Effects of virgin microplastics on goldfish (Carassius auratus)

Global daily mask use estimation in the pandemic and its post environmental health risks: Analysis based on a validated dynamic mathematical model

The outbreak of the COVID-19 pandemic led to a sharp increase in disposable surgical mask usage. Discarded masks can release microplastic and cause environmental pollution. Since masks have become a daily necessity for protection against virus infections, it is necessary to review the usage and disposal of masks during the pandemic for future management. In this study, we constructed a dynamic model by introducing related parameters to estimate daily mask usage in 214 countries from January 22, 2020 to July 31, 2022. And we validated the accuracy of our model by establishing a dataset based on published survey data. Our results show that the cumulative mask usage has reached 800 billion worldwide, and the microplastics released from discarded masks due to mismanagement account for 3.27% of global marine microplastic emissions in this period. Furthermore, we illustrated the response relationship between mask usage and the infection rates. We found a marginally significant negative correlation existing between the mean daily per capita mask usage and the rate of cumulative confirmed cases within the range of 25% to 50%. This indicates that if the rate reaches the specified threshold, the preventive effect of masks may become evident.

Exposure Pathways and Toxicity of Microplastics in Terrestrial Insects

The detrimental effects of plastics on aquatic organisms, including those of macroplastics, microplastics, and nanoplastics, have been well established. However, knowledge on the interaction between plastics and terrestrial insects is limited. To develop effective strategies for mitigating the impact of plastic pollution on terrestrial ecosystems, it is necessary to understand the toxicity effects and influencing factors of plastic ingestion by insects. An overview of current knowledge regarding plastic ingestion by terrestrial insects is provided in this Review, and the factors influencing this interaction are identified. The pathways through which insects interact with plastics, which can lead to plastic accumulation and microplastic transfer to higher trophic levels, are also discussed using an overview and a conceptual model. The diverse impacts of plastic exposure on insects are discussed, and the challenges in existing studies, such as a limited focus on certain plastic types, are identified. Further research on standardized methods for sampling and analysis is crucial for reliable research, and long-term monitoring is essential to assess plastic trends and ecological impacts in terrestrial ecosystems. The mechanisms underlying these effects need to be uncovered, and their potential long-term consequences for insect populations and ecosystems require evaluation.

Microplastics in different tissues of historical and live samples of endangered mega-fish (Acipenser sinensis) and their potential relevance to exposure pathways

The Chinese sturgeon (Acipenser sinensis) is an endangered freshwater mega-fish (IUCN-red listed) that survives in the Yangtze River Basin, but the population of which has declined significantly in response to environmental pressures generated by human activities. In order to evaluate the interaction between Chinese sturgeon and microplastics (MPs) for the first time, we examined the gut and gills of historical samples (n = 27), in conjunction with the blood and mucus of live samples (n = 10), to explore the potential pathways involved in MP uptake. We detected MPs in 62.9 % of the field fish, with no significant difference between guts (mean=0.9 items/individual) and gills (mean=0.8 items/individual). The abundance of MPs in fish from 2017 was significantly higher than that from 2015 to 2016 with regards to both gills and gut samples. The size of MPs in gills was significantly smaller than those in guts, yet both contained mostly fibers (90.2 %). No MPs were confirmed in blood, however 62.5 % of mucus samples contained MPs. The MPs in mucus indicated the possibility of MPs entering Chinese sturgeons if their skins were damaged. The body size of Chinese sturgeons affected their MPs uptake by ingestion and inhalation, as less MPs were detected in the gut and gills of smaller individuals. Combining the evidence from historical and live samples, we revealed the presence of MPs in different tissues of Chinese sturgeon and their potential relevance to exposure pathways. Our work expands the understanding of multiple exposure pathways between MPs and long-lived mega-fish, while emphasizing the potential risks of long-term exposure in the field.

Immunotoxicity of microplastics in fish

Plastic waste degrades slowly in aquatic environments, transforming into microplastics (MPs) and nanoplastics (NPs), which are subsequently ingested by fish and other aquatic organisms, causing both physical blockages and chemical toxicity. The fish immune system serves as a crucial defense against viruses and pollutants present in water. It is imperative to comprehend the detrimental effects of MPs on the fish immune system and conduct further research on immunological assessments. In this paper, the immune response and immunotoxicity of MPs and its combination with environmental pollutants on fish were reviewed. MPs not only inflict physical harm on the natural defense barriers like fish gills and vital immune organs such as the liver and intestinal tract but also penetrate cells, disrupting intracellular signaling pathways, altering the levels of immune cytokines and gene expression, perturbing immune homeostasis, and ultimately compromising specific immunity. Initially, fish exposed to MPs recruit a significant number of macrophages and T cells while activating lysosomes. Over time, this exposure leads to apoptosis of immune cells, a decline in lysosomal degradation capacity, lysosomal activity, and complement levels. MPs possess a small specific surface area and can efficiently bind with heavy metals, organic pollutants, and viruses, enhancing immune responses. Hence, there is a need for comprehensive studies on the shape, size, additives released from MPs, along with their immunotoxic effects and mechanisms in conjunction with other pollutants and viruses. These studies aim to solidify existing knowledge and delineate future research directions concerning the immunotoxicity of MPs on fish, which has implications for human health.

Microplastics removal efficiency and risk analysis of wastewater treatment plants in Oman

Microplastics (MPs) have recently been documented as an emerging pollutant that poses a critical threat to environment. Wastewater treatment plants (WWTPs) are commonly regarded as significant contributors to the presence of MPs. This study aimed to assess the MPs load of three wastewater treatment facilities in Oman using various treatments, including MBR, SBR, and CAS. Wastewater samples from influent, effluent, and sludge were collected and analyzed to determine the concentration, morphology, size, color, and polymer type of the MPs. A set of sieves with a mesh size range of 1 mm-45 μm was used to for filtration. Oxidation treatment was applied for all samples using Fenton's reagent, followed by density separation by sodium chloride solution. The Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR- FTIR) method was utilized to test 10% from each sampling point to confirm the polymer types of the MPs. The pollution load index (PLI) and hazard index (HI) have been employed to assess the risk associated with the chemical toxicity and concentration of detected particles. The PROMETHEE method was used to rank the risk of sampling sites based on different criteria that posed potential ecological and human health risks. The results indicate that the average concentrations of 0.99 MP/L, 1.38 MP/L, and 0.93 MP/L were detected in the final treated effluent of WWTP A, WWTP B, and WWTP C, respectively. These concentrations correspond to overall removal efficiencies of 82.5%, 77.4%, and 79.2% for WWTP A, WWTP B, and WWTP C, respectively Most MPs found in tertiary effluent were smaller particles (425 μm) and fiber-shaped. The major types of MPs were polypropylene (PP), low-density polyethylene (LDPE), polyurethane (PU), polyethylene terephthalate (PET), and Polyvinyl chloride (PVC). This study showed that treated effluent and sludge release significant MPs into the environment.

Transcriptomic Responses and Larval-Stage Growth of Protandrous Yellowfin Seabream (Acanthopagrus Latus) to Different Polyethylene Microplastics Exposure

Polyethylene microplastics (PE-MPs) were widespread in the marine environment; thus, their influences on marine hermaphroditic fish cannot be ignored. This study intends to evaluate the adverse biological effects of two different sources of PE, identified by Raman spectroscopy, on protandrous yellowfin seabream (Acanthopagrus latus) larvae. Growth retardation, brain lesions, head/body length ratio increase, and neuroendocrine system disorders were found, and growth and neuroendocrine regulation-related genes such as sstr2, ghrb, irs1, UGT2B15, UGT2C1, drd4a, esr2b, hsd3b7, and hsd17b2 were identified. PE microbeads (100 μm) showed more severe tissue damage on fish, while environmental PE fibers (500-2500 μm) showed more imperceptible adverse effects. There were 218 DEGs up-regulated and 147 DEGs down-regulated in the environmental PE group, while 1284 (up) and 1267 (down) DEGs were identified in the virgin PE group. PE-MP stress influenced physiological processes like growth and neuroendocrine regulation and cholesterol-steroid metabolism, and caused tissue damage in the fish larvae. The study highlights the effects of environmental PE exposure on hermaphroditic protandrous fish.

