Microplastics in the Northwestern Pacific: Abundance, distribution, and characteristics

Microplastic abundance, distribution and composition in the mid-west Pacific Ocean

Microplastic pollution is widespread across most ocean basins around the world. Microplastics (MPs) are small plastic particles that have a significant impact on the marine environment. Various research on plastic pollution have been conducted in several regions. However, currently, there is limited data on the distribution and concentration of MPs in the mid-west Pacific Ocean. Therefore, this study we investigated the abundance, distribution, characteristics, and compositions of MPs in this region. Sea surface water samples collected from 18 stations showed a microplastic concentration range of 6028-95,335 pieces/km² and a mean concentration of 34,039 ± 25,101 pieces/km². Highest microplastic concentrations were observed in the seamount region of western Pacific. We observed a significant positive correlation between microplastic abundance and latitude across the study region. It was observed that microplastic concentrations decreased with increasing offshore distance at sites located on a 154° W transect. Fibres/filaments were the dominant microparticles observed in this study (57.4%), followed by fragments (18.3%). The dominant particle size range was 1-2.5 mm (35.1%), followed by 0.5-1 mm (28.5%), and the dominant particle colour was white (33.8%), followed by transparent (31.0%) and green (24.6%). The most common polymer identified by μ-Raman was polypropylene (39.1%), followed by polymethyl methacrylate (16.2%), polyethylene (14.1%) and polyethylene terephthalate (14.2%). The possible sources and pathways of microplastics in the study area were proposed based on the morphological and compositional characteristics of particles, their spatial distribution patterns, and shipboard current profiling (ADCP). Our study contributes to the further understanding of MPs in remote ocean areas.

On optical sensing of surface roughness of flat and curved microplastics in water

The growth of microplastic (MP) pollution is of increasing concern and represents a global challenge. In situ detection of these small particles is difficult because of their sizes, shapes, transparency or translucency, surface texture and ambient conditions. We propose and demonstrate the use of a prototype optical sensor to detect flat, nearly flat, curved and rough MPs prepared from commercial polyethylene terephthalate (PET) plastics and PET bottles in water. The prototype measures the specular reflection of a laser radiation incident on MPs, with a photodiode, and the transmitted laser speckle pattern, with a charge-coupled device (CCD) camera. The presence of the MPs as well as the optical surface roughness are determined from the specular reflection. Additionally, the so-called speckle contrast calculated from the speckle pattern, as a promising tool, is used to rank the rough MPs according to the different average surface roughness, to approximately twice the wavelength of the probing light. The novel application of laser speckle contrast and the optical roughness estimation allows the description of MP surface roughness in water. Moreover, in combination with earlier studies, these results, therefore, pave a way for the complete and a relatively easier description of MPs properties optical and also advances our step towards the development of simple and robust optical monitoring techniques for micro and nanoplastics in open and wastewater.

Evidence of ingested plastics in stranded loggerhead sea turtles along the Greek coastline, East Mediterranean Sea

Plastic debris has become a major threat to the marine environment and wildlife. Sea turtles are particularly vulnerable, and are known to ingest plastic debris globally; however, information from Greek waters is still absent. In this study, 36 stranded dead loggerhead turtles (Caretta caretta) were collected from the Greek coastline area, and their gastrointestinal content was analysed for ingested plastic debris. Twenty-six individuals (72%) were found to have ingested plastic, with an average of 7.94 ± 3.85 (SE) plastic items per turtle. In total, 286 plastic items were counted and categorised by size, shape, colour, and polymer type. Fourier Transform Infrared Spectrometry revealed that polypropylene and polyethylene were the dominant polymer plastic types found. Results indicated a variation in plastic ingestion amongst life stages of the loggerhead specimens. This study provides evidence of plastic ingestion by loggerhead turtles in Greek waters.

Microplastic contamination of drinking water: A systematic review

BACKGROUND

Microplastics (MPs) are omnipresent in the environment, including the human food chain; a likely important contributor to human exposure is drinking water.

OBJECTIVE

To undertake a systematic review of MP contamination of drinking water and estimate quantitative exposures.

METHODS

The protocol for the systematic review employed has been published in PROSPERO (PROSPERO 2019, Registration number: CRD42019145290). MEDLINE, EMBASE and Web of Science were searched from launch to the 3rd of June 2020, selecting studies that used procedural blank samples and a validated method for particle composition analysis. Studies were reviewed within a narrative analysis. A bespoke risk of bias (RoB) assessment tool was used.

