm down to 0.7 μm in the whole body of seven benthic species with variable feeding modes. Plastic was detected in all samples, with an almost systematic detection of polypropylene and polyethylene. Our method presents a major development in determining the levels of plastic contaminations in samples with rich organic matter content.

Identification and Quantification of Microplastics in the Marine Environment Using the Laser Direct Infrared (LDIR) Technique

Here, we evaluate for the first time the performances of the newly developed laser direct infrared (LDIR) technique and propose an optimization of the initial protocol for marine microplastics (MPs) analysis. Our results show that an 8 μm porosity polycarbonate filter placed on a Kevley slide enables preconcentration and efficient quantification of MPs, as well as polymer and size determination of reference plastic pellets of polypropylene (PP), polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET), with recoveries ranging from 80-100% and negligible blank values for particle sizes ranging from 200 to 500 μm. A spiked experiment using seawater, sediment, mussels, and fish stomach samples showed that the method responded linearly with significant slopes (R² ranging from 0.93-1.0; p < 0.001, p < 0.01). Overall, 11 polymer types were identified with limited handling and an analysis time of ca. 3 h for most samples and 6 h for complex samples. Application of this technique to Mediterranean marine samples (seawater, sediment, fish stomachs and mussels) indicated MP concentrations and size distribution consistent with the literature. A high predominance of PVC (sediment, fish stomachs) and PE and PP (seawater, mussels) was observed in the analyzed samples.

Autophagic event and metabolomic disorders unveil cellular toxicity of environmental microplastics on marine polychaete Hediste diversicolor

Although the hazards of microplastics (MPs) have been quite well explored, the aberrant metabolism and the involvement of the autophagy pathway as an adverse response to environmental MPs in benthic organisms are still unclear. The present work aims to assess the impact of different environmental MPs collected from the south coast of the Mediterranean Sea, composed by polyethylene (PE), polyethylene vinyl acetate (PEVA), low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP) and polyamide (PA) on the metabolome and proteome of the marine polychaete Hediste diversicolor. As a result, all the microplastic types were detected with Raman microspectroscopy in polychaetes tissues, causing cytoskeleton damage and induced autophagy pathway manifested by immunohistochemical labeling of specific targeted proteins, through Tubulin (Tub), Microtubule-associated protein light chain 3 (LC3), and p62 (also named Sequestosome 1). Metabolomics was conducted to further investigate the metabolic alterations induced by the environmental MPs-mixture in polychaetes. A total of 28 metabolites were differentially expressed between control and MPs-treated polychaetes, which showed elevated levels of amino acids, glucose, ATP/ADP, osmolytes, glutathione, choline and phosphocholine, and reduced concentration of aspartate. These novel findings extend our understanding given the toxicity of environmental microplastics and unravel their underlying mechanisms.

Exposure to microplastics leads to a defective ovarian function and change in cytoskeleton protein expression in rat

Microplastics (MPs) are ubiquitous environmental contaminants; through their physicochemical properties, they can have potentially negative effects on the environment as well as on animal and human health. Studies addressing the toxicity of MPs on mammalian female reproduction are almost absent. Thus, the main objective of the present study was to assess the impact of oral exposure, during four estrous cycles, of 5 µm polystyrene-type microplastics (PS-MPs) on ovarian function in rats. Particles of PS-MPs were detected in the duodenum and, for the first time, in the different compartments of the ovarian tissue. The toxicity of accumulated PS-MPs was manifested by the reduced relative ovarian weights, by the alteration in the folliculogenesis and in the estrous cycle duration, and by the reduced serum concentration of estradiol. The defective ovarian function following PS-MP treatment might be due to the induction of oxidative stress, which has been proved by an increased malondialdehyde (MDA) concentration and an increased superoxide dismutase (SOD) and catalase (CAT) activities as well as a decreased protein sulfhydryl (PSH) level in the rat ovary. Importantly, by immunofluorescence and RT-PCR, we demonstrated a significant decrease in the expression of cytoskeletal proteins: α-tubulin and disheveled-associated activator of morphogenesis (DAAM-1) in the ovary of rats exposed to PS-MPs at proteomic and transcriptomic levels. Our results uncovered, for the first time, the distribution and accumulation of PS-MPs across rat ovary, revealed a significant alteration in some biomarkers of the ovarian function, and highlighted the possible involvement of MP-induced disturbance of cytoskeleton in these adverse effects.