How do fish consume microplastics? An experimental study on accumulation pattern using Nile tilapia (Oreochromis niloticus)

The aim of this study was to investigate microplastic (MP) exposure by Nile tilapia (Oreochromis niloticus) in laboratory conditions. A total of 150 tilapia fishes were equally distributed randomly in 15 different glass tanks with five experimental conditions. Observed results depicted that the presence of MPs in different organs was mainly accumulated from the fish feed rather than externally added MPs in the culture tanks. It was also revealed that the gastrointestinal tract (GIT) was found to be the most susceptible to MPs accumulation followed by gills and muscles in order. However, muscle contained the least size of MPs followed by GITs and gills. A statistical test showed significant correlations among the average length and weight of fish with MP exposure. A filamentous shape was found to be dominant in both GITs and gills while fragment shape was dominant in muscles. FTIR results revealed a total of 12 different polymers in the fish of which two polymers (polyvinyl alcohol and ethylene vinyl acetate) were not detected in the feed-only tanks. Polypropylene (PP) and polyethylene terephthalate (PET) were found to be dominant polymers in all the experimental GIT, gills, and muscle organs. FESEM results indicated the presence of different textures including cracks, edges, flakes, scratches, grooves, and adhering particles. EDX results exhibited the presence of Na, Si, K, Ni, Cu, Zn, As, and Cd in the analyzed samples that may pose additional health risks. Thus, this study could act as baseline data for laboratory-based studies of aquaculture species in future research.

Deleterious effects of polypropylene released from paper cups on blood profile and liver tissue of Clarias gariepinus: bioremediation using Spirulina

Despite numerous studies on microplastics, the biological impacts of polypropylene microplastics (PP-MPs) and its toxicity on freshwater fish have yet to be fully revealed. The purpose of this research was to look at the potentially harmful effects of PP-MPs in freshwater African catfish Clarias gariepinus and bioremediation using Spirulina. After acclimatization to laboratory conditions, 108 fish (125 ± 3 gm and 27 ± 2 cm) were assigned into triplicate six experimental groups (12 fish/group), a control group, Spirulina group (SP), PP-MP-treated groups (0.14 and 0.28 mg/l PP-MPs), and PP-MP + Spirulina-treated groups (0.14 mg/l PP-MPs + 200 mg/L SP and 0.28 mg/l PP-MPs +200 mg/L SP) for 15-day exposure and 45-day recovery after that. The hematological parameters exhibiting significance (RBCs, Hct, Hb, and MCV) or non-significance (MCH and MCHC) either decreased with the increase in PP-MP doses from 0.0 in the control to 0.28 mg/L red blood cells (RBCs), hematocrit (Hct), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), hemoglobin (Hb) and platelets or increased with such an increase in doses (mean corpuscular volume (MCV)). The liver enzyme activity, aspartate aminotransferase (AST), alkaline phosphatase (ALP), and alanine aminotransferase (ALT) exhibited non-significant (p ≥ 0.05) or significant (p < 0.05) increases in (0.14 and 0.28 mg/L) PP-MP-exposed groups, respectively, except ALP. Furthermore, there was a significant (p < 0.05) or non-significant (p ≥ 0.05) increase in 0.14 and 0.28 mg/l PP-MP +200 mg/L-exposure groups, respectively, compared to the control group and the same exposure group without Spirulina. In comparison to the control group, PP-MPs (0.14 and 0.28 mg/L) induced a significant (p < 0.05) increase in the percentage of poikilocytosis and nuclear abnormalities of RBCs. The liver tissue from fish exposed to PP-MPs exhibited varying degrees of pathological changes. These results indicated that these pathological changes increased with PP-MP concentration, suggesting that the effect of PP-MPs was dose-dependent. After 45 days of recovery under normal conditions, it was obvious that there was a significant improvement in the percentage of poikilocytosis and nuclear abnormalities of RBCs, as well as a non-significant improvement in hemato-biochemical parameters and liver tissue.

Size dependent ingestion and effects of microplastics on survivability, hematology and intestinal histopathology of juvenile striped catfish (Pangasianodon hypophthalmus)

Microplastic pollution is drastically increasing in aquatic ecosystems and it is assumed that different sizes of microplastics have diverse impacts on the physiology of aquatic organisms. Therefore, this study was intended to examine the ingestion and size specific effects of polyamide microplastic (PA-MP) on different physiological aspects such as growth, feed utilization, survivability, blood parameters and intestinal histopathology of juvenile striped catfish (Pangasianodon hypophthalmus). In a 28-day exposure, the fish were fed with different sized PA-MP with a concentration of 500 mg per kg of feed in order to simulate highly microplastic contaminated environment. Three different treatments were set for this experiment i.e. T1, 25-50 μm (smaller microplastic); T2, 300 μm-2 mm (larger microplastic); T3, (mixed) including a control (C); each had three replicates. The highest ingestion was recorded in the gastrointestinal tract (GIT) of fish exposed to smaller PA-MP treatments (T1 followed by T3). The results also showed compromised weight gain (WG; g), specific growth rate (SGR; %/day) and feed conversion ratio (FCR) with the exposure of PA-MP. Besides, survivability significantly reduced among treatments with the ingestion of smaller sized microplastic and found lowest in T1 (65.0 ± 5.0). In addition, the presence of PA-MP in feed negatively affected the concentration of hemoglobin and blood glucose. Similarly, smaller PA-MP caused most erythrocytic cellular and nuclear abnormalities; found highest in T1 that significantly different from other treatments (p < 0.05). Various histopathological deformities were observed in fish fed with PA-MP incorporated feed. The principal component analysis (PCA) showed that the toxicity and stress imparted by smaller PA-MP affected the survivability and blood parameters where larger PA-MP caused mild to severe abnormalities. Based on eigenvector values, the major abnormalities in intestine included occurrence of epithelium columnar degeneration (ECD: 0.402; PC1), hyperplasia of internal mucosa (HISM: 0.411; PC1), beheading of villi (BV: 0.323; PC1), atrophy of mucosa (AM: 0.322; PC1), tiny vacuoles in apical villi (TV: 0.438. PC2), crypt degeneration (CD: 0.375: PC2) and atrophy of goblet cell (AGC: 0.375; PC2). Therefore, it has been speculated that the size based PA-MP ingestion in the GIT interfered with the digestion and absorption as well as caused deformities that reflected negatively in survivability and hemato-biochemical parameters of juvenile striped catfish.

Incidence of microplastics in Indian anchovy Stolephorus indicus from Tuticorin, Southeast coast of India

In the present study, the occurrence of microplastics (MPs) in the gut, gill, and muscle of edible fish Stolephorus indicus sampled from Tuticorin coastal regions of Tamilnadu, India was investigated. We recorded a total of 689 MPs which includes 510 and 179 MPs from males and females respectively. The total abundance of MPs was significantly (P < 0.05) higher in the gut followed by gills and muscle. The sex-wise distribution of average MPs showed high in the females' gut and compared to that in males. Further, the length wise distribution of MPs was higher in the muscle in both male and female fish, followed by other organs. The predominance of MPs in tissues were transparent and blue colour with fibers and fragments in both males and females. Besides, polyethylene terephthalate and nylon were evidenced by the Fourier-transform infrared spectroscopy spectrum in all organs of fishes.

Polystyrene nanoplastic and engine oil synergistically intensify toxicity in Nile tilapia, Oreochromis niloticus : Polystyrene nanoplastic and engine oil toxicity in Nile tilapia

Polystyrene nanoplastic (PS-NPs) and Engine oil (EO) pose multiple ecotoxic effects with increasing threat to fish ecosystems. The current study investigated the toxicity of 15 days exposure to PS-NPs and / or EO to explore their combined synergistic effects on Nile tilapia, Oreochromis niloticus (O. niloticus). Hematobiochemical parameters, proinflammatory cytokines, and oxidative stress biomarkers as well as histological alterations were evaluated. The experimental design contained 120 acclimated Nile tilapia distributed into four groups, control, PS-NPs (5 mg/L), EO (1%) and their combination (PS-NPs + EO). After 15-days of exposure, blood and tissue samples were collected from all fish experimental groups. Results indicated that Nile tilapia exposed to PS-NPs and / or EO revealed a significant decrease in almost all the measured hematological parameters in comparison to the control, whereas WBCs and lymphocyte counts were significantly increased in the combined group only. Results clarified that the combined PS-NPs + EO group showed the maximum decrease in RBCs, Hb, MCH and MCHC, and showed the maximum significant rise in interleukin-1β (IL-1β), and interleukin-6 (IL-6) in comparison to all other exposed groups. Meanwhile, total antioxidant capacity (TAC) showed a significant (p < 0.05) decline only in the combination group, whereas reduced glutathione (GSH) showed a significant decline in all exposed groups in comparison to the control. Both malondialdehyde (MDA) and aspartate aminotransferase (AST) showed a significant elevation only in the combination group. Uric acid showed the maximum elevation in the combination group than all other groups, whereas creatinine showed significant elevation in the EO and combination group when compared to the control. Furthermore, the present experiment proved that exposure to these toxicants either individually or in combination is accompanied by pronounced histomorpholgical damage characterized by severe necrosis and hemorrhage of the vital organs of Nile tilapia, additionally extensively inflammatory conditions with leucocytes infiltration. We concluded that combination exposure to both PS-NPs and EO caused severe anemia, extreme inflammatory response, oxidative stress, and lipid peroxidation effects, thus they can synergize with each other to intensify toxicity in fish.

