Microplastic distribution, abundance, and composition in the sediments, water, and fishes of the Red and Mediterranean seas, Egypt

Abundance, characteristics and ecological risks of microplastics from South Yellow Sea Mudflat

Microplastic (MP) pollution in global marine environments has been extensively reported and attracted significant concerns, but MP distribution in mudflat has rarely been studied. In this paper, the abundance, features and ecological risk of MP in South Yellow Sea Mudflat were investigated comprehensively. MP were both detected in waters (5.4 ± 0.38-11.3 ± 0.78 items/L) and sediments (5.1 ± 0.36-10.1 ± 0.69 items/g) from South Yellow Sea Mudflat. There existed different MP abundance tendencies from sampling Group I (coastal estuary or port) and II (purely coastal mudflat), while MP abundance in water from Group II was lower than that from Group I generally, but MP abundance in sediment from Group I was lower than that from Group II generally. This suggested that MP abundance in mudflat water could be associated with frequent human activities significantly, and disturbance might not be beneficial to MP accumulation in sediments. Fragments, transparent, polyethylene (PE), polypropylene (PP) and polystyrene (PS) were major MP features in mudflat water and sediment, and maximum proportion of size of MP was 0.001-0.25 mm in both water and sediment. Furthermore, the primary risk assessment indicated that MP pollution load for mudflat was low level. However, potential MP ecological risk for mudflat could reach dangerous level to very dangerous level by calculating and evaluating polymer risk index (PRI) and potential ecological risk index (PERI), which could be caused by high proportions of polyvinyl chloride (PVC) and polyacrylonitrile (PAN) with high hazard score. For the first time, reference data about MP pollution from South Yellow Sea Mudflat were supplied in this paper, which would be helpful for management and control of MP in mudflat.

Microplastics in wild fish in the Three Gorges Reservoir, China: A detailed investigation of their occurrence, characteristics, biomagnification and risk

Microplastics (MPs) pollution in freshwater poses a risk to various ecosystems and health security. In 2018, the Chinese government banned fishing since 2018 in the Three Gorges Reservoir (TGR), but the fate and risk of MPs in wild fish remain unclear. Therefore, a detailed investigation was conducted into the occurrence of MPs in 18 wild fish species in the TGR using a Micro Fourier Transform Infrared Spectrometer, and the trophic transfer and risks were assessed. MPs in fish were aged, with abundances ranging from 0.68 ± 0.98 to 4.00 ± 2.12 items/individual. Most particles were less than 1 mm in size (73.4 %), with fibers being the dominant shape (48.9 %) and transparent as the dominant color (35 %). Polyethylene (PE) was the most prevalent type. The bioconcentration factor (BCF), bioaccumulation factor (BAF), trophic magnification factor (TMF) and polymer hazard index (PHI) were low, suggesting no trophic transfer and a low risk of MPs. The BAF may provide a more reasonable description of the degree of enrichment of MPs, and 'items/individual' or 'g/individual' can be used to describe MPs concentrations in fish. This study proposes new insights and prospectives that can help researchers better understand MPs enrichment in fish across various trophic levels.

Single and combined toxicity of tadalafil (Cilais) and microplastic in Tilapia fish (Oreochromis niloticus)

The joint impact of tadalafil (Cilais) as a pharmaceutical residue and microplastics on fish is not well comprehended. The current study examined haematological, biochemical, and antioxidant parameters, along with immunohistochemical and histological indications in tilapia (Oreochromis niloticus) after being exposed to tadalafil, polyethylene microplastics (PE-MPs), and their mixtures for 15 days. The fish were distributed into 1st group control group (The fish was maintained in untreated water without any supplements); 2nd group exposed to 10 mg/L PE-MPs;3rd group exposed to 20 mg/l tadalafil (Cilais); 4th group exposed to 20 mg/l tadalafil (Cilais) + 10 mg/LPE-MPs (in triplicate). The levels of creatinine, uric acid, glucose, AST, ALT, and albumin in fish treated with tadalafil alone or in combination with PE-MPs were significantly higher than those in the control group. Fish exposed to PE-MPs, tadalafil, and tadalafil plus PE-MPs showed significantly lower levels of RBCs, Hb, Ht, neutrophils, and lymphocytes compared to the control group. Serum levels of total antioxidant capacity and reduced glutathione (GSH) were notably lowered in fish groups subjected to PE-MPs, tadalafil, and tadalafil + PE-MPs combinations in comparison to the control group. Malondialdehyde (MDA) serum levels were notably elevated in fish groups subjected to PE-MPs, tadalafil, and tadalafil + PE-MPs combinations compared to the control group. The most severe impact was observed in the tadalafil + PE-MPs combination group. Interleukin-6 (IL-6) levels were significantly increased in liver tissues following exposure to both tadalafil and microplastics compared to tissues exposed to only one substance or the control group. Changes in the gills, liver, and renal tissues were seen following exposure to PE-MPs, tadalafil, and tadalafil + PE-MPs combination in comparison to the control group of fish. Ultimately, the mixture of tadalafil and PE-MPs resulted in the most detrimental outcomes. Tadalafil and PE-MPs exhibited showed greater adverse effects, likely due to tadalafil being absorbed onto PE-MPs.