Interactive effects of environmental microplastics and 2,4-dichlorophenoxyacetic acid (2,4-D) on the earthworm Eisenia andrei

Given the wide use of plastic and pesticides in agriculture, microplastics (MP) and the herbicide 2,4 dichloro-phenoxy-acetic acid (2-4-D) can be present simultaneously in soil. Nevertheless, little is known about their combined toxicity. In this study, Eisenia andrei was exposed to environmental MP (100 µg kg^-1 soil) and 2,4-D (7 mg kg^-1 soil) for 7 and 14 days. Bioaccumulation, genotoxicity, oxidative stress and gene expression level were assessed. Results revealed that MP increased 2,4-D bioaccumulation in earthworms. Simultaneous exposure to both these pollutants caused a significant reduction in lysosomal membrane stability (LMS) and an increase in micronuclei (MNi) frequency. Biochemical analysis revealed oxidative alterations in earthworms exposed to all treatments; being very pronounced in earthworms exposed to the mixture in terms of increase in glutathione-S-Transferase (GST), catalase (CAT) and malondialdehydes accumulation (MDA). Furthermore, an up-regulation in cat and gst expression level was recorded in worms exposed to single or mixture treatment, except MP in case of gst. Our data highlight the toxicity of the combined exposure to MP and 2,4-D and afford new insights into the potential ecological risks posed by MP in terrestrial ecosystems.

Microplastics in the abyss: a first investigation into sediments at 2443-m depth (Toulon, France)

Plastic and microplastic pollutions are known to be widespread across the planet in all types of environments. However, relatively little about microplastic quantities in the deeper areas of the oceans is known, due to the difficulty to reach these environments. In this work, we present an investigation of microplastic (<5 mm) distribution performed in the bottom sediments of the abyssal plain off the coast and the canyon of Toulon (France). Four samples of deep-sea sediment were collected at the depth of 2443 m during the sea operations carried out by the French oceanographic cruises for the KM3NeT project. The chemical and physical characterisation of the sediment was carried out, and items were extracted from sediments by density separation and analysed by optical microscope and µRaman spectroscopy. Results show microplastics in the deep-sea sediments with a concentration of about 80 particles L^-1, confirming the hypothesis of microplastics spread to abyssal sediments in the Mediterranean Sea.

Assessment of seasonal variability of input of microplastics from the Northern Dvina River to the Arctic Ocean

Northern Dvina River is one of the largest rivers in the European Arctic flowing into the White Sea through the populated regions with developed industry. Floating plastics include microplastics (0.5-5 mm) and mesoplastics (5-25 mm) were observed on seasonal variations in the Northern Dvina River mouth. The samples were collected every month from September to November 2019 and from May to October 2020 with a Neuston net that was togged 3 nautical miles in the Korbel'nyy Branch of the River delta. Chemical composition of the plastic particles was determined using a Fourier transmission infrared spectrometer. The majority of the microplastics were identified as polyethylene 52.6%, followed by polypropylene 36.8%. After estimating the export fluxes of microplastics from the Northern Dvina River to the Arctic, there is no significant seasonal variation of the river export of microplastics. The microplastics export rate during the spring flood period in May turned out to be maximum, 58 items/s, while the minimum discharge was in September with a value of 9 items/s. The average weight concentration of microplastics was 18.5 μg/m³, which is higher than it was found in the Barents Sea - 12.5 μg/m³ and several times higher than in the Eurasian Arctic on average - 3.7 μg/m³. These results indicate that the Northern Dvina River is being one of the main sources of microplastic pollution of the White and the Barents Seas.

