Effects of pollutants and microplastics ingestion on oxidative stress and monoaminergic activity of seabream brains

Micro-and nano-plastics induce kidney damage and suppression of innate immune function in zebrafish (Danio rerio) larvae

Aquatic environments serve as critical repositories for pollutants and have significantly accumulated micro- and nanoplastics (MNPs) due to the extensive production and application of plastic products. While the disease resistance and immunity of fish are closely linked to the condition of their aquatic habitats, the specific effects of nanoplastics (NPs) and microplastics (MPs) within these environments on fish immune functions are still not fully understood. The present study utilized zebrafish (Danio rerio) embryos and larvae as model organisms to examine the impacts of polystyrene NPs (100 nm) and MPs (5 μm) on fish immune responses. Our findings reveal that NPs and MPs tend to accumulate on the surfaces of embryos and within the intestines of larvae, triggering oxidative stress and significantly increasing susceptibility to Edwardsiella piscicida infection in zebrafish larvae. Transmission electron microscopy examined that both NPs and MPs inflicted damage to the kidney, an essential immune organ, with NPs predominantly inducing endoplasmic reticulum stress and MPs causing lipid accumulation. Transcriptomic analysis further demonstrated that both NPs and MPs significantly suppress the expression of key innate immune pathways, notably the C-type lectin receptor signaling pathway and the cytosolic DNA-sensing pathway. Within these pathways, the immune factor interleukin-1 beta (il1b) was consistently downregulated in both exposure groups. Furthermore, exposure to E. piscicida resulted in restricted upregulation of il1b mRNA and protein levels, likely contributing to diminished disease resistance in zebrafish larvae exposed to MNPs. Our findings suggest that NPs and MPs similarly impair the innate immune function of zebrafish larvae and weaken their disease resistance, highlighting the significant environmental threat posed by these pollutants.

What are the global patterns of microplastic ingestion by fish? A scientometric review

The billions of tons of plastic released into the environment mostly fragment into smaller particles that reach rivers and oceans, posing toxicity risks to aquatic organisms. As fish serve as excellent environmental indicator organisms, this study aims to comprehensively review and quantify published data regarding the abundance of microplastics (MPs) ingested by fish through scientometric analysis. Systematic analysis reveals that global aquatic ecosystems are contaminated by MPs, with the characteristics of these contaminants stemming from inadequate disposal management practices. The abundance of MPs was recorded in several fish species, notably Cyprinus carpio in natural environments and Danio rerio in controlled environments. According to the surveyed studies, laboratory experiments do not accurately represent the conditions found in natural environments. The results suggest that, in natural environments, the predominant colors of MPs are blue, black, and red. Fibers emerged as the most prevalent type, with polyethylene (PE) and polypropylene (PP) being the most frequently identified chemical compositions. On the other hand, laboratory studies showed that the spheres and fragments ingested were predominantly polystyrene (PS) green, followed by the colors blue and red. This discrepancy complicates drawing accurate conclusions regarding the actual effects of plastic particles on aquatic biota. Given the enduring presence of plastic in the environment, it is imperative to consider and implement environmental monitoring for effective, long-term management.

Neurotoxicities induced by micro/nanoplastics: A review focusing on the risks of neurological diseases

Pollution of micro/nano-plastics (MPs/NPs) is ubiquitously prevalent in the environment, leading to an unavoidable exposure of the human body. Despite the protection of the blood-brain barrier, MPs/NPs can be transferred and accumulated in the brain, which subsequently exert negative effects on the brain. Nevertheless, the potential neurodevelopmental and/or neurodegenerative risks of MPs/NPs remain largely unexplored. In this review, we provide a systematic overview of recent studies related to the neurotoxicity of MPs/NPs. It covers the environmental hazards and human exposure pathways, translocation and distribution into the brain, the neurotoxic effects, and the possible mechanisms of environmental MPs/NPs. MPs/NPs are widely found in different environment matrices, including air, water, soil, and human food. Ambient MPs/NPs can enter the human body by ingestion, inhalation and dermal contact, then be transferred into the brain via the blood circulation and nerve pathways. When MPs/NPs are present in the brain, they can initiate a series of molecular or cellular reactions that may harm the blood-brain barrier, cause oxidative stress, trigger inflammatory responses, affect acetylcholinesterase activity, lead to mitochondrial dysfunction, and impair autophagy. This can result in abnormal protein folding, loss of neurons, disruptions in neurotransmitters, and unusual behaviours, ultimately contributing to the initiation and progression of neurodegenerative changes and neurodevelopmental abnormalities. Key challenges and further research directions are also proposed in this review as more studies are needed to focus on the potential neurotoxicity of MPs/NPs under realistic conditions.