The retention of plastic particles by macrophytes in the Amazon River, Brazil

This study evaluated the presence of plastics and microplastics in macrophytes in an urbanized sector of the Amazon River. A total of 77 quadrats in 23 macrophyte banks were sampled during the dry (September 2020) and rainy (June 2021) season. Five species were identified: Paspalum repens, Pontederia rotundifolia, Pistia stratiotes, Salvinia auriculata and Limnobium laevigatum, with P. repens being dominant during the dry season (47.54%) and P. rotundifolia during the rainy season (78.96%). Most of the plastic particles accumulated in Paspalum repens (49.3%) and P. rotundifolia (32.4%), likely due to their morphological structure and volume. The dry season showed a higher accumulation of plastic particles than the rainy season. Microplastics were found in most samples, during both the dry (75.98%) and rainy seasons (74.03%). The upstream macrophyte banks retained more plastic particles compared to the downstream banks. A moderate positive correlation was observed between the presence of plastic particles and macrophyte biomass, and a weak positive correlation between the occurrence of microplastics and mesoplastics. White and blue fragments, ranging from 1 to 5 mm were the most common microplastics found in the macrophyte banks. Green fragments and green and blue fibers were identified as polypropylene, blue and red fragments as polyethylene, and white fragments as polystyrene. Therefore, the results of this study highlight the first evidence of the retention of plastic particles in macrophytes of the Amazon and highlight a significant risk due to the harmful effects that this type of plastic can cause to the fauna and flora of aquatic ecosystems.

Assessment of Microplastics and Potentially Toxic Elements in Surface Sediments of the River Kelvin, Central Scotland, United Kingdom

Contamination of the environment by microplastics (MPs), polymer particles of <5 mm in diameter, is an emerging concern globally due to their ubiquitous nature, interactions with pollutants, and adverse effects on aquatic organisms. The majority of studies have focused on marine environments, with freshwater systems only recently attracting attention. The current study investigated the presence, abundance, and distribution of MPs and potentially toxic elements (PTEs) in sediments of the River Kelvin, Scotland, UK. Sediment samples were collected from eight sampling points along the river and were extracted by density separation with NaCl solution. Extracted microplastics were characterised for shape and colour, and the polymer types were determined through attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Pollution status and ecological risks were assessed for both the microplastics and PTEs. Abundance of MPs generally increased from the most upstream location (Queenzieburn, 50.0 ± 17.3 particles/kg) to the most downstream sampling point (Kelvingrove Museum, 244 ± 19.2 particles/kg). Fibres were most abundant at all sampling locations, with red, blue, and black being the predominant colours found. Larger polymer fragments were identified as polypropylene and polyethylene. Concentrations of Cr, Cu, Ni, Pb and Zn exceeded Scottish background soil values at some locations. Principal component and Pearson's correlation analyses suggest that As, Cr, Pb and Zn emanated from the same anthropogenic sources. Potential ecological risk assessment indicates that Cd presents a moderate risk to organisms at one location. This study constitutes the first co-investigation of MPs and PTEs in a river system in Scotland.