Interaction of Microplastics with Antibiotics in Aquatic Environment: Distribution, Adsorption, and Toxicity

As two major types of pollutants of emerging concerns, microplastics (MPs) and antibiotics (ATs) coexist in aquatic environments, and their interactions are a source of increasing concern. Therefore, this work examines the interaction mechanisms of MPs and ATs, and the effect of MPs on ATs bioavailability and antibiotic resistance genes (ARGs) abundance in aquatic environments. First, the mechanisms for ATs adsorption on MPs are summarized, mainly including hydrophobic, hydrogen-bonding, and electrostatic interactions. But other possible mechanisms, such as halogen bonding, CH/π interaction, cation-π interaction, and negative charge-assisted hydrogen bonds, are newly proposed to explain the observed ATs adsorption. Additionally, environmental factors (such as pH, ionic strength, dissolved organic matters, minerals, and aging conditions) affecting ATs adsorption by MPs are specifically discussed. Moreover, MPs could change the bioaccumulation and toxicity of ATs to aquatic organisms, and the related mechanisms on the joint effect are reviewed and analyzed. Furthermore, MPs can enrich ARGs from the surrounding environment, and the effect of MPs on ARGs abundance is evaluated. Finally, research challenges and perspectives for MPs-ATs interactions and related environmental implications are presented. This review will facilitate a better understanding of the environmental fate and risk of both MPs and ATs.

Personal protective equipment (PPE) pollution associated with the COVID-19 pandemic along the coastline of Agadir, Morocco

The increasing use of personal protective equipment (PPE) as a sanitary measure against the new coronavirus (SARS-CoV-2) has become a significant source of many environmental risks. The majority of the governments enforce the use of PPE in public areas, such as beaches. Thus, the use and disposal of PPE have compromised most solid waste management strategies, ultimately leading to the occurrence of PPE polluting the marine environment. The present study aimed to monitor the PPE pollution associated with COVID-19 along the coastline of Agadir, Morocco. In parallel, the influence of the activities carried out in each sampled beach before and after the lockdown break was reported. Overall, a total number of 689 PPE items were identified, with a mean density of 1.13 × 10^-5 PPE m^-2 (0-1.21 × 10^-4 PPE m^-2). The majority of the PPE items found were face masks (96.81%), out of which 98.4% were surgical masks and 1.6% were reusable cloth masks. The most polluted sites were the beaches with recreational activities, followed by surfing, and fishing as the main activity. Importantly, PPE density increased significantly after lockdown measures. Additionally, the discarded PPE sampled in the supralittoral zone was higher than PPE recorded in the intertidal zone. This confirms that PPE items are driven by the beachgoers during their visit. PPE items are a source of microplastic and chemical pollutants, a substrate to invasive species colonization, and a potential threat of entanglement, ingestion, and/or infection among apex predators. In the specific case of Agadir beaches, significant efforts are required to work on the lack of environmental awareness and education. It is recommended to improve beach cleaning strategies and to penalize incorrect PPE disposal. Additional alternatives may be adopted, as the involvement of biodegradable materials in PPE manufacturing, recycling through pyrolysis, and encouraging reusable and washable masks.

Generation of nanoplastics during the photoageing of low-density polyethylene

In this work, we studied the hydrolytic and photochemical degradation of three low-density polyethylene (LDPE) materials, within the size range of microplastics (MP). The MPs were exposed to mechanical agitation and UV irradiation equivalent to one year of solar UVB + UVA in a stirred photoreactor. Flow cytometry was used to track the formation of small (1-25 μm) MPs by applying Mie's theory to derive the size of MP particles from scattering intensity readings. The calculation was based on a calibration with polystyrene (PS) beads. The results showed that the generation of 1-5 μm MP reached 10⁴-10⁵ MPs in the 1-25 μm range per gram of LDPE. ATR-FTIR and micro-FTIR measurements evidenced the formation of oxygenated moieties, namely hydroxyl, carbonyl, and carbon-oxygen bonds, which increased with irradiation time. We also found evidence of the production of a high number of nanoplastics (<1 μm, NPs). The Dynamic Light Scattering size of secondary NPs was in the hundreds of nm range and might represent up to 10¹⁰ NPs per gram of LDPE. Our results allowed the unambiguous spectroscopic assessment of the generation of NPs from LDPE under conditions simulating environmental exposure to UV irradiation and used flow cytometry for the first-time to track the formation of secondary MPs.

