Color preferences and gastrointestinal-tract retention times of microplastics by freshwater and marine fishes

Effect of parasitic infection on microplastic ingestion in a native leuciscid hybrid species (Alburnus derjugini x Squalius orientalis) from Kürtün Dam Lake, Türkiye

Microplastic (MP) pollution is currently one of the most serious environmental issues. MPs were investigated in the Kürtün Dam Lake in healthy individuals of the native leuciscid hybrid (Alburnus derjugini x Squalius orientalis) species and individuals infected with the Ligula intestinalis parasite. Although MP abundance appeared to be higher in non-infected fish (NIF) than in L. intestinalis (L) and infected fish (IF), the MP abundance in IF was higher, because the parasite theoretically belongs to IF. In addition to the observation of MPs in the gastrointestinal tract (GIT) of fish, the diffusion of MPs by parasites settled in the body cavity indicates that MPs are not only present in the GIT. Therefore, predation on existing fish by birds causes MP dispersion. In the present study, the most common MP shape was fiber (100% for NIF and IF, 85.7% for L), the MP color was black (57.1% for IF and L) and orange (50% for NIF), and the polymer type was polyamide (57.1% for IF, 50% for NIF) and polyethylene terephthalate (28.5% for L). These MP compositions led us to believe that textile effluents and aquaculture operations in dam lakes could be sources of pollution. Therefore, this study provides insights for future research to elucidate the connection between MP consumption and parasite infection.

Bioaccumulation of polycyclic aromatic hydrocarbons and their human health risks depend on the characteristics of microplastics in marine organisms of Sanggou Bay, China

Microplastics pose a threat to marine environments through their physical presence and as vectors of chemical pollutants. However, the impact of microplastics on the accumulation and human health risk of chemical pollutants in marine organisms remains largely unknown. In this study, we investigated the microplastics and polycyclic aromatic hydrocarbons (PAHs) pollution in marine organisms from Sanggou Bay and analyzed their correlations. Results showed that microplastic and PAHs concentration ranged from 1.23 ± 0.23 to 5.77 ± 1.10 items/g, from 6.98 ± 0.45 to 15.07 ± 1.25 μg/kg, respectively. The microplastic abundance, particularly of fibers, transparent and color plastic debris, correlates strongly with PAH contents, indicating that microplastics increase the bioaccumulation of PAHs and microplastics with these characteristics have a significant vector effect on PAHs. Although consuming seafood from Sanggou Bay induce no carcinogenic risk from PAHs, the presence of microplastics in organisms can significantly increases incremental lifetime cancer risk of PAHs. Thus, microplastics can serve as transport vectors for PAHs with implications for the potential health risks to human through consumption. This study provides new insight into the risks of microplastics in marine environments.

Effects of food quantity on the ingestion and egestion of MPs with different colors by Daphnia magna

Aquatic organism uptake and accumulate microplastics (MPs) through various pathways, with ingestion alongside food being one of the primary routes. However, the impact of food concentration on the accumulation of different types of MPs, particularly across various colors, remains largely unexplored. To address this gap, we selected Daphnia magna as a model organism to study the ingestion/egestion kinetics and the preference for different MP colors under varying concentrations of Chlorella vulgaris. Our findings revealed that as the concentration of Chlorella increased, the ingestion of MPs by D. magna initially increased and then showed a decline. During the egestion phase within clean medium without further food supply, an increase in food concentration during the ingestion phase led to a slower rate of MP discharge; while when food was present during the egestion phase, the discharge rate accelerated for all treatments, indicating the importance of food ingestion/digestion process on the MPs bioaccumulation. Furthermore, in the presence of phytoplankton, D. magna demonstrated a preference for ingesting green-colored MPs, especially at low and medium level Chlorella supply, possibly due to the enhanced food searching activities. Beyond gut passage, we also examined the attachment of MPs to the organism's body surface, finding that the number of adhered MPs increased with increasing food concentration, likely due to the intensified filtering current during food ingestion. In summary, this study demonstrated that under aquatic environment with increasing phytoplankton concentrations, the ingestion and egestion rates, color preferences, as well as surface adherence of MPs to filter feeding zooplanktons will be significantly influenced, which may further pose ecological risks. Our results offer novel insights into the unintentional accumulation of MPs by zooplankton, highlighting the complex interactions between food availability and MPs accumulation dynamics.