Mind over Microplastics: Exploring Microplastic-Induced Gut Disruption and Gut-Brain-Axis Consequences

As environmental plastic waste degrades, it creates an abundance of diverse microplastic particles. Consequently, microplastics contaminate drinking water and many staple food products, meaning the oral ingestion of microplastics is an important exposure route for the human population. Microplastics have long been considered inert, however their ability to promote microbial dysbiosis as well as gut inflammation and dysfunction suggests they are more noxious than first thought. More alarmingly, there is evidence for microplastics permeating from the gut throughout the body, with adverse effects on the immune and nervous systems. Coupled with the now-accepted role of the gut-brain axis in neurodegeneration, these findings support the hypothesis that this ubiquitous environmental pollutant is contributing to the rising incidence of neurodegenerative diseases, like Alzheimer's disease and Parkinson's disease. This comprehensive narrative review explores the consequences of oral microplastic exposure on the gut-brain-axis by considering current evidence for gastrointestinal uptake and disruption, immune activation, translocation throughout the body, and neurological effects. As microplastics are now a permanent feature of the global environment, understanding their effects on the gut, brain, and whole body will facilitate critical further research and inform policy changes aimed at reducing any adverse consequences.

Effects of different concentrations and particle sizes of nanoplastics on gut microbiology, metabolism, and immunity in Chiromantes dehaani

This study investigated the effects of nanoplastics (NPs) of varying particle sizes (75, 500, and 1000 nm) and concentrations (2.5 and 10 mg/L) on the gut health of Chiromantes dehaani. The experimental groups included a control (Cg0), and varying combinations of particle size and concentration. Our results showed that 75 nm NPs were more likely to enhance pathogenic bacterial growth than other sized NPs. Compared with CK, Low NPs concentrations (2.5 mg/L) raised total cholesterol (T-CHO) levels in the gut, while high concentrations significantly decreased both triglyceride (TG) and T-CHO levels (p < 0.05). The enzymatic activities of intestinal lipase and amylase were inhibited by NPs exposure, with greater inhibition at higher NPs concentrations. The 500 nm NPs exhibited a notably higher inhibitory effect than the 75 and 1000 nm NPs (P < 0.05). In terms of apoptosis, NPs exposure led to reduced mRNA expression of Bcl2 and increased expression of Caspase-3, Caspase-8, and Caspase-9, indicating an induction of apoptosis. This effect was more pronounced at higher NPs concentrations, with 75 nm NPs more likely to induce apoptosis in intestinal cells than 500 nm and 1000 nm NPs. Moreover, NPs triggered intestinal inflammatory responses, evidenced by the increased mRNA expression of TNF-β, TNF-α, IL1β, IL6, and IL8, and the decreased expression of IL10. High NPs concentrations were more likely to induce intestinal inflammation, with 500 nm NPs imparting the strongest effect. In summary, the study demonstrated that NPs, and particularly those at higher concentrations, disrupted the gut environment of C. dehaani by altering the microflora, reducing microbial diversity, inhibiting digestion and metabolism, inducing apoptosis, and triggering inflammation. Among the sizes of NPs tested, 500 nm NPs had the most significant adverse impact on digestion, metabolism, and inflammation, while 75 nm NPs most strongly induced apoptosis in C. dehaani's intestinal cells.

Plastic webs, the new food: Dynamics of microplastics in a Mediterranean food web, key species as pollution sources and receptors

In the context of global environmental change, this study presents a novel approach to evaluating microplastic (MP) fluxes and probabilities of pollution within marine food webs. A topological model was built to understand the dynamics of MP pollution in the Mediterranean food webs. The analysis involves two approaches: the first approach includes centrality measures to understand the key role of species in the transmission of trophic effects regarding MPs, and the second approach incorporates MP data by developing the Interaction Pollution Indices (IPIs) at multiple levels to identify species being sources and receptors of MP pollution in the new concept of a plastic-food web. The trophic network consisted of 356 nodes representing not only species, but also aggregations in higher taxa, for a total of 3517 interactions, with 108 species having information on MP frequency of occurrence (FO). The mean probability of dietary MP transference was 0.087 %, and the maximum was 18 %. Species such as the rose shrimp A. antennatus, the catshark S. canicula, the sole S. solea, the sardine S. pilchardus, the Norway lobster N. norvegicus, and the forkbeard P. phycis were found to be significant sources of pollution and played crucial roles in the transmission of effects within the network. By incorporating the IPIs, a deeper understanding of the pollution dynamics at multiple levels was gained, highlighting the value of combining feeding and MP pollution data to develop effective management and conservation strategies. The application of the IPIs holds immense potential for studying bioaccumulation and biomagnification through MP pollutant transferences in marine ecosystems. Its flexibility in incorporating different types of information and units enables its transversal application throughout the field of ecology. This research provides a crucial step towards developing effective tools for MP pollution mitigation strategies and the preservation of marine ecosystems integrity.