Occurrence of microplastics in fish gastrointestinal tracts belongs to different feeding habits from the Bangladesh coast of the Bay of Bengal

The Bay of Bengal (BoB) is home to a range of commercially important species with different food habits and feeding features. Microplastic (MP) contamination in the fish of BoB, like in many other marine environments, is a significant environmental concern. The study aimed to investigate the presence of microplastics (MPs) in the gastrointestinal tracts (GITs) of selected commercial marine fishes from the Bangladesh coast of the BoB. Six fish species (Escualosa thoracata, Tenualosa ilisha, Johnius belangerii, Trichiurus lepturus, Planiliza parsia, and Mystus gulio) were investigated (n = 120) following hydrogen peroxide digestion, and floatation (saline solution) protocols. After analyses, a total number of 696 MPs (dimension 0.3 to 5 mm) were identified. Moreover, the highest occurrence of MPs in fish GITs was found in planktivorous fish (average of 7.7 items/individual), followed by omnivorous (average of 5.2 items/individual), and carnivorous fish (average of 4.6 items/individual) (p < 0.001). However, planktivorous E. thoracata showed the highest number of MPs per g of GIT (average of 30.99 items/g GIT), whereas T. ilisha showed the lowest count (average of 0.77 items/g GIT). Different types of MPs (fibers (19 to 76%), fragments (6 to 61%), films (8 to 35%), microbeads (0 to 5%), and foams (0 to 2%)) were also observed. In terms of the color of MPs, the transparent, black, green, and blue types were the most common. Polymers were found as polyethylene (35 to 43%), polyethylene terephthalate (28 to 35%), polyamide (20 to 31%), and polystyrene (0 to 7%). The study provides a significant incidence of MPs in fish from the Bangladesh part of the BoB, which is very concerning. Therefore, long-term research is indispensable to ascertain the variables affecting the presence of MPs in fish, their origins, and their potential effects on the BoB fisheries. Stringent policies on plastic use and disposal should be strongly urged in this coastal region.

Assessment of microplastic contamination in shrimps from the Bay of Bengal and associated human health risk

Microplastics (MPs) were analyzed in seven shrimp species Tiger shrimp (Penaeus monodon), Red tiger shrimp (Caridina cantonensis), Indian shrimp (Penaeus indicus), Red shrimp (Metapenaeus dobsoni), White shrimp (Penaeus merguiensis), Brown shrimp (Metapenaeus monoceros), and Roshna shrimp (Palaemon styliferus) collected from the Bay of Bengal. The abundance and characteristics of MPs were assessed in the gastrointestinal tract (GIT), which certainly translocated to the muscle of shrimp species. The highest MP abundance was found in C. cantonensis with 7.2 items/individual (25.3 items/g in the GIT and 6.3 items/g in muscle). The prominent types of MPs in shrimp samples were fibers (30 %) and fragments (29 %). The ingestion rate of MPs of black and transparent color was comparatively higher, with 64 % of the ingested MPs were < 100 μm. The primary polymer types detected based on Fourier Transform Infrared (FTIR) analysis were Low-Density Polyethylene (LDPE), High-Density Polyethylene (HDPE), Polymethyl Methacrylate (PMMA), Polyvinyl Chloride (PVC), Polypropylene (PP), and Ethylene Vinyl Acetate (EVA). Results from Scanning Electron Microscopy (SEM) showed rough surface textures and adhered particles on the MPs isolated from shrimps. The margin of exposure for females was 71.42, and for males, it was 80.64, indicating that women in Bangladesh are more likely to be exposed to MPs and face a higher risk than men. Sensitivity analysis revealed that MPs particle size was the most sensitive parameter. These findings provide a comprehensive understanding of MP ingestion, human exposure, and contamination in shrimps of Bangladesh, which can help future monitoring efforts.

Assessment of dietary polyvinylchloride, polypropylene and polyethylene terephthalate exposure in Nile tilapia, Oreochromis niloticus: Bioaccumulation, and effects on behaviour, growth, hematology and histology

Microplastics (MPs) have been recognized as emerging aquatic pollutants receiving major concern due to their detrimental effects on aquatic life. Nile Tilapia, Oreochromis niloticus is a model species considered in toxicological studies to address the effects of pollutants in freshwater animals. However, comprehensive knowledge comparing the impacts on fish across various MPs polymers is scarce. Therefore, the overarching aim of the current study was to examine the bioconcentration of MPs polymers: polyvinylchloride (PVC), polypropylene (PP), and polyethylene terephthalate (PET), and their toxic effects on growth, and behavioral responses, hematology, and histology of gills, liver, and intestine in O. niloticus. Fishes were subjected to a 21-day dietary exposure to MPs by assigning them into six treatment groups: T1 (4% of PVC), T2 (4% of PP), T3 (4% of PET), T4 (8% of PVC), T5 (8% of PP), T6 (8% of PET), and control (0% of MPs), to assess the effects on fish across the polymers and dosage. Results showed several abnormalities in anatomical and behavioral parameters, lower growth, and high mortality in MPs-exposed fish, indicating a dose-dependent relationship. The elevated dosage of polymers raised the bioavailability of PVC, PP, and PET in gills and gut tissues. Noteworthy erythrocyte degeneration referred to cytotoxicity and stress imposed by MPs, whereas the alterations in hematological parameters were possibly due to blood cell damage, also indicating mechanisms of defense against MPs toxicity. Histopathological changes in the gills, liver, and intestine confirmed the degree of toxicity and associated dysfunctions in fish. A higher sensitivity of O. niloticus to PET-MPs compared to other polymers is likely due to its chemical properties and species-specific morphological and physiological characteristics. Overall, the present study reveals valuable insights into the emerging threat of MPs toxicity in freshwater species, which could be supportive of future toxicological research.

Microplastics may induce food dilution and endocrine disrupting effects in fathead minnows (Pimephales promelas), and decrease offspring quality

Microplastics are a complex environmental contaminant that have been reported to cause a variety of impacts, although the mechanism of these impacts remains unclear. Many studies have investigated either sub-organismal or apical endpoints, while very few have attempted to integrate and link endpoints seen at multiple levels of organization. Here, we exposed fathead minnows to microplastics for their entire lifecycle, from the egg stage through to reproduction, and raised a subset of the offspring in clean water. We show that both preconsumer and environmentally sourced microplastics impact adult growth, lipid storage, and external colouration, suggesting a potential food dilution effect. Environmentally sourced microplastics, but not preconsumer microplastics, had further endocrine disrupting impacts on the parental generation and their offspring in the low concentration treatments such that egg production began later, eggs were less viable, and the offspring had higher rates of malformation. Low dose effects are a typical dose-response for endocrine disrupting contaminants. These results suggest that microplastic exposure, at concentrations relevant to what is being found in the environment, has potential implications for forage fish populations. Our findings also highlight the importance of using an integrative approach to understanding the mechanisms behind how and why microplastics impact organisms.

Environmental and ecological risk of microplastics in the surface waters and gastrointestinal tract of skipjack tuna (Katsuwonus pelamis) around the Lakshadweep Islands, India

The presence of microplastics (MPs) in marine ecosystems is widespread and extensive. They have even reached the deepest parts of the ocean and polar regions. The number of articles on plastic pollution has increased in recent years, but few have investigated the MPs from oceanic islands which are biodiversity hotspots. We investigated the possible microplastic contamination their source and characteristics in surface waters off Kavaratti Island and in the gastrointestinal tract (GT) of skipjack tuna, Katsuwonus pelamis collected from Kavaratti Island of the Lakshadweep archipelago. A total of 424 MP particles were isolated from the surface water samples collected from off Kavaratti Island with an average abundance of 5 ± 1nos./L. A total of 117 MPs were recovered from the GT of skipjack tuna from 30 individual fishes. This points to a potential threat of MP contamination in seafood around the world since this species has a high value in local and international markets. Fiber and blue color were the most common microplastic morphotypes and colors encountered, respectively, both from surface water and GT of fish. Smaller MPs (0.01-1 mm) made up a greater portion of the recovered materials, and most of them were secondary MPs. Polyethylene and polypropylene were the most abundant polymers found in this study. The Pollution Load Index (1.3 ± 0.21) of the surface water and skipjack tuna (1 ± 0.7) indicates a minor ecological risk for the coral islands, while the Polymer Hazard Index highlights the ecological risk of polymers, even at low MP concentrations. This pioneer study sheds preliminary light on the abundance, properties, and environmental risks of MPs to this highly biodiverse ecosystem.