First report of plastic and non-plastic microparticles in stomach of slandertail lanternshark and shortspine spurdog from the edge of East China Sea

This study investigates the presence of plastic and non-plastic microparticles in the gastrointestinal tracts of two deep-sea sharks, Etmopterus molleri (n = 118) and Squalus mitsukurii (n = 6), bycatch from the East China Sea continental shelf. We found a total of 117 microparticles, predominantly fibres (67.52 %), with blue (31.62 %) and black (23.94 %) being the most prevalent colours. E. molleri contained 70 microparticles (0.63 ± 0.93 items/shark), 61.42 % non-plastics like viscose and cotton, while plastics included polyethylene, polyethylene terephthalate, and acrylic. Despite S. mitsukurii's limited sample size, the results show that it takes in a lot of microparticles (47 microparticles, 7.83 ± 2.64 items/shark), 57.44 % non-plastics (viscose, cotton, and ethyl cellulose), and 42.56 % plastics. A positive correlation between microparticle presence and total length was observed for E. molleri. These results provide initial data on microparticle ingestion by these species, highlighting potential ecological risks and trophic transfer implications in deep-sea ecosystems.

Understanding microplastic presence in different wastewater treatment processes: Removal efficiency and source identification

Municipal effluents discharged from wastewater treatment plants (WWTPs) are a considerable source of microplastics in the environment. The dynamic profiles of microplastics in treatment units in WWTPs with different treatment processes remain unclear. This study quantitatively analyzed microplastics in wastewater samples collected from different treatment units in two tertiary treatment plants with distinct processes. The influents contained an average of 15.5 ± 3.5 particles/L and 38.5 ± 2.5 particles/L in the two WWTPs with in the oxidation ditch process and the integrated fixed-film activated sludge process, respectively. Interestingly, microplastic concentrations in the influent were more influenced by the population density in the served area than sewage volume or served population equivalent. Throughout the treatment process, concentrations were reduced to 1.5 ± 0.5 particles/L and 1.0 ± 1.0 particles/L in the final effluents, representing an overall decrease of 90% and 97%, in WWTPs with the oxidation ditch process and integrated fixed-film activated sludge process, respectively. A significant proportion of the microplastics were removed during the primary treatment stage in both WWTPs, with better performance for foam, film, line-shaped and large-sized microplastics. Most microplastics were accumulated in activated sludge, indicating its key role as the primary sink in WWTPs. The multiple correspondence analysis identified laundry washing and daily necessities such as packaging and containers as the major contributors to microplastics in WWTPs. The study proposed recommendations for upgrading WWTPs, modifying designs, and implementing strategies to reduce microplastic sources, aiming to minimize the release of microplastics into the environment. These findings can shed lights on the sources of microplastics in WWTPs, and advance our understanding of the mechanisms for more effective microplastic removals in wastewater treatment technologies in future applications.

The presence and physico-chemical properties of microplastics in seawater, sediment, and several organs of the spotted scat fish (Scatophagus argus, Linnaeus, 1766) collected from different locations along the East Java coast in Indonesia

