Microplastic does not magnify the acute effect of PAH pyrene on predatory performance of a tropical fish (Lates calcarifer)

Temporal patterns in multiple stressors shape the vulnerability of overwintering Arctic zooplankton

The Arctic polar nights bring extreme environmental conditions characterised by cold and darkness, which challenge the survival of organisms in the Arctic. Additionally, multiple anthropogenic stressors can amplify the pressure on the fragile Arctic ecosystems during this period. Determining how multiple anthropogenic stressors may affect the survival of Arctic life is crucial for ecological risk assessments and management, but this topic is understudied. For the first time, our study investigates the complex interactions of multiple stressors, exploring stressor temporal dynamics and exposure duration on a key Arctic copepod Calanus glacialis during the polar nights. We conducted experiments with pulse (intermittent) and press (continuous) exposure scenarios, involving microplastics, pyrene and warming in a fully factorial design. We observed significant effects on copepod survival, with pronounced impacts during later stressor phases. We also detected two-way interactions between microplastics and pyrene, as well as pyrene and warming, further intensified with the presence of a third stressor. Continuous stressor exposure for 9 days (press-temporal scenario) led to greater reductions in copepod survival compared to the pulse-temporal scenario, characterised by two 3-day stressor exposure phases. Notably, the inclusion of recovery phases, free from stressor exposure, positively influenced copepod survival, highlighting the importance of temporal exposure dynamics. We did not find behaviour to be affected by the different treatments. Our findings underscore the intricate interactions amongst multiple stressors and their temporal patterns in shaping the vulnerability of overwintering Arctic copepods with crucial implications for managing Arctic aquatic ecosystems under the fastest rate of ongoing climate change on earth.

Effects of salinity on naphthalene adsorption and toxicity of polyethylene microparticles on Artemia salina

Plastic pollution in aquatic ecosystems is increasing and plastic particles may adsorb and transport a diverse array of contaminants, thereby increasing their bioavailability to biota. This investigation aimed to evaluate the effects of varying polyethylene microplastics (PE MPs) and naphthalene (NAPH) concentrations on the survival and feeding rates of the model organism, Artemia salina, as well as NAPH adsorption to microplastics at different salinity levels (17, 75, 35.5 and 52.75 g L-1) under selected climate change scenarios. Survival (48 h) and feeding rates (6 h) of A. salina were also monitored, revealing that the presence of higher PE and NAPH concentrations lead to decreased survival rates while also increasing the number and size of microplastic particles in the saline solutions. Higher PE concentrations negatively affected A. salina feeding rates and NAPH concentrations were positively correlated with particle number and size, as well as with NAPH and PE adsorption rates in solution. Our findings demonstrate that the co-occurrence of microplastics and NAPH in aquatic environments can result in detrimental zooplankton survival and feeding rate effects. Furthermore, this interaction may contribute to the accumulation of these contaminants in the environment, highlighting the need to simultaneously monitor and mitigate the presence of microplastics and organic pollutants, like NAPH, in aquatic environments.

Occurrence, transport, and toxicity of microplastics in tropical food chains: perspectives view and way forward

Microplastics, which have a diameter of less than 5 mm, are becoming an increasingly prevalent contaminant in terrestrial and aquatic ecosystems due to the dramatic increase in plastic production to 390.7 million tonnes in 2021. Among all the plastics produced since 1950, nearly 80% ended up in the environment or landfills and eventually reached the oceans. Currently, 82-358 trillion plastic particles, equivalent to 1.1-4.9 million tonnes by weight, are floating on the ocean's surface. The interactions between microorganisms and microplastics have led to the transportation of other associated pollutants to higher trophic levels of the food chain, where microplastics eventually reach plants, animals, and top predators. This review paper focuses on the interactions and origins of microplastics in diverse environmental compartments that involve terrestrial and aquatic food chains. The present review study also critically discusses the toxicity potential of microplastics in the food chain. This systematic review critically identified 206 publications from 2010 to 2022, specifically reported on microplastic transport and ecotoxicological impact in aquatic and terrestrial food chains. Based on the ScienceDirect database, the total number of studies with "microplastic" as the keyword in their title increased from 75 to 4813 between 2010 and 2022. Furthermore, various contaminants are discussed, including how microplastics act as a vector to reach organisms after ingestion. This review paper would provide useful perspectives in comprehending the possible effects of microplastics and associated contaminants from primary producers to the highest trophic level (i.e. human health).

Gut toxicity of polystyrene microplastics and polychlorinated biphenyls to Eisenia fetida: Single and co-exposure effects with a focus on links between gut bacteria and bacterial translocation stemming from gut barrier damage

Microplastics' (MPs) ability to sorb and transport polychlorinated biphenyls (PCBs) in soil ecosystems warrants significant attention. Although organisms mainly encounter pollutants through the gut, the combined pollution impact of MPs and PCBs on soil fauna gut toxicity remains incompletely understood. Consequently, this study examined the gut toxicity of polystyrene MPs (PS-MPs) and PCB126 on Eisenia fetida, emphasizing the links between gut bacteria and bacterial translocation instigated by gut barrier impairment. Our findings underscored that E. fetida could ingest PS-MPs, which mitigated the PCB126 accumulation in E. fetida by 9.43 %. Exposure to PCB126 inhibited the expression of gut tight junction (TJ) protein genes. Although the presence of PS-MPs attenuated this suppression, it didn't alleviate gut barrier damage and bacterial translocation in the co-exposure group. This group demonstrated a significantly increased level of gut bacterial load (BLT, ANOVA, p = 0.005 vs control group) and lipopolysaccharide-binding protein (LBP, ANOVA, all p < 0.001 vs control, PCB, and PS groups), both of which displayed significant positive correlations with antibacterial defense. Furthermore, exposure to PS-MPs and PCB126, particularly within the co-exposure group, results in a marked decline in the dispersal ability of gut bacteria. This leads to dysbiosis (Adonis, R2 = 0.294, p = 0.001), with remarkable signature taxa such as Janthinobacterium, Microbacterium and Pseudomonas, being implicated in gut barrier dysfunction. This research illuminates the mechanism of gut toxicity induced by PS-MPs and PCB126 combined pollution in earthworms, providing novel insights for the ecological risk assessment of soil.

Limited impact of weathered residues from the Deepwater Horizon oil spill on the gut-microbiome and foraging behavior of sheepshead minnows (Cyprinodon variegatus)

The Deepwater Horizon disaster of April 2010 was the largest oil spill in U.S. history and exerted catastrophic effects on several ecologically important fish species in the Gulf of Mexico (GoM). Within fish, the microbiome plays a key symbiotic role in maintaining host health and aids in acquiring nutrients, supporting immune function, and modulating behavior. The aim of this study was to examine if exposure to weathered oil might produce significant shifts in fish gut-associated microbial communities as determined from taxa and genes known for hydrocarbon degradation, and whether foraging behavior was affected. The gut microbiome (16S rRNA and shotgun metagenomics) of sheepshead minnow (Cyprinodon variegatus) was characterized after fish were exposed to oil in High Energy Water Accommodated Fractions (HEWAF; tPAH = 81.1 ± 12.4 µg/L) for 7 days. A foraging behavioral assay was used to determine feeding efficiency before and after oil exposure. The fish gut microbiome was not significantly altered in alpha or beta diversity. None of the most abundant taxa produced any significant shifts as a result of oil exposure, with only rare taxa showing significant shifts in abundance between treatments. However, several bioindicator taxa known for hydrocarbon degradation were detected in the oil treatment, primarily Sphingomonas and Acinetobacter. Notably, the genus Stenotrophomonas was detected in high abundance in 16S data, which previously was not described as a core member of fish gut microbiomes. Data also demonstrated that behavior was not significantly affected by oil exposure. Potential low bioavailability of the oil may have been a factor in our observation of minor shifts in taxa and no behavioral effects. This study lays a foundation for understanding the microbiome of captive sheepshead minnows and indicates the need for further research to elucidate the responses of the fish gut-microbiome under oil spill conditions.