RESULTS

12 studies were included in the review: six of tap water (TW) and six of bottled water (BW). Meta-analysis was not appropriate due to high statistical heterogeneity (I2>95%). Seven studies were rated low RoB and all confirmed MP contamination of drinking water. The most common polymers identified in samples were polyethylene terephthalate (PET) and polypropylene (PP), Methodological variability was observed throughout the experimental protocols. For example, the minimum size of particles extracted and analysed, which varied from 1 to 100 μm, was seen to be critical in the data reported. The maximum reported MP contamination was 628 MPs/L for TW and 4889 MPs/L for BW, detected in European samples. Based on typical consumption data, this may be extrapolated to a maximum yearly human adult uptake of 458,000 MPs for TW and 3,569,000 MPs for BW.

CONCLUSIONS

This is the first systematic review that appraises the quality of existing evidence on MP contamination of drinking water and estimates human exposures. The precautionary principle should be adopted to address concerns on possible human health effects from consumption of MPs. Future research should aim to standardise experimental protocols to aid comparison and elevate quality.

Microplastic pollution around remote uninhabited coral reefs of Nansha Islands, South China Sea

Microplastic (MP) pollution is a growing environmental problem in the global oceans. However, there is relatively little evidence of the extent of MP pollution around remote islands, such as coral reefs, in the open ocean. In this study, we conducted a large-scale investigation of MP pollution in the surface waters around the remote uninhabited coral reefs of Nansha Islands in South China Sea. Microplastics were widespread in the surface waters with an average abundance of 0.0556 ± 0.0355 items/m³, although this varied among the coral reefs. The MPs were predominantly composed of polypropylene (PP) and polyethylene (PE), and > 70% of them were <3 mm in size. Fragments and fibers comprised the most common MP types. The similarity between macro plastic and MP compositions provided evidence for the tracing of MP sources in the study area. The main pollutants (transparent PP fibers and PE fibers) around these remote coral reefs may originate from fishing gear abrasions. The plastic waste released from nearby residential islands and high-intensity fishing activities around Nansha Islands likely represented important local sources. Overall, the abundance of MPs found in the surface waters surrounding these remote coral reefs in the South China Sea was relatively low; however, these levels of MP pollution should not be disregarded given the importance of coral reef ecosystems.

Microplastics in subsurface coastal waters along the southern coast of Viti Levu in Fiji, South Pacific

Microplastics (MPs) remain largely understudied in Small Island Developing States. This study is aimed at comparing the abundance and characteristics of MPs in rural and urban marine coastal sites located along the southern coast of Fiji's main inhabited island, Viti Levu. Collection of subsurface waters (at depth of ca. 0.6 m) was performed at seven sites via Niskin bottle. Samples were filtered over a membrane filter to extract MPs and to allow visual analysis and polymer identification by using attenuated total reflectance in Fourier transform infrared spectroscopy. Findings from this study depict widespread presence of MPs in both urban and rural sites, and show no significant differences in the four parameters studied, i.e. abundance of MP pieces (2.0 vs 1.6 MP/L, respectively), form types (dominance of fibers), size (0.5-0.9 and 1.0-1.4 mm totaling 48% of the samples), and color (blue contributing 30%, and red and black contributing 25% each). These findings challenge the common expectation of a higher MPs pollution in urban areas compared to rural areas.

Separation, characterization and identification of microplastics and nanoplastics in the environment

Microplastics (MPs) have globally been detected in aquatic and marine environments, which has raised scientific interests and public health concerns during the past decade. MPs are those polymeric particles with at least one dimension <5 mm. MPs possess complex physicochemical properties that vary their mobility, bioavailability and toxicity toward organisms and interactions with their surrounding pollutants. Similar to nanomaterials and nanoparticles, accurate and reliable detection and measurement of MPs or nanoplastics and their characteristics are important to warrant a comprehensive understanding of their environmental and ecological impacts. This review elaborates the principles and applications of diverse analytical instruments or techniques for separation, characterization and quantification of MPs in the environment. The strength and weakness of different instrumental methods in separation, morphological, physical classification, chemical characterization and quantification for MPs are critically compared and analyzed. There is a demand for standardized experimental procedures and characterization analysis due to the complex transformation, cross-contamination and heterogeneous properties of MPs in size and chemical compositions. Moreover, this review highlights emerging and promising characterization techniques that may have been overlooked by research communities to study MPs. The future research efforts may need to develop and implement new analytical tools and combinations of hyphenated technologies to complement respective limitations of detection and yield reliable characterization information for MPs. The goal of this critical review is to facilitate the research of plastic particles and pollutants in the environment and understanding of their environmental and human health effects.