A comprehensive study was undertaken to examine the contamination of spotted scat fish (Scatophagus argus) with microplastics (MP) in various locations along the East Java coast of Indonesia. The purpose of this study was to collect detailed information regarding the abundance, color, shape, size, type of polymer, and chemical components of the MP. The findings of this study indicated that MP exhibiting distinct attributes-including a specific fiber type, black coloration, and a size range of 1000- <5000 μm-was most abundant in the gill, stomach, and intestines of spotted scat fish of varying lengths. And MP with a size range of 100-<500 μm was prevalent in the sediment. MP with black fragments measuring less than 100 μm in diameter were found primarily in seawater. A positive correlation was identified between fish length and MP abundance in the intestines, as indicated by the Spearman correlation coefficient. Conversely, a negative correlation was detected between fish length and MP abundance in the gills. The findings of the Fourier transform infrared spectroscopy and Gas chromatography-mass spectrometry analyses, which indicate the presence of various polymers and chemical substances including plasticizers (e.g., diethyl phthalate, decane, and eicosane), stabilizers (2-piperidinone, hexadecanoic acid, mesitylene, and 2,4-Di-tert-butylphenol), and flame retardant (cyclododecene), in fish, are of the utmost importance. These substances have the potential to endanger the health of both animals and humans if they are ingested through the food chain.

Towards the understanding of the uptake and depuration of microplastics in the ragworm Hediste diversicolor: Field and laboratory study

An important number of studies have evaluated the presence of microplastics, particles with a size below 5 mm, in aquatic organisms. Studies have shown that these fragments are widely present in the marine environment, but research on the estuarine ecosystem is still scarce. In this study, two different approaches were used to evaluate the presence and ingestion of plastic particles in the ragworm Hediste diversicolor: a field study for the environmental assessment and a laboratory experiment in controlled condition. For the environmental evaluation, ingestion of microplastics was evaluated in the ragworm H. diversicolor sampled from the mudflats of the Seine estuary (France) during March and June 2017 and 2018, on two locations: S1 and S2, both characterized by high anthropogenic pressures, and for S2 a more influential hydrodynamic component. Ingestion of microplastics was measured in ragworms tissues and in gut content (sediment) after depuration. The number of particles as well as their size, shape and color were reported and compared between sampling period and locations. Results showed the presence of a low number of particles in both worms and gut content. In gut content, 45.6% and 87.58% of samples from site S1 and S2 respectively contained plastic like particles. In worms, 41.7% (S1) and 75.8% (S2) of analysed samples contained plastic like items. The lowest mean number of particles was 0.21 ± 0.31 (S1 in June 2017) in worms' tissues, but 0.80 ± 0.90 (S1 in June 2017) in the gut content and the highest was 1.47 ± 1.41 (S2 in April 2017) while the highest number was 2.55 ± 2.06 (S2 in June 2017) in worms and gut content respectively. The majority of suspected microplastics observed were fibers (66%) and fragments (27%), but films (3.7%) foam (2.1%), and granules (0.2%) were also identified. In addition, the most polymer type observed by Raman spectroscopy was polypropylene. Furthermore, a preliminary study of the ingestion and egestion of fluorescent polyethylene (PE) microbeads in the digestive tract of ragworms was conducted after exposure through water, during 1h at 1.2 × 106 MP/mL. Results showed a rapid turnover of PE microbeads throughout the digestive tract of worms especially after exposure through water. This study revealed that microplastics are ingested by the ragworm H. diversicolor but do not seem to bioaccumulate. More research is needed to measure potential chronic effects of microplastics on physiological parameters of H. diversicolor and potential trophic transfer of microplastics.

Comparison of phthalate esters (PAEs) in freshwater and marine food webs: Occurrence, bioaccumulation, and trophodynamics