Field evidence for microplastic interactions in marine benthic invertebrates

Microplastics represent an important issue of concern for marine ecosystems worldwide, and closed seas, such as the Mediterranean, are among the most affected by this increasing threat. These pollutants accumulate in large quantities in benthic environments causing detrimental effects on diverse biocenoses. The main focus of this study is on the ‘polychaetes-microplastics’ interactions, particularly on two species of benthic polychaetes with different ecology and feeding strategies: the sessile and filter feeder Sabella spallanzanii (Gmelin, 1791) and the vagile carnivorous Hermodice carunculata (Pallas, 1766). Since not standardized protocols are proposed in literature to date, we compared efficiencies of diverse common procedures suitable for digesting organic matter of polychaetes. After the definition of an efficient digestion protocol for microplastics extraction for both polychaetes, our results showed high microplastics ingestion in both species. Microplastics were found in 42% of individuals of S. spallanzanii, with a mean of 1 (± 1.62) microplastics per individual, in almost all individuals of H. carunculata (93%), with a mean of 3.35 (± 2.60). These significant differences emerged between S. spallanzanii and H. carunculata, is probably due to the diverse feeding strategies. The susceptibility to this pollutant makes these species good bioindicators of the impact of microplastics on biota.

Chemical Analysis of Microplastics and Nanoplastics: Challenges, Advanced Methods, and Perspectives

Microplastics and nanoplastics have become emerging particulate anthropogenic pollutants and rapidly turned into a field of growing scientific and public interest. These tiny plastic particles are found in the environment all around the globe as well as in drinking water and food, raising concerns about their impacts on the environment and human health. To adequately address these issues, reliable information on the ambient concentrations of microplastics and nanoplastics is needed. However, micro- and nanoplastic particles are extremely complex and diverse in terms of their size, shape, density, polymer type, surface properties, etc. While the particle concentrations in different media can vary by up to 10 orders of magnitude, analysis of such complex samples may resemble searching for a needle in a haystack. This highlights the critical importance of appropriate methods for the chemical identification, quantification, and characterization of microplastics and nanoplastics. The present article reviews advanced methods for the representative mass-based and particle-based analysis of microplastics, with a focus on the sensitivity and lower-size limit for detection. The advantages and limitations of the methods, and their complementarity for the comprehensive characterization of microplastics are discussed. A special attention is paid to the approaches for reliable analysis of nanoplastics. Finally, an outlook for establishing harmonized and standardized methods to analyze these challenging contaminants is presented, and perspectives within and beyond this research field are discussed.

Microplastics (MPs) Act as Sources and Vector of Pollutants-Impact Hazards and Preventive Measures

Currently, people are paying more and more attention to the interaction between microplastics (MPs) and chemical substances (including metals and organic substances), so it is necessary to understand the relationship between MPs and chemical substances. In this review, we explored (1) MPs may become a source of chemical substances. (2) MPs can also be used as a carrier for attaching pollutants. (3) No matter what role MPs play, MPs and the attached chemical substances will have harmful effects on biological systems. However, because the current research is not deep enough, more experimental areas are needed to explore the interaction mechanism and the principle of toxicity. In addition, laws and policies need to be developed that actively promote and strive to develop biodegradable alternative microplastics to reduce the harm of microplastics and their additives to the environment.

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.