Optical transmission spectra study in visible and near-infrared spectral range for identification of rough transparent plastics in aquatic environments

Erosion of microplastics due to residence time in aquatic environments causes roughening of the microplastic. Unfortunately, currently used measurement methods do not provide information on the surface roughness of the microplastic embedded in water. In this study we propose a novel method by using transmittance to get information on the magnitude of the surface roughness of microplastics and to rank microplastics by thickness. For such a purpose, we studied optical properties such as dispersion, absorption of both plastics and water in the partial spectral range of visible light (Vis), transmission and scattering of light by plastic sheets, as well as, the calculated sample thickness in the Vis region. These were explored for the detection of both smooth and roughened plastic sheets immersed in water. Moreover, by using the transmission spectrum and refractive index of both plastic and water it is possible to estimate the average surface roughness of plastic samples. Our results suggest that the optical properties in the Vis region offer an interesting way for the detection of both rough and smooth plastic sheets and for ranking the type of plastics in an aquatic environment.

Nearshore spatio-temporal sea surface trawls of plastic debris in the Balearic Islands

Nearshore sea-surface manta trawls were carried out monthly at seven sites along the coastline of Mallorca in the Balearic Islands in the Western Mediterranean Sea. Plastic marine debris was present in all trawls (n = 63) with an overall average abundance of 858,029 ± 4,082,964 items/km² (mean ± standard deviation) and weight of 4,520 ± 22,806 g(DW)/km² and the micro-plastic fraction (74%) dominating the size class. Polyethylene (LDPE and HDPE) was the most common polymer (70%) with high spatial heterogeneity, especially along the north-western coast. August showed almost two-fold as much plastic as the other months, and the number of items decreased significantly with distance from the coastline. A positive correlation was found with the fractal dimension of the coastline indicating higher coastal plastic debris retention in areas with a higher fractal dimension and backtracking simulations indicated that marine litter was mainly locally sourced. Overall results indicate a significant small scale variability of nearshore coastal marine plastic in the Balearic Islands.

Spatial-temporal distribution of microplastics in surface water and sediments of Maozhou River within Guangdong-Hong Kong-Macao Greater Bay Area

Concerns over the negative impacts of microplastics on human health have led to growing attention on the occurrence of microplastics in aquatic environment. Recent studies have extended their focus from marine to inland waters, especially on the spatial-temporal distribution of the microplastics in urban rivers. In this study, Maozhou River, the largest river in Shenzhen, a tributary of the Pearl River, was selected as a representative inland waterway of Guangdong-Hong Kong-Macao Greater Bay Area. The spatial-temporal investigation was performed on microplastics in the surface water and sediments of 17 sites along the mainstream of the Maozhou River. Results show that microplastics were widely and unevenly distributed along the river and reached the high abundances on the site most intensively surrounded by industries as well as the sites downstream. The abundances in dry season ranged from 4.0 ± 1.0 to 25.5 ± 3.5 items·L^-1 in water and 35 ± 15 to 560 ± 70 item·kg^-1 in sediments, which were relatively higher than those observed in the wet season (water: 3.5 ± 1.0 to 10.5 ± 2.5 items·L^-1; sediments: 25 ± 5 to 360 ± 90 item·kg^-1; p value < 0.05). The dominant types of the microplastics were identified as: PE Polyethylene (PE, water: 45.0%, sediments: 42.0%), polypropylene (PP, water and sediments: 12.5%), polystyrene (PS, water: 34.5%; sediments 14.5%) and polyvinyl chloride (PVC, water: 2.0%; sediments: 15%). Moreover, metals like Al, Si, Ca were discovered on the rough surface of the microplastics, indicating the interactions between the microplastics and the aquatic environment. Through a comprehensive comparison with other major inland waters in China, this work provides valuable data on the microplastics pollution of a representative inland water in the Greater Bay Area, and will further contribute to a better understanding on the land-based input of microplastics from the intensively affected inland waters.