Phthalate esters (PAEs) have received widespread attentions due to their ubiquity in various kinds of matrices and potential biotoxicity. This study systematically compared the concentrations, bioaccumulation, trophodynamics and health risk of PAEs in 25 species (n = 225) collected from a marine (Bohai Bay, BHB) and freshwater environment (Songhua River, SHR), China. Results showed that di-(2-ethylhexyl) phthalate and di-n-butyl phthalate were the predominant PAEs in the organisms from the two aquatic environments. The total concentrations of 6 PAEs in algae and fish from SHR were significantly higher than those from BHB. Two food webs were constructed in BHB and SHR based on the abundance of 15N in the organisms. All the PAEs except dimethyl phthalate exhibited trophic dilution with the trophic magnification factors less than 1. Moreover, an obvious biodilution of PAEs was observed in marine food web compared to freshwater food web. A low health risk of PAEs was found in organisms from both BHB and SHR. However, di-(2-ethylhexyl) phthalate exhibited a potential carcinogenic risk by consumption of some benthos in BHB and fish in SHR. This study provides a valuable perspective for understanding the trophodynamics and health risk of PAEs in marine and freshwater environments.

Incidence of microplastic translocation in freshwater fish eggs

The issue of microplastic contamination in seafood is progressively recognised as a significant global issue. This study presents novel findings regarding the detection of microplastics within the eggs of commercially available fish intended for consumption by humans. Eggs of Ompok bimaculatus, Heteropneustes fossilis, Mystus vittatus and Anabas testudineus collected from the Periyar River, Kerala, India were subjected to analysis for the potential presence of microplastics. Out of the 91 fishes (containing eggs) examined, microplastics were observed in the eggs of 2 species, i.e., Ompok bimaculatus and Mystus vittatus. The polymers recorded were polyethylene and polypropylene. Fish eggs are commonly consumed by humans and are highly esteemed as a delectable food. Considering the widespread consumption of fish eggs as a delicacy among humans, there exists a potential route for human exposure to microplastics, which raises concerns regarding public health.

Microplastic pollution in wild and aquacultured Mediterranean mussels from the Sea of Marmara: Abundance, characteristics, and health risk estimations

Microplastic (MP) pollution raises urgent concerns about the environmental well-being and the safety of the food supply for humans. Mussels are essential filter-feeding organisms that may be highly susceptible to MPs uptake due to their global distribution and sedentary lifestyle. There is also a knowledge gap regarding MP levels in commercially-farmed and wild-sourced mussels for human consumption, creating gaps in risk identification for food safety. This study aims to fill this gap in understanding by (a) investigating the presence and abundance of MPs in both wild and aquacultured mussels collected from six different stations in the Sea of Marmara, (b) comparing the levels of MPs between aquacultured and wild mussels, and (c) evaluating the potential health risks associated with the consumption of these contaminated mussels. Polymer types were verified by ATR-FTIR (Attenuated Total Reflectance Fourier Transform- Infrared Spectroscopy), and 6 different polymers have been identified. Among the total 753 identified MPs, the majority (79.8%) were fibers, with the predominant size range (42.4%) falling between 0.1 and 0.5 mm. Consuming wild mussels was associated with a 187.6% higher risk of MP intake compared to aquaculture. A consumer can potentially be exposed to 133.11 to 844.86 MP particles when consuming a 100 g serving of mussels, with risks becoming more significant as portion sizes increase, as is the case in some countries where portions reach 225 g. In this study, detailed information is presented on MP pollution in both wild and aquacultured mussels from Sea of Marmara, providing valuable insights for ensuring food safety, effective management and control of MP pollution in this region.

Microplastics in mangroves with special reference to Asia: Occurrence, distribution, bioaccumulation and remediation options

