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

Microplastic assessment in remote and high mountain lakes of Gilgit Baltistan, Pakistan

Microplastic (MP) pollution is a critical environmental challenge worldwide, however limited research is reported in remote lakes of Pakistan. This study assessed MPs (>5 mm) prevalence, distribution and risk perspective in water and sediment of eight remote and high-altitude lakes (>1500 m above sea level) of Gilgit Baltistan, Pakistan. The lakes exhibited an average abundance of 152.6 ± 104.6 to 12.1 ± 7 MP/kg of dry sediments and 2 ± 0.9 to 17.1 ± 17.2 MP/L of surface water. MPs <200 μm dominated in both matrices. Surface water predominantly contained polyester and polypropylene, while polypropylene and polyethylene dominated in sediments. The gradient of elevation did not show any pronounced impact on the fiber loading or MP count in both matrices. Backward air mass trajectory revealed that air masses vastly travelled from western-Asia, Arabian sea and Bay of Bengal with an average transmission distance of 2500-3500 km (500 m a.s.l) that can be a potential deposition MP source in the area. Pollution Load Index of the lakes were >1 exhibiting pollution. All other lakes except Batura and Borith manifested a moderate hazard index. Naltar lake along with aforementioned two lakes also manifested high polymer toxicity. Further research should emphasize understanding the mechanisms and biotic interactions in high-mountain ecosystems.

Detection of fibrous microplastics and natural microfibers in fish species (Engraulis encrasicolus, Mullus barbatus and Merluccius merluccius) for human consumption from the Tyrrhenian sea

The occurrence of natural/artificial and synthetic microfibers was assessed in three commercial fish species (Engraulis encrasicolus, Mullus barbatus, Merluccius merluccius) from the Tyrrhenian Sea sold for human consumption. The gastrointestinal tracts of n. 150 samples were analyzed, the isolated microfibers were classified applying a morphological approach, based on the analysis of their morphological features, coupled with the identification of the chemical composition of a subsample of microfibers. All the species contained microfibers at levels ranging from 0 to 49 items/individual and the number of ingested microfibers significantly differed between pelagic and demersal fishes. The evaluation of fiber morphologies highlighted that natural/artificial microfibers were the most numerous among the isolated microfibers, while the dominant colors were blue, black, and clear in all the species. Chemical characterization confirmed the morphological identification and indicated cellulose and polyester as the most common polymer types. Considering the analytical issues that may affect the evaluation of microfiber pollution, the results pointed out the importance of an accurate morphological approach that allows the distinction between different fiber types, before the spectroscopic analyses. Moreover, the implementation of fast and accessible methods to identify microfibers in fish species intended for human consumption will be beneficial also to make an adequate risk assessment to consumer health.

Microplastic characterization in the stomachs of swordfish (Xiphias gladius) from the western Mediterranean Sea

In this study, we aimed to quantify the presence of microplastics (MPs) in the stomachs of large pelagic fish (swordfish, Xiphias gladius, Linnaeus, 1758) sampled in the western Mediterranean Sea, and assess temporal trends (2011-2012 vs. 2017-2019) in MP ingestion. MPs were extracted from stomachs and characterized by μ-Fourier transform infrared spectroscopy. Results highlighted the ingestion of MP in 39 out of 49 stomachs analysed. Ingested MPs consisted mostly of small (<1 mm) fibers (88.6 %, mean ± standard deviation = 2.5 ± 6.1 particles per stomach), with a greater frequency of occurrence (FO) in the second period (FO = 90 %, 3.3 ± 8.0 particles per stomach). The predominant colours were purple, black and blue, and polyethylene terephthalate was the most frequently detected polymer. These results are crucial for the development of management actions aimed at the conservation of swordfish in the Mediterranean Sea and the prevention of health risks to humans.