The physiological response of the clam Ruditapes philippinarum and scallop Chlamys farreri to varied concentrations of microplastics exposure

Microplastics (MPs) pollution's impact on the marine ecosystem is widely recognized. This study compared the effects of polyethylene (PE) and polyethylene terephthalate (PET) on two bivalve species, Ruditapes philippinarum (clam) and Chlamys farreri (scallop), at two particle concentrations (10 and 1000 μg/L). MPs were found in the digestive glands and gills of both species. Although clearance rates showed no significant changes, exposure to different MPs caused oxidative stress, energy disruption, and lipid metabolism disorders in both clam and scallop. Histopathological damage was observed in gills and digestive glands. IBR values indicated increasing toxicity with concentration, with PET being more toxic than PE. WOE model suggested increasing hazard with concentration, highlighting higher PET toxicity on clam digestive glands. In contrast, PE hazard increased in gills, showing different species responses. R. philippinarum exhibited higher sensitivity to MPs than C. farreri, providing insights for assessing ecological risk under realistic conditions and stress conditions.

Insight into microplastics in the aquatic ecosystem: Properties, sources, threats and mitigation strategies

Globally recognized as emergent contaminants, microplastics (MPs) are prevalent in aquaculture habitats and subject to intense management. Aquaculture systems are at risk of microplastic contamination due to various channels, which worsens the worldwide microplastic pollution problem. Organic contaminants in the environment can be absorbed by and interact with microplastic, increasing their toxicity and making treatment more challenging. There are two primary sources of microplastics: (1) the direct release of primary microplastics and (2) the fragmentation of plastic materials resulting in secondary microplastics. Freshwater, atmospheric and marine environments are also responsible for the successful migration of microplastics. Until now, microplastic pollution and its effects on aquaculture habitats remain insufficient. This article aims to provide a comprehensive review of the impact of microplastics on aquatic ecosystems. It highlights the sources and distribution of microplastics, their physical and chemical properties, and the potential ecological consequences they pose to marine and freshwater environments. The paper also examines the current scientific knowledge on the mechanisms by which microplastics affect aquatic organisms and ecosystems. By synthesizing existing research, this review underscores the urgent need for effective mitigation strategies and further investigation to safeguard the health and sustainability of aquatic ecosystems.

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).

Physiological and histopathological effects of polystyrene nanoparticles on the filter-feeding fish Hypophthalmichthys molitrix

Excessive use of plastics in daily life is causing plastic pollution in aquatic environment and threatening the aquatic life. Therefore, research on the plastic pollution in aquatic environment is crucial to understand its impact and develop effective solution for safeguarding aquatic life and ecosystem. The current study investigated the effects of water borne polystyrene nanoparticles (PS-NPs) on hemato-immunological indices, serum metabolic enzymes, gills, and liver antioxidant parameters, plasma cortisol level and histopathological changes in liver and gill tissues of the widely distributed fish Hypophthalmichthys molitrix. The fingerlings of H. molitrix were exposed to different concentrations (T1-0.5, T2-1.0, and T3-2.0 mg/L) of PS-NPs respectively for 15 days consecutively. Our results indicated the dose dependent negative effects of PS-NPs on the physiology and histopathology of H. molitrix. Immuno-hematological indices showed significant increase in WBCs count, phagocytic activity, and lysozyme activity, while decreased RBC count, Hct%, Hb level, total proteins, IgM, and respiratory burst activity were observed. The levels of antioxidant enzymes like SOD, CAT and POD showed the decreasing trends while metabolic enzymes (AST, ALT, ALP and LDH), LPO, ROS activities and relative expressions of SOD1, CAT, HIF1-α and HSP-70 genes increased with increased concentrations of PS-NPs. Moreover, blood glucose and cortisol levels also showed significant increasing trends with dose dependent manner. Histopathological examination indicated moderate to severe changes in the gills and liver tissues of the group treated with 2.0 mg/L of PS-NPs. Overall, the results showed the deleterious effects of PS-NPs on physiology, immunity, metabolism, and gene expressions of H. molitrix. It is concluded that particulate plastic pollution has deleterious effects on filter feeding fish, which might affect human health through food chain and particulate chemical toxicity.

Evidence of microplastics accumulation in the gills and gastrointestinal tract of fishes from an estuarine system in Ghana

The contamination of aquatic environments by microplastics (MPs) and their subsequent ingestion by fish continues to be a universal ecological challenge. Although numerous studies have been conducted on the accumulation of MPs by fishes globally, not much work has been done within the major estuaries along the Atlantic Coast. This study explored and characterized microplastics in the gills and gastrointestinal tract in 98 specimens of 10 fish taxa (Sarotherodon melanotheron, Pseudotolithus senegalensis, Gobionellus occidentalis, Ethmalosa fimbriata, Chrysichthys nigrodigitalus, Elops lacerta, Mugil bananesis, Cynoglossus senegalensis, Apsilus fuscus and Galeoides decadactylus) from the Pra Estuary, Ghana. The gastrointestinal contents of the fish were extracted, analysed and characterized using a stereomicroscope fitted with an Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR). A total of 529 MP particles were found in the fishes. C. nigrodigitalus recorded the highest MP levels in the gills with an average of 4.83 ± 2.08 items/individual whiles S. melanotheron recorded the highest in the gastrointestinal tract at 9.83 ± 4.63 items/individual. Within the fish, transparent fibrous MPs of size <0.5 mm were the dominate types found. A vertical prevalence of MPs was observed across the feeding and habitat preference of the species suggesting a possible linkage with the ecological niche of fishes. Our findings further demonstrate the need for advance studies on the impacts and level of threat microplastic accumulation pose to the sampled fishes and potential consumers.

Evaluation of microplastic pollution and risk assessment in a tropical monsoonal estuary, with special emphasis on contamination in jellyfish

Estuaries, which serve as vital links between land and coastal ecosystems, play a significant part in facilitating the transfer of plastic waste from the land to the ocean. In this research, we examined the prevalence, characteristics, and ecological risks of microplastics (MPs) in the extensively urbanized Cochin Estuarine System (CES), India. Additionally, it represents one of the initial evidence-based examinations of MPs ingestion by jellyfish in Indian waters, focusing on Acromitus flagellatus, Blackfordia virginica, and Pleurobrachia pileus species. The abundance of MPs found in the surface water of the Cochin Estuarine System (CES) varied between 14.44 ± 9 to 30 ± 15.94 MP/m3, with an average of 21.6 ± 11 MP/m3. In both surface waters and jellyfish from the Cochin Estuarine System (CES), fibers were the most prevalent type of MPs, with polyethylene (PE), polypropylene (PP), and polyamide (PA) being the most common polymer varieties. To evaluate the current levels of MPs and their effect on the CES, the Pollution Load Index (PLI), Potential Ecological Risk Index (PERI), and Polymeric Risk Index (H) were utilized. The high PLIestuary values (20.33), high Hestuary values (234.02), and extreme PERIestuary value (1646.06) indicate that the CES is facing an extreme ecological risk. Among the 280 jellyfish individuals examined, 118 (42.14%) were recognized to contain MPs with an average of 1.54 ± 2.68 MPs/individual. Pearson bivariate analysis revealed a significant correlation between the jellyfish bell size and number of plastics per individual. Comparison between jellyfish species revealed, the majority (66%) of the MPs identified in jellyfish were from A. flagellatus and 44 among the 50 jellyfish examined (88%) had MPs. These findings suggest that A. flagellatus may be a potential sink for MPs and may be utilized to be a bioindicator for monitoring MPs contamination in estuarine systems, aiding in future plastic pollution mitigation efforts.

Independent and synergistic effects of microplastics and endocrine-disrupting chemicals on the reproductive social behavior of fathead minnows (Pimephales promelas)

Microplastics (MPs) have become an environmental concern in recent years, with most research focused on the physiological effects of exposure. Comparatively little consideration has been given to the potential behavioral impacts of exposure, which may also have fitness consequences for individuals. Moreover, MPs can serve as vectors for endocrine-disrupting chemicals and other locally co-occurring contaminants known to impair behavioral responses. This project aimed to determine whether MPs alone or in association with a common environmental EDC (17-alpha ethinyl estradiol; EE2) alter reproductive behavior and decision-making in fish. Male and female fathead minnows (Pimephales promelas) were exposed to MPs associated with either a low (10 ng/L; MPEE2 10) or high (50 ng/L, MPEE2 50) concentration of EE2, or MPs without EE2 (MPvirgin) for 30 days via a dietary feeding protocol. Behavioral trials were conducted on Day 31 to determine the effects of exposure on male-female social interactions. The expression of male sexually selected traits, including courtship, was unaffected by exposure. However, non-exposed females in all treatment groups trended toward discrimination against exposed males, which reached statistical significance for the MPEE2 50 group. Female fish exposed to MPs, alone or in association with EE2, were equally likely to approach and associate with non-exposed and exposed males. The results from this study suggest that MPs may alter social behavior in fishes and that the behavioral impacts of exposure may be more strongly pronounced in females than males. Such individual-level changes in fitness have the potential to impact population size, with downstream effects on the broader aquatic community.