Combined effect of microplastic and triphenyltin: Insights from the gut-brain axis

Microplastics (MPs), an emerging group of pollutants, not only have direct toxic effects on aquatic organisms but also cause combined toxicity by absorbing other pollutants. Triphenyltin (TPT), one of the most widely used organotin compounds, has adverse effects on aquatic organisms. However, little is known about the combined toxicity of MPs and TPT to aquatic organisms. To investigate the individual and combined toxicity of MPs and TPT, we selected the common carp (Cyprinus carpio) for a 42-day exposure experiment. Based on the environmental concentrations in a heavily polluted area, the experimental concentrations of MPs and TPT were set at 0.5 mg L^-1 and 1 μg L^-1, respectively. The effects of MPs combined with TPT on the carp gut-brain axis were evaluated by detecting gut physiology and biochemical parameters, gut microbial 16S rRNA, and brain transcriptome sequencing. Our results suggest that a single TPT caused lipid metabolism disorder and a single MP induced immunosuppression in carp. When MPs were combined with TPT, the involvement of TPT amplified the immunotoxic effect induced by MPs. In this study, we also explored the gut-brain axis relationship of carp immunosuppression, providing new insights for assessing the combined toxicity of MPs and TPT. At the same time, our study provides a theoretical basis for evaluating the coexistence risk of MPs and TPT in the aquatic environment.

Microplastics in aquatic environments: A comprehensive review of toxicity, removal, and remediation strategies

The occurrence of microplastics (MPs) in aquatic environments has been a global concern because they are toxic and persistent and may serve as a vector for many legacies and emerging pollutants. MPs are discharged to aquatic environments from different sources, especially from wastewater plants (WWPs), causing severe impacts on aquatic organisms. This study mainly aims to review the Toxicity of MPs along with plastic additives in aquatic organisms at various trophic compartments and available remediation methods/strategies for MPs in aquatic environments. Occurrences of oxidative stress, neurotoxicity, and alterations in enzyme activity, growth, and feeding performance were identical in fish due to MPs toxicity. On the other hand, growth inhibition and ROS formation were observed in most of the microalgae species. In zooplankton, potential impacts were acceleration of premature molting, growth retardation, mortality increase, feeding behaviour, lipid accumulation, and decreased reproduction activity. MPs togather with additive contaminants could also exert some toxicological impacts on polychaete, including neurotoxicity, destabilization of the cytoskeleton, reduced feeding rate, growth, survivability and burrowing ability, weight loss, and high rate of mRNA transcription. Among different chemical and biological treatments for MPs, high removal rates have been reported for coagulation and filtration (>86.5 %), electrocoagulation (>90 %), advanced oxidation process (AOPs) (30 % to 95 %), primary sedimentation/Grit chamber (16.5 % to 58.84 %), adsorption removal technique (>95 %), magnetic filtration (78 % to 93 %), oil film extraction (>95 %), and density separation (95 % to 100 %). However, desirable extraction methods are required for large-scale research in MPs removal from aquatic environments.

Wind erosion induced low-density microplastics migration at landscape scale in a semi-arid region of northern China

Microplastics (MPs) have been extensively investigated in terrestrial environments, while the occurrence and movement of MPs at the landscape scale in semi-arid regions with serious wind erosion are less well studied. Here, we sampled film mulching farmland and downwind nearby grassland surface soils in a semi-arid region of northern China to explore the distribution of MPs at different downwind distances and the potential environmental risk to the local landscapes. The results revealed that the MP abundances presented a decreasing trend with increasing downwind distance (Mann-Kendall test, P < 0.01). The MP size distributions at different distances showed similar sigmoid trends described by logistic models. MP fiber size (500-2000 μm) abundance in the farmland was higher than that of the grassland. By contrast, MP non-fiber size (<1000 μm) abundance of farmlands was less than that of the grassland. The abundances of fibers larger than 500 μm and non-fibers larger than 1000 μm in size decreased exponentially with increasing downwind distance. The size of transported MPs at the landscape scale was larger than that of long-distance dispersal. The migration of MPs from farmlands can pose a potential threat to the downwind landscape, leading the downwind grassland to be a potential MP emission source. This study presents the first insights into the MPs distribution among different downwind distances at the landscape scale. Future research is required to deploy aeolian sediment sampling devices and establish the connection between the field data and the MP emission models.

Microplastic Presence in the Digestive Tract of Pearly Razorfish Xyrichtys novacula Causes Oxidative Stress in Liver Tissue

Plastic pollution in the oceans is a growing problem, with negative effects on exposed species and ecosystems. Xyrichtys novacula L. is a very important fish species both culturally and economically in the Balearic Islands. The aim of the present study was to detect and categorise the presence of microplastics (MPs) in the digestive tract of X. novacula, as well as the existence of oxidative stress in the liver. For this purpose, the fish were categorised into two groups based on the number of MPs observed in the digestive tracts: a group with no or low presence of MPs (0-3 items) and a group with a higher presence of MPs (4-28 items). MPs were found in 89% of the specimens analysed, with a dominance of fibre type and blue colour. Regarding the type of polymer, polycarbonate was the most abundant, followed by polypropylene and polyethylene. For the group with a greater presence of MPs, the activities of the antioxidant enzymes glutathione peroxidase and glutathione reductase, as well as the phase II detoxification enzyme glutathione s-transferase, were higher than the activities observed in fish with little to no presence of MPs. The activities of catalase and superoxide dismutase and the levels of malondialdehyde did not show significant differences between both groups. In conclusion, these results demonstrate the presence of MPs in the digestive tract of X. novacula and the existence of an antioxidant and detoxification response, mainly based on the glutathione-based enzymes.

Biological effects on the migration and transformation of microplastics in the marine environment

Microplastics(MPs) are ubiquitous, difficult to degrade, and potentially threatening to organisms in marine environment, so it is important to clarify the factors that affect their biogeochemical processes. The impact of biological activities on the MPs in marine environment is ubiquitous and complex, and there is currently a lack of systematic summaries. This paper reviews the effects of biological actions on the migration, distribution and degradation of MPs in marine environment from four aspects: biological ingestion and digestion, biological movement, biological colonization and biological adhesion. MPs in seawater and sediments can be closely combined with organisms through three pathways: biological ingestion, biofilm formation or adhesion to organisms, and are passed between species at different trophic levels through the food chain. The generation and degradation of faecal pellets and biofilms can alter the density of "environmental MPs", thereby affecting their vertical migration and deposition in water bodies. The movement of swimming organisms and the disturbance by benthic organisms can promote the migration of MPs in water and vertical migration and resuspension in sediments, thereby changing the distribution of MPs in local sea areas. The grinding effect of the digestive tract and the secretion of chemicals from the biofilm (such as enzymes and acids) can reduce the particle size and increase surface roughness of MPs, or even degrade them completely. Besides, biological adhesion may be an important mechanism affecting the distribution, migration and preservation of MPs. There may be complex interactions and linkages among marine dynamical processes, photochemical degradation and biological processes that collectively affect the biogeochemical processes of MPs, but their relative contributions remain to be more studied.

Environmental microplastic accumulation exacerbates liver ischemia-reperfusion injury in rat: Protective effects of melatonin

Ischemia-reperfusion (IR) injury is an inevitable complication of liver transplantation and partial hepatectomy. Although the hazards of environmental microplastics (EMPs) have been well explored, data underlying their impact on IR-induced hepatotoxicity and how to alleviate these damages remain largely undefined. In this study, the involvement of melatonin (MT) in modulating EMPs toxicity in the liver undergoing ischemia-reperfusion injury was investigated. Male Wistar rats were exposed to MPs for 7 days and then subjected to 1 h of partial warm ischemia (70 %) followed by 24 h of reperfusion. We analyzed some parameters as the oxidative stress, the stability of cytoskeleton as well as inflammation, and autophagy. Our data suggested that EMPs elicited liver injury in ischemic animals. Data revealed several histological alterations caused by EMP and IRI, including cellular disorientation, cell necrosis, and microvacuolar steatosis, as well as inflammatory cell infiltration. EMPs increased blood transaminase (AST and ALT) and oxidative stress levels in the ischemic liver. In addition, RT-qPCR, immunofluorescence, and western blot analyses highlighted an increased expression of α-tubulin, IL-18, NFkB, and LC3. However, the ability of MT to reduce MPs and IRI toxicity was consistent with a significant decrease in the evaluated markers. The combined data not only document that melatonin is an effective agent to protect against hepatic IRI but also reduces cellular dysfunction caused by EMPs.

