Accumulation of microplastics in fish guts and gills from a large natural lake: Selective or non-selective?

The first evidence of microplastic presence in the River Nile in Khartoum, Sudan: Using Nile Tilapia fish as a bio-indicator

The extent of microplastics in African freshwater systems remains less investigated. In Sudan, there is no single study reporting microplastics in water bodies. This scoping study aimed to investigate the presence and characteristics of microplastics (MPs) in Nile Tilapia fish from the River Nile in Khartoum, Sudan. The digestive tracts of the fish were digested using 10% potassium hydroxide, and microplastic particles were extracted by density separation using sodium iodide. 567 particles of different sizes (0.04-4.94 mm), shapes (fibers, fragments, films, foams, and pellets), and colours (mostly green, black, blue, and grey) were identified as microplastics. The average abundance of microplastics was 72.02 ± 62.06 particles/kg, and the average intensity was 18.90 ± 9.17 MPs/fish. Small-sized (<1 mm), fibrous-shaped, and coloured microplastics were most abundant in all samples, representing 56%, 85%, and 84%, respectively. Surface examination by SEM showed signs of fragmentation such as cracks, pits, and pores. Two polymer types (high-density polyethylene and polypropylene) were identified by Raman spectroscopy. The predominance of fibers and fragments (94.5%) over pellets (0.35%) and the apparent signs of fragmentation may indicate that MPs are mostly secondary MPs. Wastewater effluent, domestic discharge, and recreational activities are the potential sources. This scoping investigation provided the first data on microplastic presence in the River Nile in Khartoum, and it could be used to guide future studies to fill research gaps in the region.

Biodegradation of microplastics: Advancement in the strategic approaches towards prevention of its accumulation and harmful effects

Microplastics (MPs) are plastic particles in a size ranging from 1 mm to 5 mm in diameter, and are formed by the breakdown of plastics from different sources. They are emerging environmental pollutants, and pose a great threat to living organisms. Improper disposal, inadequate recycling, and excessive use of plastic led to the accumulation of MP in the environment. The degradation of MP can be done either biotically or abiotically. In view of that, this article discusses the molecular mechanisms that involve bacteria, fungi, and enzymes to degrade the MP polymers as the primary objective. As per as abiotic degradation is concerned, two different modes of MP degradation were discussed in order to justify the effectiveness of biotic degradation. Finally, this review is concluded with the challenges and future perspectives of MP biodegradation based on the existing research gaps. The main objective of this article is to provide the readers with clear insight, and ideas about the recent advancements in MP biodegradation.

Microplastics Contamination in the Edible Fish Mozambique Tilapia (Oreochromis mossambicus) from the Selvampathy Wetland of Coimbatore, Tamil Nadu, India

The present study investigated the microplastics (MPs) contamination in the gastrointestinal (GI) tract, gills and muscle of the Mozambique tilapia, Oreochromis mossambicus sampled from the Selvampathy Lake of Coimbatore, Tamil Nadu. MPs abundance was found in 10 to 28, 8 to 27, and 4 to 12 particles and their size ranged between 4.4 and 210, 4.6 to 180, and 4.5 to 194 μm in the GI tract, gills and muscle, respectively. MPs were dominantly shaped as fibres (95%) and fragments (5%) with the following colour pattern of blue > black > pink > transparent > and others. Extracted MPs polymer nature were polyethylene (54%), polyamide (38%) and polypropylene (8%). The present study reveals that the edible fish O. mossambicus had MPs that can be transferred to consumers. Moreover, urban discharges, including domestic wastes, agricultural and rainwater runoff, might be possible MPs sources to the studied wetland.

Microplastics: challenges of assessment in biological samples and their implication for in vitro and in vivo effects

Microplastics (MPs) have attracted global interest because they have been recognized as emerging pollutants that require urgent attention. MPs are plastic particles with a size between 1 micron and 5 mm (1 µm-5mm); those measuring less than 1 µm are known as nanoplastics (NPs). MP is distributed in the environment in various physical forms that depend on the degradation process, the erosion factors to which it was subjected, or the original form in which it was intentionally manufactured. Humans may be exposed to these pollutants mainly by ingestion or inhalation, which could adversely affect human health with effects that are still unknown due to limitations that are often dependent on their analytical determination and lack of studies over time, as it is a relatively new topic. Therefore, this review focuses on the challenges currently faced by laboratories for determining MPs in different matrices. We highlight the application of methods and techniques to assess the precise levels of exposure to MPs in biological samples. In addition, exposure pathways, sources, and evidence of adverse effects reported in vitro and in vivo studies are described to generate knowledge about their potential threat to human health.