Impact of mixing energy and dispersant dosage on oil dispersion and sedimentation with microplastics in the marine environment

Recently, the fate of spilled oil in the presence of microplastics (MPs) in the sea has attracted attention of researchers. Merey crude oil and polyethylene terephthalate (PET) were used as the experimental materials in this study. The effects of mixing energy and dispersant dosage on oil dispersion and sedimentation in the presence of MPs in the water column were investigated by laboratory experiments simulating actual sea conditions. The increase of mixing energy showed a promoting effect on oil dispersion. When the oscillation frequency increased from 140 rpm to 180 rpm, the oil dispersion efficiency (ODE) ranged from 2.1 %-3.7 % to 17.4 %-30.8 %, and the volumetric mean diameter (VMD) of the suspended oil droplets/MPs-oil agglomerates (MOA) decreased from 99.9-131.4 μm to 76.6-88.2 μm after 2 h oscillation. The application of chemical dispersant led to an increase in both the quantity and size of the formed sunken MPs-oil-dispersant agglomerates (MODA). At the dispersant-to-oil ratio (DOR) of 1:5, the ODE declined from 77.7 % to 62.6 % when the MPs concentration increased from 0 to 150 mg/L, while the oil sinking efficiency (OSE) rose from 3.4 % to 15.6 % when the MPs increased from 25 to 150 mg/L; the maximum size of the sunken MODA reached 13.0 mm, and the total volume of the MODA formed per unit volume oil reached 389.7 μL/mL oil at the MPs concentration of 150 mg/L. Meanwhile, the results showed that the presence of MPs inhibited the oil dispersion by increasing the oil-water interfacial tension. The outcomes of this work may provide assistance in predicting the transport of spilled oil and developing emergency measures.

Functional Trait-Based Evidence of Microplastic Effects on Aquatic Species

Microplastics represent an ever-increasing threat to aquatic organisms. We merged data from two global scale meta-analyses investigating the effect of microplastics on benthic organisms' and fishes' functional traits. Results were compared, allowing differences related to vertebrate and invertebrate habitat, life stage, trophic level, and experimental design to be explored. Functional traits of aquatic organisms were negatively affected. Metabolism, growth, and reproduction of benthic organisms were impacted, and fish behaviour was significantly affected. Responses differed by trophic level, suggesting negative effects on trophic interactions and energy transfer through the trophic web. The experimental design was found to have the most significant impact on results. As microplastics impact an organism's performance, this causes indirect repercussions further up the ecological hierarchy on the ecosystem's stability and functioning, and its associated goods and services are at risk. Standardized methods to generate salient targets and indicators are urgently needed to better inform policy makers and guide mitigation plans.

Microplastic exposure and consumption increases susceptibility to gyrodactylosis and host mortality for a freshwater fish

Microplastics have been found in all surveyed ecosystems and in the diet of multiple species. Detrimental health impacts of microplastic consumption include reduced growth and fecundity, metabolic stress and immune alterations for both invertebrates and vertebrates. Limited information exists, however, on how disease resistance may be affected by microplastic exposure and consumption. Here, the impact of microplastic (0.01 and 0.05 mg l-1 of polypropylene) on fish host susceptibility to disease and mortality was assessed using the guppy Poecilia reticulata-gyrodactylid Gyrodactylus turnbulli system. Fish exposed to and/or consuming microplastic at both concentrations demonstrated significantly higher pathogen burdens over time compared with fish fed a plastic-free diet. Furthermore, microplastic (at both tested concentrations) was associated with increased mortality events for fish within all treatments, regardless of host infection status. This study adds to the growing body of evidence showing that microplastic pollution can be detrimental to fish welfare by reducing disease resistance.

How plastic debris and associated chemicals impact the marine food web: A review

Contamination from plastic debris is omnipresent in marine environments, posing a substantial risk to marine organisms, food webs and the ecosystem. The overlap between the size range of marine plastic pollution with prey means that plastics are readily available for consumption by organisms at all trophic levels. Large plastic debris can directly result in the death of larger marine organisms, through entanglement, strangulation, choking and starvation through a false sense of satiation. Whereas smaller plastic debris, such as micro- and nano-plastics can have adverse impact to marine organisms due to their large surface area to volume ratio and their ability to translocate within an organism. Various physiological processes are reported to be impacted by these small contaminants, such as feeding behaviour, reproductive outputs, developmental anomalies, changes in gene expression, tissue inflammation and the inhibition of growth and development to both adults and their offspring. Micro- and nano-plastics are still relatively poorly understood and are considered a hidden threat. Plastic is a complex contaminant due to the diversity in sizes, shapes, polymer compositions, and chemical additives. These factors can each have unique and species-specific impacts. Consumption of plastics can occur directly, through ingestion and indirectly, through trophic transfer, entanglement of prey, adherence of plastics to external surfaces, and adherence of organisms to the external surfaces of plastics. This review investigated the intrusion of plastics into the marine food web and the subsequent consequences of plastic pollution to marine biota.The objective of this review was to identify the complexity of impacts to marine organisms through the food web from plastic contamination. Through a concise analysis of the available literature the review has shown that plastic pollution and their associated additives can adversely impact environmental and biological health.

Microplastics induce neurotoxicity in aquatic animals at environmentally realistic concentrations: A meta-analysis

Microplastics (MPs) draw international attention owing to their widespread distribution in water ecosystems, but whether MPs cause neurotoxic effects in aquatic animals at environmentally realistic concentrations is still controversial. This meta-analysis recompiled 35 studies to determine whether MPs could change the levels of brain (in vivo) neurotransmitters in aquatic animals at environmentally realistic concentrations (≤1 mg/L, median = 0.100 mg/L). Then, a group comparison was conducted to compare the effects of different factors on the effect size and to explore the significant factors affecting the neurotoxicity of MPs. The results demonstrated that MP exposure could considerably decrease the levels of acetylcholinesterase (AchE) in the brain of aquatic animals by 16.2%. However, the effects of MPs on cholinesterase (CHE), acetylcholine (ACh), dopamine (DA) and γ-aminobutyric acid (GABA) were not statistically significant due to the small number of studies and samples. The neurotoxicity of MPs was closely linked with particle size and exposure time but independent of animal species, MP compositions, MP morphology and MP concentrations. Further literatures review indicated that MP-induced neurotoxicity and behavioral changes are related with multiple biological processes, including nerve damage, oxidative stress, intestinal flora disturbance and metabolic disorder. Furthermore, some factors influencing MP neurotoxicity in the real environment (e.g. the aging of MPs, the release of MP additives, and the co-exposure of MPs and pollutants) were discussed. Overall, this study preliminarily explored whether MPs induced changes in neurotoxicity-related indicators in aquatic animals through meta-analysis and provided scientific evidence for evaluating the health risks and neurotoxicity of MPs at the environmental level.

Potential of microplastics participate in selective bioaccumulation of low-ring polycyclic aromatic hydrocarbons depending on the biological habits of fishes

Currently, although the cumulative effects of microplastics (MPs) and organic pollutants (OPs) in the environment and within organisms are being investigated, whether and how MPs participate in bioaccumulation of OPs based on a carrier effect is still unclear. In the present study, water and aquatic organisms were collected from the Pearl River. Polycyclic aromatic hydrocarbons (PAHs) and MPs were separated by solid phase extraction and were measured by gas chromatography mass spectrometry and Fourier transform infrared spectroscopy, respectively. Higher PAH concentrations at the river outlet and higher MPs abundance in the inner river were observed, indicating a mismatched distribution between PAHs and MPs. No correlation between MP abundance and PAH concentration in fishes was detected, implying that MPs exerted limited influence on PAH concentrations. Interestingly, bioconcentration factors of one major low-ring PAH (phenanthrene) in fishes showed a significant correlation with MPs abundance, implying that although MPs did not affect the variation in PAH concentrations, they potentially participated in selective bioaccumulation of PAHs. Moreover, significant correlations between MPs abundance and PAHs in fishes with different feeding and living habits were found, indicating that MPs' participation in PAH bioaccumulation was dependent on fish biology and life history. Furthermore, the health risk posed by PAHs in fishes at the river outlet surpassed the line of potential high risk, while the ecological risk posed by MPs at the inner river was in the danger category, indicating the ecological risks posed by PAHs and MPs are uneven along the Pearl River. These findings deepen our understanding of the underlying mechanism of MPs participating in selective bioaccumulation of low-ring PAHs in fishes based on fish biology and point out the present risks posed by these two pollutants in the Pearl River and its estuary, which contribute to aquatic environmental protection and fishery production in this region.

Microplastic contamination in large migratory fishes collected in the open Atlantic Ocean

Fishes are one of the most important components of the oceans and are exposed to several anthropogenic pressures, namely microplastic (MP), contaminants that are now ubiquitous worldwide. Taking advantage of the 2020 Circumnavigation Expedition carried by the NRP Sagres tall ship of the Portuguese Navy, fish samples from the southern Atlantic ocean were collected to evaluate possible MP contamination. In a total of 14 weeks of campaign, seven large migratory fishes of commercial interest were collected across the middle Atlantic Ocean and along the South American Atlantic coast. All individuals were contaminated with MPs, with an average of 18 ± 11 MPs/fish. In all fish sampled, both the gastrointestinal tract and gills presented MPs, indicating different contamination pathways including via their preys and from surrounding water, respectively. A total of 124 MPs were observed, where 72 % were fibers and 28 % particles, mostly of blue color (85 %), and with rayon and nylon as the most abundant polymers. This study is an important contribution to increase the scientific knowledge of MP contamination in mesopelagic fishes used for human consumption and collected in the open waters, reinforcing the need for further research regarding MP contamination in top predatory species from high trophic levels.

