Assessment of microplastics derived from mariculture in Xiangshan Bay, China

Occurrence of microplastics and metals in European seabass produced in different aquaculture systems: Implications for human exposure, risk, and food safety

Microplastics (MPs) are emerging contaminants of increasing concern as they may cause adverse effects and carry other contaminants, which may potentially compromise human health. Despite occurring in aquatic ecosystems worldwide, the knowledge about MP presence in different aquaculture systems and their potential impact on seafood products is still limited. This study aimed to determine the levels of MPs in water, feed, and European seabass (Dicentrarchus labrax) from three relevant aquaculture systems and estimate human exposure to MPs and metals through seabass consumption. The recirculating aquaculture system (RAS) had the highest MP occurrence in water and feed. MP levels in seabass followed the aquaculture system's levels in water and feed, with RAS-farmed fish presenting the highest MP load, both in the fish gastrointestinal tract (GIT) and muscle, followed by pond-, and cage-farmed fish. MPs' characteristics across aquaculture systems and fish samples remained consistent, with the predominant recovered particles falling within the MP size range. The particles were visually characterized and chemically identified by micro-Fourier Transform Infrared Spectroscopy (μFTIR). Most of these particles were fibres composed of man-made cellulose and PET. MP levels in GIT were significantly higher than in muscle for pond- and RAS-farmed fish, MPs' bioconcentration factors >1 indicated bioconcentration in farmed seabass. Metal concentrations in fish muscle were below permissible limits, posing low intake risks for consumers according to the available health-based guidance values and estimated dietary scenarios.

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

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

Potential threats of microplastics and pathogenic bacteria to the immune system of the mussels Mytilus galloprovincialis

As one of the main components of marine pollution, microplastics (MPs) inevitably enter the mussel aquaculture environment. At the same time, pathogenic bacteria, especially pathogens such as Vibrio, can cause illness outbreaks, leading to large-scale death of mussels. The potential harm of MPs and pathogenic bacteria to bivalve remains unclear. This study designed two experiments (1) mussels (Mytilus galloprovincialis) were exposed to 100 particles/L or 1,000 particles/L polymethyl methacrylate (PMMA, 17.01 ± 6.74 μm) MPs and 1 × 107 CFU/mL Vibrio parahaemolyticus at the same time (14 days), and (2) mussels were exposed to 100 particles/L or 1,000 particles/L MPs for a long time (30 days) and then exposed to 1 × 107 CFU/mL V. parahaemolyticus to explore the effects of these two stresses on the mussel immune system. The results showed that after the combined exposure of V. parahaemolyticus and MPs, the lysosomal membrane stability of hemocytes decreased, lysozyme activity was inhibited, and hemocytes were induced to produce more lectins and defensins to fight pathogenic invasion. Long-term exposure to MPs caused a large amount of energy consumption in mussels, inhibited most of the functions of humoral immunity, increased the risk of mussel infection with pathogenic bacteria, and negatively affected mussel condition factor, the number of hemocytes, and the number of byssuses. Mussels may allocate more energy to deal with MPs and pathogenic bacterial infections rather than for growth. Above all, MPs exposure can affect mussel immune function or reduce its stress resistance, which in turn has an impact on mollusk farming.

Occurrence, distribution and sources of microplastics in typical marine recirculating aquaculture system (RAS) in China: The critical role of RAS operating time and microfilter

Industrial mariculture, a vital means of providing high quality protein to humans, is a potential source of microplastics (MPs) which have recently received increasing attention. This study investigated the occurrence and distribution of microplastics in feed, source water and recirculating aquaculture system (RAS) with long & short operating times as well as in fish from typical industrial mariculture farms in China. Results showed that microplastics occurred in all samples with the average concentration of 3.53 ± 1.39 particles/g, 0.70 ± 0.17 particles/L, 1.53 ± 0.21 particles/L and 2.21 ± 0.62 particles/individual for feed, source water, RAS and fish, respectively. Microplastics were mainly fiber in shape, blue in color and 20-500 μm in size. Compared with short operated RAS, long operating time led to higher microplastic concentration in RAS, especially that of microplastic in 20-500 μm, granular and blue. Regardless of short or long operating time, microplastics in RAS mainly gathered in culture tank, tank before microfilter and fixed-bed biological filter, and the microfilter removed efficiently the microplastic with the shape of film, granule, fragment as well as those with size > 1000 μm. As for the polymer types, polyamide (PA, 71.9 %) and polyethylene terephthalate (PET, 65.7 %) dominated in feed and source water, respectively, which may be the reason for the high proportion of PA (38.8 % and 26.4 %) and PET (31.8 % and 30.2 %) in RAS and fish. In addition, polypropylene (PP) was also detected in RAS (18.7 %) and fish (22.6 %), indicating that other plastic facilities such as PP brush carrier also made a contribution. Positive matrix factorization (PMF) model revealed three sources of MP in RAS, namely plastic facilities, industrial sewage and plastic packaging products. Our results provided a theoretical basis for the management of MP in RAS.

High-sensitive determination of tetracycline antibiotics adsorbed on microplastics in mariculture water using pre-COF/monolith composite-based in-tube solid phase microextraction on-line coupled to HPLC-MS/MS

Microplastics (MPs) act as carriers for organic pollutants (e.g. antibiotics) and microorganisms (e.g. bacteria) in waters, leading to the proliferation of antibiotic resistance genes. Moreover, the antibiotics adsorbed on MPs may exacerbate this process. For further research, it is necessary to understand the types and amounts of antibiotics adsorbed on MPs. However, due to the heavy work of MPs collection and sample pretreatment, there is a lack of analytical methods and relevant data. In this study, an in-tube solid phase microextraction (IT-SPME) on-line coupled to HPLC-MS/MS method based on amorphous precursor polymer of three-dimensional covalent organic frameworks/monolith-based composite adsorbent was developed, which could efficiently capture, enrich and analyze tetracycline (TCs) antibiotics. Under the optimal extraction parameters, the developed method was capable of detecting TCs at levels as low as 0.48-1.76 pg. This method was applied to analyze the TCs adsorbed on MPs of different particle sizes in mariculture water for the first time, requiring a minimum amount of MPs of only 1 mg. Furthermore, it was observed that there could be an antagonistic relationship between algal biofilm and TCs loaded on MPs. This approach could open up new possibilities for analyzing pollutants on MPs and support deeper research on MPs.

Microplastic pollution: a review of techniques to identify microplastics and their threats to the aquatic ecosystem

Microplastics (MPs), small synthetic particles, have emerged as perilous chemical pollutants in aquatic habitats, causing grave concerns about their disruptive effects on ecosystems. The fauna and flora inhabiting these specific environments consume these MPs, unwittingly introducing them into the intricate web of the food chain. In this comprehensive evaluation, the current methods of identifying MPs are amalgamated and their profound impacts on marine and freshwater ecosystems are discussed. There are many potential risks associated with MPs, including the dangers of ingestion and entanglement, as well as internal injuries and digestive obstructions, both marine and freshwater organisms. In this review, the merits and limitations of diverse identification techniques are discussed, including spanning chemical analysis, thermal identification, and spectroscopic imaging such as Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and fluorescent microscopy. Additionally, it discusses the prevalence of MPs, the factors that affect their release into aquatic ecosystems, as well as their plausible impact on various aquatic ecosystems. Considering these disconcerting findings, it is imperative that appropriate measures should be taken to assess the potential risks of MP pollution, protect aquatic life and human health, and foster sustainable development.