Interactions between microplastics and insects in terrestrial ecosystems-A systematic review and meta-analysis

The presence of microplastics (MPs) in terrestrial ecosystems has been confirmed worldwide. Due to their widespread distribution and diversity in habitats, insects will readily interact with MPs via various pathways. Although the topic of MP-insect interactions is still in the early stages of research, it is becoming increasingly important. We used a META approach with phylogenetic control and subgroup examination to summarize the evidence from both field and laboratory experiments in quantitative form. The field evidence suggests that insects can take and transfer MPs along food chains via ingestion and adherence. Also, they are active in the bio-fragmentation of MPs and the generation of secondary pollutants. The exposure to MPs impaired key biological traits of insects, mainly their behavior and health, such as reducing climbing ability and increasing oxidative stress. In terms of exposure conditions, the small-sized MPs can induce more severe effects on the insects, while the insect response to MPs was not significantly reliant on exposure times or MP concentrations based on the current evidence available. We propose that insects not only play roles in the redistribution of MPs spatially and in food chains via bio-fragmentation but are also threatened by MPs. Our research deepens our understanding of the environmental risks posed by MPs in insect ecosystems.

Research progress on occurrence characteristics and source analysis of microfibers in the marine environment

Synthetic microfiber pollution is a growing concern in the marine environment. However, critical issues associated with microfiber origins in marine environments have not been resolved. Herein, the potential sources of marine microfibers are systematically reviewed. The obtained results indicate that surface runoffs are primary contributors that transport land-based microfibers to oceans, and the breakdown of larger fiber plastic waste due to weathering processes is also a notable secondary source of marine microfibers. Additionally, there are three main approaches for marine microplastic source apportionment, namely, anthropogenic source classification, statistical analysis, and numerical simulations based on the Lagrangian particle tracking method. These methods establish the connections between characteristics, transport pathways and sources of microplastics, which provides new insights to further conduct microfiber source apportionment. This study helps to better understand sources analysis and transport pathways of microfibers into oceans and presents a scientific basis to further control microfiber pollution in marine environments.

Monthly variation and transport of microplastics from the Soan River into the Indus River

The presence of plastic and microplastic pollution in freshwater systems receives extensive concerns for its accumulative trend and potential ecological impacts. This is the first annual study that investigated the monthly profile of plastic pollution in the mouth of the Soan River. Plastic pollutants comprising microplastic content up to 91.7 % were abundantly found during different seasons around the year, ranging from 132.7 items/m3 to 641.3 items/m3. The average abundance of plastics was significantly higher in August (641.3 ± 23.7 items/m3) than in other months. Overall, fibers, large microplastics (L-MPs), and transparent items were dominant by shape (57.7 %), size (61.9 %), and color (24.6 %), respectively. The highest average number of fibers (374.3/m3) and L-MPs (396 items/m3) were recorded during May and remained higher in the surface water from December to May. Fragments (432.3/m3) and S-MPs were observed higher (362.3 items/m3) during the peak rainy month of the summer monsoon season (August). Variations in the abundance and morphotypes were seemingly not only influenced by the seasonal change but also might be due to hydromorphological characteristics of the river, especially riverbed morphology, and the flow of the water. Only 5.2 % of the total items found were identified using μ-FTIR (micro-Fourier Transformed Infrared Spectroscope) which consisted of 70.7 % plastic items. Spectroscopy revealed that polyethylene terephthalate was an abundantly found polymer that largely prevailed in the form of fibers, followed by polypropylene and polyethylene. Most of the fragments, foams, and films were composed of polypropylene, polystyrene, and rayon respectively. Being an urban river, the polymeric profile demonstrated that anthropogenic activities had a significant impact on polluting the river. These findings are a very important source to understand the profile of plastic pollution in the Soan River and also a significant reference for policy-making in controlling plastic pollution among the riverine networks.

Polyacrylonitrile microfibers pose a significant threat to the early-stage survival of zebrafish

Microplastic pollution, especially microfibers (MFs), presents a critical global environmental challenge in natural water bodies. Yet, research on the toxic effects of MFs, particularly during early fish development, is limited. This study aimed to investigate MFs' toxic effects and mechanisms on early-stage zebrafish. Zebrafish embryos were exposed to varying concentrations of polyacrylonitrile microfibers (PanMfs) for 7 days. Results revealed PanMfs adhering to the embryos' surface, with higher concentrations accelerating heart rate and causing pericardial edema in post-hatching larvae. Larvae ingested PanMfs, leading to their accumulation in the intestines and increased levels of reactive oxygen species (ROS) and mitochondrial quantity. Notably, lipid metabolism and calcium ion related signaling pathways underwent significant changes. Low concentration MFs affected glycometabolism pathways, with potential roles for aldob and cacng1a, exhibiting pronounced increases in ROS levels. High concentration of MFs had the most profound impact on signal transduction-related pathways, and possibly triggering micromitophagy and apoptosis in zebrafish intestinal epithelial cells through the Kras/MAPK signaling pathway, with potential roles for kras and mapk9. Although ROS increase was somewhat alleviated, it resulted in decreased survival rates and restricted growth in high concentration of MFs group. These findings highlight the significant threat of MFs to the early survival of fish. MFs pollution prevention and control hold great significance in the conservation of fishery resources.

Microplastics as an emerging contaminant of concern to our environment: a brief overview of the sources and implications

Over the years, it has become evident that microplastics are one of the most important contaminants of concern requiring significant attention. The large abundance of microplastics that are currently in the environment poses potential toxicity risks to all organisms that are exposed to them. Microplastics have been found to affect the physiological and biological processes in marine and terrestrial organisms. As well as being a contaminant of concern in itself, microplastics also have the ability to act as vectors for other contaminants. The potential for microplastics to carry pollutants and transfer them to other organisms has been documented in the literature. Microplastics have also been linked to hosting antibiotic resistant bacteria and antibiotic resistance genes which poses a significant risk to the current health system. There has been a significant increase in research published surrounding the topic of microplastics over the last 5 years. As such, it is difficult to determine and find up to date and relevant information. This overview paper aims to provide a snapshot of the current and emerging sources of microplastics, how microplastics can act as a contaminant and have toxic effects on a range of organisms and also be a vector for a large variety of other contaminants of concern. The aim of this paper is to act as a tool for future research to reference relevant and recent literature in this field.

Microplastic distribution in different tissues of small pelagic fish of the Northeast Atlantic Ocean

The accumulation of microplastics (MP) by marine species of ecological and commercial interest represents a major concern, particularly for those present in human diet. This study analysed the accumulation of MP in three species of coastal pelagic fish with high commercial value, European sardine (Sardina pilchardus), European anchovy (Engraulis encrasicolus) and horse mackerel (Trachurus trachurus), collected along the Western coast of the Iberian Peninsula. The gastrointestinal tract (GT), gills and muscle were analysed and a total of 504 particles were observed. MP were found in all target tissues of the studied species. Horse mackerel exhibited significantly higher concentrations of microplastics in GT compared to other tissues. On the other hand, anchovies and sardines had significantly lower microplastic concentrations in their muscle tissue. The accumulation of microplastics in the gills showed a significant difference between species, with anchovy having significantly higher concentrations compared to horse mackerel. Horse mackerel had the highest percentage of individuals with microplastics in their GT (92 %), followed by sardine (75 %) and anchovy (50 %). Horse mackerel was also the species that registered the highest percentage of individuals with particles in the muscle (63 %), followed by anchovy (40 %) and finally sardine (39 %). MP in the gills of European sardines and anchovies were similar to those found in water samples. The majority of MP found measured <0.5 mm and were blue fibers. Furthermore, the presence of MP in the GT showed a weak and moderated significant negative correlation with the Fulton Condition Index in horse mackerel and European sardine. Our study confirms the ubiquitous extent of MP contamination in the ocean and provides baseline evidence of MP tissue distribution in three small pelagic fish species with distinct feeding behaviour, while correlating this with the presence of MP in water. Importantly, the results of this study contribute to improve the understanding of biological partitioning of MP in open sea fish species with high commercial relevance, and the potential deleterious effects of our increasingly MP contaminated world.