The power of Posidonia oceanica meadows to retain microplastics and the consequences on associated macrofaunal benthic communities

In the coastal environment, a large amount of microplastics (MPs) can accumulate in the sediments of seagrass beds. However, the potential impact these pollutants have on seagrasses and associated organisms is currently unknown. In this study, we investigated the differences in MPs abundance and composition (i.e., shape, colour and polymer type) in marine sediments collected at different depths (-5 m, -15 m, -20 m) at two sites characterized by the presence of Posidonia oceanica meadows and at one unvegetated site. In the vegetated sites, sediment samples were collected respectively above and below the upper and lower limits of the meadow (-5 m and -20 m), out of the P. oceanica meadow, and in the central portion of the meadow (-15 m). By focusing on the central part of the meadow, we investigated if the structural features (i.e. shoots density and leaf surface) can affect the amount of MPs retained within the underlying sediment and if these, in turn, can affect the associated benthic communities. Results showed that the number of MPs retained by P. oceanica meadows was higher than that found at the unvegetated site, showing also a different composition. In particular, at vegetated sites, we observed that MPs particles were more abundant within the meadow (at - 15 m), compared to the other depths, on unvegetated sediment, with a dominance of transparent fragments of polypropylene (PP). We observed that MPs entrapment by P. oceanica was accentuated by the higher shoots density, while the seagrass leaf surface did not appear to have any effect. Both the abundance and richness of macrofauna associated with P. oceanica rhizomes appear to be negatively influenced by the MPs abundance in the sediment. Overall, this study increases knowledge of the potential risks of MPs accumulation in important coastal habitats such as the Posidonia oceanica meadows.

Microplastics in aquatic ecosystems of Africa: A comprehensive review and meta-analysis

Microplastic pollution is a global issue of great public concern. Africa is flagged to host some of the most polluted water bodies globally, but there is no enough information on the extent of microplastic contamination and the potential risks of microplastic pollution in African aquatic ecosystems. This meta-analysis has integrated data from published articles about microplastic pollution in African aquatic ecosystems. The data on the microplastic distribution and morphological characteristics in water, sediments and biota from African rivers, lakes, oceans and seas were extracted from 75 selected studies. Multivariate statistics were used to critically analyze the effects of sampling and detection methods, ecological risks, spatial distribution and similarity of microplastics in relation to the geographical distance between sampling sites. This study found that sampling methods have significant effect on abundance and morphological characteristics of microplastics and that African aquatic ecosystems are highly contaminated with microplastics compared to global data. The most prevalent colors were white, transparent and black, the most prevalent shapes were fibres and fragments, and the most available polymers were polypropylene (PP), polystyrene (PS) and polyethene terephthalate (PET). Microplastic polymers similarity decreased with an increase in geographical distance between sites. Risk levels of microplastics in African aquatic ecosystems were comparatively high, and more than 40 % of water and sediments showed highest level of ecological risk. This review provides recent information on the prevalence, distribution and risks of microplastics in African aquatic ecosystems.

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.

Microplastics in marine invertebrates from the Red Sea Coast of Egypt: Abundance, composition, and risks

This study marked the first exploration of microplastics in marine invertebrates in the Red Sea Coast of Egypt. 110 individuals from 11 different species, including Bivalvia, Gastropoda, Echinoidea, and Holothuroidrea, were collected near a popular tourist destination. The average concentrations of microplastics varied among species, ranging from 8.2 to 136.5 items per individual or 0.2 to 18.1 items per gram of tissue wet weight, with 100 % occurrence. Bivalves had higher concentrations per gram of tissue compared to sediment dwellers and grazers, with Brachidontes pharaonis showing the highest levels. Actinopyga crassa, a sea cucumber, displayed the highest abundance per individual due to its large size and behavior. The identified plastic polymers suggested sources associated with tourism and maritime activities. The estimated human exposure to microplastics through bivalve consumption was minimal. Further research is needed to examine microplastics contamination in the Red Sea and its potential impacts on ecosystems and human well-being.

Quantifying microplastics pollution in the Red Sea and Gulfs of Suez and Aqaba: Insights from chemical analysis and pollution load assessment