First evidence of microplastics and their characterization in yellow-legged gull (Larus michahellis michahellis, Naumann, 1840) pellets collected from the Sfax salina, southeastern Tunisia

The aim of this work was to provide evidence on the presence of microplastics (MPs) in regurgitated Yellow-legged Gull pellets (n = 18) from Sfax salina (south-eastern Tunisia). This artificial area is subject to high anthropogenic pressure and hosts Yellow-legged Gulls, which are at the top of the trophic chain and can be used as sentinel species to monitor litter in the environment, including plastic pollution. The total number of MPs found in the samples was 309, 63.8 % fibres (4.95 ± 3.51 MPs/g) and 36.2 % fragments (2.87 ± 1.74 MPs/g). Micro-FTIR analysis evidenced that a large proportion of the fibres was attributed to artificial cellulose (40.7 %). Ethylene vinyl acetate (EVA) and polyethylene (PE) were found in the fragments.

Assessment of the impact of microplastic ingestion in striped red mullets from an Eastern Mediterranean coastal area (Zakynthos Island, Ionian Sea)

Monitoring microplastics (MPs) in the marine environment is an ongoing process, and our understanding of their impact on marine organisms is limited. The present study evaluates the effects of ingested MPs on the marine MP pollution bioindicator fish species Mullus surmuletus. The study follows a three-fold approach to assess the impact of MPs on marine organisms by investigating: 1) the ingestion of MPs, 2) the bioaccumulation of phthalate compounds as plastic additives, and 3) the evaluation of toxicological biochemical and cellular biomarkers. Striped red mullets were sampled in the marine protected area (MPA) of the National Marine Park of Zakynthos and coastal sites with high touristic pressure in Zakynthos Island in the Ionian Sea, Greece. Fewer ingested MPs and lower phthalate concentrations were found in fish inside the MPA compared to those sampled outside the marine park. However, no relationship was found between either phthalate concentrations or biomarker levels with the ingested MPs in the red striped mullets. Biomarker levels were influenced by season and site, but no effect could be attributed to the ingested MPs. The lack of association of biomarker responses and plasticizer bioaccumulation to MP ingestion can be explained by the low number of ingested MPs in the fish from Zakynthos coastal area as MP abundance ranged from 0.15 to 0.55 items per individual fish.

Tracking anthropogenic microparticles in wildlife of an alpine insular environment

Despite the isolation of remote natural regions, it has been discovered that they are experiencing the accumulation of anthropogenic microparticles (i.e., microplastics or natural or semisynthetic cellulosic particles). Teide National Park (Canary Islands, Spain) is a high-mountain protected area known for its rich biodiversity. This study aims to assess the occurrence of coloured anthropogenic particles in the faecal matter of wild mammals, specifically rabbits and mouflons, residing in the park. With this purpose, faeces were collected from 68 systematically distributed sampling points. A stereomicroscopy-guided grinding process allowed a chemical-free and quick visual inspection of 616 individual excreta, revealing that 96% were particle-free. However, 37 anthropogenic particles were found, which correspond to 0.79 ± 0.20 items per gram of dry faecal matter. The archetypical particle was a cellulosic blue microfibre of 2721 ± 407 µm, though poly(ethylene-vinyl acetate) and polypropylene were also identified via micro Fourier-transform infrared spectroscopic analysis. Atmospheric deposition and touristic pressure may be the sources of the anthropogenic particles, as they were randomly found in 36% of the sampling points. These findings represent the first evidence of anthropogenic particle ingestion by wild rabbits and mouflons, signifying the introduction of microplastics into terrestrial food chains in a remote high-mountain environment.