Microplastics increases the heat tolerance of Daphnia magna under global warming via hormetic effects

The ecological risk assessment of microplastics under global warming receives increasing attention. Yet, such studies mostly focused on increased mean temperatures (MT), ignoring another key component of global warming, namely daily temperature fluctuations (DTF). Moreover, we know next to nothing about the combined effects of multigenerational exposure to microplastics and warming. In this study, Daphnia magna was exposed to an environmentally relevant concentration of polystyrene microplastics (5 μg L-1) under six thermal conditions (MT: 20 ℃, 24 ℃; DTF: 0 ℃, 5 ℃, 10 ℃) over two generations to investigate the interactive effects of microplastics and global warming. Results showed that microplastics had no effects on Daphnia at standard thermal conditions (constant 20 °C). Yet, microplastics increased the fecundity, heat tolerance, amount of energy storage, net energy budget and cytochrome P450 activity, and decreased the energy consumption when tested under an increased MT or DTF, indicating a hormesis effect induced by microplastics under warming. The unexpected increase in heat tolerance upon exposure to microplastics could be partly explained by the reduced energy consumption and/or increased energy availability. Overall, the present study highlighted the importance of including DTF and multigenerational exposure to improve the ecological risk assessment of microplastics under global warming.

Screening of polymer types and chemical weathering in macro- and meso-plastics found on lake and river beaches using a combined chemometric approach

In the environment, synthetic polymers, commonly known as "plastics", are well-known to undergo various chemical weathering processes, which modify their surface chemistry by introducing new functional groups. Such changes are important to monitor, as they can severely influence the toxicity caused by plastic debris. Therefore, in this study, two chemometric models are proposed to accelerate the chemical classification of macro- and meso-plastics found in the environment. For this purpose, principal component analysis (PCA) and hierarchical cluster analysis (HCA) were applied on preprocessed infrared spectra of 83 plastic fragments found on public lake and river beaches. HCA associated all beach samples with a known plastic, whereas PCA enabled the association of only 39.8% (33 out of 83) of the beach samples with a known plastic. However, both techniques agreed on 93.9% of the samples identified. According to PCA and HCA results, polypropylene and polyethylene were the most frequently identified polymers in the samples. PCA turned out to be a very promising tool for fast screening of weathered plastics, since the distance of samples from the polypropylene cluster in the PCA plot was correlated with weathering. This was later confirmed by employing other characterization techniques such as micro-Raman, X-ray photoelectron spectroscopy and scanning electron microscopy. Finally, future experiments should focus on the applicability of the proposed combined chemometric approach for very small microplastics (<100 μm), as they have more important effects than larger plastics on aquatic ecosystems.

Overviewing the Ground Reality of Microplastic Effects on Seafoods, Including Fish, Shrimps and Crabs: Future Research Directions

While plastics are already notorious for their accumulation in the environment, which poses environmental challenges, invisible microplastics (MPS) are an even greater challenge. This review focuses on consolidating the reports available on MP accumulation in edible marine and freshwater fishes, shrimps, and crabs. The reality as to whether MPs in these edible aquatic organisms are really a cause of high concern is questioned and discussed. While the entrails of aquatic organisms are reported to contain high levels of MPs, because these products are consumed after the removal of the entrails and gut area in the majority of cases, the MP threat is questionable. The existence of MPs in these aquatic sources is validated but their potency in harming humans, aquatic organisms, and other interlinked species is unassessed. To overcome the difficulty in tracing the movement of MPs in a bigger ecosystem, this review proposes laboratory-based pilot studies mimicking real-world conditions, which will help us to understand the kinetics of MPs in the food chain. The effects of MPs on human welfare and health are yet to be assessed, and this is another gap that needs attention.

Effects of the Antidepressant Amitriptyline on Juvenile Brown Trout and Their Modulation by Microplastics

Pharmaceuticals such as antidepressants are designed to be bioactive at low concentrations. According to their mode of action, they can also influence non-target organisms due to the phylogenetic conservation of molecular targets. In addition to the pollution by environmental chemicals, the topic of microplastics (MP) in the aquatic environment came into the focus of scientific and public interest. The aim of the present study was to investigate the influence of the antidepressant amitriptyline in the presence and absence of irregularly shaped polystyrene MP as well as the effects of MP alone on juvenile brown trout (Salmo trutta f. fario). Fish were exposed to different concentrations of amitriptyline (nominal concentrations between 1 and 1000 µg/L) and two concentrations of MP (104 and 105 particles/L; <50 µm) for three weeks. Tissue cortisol concentration, oxidative stress, and the activity of two carboxylesterases and of acetylcholinesterase were assessed. Furthermore, the swimming behavior was analyzed in situations with different stress levels. Exposure to amitriptyline altered the behavior and increased the activity of acetylcholinesterase. Moreover, nominal amitriptyline concentrations above 300 µg/L caused severe acute adverse effects in fish. MP alone did not affect any of the investigated endpoints. Co-exposure caused largely similar effects such as the exposure to solely amitriptyline. However, the effect of amitriptyline on the swimming behavior during the experiment was alleviated by the higher MP concentration.

Emerging bio-dispersant and bioremediation technologies as environmentally friendly management responses toward marine oil spill: A comprehensive review

Marine oil spills emanating from wells, pipelines, freighters, tankers, and storage facilities draw public attention and necessitate quick and environmentally friendly response measures. It is sometimes feasible to contain the oil with booms and collect it with skimmers or burn it, but this is impracticable in many circumstances, and all that can be done without causing further environmental damage is adopting natural attenuation, particularly through microbial biodegradation. Biodegradation can be aided by carefully supplying biologically accessible nitrogen and phosphorus to alleviate some of the microbial growth constraints at the shoreline. This review discussed the characteristics of oil spills, origin, ecotoxicology, health impact of marine oils spills, and responses, including the variety of remedies and responses to oil spills using biological techniques. The different bioremediation and bio-dispersant treatment technologies are then described, with a focus on the use of green surfactants and their advances, benefits/drawbacks. These technologies were thoroughly explained, with a timeline of research and recent studies. Finally, the hurdles that persist as a result of spills are explored, as well as the measures that must be taken and the potential for the development of existing treatment technologies, all of which must be linked to the application of integrated procedures.

Ecotoxic effects of microplastics and contaminated microplastics - Emerging evidence and perspective

The high prevalence and persistence of microplastics (MPs) in pristine habitats along with their accumulation across environmental compartments globally, has become a matter of grave concern. The resilience conferred to MPs using the material engineering approaches for outperforming other materials has become key to the challenge that they now represent. The characteristics that make MPs hazardous are their micro to nano scale dimensions, surface varied wettability and often hydrophobicity, leading to non-biodegradability. In addition, MPs exhibit a strong tendency to bind to other contaminants along with the ability to sustain extreme chemical conditions thus increasing their residence time in the environment. Adsorption of these co-contaminants leads to modification in toxicity varying from additive, synergistic, and sometimes antagonistic, having consequences on flora, fauna, and ultimately the end of the food chain, human health. The resulting environmental fate and associated risks of MPs, therefore greatly depend upon their complex interactions with the co-contaminants and the nature of the environment in which they reside. Net outcomes of such complex interactions vary with core characteristics of MPs, the properties of co-contaminants and the abiotic factors, and are required to be better understood to minimize the inherent risks. Toxicity assays addressing these concerns should be ecologically relevant, assessing the impacts at different levels of biological organization to develop an environmental perspective. This review analyzed and evaluated 171 studies to present research status on MP toxicity. This analysis supported the identification and development of research gaps and recommended priority areas of research, accounting for disproportionate risks faced by different countries. An ecological perspective is also developed on the environmental toxicity of contaminated MPs in the light of multi-variant stressors and directions are provided to conduct an ecologically relevant risk assessment. The presented analyses will also serve as a foundation for developing environmentally appropriate remediation methods and evaluation frameworks.