Microplastics (MPs) constitute the majority of marine plastic litter. The pollution caused by MPs has been categorized as a gradual and persistent crisis, but little is known about its extent along the shores of the Red Sea, particularly on the Egyptian side. The Red Sea is a rapidly developing region and home to critical ecosystems with high levels of endemism. This study represents the first comprehensive survey investigating the extent of MP pollution along the Egyptian shores of the Red Sea, including the Gulf of Suez and Aqaba. Mean concentrations ranged from 23.3 ± 15.28 to 930.0 ± 181.9 MPs/kg DW. Out of 17 beaches surveyed, 12 had mean concentrations of <200 items/kg, indicating a low occurrence of MPs compared to the shores of the Mediterranean Coast of Egypt. The pollution load index varied from low to medium levels in most locations. Ras Mohamed, a marine protected area, showed high vulnerability to MP pollution. All the investigated particles were fragments of secondary MPs. The sources of pollution mainly come from maritime activities, including cargo shipping and intense recreational activities. Fourier Transform Infrared Spectroscopy identified four plastic polymers, with polyethylene and polypropylene being the most common. The surface morphology of plastic particles was examined using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy. All the particles exhibited signs of degradation, which could generate countless plastic pieces with possible deleterious impacts. This work has highlighted the importance of conducting region-specific assessments of mismanaged plastic waste, focusing on the role of tourism and recreational navigation as contributors to plastic litter, to estimate plastic waste inputs into the waters of the Red Sea Coast of Egypt. Efforts are needed to develop strategic plans to reduce the disposal of plastic waste in the region.

Plastic Contamination in Seabass and Seabream from Off-Shore Aquaculture Facilities from the Mediterranean Sea

We characterized the presence of plastics in different organs of the gilthead seabream (Sparus aurata) and European seabass (Dicentrarchus labrax) from some off-shore aquaculture facilities of the Mediterranean Sea. Plastics were detected in 38% of analyzed fish. Higher contamination was observed in fish from Turkey and Greece with respect to Italy, without significant differences between the geographical areas. Plastics accumulated mostly in the gastrointestinal tract and, to a lower extent, in the muscle, which represents the edible part of fish. Based on the particle detected, a maximum amount of 0.01 plastic/g wet weight (w.w.) can occur in muscles, suggesting a low input for humans through consumption. A large portion of the particles identified was represented by man-made cellulose-based fibers. The characterization of the polymeric composition suggests that plastics taken up by fish can have land-based and pelagic origins, but plastics can be introduced also from different aquaculture practices.

Spatio-temporal distribution of microplastic abundances in Izmir Bay (eastern Aegean Sea)

Microplastics (MPs) and their impacts have been extensively studied in the Mediterranean region. However, more research has yet to be conducted on assessing the extent of microplastic (MP) pollution in the eastern Aegean Sea, specifically in Izmir Bay. This study aims to evaluate the current state of MP pollution in surface water and sediment samples collected from Izmir Bay. Ten sampling stations were specifically selected, including locations near stream discharge points, maritime transportation piers, and port areas. Surface water samples were collected using a manta trawl net, while sediment samples were obtained using a Van Veen grab. The mean MP abundances in surface water ranged from 1,083,882 to 8,091,684 items/km2. Fragment type MPs were dominant. In terms of size category, it was found that MP s of 500µm size were dominant. The dominant color of MPs was white. ATR-FTIR analyses revealed that polyethylene and polypropylene were the dominant polymer types. MP concentrations in sediment ranged from 2,125 to 4,925 items/m2, with fiber-type MPs being the most abundant. Black-colored MPs were found to dominate in sediment samples. Overall, the MP levels in Izmir Bay were higher than previous studies findings. Therefore, it is crucial to conduct long-term monitoring studies to obtain more consistent and reliable data on MP pollution levels in Izmir Bay.

Occurrence and distribution of meso- and macroplastics in the water, sediment, and fauna of the Nile River, Egypt

The present study described the most recent findings concerning the abundance and distribution of plastic in water, sediment, and fauna in the Nile River of Upper Egypt as an interesting research point. The findings revealed that plastics were abundant in the water, sediments, fish, and crayfish throughout the sites. The Nagaa Hammadi site has the highest abundance of meso- and macroplastics in its water and sediment. African catfish had the highest abundance of meso- and macroplastics compared to the other species, while Nile tilapia had no meso- or macroplastics in its alimentary canal or gills in all sites. The Edfu site has the highest abundance of mesoplastics in the alimentary canals of African catfish, while the Nagaa Hammadi site has the highest abundance of mesoplastics in the gills, and macroplastics appeared only in the alimentary canal of African catfish from the El-wasta site. Only mesoplastics were found in the crayfish's alimentary canal, with the Nagaa Hammadi site having the highest abundance. No macroplastics were detected in the crayfish's gills or alimentary canal. Additionally, this work lets us understand how plastics behave in freshwater environments, and it is a step toward decision-makers taking appropriate measures to reduce their risk.