Plastic, It's What's for Dinner: A Preliminary Comparison of Ingested Particles in Bottlenose Dolphins and Their Prey

Microplastic ingestion was reported for common bottlenose dolphins (Tursiops truncatus) inhabiting Sarasota Bay, FL, USA, a community that also has prevalent exposure to plasticizers (i.e., phthalates) at concentrations higher than human reference populations. Exposure sources are currently unknown, but plastic-contaminated prey could be a vector. To explore the potential for trophic exposure, prey fish muscle and gastrointestinal tract (GIT) tissues and contents were screened for suspected microplastics, and particle properties (e.g., color, shape, surface texture) were compared with those observed in gastric samples from free-ranging dolphins. Twenty-nine fish across four species (hardhead catfish, Ariopsis felis; pigfish, Orthopristis chrysoptera; pinfish, Lagodon rhomboides; and Gulf toadfish, Opsanus beta) were collected from Sarasota Bay during September 2022. Overall, 97% of fish (n = 28) had suspected microplastics, and GIT abundance was higher than muscle. Fish and dolphin samples contained fibers and films; however, foams were common in dolphin samples and not observed in fish. Suspected tire wear particles (TWPs) were not in dolphin samples, but 23.1% and 32.0% of fish muscle and GIT samples, respectively, contained at least one suspected TWP. While some similarities in particles were shared between dolphins and fish, small sample sizes and incongruent findings for foams and TWPs suggest further investigation is warranted to understand trophic transfer potential.

Characterization of microplastics in digestive tract of commercial fish species from the Oman Sea

Microplastics (MPs) content of the digestive tract of two commercial fish from the northern shores of the Oman Sea were investigated. The MPs were characterized by optical microscopy, fluorescent microscopy, and SEM-EDX for their number, shape, size, and color. Polymer composition was analyzes using micro-Raman spectroscopy (RMS). MPs were recovered in all fish samples (100 %), with an average of 43.16 ± 8.23 items/individual in Otolithes ruber, and 29.9 ± 2.73 items/individual in Acanthopagrus latus. The predominant shape of MPs in both fishes was fiber (46 %) with black, transparent, and white colors. The majority of MPs were <1000 μm (75 %), and half of the MPs were smaller than 300 μm in size. Their synthetic nature was confirmed by Nile Red staining and determination of the elemental composition of selected items. Polypropylene (PP) and polyethylene (PE) were the dominant plastic polymers in the fish digestive tracts. This study reveals abundance distribution of MPs in digestive tract of commercial marine fish. High number of ingested MPs can alarm the accumulation of MPs in the northern of Oman Sea ecosystem with anthropogenic activities and raises issues in public health.

The organism fate of inland freshwater system under micro-/nano-plastic pollution: A review of past decade

Micro- and nano-plastics (MPs/NPs) are characterized by their small size and extensive surface area, making them global environmental pollutants with adverse effects on organisms at various levels, including organs, cells, and molecules. Freshwater organisms, such as microalgae, emerging plants, zooplankton, benthic species, and fish, experience varying impacts from MPs/NPs, which are prevalent in both terrestrial and aquatic inland environments. MPs/NPs significantly impact plant physiological processes, including photosynthesis, antioxidant response, energy metabolism, and nitrogen removal. Extended exposure and ingestion to MPs/NPs might cause metabolic and behavioral deviations in zooplankton, posing an extinction risk. Upon exposure to MPs/NPs, both benthic organisms and fish display behavioral and metabolic disturbances, due to oxidative stress, neural toxicity, intestinal damage, and metabolic changes. Results from laboratory and field investigations have confirmed that MPs/NPs can be transported across multiple trophic levels. Moreover, MPs/NPs-induced alterations in zooplankton populations can impede energy transfer, leading to food scarcity for filter-feeding fish, larvae of benthic organism and fish, thus jeopardizing aquatic ecosystems. Furthermore, MPs/NPs can harm the nervous systems of aquatic organisms, influencing their feeding patterns, circadian rhythms, and mobility. Such behavioral alterations might also introduce unforeseen ecological risks. This comprehensive review aims to explore the consequences of MPs/NPs on freshwater organisms and their interconnected food webs. The investigation encompasses various aspects, including behavioral changes, alterations in physiology, impacts on metabolism, transgenerational effects, and the disruption of energy transfer within the ecosystem. This review elucidated the physiological and biochemical toxicity of MPs/NPs on freshwater organisms, and the ensuing risks to inland aquatic ecosystems.