Microplastics (MPs) are a new and lesser-known pollutant that has intrigued the interest of scientists all over the world in recent decades. MP (<5mm in size) can enter marine environments such as mangrove forests in a variety of ways, interfering with the health of the environment and organisms. Mangroves are now getting increasingly exposed to microplastic contamination due to their proximity to human activities and their position as critical transitional zones between land and sea. The present study reviews the status of MPs contamination specifically in mangrove ecosystems situated in Asia. Different sources and characteristics of MPs, subsequent deposition of MPs in mangrove water and sediments, bioaccumulation in different organisms are discussed in this context. MP concentrations in sediments and organisms were higher in mangrove forests exposed to fishing, coastal tourism, urban, and industrial wastewater than in pristine areas. The distribution of MPs varies from organism to organism in mangrove ecosystems, and is significantly influenced by their morphometric characteristics, feeding habits, dwelling environment etc. Mangrove plants can accumulate microplastics in their roots, stem and leaves through absorption, adsorption and entrapment helping in reducing abundance of microplastic in the surrounding environment. Several bacterial and fungal species are reported from these mangrove ecosystems, which are capable of degrading MPs. The bioremediation potential of mangrove plants offers an innovative and sustainable approach to mitigate microplastic pollution. Diverse mechanisms of MP biodegradation by mangrove dwelling organisms are discussed in this context. Biotechnological applications can be utilized to explore the genetic potential of the floral and faunal species found in the Asian mangroves. Detailed studies are required to monitor, control, and evaluate MP pollution in sediments and various organisms in mangrove ecosystems in Asia as well as in other parts of the world.

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.

Diel Pattern of Microplastic Residues in Zebrafish

As one of the emerging pollutants, microplastics (MPs) can be taken up by aquatic organisms through ingestion. However, little is known about the uptake pattern in organisms over time and the associated mechanisms of retention patterns. The present study aims to elucidate these patterns in fish, their relationship with light/dark conditions, and examine the uptake kinetic process of small-sized plastic pollutants, especially during the long-neglected dark period. Zebrafish were sampled every 2 h during the light and dark periods after exposure to an environmentally relevant concentration (100 items/L) of MPs. The results demonstrated that MP residues in zebrafish decreased during the dark period rather than increased over time. The MP retention rhythm and the swimming behavior of exposed zebrafish displayed a statistically significant light/dark variation. Moreover, a very strong and statistically significant positive correlation was found between the swimming speed of zebrafish and the number of MP residues in the gastrointestinal tracts of zebrafish. These results clearly demonstrate that fibrous MP residues in the fish have a discernible diel pattern. This work improves the understanding of the dynamic residual process of MPs in organisms and calls for further in-depth circadian toxicokinetic studies to better suit particle pollutants.

Microplastic abundance in urban vs. peri-urban mangroves: The feasibility of using invertebrates as biomonitors of microplastic pollution in two mangrove dominated estuaries of southern Africa

Microplastic (MP) prevalence has been well documented, however, knowledge gaps exist for African mangrove forests. This research is the first to compare MP pollution (using FT-IR analysis) in an urban (Durban Bay) and peri-urban (Mngazana Estuary) mangrove forest in South Africa, across different compartments. MP pollution (typology, abundance, and distribution) was quantified in estuarine surface water, sediment and the soft tissue of three keystone species (Austruca occidentalis, Chiromantes eulimene and Cerithidea decollata) in relation to disturbances acting on these systems. MP averages ranged from 99 to 82 MPs/kg sediment, 177 to 76 MPs/L water and 82 to 59 MP/g-1 DW in biota. Overall fibres were the dominant MP type across all compartments. The three invertebrate species exhibited MP bioaccumulation, however, significant differences were observed between MP concentrations in the soft body tissue of invertebrates and abiotic compartments, providing evidence that they are not effective biomonitors of MP pollution.

Stealth microplastics pollutants: Toxicological evaluation of polyethylene terephthalate-based glitters on the microalga Desmodesmus sp. and its color effect

Polyethylene terephthalate-based glitters (PET glitters) are a potential source of primary microplastics in the environment. However, the bioeffects of PET glitters and the associated leachates remain largely unknown. In this study, we investigated the individual and combined toxicity of five colors (silver, black, red, green, and blue) of PET glitters and their corresponding leachates on the cellular responses of Desmodesmus sp. The results indicated that the photosynthesis of Desmodesmus sp. could be partly affected by PET glitters through the shading effect, but not that of growth. Conversely, the leachates of red and green PET glitters significantly inhibited the growth of the microalga, suggesting a higher risk associated with additives leached from these colors of PET glitters. Furthermore, the adverse effects of the co-occurrence of PET glitters and leachates were closely related to oxidative stress responses in the microalgal cells, along with a color effect, which could be mainly attributed to variations in the composition and abundance of toxic additives in different colors of PET glitters. Overall, our findings provide insights into the ecological risks posed by glitters in aquatic environments and emphasize the importance of considering color factors in assessing microplastics toxicity.