Large size (>100-μm) microplastics are not biomagnifying in coastal marine food webs of British Columbia, Canada

Microplastics (MPs) contamination in marine environments is of increasing concern, as plastic particles are globally ubiquitous across ecosystems. A large variety of aquatic taxa ingest MPs, but the extent to which animals accumulate and transfer MPs through food webs is largely unknown. In this study, we quantified MP uptake in bivalves, crabs, echinoderms, and fish feeding at different trophic levels at three sites on southern Vancouver Island. We paired stable-isotope food web analysis with MP concentrations in digestive tracts across all trophic levels and in fish livers. We then used Bayesian generalized linear mixed models to explore whether bioaccumulation and biomagnification were occurring. Our results showed that MPs (100-5000 μm along their longest dimension) are not biomagnifying in marine coastal food webs, with no correlation between the digestive tract or fish liver MP concentrations and trophic position of the various species. Ecological traits did, however, affect microplastic accumulation in digestive tracts, with suspension feeder and smaller-bodied planktivorous fish ingesting more MPs by body weight. Trophic transfer occurred between prey and predator for rockfish, but higher concentrations in full stomachs compared with empty ones suggested rapid excretion of ingested MPs. Collectively, our findings suggested the movement of MP through marine food webs is facilitated by species-specific mechanisms, with contamination susceptibility a function of species biology, not trophic position. Furthermore, the statistical methods we employ, including machine learning for classifying unknown particles and a probabilistic way to account for background contamination, are universally applicable to the study of microplastics. Our findings advance understanding of how MPs enter and move through aquatic food webs, suggesting that lower-trophic-level animals are more at risk of ingesting >100-μm MPs, relative to higher-trophic-level animals. Our work also highlights the need to advance the study of <100-μm MPs, which are still poorly understood and may need to be considered separately in ecological risk assessments.

The ecotoxicological consequences of microplastics and co-contaminants in aquatic organisms: a mini-review

Microplastics (MPs, <5 mm in size) are a grave environmental concern. They are a ubiquitous persistent pollutant group that has reached into all parts of the environment - from the highest mountain tops to the depths of the ocean. During their production, plastics have added to them numerous chemicals in the form of plasticizers, colorants, fillers and stabilizers, some of which have known toxicity to biota. When released into the environments, MPs are also likely to encounter chemical contaminants, including hydrophobic organic contaminants, trace metals and pharmaceuticals, which can sorb to plastic surfaces. Additionally, MPs have been shown to be ingested by a wide range of organisms and it is this combination of ingestion and chemical association that gives weight to the notion that MPs may impact the bioavailability and toxicity of both endogenous and exogenous co-contaminants. In this mini-review, we set the recent literature within what has been previously published about MPs as chemical carriers to biota, with particular focus on aquatic invertebrates and fish. We then present a critical viewpoint on the validity of laboratory-to-field extrapolations in this area. Lastly, we highlight the expanding 'microplastic universe' with the addition of anthropogenic particles that have gained recent attention, namely, tire wear particles, nanoplastics and, bio-based or biodegradable MPs, and highlight the need for future research in their potential roles as vehicles of co-contaminant transfer.

Promotion of the biodegradation of phenanthrene adsorbed on microplastics by the functional bacterial consortium QY1 in the presence of humic acid: Bioavailability and toxicity evaluation

The adsorption of hydrophobic organic compounds (HOCs) by microplastics (MPs) has attracted great attention in recent years. However, the ultimate environmental fate of the HOCs sorbed on MPs (HOCs-MPs) is poorly understood. In this work, we investigated the potential influence of the biotransformation process on the environmental fate of phenanthrene (PHE, a model HOC) sorbed on MPs (PHE-MPs) under the existence of humic acid (HA, the main ingredient of dissolved organic matter (DOM)) in the aquatic environment. The results indicated that the adsorption behavior of PHE on MPs decreased its bioavailability and thus inhibited its biotransformation efficiency. However, HA significantly promoted the biodegradation rate and percentage of PHE-MPs. This was probably because HA improved the desorption of PHE from MPs, which promoted the acquisition of PHE by bacteria from the aqueous phase. Further, HA dramatically increased the bacterial community diversity and richness and altered the community composition. The richness of some PHE-degrading bacteria, such as Methylobacillus and Sphingomonas, significantly increased, which may also be an important factor for promoting PHE biodegradation. Molecular ecological network analysis implied that HA enhanced the modularity and complexity of bacterial interaction networks, which was beneficial to maintaining the functional stability of the consortium QY1. Besides, HA decreased the cytotoxicity of functional microbes induced by HOCs-MPs. This work broadens our knowledge of the environmental fate of HOCs-MPs and interactions of MPs, HOCs, DOMs and functional microbial consortiums in aqueous environments.

Recent advances in toxicological research and potential health impact of microplastics and nanoplastics in vivo

As emerging pollutants, direct and indirect adverse impacts of micro(nano)plastics (MPs/NPs) are raising an increasing environmental concern in recent years due to their poor biodegradability and difficulty in recycling. MPs/NPs can act as carriers of bacteria, viruses, or pollutants (such as heavy metals and toxic organic compounds), and may potentially change the toxicity and bioavailability of pollutants. Ingested or attached MPs/NPs can also be transferred from low-trophic level organisms to high-nutrient organisms or even the human body through the food chain transfer process. This article reviews the emerging field of micro- and nanoplastics on organisms, including the separate toxicity and toxicity of compound after the adsorption of organic pollutants or heavy metals, as well as possible mechanism of toxicological effects and evaluate the nano- and microplastics potential adverse effects on human health. The inherent toxic effects MPs/NPs mainly include the following: physical injury, growth performance decrease and behavioral alteration, lipid metabolic disorder, induced gut microbiota dysbiosis and disruption of the gut's epithelial permeability, neurotoxicity, damage of reproductive system and offspring, oxidative stress, immunotoxicity, etc. Additionally, MPs/NPs may release harmful plastic additives and toxic monomers such as bisphenol A, phthalates, and toluene diisocyanate. The vectors' effect also points out the potential interaction of MPs/NPs with pollutants such as heavy metals, polycyclic aromatic hydrocarbons, organochlorine pesticides, polychlorinated biphenyls, perfluorinated compounds, pharmaceuticals, and polybrominated diphenyl ethers. Nevertheless, these potential consequences of MPs/NPs being vectors for contaminants are controversial.

Alleviation of Tris(2-chloroethyl) Phosphate Toxicity on the Marine Rotifer Brachionus plicatilis by Polystyrene Microplastics: Features and Molecular Evidence

As emerging pollutants, microplastics (MPs) and organophosphorus esters (OPEs) coexist in the aquatic environment, posing a potential threat to organisms. Although toxicological studies have been conducted individually, the effects of combined exposure are unknown since MPs can interact with OPEs acting as carriers. In this study, we assessed the response of marine rotifer, Brachionus plicatilis, to co-exposure to polystyrene MPs and tris(2-chloroethyl) phosphate (TCEP) at different concentrations, including population growth, oxidative status, and transcriptomics. Results indicated that 0.1 μm and 1 μm MPs were accumulated in the digestive system, and, even at up to 2000 μg/L, they did not exert obvious damage to the stomach morphology, survival, and reproduction of B. plicatilis. The presence of 1 μm MPs reversed the low population growth rate and high oxidative stress induced by TCEP to the normal level. Some genes involved in metabolic detoxification and stress response were upregulated, such as ABC and Hsp. Subsequent validation showed that P-glycoprotein efflux ability was activated by combined exposure, indicating its important role in the reversal of population growth inhibition. Such results challenge the common perception that MPs aggravate the toxicity of coexisting pollutants and elucidate the molecular mechanism of the limited toxic effects induced by MPs and TCEP.

The M/V X-Press Pearl Nurdle Spill: Contamination of Burnt Plastic and Unburnt Nurdles along Sri Lanka’s Beaches

In May 2021, the M/V X-Press Pearl cargo ship caught fire 18 km off the west coast of Sri Lanka and spilled ∼1680 tons of spherical pieces of plastic or "nurdles" (∼5 mm; white in color). Nurdles are the preproduction plastic used to manufacture a wide range of end products. Exposure to combustion, heat, and chemicals led to agglomeration, fragmentation, charring, and chemical modification of the plastic, creating an unprecedented complex spill of visibly burnt plastic and unburnt nurdles. These pieces span a continuum of colors, shapes, sizes, and densities with high variability that could impact cleanup efforts, alter transport in the ocean, and potentially affect wildlife. Visibly burnt plastic was 3-fold more chemically complex than visibly unburnt nurdles. This added chemical complexity included combustion-derived polycyclic aromatic hydrocarbons. A portion of the burnt material contained petroleum-derived biomarkers, indicating that it encountered some fossil-fuel products during the spill. The findings of this research highlight the added complexity caused by the fire and subsequent burning of plastic for cleanup operations, monitoring, and damage assessment and provides recommendations to further understand and combat the impacts of this and future spills.