Toxicological impacts of microplastics on human health: a bibliometric analysis

Plastic has been known as an artificial polymer whereas environmental microplastics become a global concern. Microplastics are reported to cause immunotoxicity in humans through gut deposition and entering the bloodstream. This study is a comprehensive indication of the recent research on microplastic toxicity in the gastrointestinal system. We performed bibliographic analysis using VOS viewer software and analyzed the data received on microplastics and their impact on gut health which has grown exponentially since 2016. Recent findings also support microplastic toxicity in combination with heavy metals. The smaller particle size and other factors enhanced the adsorption ability of environmental contamination such as heavy metals on microplastic which increased their bioaccumulation. Such toxic complexes of heavy metals and microplastics are a concern to natural ecosystems and environmental biologists. Few reports also demonstrated the biofilm formation on microplastic surfaces which might cause greater environmental as well as human health risks. Notably, terms of determining the microplastics in human tissues through several analytical techniques are still limited to some extent. Future research should be focused on the quantification of microplastics in human tissues, the combined effect of microplastics with other contaminants, and their effects on pre-existing diseases. This study boosts understanding of the potential impacts of microplastic and nanoplastic toxicity in the human gastrointestinal system.

Toxic effect of chronic exposure to polyethylene nano/microplastics on oxidative stress, neurotoxicity and gut microbiota of adult zebrafish (Danio rerio)

The rapid development of aquaculture industry has provided a large amount of high-quality animal protein, while the food safety caused by microplastics and nanoplastics (MP/NPs) has become a major concern. In addition, recent evidence has shown the potential toxic effect of PE-MP/NPs, highlighting the need for further research into their environmental and health impacts. Chronic exposure of polyethylene microplastics (PE-MPs) and nanoplastics (PE-NPs) on adult zebrafish were conducted in the present study for 21 d. Organ-dependent oxidative damage induced by MP/NPs was observed. Insignificant differences in neurotoxicity and dysbiosis of gut microbiota were found between MPs and NPs. Changes in glutathione S-transferase (GST), glutathione (GSH), catalase (CAT), lipid peroxidation (LPO), and superoxide dismutase (SOD) showed that MP/NPs induced oxidative damage in gill and intestinal cells of zebrafish. The inhibited AChE activity suggested the potential neurotoxicity of microplastics and nanoplastics (MP/NPs). In addition, chronic exposure increased the alpha-diversity of intestinal microbiota. At the phylum level, the average relative abundance of Proteobacteria increased from 29.73% (control group) to 66.10% (microplastics), 54.84% (nanoplastics) and 60.03% (combined exposure), respectively. Tenericutes decreased from 55.43% (control group) to 20.02% (microplastics), 22.44% (nanoplastics) and 31.77% (combined exposure), respectively. Overall, this study provides new insights and objective evidence for the toxicity assessment of PE-MPs.

An effect assessment of microplastics and nanoplastics interacting with androstenedione on mosquitofish (Gambusia affinis)

An increasing number of microplastics have been detected in aquatic environments, causing various damage to organisms. The size of microplastics affects the toxicity once they enter the organisms. Meanwhile, there is an increasing variety of Endocrine-disrupting chemicals (EDCs) present in aquatic environments. Androstenedione (AED) is a typical EDC. In this study, we used polystyrene microspheres of 80 nm (NPs) and 8 μm (MPs) as materials to simulate environmental contaminants in the aquatic environment with AED. We used female mosquitofish (Gambusia affinis) as the research object to investigate the effects of microplastics on fish in waters containing AED. We compared different sizes of particles accumulation in some tissues of fish and variation of enzyme activities (SOD, LDH, CAT), and the content of MDA in the gut. MPs, NPs, and AED combined exposure test investigated mRNA profiles of immune-related genes (IL-1β, IL-6, IL-8, IL-10) and hormone receptor genes (ARα, ARβ, ERα, ERβ) in the liver of fish. Our results indicated that MPs emerged in various tissues (gill, gut, and liver) of mosquitofish. Besides, NPs and MPs caused enteric abnormal enzyme activity after 48 h of exposure, which was particularly pronounced in the MPs-AED group. MPs induced significant upregulation of inflammatory factors and gonadal factor genes after 96 h of exposure, which was more pronounced when co-exposed with AED. In conclusion, NPs and MPs caused mechanisms of immune damage and inflammatory response. MPs were found to be more likely to cause adverse reactions than NPs, and these responses were enhanced by the combined effects of AED. This study demonstrated that AED can exacerbate the negative effects of MPs and NPs on mosquitofish. It provided an important basis for the effective assessment of MPs and NPs on bioaccumulation and biochemical status of mosquitofish. Additionally, it serves as a foundation to investigate the interactive effects of microplastics and EDCs in living organisms.