Microplastic contamination in commercial fish feeds: A major concern for sustainable aquaculture from a developing country

Plastic pollution has become a global issue nowadays. Due to the increased population in developing countries, we largely depend on fish from our aquaculture industry to meet the required protein demand. Though several studies documented plastic ingestion in freshwater and marine organisms, very limited studies have been conducted to elucidate microplastic (MP) contamination in commercial fish feed. Therefore, this study was designed to identify, quantify, and characterize microplastics (MPs) in commercial fish feeds in Bangladesh and assess possible health risks in fish consuming different commercial fish feeds. All fish feed samples were 100 % contaminated with MPs, where the mean abundance of MPs ranged between 500 and 2200 MPs/kg. No significant differences among different types of feeds (e.g., starter, grower, and finisher) were observed in terms of MPs abundance (F = 0.999, p = 0.385). This study revealed that fiber was the most dominant shape of MPs (90 %), while the most dominant color of MPs was red (34 %), followed by black (31 %) and blue (19 %). The 100-1500 µm size class covers 88 % of the total MPs in the collected fish feed samples. Identified polymers in the samples were polyethylene (PE, 37.71 %), polyvinyl chloride (PVC, 27.14 %), polypropylene (PP, 22.08 %), and polyethylene terephthalate (PET, 13.07 %), respectively, where PE and PVC fall under the risk category IV to V. The Pollution load index (PLI) values of all fish feed samples were <10, indicating the risk category of I (low risk). Therefore, this study highly recommended avoiding plastic materials in the packaging and storing purposes of feed ingredients in the feed mills to ensure contamination-free fish feed for sustainable aquaculture.

Is 5 mm still a good upper size boundary for microplastics in aquatic environments? Perspectives on size distribution and toxicological effects

Plastic is everywhere as an essential component of industries' products, but accumulation and degradation of plastics into microplastics occurs continuously in aquatic environments. Despite numerous studies investigating the influence of microplastics, challenges remain when comparing comprehensive results due to the lack of agreement regarding microplastics sizes. Over 80 studies and reports were reviewed, revealing the inconsistencies in defining the upper size limit for microplastics, and are the basis of this exploration of the need to redefine the latter by focusing on pragmatic factors such as size distribution and toxicity endpoints in aquatic environments. Reviewed articles indicate a gap between recommendations for microplastics definitions and the current status of microplastics. We suggest initiating a discussion regarding downscaling the broadly accepted 5 mm upper limit to 1000 μm, considering environmentally realistic conditions and SI nomenclature. We encourage continued international discussion of redefining the upper size limit defining microplastics from this pragmatic view.

Microplastics in aquaculture systems: Occurrence, ecological threats and control strategies

With the intensification of microplastic pollution globally, aquaculture environments also face risks of microplastic contamination through various pathways such as plastic fishing gear. Compared to wild aquatic products, cultured aquatic products are more susceptible to microplastic exposure through fishing tackle, thus assessing the impacts of microplastics on farmed species and human health. However, current research on microplastic pollution and its ecological effects in aquaculture environments still remains insufficient. This article comprehensively summarizes the pollution characteristics and interrelationships of microplastics in aquaculture environments. We analyzed the influence of microplastics on the sustainable development of the aquaculture industry. Then, the potential hazards of microplastics on pond ecosystems and consumer health were elucidated. The strategies for removing microplastics in aquaculture environments are also discussed. Finally, an outlook on the current challenge and the promising opportunities in this area was proposed. This review aims to evaluate the value of assessing microplastic pollution in aquaculture environments and provide guidance for the sustainable development of the aquaculture industry.

Effects Caused by the Ingestion of Microplastics: First Evidence in the Lambari Rosa (Astyanax altiparanae)

Microplastics are a class of contaminants that pose a threat to aquatic biota, as they are easily found in aquatic ecosystems and can be ingested by a wide variety of organisms, such as fish. The lambari rosa (Astyanax altiparanae) is a microphage fish, which feeds on microscopic beings and particles, making it potentially susceptible to ingesting MPs discarded in the environment. In addition, this fish is of great economic and food importance, as it is used for human consumption. This study aimed to evaluate the accumulation and possible toxicological effects caused to lambari rosa (n = 450) by the ingestion of polyethylene (PE) and polyethylene terephthalate (PET) MPs, since the MPs of these polymers in the form of granules, fragments, and fibers are the most commonly reported in the aquatic environment. The parameters investigated here were the quantitative analysis of ingested MPs using microscopic and staining techniques, as well as the mortality rate, malformations/injuries, and impaired weight gain. At the end of the experiment, it was concluded that MPs from both polymers accumulated in the gastrointestinal tract of the lambari rosa, and that dietary exposure, especially to the PET polymer, was responsible for increasing the mortality rate in this species.

Nano- and micro-polystyrene plastics interfered the gut barrier function mediated by exosomal miRNAs in rats

Microplastics (MPs) are widely distributed in the global environment, entering and accumulating in organisms in various ways and posing health threats. MPs can damage intestine; however, the mechanism by which MPs cause intestinal damage in rats is unclear. Here, rats were exposed to 50 nm PS-NPs or 5 μm PS-MPs for 4 weeks to evaluate the possible effects on intestinal barrier function and exosomal miRNAs expressions. The results showed that PS-NPs or PS-MPs disrupted the gut microbiota and affected gut barrier function at the biological level. In addition, PS-NPs and PS-MPs altered the composition of exosomal miRNAs in the intestinal and serum. Both PS-NPs and PS-MPs decreased the expression of miR-126a-3p in the intestinal and serum exosomes, which is an important signalling molecule involved in MPs induced gut barrier function disorder. More importantly, both in vitro and in vivo experiments indicated that miR-126a-3p was closely related to oxidative damage of intestinal cells through the PI3K-Akt pathway and eventually promote cell apoptosis by regulating the target gene of PIK3R2. Our study suggested that PS-NPs and PS-MPs could affect rat intestinal barrier function through an exosomal miRNA mediated pathway.

Chromium (IV) transfer to Amusium pleuronectes by LDPE microplastics: An experimental study

An experiment was carried out to investigate the potential of virgin LDPE microplastics to transfer heavy metals. Desired shapes (fibres, fragments, and films) and sizes (< 5 mm) of virgin LDPE microplastics were immersed in a known concentration (30 µg/l) of chromium (IV). These Cr-coated microplastics were introduced into a culture tank containing edible scallops (Amusium pleuronectes). After the completion of the experiment (5 days), the sediments in the culture tank and edible tissues of A. pleuronectes were tested for the presence of Cr. In the sediments, a maximum concentration of 1.934 µg/g of Cr was accumulated at a rate of R2 = 0.979, while in the tissues, the maximum accumulation concentration was 0.733 µg/g of Cr at a rate of R2 = 0.807. Energy Dispersive X-ray Spectroscopy analysis also confirmed the presence of Cr (2.61 ± 0.44 mass % and 1.80 ± 0.30 atom%) in the tissues of A. pleuronectes, which was absent in the control tissues. The study showed that when exposed to contaminants such as heavy metals, LDPE microplastics can adhere and transfer them to biotic tissues. LDPE showed the potential to transfer adhered contaminants; however, the effects caused by these transferred contaminants on biota must be studied further. Risk assessment study showed that potential ecological risk of Cr is < 40 indicating low risk however, the combined effect of Cr and LDPE can compound its toxicity which needs to be studied further.

Investigations of hemato-biochemical and histopathological parameters, and growth performance of walking catfish (Clarias batrachus) exposed to PET and LDPE microplastics

Fish inhabiting various trophic levels are affected differently as the presence of microplastic (MP) in the water column and their ingestion by fish varies. Walking catfish (Clarias batrachus) inhabits the bottom of the water bodies. To understand the effects of MP, we exposed C. batrachus to two types of MP - polyethylene terephthalate (PET) and low-density polyethylene (LDPE) for 60 days. After exposure, hematological indices, mainly red blood cells and hemoglobin levels decreased, and white blood cells increased significantly compared to the control group (p < 0.05). A significant increase in the levels of blood urea and glucose was observed, and serum glutamic pyruvate transaminase and serum glutamyl oxaloacetic transaminase activity remained elevated (p < 0.05). Histopathological examination of the liver, kidney, intestine, and gills showed morphological alterations. Moreover, MP exposure caused growth retardation (p < 0.05) in C. batrachus. Widespread pollution of water bodies by MP may impose serious ecological risks to bottom-feeding fish in Bangladesh.

The Microplastics Iceberg: Filling Gaps in Our Understanding

Plastic is an indispensable material in modern society; however, high production rates combined with inadequate waste management and disposal have resulted in enormous stress on ecosystems. In addition, plastics can become smaller particles known as microplastics (MPs) due to physical, chemical, and biological drivers. MP pollution has become a significant environmental problem affecting terrestrial and aquatic ecosystems worldwide. Although the topic is not entirely new, it is of great importance to the field of polymers, drawing attention to specific gaps in the existing literature, identifying future areas of research, and improving the understanding of MP pollution and its environmental impacts. Despite progress in this field, problems remain. The lack of standardized methods for MP sampling, separation, extraction, and detection makes it difficult to collect information and establish links between studies. In addition, the distribution and pathways of MPs in ecosystems remain unknown because of their heterogeneous nature and the complex matrices in which they occur. Second, toxicological tests showed that MPs can be ingested by a wide range of organisms, such as Danio rerio and Eisenia fetida, resulting in gut obstruction, physical damage, histological changes, and oxidative stress. The uptake of MP and their toxicological effects depend on their shape, size, concentration, and polymer composition. Furthermore, MPs can enter the food chain, raising concerns regarding potential contaminations for human and environmental health. This review paper sheds light on the pressing issue of MP pollution and highlights the need for interdisciplinary collaboration between scientists, policymakers, and industry leaders.