Microplastics in coastal and oceanic surface waters and their role as carriers of pollutants of emerging concern in marine organisms

Microplastics (Mps) pose a significant environmental challenge with global implications. To examine the effect of Mps on coastal and oceanic surface waters, as well as in marine organisms, 167 original research papers published between January 2013 and September 2022 were analyzed. The study revealed an unequal distribution of research efforts across the world. Fragments and fibers were the most frequently detected particles in ocean surface waters and marine biota, which mainly consisted of colored and transparent microparticles. Sampling of Mps was primarily done using collecting nets with a mesh size of 330 μm. Most articles used a stereomicroscope and Fourier-Transform Infrared spectroscopy for identification and composition determination, respectively. Polyethylene and polypropylene were the most frequent polymers found, both in coastal waters and in marine organisms. The major impact observed on marine organisms was a reduction in growth rate, an increase in mortality, and reduced food consumption. The hydrophobic nature of plastics encourages the formation of biofilms called the "plastisphere," which can carry pollutants that are often toxic and can enter the food chain. To better define management measures, it is necessary to standardize investigations that assess Mp pollution, considering not only the geomorphological and oceanographic features of each region but also the urban and industrial occupation of the studied marine environments.

Occurrence and risks of microplastics in the ecosystems of the Middle East and North Africa (MENA)

The ubiquitous nature of microplastics (MPs) in nature and the risks they pose on the environment and human health have led to an increased research interest in the topic. Despite being an area of high plastic production and consumption, studies on MPs in the Middle East and North Africa (MENA) region have been limited. However, the region witnessed a research surge in 2021 attributed to the COVID-19 pandemic. In this review, a total of 97 studies were analyzed based on their environmental compartments (marine, freshwater, air, and terrestrial) and matrices (sediments, water columns, biota, soil, etc.). Then, the MP concentrations and polymer types were utilized to conduct a risk assessment to provide a critical analysis of the data. The highest MP concentrations recorded in the marine water column and sediments were in the Mediterranean Sea in Tunisia with 400 items/m³ and 7960 items/kg of sediments, respectively. The number of MPs in biota ranged between 0 and 7525 per individual across all the aquatic compartments. For the air compartment, a school classroom had 56,000 items/g of dust in Iran due to the confined space. Very high risks in the sediment samples (Erⁱ > 1500) were recorded in the Caspian Sea and Arab/Persian Gulf due to their closed or semi-closed nature that promotes sedimentation. The risk factors obtained are sensitive to the reference concentration which calls for the development of more reliable risk assessment approaches. Finally, more studies are needed in understudied MENA environmental compartments such as groundwater, deserts, and estuaries.

The pollution of microplastics in sediments: The ecological risk assessment and pollution source analysis

The occurrence of microplastics (MPs) pollution in sediments has brought huge challenges to the development of society. Pollution control of MPs in sediments has become an inevitable requirement for current society. This requires implementing targeted pollution control measures in high MPs ecological risk areas and controls MPs discharge in pollution source. Existing studies lack in-depth understanding in MPs ecological risk assessment and MPs pollution source analysis, this limits the pollution control of MPs in sediments. In this study, the studies of MPs pollution in sediments from 2013 to 2022 were reviewed. The results showed that the environmental problems caused by MPs pollution in marine sediments have been widely discussed over the past decade. And the occurrence of MPs pollution in sediments brought potential threat to marine ecology and human food supply. Furthermore, pollution load index, polymer risk index and potential ecological risk index of MPs were frequently used in the existing ecological risk assessment of MPs in sediments. A large amount of monitoring data and simulation data is conducive to improving these MPs ecological risk assessment indicators. This can provide a useful reference for managers to formulate MPs pollution control measures. And MPs types and land-use types can provide basis to analyze the pollution source of MPs in sediments. Developing more accurate MPs detection and analysis technologies can further improve current MPs pollution source analysis system. This is conducive to control the discharge of MPs in the pollution source. In future studies, more complete MPs ecological risk assessment system and MPs pollution source analysis system should be established to control the pollution of MPs in sediments.