First record of plastic ingestion by a freshwater stingray

The abundance and dispersion of plastic particles in aquatic ecosystems has become pervasive resulting in the incorporation of these materials into food webs. Here we describe the first record of plastic ingestion by the freshwater white-blotched river stingray Potamotrygon leopoldi (Potamotrygonidae), an endemic and threatened species in the Xingu River, Amazon basin. Potamotrygonidae stingrays inhabit exclusively Neotropical rivers, occupying rocky substrate habitats and feeding mainly on benthic macroinvertebrates. The gastrointestinal tract of 24 stingrays were analyzed, 16 (66.6 %) of which contained plastic particles. In total, 81 plastic particles were recorded and consisted of microplastics (< 5 mm, n = 57) and mesoplastics (5-25 mm, n = 24). The plastic particles found were classified into fibers (64.2 %, n = 52) and fragments (35.8 %, n = 29). The predominant color was blue (33.3 %, n = 27), followed by yellow (18.5 %, n = 15), white (14.8 %, n = 12), black (13.6 %, n = 11), green (6.2 %, n = 5), transparent (4.9 %, n = 4), pink, grey and brown (2.5 %, n = 2, each) and orange (1.2 %, n = 1). No significant correlation was observed between the number of plastic particles and the body size. Eight types of polymers were identified in the plastic particles analyzed using 2D FTIR Imaging. The most frequent polymer was artificial cellulose fiber. This is the first report of plastic ingestion by freshwater elasmobranchs in the world. Plastic waste has become an emerging problem in aquatic ecosystems globally and our results provide an important datapoint for freshwater stingrays in the Neotropics.

Seasonal monitoring of microplastic pollution in the Southeast Black Sea: An example of red mullet (Mullus barbatus) gastrointestinal tracts

This study investigated seasonal presence of microplastic (MP) in gastrointestinal tracts of red mullet (Mullus barbatus) sampled from the Southeast Black Sea Region. A total of 335 MPs were detected in 120 individuals. While the most MP was observed in the winter and autumn seasons, quite few MPs were found in the summer and spring seasons. MP size did not show significant difference among seasons. While all of the MPs in the autumn and spring and most of the MPs in the winter were fiber-shaped, most of the MPs in the summer were fragments. The most observed MP color for all seasons was white. While polymer structures did not show much variation in spring and summer, six different polymers were determined for both autumn and winter. In general, less MPs were detected during fishing ban period (summer) and the characteristic properties of the detected MPs suggest a MP pollution in the region due to intense fishing activities.

First account of microplastics in pelagic sporting dolphinfish from the eastern Mexican coast of Baja California Sur

This study is a baseline data on the presence of MPs from the gastro-intestinal tracts (GITs) in Coryphaena hippurus Linnaeus, from eastern Baja California Sur, México. 878 MPs items (in %) of fibers (29%), fragments (68%) and films (1.3%) were detected from 51 GITs of Coryphaena hippurus. Transparent, white, blue and black were the prevalent colours. Morphological features observed through SEM analysis, the presence of heavily weathered MPs is due to the mechanical, microbiological and chemical weathering process. PP (29%), Nylon (29%), PS (17%), PE (11%), PET (6%) and HDPE (8%) presence indicates their source from regional anthropogenic stress. Trophic level transition is enforced by polymer derivative, permitting the sinking behavior of MPs and increased ingestion probability. Fishes were classified as slim despite their higher feeding capabilities and ingested MPs indicates a relationship with environmental contaminants. Current study emphasizes the health risk linked to biological aspects of MPs ingestion.