Seeking for a perfect (non-spherical) microplastic particle - The most comprehensive review on microplastic laboratory research

In recent decades, much attention has been paid to microplastic pollution, and research on microplastics has begun to grow exponentially. However, microplastics research still suffers from the lack of standardized protocols and methods for investigation of microplastics under laboratory conditions. Therefore, in this review, we summarize and critically discuss the results of 715 laboratory studies published on microplastics in the last five years to provide recommendations for future laboratory research. Analysis of the data revealed that the majority of microplastic particles used in laboratory studies are manufactured spheres of polystyrene ranging in size from 1 to 50 µm, that half of the studies did not characterize the particles used, and that a minority of studies used aged particles, investigated leaching of chemicals from microplastics, or used natural particles as a control. There is a large discrepancy between microplastics used in laboratory research and those found in the environment, and many laboratory studies suffer from a lack of environmental relevance and provide incomplete information on the microplastics used. We have summarized and discussed these issues and provided recommendations for future laboratory research on microplastics focusing on (i) microplastic selection, (ii) microplastic characterization, and (iii) test design of laboratory research on microplastics.

Effects of ingestion of polyethylene microplastics on survival rate, opercular respiration rate and swimming performance of African catfish (Clarias gariepinus)

The study evaluated the impact of ingestion of microplastics on accumulation, survival, opercular respiratory rate (ORR), and swimming performance of Clarias gariepinus, the African freshwater catfish exposed to polyethylene microplastics. Juveniles were exposed for 4 days to 50-500 µm low-density polyethylene (LDPE) microplastics at four different concentrations (0.5, 1.0, 1.5, and 2.0 g/L). After 4 days of exposure, the concentration of microplastics in the gastrointestinal tract (GIT) of the fish increased with increasing concentrations of microplastics. Mean weights of microplastics in the GIT of the fish ranged from 0.0025 ± 0.001 g to 0.054 ± 0.01 g, suggesting that the fish were unable to detect and avoid ingesting the microplastics. No mortality was observed in all the treatment concentrations except in the highest concentration (2 g/L) where 10% mortality was observed. The results showed that ORR increased in a concentration and time-dependent manner. Compared with the control group, the swimming speed, travel distance and movement patterns of the fish exposed to microplastics were significantly reduced (p < 0.05). Therefore, this study helps understand the environmental impact of microplastics on C. gariepinus in freshwater environments.

The Role of the Ecotoxicology Applied to Seafood as a Tool for Human Health Risk Assessments Concerning Polycyclic Aromatic Hydrocarbons

Background: Polycyclic aromatic hydrocarbons (PAHs) are persistent pollutants routinely detected in aquatic ecosystems. It is, therefore, necessary to assess the link between deleterious marine biota PAH effects, especially in commercialized and consumed animals, environmental health status, and potential human health risks originating from the consumption of contaminated seafood products. Thus, this review seeks to verify the relationships of ecotoxicological studies in determining effect and safety concentrations on animals routinely consumed by humans. Methods: A total of 52 published studies between 2011 and 2021, indexed in three databases, were selected following the PICO methodology, and information on test animals, evaluated PAH, and endpoints were extracted. Results: Benzo(a)pyrene and phenanthrene were the most investigated PAHs in terms of biomarkers and test organisms, and mussels were the most evaluated bioindicator species, with an emphasis on reproductive responses. Furthermore, despite the apparent correlation between environmental PAH dynamics and effects on aquatic biota and human health, few assessments have been performed in a multidisciplinary manner to evaluate these three variables together. Conclusions: The links between human and environmental sciences must be strengthened to enable complete and realistic toxicity assessments as despite the application of seafood assessments, especially to mussels, in bioassays, the connection between toxicological animal responses and risks associated with their consumption is still understudied.

Impact of polypropylene microplastics and chemical pollutants on European sea bass (Dicentrarchus labrax) gut microbiota and health

Plastic pollution has become a global problem for marine ecosystems. Microplastics (MPs) are consumed by several marine organisms, including benthic and pelagic fish species that confuse them with food sources, thus contributing to bioaccumulation along the food chain. In addition to structural intestinal damage, ingestion of MPs represents a pathway for fish exposure to potentially hazardous chemicals, too. Most of them are endocrine disrupters, genotoxic or induce immune depression in fish. Accordingly, we assessed the combined toxicological effects of microplastics (MPs) and adsorbed pollutants by adding them to marine fish diet. European sea bass (Dicentrarchus labrax) juveniles were fed for 60 days with feeds containing polypropylene MPs, either virgin or contaminated with chemical pollutants (a blend of dichlorodiphenyldichloroethylene, chlorpyrifos, and benzophenone-3). The data demonstrated a synergic action of MPs and chemical pollutants to induce an inflammatory-like response in distal intestine of sea bass as shown by the up regulation of cytokine il-6 and tnf-α expression. Morphological analysis detected the presence of a focus of lymphocytes in anterior and posterior intestinal segments of fish fed with contaminants in the diet. With regard to microbiota, significant changes in bacterial species richness, beta diversity, and composition of gut microbiota were observed as a consequence of both pollutants and polluted MPs ingestion. These perturbations in gut microbial communities, including the reduction of beneficial lactic acid bacteria and the increase in potential pathogenic microorganism (Proteobacteria and Vibrionales), were undeniable signs of intestinal dysbiosis, which in turn confirmed the signs of inflammation caused by pollutants, especially when combined with MPs. The results obtained in this study provide, therefore, new insights into the potential risks of ingesting MPs as pollutant carriers in marine fish.

Warming, temperature fluctuations and thermal evolution change the effects of microplastics at an environmentally relevant concentration

Microplastics are sometimes considered not harmful at environmentally relevant concentrations. Yet, such studies were conducted under standard thermal conditions and thereby ignored the impacts of higher mean temperatures (MT), and especially daily temperature fluctuations (DTF) under global warming. Moreover, an evolutionary perspective may further benefit the future risk assessment of microplastics under global warming. Here, we investigated the effects of two generations of exposure to an environmentally relevant concentration of polystyrene microplastics (5 μg L^-1) under six thermal conditions (2 MT × 3 DTF) on the life history, physiology, and behaviour of Daphnia magna. To assess the impact of thermal evolution we thereby compared Daphnia populations from high and low latitudes. At the standard ecotoxic thermal conditions (constant 20 °C) microplastics almost had no effect except for a slight reduction of the heartbeat rate. Yet, at the challenging thermal conditions (higher MT and/or DTF), microplastics affected each tested variable and caused an earlier maturation, a higher fecundity and intrinsic growth rate, a decreased heartbeat rate, and an increased swimming speed. These effects may be partly explained by hormesis and/or an adaptive response to stress in Daphnia. Moreover, exposure to microplastics at the higher mean temperature increased the fecundity and intrinsic growth rate of cold-adapted high-latitude Daphnia, but not of the warm-adapted low-latitude Daphnia, suggesting that thermal evolution in high-latitude Daphnia may buffer the effects of microplastics under future warming. Our results highlight the critical importance of DTF and thermal evolution for a more realistic risk assessment of microplastics under global warming.

Polystyrene microplastics increase estrogenic effects of 17α-ethynylestradiol on male marine medaka (Oryzias melastigma)

Microplastics (MPs) and endocrine disrupting chemicals are ubiquitous pollutants in marine environments, but their combined ecological risk is unclear. This study exposed male marine medaka (Oryzias melastigma) to 10 ng/L 17α-ethynylestradiol (EE₂) alone or EE₂ plus 2, 20, and 200 μg/L polystyrene MPs for 28 days to investigate the impacts of MPs on the reproductive disruption of EE₂. The results showed that 10 ng/L EE₂ alone did not affect biometric parameters, while co-exposure to EE₂ and 20, 200 μg/L MPs suppressed the growth and decreased gonadosomatic and hepatosomatic indices. Compared to EE₂ alone, EE₂ plus MPs exposure significantly increased plasma 17β-estradiol (E₂) levels in a dose-dependent manner, and co-exposure to EE₂ and 20, 200 μg/L MPs significantly increased the ratios of E₂/testosterone (T). Moreover, EE₂ plus MPs exposure elevated the transcription levels of estrogen biomarker genes vitellogenin and choriogenin, and estrogen receptor (ERα and ERβ). Morphological analysis also showed that co-exposure to EE₂ and MPs induced more severe damage to the testes and livers, indicating that MPs increased the toxicity of EE₂. The actual EE₂ concentrations in the solution increased with the exposure concentrations of MPs, suggesting that MPs changed the fate and behavior of EE₂ in the seawater. These findings demonstrate that MPs could increase the estrogenic effects of EE₂ on marine fish, suggesting that the combined health risk of MPs and endocrine disrupting chemicals on marine organisms should be paid great attention.