Marine litter in the Red Sea: Status and policy implications

The Red Sea's unique ecosystem is home to >1500 species. However, the presence of anthropogenic litter, whether from land-based or sea-based sources, may pose a potential risk to the Red Sea fauna and flora. This work analyzes marine litter in the Red Sea, utilizing the Drivers-Pressure-State-Impact-Response (DPSIR) framework to group findings in a survey of peer-reviewed studies. The review is further augmented with a survey of the current response, covering regional and national instruments. Although research addressing marine litter in the Red Sea is not as rich as for other seas, studies suggest marine litter is abundant and that the influx of litter is driven by recreational activity, fishing, and shipping. Moreover, the COVID-19 pandemic has exacerbated the influx of marine litter to the Red Sea due to improper disposal of personal protective equipment (PPE). The response has intensified in recent years, with regional and national frameworks established and initiatives driven by Non-Governmental Organizations (NGOs). We discuss whether the regional action plan addresses the specific concerns uncovered in marine litter studies while providing a comparison with plans of other regional seas.

Protective efficacy of dietary natural antioxidants on microplastic particles-induced histopathological lesions in African catfish (Clarias gariepinus)

Microplastic particles (MPs) are a common environmental pollutant easily ingested by fish in aquaculture. The current study evaluated the protective efficacies of some antioxidant, e.g., lycopene, citric acid, and chlorella, against the toxic effects of MP ingestion by Clarias gariepinus using histopathological biomarkers. Five experimental groups were established, a control group receiving only a standard diet, a group exposed to 500 mg/kg MP concomitant with the standard diet, and three antioxidant groups exposed to MPs plus either lycopene (500 mg/kg), citric acid (30 g/kg), or chlorella (50 g/kg) in the standard diet. After 15 days, fish were sacrificed for histological and histochemical examinations. Histological analysis of the kidney for group 2 (fed 500 mg/kg MPs alone) revealed distributed tissue dissociation, regional glomerular hypertrophy or shrinkage, melanomacrophage accumulation, and expansion of Bowman's space, while liver tissue exhibited dilation and rupture of the central vein wall, hemorrhage, cytoplasmic vacuolation, and cellular necrosis or apoptosis. Fish exposed to MPs also exhibited connective tissue fiber accumulation around renal blood vessels, renal tubules, the central hepatic vein, hepatic blood sinusoids, and serosal, muscle, and submucosal layers of the intestine. In addition, MP exposure reduced carbohydrate (mainly glycogen) contents in the brush borders and basement membranes of renal tubules, glomeruli, and intestinal tissues as well as in the cytoplasm of hepatocytes. These signs of renal, hepatic, and intestinal histopathology were fully or partially reversed by dietary lycopene, chlorella, or citric acid. Enhancing dietary antioxidants is an effective strategy for preventing MP toxicity in Clarias gariepinus in aquaculture.

Detection of microplastic fibers tangle in deep-water rose shrimp (Parapenaeus longirostris, Lucas, 1846) in the northeastern Mediterranean Sea

Microplastic (MP) pollution in marine environments has been a major global concern in recent years. Microplastic particles pose a threat in aquatic animals by accumulating in their digestive system, acting like a pollution vector, and they can also transfer to upper trophic levels. For that reason, commercially important deep-water rose shrimp Parapenaeus longirostris were employed in this study to examine the MP pollution status of two different regions (Samandağ and Mersin offshore waters) of the northeastern Mediterranean Sea. MPs were detected in all examined specimens (average of 18.8 MPs ind-1), and fiber tangle-shaped like balls were observed by 22% and 9% at Samandağ and Mersin, respectively. P. longirostris individuals from Samandağ showed higher occurrence (100%) and higher accumulation (29.7 ± 24.4 MPs ind-1). MP abundance extracted from the shrimp individuals from Samandağ region was higher than that of previously reported shrimp species. The majority of extracted microplastics were fiber (100%), black (46%) in color and 1-2.5 mm in size. Polyethylene was identified as the most common polymer type by Fourier transform infrared spectroscopy (FTIR). This study is the first report to evaluate microplastic occurrence and fiber tangles in P. longirostris from northeastern Mediterranean Sea. Results obtained in this study will enhance the understanding of MP pollution among different trophic levels.