Spatio-temporal variation and ecological risk assessment of microplastics along the touristic beaches of a mediterranean coast transect (Valencia province, East Spain)

Annually, the Mediterranean region attracts around one-third of the global coastal tourism, which is acknowledged as a substantial contributor to plastic pollution. Coastal municipalities mitigate this through periodic sand and shore cleaning. However, the efficacy of these measures remains uncertain. In this study, the occurrence of MPs (10 μm-5 mm) in sand from seven different, regularly cleaned, touristic beaches of the coastline of Valencia province (E Spain) was assessed. Two different sampling campaigns were performed in winter and in summer (2022) to compare the results and understand the influence of the high touristic activity, as well as, the efficiency of the measures taken against MPs pollution. The methodology used was designed specifically for the matrix and employed density separation using a Sediment Microplastic Isolation (SMI) Unit. In addition to conventional visual inspection and ATR-FTIR, automatic quantification and identification of the polymers of lower size was performed by μFTIR. The average MPs concentration in the summer (339 ± 92 MP kg-1 by stereomicroscopy and 339 ± 189 MP kg-1 by μFTIR) was significantly higher than in the winter (71 ± 92 MP kg-1 and 143 ± 85 MP kg-1) (p < 0.05). The combination of these analytical tools provides comprehensive information about the MPs present in beach sand. Fibers were the most abundant form of MPs, while most of the polymers analyzed were polyethylene (PE) and halogenated polystyrene (Cl-PS and Br-PS) with food packaging, swimming equipment and fishing nets being their most probable sources. Ecological risk assessment was performed through the Pollution Load Index (PLI), the Hazardous Index (HI) and the Risk Quotient (RQ), with the results indicating potential risk that ranges from moderate to high depending on the applied approach.

The Occurrence of Microplastics in Donax trunculus (Mollusca: Bivalvia) Collected along the Tuscany Coast (Mediterranean Sea)

Microplastics (MPs) (0.1 µm-5 mm particles) have been documented in oceans and seas. Bivalve molluscs (BMs) can accumulate MPs and transfer to humans through the food chain. BMs (especially mussels) are used to assess MPs' contamination, but the genus Donax has not been thoroughly investigated. The aim of this study was to detect and characterize MPs in D. trunculus specimens collected along the Tuscan coast (Italy), and to assess the potential risk for consumers. The samples (~10 g of tissue and intervalval liquid from 35 specimens) were digested using a solution of 10% KOH, subjected to NaCl density separation, and filtered through 5 μm pore-size filters. All items were morphologically classified and measured, and their mean abundance (MA) was calculated. Furthermore, 20% of them were analyzed by Raman spectroscopy and, based on the obtained results, the MA was recalculated (corrected MA) and the annual human exposure was estimated. In the 39 samples analyzed, 85 items fibers (n = 45; 52.94%) and fragments (n = 40; 47.06%) were found. The MA was 0.23 ± 0.17 items/grww. Additionally, 83.33% of the items were confirmed as MPs (polyethylene and polyethylene terephthalate). Based on the correct MA (0.18 MPs/grww), D. trunculus consumers could be exposed to 19.2 MPs/per capita/year. The health risk level of MPs was classified as level III (moderate).

Are fishes selecting the trash they eat? Influence of feeding mode and habitat on microplastic uptake in an artificial reef complex (ARC)

Every year, coastal countries generate ∼275 million tons of plastic, and the oceans receive from 4.8 to 12.7 million tons3. Pollution by synthetic polymers is even more problematic for the environment when this material is fragmented into small portions, forming microplastics (MPs). In the present study, we analyze the selection of MPs by the ichthyofauna based on the availability of the morphotypes and polymeric composition of microplastic in the environment and compare the amount of MP in surface water, water column, sediments and fish in different organs, trophic categories, habitats and areas with and without artificial reefs. In order to achieve this goal, the shape, color, abundance and chemical composition of MPs in the digestive tract and gills of 18 fish species in artificial reefs area and control area, were evaluated. A total of 216 fish were analyzed, and 149 (60 %) had MPs in at least one organ and showed a mean concentration of 1.55 ± 3.31 MPs/g. Of the 18 fish species collected in the reef complex area, 17 (94 %) included individuals with at least one MP in digestive tract or gills. Four species showed the higher selectivity of MP types, colors, and polymers. More MPs were found in the fish, surface water, water column and sediment in the artificial reef area compared to the control areas. This is the first evidence of MP selection by commercially important fish species in artificial marine structures worldwide. These results provide useful information on MP pollution in RAs and highlight yet another issue that must be considered in the management of fisheries resources in the region and in other reef complexes around the world.