New methodologies for the detection, identification, and quantification of microplastics and their environmental degradation by-products

Sampling, separation, detection, and characterization of microplastics (MPs) dispersed in natural water bodies and ecosystems is a challenging and critical issue for a better understanding of the hazards for the environment posed by such nearly ubiquitous and still largely unknown form of pollution. There is still the need for exhaustive, reliable, accurate, reasonably fast, and cost-efficient analytical protocols allowing the quantification not only of MPs but also of nanoplastics (NPs) and of the harmful molecular pollutants that may result from degrading plastics. Here a set of newly developed analytical protocols, integrated with specialized techniques such as pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS), for the accurate and selective determination of the polymers most commonly found as MPs polluting marine and freshwater sediments are presented. In addition, the results of an investigation on the low molecular weight volatile organic compounds (VOCs) released upon photo-oxidative degradation of microplastics highlight the important role of photoinduced fragmentation at a molecular level both as a potential source of hazardous chemicals and as accelerators of the overall degradation of floating or stranded plastic debris.

Abundance, composition, and fate of microplastics in water, sediment, and shellfish in the Tapi-Phumduang River system and Bandon Bay, Thailand

Microplastic contamination in the environment is a global problem, as evidenced by the increasing amount of research worldwide. To our knowledge, this study is the first to investigate the microplastic distribution in Bandon Bay, one of the most important maricultural areas of Thailand. Water and sediment samples from the Tapi-Phumduang River system (n = 10) and Bandon Bay (n = 5) were collected. Water sampling at the river mouth was carried out during a complete tidal cycle to estimate the microplastic flux to the bay during the wet season. Moreover, two commercial bivalve species grown in the bay, the green mussel (Perna viridis) and lyrate Asiatic hard clam (Meretrix lyrata), were analyzed. More items of microplastics were found in the river system than in the bay. During the tide cycle, one-third of the microplastics entering the bay were washed back upstream during high tide. This backflow consisted mainly of larger microplastics. The average daily load of microplastics to the bay was 22.4 × 10⁹ items day^-1. The load during low tide was approximately 4-5 times higher than that during high tide. The overall accumulation of microplastics in the bottom sediments of the river and in the bay was similar (p < 0.05). Green mussels showed significantly higher contamination with microplastics than clams. Notably, the small-sized shellfish contained more particles (items/g) than the large ones (p < 0.05). Fibers were detected in virtually all samples: water (98%), sediment (94%), mussels (100%), and clams (95%). Among these, microfibers (<1 mm) were detected in water (71%), sediment (63%), green mussels (63%), and clams (52%). Blue and white particles were the two most frequently observed colors, while the most dominant polymers were rayon, followed by polypropylene (PP) or polyethylene (PE), polyethylene terephthalate (PET), and nylon. To this end, we posit that river discharge was a significant source of microplastics in Bandon Bay, with minor additional contributions from fishing and mariculture activities within the bay. Ultimately, these microplastics may end up in the sediments and living organisms.

Bacterial community profiling of floating plastics from South Mediterranean sites: First evidence of effects on mussels as possible vehicles of transmission

Plastic wastes accumulation in marine environments is becoming a crucial issue; while the toxicity to biota is quite well explored, a gap of knowledge still exists on the role that plastics play in shaping bacterial community structures in marine conditions and their possible transmission to humans. The present study intended first to profile bacterial community structure in floating plastic particles (FP) biofilms and seawater from four Tunisian coastal areas using high-throughput sequencing (HTS) of 16S rDNA. Subsequently, mussels (Mytilus galloprovincialis) as filter feeding organisms were exposed to the FP to broaden the knowledge on the potential role played by environmental plastic particles in shaping bacterial community structures and on their possibility to act as vehicles of bacteria through the food web. The mussels' microbiota was microbiologically analyzed through HTS, and the Histidine Rich Glycoprotein (HRG) gene expression level was investigated as the main immune response. Our results clearly showed a great variation in the composition of bacterial communities of FP and seawater from different geographical areas. Moreover, the gills of mussels exposed to sterilized seawater and native FP from each site exhibited a wider bacterial biodiversity. The gene expression level of HRG was found to be significantly higher in animals exposed to native FP when compared to sterilized FP. Our results should be carefully considered in view of the Trojan horse effects of FP toward bacteria and its potential toxicity.