Beyond the exposure phase: Microplastic depuration and experimental implications

Currently, most studies focus on the effect of microplastics (MPs) in the exposure phase, but pay limited attention to the depuration phase. Depuration is a promising practice to achieve safe aquaculture production, which is also helpful to understand the long-term impact of MPs. Therefore, investigating the post-exposure scenarios of MPs has great practical significance. In order to provide implications for future research, this work attempted to systematize the current findings and knowledge gaps regarding the depuration of MPs. More specifically, three methods, including direct fitting, one-compartment kinetic model and interval observation, for estimating the retention time of MPs to further determine the minimum depuration time were introduced, in which the one-compartment kinetic model could also be used to calculate the depuration rate constant and biological half-life of MPs. Moreover, the post-exposure effect of MPs generally presented three scenarios: incomplete reversal (legacy effect), return to control level (recovery) and stimulatory response (hormesis-like effect). In addition, the possible tissue translocation of MPs, the influence of food abundance and body shape on MPs egestion, and the potential interaction with environmental factors, have aroused great scientific concerns and need further exploration and clarification.

Polystyrene microplastics induced inflammation with activating the TLR2 signal by excessive accumulation of ROS in hepatopancreas of carp (Cyprinus carpio)

Polystyrene microplastics (PS-MPs) affect the immune defense function on carp (Cyprinus carpio). The PS-MPs model of carp was established by feeding with PS-MPs particle size of 8 µm and concentration of 1000 ng/L water. Hepatopancreas function test revealed the activities of AKP, ALT, AST and LDH abnormal increase. PS-MPs induced tissue damage and lead to abnormal hepatopancreas function. The PS-MPs also induced a oxidative stress with the antioxidant enzymes SOD, CAT, GSH-PX, and T-AOC activities decreasing and reactive oxygen species (ROS) excessive accumulation. PS-MPs activated the Toll like receptor-2 (TLR2) signaling pathway. The mRNA and protein expressions of TLR2, Myeloid differentiation primary response 88 (MyD88), tumor necrosis factor receptor-associated factor 6 (TRAF6), NF-κB p65, Tumor necrosis factor (TNF-α), Interleukin-1β (IL-1β), Inducible Nitric Oxide Synthase (iNOS), and cycooxygenase 2(COX2) was revealed increased in both hepatopancreas and hepatocytes with the qPCR and Western blotting analysis mode. ELISA showed the expressions of TNF-α, IL-1β, iNOS, and COX2 inflammatory molecule were increased in both hepatopancreas and hepatocytes. The results showed that PS-MPs caused a serious injure in the hepatopancreas and brought serious effects on the inflammatory response of carp. The present study displayed the harm caused by PS-MPs in freshwater fish, and provided some suggestions and references for toxicological studies of microplastics in freshwater environment.

Breaking the paradigm: Marine sediments hold two-fold microplastics than sea surface waters and are dominated by fibers

We conducted one of the first studies to integrate the quantification and characterization of microplastics (MPs), including fibers, in different habitats (sea surface, seafloor and beach sediments) of a coastal Mediterranean marine protected area, analyzing their ingestion in several marine species. The objectives of the study were to evaluate the distribution of MPs according to shape and polymer, to assess the contribution of fibers to local plastic pollution and to evaluate their ingestion in fish and invertebrates species that inhabit the study area (Pagrus pagrus, Serranus scriba, Spondyliosoma cantharus, Diplodus vulgaris, Oblada melanura, Holothuria forskalii, Holothuria tubularis, Holothuria polis, Arbacia lixula, Paracentrotus lividus, Modiolus barbatus, Mytilus galloprovincialis and Arca noae). A total of 111 environmental samples were analyzed. The mean abundance of MPs (excluding fibers) quantified in beach sediments (13,418.86 ± 28,787.99 MPs/m²) was two orders of magnitude higher than that found in seafloor sediments (76.92 ± 108.84 MPs/m²), which in turn was two orders of magnitude higher than sea surface samples (0.17 ± 0.39 MPs/m²). The fibers were the most abundant shape of MPs identified in all habitats. Variability in MPs ingestion was detected between species, with ingestion rates ranging from 43 % to 100 % for general MPs and ranging from 7 % to 100 % for fibers. The highest ingestion was observed in Holoturians, representing suitable bioindicators for plastic pollution. The composition of the polymer varies weakly depending on habitats and biota, but the result is strongly correlated with the morphology of the plastic. Fibers were mainly composed of cellulose acetate (29 %), styrofoam of polystyrene (18 %), and filaments, films and fragments of polyethylene and polypropylene. The results highlighted the need to expand integrated approaches to effectively study marine plastic pollution and to undertake efficient actions to limit the input of plastics, particularly fibers, into the marine environment.