Microplastics in fish and sediments from the Montenegrin coast (Adriatic Sea): Similarities in accumulation

The accumulation of microplastics (MPs) in the biotic and abiotic components of the marine environment poses a major threat to marine ecosystems worldwide. The objective of this study was to document, for the first time, differences in MP accumulation in the gastrointestinal tract of two commercially important fish species and to evaluate the possible correlation between MP accumulation in the biotic (fish) and abiotic (sediment) components of the marine environment of the Montenegrin coast (Adriatic Sea). Samples were collected from two areas of the Montenegrin coast, Boka Kotorska Bay and the coastal part of the open sea. The frequency of MP ingestion was 58.6 % for Mullus barbatus and 54 % for Merluccius merluccius, while the average number of ingested MPs was 2.9 ± 0.5 and 3.2 ± 1.0 items/individual, respectively. Average MP abundance in surface sediments from Boka Kotorska Bay and the coastal part of the open sea was 315 ± 45 and 435 ± 258 MPs/kg of dry sediment, respectively. Most MPs identified were filaments, followed by fragments and films, while the most abundant polymers found in fish and sediments samples were polypropylene and polyethylene. The present results indicate that MP pollution in the study area is reflected in the accumulation of MPs in the biotic (fish) and abiotic (sediment) components of the marine environment. Measures need to be taken to reduce the input of plastics/MPs into the marine environment.

Neurotoxic effects of different sizes of plastics (nano, micro, and macro) on juvenile common carp (Cyprinus carpio)

Using common carp as a model, we assessed the effects of polyethylene (PE) plastics on the brain. We measured activity of acetylcholinesterase (AChE), monoamine oxidase (MAO), and the content of nitric oxide (NO) in carp brain following exposure to 100 mg/L of either macroplastics (MaP), microplastics (MPs), or nanoplastic (NPs) for 15 days compared to an unexposed group. Following exposure, each biochemical biomarker was reduced 30–40%, with a higher magnitude of change corresponding to the smaller size of the particles (NPs > MPs > MaPs). In the carp tectum, exposure for 15 days to plastic particles caused varying degrees of necrosis, fibrosis, changes in blood capillaries, tissue detachment, edema, degenerated connective tissues, and necrosis in large cerebellar neurons and ganglion cells. In the carp retina, there was evidence for necrosis, degeneration, vacuolation, and curvature in the inner layer. Here we provide evidence that exposure to plastic particles can be associated with neurotoxicity in common carp.

Occurrence of Natural and Synthetic Micro-Fibers in the Mediterranean Sea: A Review

Among microplastics (MPs), fibers are one of the most abundant shapes encountered in the aquatic environment. Growing attention is being focused on this typology of particles since they are considered an important form of marine contamination. Information about microfibers distribution in the Mediterranean Sea is still limited and the increasing evidence of the high amount of fibers in the aquatic environment should lead to a different classification from MPs which, by definition, are composed only of synthetic materials and not natural. In the past, cellulosic fibers (natural and regenerated) have been likely included in the synthetic realm by hundreds of studies, inflating “micro-plastic” counts in both environmental matrices and organisms. Comparisons are often hampered because many of the available studies have explicitly excluded the micro-fibers (MFs) content due, for example, to methodological problems. Considering the abundance of micro-fibers in the environment, a chemical composition analysis is fundamental for toxicological assessments. Overall, the results of this review work provide the basis to monitor and mitigate the impacts of microfiber pollution on the sea ecosystems in the Mediterranean Sea, which can be used to investigate other basins of the world for future risk assessment.

Microplastic occurrence in the gastrointestinal tract and gill of bioindicator fish species in the northeastern Mediterranean

Microplastic pollution is an extremely emerging problem and its potential threats to the aquatic organisms were investigated worldwide. In this study, four different commercial fish species (Mullus barbatus (Linnaeus, 1758), Mullus surmuletus (Linnaeus, 1758), Mugil cephalus (Linnaeus, 1758), Saurida undosquamis (Richardson, 1848)) were used as a bioindicator to assess the microplastic pollution in the northeastern Mediterranean. The frequency of occurrence in the gastrointestinal tract (GIT) and gill was varied between 66-100% and 68-90%, respectively. The highest microplastic abundance was detected at the GIT of M. cephalus sampled from Asi River estuary. The majority of extracted microplastics were fiber, black in color and less than 1 mm in size. Fourier Transform Infrared Spectroscopy (FTIR) indicated the most common polymer type as polyethylene. This study is the first study examining the microplastic existence in gill and results obtained in this study improve the knowledge about the relationship of microplastic ingestion in fish and environmental conditions in the Northeastern Mediterranean Sea.