High microplastics concentration in liver is negatively associated with condition factor in the Benguela hake Merluccius polli

Microplastics (MPs) affect both marine and terrestrial biota worldwide for their harmful effects, which range from physical cell damage to physiological deterioration. In this research, microplastics were quantified from gills, liver and muscle of demersal Benguela hakes Merluccius polli (n = 94), caught by commercial trawling from northwest African waters. Plastic polymers were identified using Fourier Transformed-infraRed spectroscopy (FT-iR). Fulton's k condition factor and the degree of DNA degradation in liver were measured. None of the individuals were free of MPs, whose concentration ranged from 0.18 particles/g in muscle to 0.6 in liver. Four hazardous polymers were identified: 2-ethoxyethylmethacrylate, polyester, polyethylene terephthalate, and poly-acrylics. MP concentration in liver was correlated negatively with the condition factor, suggesting physiological damage. Positive association of MP concentration and liver DNA degradation was explained from cell breakage during trawl hauls during decompression, suggesting an additional way of MPs harm in organisms inhabiting at great depth. This is the first report of potential MPs-driven damage in this species; more studies are recommended to understand the impact of MP pollution on demersal species.

Exploring microplastic pollution in a Mediterranean river: The role of introduced species as bioindicators

Studies of plastic contamination in freshwater ecosystems and their biota remain scarce, despite the fact that the vast majority of plastic waste initially passes through lotic ecosystems. Biomonitoring provides valuable information regarding plastic pollution and microplastic threats to biota and human health. The aim of this study was to explore the potential use of a non-indigenous fish species as a bioindicator of microplastic pollution in an Eastern Mediterranean River. Our study area is located in a heavily modified and vastly impacted urban river which flows through the largest part of the Metropolitan area of Athens, Greece. We used an introduced chub species (Squalius vardarensis) to assess microplastic ingestion in the river. The results indicated moderate occurrence and abundance of microplastics in the fish gastrointestinal tracts; one-third of specimens (35%) contained microplastics, although the average number of microplastics per specimen was relatively low (1.7 ± 0.2). Overall, the abundance of microplastics in the water confirmed the moderate level of microplastics contamination in our study area. The major polymer types of microplastics identified by FT-IR analysis were: polyethylene (PE), polyvinyl alcohol (PVA) and polypropylene (PP); reflecting the fragmentation of larger litter from industrial packaging and/or household goods. Surface runoff of the urban environment, via motorways and major road networks, could be the contributing factor to the reported microplastics. Our results suggest that generalist's non-indigenous species such as chubs could be used as bioindicators of microplastics in inland waters. Introduced fishes can be a feasible, nondestructive, and cost-effective option for the assessment of microplastics in freshwater ecosystems, while freshwater chubs' high abundance and omnipresence in European rivers further serve this scope. However, it is worth noting that the suitability of any particular species as a bioindicator of microplastics may depend on a variety of factors, including their feeding behavior, habitat, and exposure to microplastics in their environment.

A global synthesis of microplastic contamination in wild fish species: Challenges for conservation, implications for sustainability of wild fish stocks and future directions

Research on the occurrence of microplastics in wild fish populations is a constantly growing area, requiring continuous reviews to properly keep up with the fast pace of publications and guide future work. This review analyses the scientific output of 260 field studies covering 1053 different fish taxa for the presence of microplastics. To date, microplastics have been recorded in 830 wild fish species, including 606 species of interest to commercial and subsistence fisheries. Among these, based on IUCN Red List status, 34 species are globally classified in one of the three threatened categories (Critically Endangered, Endangered or Vulnerable) and another 22 species were assessed as "Near Threatened". Of the species for which the IUCN Red List tracks population trend data, the fish species reported to have microplastics so far include 81 which are recorded as declining, 134 as stable and just 16 as increasing. This review highlights the potential implications of fish microplastic contamination to biodiversity conservation, sustainability of wild fish stocks, and human food safety and security. Finally, recommendations for future research are presented.

Microplastic pollution in aquatic environments may facilitate misfeeding by fish

Numerous recent studies have documented ingestion of microplastics (MPs) by many aquatic animals, yet an explanation for misfeeding by fish remains unexplained. Here we tested the hypothesis that biofilm (biofouling) on MP surfaces due to exposure in the aquatic environment facilitates misfeeding in fish. Spherical polystyrene (PS) was cultured for 0-22 weeks in a freshwater environment to grow a biofilm on the MPs. Goldfish were employed in a simple feeding experiment with and without provision of genuine food at ecologically relevant MP concentrations. Absorbance (ABS), which is a proxy for biofilm formation, increased exponentially within three weeks of initiation and reached a plateau after approximately five weeks. Although fish did not swallow the MPs, "capture" occurred when food pellets were in the vicinity and significantly increased in probability with aging. Duration of capture also increased significantly with increasing aging. These results suggest that drifting of MPs in aquatic environments may facilitate fish misidentification of MPs as edible prey.