Microplastic occurrence and ecological risk assessment in the eight outlets of the Pearl River Estuary, a new insight into the riverine microplastic input to the northern South China Sea

Estuaries are unique transition zones connecting terrestrial and coastal environments and are recognized as primary conveyors for land-derived plastics to open oceans. Riverine microplastics (MPs) have been commonly investigated using sequential sampling which might not effectively reflect the actual load. In this study, sampling at eight outlets was performed during a complete tidal cycle to estimate the MP flux to the Pearl River Estuarine (PRE) using a concurrent sampling strategy. The MP abundances ranged from 2.90 ± 0.57-5.9 ± 2.27 particles/L. A remarkable difference between tides in MP abundances suggests tidal effect should not be overlooked in assessment. The MP load through the eight outlets was estimated at 304 trillion particles or 1102 tons into the PRE annually. Additionally, similar potential ecological risk assessment among eight rivers implied that environmental threats posed by less urbanized and populated rural areas on the western side have been under-evaluating for decades.

Euryhaline fish larvae ingest more microplastic particles in seawater than in freshwater

Microplastic (MP) pollution is a major concern in aquatic environments. Many studies have detected MPs in fishes; however, little is known about differences of microplastic uptake by fish in freshwater (FW) and those in seawater (SW), although physiological conditions of fish differ significantly in the two media. In this study, we exposed larvae (21 days post-hatching) of Oryzias javanicus (euryhaline SW) and Oryzias latipes (euryhaline FW), to 1-µm polystyrene microspheres in SW and FW for 1, 3, or 7 days, after which, microscopic observation was conducted. MPs were detected in the gastrointestinal tracts in both FW and SW groups, and MP numbers were higher in the SW group in both species. Vertical distribution of MPs in the water, and body sizes of both species exhibited no significant difference between SW and FW. Detection of water containing a fluorescent dye revealed that O. javanicus larvae swallowed more water in SW than in FW, as has also been reported for O. latipes. Therefore, MPs are thought to be ingested with water for osmoregulation. These results imply that SW fish ingest more MPs than FW fish when exposed to the same concentration of MPs.

Decade of microplastic alteration in the southeastern black sea: An example of seahorse gastrointestinal tracts

Unconscious and excessive use of plastic supports the diversity and abundance of microplastics (MPs) in marine environments. As a result of MP exposure, organisms in the marine environment are faced with adverse scenarios up to death. In this study, ten-year MP composition was investigated in gastrointestinal tracts (GITs) of low-mobility seahorses (90 individuals per period) from the Southeastern Black Sea. Seahorse GITs sampled during both 2012 and 2022 contain 102 and 135 MP items, respectively. The number of MPs per unit individual seahorse and unit seahorse weight was higher in the 2022 period. On the other hands, no significant differences were observed between the MP lengths of both periods. The majority of MPs in both sample periods were materials shorter than 1000 μm. Of the eight found synthetic polymers, five belonged to the 2012 period, while seven were observed during the 2022 period. Additionally, the most abundant synthetic polymer for both periods is polyvinyl stearate (PVS). As a result, 43% of the total plastic material belonged to the 2012 period, while 57% was observed in the 2022 period. Considering both the diversity of polymers and the abundance of plastics, the region was adversely affected by plastic materials in the 2022 period.