Fifty-year pollution history of microplastics and influencing factors in offshore sediments: A case study of Ningbo, China

Sediment cores are optimal mediums for investigating the historical presence of offshore microplastics (MPs). In this study, two sediment cores were collected at varying water depths, i.e., XS2 (10 m) and XS3 (20 m), from the Xiangshan offshore (XSO) in Ningbo. We focused on the spatiotemporal distribution characteristics of MPs within two sediment cores and explored the response differences of MPs abundance to natural factors and human activities. The results showed that the MPs abundance in sediments has gradually increased since the late 1960s, but with interannual fluctuations. MPs abundance in XS2 and XS3 were 1133-8700 and 633-11433 items/kg dry weight, respectively. The predominant polymers were PA, PU, PET and ACR, with fragmented particles being the most prevalent shape of MPs. The MPs abundance in XS2 and XS3 had a similar response to natural factors, mainly including (i) MPs abundance significantly correlated with the sediment load of the Qiantang River (p < 0.01), indicating that sediment load might be an important factor affecting the MPs abundance and that MPs transported by rivers had characteristics of near-source sedimentation; (ii) typhoons had the effect of weakening the MPs abundance; and (iii) geological activities might be potential contributing factors to variations in MPs' abundance in deep sediments. Correlation analyses demonstrated that MPs in XSO was the result of multiple sources, stemming from plastic production, sewage discharge, marine fisheries and shipping activities. Notably, XS3 exhibited higher sensitivity to human activities compared to XS2, owing to differences in sampling locations. This study underscores the significance of employing two sediment cores, rather than a single core, as it provides a more comprehensive insight into the overarching trends and disparities in the historical pollution of MPs. Our findings contribute to a deeper understanding of the history of offshore MPs pollution, shedding new light on this critical environmental issue.

Microplastic pollution and ecological risk assessment of Yueqing Bay affected by intensive human activities

Microplastics (MPs) are a widespread environmental problem posing ecological risks in the ocean. We investigated the abundance, spatial distribution, characteristics and ecological risks of MPs in surface seawater, sediments and organisms in Yueqing Bay, China. MPs were detected in both environmental media and organisms. The overall abundance (0.24 items/m3 seawater, 6.13 items/kg dry sediment, 0.77 items/individual in organisms) was low to medium compared with other coastal areas. The MPs were mainly derived from the high-intensity mariculture and shipping in the bay, as well as industrial and human activities along the surrounding coast. The abundance of MPs in water of the left (western) bay (0.39 items/m3) was considerably higher than that of the right (north-eastern) bay (0.07 items/m3) due to the different levels of population and economic development on the left and right coasts. The ecological risk assessment showed generally low to medium risk from MPs pollution in Yueqing Bay, with higher ecological risk index (H) and potential ecological hazards (RI) of MPs polymers in water samples. These data emphasize the need for timely and effective action to reduce the contribution of intensive human activities to MPs pollution and provide information for further ecotoxicological studies, pollution control, and policy development of MPs.

Microplastic particles in river sediments and water of southwestern Nigeria: insights on the occurrence, seasonal distribution, composition, and source apportionment

Microplastics (MPs) are globally recognized as an emerging environmental threat, particularly in the aquatic environment. This study presents baseline data on the occurrence and distribution of MPs in sediments and surface water of major rivers in southwestern Nigeria. Microplastics were extracted by density separation and polymer identification using Fourier transformed infrared spectroscopy in attenuated total reflectance mode (FTIR-ATR). The abundance of MPs in surface sediment and water samples across all locations ranged from 12.82 to 22.90 particle/kg dw and 6.71 to 17.12 particle/L during the dry season and 5.69 to 14.38 particle/kg dw and 12.41 to 22.73 particle/L during the wet season, respectively. On average, fiber constituted the highest percentage of MP in sediments (71%) and water (67%) while foam accounted for the lowest values of 0.6% and 1.7%, respectively. Polypropylene (PP) and polyethylene (PE) were the main MPs across all locations based on Fourier transform infrared spectroscopy (FTIR). MPs of size < 1 mm were the most abundant (≥ 55%) on average in both water and sediments. The study identified run-off from human activities and industrial wastewater as potential sources of MP exposure based on positive matrix factorization. The study suggests assessing the impact of different land-use activities on MPs occurrence and distribution in addition to quantifying MPs in seafood as a way forward in food safety management systems for further studies. This study confirmed the occurrence and widespread distribution of MPs in surface water and sediments and provides a database on MP pollution in Nigeria.

Urban tropical freshwater ponds as microplastics hotspots-insight on abundance and characteristics using an improved sampling technique

This study elucidates the distribution and characteristics of microplastics (MPs) in 20 tropical freshwater ponds, located in the urban settlement of Raipur city in state of Chhattisgarh, India. The ponds were divided into 4 groups based on the habitat types to understand the influence of land use patterns and human activity on the distribution of MPs. Here, we provide an improved sampling technique that is economical, traditional, indigenous, independent of vessels or structures, and replicable for smaller waterbodies. The efficiency of the proposed method is closer to the traditional boat-based net sampling technique. MPs are ubiquitous in surface water samples of all 20 ponds. The average abundance of MPs was 2.52 ± 1.28 particles/L for bucket samples and 2.93 ± 1.34 particles/L for net samples. Among extracted MPs, fragments, films, and foams were dominant. MPs within size class 1 mm to 500 μm were prevailing for both bucket samples and tube-net samples. Color-wise, white/transparent and black MPs were abundant in both types of samples while the majority of MPs were polyethylene and polystyrene. The tube-net sampling method is economical and replicable and provides comparable results. This can help study MPs distribution in smaller inland waterbodies where boats and structures are not readily available to conduct net sampling. We provide the first insight into the distribution of MPs in urban ponds, and the results can be used to determine the ubiquity of MPs in urban ponds located in different regions of the subcontinent.

Microplastic contamination in water and sediments of Mahanadi River, India: An assessment of ecological risk along rural-urban area

Worldwide, environmental concerns about MPs pollution have increased. Microplastic contamination that pollutes the ocean is mostly caused by terrestrial transfer from close proximity locations. A study of MPs pollution near coastal locations becomes necessary to address the MPs transit, fate, and mitigation. In the current study MPs pollution in the surface water and sediment of the Mahanadi River estuary was assessed during Pre-MS and MS. The size, shape, and colour of the MPs were determined using a stereomicroscope, and the MPs polymer composition was identified by Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopy. The mean concentration of MPs that were potentially discovered in water was 16.6 ± 5.2 and sediments 197.3 ± 5.4 during Pre-MS. In the MS observed mean abundance of MPs was 15.1 ± 5.4 in water and 164.6 ± 76.9 in sediments. The highest abundant size was smaller than 1 mm; the most prevalent shape were fibers followed by film and fragments; black and white was a prominent colour in water and sediments respectively. Polyesters (PEs), polyethylene (PE), polyvinyl chloride (PVC), polypropylene (PP), polyamide (PA), Polystyrene (PS), and Polycarbonates (PC) were found in the analysis of the chemical composition of MPs in water and sediments samples. The calculated PLI value shows pollution load at category I, with polymer hazard levels at categories III, IV, and V, indicating very high risk. The current research results show that river inflows and fishing-related actions are probably the main causes of MPs pollution.

Spatial distribution characteristics of microplastics in the seawater column and sediments of the artificial reef area and adjacent water in Haizhou Bay

Recently, scholars have been increasing concerned about microplastics (MPs). Unfortunately, information is lacking on the spatial distribution patterns of MPs in coastal seas; therefore, our understanding of the extent of offshore MP contamination remains incomplete. MP distribution in the seawater and surface sediments of an aquaculture area (AA), artificial reef area (AR), and comprehensive effect area (CEA) in Haizhou Bay were investigated in this study. The results showed that the mean abundances of MPs in the surface, middle and bottom seawater were 6.98 ± 3.01 n/m3, 9.12 ± 3.07 n/m3 and 10.20 ± 2.41 n/m3, respectively, and that the abundance in the sediment was 3.09 ± 1.16 n/g. The MP abundance in the bottom seawater was significantly higher than that in the surface seawater (P < 0.05). The correlation among MPs at different depths was not significant, but MPs in most habitats showed a significant correlation. We discovered a significant correlation between the abundance of MPs in the CEA seawater and AR sediments, but not between that in the CEA sediments and AR sediments. MPs can be transported from surface seawater to deeper layers by natural deposition processes. The horizontal transport of MPs due to the coastal gulf current and regular semidiurnal tides lead to the correlations observed in of MP abundance among the AA, CEA, and AR. Migration of MPs from the CEA to the AR was primarily caused by the southern eddies in Haizhou Bay, while migration of MPs from the sediment to the seawater could be due to upwelling in the AR. This was also the main reason there was a lack of a correlation between the sediment from the AR and the seawater from the CEA. This work provides a theoretical and empirical foundation for MP transport and source tracking.