Is Wild Marine Biota Affected by Microplastics?

The present review provides detailed information on the adverse effects of MPs on wild marine organisms, including tissue damage, fish condition, oxidative stress, immune toxicity, and genotoxicity. A bibliometric analysis was carried out on CiteSpace (version 6.1.R3) (Drexel University, Philadelphia, PA, USA) to verify how many papers studied the effects on wild marine species. The results showed a total of 395 articles, but only 22 really presented data on the effects or impacts on marine biota, and of these, only 12 articles highlighted negative effects. This review shows that the observed effects in wild organisms were less severe and milder than those found in the experimental conditions. The knowledge of negative effects caused by direct ingestion of microplastics in wild animals is still limited; more efforts are necessary to fully understand the role of MPs and the adverse effects on wild marine organisms, the ecosystem, and human health.

The legacy effect of microplastics on aquatic animals in the depuration phase: Kinetic characteristics and recovery potential

The prevalence of microplastics (MPs) in global aquatic environments has received considerable attention. Currently, concerns have been raised regarding reports that the adverse effect of MPs on aquatic animals in the exposure phase may not be (completely) reversed in the depuration phase. In order to provide insights into the legacy effect of MPs from the depuration phase, this study evaluated the kinetic characteristics and recovery potential of aquatic animals after the exposure to MPs. More specifically, a total of 68 depuration kinetic curves were highly fitted to estimate the retention time of MPs. It was shown that the retention time ranged from 1.26 to 3.01 days, corresponding to the egestion of 90 % to 99 % of ingested MPs. The retention time decreased with the increased retention rate. Furthermore, variables potentially affecting the retention time were ranked by the decision tree-based eXtreme Gradient Boosting (XGBoost) algorithm, suggesting that the particle size and tested species were of great importance for explaining the difference in retention time of MPs. Moreover, a biomarker profile was recompiled to determine the toxic changes. Results indicated that the MPs-induced toxicity significantly reduced in the depuration phase, evidenced by the recovery of energy reserves and metabolism, hepatotoxicity, immunotoxicity, hematological parameters, neurotoxicity and oxidative stress. However, the continuous detoxification and remarkable genotoxicity implied that the toxicity was not completely alleviated. In addition, the current knowledge gaps are also highlighted, with recommendations proposed for future research.

Microplastic presence in the pelagic fish, Seriola dumerili, from Balearic Islands (Western Mediterranean), and assessment of oxidative stress and detoxification biomarkers in liver

Microplastics (MPs) are characterized by their high persistence in marine ecosystems, and due to their small size, they can be easily ingested by very diverse organisms. Although the presence of MPs in wild fish is well documented, there is still limited information on their potential to induce adverse effects. Pelagic fish species, because of their wide distribution, are considered good bioindicators for monitoring environmental pollution of marine ecosystems. This study investigated the presence of MPs in the gastrointestinal tract of the predatory pelagic fish (Seriola dumerili) in the Balearic Islands (Mediterranean Sea), and the possible relationship with oxidative stress through the analysis of biomarkers in liver tissue. The results showed the presence of MPs in 98% of total samples examined (n = 52) with an average of 12.2 ± 1.3 MPs/individual. A greater amount of fibre-like particles was isolated compared to fragments. No correlation between the presence of MPs in the gastrointestinal contents and the size of the fishes was noted. Antioxidant enzymes (superoxide dismutase and catalase) and the phase II detoxification enzyme glutathione-S-transferase showed increased activities in fish with higher MPs load. The activity ethoxyresorufin-O-deethylase and the levels of malondialdehyde were similar in both groups. In conclusion, the present results provide an important database on the assessment of the presence of MP debris in S. dumerili gastrointestinal tract and, the potential capability to cause oxidative stress.