Microplastics pollution in freshwater sediments: The pollution status assessment and sustainable management measures

Microplastics (MPs) pollution in freshwater sediments has brought hidden dangers to food and drinking water supply. Implementing sustainable management measures for MPs pollution in freshwater sediments has become an inevitable trend for sustainable development of society. Existing studies still lacked sufficient discussion in sustainable management of MPs pollution in freshwater sediments. This makes it difficult to formulate sustainable management measures for MPs pollution in freshwater sediments. This study analyzed the pollution status of MPs in freshwater sediments from 84 study areas. The results showed that current studies on MPs pollution in freshwater sediments were mainly concentrated in densely populated and economically developed areas. The average abundance of MPs in freshwater sediments from collected study areas was 1290.88 items/kg, this brought a potential threat to sustainable development in surrounding areas. The pollution load level and potential ecological risk level of MPs in freshwater sediments from these study areas were low. Reducing MPs discharge and restricting the use of high-risk polymers are effective ways to prevent the deterioration of MPs pollution status in freshwater sediments. The abundance and types of MPs in freshwater sediments from these study areas were affected by human activities. Sustainable management of MPs pollution in freshwater sediments from collected study areas requires establishing a lifecycle management system for plastic products, and the industrial structures should be optimized. In addition, legislation and market regulation are effective ways to restrict the discharge of plastic wastes. Sustainable management of MPs in freshwater sediments requires the synergy of legislation and market regulation.

The sustainable management of microplastics pollution in sediments from China: Promulgating relevant laws and implementing targeted management

Microplastics (MPs) pollution in sediments brings a huge challenge to the sustainable development of society. China is one of the countries with the largest production and application of plastic products in the world. The sustainable management of MPs pollution in sediments from China has important implications for achieving the United Nations Sustainable Development Goals. There is a lack of targeted management measures for the sustainable management of MPs pollution in sediments from China. In this study, 74 study areas were collected to analyze the pollution status of MPs in sediments from China. The results showed that the study on MPs pollution in sediments from China was concentrated in the Bohai Rim Economic Circle (n = 12), the Yangtze River Delta Economic Circle (n = 16) and the Pearl River Delta Economic Circle (n = 13). And the average abundance of MPs in sediments from China showed a decreasing trend from coastal to inland. Fiber had the highest centrality degree in the correlation network of MPs types. The reduction of fiber in sediments can reduce the diversity of MPs in sediments from China. Population density, economic level, urbanization level and industrial structure were significantly correlated with MPs types in sediments from China. The targeted management measures can be formulated based on the contribution of different human activities to MPs types. Managing pollution sources and cutting off transmission pathways are effective means for the targeted management of MPs in sediments. In addition, legislation can effectively restrict the application of plastic products. Promulgating relevant laws and implementing targeted management are conducive to the sustainable management of MPs pollution in sediments from China. In future studies, a big data platform for MPs pollution should be established to obtain a comprehensive understanding in the pollution status of MPs in sediments from China.

Microplastics accumulation in gastrointestinal tracts of Mullus barbatus and Merluccius merluccius is associated with increased cytokine production and signaling

There is clear evidence that different marine species can be impacted by microplastic (MP) ingestion accumulating such MPs mainly in the gastrointestinal tract. However, there is still limited knowledge on the consequences of MPs' accumulation in the gut. The present study aims to assess MPs and their potential immunotoxic effects in the digestive tract of two species showing different ecological traits: the red mullet (Mullus barbatus) and the European hake (Merluccius merluccius). Infrared spectroscopy (FTIR-ATR), micro-Raman and electron scanning microscope (SEM) were used to accurately identify the main plastic polymers detected in gut contents. In addition, we investigated the association between MP uptake and intestinal inflammation by evaluating expression and secretion of proinflammatory cytokines. MP abundance ranged from 1 to 20 items/individual in red mullet and from 2 to 15 items/individual in European hake. The majority of ingested MPs were fibers, while the dominant colors were black and blue in both species. Chemical characterization indicated polyethylene and polypropylene as the most common polymer types. Moreover, it was observed that MP abundance was highly positive correlated to cytokines (i.e. interleukin-1β, 10, and interferon) and antioxidant enzyme (i.e. catalase and superoxide dismutase) transcript levels suggesting ROS generation and an infiltration of immune cells in the gut. Our findings provide evidence that the induction of cytokine-dependent signaling pathways is one aspect of the complex mechanism by which MPs affect the gut system in fish.