Are microplastics in aquaculture an undeniable driver in accelerating the spread of antibiotic resistance genes?

Aquaculture products have been a key source of protein in the human food supply. Contamination by microplastics and antibiotic resistance genes (ARGs) directly affects food quality and safety. Plastic fishing gear and the long-term misuse of antibiotics result in the persistent residue, migration, and spread of microplastics and ARGs in the aquaculture environment, causing in ecological imbalance and endangering human security. Microplastics can act as "petri dishes" for the reproduction, communication, and spread of ARGs, which adds an additional layer of complexity to the global issues surrounding microplastics and ARGs. Aquaculture has become an important source of microplastics and ARGs in natural waters. Accordingly, this paper mainly discusses the contribution of aquaculture to the presence of microplastics and ARGs in aquatic ecosystems. Microplastics and ARGs can (1) affect the production and quality of aquatic products; (2) influence the development and reproduction of aquatic organisms; and (3) accelerate the spread of resistant bacteria. How to eliminate microplastics and ARGs and block their transmission has become a worldwide problem. Actually, further research is required to understand the scale and scope of these effects.

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

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

Anthropogenic As pollution mediated by submarine groundwater discharge in a marine ranch

Arsenic (As) pollution, is a global problem, threatening human health and ecological security, especially in the bay environment with dense population and human activities. Among potential pathways of As into the bay, submarine groundwater discharge (SGD) has not received adequate attention due to its invisibility. We determined As and 222Rn activity concentrations in different water mass. Spatial variation of dissolved As concentration in the groundwater was large and attributed to the adjacent local industries. By combining 222Rn mass balance modeling with As concentrations measured, the SGD-derived As fluxes was conservatively estimated to be 1310 kg As d-1 and 5880 kg As d-1 in the dry and wet seasons, respectively. The migration of arsenic may be enhanced by rainfall and dissolved carbon. The amount of SGD derived As input to the bay was greater than the total combined As input from river discharge, atmosphere, sewage drainage, and diffusion from sediment.

Distribution Characteristics of Microplastics in Surface Seawater off the Yangtze River Estuary Section and Analysis of Ecological Risk Assessment

Microplastics are widespread in the oceans as a new type of pollutant. Due to the special geographical environment characteristics, the Yangtze River estuary region become hotspot for microplastics research. In 2017 and 2019, surface seawater microplastics samples were collected from five stations off the Yangtze River estuary during four seasons (spring, summer, autumn, and winter). The abundance and characteristics of microplastics in seawater were researched. The results showed that microplastics widely existed in surface seawater; the average abundance of microplastics in seawater was (0.17 ± 0.14) items/m3 (0.00561 ± 0.00462) mg/m3; and accounting for 80% of the total plastic debris, the abundance of microplastics was at moderately low levels compared to national and international studies. The particle size of most microplastics was between 1 mm to 2 mm, accounting for 36.1% of the total microplastics. The main shapes of microplastics were fiber, flake, and line, accounting for 39.5%, 28.4%, and 20.8%, respectively. Polypropylene, polyethylene terephthalate, and polyethylene were the main components of microplastics, accounting for 41.0%, 25.1%, and 24.9%, respectively. Yellow, green, black, and transparent were the most common colors, accounting for 21.9%, 19.6%, 16.5%, and 15.7%, respectively. This study shows that the spatial distribution of microplastics in the surface waters off the Yangtze River estuary shows a decreasing trend from nearshore to farshore due to the influence of land-based inputs, hydrodynamics, and human activities; the distribution of microplastics has obvious seasonal changes, and the level of microplastic pollution is higher in summer. The potential ecological risk of microplastics in the surface waters off the Yangtze River estuary is relatively small.

Vertical distribution of microplastics in a river water column using an innovative sampling method

Due to limitations of sampling methods, subsurface water is usually a less well-investigated compartment of the water column when scientists assess microplastic contamination. In this study, microplastic (MP) contamination was assessed in a freshwater river both in surface and subsurface using an innovative sampling method. Microplastic contamination in the lower part of the water column, i.e., near-bottom water and in sediments, was also studied. Three sampling campaigns were carried out during different weather conditions: stormy, rainy, and dry in order to observe their influence on the microplastics vertical distribution. No significant difference was observed between the abundance and types of MPs in surface and subsurface water. The proportion of polymer with theoretical density < 1 (polypropylene d = 0.9, polyethylene d = 0.91-0.95) and polystyrene (d = 0.1-1.06) in the surface and subsurface samples was 73.5%, and this proportion drops to 40.8% for the samples located in the near-bottom water and the sediments. Our results indicate that the MP concentration of the different compartments analyzed can be significantly influenced by rainfall during and prior to the sampling day. This study highlights that in shallow rivers, surface water sampling is representative of the water column MP contamination, but that sampling without taking environmental conditions into account may lead to erroneous estimation of MPs concentration and flux entering the marine environment.

Impacts of shipyard oil leakage on the PAHs and PCBs occurrence in Xiangshan Bay, China

Here, we studied the shipyard impacts on the distribution of PAHs and PCBs in the semi-enclosed Xiangshan Bay, an important mariculture zone in China. The results showed that the shipyard caused a pollution plume for PAHs but not for PCBs. As characteristic pollutants of oil leakage, the PAHs had concentrations of up to 55.82 ng L-1 in the water, 2235.04 ng g-1 in suspended particulate matter (SPM), and 1489.60 ng g-1 in sediment. The PAHs in water and SPM were dominated by phenanthrene and pyrene that were mostly derived from lubricant and diesel, while those in sediments were dominated by the high-molecular-weight PAHs, such as indeno[1,2,3-c,d]pyrene. In contrast, the PCBs concentrations reached up to 10.17 ng L-1, 79.72 ng g-1, and 124.33 ng g-1 in the seawater, SPM, and sediment samples, respectively, and they did not show spatial patterns affected by the shipyard. Moreover, the health risk assessment indicated that the shipyard discharge caused a substantial PAHs ecological risk to the adjacent and downstream water environment. Therefore, point source discharge in semi-enclosed bays should be paid close attention to due to the strong pollutant transport effect.

Dietary Microplastic Administration during Zebrafish (Danio rerio) Development: A Comprehensive and Comparative Study between Larval and Juvenile Stages

One of the main sources of MPs contamination in fish farms is aquafeed. The present study investigated, for the first time through a comparative approach, the effects of different-sized fluorescent MPs included in a diet intended for zebrafish (Danio rerio). A comparison based on fish developmental stage (larval vs. juvenile), exposure time, and dietary MPs' size and concentration was performed. Four experimental diets were formulated, starting from the control, by adding fluorescent polymer A (size range 1-5 µm) and B (size range 40-47 µm) at two different concentrations (50 and 500 mg/kg). Zebrafish were sampled at 20 (larval phase) and 60 dpf (juvenile stage). Whole larvae, intestine, liver and muscles of juveniles were collected for the analyses. Polymer A was absorbed at the intestinal level in both larvae and juveniles, while it was evidenced at the hepatic and muscular levels only in juveniles. Hepatic accumulation caused an increase in oxidative stress markers in juveniles, but at the same time significantly reduced the number of MPs able to reach the muscle, representing an efficient barrier against the spread of MPs. Polymer B simply transited through the gut, causing an abrasive effect and an increase in goblet cell abundance in both stages.