Microplastics in inland and offshore sediments in the Apulo-Lucanian region (Southern Italy)

Inland and offshore sediments from Southern Italy were studied in order to evaluate the occurrence and nature of microplastics (MPs). Inland sediments were collected in the Bradano and Basento rivers (Apulo-Lucanian region, Southern Italy), while offshore sediments were collected on the continental shelf near Bari (Adriatic Sea) and Metaponto (Ionian Sea). MPs were detected and characterized using optical microscopy, micro-Fourier-Transform Infrared spectroscopy (μ-FTIR) and micro-Raman analyses. The number of MPs present varied between 144 and 1246 kg-1 of dry sediment (468.8 ± 410,7 MPs kg-1) with a predominance of black fibers; no correlation emerged between MPs and sediment grain size. In river sediments, the occurrence of MPs is associated with local pollution, whereas the offshore occurrence of MPs depends on seasonal river flow and submarine canyons. Compositional analyses suggest that the main source of MPs in the studied sediments is sewage discharge from residential areas.

Testing of Different Digestion Solutions on Tissue Samples and the Effects of Used Potassium Hydroxide Solution on Polystyrene Microspheres

Microplastic particles are ubiquitous in our environment, having entered the air, the water, the soil, and ultimately our food chain. Owing to their small size, these particles can potentially enter the bloodstream and accumulate in the organs. To detect microplastics using existing methods, they must first be isolated. The aim of this study was to develop a non-destructive method for efficiently and affordably isolating plastic particles. We investigated the digestion of kidney, lung, liver, and brain samples from pigs. Kidney samples were analyzed using light microscopy after incubation with proteinase K, pepsin/pancreatin, and 10% potassium hydroxide (KOH) solution. Various KOH:tissue ratios were employed for the digestion of lung, liver, and brain samples. Additionally, we examined the effect of 10% KOH solution on added polystyrene microplastics using scanning electron microscopy. Our findings revealed that a 10% KOH solution is the most suitable for dissolving diverse organ samples, while enzymatic methods require further refinement. Moreover, we demonstrated that commonly used 1 µm polystyrene particles remain unaffected by 10% KOH solution even after 76 h of incubation. Digestion by KOH offers a simple and cost-effective approach for processing organ samples and holds potential for isolating plastic particles from meat products.

Impact of Fibrous Microplastic Pollution on Commercial Seafood and Consumer Health: A Review

The omnipresence of microfibers in marine environments has raised concerns about their availability to aquatic biota, including commercial fish species. Due to their tiny size and wide distribution, microfibers may be ingested by wild-captured pelagic or benthic fish and farmed species. Humans are exposed via seafood consumption. Despite the fact that research on the impact of microfibers on marine biota is increasing, knowledge on their role in food security and safety is limited. The present review aims to examine the current knowledge about microfiber contamination in commercially relevant fish species, their impact on the marine food chain, and their probable threat to consumer health. The available information suggests that among the marine biota, edible species are also contaminated, but there is an urgent need to standardize data collection methods to assess the extent of microfiber occurrence in seafood. In this context, natural microfibers should also be investigated. A multidisciplinary approach to the microfiber issue that recognizes the interrelationship and connection of environmental health with that of animals and humans should be used, leading to the application of strategies to reduce microfiber pollution through the control of the sources and the development of remediation technologies.

Editorial for the Special Issue “Microplastics in Aquatic Environments: Occurrence, Distribution and Effects”

The large production and widespread daily consumption of plastic materials—which began in the last century—together with the often-inadequate collection and recycling systems, have made plastics and, consequently, microplastics (MPs) ubiquitous pollutants [...]