An unintended challenge of microplastic pollution in the urban surface water system of Lahore, Pakistan

Plastics are widely considered to be a major threat particularly in the urban areas owing to extensive use of plastic products. The current study is the first investigation to highlight the microplastics (MPs) pollution from the freshwater (Ravi River) located in the predominant urban center, i.e., Lahore, Pakistan. The concentration profile was quantified from surface water (n = 19) and sediments (n = 19) collected from different drains and canals of predominant freshwater resources in Lahore, Pakistan. The highest content of MPs was observed in the sullage carrier with mean concentration of 16,150 ± 80 MPs/m³ and 40,536 ± 202 MPs/m² in the water and sediments respectively. The lowest level was detected in the link canals with mean concentration of 190 ± 141 MPs/m³ in the water and 683 ± 479 MPs/m² in the sediments. The proportion of large size MPs (300 μm-5 mm) was maximum in the upstream section of Ravi river, whereas fine size MPs (50-150 μm) were dominant in the downstream section. In terms of shapes, the fragments were predominant with a relative abundance of 56.1% and 83.1% followed by fibers with a relative abundance of 38.6% and 11.8% in the water and sediments respectively. The chemical composition analysis showed that most of the fibers, fragments, and beads were polyethylene while the sheets were composed of polypropylene. Nevertheless, the foams isolated from the samples were composed of polystyrene. Within 24 h, about 2.4 ± 2.4 billion microplastic pieces were estimated to be transported from a single water channel into the river. The highest discharge of MPs was estimated from the sullage carrier with about 7 billion pieces/day.

Impact of Microplastic Fibers from the Degradation of Nonwoven Synthetic Textiles to the Magdalena River Water Column and River Sediments by the City of Neiva, Huila (Colombia)

Magdalena River surface water and shoreline sediments were sampled for microplastic particles at three locations in the city of Neiva, Colombia: upstream, city center, and downstream of the raw wastewater outflow. The absence of an industrial and manufacturing sector in Neiva provided an opportunity to assess the impact of upstream agricultural practices, as well as municipal activities such as wastewater outflow and laundry washing, on the quantity, polymer composition, and morphology of microplastic particles produced per capita and entering a river system. Microplastic particle concentrations increased with downstream distance, with microfiber concentrations ranging from 0.097 to 0.135 fibers/L in the river water and 25.5 to 102.4 fibers/kg in shoreline sediment. Microplastic fragment concentrations were 0.013–0.028 fragments/L in surface water and 10.4–12.7 fragments/kg of sediment. Raman microscope and scanning electron microscopy identified the relative composition of the polymers comprising the microplastic particles was similar regardless of sampling site or whether the sample was collected from the surface water or shoreline sediments, with polypropylene and polyethylene comprising at least 75% of the total polymers in all samples. Average fiber widths of < 20 µm in all but one sample, along with the lack of acrylic and polyester fibers used predominantly in woven synthetic textiles, indicated that the degradation of nonwoven synthetic textiles is the predominant origin of these microplastic fibers in the Magdalena River.

Microplastic pollution in deep-sea sediments and organisms of the Western Pacific Ocean

Microplastics are ubiquitous in marine environments. Sediments and marine organisms are recognized as the carriers and final destinations of microplastics. However, research on the concentration and abundance of microplastics in deep-sea sediments and organisms is limited. In this study, samples of sediments and organisms were collected from deep-sea locations of the western Pacific Ocean, with the depth ranging from 4601 m to 5732 m. Microplastics were extracted from the samples and analyzed by micro-Fourier-transform infrared spectroscopy. The average abundance of microplastics in the sediments was 240 items per kg dry weight of sediment. The microplastics were predominantly fibrous in shape (52.5%), blue in color (45.0%), and less than 1 mm in size (90.0%). The most commonly detected polymers were poly(propylene-ethylene) copolymer (40.0%) and polyethylene terephthalate (27.5%). The concentrations of polychlorinated biphenyls (PCBs), which are representatives of persistent organic pollutants, in the pore water of sediment samples were also investigated. A significant correlation between the distribution of microplastics and the PCB concentrations in sediments was found (P = 0.016). Microplastics were also detected in deep-sea organisms (i.e., Crinoidea, Pheronematidae, Ophiuroidea, and Gammaridea) in the sampling region, with an abundance of 0-3 items per individual biological sample. This assessment of microplastics in deep-sea sediments and benthic organisms of the western Pacific Ocean confirms that microplastic pollution exists in the deep-sea ecosystems of this region.

The distribution, characteristics and ecological risks of microplastics in the mangroves of Southern China

During the production, use and disposal of plastic products, microplastics (MPs) are dispersed into the surrounding environment and have inevitable impacts on mangrove ecosystems in estuaries and offshore areas. In the mangroves of Southern China, the systematic evaluation of the distribution, characteristics and ecological risks of MPs is lacking. In this study, surface sediments (0-5 cm depth) were collected from six representative mangroves in China to explore MP contamination and its associated ecological risk. Based on the results, MP concentrations of MPs in mangrove sediments were as follows: FT (2249 ± 747 items/kg), ZJ (736 ± 269 items/kg), DF (649 ± 443 items/kg), DZG (431 ± 170 items/kg), YX (424 ± 127 items/kg), and FCG (227 ± 173 items/kg). The higher MP concentration in the Futian mangrove was mainly related to inputs from the Pearl River, the third largest river in China. The predominant shape, colour, and size of MPs were fibrous, white-transparent, and 500-5000 μm, respectively. The main MP polymer types were polypropylene, polyethylene, and polystyrene. Degradation artefacts were present on surface of MPs as well as metallic and non-metallic elements. MPs concentration in mangrove sediments increased with increasing social-economic development of surrounding districts, which indicated the clear influence of anthropogenic activity on MP pollution in these mangroves. Furthermore, total organic carbon (TOC) and silt content were positively associated with MPs (P < 0.01), indicating a facilitatory role in deposition of MPs in mangroves. Based on a comprehensive evaluation using the potential ecological risk factor (E_i), potential ecological risk (RI), polymer risk index (H) and pollution load index (PLI), MPs were found to present ecological risks in these mangroves, with the highest risk occurring in the Futian mangrove.

Microplastics in seawater: sampling strategies, laboratory methodologies, and identification techniques applied to port environment

The European Interreg Italy-France 2014-2020 Maritime Project SPlasH! (Stop to Plastics in H₂O!) focused on the study of microplastics (MPs) in the marine port environment to evaluate their presence, abundance, and mechanisms of diffusion to the open sea. In the framework of this project, a worldwide review of 74 studies was carried out, providing an overview of MP investigation techniques, focusing on sampling strategies, laboratory methodologies, and identification of MPs collected in seawater, and specifically evaluating their applicability to the marine port environment. Nets were the most commonly used device for MP surface sampling, but their use can be difficult in narrow spaces within the port basins, and they must be coupled to discrete sampling devices to cover all port basins. In the laboratory, density separation (NaCl, ZnCl₂, NaI, sodium lauryl sulfate (SLS)), filtration (polycarbonate, polyamide, glass, cellulose, ANOPORE inorganic membrane filters), sieving, visual sorting, and digestion methods (acidic, enzymatic, alkaline, oxidative) were used to separate MPs from seawater. Digestion becomes essential with water samples with great inorganic and organic loads as deriving from a port. Although many studies are based only on visual MP identification under a microscope, analytical identification techniques unequivocally determine the particle nature and the identity of the plastic polymers and are necessary to validate the visual sorting of MPs. Fourier-transform infrared spectroscopy (FTIR) is the most used analytical identification technique.

Microplastics in seawater: sampling strategies, laboratory methodologies, and identification techniques applied to port environment

The European Interreg Italy-France 2014-2020 Maritime Project SPlasH! (Stop to Plastics in H₂O!) focused on the study of microplastics (MPs) in the marine port environment to evaluate their presence, abundance, and mechanisms of diffusion to the open sea. In the framework of this project, a worldwide review of 74 studies was carried out, providing an overview of MP investigation techniques, focusing on sampling strategies, laboratory methodologies, and identification of MPs collected in seawater, and specifically evaluating their applicability to the marine port environment. Nets were the most commonly used device for MP surface sampling, but their use can be difficult in narrow spaces within the port basins, and they must be coupled to discrete sampling devices to cover all port basins. In the laboratory, density separation (NaCl, ZnCl₂, NaI, sodium lauryl sulfate (SLS)), filtration (polycarbonate, polyamide, glass, cellulose, ANOPORE inorganic membrane filters), sieving, visual sorting, and digestion methods (acidic, enzymatic, alkaline, oxidative) were used to separate MPs from seawater. Digestion becomes essential with water samples with great inorganic and organic loads as deriving from a port. Although many studies are based only on visual MP identification under a microscope, analytical identification techniques unequivocally determine the particle nature and the identity of the plastic polymers and are necessary to validate the visual sorting of MPs. Fourier-transform infrared spectroscopy (FTIR) is the most used analytical identification technique.

Microplastic pollution in water, sediment, and fish from artificial reefs around the Ma'an Archipelago, Shengsi, China

In this study, the occurrence and distribution of microplastics in artificial reefs around the Ma'an Archipelago, a national marine ranching area in China, were investigated. The abundance of microplastics ranged from 0.2 ± 0.1 to 0.6 ± 0.2 items L^-1 in surface water, 30.0 ± 0.0 to 80.0 ± 14.1 items kg^-1 dry weight in the sediment, and 2.3 ± 1.5 to 7.3 ± 3.5 items individual^-1 in fish. Most of the detected microplastics were fiber-shaped, blue or transparent, and smaller than 1 mm. Polyethylene, polypropylene, and poly(ethylene:propylene:diene) copolymer were the most abundant polymer types in the surface water samples, whereas cellophane was dominant in the sediment and fish. The appearance of microplastic pollution around the artificial reefs could be attributed mainly to the activities of the fisheries in the area, whereas the microplastic ingestion by fish was affected by the extent of microplastic contamination of the sediment. The results highlight the widespread presence of microplastics in the water, sediment, and biota of the artificial reefs around the Ma'an Archipelago, thereby improving understanding of the environmental risks posed by microplastics to marine artificial reef ecosystems and fisheries in general.

Microplastics in aquatic environments: Occurrence, accumulation, and biological effects

Microplastics, whether originating directly from industrial and household products or from the degradation of larger plastics, are currently of intense global concern. These particles are present in aquatic environments in high concentrations and may adversely affect aquatic organisms. An additional concern is the ability of microplastics to adsorb inorganic and organic pollutants and subsequently liberate them into marine and freshwater systems. In this review, we report on the occurrence and abundance of microplastics in the global aquatic environment. We then consider the accumulation (uptake, distribution, and elimination) of microplastics in aquatic organisms and the important factors that lead to bioaccumulation. The effects of microplastics on aquatic organisms of different trophic levels are also discussed. Several studies have shown that the size, shape, and surface physicochemical characteristics of microplastics are essential determinants of their biological effects. Finally, we examine the combined effects of microplastics and other pollutants, including persistent organic pollutants and heavy metals. Our review concludes by suggesting future lines of research based on the remaining knowledge gaps in microplastic research.

Spatial and seasonal distribution of microplastics on sandy beaches along the coast of the Hengchun Peninsula, Taiwan

Here we present the first report on microplastic pollution on the beaches along the coast of the Hengchun Peninsula, which is one of the major tourist attractions in Taiwan. By using a standard operating procedure, sand samples were collected from eight beaches in June and November in 2017, and the microplastics in the sand samples were quantified and characterized in the laboratory. The average density of microplastics ranged from 80 to 480 particles/kg dry weight sand. There was no apparent seasonal difference but there were significant spatial differences among sampling sites. No significant difference in microplastic levels was observed among the west, south, and east coasts, but microplastic density was higher on beaches with higher tourism activity levels. The most abundant type of microplastics was fiber (>97%) and the most common color was white/transparent (57%). In addition, using a Fourier Transform Infrared (FTIR) spectrophotometer we identified microplastics as polyethylene (PE) and polypropylene (PP). Our results show that microplastics are ubiquitous along the coast of the Hengchun Peninsula, and the major factor associated with the abundance of microplastics is tourism activity.

The marine nano- and microplastics characterisation by SEM-EDX: The potential of the method in comparison with various physical and chemical approaches

The marine microplastic (MMs) is an interdisciplinary problem. The polymer debris are ubiquitous (soil, hydrosphere, atmosphere) and the majority ends, transported by the freshwaters, in the global ocean system: from pelagial waters, surface gyres and benthos up to the animals at different trophic levels. Their quantitative, qualitative and eco-toxicological analyses, based on analytical, physical and chemical methods, are still a challenge due to the complex matrices, materials weathering, limited concentration, and size. Moreover, further fragmentation due to the waves and UV radiation leads to the constant increase of their surface. The aim of this article is to present the advantages, drawbacks and future perspectives of using SEM-EDX method in the analyses of marine polymer debris from macro to the nanoscale. Theoretical issues are presented in comparison to the commonly used approaches. The practical aspects will be discussed based on case studies. Examples of the results, high-resolution SEM pictures are included.

Environmental implications of microplastic pollution in the Northwestern Pacific Ocean

Microplastics (MPs) contamination has been recognized as one of major threats to coastal marine environments. Although studies evidenced severe MPs contaminations to the Pacific Ocean, environmental implications of MPs concentrations, distributions, and characteristics have not been evaluated in sufficient detail. