No Effect of Polystyrene Microplastics on Foraging Activity and Survival in a Post-larvae Coral-Reef Fish, Acanthurus triostegus

Studies on the transfer effect of aged polyethylene microplastics in soil-plant system

The widespread use of polyethylene (PE) agricultural films has led to a large accumulation of microplastics in soil, and the environmental effects of microplastics on soil-plants have received increasing attention. In the actual soil environment, microplastics undergo significant changes in their physicochemical properties due to aging, accompanied by complex ecological and environmental effects. However, the quantitative understanding of the environmental effects of microplastic aging in soil-plant systems is still unclear. Therefore, this study investigated the effects of aged and unaged PE microplastics on ecological functions and microplastic transfer mechanisms in soil-plant system, and confirmed the transport behavior of micrometer-sized microplastics (26 μm) within maize plants, expanding the upper size limit of existing studies on microplastic transport within plants. The accumulation of microplastics in maize was also quantitatively assessed in combination with the self-established method of Eu marked PE. The mobility ratio of microplastics from soil to roots, roots to stems, and stems to leaves was 1.07%, 0.76%, and 103.28%, respectively. This study provides a scientific understanding for the environmental effects of microplastics in soil-plants systems quantitatively.

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.

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.

Toxicological impacts of micro(nano)plastics in the benthic environment

Micro(nano)plastics (MNPs) have sparked growing public and scientific concerns as emerging pollutants in recent decades, due to their small size and potential for significant ecological and human health impacts. Understanding the toxicological effects of MNPs on aquatic organisms is of great importance; however, most of the available research on aquatic organisms has focused on the pelagic organisms, and studies on benthic organisms are lacking yet. Being bottom-dwelling creatures, benthos perhaps confronts more extreme pressure from MNPs. Therefore, this review summarizes the current literature on the impacts of MNPs on benthic organisms to reveal their toxicity on the survival, growth, development and reproductive systems. MNPs can accumulate in various tissues of benthos and probably cause tissue-specific damage, resulting in genotoxicity and reproductive toxicity to benthic organisms. And, in severe cases, they may also pass on the adverse effects to the next generations. The complexity of co-exposure to MNPs with other aquatic contaminants is also highlighted. Furthermore, we have comprehensively discussed the internal and external factors affecting the toxicity of MNPs in benthic organisms. Additionally, we also presented the current research gaps and potential future challenges, providing overall background information for a thorough understanding of the toxic effects of MNPs in the benthic aquatic ecosystem.

Occurrence of Microplastics in Tap and Bottled Water: Current Knowledge

A narrative review was carried out to describe the current knowledge related to the occurrence of MPs in drinking water. The reviewed studies (n = 21) showed the presence of microplastics (MPs) in tap (TW) and bottled (BW) water, increasing concerns for public health due to the possible toxicity associated with their polymeric composition, additives, and other compounds or microorganism adsorbed on their surface. The MP concentration increase by decreasing particles size and was higher in BW than in TW. Among BW, reusable PET and glass bottles showed a higher MP contamination than other packages. The lower MP abundance in TW than in natural sources indicates a high removal rate of MPs in drinking water treatment plants. This evidence should encourage the consumers to drink TW instead of BW, in order to limit their exposure to MPS and produce less plastic waste. The high variability in the results makes it difficult to compare the findings of different studies and build up a general hypothesis on human health risk. A globally shared protocol is needed to harmonize results also in view of the monitoring plans for the emerging contaminants, including MPs, introduced by the new European regulation.

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.

Microplastics: impacts on corals and other reef organisms

Plastic pollution in a growing problem globally. In addition to the continuous flow of plastic particles to the environment from direct sources, and through the natural wear and tear of items, the plastics that are already there have the potential to breakdown further and therefore provide an immense source of plastic particles. With the continued rise in levels of plastic production, and consequently increasing levels entering our marine environments it is imperative that we understand its impacts. There is evidence microplastic and nanoplastic (MNP) pose a serious threat to all the world's marine ecosystems and biota, across all taxa and trophic levels, having individual- to ecosystem-level impacts, although these impacts are not fully understood. Microplastics (MPs; 0.1–5 mm) have been consistently found associated with the biota, water and sediments of all coral reefs studied, but due to limitations in the current techniques, a knowledge gap exists for the level of nanoplastic (NP; <1 µm). This is of particular concern as it is this size fraction that is thought to pose the greatest risk due to their ability to translocate into different organs and across cell membranes. Furthermore, few studies have examined the interactions of MNP exposure and other anthropogenic stressors such as ocean acidification and rising temperature. To support the decision-making required to protect these ecosystems, an advancement in standardised methods for the assessment of both MP and NPs is essential. This knowledge, and that of predicted levels can then be used to determine potential impacts more accurately.

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.

Treatment-level impacts of microplastic exposure may be confounded by variation in individual-level responses in juvenile fish

Microplastic (MP) pollution is a key global environmental issue and laboratory exposure studies on aquatic biota are proliferating at an exponential rate. However, most research is limited to treatment-level effects, ignoring that there may be substantial within-population variation in responses to anthropogenic stressors. MP exposure experiments often reveal considerable, yet largely overlooked, inter-individual variation in particle uptake within concentration treatments. Here, we investigated to what degree treatment-level responses to MP exposure may be affected by variation in MP ingestion rates in the early life stages of a marine fish, the Gilt-head seabream, Sparus aurata. First, we tested whether MP ingestion variation is repeatable. Second, we assessed to what degree this variation may determine individual-level effects of MP exposure on fitness-related behavioural performance (i.e., escape response). We found that consistent inter-individual variation in MP ingestion was prevalent and led to differential impacts within exposure treatments. Individuals with high MP ingestion rates exhibited markedly inferior escape responses, a result that was partially concealed in treatment-level analyses. Our findings show that the measured response of populations to environmental perturbations could be confounded by variation in individual-level responses and that the explicit integration of MP ingestion variation can reveal cryptic patterns during exposure experiments.

Chronic feeding exposure to virgin and spiked microplastics disrupts essential biological functions in teleost fish

Toxicity of polyethylene (PE) and polyvinyl chloride (PVC) microplastics (MPs), either virgin or spiked with chemicals, was evaluated in two short-lived fish using a freshwater species, zebrafish, and a marine species, marine medaka. Exposures were performed through diet using environmentally relevant concentrations of MPs over 4 months. No modification of classical biomarkers, lipid peroxidation, genotoxicity or F0 behaviour was observed. A significant decrease in growth was reported after at least two months of exposure. This decrease was similar between species, independent from the type of MPs polymer and the presence or not of spiked chemicals, but was much stronger in females. The reproduction was evaluated and it revealed a significant decrease in the reproductive output for both species and in far more serious numbers in medaka. PVC appeared more reprotoxic than PE as were MPs spiked with PFOS and benzophenone-3 compared to MPs spiked with benzo[a]pyrene. Further, PVC-benzophenone-3 produced behavioural disruption in offspring larvae. These results obtained with two species representing different aquatic environments suggest that microplastics exert toxic effects, slightly different according to polymers and the presence or not of sorbed chemicals, which may lead in all cases to serious ecological disruptions.

Micro and Nano Plastics Distribution in Fish as Model Organisms: Histopathology, Blood Response and Bioaccumulation in Different Organs

Micro- and nano-plastic (MP/NP) pollution represents a threat not only to marine organisms and ecosystems, but also a danger for humans. The effects of these small particles resulting from the fragmentation of waste of various types have been well documented in mammals, although the consequences of acute and chronic exposure are not fully known yet. In this review, we summarize the recent results related to effects of MPs/NPs in different species of fish, both saltwater and freshwater, including zebrafish, used as model organisms for the evaluation of human health risk posed by MNPs. The expectation is that discoveries made in the model will provide insight regarding the risks of plastic particle toxicity to human health, with a focus on the effect of long-term exposure at different levels of biological complexity in various tissues and organs, including the brain. The current scientific evidence shows that plastic particle toxicity depends not only on factors such as particle size, concentration, exposure time, shape, and polymer type, but also on co-factors, which make the issue extremely complex. We describe and discuss the possible entry pathways of these particles into the fish body, as well as their uptake mechanisms and bioaccumulation in different organs and the role of blood response (hematochemical and hematological parameters) as biomarkers of micro- and nano-plastic water pollution.

Risks of floating microplastic in the global ocean

Despite the ubiquitous and persistent presence of microplastic (MP) in marine ecosystems, knowledge of its potential harmful ecological effects is low. In this work, we assessed the risk of floating MP (1 μm-5 mm) to marine ecosystems by comparing ambient concentrations in the global ocean with available ecotoxicity data. The integration of twenty-three species-specific effect threshold concentration data in a species sensitivity distribution yielded a median unacceptable level of 1.21 ∗ 10⁵ MP m^-³ (95% CI: 7.99 ∗ 10³-1.49 ∗ 10⁶ MP m^-³). We found that in 2010 for 0.17% of the surface layer (0-5 m) of the global ocean a threatening risk would occur. By 2050 and 2100, this fraction increases to 0.52% and 1.62%, respectively, according to the worst-case predicted future plastic discharge into the ocean. Our results reveal a spatial and multidecadal variability of MP-related risk at the global ocean surface. For example, we have identified the Mediterranean Sea and the Yellow Sea as hotspots of marine microplastic risks already now and even more pronounced in future decades.

Microplastic exposure interacts with habitat degradation to affect behaviour and survival of juvenile fish in the field

Coral reefs are degrading globally due to increased environmental stressors including warming and elevated levels of pollutants. These stressors affect not only habitat-forming organisms, such as corals, but they may also directly affect the organisms that inhabit these ecosystems. Here, we explore how the dual threat of habitat degradation and microplastic exposure may affect the behaviour and survival of coral reef fish in the field. Fish were caught prior to settlement and pulse-fed polystyrene microplastics six times over 4 days, then placed in the field on live or dead-degraded coral patches. Exposure to microplastics or dead coral led fish to be bolder, more active and stray further from shelter compared to control fish. Effect sizes indicated that plastic exposure had a greater effect on behaviour than degraded habitat, and we found no evidence of synergistic effects. This pattern was also displayed in their survival in the field. Our results highlight that attaining low concentrations of microplastic in the environment will be a useful management strategy, since minimizing microplastic intake by fishes may work concurrently with reef restoration strategies to enhance the resilience of coral reef populations.

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.

Microplastic ingestion rates are phenotype-dependent in juvenile anemonefish

The potential influence of microplastic debris on marine organisms is an issue of great ecological and socioeconomic concern. Experiments exposing fishes and invertebrates to constant concentrations of microplastics often yield high variation in particle ingestion rates among individuals. Yet, despite an increasing interest in microplastic ingestion in the wild, the potential intrinsic drivers of inter-individual variation have received little attention so far. Here we assessed individual-level ingestion of Polyethylene microspheres by laboratory-reared juvenile anemonefish, Amphiprion ocellaris, in relation to (a) ambient particle concentrations and (b) repeatable behavioural traits. We show that microplastic ingestion is highly variable at all tested particle concentrations and that this variation can partially be explained by individual activity levels. Moreover, the relationship between ingestion and behavioural variation increased notably when only the most behaviourally consistent individuals (n = 40 out of 60) were considered in the analysis. Our findings indicate that microplastic ingestion rates in juvenile reef fishes may be less dependent on ambient concentrations than expected; instead they are to some degree phenotype-dependent. Care should thus be taken when reporting mean responses to microplastic exposure treatments, because some individuals may not be affected in the same way as others due to differential ingestion behaviour. We also discuss potential ramifications of non-random ingestion variability on population- and community-level responses.

Toxicity of Microplastics and Nanoplastics in Mammalian Systems

Fragmented or otherwise miniaturized plastic materials in the form of micro- or nanoplastics have been of nagging environmental concern. Perturbation of organismal physiology and behavior by micro- and nanoplastics have been widely documented for marine invertebrates. Some of these effects are also manifested by larger marine vertebrates such as fishes. More recently, possible effects of micro- and nanoplastics on mammalian gut microbiota as well as host cellular and metabolic toxicity have been reported in mouse models. Human exposure to micro- and nanoplastics occurs largely through ingestion, as these are found in food or derived from food packaging, but also in a less well-defined manner though inhalation. The pathophysiological consequences of acute and chronic micro- and nanoplastics exposure in the mammalian system, particularly humans, are yet unclear. In this review, we focus on the recent findings related to the potential toxicity and detrimental effects of micro- and nanoplastics as demonstrated in mouse models as well as human cell lines. The prevailing data suggest that micro- and nanoplastics accumulation in mammalian and human tissues would likely have negative, yet unclear long-term consequences. There is a need for cellular and systemic toxicity due to micro- and nanoplastics to be better illuminated, and the underlying mechanisms defined by further work.

Quantification and characterisation of microplastics ingested by selected juvenile fish species associated with mangroves in KwaZulu-Natal, South Africa

Though the number studies on microplastic ingestion by fish is growing, data on fish species characteristic of the South African coastline are scarce. This study quantified and characterised (physically and chemically) microplastics ingested by four species of juvenile fish (viz. Oreochromis mossambicus [Peters, 1852], Terapon jarbua [Forsskål, 1775], Ambassis dussumieri [Cuvier, 1828] and Mugil sp.), within four mangroves along the east coast of South Africa. Microplastics were isolated from whole fish using a proteinase K digestion method, and then quantified and characterised in terms of shape, chemical nature (plastic type), colour and length. Fibres (68%) and fragments (21%) were the dominant shapes found. Of the 174 fish sampled, 52% contained microplastic particles, with 0.79 ± 1.00 particles per fish. The average number of particles per fish did not differ significantly across species within sites and across sites but was higher than in juvenile fish of other species sampled in oceanic habitats. The main plastic types collected using 10 μm filters and identified with Fourier Transform Infrared Spectroscopy (FTIR), were rayon (70.4%), polyester (10.4%), nylon (5.2%) and polyvinylchloride (3.0%). Particle length ranged from 0.1 to 4.8 mm, averaging 0.89 ± 0.77 mm, but irrespective of length, particles were mostly blue in colour. This study provides evidence that juvenile fish inhabiting mangroves are consuming significant quantities of microplastics. Importantly, it should be noted that rayon, though the most abundant plastic type found, is a semi-synthetic fibre made from regenerated cellulose that is commonly reported in studies of this nature. The habitats studied serve as nurseries for numerous fish species; however, more detailed studies are needed to assess whether microplastic ingestion could compromise the health of these fish or whether these effects are dependent on species, feeding habit and/or plastic type.