Environmentally relevant concentrations of microplastics influence the locomotor activity of aquatic biota

The occurrence of microplastics (MPs) in various marine and freshwater matrices has attracted great attention. However, the effect of MPs in natural environment on the locomotor performance of aquatic biota is still controversial. Therefore, this meta-analysis was conducted, involving 116 effect sizes from 2347 samples, to quantitatively evaluate the alteration in locomotor behavior of aquatic organisms induced by MPs at environmentally relevant concentrations (≤ 1 mg/L, median = 0.125 mg/L). It was shown that MP exposure significantly inhibited the average speed and moved distance of aquatic organisms by 5% and 8% (p < 0.05), respectively, compared with the control, resulting in an obvious reduction of locomotor ability by 6% (p < 0.05). Egger's test indicated that the results were stable without publication bias (p > 0.05). The complex influence of MPs on the locomotor ability were characterized through random-effects meta-regression analyses, presenting size-, time-, concentration-dependent manners and multi-factors interactions. In addition, several physiological changes, including energy reserve reduction, metabolism disorder, gut microbiota dysbiosis, inflammation response, neurotoxic response, and oxidative stress, of aquatic organisms triggered by MP exposure at environmentally relevant concentrations were also provided, which might account for the MPs-induced locomotor activity decline.

Are microplastics destabilizing the global network of terrestrial and aquatic ecosystem services?

Plastic has created a new man-made ecosystem called plastisphere. The plastic pieces including microplastics (MPs) and nanoplastics (NPs) have emerged as a global concern due to their omnipresence in ecosystems and their ability to interact with the biological systems. Nevertheless, the long-term impacts of MPs on biotic and abiotic resources are not completely understood, and existing evidence suggests that MPs are hazardous to various keystones species of the global biomes. MP-contaminated ecosystems show reduced floral and faunal biomass, productivity, nitrogen cycling, oxygen-generation and carbon sequestration, suggesting that MPs have already started affecting ecological biomes. However, not much is known about the influence of MPs towards the ecosystem services (ESs) cascade and its correlation with the biodiversity loss. MPs are perceived as a menace to the global ecosystems, but their possible impacts on the provisional, regulatory, and socio-economic ESs have not been extensively studied. This review investigates not only the potentiality of MPs to perturb the functioning of terrestrial and aquatic biomes, but also the associated social, ecological and economic repercussions. The possible long-term fluxes in the ES network of terrestrial and aquatic niches are also discussed.

A review of human and animals exposure to polycyclic aromatic hydrocarbons: Health risk and adverse effects, photo-induced toxicity and regulating effect of microplastics

Polycyclic aromatic hydrocarbons (PAHs) are one of the most widely distributed persistent organic pollutants (POPs) in the environmental media. PAHs have been widely concerned due to their significant health risk and adverse effects to human and animals. Currently, the main sources of PAHs in the environment are the incomplete combustion of fossil fuels, as well as municipal waste incineration and agricultural non-surface source emissions. In this work, the scope of our attention includes 16 typical PAHs themselves without involving their metabolites and industrial by-products. Exposure of human and animals to PAHs can lead to a variety of adverse effects, including carcinogenicity and teratogenicity, genotoxicity, reproductive- and endocrine-disrupting effects, immunotoxicity and neurotoxicity, the type and severity of which depend on a variety of factors. On the other hand, the regulatory effect of microplastics (MPs) on the bio-toxicity and bioaccumulation capacity of PAHs has now gradually attracted attention. We critically reviewed the adsorption capacity and mechanisms of MPs on PAHs as well as the effects of MPs on PAHs toxicity, thus highlighting the importance of paying attention to the joint bio-toxicity caused by PAHs-MPs interactions. In addition, due to the extensive nature of the common exposure pathway of PAHs and ultraviolet ray, an accurate understanding of biological processes exposed to both PAHs and UV light is necessary to develop effective protective strategies. Finally, based on the above critical review, we highlighted the research gaps and pointed out the priority of further studies.

Size-dependent adverse effects of microplastics on intestinal microbiota and metabolic homeostasis in the marine medaka (Oryzias melastigma)

Microplastic (MP) is an emerging environmental pollutant and exposure to MPs has been associated with numerous adverse health outcomes in both wild and laboratory animals. The toxicity of MPs depends on concentration, exposure time, chemical composition and size distribution, but the impacts of particle size remain inconclusive yet. In this study, adult marine medaka (Oryzias melastigma) were exposed to different size of polystyrene MPs (PS-MPs) with concentration of 10 mg/L for 60 days and the growth performance, lipid metabolism, immune parameters and gut microbiome were determined. Results indicated that particle size is a dominant factor causing lipid metabolism disorders and hepatic toxicity in PS-MPs-exposed fish. The bodyweight, adipocyte size and hepatic lipid contents were significantly increased in 200 μm PS-MPs-exposed fish, while 2 and 10 μm PS-MPs-exposed fish exhibited liver injury principally manifested asthepresence oflittlefibrosis and inflammation. Given that larger particles could not enter the circulatory system, the impacts of PS-MPs on intestinal microbial biota homeostasis were further investigated. The results not only showed the characterization of gut microbial communities in Oryzias melastigma, but also indicated that microbial diversity and composition were altered in gut of fish exposed to PS-MPs, in particular 200 μm PS-MPs. The differentially abundant bacterial taxa in PS-MPs-exposed fish mainly belonged to the phylum Verrucomicrobia, Firmicutes and Fusobacteria. And furthermore, increased abundance of Verrucomicrobia and Firmicutes/Bacteroidetes ratio and decreased Fusobacteria were correlated with the increased bodyweight. Intestinal microbiome should play a critical role in regulating host lipid metabolism in fish exposed to lager size of PS-MPs.

Current research trends on micro- and nano-plastics as an emerging threat to global environment: A review

Micro-and nano-plastics (MNPs) (size < 5 mm/<100 nm) epitomize one of the emergent environmental pollutants with its existence all around the globe. Their high persistence nature and release of chemicals/additives used in synthesis of plastics materials may pose cascading impacts on living organism across the globe. Natural connectivity of all the environmental compartments (terrestrial, aquatic, and atmospheric) leads to migration/dispersion of MNPs from one compartment to others. Nevertheless, the information on dispersion of MNPs across the environmental compartments and its possible impacts on living organisms are still missing. This review first acquaints with dispersion mechanisms of MNPs in the environment, its polymeric/oligomeric and chemical constituents and then emphasized its impacts on living organism. Based on the existing knowledge about the MNPs' constituent and its potential impacts on the viability, development, lifecycle, movements, and fertility of living organism via several potential mechanisms, such as irritation, oxidative damage, digestion impairment, tissue deposition, change in gut microbial communities' dynamics, impaired fatty acid metabolism, and molecular damage are emphasized. Finally, at the end, the review provided the challenges associated with remediation of plastics pollutions and desirable strategies, policies required along with substantial gaps in MNPs research were recommended for future studies.

Algal density affects the influences of polyethylene microplastics on the freshwater rotifer Brachionus calyciflorus

Most previous researches focused on the toxicity of polystyrene microplastics (MPs) to marine organisms, but less on polyethylene MPs and freshwater zooplanktons. The present study aims to elucidate the toxicity of polyethylene (PE) MPs (diameter = 10-22 μm) to the typical freshwater rotifer Brachionus calyciflorus. Firstly, fluorescent microscope observation showed that rotifers could ingest PE MPs and accumulate them in their digestive tracts. Life-table experiments revealed that exposure to 0.5 × 10³, 2.5 × 10³, and 1.25 × 10⁴ particles/mL PE MPs significantly reduced net reproductive rate and intrinsic rate of pollution increase of rotifers under algal densities (Scenedesmus obliquus) of 0.1 × 10⁶, and 0.5 × 10⁶ cells/mL, but no significant effects were observed under 2.5 × 10⁶ cells/mL algal density. These results showed that PE MPs suppressed the reproduction of rotifer and this negative effect could be alleviated by increasing food supply. The swimming linear speed of rotifers significantly decreased with increasing MP concentrations. The activities of superoxide dismutase and Na⁺-K⁺-ATPase significantly decreased in treatments with high concentration of PE MPs under 0.1 × 10⁶ cells/mL algal density, but did not change significantly in MP treatments under 0.5 × 10⁶ and 2.5 × 10⁶ cells/mL, compared to the control. Glutathione peroxidase activity significantly increased in treatments with 1.25 × 10⁴ particles/mL and 2.5 × 10³ particles/mL under 0.1 × 10⁶ and 0.5 × 10⁶ cells/mL algal density, respectively, but did not change significantly in all MP treatments under 2.5 × 10⁶ cells/mL. Exposure to PE MPs might lower the gathering capacity of algae, induce oxidative stress, trigger cell membrane damages and disturb energy metabolism in rotifers, which can explain the PE MPs toxicity to rotifer reproduction.

Microplastics decrease the toxicity of triphenyl phosphate (TPhP) in the marine medaka (Oryzias melastigma) larvae

Plastics have been recognized as a serious threat to the environment. Besides their own toxicity, microplastics can interact with other environmental pollutants, acting as carriers and potentially modulating their toxicity. In this study, the toxicity of polystyrene (PS) microplastic fragments (plain PS; carboxylated PS, PS-COOH and aminated PS, PS-NH₂) and triphenyl phosphate (TPhP) (an emerging organophosphate flame retardant) at the environmentally relevant concentrations to the marine medaka (Oryzias melastigma) larvae was investigated. Larvae were exposed to 20 μg/L of microplastic fragments or 20 and 100 μg/L of TPhP or a combination of both for 7 days. The results showed that the three microplastics did not affect the larval locomotor activity. For TPhP, the larval moving duration and distance moved were significantly decreased by the TPhP exposure, with a maximum decrease of 43.5% and 59.4% respectively. Exposure to 100 μg/L TPhP respectively down-regulated the expression levels of sine oculis homeobox homologue 3 (six3) and short wavelength-sensitive type 2 (sws2) by 19.1% and 41.7%, suggesting that TPhP might disturb eye development and photoreception and consequently the low locomotor activity in the larvae. Interestingly, during the binary mixture exposure, the presence of PS, PS-COOH or PS-NH₂ reversed the low locomotor activity induced by 100 μg/L TPhP to the normal level. Relative to the larvae from the 100 μg/L TPhP group, the movement duration and distance moved were increased by approximately 60% and 100%, respectively, in the larvae from the TPhP + PS, TPhP + PS-COOH and TPhP + PS-NH₂ groups. However, the gene expression profiles were distinct among the fish from the TPhP + PS, TPhP + PS-COOH and TPhP + PS-NH₂ groups, implying different mechanisms underlying the reversal of the locomotor activity. The findings in this study challenge the general view that microplastics aggravate the toxicity of the adsorbed pollutants, and help better understand the environmental risk of microplastic pollution.

Microplastics and associated contaminants in the aquatic environment: A review on their ecotoxicological effects, trophic transfer, and potential impacts to human health

The microplastic pollution and related ecological impacts in the aquatic environment have attracted global attention over the past decade. Microplastics can be ingested by aquatic organisms from different trophic levels either directly or indirectly, and transferred along aquatic food chains, causing different impacts on life activities of aquatic organisms. In addition, microplastics can adsorb various environmental chemical contaminants and release toxic plastic additives, thereby serving as a sink and source of these associated chemical contaminants and potentially changing their toxicity, bioavailability, and fate. However, knowledge regarding the potential risks of microplastics and associated chemical contaminants (e.g., hydrophobic organic contaminants, heavy metals, plastic additives) on diverse organisms, especially top predators, remains to be explored. Herein, this review describes the effects of microplastics on typical aquatic organisms from different trophic levels, and systematically summarizes the combined effects of microplastics and associated contaminants on aquatic biota. Furthermore, we highlight the research progress on trophic transfer of microplastics and associated contaminants along aquatic food chain. Finally, potential human health concerns about microplastics via the food chain and dietary exposure are discussed. This work is expected to provide a meaningful perspective for better understanding the potential impacts of microplastics and associated contaminants on aquatic ecology and human health.

Toxicological interactions of microplastics/nanoplastics and environmental contaminants: Current knowledge and future perspectives

The co-occurrence of microplastics/nanoplastics (MPs/NPs) with other environmental contaminants has stimulated a focus shift of its skyrocketed research publications (more than 3000 papers during 2016-2020, Web of Science) from ubiquitous occurrence to interactive toxicity. Here, in this review, we provided the current state of knowledge on toxicological interaction of MPs/NPs with co-contaminants (heavy metals, polycyclic aromatic hydrocarbons, pharmaceuticals, pesticides, nanoparticles, organohalogens, plastic additives, and organotins). We discussed the possible interactions (aggregation, adsorption, accumulation, transformation, desorption) that played a role in influencing the toxicity of the mixture. Besides, the type of interactions such as synergistic, antagonistic, potentiating was expounded to get a deeper mechanistic understanding. Despite the wide occurrence and usage, scant studies were available on polypropylene, polyethylene terephthalate. Our analysis shows a dearth of research on common occurring heavy metals (mercury, lead, chromium), phthalates, personal care products. Considerations for environmental factors such as the presence of dissolved organic matter, pH, salinity, temperature, and effects of different colors and types of polymer are recommended.

Toxicity of polystyrene microplastics on juvenile Oncorhynchus mykiss (rainbow trout) after individual and combined exposure with chlorpyrifos‎

Microplastic (MP) sorption and transfer of chemical contaminants has been widely reported, yet few studies have investigated combined effects of contaminant-loaded MPs on organisms. This study examined effects of pristine or chlorpyrifos (CPF)-loaded polystyrene (PS)‎ fragments on histopathological and histomorphometrical biomarkers in rainbow trout (Onchorhynchus mykiss)‎. In laboratory, O. mykiss were exposed for 96 h to pristine PS-MPs concentrations (30 or 300 µg/L), concentrations of CPF ‎alone (2 or ‎‎6 µg/L), and the same concentrations of CPF in the presence of PS-MPs in aquaria‎. Results showed the highest histopathological alterations in both CPF concentrations and when combined with PS-MPs in fish gills. Alternatively, high histopathological lesions including massive necrosis, infiltration of inflammatory cells, and shed of villi tips were observed in fish gut in high CPF concentrations combined with high PS-MP concentrations of ‎(6 μg/L CPF+300 μg/L PS-‎MPs). Individual CPF and PS-MP concentrations or combined together showed significant changes in histomorphometrical biomarkers in fish gills, gut and skin. Findings highlight that pristine PS-MPs cause toxicity and increase adverse effects of CPF in O. mykiss, especially in gill tissue. We present evidence that pristine short-term exposure to even low concentrations of PS-MPs has a significant impact on biomarker responses in O. mykiss.

Linking effects of microplastics to ecological impacts in marine environments

Recently, efforts to determine the ecological impacts of microplastic pollutants have increased because of plastic's accelerated contamination of the environment. The tiny size, variable surface topography, thermal properties, bioavailability and biological toxicity of microplastics all offer opportunities for these pollutants to negatively impact the environment. Additionally, various inorganic and organic chemicals sorbed on these particles may pose a greater threat to organisms than the microplastics themselves. However, there is still a big knowledge gap in the assessment of various toxicological effects of microplastics in the environment. Ecological risk assessment of microplastics has become more challenging with the current data gaps. Thus, a current literature review and identification of the areas where research on ecology of microplastics can be extended is necessary. We have provided an overview of various aspects of microplastics by which they interact negatively or positively with marine organisms. We hypothesize that biogeochemical interactions are critical to fully understand the ecological impacts, movement, and fate of microplastics in oceans. As microplastics are now ubiquitous in marine environments and impossible to remove, we recommend that it's not too late to converge research on plastic alternatives. In addition, strict actions should be taken promptly to prevent plastics from entering the environment.

Molecular and cellular responses to short exposure to bisphenols A, F, and S and eluates of microplastics in C. elegans

Bisphenol F (BPF) and bisphenol S (BPS) have been developed as an alternative to bisphenol A (BPA), a well-known endocrine disruptor, leading to their detection in the aquatic environment. In this work, we used the animal model Caenorhabditis elegans to improve our understanding of their potential effects on the biota and the environment. Our findings demonstrated that, after 24 h exposure, all the bisphenols examined increased the number of apoptotic corpses and the expression of the detoxifying enzymes SOD-3 and GST-4, without affecting the ROS levels, while BPA and BPS significantly enhanced DNA fragmentation. Furthermore, similarly to BPA, BPF and BPS did not alter the lifespan through the activation of SEK-1 and SKN-1 pathways. Thus, this study raises the attention of the risks associated with exposure to BPA alternatives. We also examined the effects of microplastic (MP) eluates on C. elegans. Aqueous extracts of weathered microplastic samples, both at high and low degradation state and pellets, have been evaluated for their effects on lifespan, DNA fragmentation, germline apoptosis, and oxidative stress response. Overall, our findings showed that eluates of low degraded plastics exert a greater toxic effect on the nematode C. elegans compared with the aqueous sample of high degraded plastic fragments and pellets.