Environmental occurrence and ecotoxicity of aquaculture-derived plastic leachates

Plastic products such as fishing nets and foam buoys have been widely used in aquaculture. To enhance the desirable characteristics of the final equipment, plastic gear for aquaculture is mixed with a wide range of additives. Recent studies have shown that additives could be leached out to the environment with a long-term use of aquaculture plastics, forming aquaculture-derived plastic leachates. It should be emphasized that some leachates such as phthalic acid esters (PAEs) and organophosphate esters (OPEs) are endocrine disruptors, which could increase the exposure risk of aquatic products and subsequently display potential threats to human health via food chain. However, systematic studies on the release, occurrence, bioaccumulation, and toxic effects of aquaculture-derived plastic leachates are missing, overlooking their potential sources and ecotoxicological risks in aquatic environments. We have reviewed and compared the concentrations of major plastic leachates in the water environment and organisms of global aquaculture and non-farmed areas, confirming that aquaculture leachate is an important source of contaminants in the environment. Moreover, the toxic effects of aquaculture-derived plastic additives and the related mechanisms are summarized with fish as a representative, revealing their potential health risk. In addition, we proposed current challenges and future research needs, which provides scientific guidance for the use and management of plastic products in aquaculture industries.

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

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

A comprehensive evaluation of microplastic pollution in the Xiangshan Bay of China with special reference to seasonal variation

Marine microplastic (MP) pollution has drawn global attention due to its potential risk to ecosystem. In the present study, we investigated MP pollution in surface water and sediment of a semi-closed bay: the Xiangshan Bay in the East China Sea in spring and summer. The results showed that MP abundance in surface water increased significantly in summer than spring (0.233 and 0.036 item/m³, respectively), while MP abundance in sediment was relatively steady. Meanwhile, the smaller size MPs (diameter < 1000 μm) and land-input fragment-shaped and film-shaped PP and PE increased in surface water in summer compared to spring. Surface microstructure of MPs showed that there were more cracks on MPs in summer comparing to spring. Based on diversity index, MP pollution in the Xiangshan Bay was at a low level and the composition was relatively uncomplicated. The source tracing analysis indicated main contributor of MPs were different in two seasons: textile industry was the dominate source of MPs in spring while fishery production were the dominate source in summer. Our results indicate that the pollution source of MPs could be various in different seasons due to the different climate and human activities, and provide a reference in the prevention and control of MP pollution in semi-closed bay ecosystems.

Microplastics pollution in mud crab (Scylla sp.) aquaculture system: First investigation and evidence

Microplastics (MPs) occurrence in farmed aquatic organisms has already been the prime priority of researchers due to the food security concerns for human consumption. A number of commercially important aquaculture systems have already been investigated for MPs pollution but the mud crab (Scylla sp.) aquaculture system has not been investigated yet even though it is a highly demanded commercial species globally. This study reported the MPs pollution in the mud crab (Scylla sp.) aquaculture system for the first time. Three different stations of the selected aquafarm were sampled for water and sediment samples and MPs particles in the samples were isolated by the gravimetric analysis (0.9% w/v NaCl solution). MP abundance was visualized under a microscope along with their size, shape, and color. A subset of the isolated MPs was analyzed by scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) for the surface and chemical characterization respectively. The average MPs concentration was 47.5 ± 11.875 particles/g in sediment and 127.92 ± 14.99 particles/100 L in the water sample. Fibrous-shaped (72.17%) and transparent-colored (59.37%) MPs were dominant in all the collected samples. However, smaller MPs (>0.05-0.5 mm) were more common in the water samples (47.69%) and the larger (>1-5 mm) MPs were in the sediment samples (47.83%). SEM analysis found cracks and roughness on the surface of the MPs and nylon, polyethylene, polypropylene, and polystyrene MPs were identified by FTIR analysis. PLI value showed hazard level I in water and level II in sediment. The existence of deleterious MPs particles in the mud crab aquaculture system was well evident. The other commercial mud crab aquafarms must therefore be thoroughly investigated in order to include farmed mud crabs as an environmentally vulnerable food security concern.

The factors influencing the vertical transport of microplastics in marine environment: A review

There have been numerous studies that have identified the presence of low-density microplastics (MPs) in the water column and sediments. The focus of current MPs research has shifted towards the interaction of MPs with marine organisms and their potential hazards, including the uptake characteristics, biological transport and toxicological effects of MPs, but the processes involved in the deposition behavior of MPs are still poorly understood. In this review, we summarize the current state of knowledge on the vertical transport of MPs influenced by their physicochemical properties and marine organisms, and discuss their potential impact on MPs deposition. The physicochemical properties of MPs determine their initial distribution. The density, shape, and size of MPs influence their settling state in the marine environment. Marine biota play a key role in the transport of MPs to deep marine environment, mainly by changing the density and adsorption of MPs. Biofouling can alter the surface properties of MPs and increase the overall density, thus affecting the vertical flux of the plastic. Macroalgae may trap MPs particles by producing chemicals or by using electrostatic interactions. Marine swimming organisms ingest MPs and excrete them encapsulated in fecal particles, while the activity of marine benthic organisms may contribute to the transfer of MPs from surface sediments to deeper layers. In addition, MPs may be incorporated into organic particles produced by marine organisms such as marine snow or marine aggregates, increasing the vertical flux of MPs. However, due to the complexity of different sea areas and MPs properties, the deposition behavior of MPs may be the result of the interaction of multiple factors. Thus, the effects of MPs properties, marine organisms and the natural environment on MPs deposition in marine environment needs further research to fill this gap.

First evidence of meso- and microplastics on the mangrove leaves ingested by herbivorous snails and induced transcriptional responses

Although evidence suggests the ubiquity of meso- and microplastics (MMPs) in mangrove forests, our knowledge of their bioavailability and risk on mangrove leaves is scarce. Here, we investigated MMP contamination concerning submerged mangrove leaves and herbivorous snails that mainly feed on them from the four mangrove forests located in Beibu Gulf, Guangxi Province, China. Results showed that the MMP abundance on the mangrove leaves ranged from 0.01 ± 0.00 to 0.42 ± 0.15 items cm^-2, while it ranged from 0.33 ± 0.21 to 6.20 ± 2.91 items individual^-1 in the snails. There were significant positive correlations between snails and leaves regarding the abundance of total MMPs and the proportions of MMPs with the same characteristics. Expanded polystyrene (EPS) that mainly derived from aquaculture rafts, accounted for a major component both on the leaves and in the snails in Shi Jiao (SJ). Both the detection frequency and percentage of larger EPS (2.00-17.50 mm) on the leaves in SJ were higher than other sites. Meanwhile, the detection frequency, abundance and percentage of larger EPS on the leaves had significant positive correlations with those of micro-EPS in the snails. These findings suggested that mangrove leaves may represent a viable pathway for MMPs to enter the herbivorous snails. Larger EPS with higher frequency of occurrence on mangrove leaves were more likely to be encountered and ingested by snail considering its opportunistic feeding behavior. In addition, 11 sensitive genes involved in the processes of metabolism, intestinal mucosal immune systems, and cellular transduction in the snails were significantly suppressed by MMP exposure, which may be potentially used as early biomarkers to indicate the biological effects of MMPs under realistic environmental conditions. Overall, this study provides novel insights into the fate, sources, and biological effects of MMPs on mangrove leaves.

Occurrence of nano/microplastics from wild and farmed edible species. Potential effects of exposure on human health

The occurrence of nano/microplastics (N/MPs) has become a global concern due to their risk on the aquatic environment, food webs and ecosystems, thus, potentially affecting human health. This chapter focuses on the most recent evidence about the occurrence of N/MPs in the most consumed wild and farmed edible species, the occurrence of N/MPs in humans, the potential impact of N/MPs on human health as well as future research recommendations for assessing N/MPs in wild and farmed edible species. Additionally, the N/MP particles in human biological samples, which include the standardization of methods for collection, characterization, and analysis of N/MPs that might allow evaluating the potential risk of the intake of N/MPs in human health, are discussed. Thus, the chapter consequently includes relevant information about the content of N/MPs of more than 60 edible species such as algae, sea cucumber, mussels, squids, crayfish, crabs, clams, and fishes.

Microplastics in water systems: A review of their impacts on the environment and their potential hazards

Microplastics, the microscopic plastics, are fragments of any type of plastic that are being produced today as plastic waste originating from anthropogenic activities. Such microplastics are discharged into the environment, and they enter back into the human body through different means. The microplastics spread in the environment due to environmental factors and the inherent properties of microplastics, such as density, hydrophobicity, and recalcitrance, and then eventually enter the water environment. In this study, to better understand the behavior of microplastics in the water environment, an extensive literature review was conducted on the occurrence of microplastics in aquatic environments categorized by seawater, wastewater, and freshwater. We summarized the abundance and distribution of microplastics in the water environment and studied the environmental factors affecting them in detail. In addition, focusing on the sampling and pretreatment processes that can limit the analysis results of microplastics, we discussed in depth the sampling methods, density separation, and organic matter digestion methods for each water environment. Finally, the potential hazards posed by the behavior of aging microplastics, such as adsorption of pollutants or ingestion by aquatic organisms, due to exposure to the environment were also investigated.

Distribution and sources of microplastics in the Beibu Gulf using in-situ filtration technique

The Beibu Gulf is a vital link between China and the ASEAN nations, and microplastic contamination is rising due to fast growth, coastal life, fisheries, and mariculture. The abundance, distribution, and source analyses were conducted at 25 sample points for this study. According to this study, the average MPs was 0.25 ± 0.05 items/m³, ranging from 0.01 items/m³ to 0.89 items/m³. Fibers, white, cellulose, and 0.33-1 mm were abundant in shape, color, composition, and size, respectively. Multi-statistics-based source analysis indicated land-based inputs (packing materials, textile materials, fisheries, and mariculture) were dominant in the Beibu Gulf. In this study, we also acknowledged a comprehensive comparison and convenience between plankton pumps and other conventional designs to collect microplastic samples from water. We suggested that using a uniform design could elevate the data quality of microplastics.

Policy impact on microplastic reduction in China: Observation and prediction using statistical model in an intensive mariculture bay

Plastic pollution in the environment has spurred debate among scientists, policymakers, and the general public over how industrialization and consumerism are wreaking havoc on our ecosystem, but some policies might assist to ameliorate the problem in the near future. In this study, the decision tree classifier and Bayesian Structural Time Series (BSTS) model was used to anticipate the possible sources of microplastics and their near future state in 26 surface sediment and a sediment core, respectively in Sansha Bay, which has been criticized for its intensive mariculture applications. An inventory of microplastics in the sediment core was estimated, and it was discovered that during the previous six decades, an average of 181.95 tons of microplastics were deposited, with an average deposition (by a layer of sediment) of 179.44 tons/cm. According to the DT classifier, mariculture was the primary source of microplastics, whereas urban and industrial areas were the primary sources of POPs. The Bayesian Structural Time Series (BSTS) model revealed a microplastic downward slope, indicating that regional and national strategies implemented might successfully reduce microplastic pollution regionally.

The occurrence, speciation, and ecological effect of plastic pollution in the bay ecosystems

Bay is a unique part of the ecosystem, acting as the intersection for marine and terrestrial systems and hosting diverse biological organisms. The ubiquitous application of plastics has resulted in a massive amount of plastic waste released and accumulated in the bay ecosystem, posing significant ecological effects. Thus, thoroughly understanding plastic pollution's occurrence, speciation, and ecological effect in the bay ecosystems is of vital importance. We conducted a comprehensive review on the sources and distribution of plastics in the bay ecosystem, and the associate ecological effects, from individual toxicity to trophic transfer in ecosystems. Among bay areas around the world, the concentrations of microplastics vary from 0.01 to 3.62 × 10⁵ item/m³ in seawater and 0 to 6.75 × 10⁵ item/kg in sediment. Small-sized plastic particles (mostly <2 mm) were widely reported in bay organisms with the concentration range of 0 to 22.5 item/ind. Besides, the toxicity of plastics on marine organisms has been documented in terms of mortality, growth, development, reproduction, enzyme activity and transcription. Since abundance of small plastic particles (e.g., micro- and nano-scale) is far greater than large plastic debris in the bay ecosystems, in-depth risk assessment of small-sized plastics needs to be conducted under environmentally realistic conditions. Our review could provide a better understanding on the occurrence, speciation, and ecological effect of plastic pollution in the bay ecosystems.

Long-term deposition records of microplastics in a plateau lake under the influence of multiple natural and anthropogenic factors

Microplastic accumulation in the lake aquatic environment has attracted worldwide attention, but the long-term deposition characteristics and influencing factors of microplastics are not clear. Hence, we attempted to analyze the factors that influence the accumulation of microplastics during the process of natural environmental change and social development through the method of the sedimentological approach. In this investigation, the chronological sequence of sediment core was set up based on lead-210 composition to study microplastic accumulation rates in a plateau lake, Jianhu Lake. For the first time, the records of microplastic deposition were analyzed combined with multiple anthropogenic and natural factors, including 4 natural and 17 social factors to reveal the influence of natural processes and social development on microplastic abundances. The results showed that sediments were highly contaminated by microplastics, and the mean abundance of microplastics in the sediment cores of Jianhu Lake was 924 ± 427 particles/kg, and showed a gradually increasing trend from the bottom (25 to 30 cm) to surface layer (0 to 5 cm). Blue and black were the main colors of microplastics, and the average proportion of wirelike microplastics was 63 %. Additionally, the polymer type of microplastic was mainly rayon, the surface morphology of different polymer types was disparate, and various elements enriched on the surface of microplastics were also detected. In the past 70 years, the deposition rate of microplastics in Jianhu Lake maintained the trend of continuous growth, and the abundance of microplastics is projected to be 448 to 3017 and 513 to 3670 particles/kg by 2035 and 2050, respectively. What is more, there are significant correlations among multiple natural and anthropogenic factors and microplastic deposition, as well as microplastic polymer species.

Marine litter on the beaches of the Kanyakumari, Southern India: An assessment of their abundance and pollution indices

The problem of marine litter is increasing along the Indian coast. For conducting a baseline study to identify and assess the abundance, clean-coast index (CCI), and plastics abundance index (PAI) of marine litter were calculated on the beaches of Kanyakumari, Southern India. A total of 11,439 marine litter items were collected and classified into 33 groups along the 7 beaches of Kanyakumari. From the results, plastics were the most abundant items (65.08 %) followed by foam (21.93 %), along with cloths (4.59 %), rubber (3.09 %), papers (2.26 %), glass (2.16 %), metal (0.38 %), wood (0.26 %), and others (0.26 %). The average CCI value (27.24) indicates that all beaches are 'extremely dirty'; however, the PAI average value (4.37) indicates 'high abundance'. About 96.87 % of the marine litter originates from the land-based sources. This study provides an interpretive framework for further plastic pollution assessment, which could lead to a better marine litter management on Indian beaches.

Potential risk of microplastics in processed foods: Preliminary risk assessment concerning polymer types, abundance, and human exposure of microplastics

The occurrence of microplastics (MPs) has been widely reported in human foodstuffs, and their potential negative effects on human health have been brought into focus. Processed foods are more susceptible to MPs as contamination can be introduced during processing and packaging. However, the risk posed by MPs in processed foods remained unclear. This work aims to critically review the available data for MPs in 11 types of possessed foods and to conduct a preliminary risk assessment of MPs in processed foods. For a comprehensive evaluation, three indicators were selected and determined, namely chemical risk, pollution load, and estimated daily intake (EDI). Our results suggest that nori has the highest chemical risk, followed by canned fish, beverages, table salt, and other food items. In the case of pollution load, nori and milk fall into the risk category of Ⅳ and Ⅲ respectively. Table salts, bottled water, and sugar exhibited lower MPs pollution load (risk category of Ⅱ), whereas the pollution loads of other foods were calculated to be category Ⅰ. Moreover, a correlation between the pollution load of sea salts and MPs pollution level in ambient seawater was found. Regarding EDI of MPs from different processed foods, MPs intakes through bottled water (14.3 ± 3.4 n kg^-1 d^-1) and milk (6.6 ± 2.4 n kg^-1 d^-1) are significantly higher than that of the other foods (< 1 n kg^-1 d^-1). The probabilistic estimation of MPs daily intake indicated that children (19.7 n kg^-1 d^-1) are at a higher health risk than adults (female: 17.6 n kg^-1 d^-1, male: 12.6 n kg^-1 d^-1). Nevertheless, the exposure dose used in toxicological studies was about 10 times higher than the MPs intake via processed foods. Therefore, we argued that MPs in processed foods only carry limited risk. Overall, this study would provide the basis for risk management of MPs in processed food products.

Selective adsorption of antibiotics on aged microplastics originating from mariculture benefits the colonization of opportunistic pathogenic bacteria

Microplastics and antibiotics widely coexist in the aquatic environment, especially in mariculture regions. However, antibiotics adsorbed on microplastics and their role in the colonization of microorganisms on microplastics are poorly understood. Therefore, in-situ aging experiments were conducted to investigate the impact of antibiotics and microplastics co-occurrence on microorganisms and assess their potential risks to human health. Results showed that antibiotics were adsorbed selectively on microplastics, with 29 investigated antibiotics (n = 40) detected in surrounding water but only 6 investigated antibiotics were adsorbed on microplastics. The concentration of antibiotics accumulated on microplastics was controlled by microplastic types and environmental conditions. For example, aged polypropylene (PP) had more developed pore structures resulting in higher adsorption of antibiotics than other microplastic types. High-throughput sequencing showed higher diversity and distinct composition of microorganisms attached to the microplastics than the surrounding water. Opportunistic pathogenic bacteria such as Mycobacterium possessed positive relationships with tetracycline and doxycycline on aged microplastics, which showed adsorbed antibiotics on aged microplastics could benefit some specific pathogens colonized on the microplastics and spread into unaffected ecosystems, marine organisms even humans. The health risk quotient (HQ) implied the potential human health risk of consuming commercial seafood polluted by antibiotics and microplastic loaded with antibiotics. This study revealed the interaction of antibiotics and microorganisms with aged microplastics in aquaculture systems, providing a novel insight into their synergistic effects on ecological and human health.

Microplastics and linear alkylbenzene levels in oysters Crassostrea gigas driven by sewage contamination at an important aquaculture area of Brazil

The levels of linear alkylbenzenes (LABs) and the occurrence of microplastics (MPs) in the oysters Crassostrea gigas were evaluated in six farming areas in southern Brazil. The results revealed higher concentrations of LABs in oyster tissue from the Serraria (1977 ± 497.7 ng g^-1) and Imaruim (1038 ± 409.9 ng g^-1) sites. Plastic microfibers were found in oysters from all locations with values from 0.33 to 0.75 MPs per oyster (0.27-0.64 MPs per gram) showing the ubiquitous presence of this contaminant in the marine environment, which could be considered a threat to farming organisms. In addition, elements such as Ti, Al, Ba, V, Rb, Cr, and Cu were found in the chemical composition of the microfibers, suggesting MPs as vectors of inorganic compounds. A positive correlation between LABs and thermotolerant coliforms suggests that sewage discharges are the main source of contamination in these oysters cultured for human consumption. The present study highlights the need for efficient wastewater treatment plants and the implementation of depuration techniques in oysters from farming areas.

Contamination and distribution of buried microplastics in Sarakkuwa beach ensuing the MV X-Press Pearl maritime disaster in Sri Lankan sea

Abundance of buried microplastics in sand profiles and pellet pollution index at Sarakkuwa beach, at west-coast of Sri Lanka was studied as a case study due to the receival of plastic nurdles and debris from the MV X-Press Pearl ship disaster in May 2021. Sand collected at 7 locations to a depth of 2 m in different depths for a beach segment of 200 × 25 m² during October 2021 and sand samples obtained from beach surface during March 2020 from the same location were analyzed for microplastics. Beach was contaminated with 2-5 mm sized partially pyrolyzed LDPE fragments and nurdles demonstrating a peak abundance of 13.3702 g/kg and1 mm-500 μm sized LDPE fragments up to 2.0 m depth. High concentrations of Mo and Cr were observed in the sand collected in 2021. Sarakkuwa beach is critically polluted by nurdles, partially pyrolyzed microplastics, and toxic elements from ship disaster.

Application of a microplastic trap to the determination of the factors controlling the lakebed deposition of microplastics

Microplastics (MPs) in aquatic environments are hard to degrade, easy to transport, and potentially hazardous to biota. Previous studies of MPs in lakes have shown that their deposition is a significant process controlling both their lateral dispersal from a source, and their concentration within the water column. However, the lakebed depositional rates of MPs have predominantly been determined using laboratory experiments and/or through model simulations that may not fully reflect field conditions. In this paper, lacustrine depositional rates in Lake Ulansuhai were documented using an MP trap that allowed for the assessment and quantification of the depositional rates of MPs of differing size, density, and shape at three sampling sites over five different time periods. The results showed that the downward flux for all types of MPs near the lakebed was correlated with wind speed. Higher wind speeds led to the resuspension of greater amounts of MPs in the lakebed sediments and the transport of greater amounts of MPs from the lake inlet to the lake interior and outlet along the hydrologic flow directions. Consequently, higher wind speeds increased the abundance of MPs at the sediment-water interface and intensified the vertical mixing of MPs in the lake water, resulting in a higher depositional flux of MPs. Particles of differing size, shape, and density exhibited different depositional rates. In general, fragmentary, larger size, and higher density MPs were more likely to be deposited. Thus, size and shape have a strong effect on the migration and deposition of HDMPs in Lake Ulansuhai.

Widespread occurrence of microplastics in marine bays with diverse drivers and environmental risk

Microplastic contamination in the sediment of marine bays has attracted widespread attention, whereas the distribution, sedimentation, morphology and risk of microplastics at regional scale remain poorly understood. By introducing a data mining framework into microplastic research, we compiled a microplastic dataset of 649 samples from 24 bays to enhance the understanding of geographical difference and drivers, transfer, composition profile and environmental risk of sedimental microplastics. Microplastic abundance varied from 0.72 to 1963.96 items/kg dry weight, with higher concentrations mainly occurring in East Asian bays. The spatial pattern in abundance was driven by the river plastic emissions, aquaculture production and hydrodynamic condition. A significantly positive correlation between microplastic abundance in water and sediment was found, and microplastic sedimentation was related to polymer density, hydrodynamic conditions and sediment properties. The dominant shape and polymer of sedimental microplastics were fiber and polypropylene, respectively, and the similarity of microplastic composition decreased with increasing geographical distance. The environmental risks of microplastics were partitioned into three classes (Rank II-Rank IV) with a two-dimensional assessment system considering the bioavailability and toxicity of microplastics, and Asian bays were identified as potential high-risk areas. To reduce the environmental risk of sedimental microplastics in bays, priority should be given to the removal of microfibers, and control measures depend on the risk classes and dominant polymers. Microplastic abundance and composition were significantly affected by methodological choices regarding sampling, pretreatment and identification, suggesting a unified methodology is essential to further enhance our knowledge on the distribution and risk of microplastics in marine bays.

Impacts of terrestrial input on the distribution characteristics of microplastics in the East China Sea characterized by chromophoric dissolved organic matter (CDOM) analysis

Large quantities of microplastics are found in the East China Sea (ECS), however, the impacts of complicated terrestrial input on the distribution characteristics of microplastics have not been studied. Hence, we aimed to characterize the microplastic distribution in the ECS combined with the fluorescence characteristics of chromophoric dissolved organic matter (CDOM), a sensitive technique to trace terrestrial substances in seawater. The average microplastic abundance in the surface seawater of ECS was 34.73 ± 4.05 items/m³ and sites in the north ECS had a higher microplastic abundance (55.90 ± 2.47 items/m³) than those in the southern region (11.22 ± 4.01 items/m³), due to its proximity to the Yangtze River estuary and Hangzhou Bay. Polyethylene (PE, 44.2 %) was the most abundant microplastic type in the northern region, whereas polyethylene terephthalate (PET, 28.4 %) had a higher proportion in the south ECS. Besides, sites in the north ECS had a higher diversity index of microplastics, suggesting various sources of microplastic pollution. Interestingly, a stronger correlation with the diversity index was found for protein-like component C3 (R² = 0.56) in northern regions compared to fulvic-like component C1 (R² = 0.32) and humic-like component C2 (R² = 0.28), suggesting the significant impact of anthropogenic discharge. Moreover, no correlation between fluorescence components and microplastic diversity index was found in the south ECS, indicating that CDOM can reflect the impact range of terrestrial input on the distribution characteristics of microplastics. This research might be useful in assessing and reducing the impact of terrestrial input on the distribution characteristics of microplastics in the ECS.

Occurrence, characterization, and source delineation of microplastics in the coastal waters and shelf sediments of the central east coast of India, Bay of Bengal

The present study investigates the abundance, distribution, and characterization (shape, size, colour, chemical composition) of microplastics (MPs) in surface water and sediment from the shelf region of the central east coast of India. The surface water and sediment samples were collected at varying depths (12.8-63 m) from 21 locations covering ∼1200 km. The mean abundance of MPs in surface water and sediments were 5.3 × 10⁴ particles. km^-2, 209 ± 99 particles. kg^-1 of dry weight, respectively. Stereomicroscopy, Raman spectroscopy, and micro Fourier Transform Infra-red Spectroscopy (FTIR) were employed for the quantification and characterization of the polymers. Polyolefin (polyethylene and polypropylene) were the dominant polymers in both surface water and sediments indicating their source primarily land based. Surface water and sediment MPs were mostly blue coloured. Fibre (77%) and fragment (38%) were the dominant morphotypes in surface water and sediments, respectively. Surface characteristics studies using Scanning Electron Microscope (SEM) highlight the breakdown progress of the particles; Small MPs (<1 mm) account for >50% of the whole and dominant in the offshore region (10 km). The results reveal that the primary sources of MPs are most likely to be originating from riverine fluxes and fishing-based activities.

Characteristics of microplastic pollution and analysis of colonized-microbiota in a freshwater aquaculture system

The microbial communities associated with microplastics (MPs) and their ambient environments have received wide attention. Although previous studies have reported the differences of microbial communities between MPs and natural environment or substrates, the effects of MPs on microbial balance and functions in ambient water remain unclear, particularly for aquaculture water. Here, we investigated the MPs pollution in farm ponds of grass carp located in the Foshan City of Guangdong Province and reported the distinction of bacterial structures, functions, and complexity between microbiota on MPs and in water. MPs with an average abundance of 288.53 ± 74.27 items/L in pond water were mostly fibers and cellulose, mainly transparent and in size of 0.5-1 mm. Structures and functions of bacterial communities on MPs significantly differed from that in pond water. A large number of enriched or depleted OTUs on MPs compared with water belong to the phylum Proteobacteria, the predominant phylum in microbial communities on MPs and in water. Some species included in the phylum Proteobacteria have been shown to be cellulose-degrading and pathogenic. Microbiota on MPs exhibited higher species richness and diversity as well as a more complex network than that in water, illustrating MPs as a distinct habitat in the aquaculture system.

Microplastics in Seawater, Sediment, and Organisms from Hangzhou Bay

Microplastics (MPs) are widely present in global oceans, and can pose a threat to marine organisms. This study examined the abundance and characteristics of MPs in seawater, sediment, and organism samples collected from Hangzhou Bay. Abundance of MPs in seawater (n = 26) and sediment (n = 26) were 0.77-9.6 items/m³ and 44-208 items/kg dw, respectively. Size of MPs in sediment (mean 2.5 mm, range 0.21-5.3 mm) was significantly (p < 0.05) larger than that in seawater (1.1 mm, 0.13-4.9 mm). Fiber was consistently the predominant shape of MPs in seawater and sediment. The major polymer composition of MPs was polyethylene (PE; mean 47 %) in seawater, but textile cellulose (60 %) was the main polymer type of MPs in sediment. Average abundance of MPs in marine organisms (n = 388) ranged from 0.064 (zooplankton) to 2.9 (Harpodon nehereus) items/ind, with the mean size of 0.19-1.4 mm. MP abundance in marine organisms was not significantly correlated with their trophic level. Fiber was always the predominant shape of MPs in different marine organisms, contributing mean 67 (fish)-93 % (zooplankton) of total MPs. MPs in crustacean (mean 58 %), shellfish (64 %), and cephalopod (29 %) were dominated by textile cellulose. Whereas, PE (mean 44 %) and polypropylene (43 %) were the major polymer compositions of MPs in fish and zooplankton, respectively. To our knowledge, this is the most comprehensive study investigating the occurrence of MPs in environmental matrixes from Hangzhou Bay, which contributes to the better understanding of environmental behaviors of MPs in estuarine sea environment.

Anthropogenic microfibers are highly abundant at the Burdwood Bank seamount, a protected sub-Antarctic environment in the Southwestern Atlantic Ocean

Microplastics debris in the marine environment have been widely studied across the globe. Within these particles, the most abundant and prevalent type in the oceans are anthropogenic microfibers (MFs), although they have been historically overlooked mostly due to methodological constraints. MFs are currently considered omnipresent in natural environments, however, contrary to the Northern Hemisphere, data on their abundance and distribution in Southern Oceans ecosystems are still scarce, in particular for sub-Antarctic regions. Using Niskin bottles we've explored microfibers abundance and distribution in the water column (3-2450 m depth) at the Burdwood Bank (BB), a seamount located at the southern extreme of the Patagonian shelf, in the Southwestern Atlantic Ocean. The MFs detected from filtered water samples were photographed and measured using ImageJ software, to estimate length, width, and the projected surface area of each particle. Our results indicate that small pieces of fibers are widespread in the water column at the BB (mean of 17.4 ± 12.6 MFs.L^-1), from which, 10.6 ± 5.3 MFs.L^-1 were at the surface (3-10 m depth), 20 ± 9 MFs.L^-1 in intermediate waters (41-97 m), 24.6 ± 17.3 MFs.L^-1 in deeper waters (102-164 m), and 9.2 ± 5.3 MFs.L^-1 within the slope break of the seamount. Approximately 76.1% of the MFs were composed of Polyethylene terephthalate, and the abundance was dominated by the size fraction from 0.1 to 0.3 mm of length. Given the high relative abundance of small and aged MFs, and the oceanographic complexity of the study area, we postulate that MFs are most likely transported to the BB via the Antarctic Circumpolar Current. Our findings imply that this sub-Antarctic protected ecosystem is highly exposed to microplastic pollution, and this threat could be spreading towards the highly productive waters, north of the study area.

Prevalence of small-sized microplastics in coastal sediments detected by multipoint confocal micro-Raman spectrum scanning

Microplastics have become global emerging issue and received widespread attention in recent years. Due to their chemical persistence, plastic particles can be broken into smaller items but accumulated for long time in the environment like sediment. However, limited by current detection technologies, the distribution and characteristics of small-sized microplastics in coastal sediment remain uncertain. In this study, we established a new method based on micro-Raman spectroscopy for detecting small-sized microplastics, namely multipoint confocal micro-Raman spectrum scanning (MCmRSS). The MCmRSS was first applied in detecting microplastics in the sediment samples collected from three bays of the East China Sea. The minimum size of microplastics was 4 μm and average microplastics concentration was 91 ± 55 items /g dry weight sediment, with fragment and polyethylene as the most common shape and polymer type, respectively. The spatial variation of microplastics was in accordance with the strength of coastal human activities and marine dynamics. In all the microplastic items, the small-sized ones (<10 μm) accounted for 67%; and the relationship between microplastic concentration and its size followed a power-exponential equation. Compared with previous studies, the number of microplastics in coastal sediments detected by the MCmRSS increased by 2 orders of magnitude, which was benefited from the advantages of multipoint scanning in the fixed identification areas and high resolution of micro-Raman spectrum. Our findings would summon the re-evaluation of the potential risks of small-sized microplastics in the coastal environment.

A Review on Heavy Metal Ion Adsorption on Synthetic Microfiber Surface in Aquatic Environments

Synthetic microfibers (SMFs), tiny particles which gets fragmented from large fragments of large synthetic fibers having less than 10 µm in diameter, have gathered ubiquitously in each and every corner of the earth. After their release into the aquatic environment, they remain there without natural degradation. Furthermore, it can be anticipated that floating units are transported along the food chain leading to bioaccumulation. It has been estimated that approximately 10-20 Mt of large fabric products as garbage enter into aquatic system per annum. Recently, these synthetic fragments have been investigated as transporters of heavy metal ions (HMs) showing different types of interactions. Yet, the underlying mechanism of these types of interaction is not known, especially the factors stimulating this process and how badly they affect biotic communities. Through this article, a detailed survey was carried out on the sources of microfibers and HMs into the aquatic environment, adsorption of different types of HMs on the SMF surface, mechanics favors these HM-MF interactions, particularly highlighting the significant roles of interaction on microbial biofilm formation. Their collaborative effects which possess harmful effects on aquatic as well as terrestrial organisms was also discussed. Lastly, the future investigations should focus on rigorous research in this field. This article to the best of our knowledge briefly describes the current research developments and emphasizes the vital function of the microorganisms on MFs-HMs interactions with the encouragement for rigorous research in this field to reveal accurate mechanisms and decrease the hazards related with MF presence.

Can we quantify the aquatic environmental plastic load from aquaculture?

Aquaculture provides livelihoods for hundreds of millions of people, but it also forms a significant source of plastic litter that poses a serious hazard to aquatic ecosystems. How to assess and subsequently manage plastic loads from aquaculture is a pending and pressing issue for aquaculture sustainability, and an important concern for water environment monitoring and management. In this study, we developed the first framework for estimating plastic litter from aquaculture by combining data from satellite remote sensing, drones, questionnaires, and in situ measurements. By acquiring multidimensional (human and nature) and multiscale (centimeter to basin scale) data, this framework helped us understand the aquaculture farming patterns and its spatial and temporal evolution, and thus estimate the plastic load it generates and suggest effective management approaches. Applying this framework, we assessed the marine plastic load from oyster floating raft farming in the Maowei Sea, a typical mariculture bay in China, with an increasing farming area. Approximately 3840 tons of plastic waste is expected to be discharged into the sea in the next four years (the average service life of a floating raft) without improvements in aquaculture waste management. Strengthening governance, timely plastic removal, innovative replacement, and transforming farmers' behavior patterns are recommended as the subsequent measures for plastic management. This framework can be extended to other regions and other aquaculture patterns, and is applicable to local, regional, and global aquaculture plastic litter assessments. It is a source-based method for evaluating plastic pollution that is more conducive to subsequent plastic management than traditional post-contamination environmental monitoring. In the context of the global expansion of mariculture and the global commitment to action to combat plastic pollution, this approach could play a critical role in the investigation and management of plastic waste in aquatic environments.

Abundance of microplastics in cultured oysters (Crassostrea gigas) from Danang Bay of Vietnam

This study focuses on determination of quantity, shape, size and polymer types of microplastics in Pacific oysters (Crassostrea gigas) cultured in Danang Bay, Vietnam. Visual verification and chemical identification of microplastics was carried out by μFT-IR spectra using Nicolet iN10 MX Infrared Imaging Microscope. The average abundance of microplastic in oysters was 1.88 ± 1.58 particles/g (wet weight) and 18.54 ± 10.08 particles/individual. The prevalent shape of microplastics included three main forms as fragment, fiber and bead corresponding to 73.71; 25.84 and 0.45%, respectively. Additionally, the size of microplastics was a range of 22.4-1318.8 μm, and the most common size was less than 100 μm, accounted for 77.30%. Fifteen polymer types were detected while Nylon was the most abundant polymer type with 50.56%. In this study, microplastics accumulation with their abundance and polymeric structures could be considered as reliable evidence for further studies on assessment of their potential risk to human health.

Towards realistic predictions of microplastic fiber transport in aquatic environments: Secondary motions

Microplastics fibers are abundant in aquatic environments and are an emerging environmental threat. Understanding how fibers are transported in aquatic environments is essential for identifying pollution hotspots and developing remediation strategies. Over recent years, an increasing number of drag models have been proposed to describe the transport of microplastics in aquatic environments. However, none of the proposed models consider secondary motions, which are responsible for non-vertical settling motions. To investigate the role of secondary motions, an experimental setup with an image processing technique was developed to capture the spatial-temporal kinematics of microplastic fibers settling in quiescent water. A new drag model, which adopts the crosswise sphericity to consider the effects of secondary motions of a microplastic fiber and the Aschenbrenner shape factor to account for the unique morphology of the microplastic fiber, was proposed and evaluated. Secondary motions of microplastic fibers have profound effects on their settling trajectories and deposited positions. The settling motion and drag coefficient of a microplastic fiber is an orientation-dependent process. Moreover, the secondary motion is strongly dependent on the fiber dimension and density. The here-proposed drag model is proven to more accurately characterize the settling motion of microplastic fibers compared to existing models that neglect secondary motions. The methodology and model from this study can be used to progress towards improved and realistic predictions of the transport of microplastic fibers in aquatic environments.

Microplastics in the tissues of commercial semi-intensive shrimp pond-farmed Litopenaeus vannamei from the Gulf of California ecoregion

The omnipresence of microplastics (MPs) in marine and coastal environments has attracted attention owing to their effects on various organisms, including humans. We present the first study of MPs in the gastrointestinal tract (GT), gills (GI), and exoskeleton (EX) of the farmed whiteleg shrimp Litopenaeus vannamei from commercial aquaculture facilities in northwestern Mexico that have operated semi-intensively for the last two decades. We found that the number of MP items per tissue was 7.6 ± 0.6 in the GT, 6.3 ± 0.9 in the GI, and 4.3 ± 0.9 in the EX, with an average of 18.5 ± 1.2 MP items per shrimp (1.06 items/g, wet weight [ww]). MP concentrations were 261.7 ± 84.5, 13.1 ± 1.8, and 2.6 ± 0.6 items/g (ww) in the GT, GI, and EX, respectively. Microplastics ranged from 30 to 2800 μm in size (360 ± 39 μm) with fibers (∼90.8%), filament-shape (∼93.4%), and transparent (∼47.7%) being the most common ones. Polyethylene (∼54.5%) and polyamide (∼24.2%) were the most commonly identified polymers, although polyesters (∼12.1%), polystyrene (∼6.1%), and nylon (∼3.0%) were also found. The abundance of MPs in farmed L. vannamei may be related to their feeding habits and the availability of MP sources in aquaculture facilities.

The role of mesopelagic fishes as microplastics vectors across the deep-sea layers from the Southwestern Tropical Atlantic

Microplastics (MPs; <5 mm) are a macro issue recognised worldwide as a threat to biodiversity and ecosystems. Widely distributed in marine ecosystems, MPs have already been found in the deep-sea environment. However, there is little information on ecological mechanisms driving MP uptake by deep-sea species. For the first time, this study generates data on MP contamination in mesopelagic fishes from the Southwestern Tropical Atlantic (SWTA) to help understand the deep-sea contamination patterns. An alkaline digestion protocol was applied to extract MPs from the digestive tract of four mesopelagic fish species: Argyropelecus sladeni, Sternoptyx diaphana (Sternoptychidae), Diaphus brachycephalus, and Hygophum taaningi (Myctophidae). A total of 213 particles were recovered from 170 specimens, and MPs were found in 67% of the specimens. Fibres were the most common shape found in all species, whereas polyamide, polyethylene, and polyethylene terephthalate were the most frequent polymers. The most contaminated species was A. sladeni (93%), and the least contaminated was S. diaphana (45%). Interestingly, individuals caught in the lower mesopelagic zone (500-1000 m depth) were less contaminated with MPs than those captured in the upper mesopelagic layer (200-500 m). Our results highlight significant contamination levels and reveal the influence of mesopelagic fishes on MPs transport in the deep waters of the SWTA.