Species-specific effects of microplastics on juvenile fishes

Microplastics contamination have been extensively reported in aquatic ecosystem and organisms. It is wildly acknowledged that the ingestion, accumulation and elimination of microplastics in fishes are species-specific, which mainly depending on the feeding behavior. This study aimed to investigate the effects of microplastics on the morphology and inflammatory response in intestines of fishes with different feeding types. Largemouth bass (carnivorous fish), grass carp (herbivorous fish) and Jian carp (omnivorous fish) were used as organism model. The contributing concentration and size of microplastics were explored as well as the response time and legacy effect in fishes. Two different sizes of polystyrene microplastics (80 nm and 8 μm) were set at three concentrations. And samples were analyzed at different exposure times and depuration times. Histological analysis indicated that multiple abnormalities in intestines were presented in three species fishes after acute exposure microplastics. The mRNA abundance of immune-related genes in the intestine tissues of fishes were significantly fluctuant. There were differential expressions of genes coping with differential sizes and concentrations of microplastics exposure in different fishes. The reason for the difference effects of microplastics on fishes was still unclear but could be due to the difference in the structure and function of the digestive system. These results provided a theoretical basis to further analysis of the mechanism of fish intestinal pathology caused by microplastics.

Effect of Microplastics on the Activity of Digestive and Oxidative-Stress-Related Enzymes in Peled Whitefish (Coregonus peled Gmelin) Larvae

Microplastics (MPs) are emergent pollutants in freshwater environments and may impact aquatic organisms, including those of nutritional value. The specific activities of digestive and antioxidant enzymes can be used as good bioindicators of the potential effects of MPs on fish in case of waterborne MP contamination. In this study, we used fluorescent polystyrene microplastics (PS-MPs) to analyze the alterations in enzyme activities in larvae of Coregonus peled Gmelin (peled or Northern whitefish), one of the most valuable commercial fish species of Siberia. Our results indicate that peled larvae can ingest 2 µm PS microspheres in a waterborne exposure model. A positive correlation (r_s = 0.956; p < 0.01) was found between MP concentration in water and the number of PS microspheres in fish guts, with no significant differences between 24 h and 6-day exposure groups. The ingestion of MPs caused alterations in digestive enzyme activity and antioxidant responses at the whole-body level. The presence of PS-MPs significantly stimulated (p < 0.05) the specific activity of α-Amylase and non-specific esterases in peled larvae after 24 h. However, a pronounced positive effect (p < 0.05) of MPs on the activity of pancreatic trypsine and bile salt-activated lipase was only found after 6 days of exposure compared to after 24 h. Intestinal membrane enzyme aminopeptidase N was also stimulated in the presence of PS-MPs after 6-day exposure. We also observed a significant increase in the specific activity of catalase in peled larvae after 6 days of exposure, which indicates the MP-induced modulation of oxidative stress. Taken together, these results highlight the potential impact of environmental MPs on northern commercial fish, their importance for estimating fish stocks, and the sustainability of freshwater ecosystems.

Impact of polystyrene microplastic exposure on gilthead seabream (Sparus aurata Linnaeus, 1758): Differential inflammatory and immune response between anterior and posterior intestine

Plastics are the most widely discharged waste into the aquatic ecosystems, where they break down into microplastics (MPs) and nanoplastics (NPs). MPs are ingested by several marine organisms, including benthic and pelagic fish species, contributing to organ damage and bioaccumulation. This study aimed to assess the effects of MPs ingestion on gut innate immunity and barrier integrity in gilthead seabreams (Sparus aurataLinnaeus, 1758) fed for 21 days with a diet enriched with polystyrene (PS-MPs; 1-20 μm; 0, 25 or 250 mg /kg b.w./die). Physiological fish growth and health status were not impacted by PS-MPs treatments at the end of experimental period. Inflammation and immune alterations were revealed by molecular analyses in both anterior (AI) and posterior intestine (PI) and were confirmed by histological evaluation. PS-MPs triggered TLR-Myd88 signaling pathway with following impairment of cytokines release. Specifically, PS-MPs increased pro-inflammatory cytokines gene expression (i.e., IL-1β, IL-6 and COX-2) and decreased anti-inflammatory ones (i.e., IL-10). Moreover, PS-MPs also induced an increase in other immune-associated genes, such as Lys, CSF1R and ALP. TLR-Myd88 signaling pathway may also lead to the mitogen-activated protein kinases (MAPK) signaling pathway activation. Here, MAPK (i.e., p38 and ERK) were activated by PS-MPs in PI, following the disruption of intestinal epithelial integrity, as evidenced by reduced gene expression of tight junctions (i.e. ZO-1, Cldn15, Occludin, and Tricellulin), integrins (i.e., Itgb6) and mucins (i.e., Muc2-like and Muc13-like). Thus, all the obtained results suggest that the subchronic oral exposure to PS-MPs induces inflammatory and immune alterations as well as an impact on intestinal functional integrity in gilthead seabream, with a more evident effect in PI.

Toxic effects of microplastic (Polyethylene) on fish: Accumulation, hematological parameters and antioxidant responses in Korean Bullhead, Pseudobagrus fulvidraco

Plastic waste discharged into the aquatic environment decomposes into microplastics (MP), which have toxic effects on fish species. Korean bullhead, Pseudobagrus fulvidraco is widely distributed in freshwater ecosystems in Korea, and it is important as an ecological indicator species to evaluate MP toxicity in Korea. In this study, the accumulation and physiological effects of juvenile P. fulvidraco exposed to microplastics (Polyethylene: PE-MPs with white surface and spherical shape) at control (0 mg/L), 100, 200, 5000 and 10,000 mg/L for 96 h were confirmed. Exposure to PE-MPs showed significant bioaccumulation of P. fulvidraco, and the accumulation profile was in the order of gut > gills > liver. Hematological parameters such as the red blood cell (RBC), hemoglobin (Hb) and hematocrit (Ht) were significantly decreased over 5000 mg/L In plasma components, calcium, magnesium and total protein were significantly decreased over 5000 mg/L, whereas glucose, cholesterol, aspartate aminotransferase (AST), alanine transaminase (ALT) and alkaline phosphatase (ALP) were significantly increased over 5000 mg/L or at 10,000 mg/L In antioxidant responses, superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) were significantly increased over 5000 mg/L, whereas glutathione (GSH) was significantly decreased over 5000 mg/L. The results of this study suggest that acute exposure to PE-MPs induced all physiological changes in a concentration-dependent manner, and it affects the hematological parameters, plasma components and antioxidant response of juvenile P. fulvidraco after accumulation in specific tissues.

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.

Effects of microplastics in freshwater fishes health and the implications for human health

The presence of microplastics in aquatic environments has raised concerns about their abundance and potential hazards to aquatic organisms. This review provides insight into the problem that may be of alarm for freshwater fish. Plastic pollution is not confined to marine ecosystems; freshwater also comprises plastic bits, as the most of plastic fragments enter oceans via rivers. Microplastics (MPs) can be consumed by fish and accumulated due to their size and poor biodegradability. Furthermore, it has the potential to enter the food chain and cause health problems. Evidence of MPs s ingestion has been reported in >150 fish species from both freshwater and marine systems. However, microplastic quantification and toxicity in freshwater ecosystems have been underestimated, ignored, and not reported as much as compared to the marine ecosystem. However, their abundance, influence, and toxicity in freshwater biota are not less than in marine ecosystems. The interaction of MPs with freshwater fish, as well as the risk of human consumption, remains a mystery. Nevertheless, our knowledge of the impacts of MPs on freshwater fish is still very limited. This study detailed the status of the toxicity of MPs in freshwater fish. This review will add to our understanding of the ecotoxicology of microplastics on freshwater fish and give subsequent research directions.

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.

Increase in temperature increases ingestion and toxicity of polyamide microplastics in Nile tilapia

Microplastics (MP) pollution and global warming are worldwide concerns, creating various physiological problems for aquatic organisms. This study was carried out to know the effects of different temperature (30, 33 and 36 °C) on ingestion of MP along with the physiological consequences in Nile tilapia (Oreochromis niloticus) exposed to virgin polyamide (PA) (10 mg/L water; 500 μm to 4 mm in size) for 15 days. A significant difference was found in PA ingestion of the fish treated with different temperature. Fish from 36 °C temperature groups ingested highest amount of PA (136 ± 24.40 item/fish) during the exposure period. The hemoglobin (Hb) and red blood cell (RBC) decreased significantly in the highest temperature (36 °C) without PA exposure. At the same time, Hb increased, but RBC significantly reduced in all the temperature conditions with PA exposure. The number of white blood cell (WBC) and glucose level increased significantly in the highest temperature (36 °C) without PA exposure. In contrast, WBC increased and glucose decreased significantly in all the temperature conditions with PA exposure. Frequencies of various nuclear and cellular abnormalities of erythrocytes increased significantly in the fish exposed to all temperature with PA exposure, though severity increased with temperature. Similarly, histological damage of gills (hyperplasia, epithelial necrosis, deformed pillar system, epithelial lifting, telangiectasia) and intestine (epithelium breakage, enterocyte vacuolization and shortening of villi) was found to be mild to severe by the accumulation of PA, increased severity with increase of temperature. This study confirms that global warming as a consequence of climate change might influence MP ingestion hampering physiological state of fish.

Multi-biomarkers hazard assessment of microplastics with different polymers by acute embryo test and chronic larvae test with zebrafish (Danio rerio)

Microplastics as emerging contaminants show various composition features in the environment. However, influence of polymer types on the toxicity of microplastics is still unclear, thus affecting evaluation of their toxicity and ecological risks. In this work, toxic effects of microplastics (fragment, 52-74 μm) with different polymer types including polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP) and polystyrene (PS) to zebrafish (Danio rerio) were studied using acute embryo test and chronic larvae test. Silicon dioxide (SiO₂) was used as a control representing natural particles. Results showed microplastics with different polymers had no influence on embryonic development at environmental relevant concentration (10² particles/L), but could lead to accelerated heartbeat rate and increased embryonic death when exposed to SiO₂, PE and PS at higher concentrations (10⁴ and 10⁶ particles/L). Chronic exposure for zebrafish larvae indicated different polymers of microplastics did not affect zebrafish larvae' feeding and growth, nor induce oxidative stress. But larvae' locomotion level and AChE (acetylcholinesterase) activities could be inhibited by SiO₂ and microplastics at 10⁴ particles/L. Our study demonstrated negligible toxicity of microplastics at environmental relevant concentration, while different polymers of microplastics have similar toxic effects as SiO₂ at high concentrations. We suggest that microplastic particles may have the same biological toxicity as natural particles.

Microplastics in water, feed and tissues of European seabass reared in a recirculation aquaculture system (RAS)

Plastic particles (PLs) are ubiquitous in aquatic ecosystems and aquaculture production is susceptible to contamination from external or endogenous sources. This study investigated PL presence in water, fish feed and body sites of 55 European seabass produced in a recirculating aquaculture system (RAS). Fish morphometric parameters and health status biomarkers were determined. A total of 372 PLs were recovered from water (37.2 PL/L), 118 PLs from feed (3.9 PL/g), and 422 from seabass (0.7 PL/g fish; all body sites analysed). All 55 specimens had PLs in at least two of the four body sites analysed. Concentrations were higher in the gastrointestinal tract (GIT; 1.0 PL/g) and gills (0.8 PL/g) than in the liver (0.8 PL/g) and muscle (0.4 PL/g). PL concentration in GIT was significantly higher than in muscle. Black, blue, and transparent fibres made of man-made cellulose/rayon and polyethylene terephthalate were the most common PLs in water and seabass, while black fragments of phenoxy resin were the most common in feed. The levels of polymers linked to RAS components (polyethylene, polypropylene, and polyvinyl chloride) were low suggesting a limited contribution to the overall PL levels found in water and/or fish. The mean PL size recovered from GIT (930 μm) and gills (1047 μm) was significantly larger than those found in the liver (647 μm) and dorsal muscle (425 μm). Considering all body sites, PLs bioconcentrated in seabass (BCF_Fish >1) but their bioaccumulation did not occur (BAF_Fish <1). No significant differences were observed in oxidative stress biomarkers between fish with low (<7) and high (≥7) PL numbers. These findings suggest that fish produced in RAS are mainly exposed to MPs through water and feed. Further monitoring under commercial conditions and risk assessment are warranted to identify potential threats to fish and human health and define mitigating measures.

Additive effects of microplastics on accumulation and toxicity of cadmium in male zebrafish

Microplastics (MPs) have emerged as contaminants of concern because of their ubiquitous presence in almost all aquatic environments. The ecological effects of MPs are complex and depend on multiple factors including their age, size and the ecological matrix. There is an urgent need for multifactorial studies to elucidate their impacts. We measured the effects of virgin and naturally aged MPs, alone, pretreated with cadmium (Cd), or in combination with ionic Cd, on the bioaccumulation of Cd, metallothionein expression, behavior, and histopathology of adult zebrafish (Danio rerio). Zebrafish were exposed to virgin or aged polyethylene MPs (0.1% MPs enriched diets, w/w) or waterborne Cd (50 μg/L) or a combination of the two for 21 days. There was an additive interaction between water-borne Cd and MPs on bioaccumulation in males but not in females, Cd accumulation increased by twofold when water-borne Cd and MPs were combined. Water-borne Cd significantly induced higher levels of metallothionein compared to MPs pre-exposed to Cd. However, Cd-treated MPs caused greater damage to the intestine and liver compared to untreated MPs suggesting that bound Cd could be released or modulate MPs toxicity. We also showed that co-exposure to water-borne Cd and MPs increased anxiety in the zebrafish, compared with water-borne Cd alone, suggesting using microplastics as a vector may increase toxicity. This study demonstrates that MPs can enhance the toxicity of Cd, but further study is needed to elucidate the mechanism.

Microplastics in aquatic species of Anzali wetland: An important freshwater biodiversity hotspot in Iran

Coastal wetlands are sensitive ecosystems that give habitat to large number of species. The extent of the impact of microplastic pollution in the aquatic system and humans is not known. In this study, the occurrence of microplastics (MPs) was assessed in 7 aquatic species from the Anzali Wetland (40 fish and 15 shrimp specimens), a listed wetland on the Montreux record. Specifically, the tissues analyzed were gastrointestinal (GI) tract, gills, skin, and muscles. The total frequency of MPs (all detected MPs in the GI tract, gill and skin samples) varied from 5.2 ± 4.2 MPs/specimen for Cobitis saniae to 20.8 ± 6.7 MPs/specimen for Abramis brama. Among all tissues studied, the GI tract of the Chelon saliens, a herbivorous demersal species, had the greatest level of MPs (13.6 ± 10 MPs/specimen). Significant differences (p < 0.05) were found between the abundance of MPs in different species, tissues, living domains and feeding habit types. The findings support that fish may uptake MPs through adherence in gills (respiration) in addition to ingestion. White/transparent and black/grey polyamide (PA) fibers were the most common type of MP which may be originated from municipal wastewater and intensive fishing activities. About 34% of the MPs were in the range of 250 μm-500 μm, and those >100 μm were not detected in muscles from the study fish. All species had unhealthy weight according to the Fulton's condition index (K). Positive relationships existed between biometric properties (total length and weight) of species and the total frequency of uptaken MPs, pointing to detrimental impact of MPs in the wetland.

Presence, variation, and potential ecological impact of microplastics in the largest shallow lake of Central Europe

The presence of microplastics (MPs) in the global ecosystem has generated a rapidly growing concern worldwide. Although their presence in the marine environment has been well-studied, much less data are available on their abundance in freshwaters. MPs alone and in combination with different chemicals has been shown to cause acute and chronic effects on algae and aquatic invertebrate and vertebrate species at different biological levels. However, the combined ecotoxicological effects of MPs with different chemicals on aquatic organisms are still understudied in many species and the reported data are often controversial. In the present study, we investigated, for the first time, the presence of MPs in Lake Balaton, which is the largest shallow lake of Central Europe and an important summer holiday destination. Moreover, we exposed neonates of the well-established ecotoxicological model organism Daphnia magna to different MPs (polystyrene [3 μm] or polyethylene [≤ 100 μm]) alone and in combination with three progestogen compounds (progesterone, drospirenone, levonorgestrel) at an environmentally relevant concentration (10 ng L^-1) for 21 days. The presence of 7 polymer types of MPs in the size range of 50-100 μm was detected in Lake Balaton. Similarly to the global trends, polypropylene and polyethylene MPs were the most common types of polymer. The calculated polymer-independent average particle number was 5.5 particles m^-3 (size range: 50 μm - 100 μm) which represents the values detected in other European lakes. Our ecotoxicological experiments confirmed that MPs and progestogens can affect D. magna at the behavioral (body size and reproduction) and biochemical (detoxification-related enzyme activity) levels. The joint effects were negligible. The presence of MPs may lead to reduced fitness in the aquatic biota in freshwaters such as Lake Balaton, however, the potential threat of MPs as vectors for progestogens may be limited.