Feeding behavior responses of a juvenile hybrid grouper, Epinephelus fuscoguttatus♀ × E. lanceolatus♂, to microplastics

In recent decades, microplastic (MP) pollution has become a severe problem in aquatic environments. Yet the behavioral and selective responses of fish toward different types of MPs remain unclear. We therefore conducted laboratory-based video observations to investigate the behavioral responses of hybrid grouper juveniles (tiger grouper Epinephelus fuscoguttatus♀ × giant grouper E. lanceolatus♂) to eight different types of MPs. We observed four distinct feeding behaviors: (i) normal ingestion of MPs, which rarely occurred (0%-6%); (ii) pursuit, capture, and tasting of MPs, after which MPs were quickly spat out; (iii) detection and rejection of MPs without attack; and (iv) no significant response to MPs. Our results indicate that juveniles can distinguish MPs as inedible particle and behave differently between MPs with different sizes, colors, and materials, primarily using visual and gustatory senses. Notably, 50%-90% of MP rejection events occurred before capture. Juveniles spent double the time evaluating large nylon particles than they did evaluating large polyvinyl chloride particles before capture, but half the time tasting after capture. Although we observed no sub-lethal or lethal effects of MPs, we conclude that the presence of MPs can still have an impact on groupers in aquaculture. For instance, in the densely stocked conditions of an aquaculture unit, the fish could lose visibility and can inadvertently ingest MPs, thus suffering from their toxic impacts.

Proceed with caution: The need to raise the publication bar for microplastics research

Plastic is a ubiquitous contaminant of the Anthropocene. The highly diverse nature of microplastic pollution means it is not a single contaminant, but a suite of chemicals that include a range of polymers, particle sizes, colors, morphologies, and associated contaminants. Microplastics research has rapidly expanded in recent years and has led to an overwhelming consideration in the peer-reviewed literature. While there have been multiple calls for standardization and harmonization of the research methods used to study microplastics in the environment, the complexities of this emerging field have led to an exploration of many methods and tools. While different research questions require different methods, making standardization often impractical, it remains import to harmonize the outputs of these various methodologies. We argue here that in addition to harmonized methods and quality assurance practices, journals, editors and reviewers must also be more proactive in ensuring that scientific papers have clear, repeatable methods, and contribute to a constructive and factual discourse on plastic pollution. This includes carefully considering the quality of the manuscript submissions and how they fit into the larger field of research. While comparability and reproducibility is critical in all fields, we argue that this is of utmost importance in microplastics research as policy around plastic pollution is being developed in real time alongside this evolving scientific field, necessitating the need for rigorous examination of the science being published.

Combined effects of mulch film-derived microplastics and atrazine on oxidative stress and gene expression in earthworm (Eisenia fetida)

With the wide use of mulch film and pesticides, mulch film-derived microplastics are very likely to produce combined effects with pesticides in agricultural soil. However, little is known about their combined toxicity on terrestrial organisms. This study aimed to investigate the combined toxicity of unused or farmland residual transparent low-density polyethylene mulch film-derived microplastics (MPs and MPs-aged, respectively) (550-1000 μm) and atrazine (ATZ; 0.02 and 2.0 mg/kg) on the earthworm (Eisenia fetida). After single and combined exposure to ATZ and microplastics for 28 d, the results showed an accumulation of reactive oxygen species, a decrease in superoxide dismutase, catalase, and glutathione-S-transferase activities, an increase in the malondialdehyde and 8-hydroxydeoxyguanosine levels, and abnormal expression of annetocin, heat shock protein 70, translationally controlled tumor protein and calreticulin genes. Integrated biological response (IBR) values calculated at the biochemical level indicated that the combined exposure to ATZ and microplastics, particularly to high concentrations of ATZ, induced greater oxidative stress in E. fetida compared with that of exposure to ATZ or microplastics alone. In addition, the IBR values calculated at the gene level did not show regular changes after combined exposure to ATZ and microplastics compared with those of a single exposure. The oxidative stress and abnormal expression of genes in E. fetida induced by MPs-aged were higher than those induced by MPs; a similar trend was observed for oxidative stress induced by MPs/MPs-aged + ATZ2.0, whereas an opposite trend was observed for the abnormal expression of genes in E. fetida induced by MPs/MPs-aged + ATZ0.02/ATZ2.0. Our results suggest that mulch film-derived microplastics have the potential to enhance the toxicity of ATZ within the soil environment.

Micro-contextual identification of archaeological lipid biomarkers using resin-impregnated sediment slabs

Characterizing organic matter preserved in archaeological sediment is crucial to behavioral and paleoenvironmental investigations. This task becomes particularly challenging when considering microstratigraphic complexity. Most of the current analytical methods rely on loose sediment samples lacking spatial and temporal resolution at a microstratigraphic scale, adding uncertainty to the results. Here, we explore the potential of targeted molecular and isotopic biomarker analysis on polyester resin-impregnated sediment slabs from archaeological micromorphology, a technique that provides microstratigraphic control. We performed gas chromatography-mass spectrometry (GC-MS) and gas chromatography-isotope ratio mass spectromety (GC-IRMS) analyses on a set of samples including drill dust from resin-impregnated experimental and archaeological samples, loose samples from the same locations and resin control samples to assess the degree of interference of polyester resin in the GC-MS and Carbon-IRMS signals of different lipid fractions (n-alkanes, aromatics, n-ketones, alcohols, fatty acids and other high polarity lipids). The results show that biomarkers within the n-alkane, aromatic, n-ketone, and alcohol fractions can be identified. Further work is needed to expand the range of identifiable lipid biomarkers. This study represents the first micro-contextual approach to archaeological lipid biomarkers and contributes to the advance of archaeological science by adding a new method to obtain behavioral or paleoenvironmental proxies.

Estimation of the uptake and gut retention of microplastics in juvenile marine fish: Mummichogs (Fundulus heteroclitus) and red seabreams (Pagrus major)

We investigated the impact of microplastics (MPs) on marine fish by estimating the uptake and retention by mummichogs (Fundulus heteroclitus) and red seabreams (Pagrus major) of MPs similar in size (≥0.25 mm) and composition (polyethylene) to MPs detected in fish intestines. Results revealed a correlation between MP concentrations in aquarium water and the content of MPs in the gastrointestinal tracts of exposed fish. More than 95% were excreted from both species within 25 h; this retention time is similar to the processing time of food items. The rate of excretion showed little dependence on MP size, but there was some dependence on fish species and MP shape. These results suggest that MPs similar to those we studied have little direct adverse impact on these two marine fish species.

Interacting Effects of Polystyrene Microplastics and the Antidepressant Amitriptyline on Early Life Stages of Brown Trout (Salmo trutta f. fario)

Whether microplastics themselves or their interactions with chemicals influence the health and development of aquatic organisms has become a matter of scientific discussion. In aquatic environments, several groups of chemicals are abundant in parallel to microplastics. The tricyclic antidepressant amitriptyline is frequently prescribed, and residues of it are regularly found in surface waters. In the present study, the influence of irregularly shaped polystyrene microplastics (<50 µm), amitriptyline, and their mixture on early life-stages of brown trout were investigated. In a first experiment, the impacts of 100, 104, and 105 particles/L were studied from the fertilization of eggs until one month after yolk-sac consumption. In a second experiment, eggs were exposed in eyed ova stages to 105, 106 particles/L, to amitriptyline (pulse-spiked, average 48 ± 33 µg/L) or to two mixtures for two months. Microplastics alone did neither influence the development of fish nor the oxidative stress level or the acetylcholinesterase activity. Solely, a slight effect on the resting behavior of fry exposed to 106 particles/L was observed. Amitriptyline exposure exerted a significant effect on development, caused elevated acetylcholinesterase activity and inhibition of two carboxylesterases. Most obvious was the severely altered swimming and resting behavior. However, effects of amitriptyline were not modulated by microplastics.

The plastic brain: neurotoxicity of micro- and nanoplastics

Given the global abundance and environmental persistence, exposure of humans and (aquatic) animals to micro- and nanoplastics is unavoidable. Current evidence indicates that micro- and nanoplastics can be taken up by aquatic organism as well as by mammals. Upon uptake, micro- and nanoplastics can reach the brain, although there is limited information regarding the number of particles that reaches the brain and the potential neurotoxicity of these small plastic particles.

Earlier studies indicated that metal and metal-oxide nanoparticles, such as gold (Au) and titanium dioxide (TiO₂) nanoparticles, can also reach the brain to exert a range of neurotoxic effects. Given the similarities between these chemically inert metal(oxide) nanoparticles and plastic particles, this review aims to provide an overview of the reported neurotoxic effects of micro- and nanoplastics in different species and in vitro. The combined data, although fragmentary, indicate that exposure to micro- and nanoplastics can induce oxidative stress, potentially resulting in cellular damage and an increased vulnerability to develop neuronal disorders. Additionally, exposure to micro- and nanoplastics can result in inhibition of acetylcholinesterase activity and altered neurotransmitter levels, which both may contribute to the reported behavioral changes.

Currently, a systematic comparison of the neurotoxic effects of different particle types, shapes, sizes at different exposure concentrations and durations is lacking, but urgently needed to further elucidate the neurotoxic hazard and risk of exposure to micro- and nanoplastics.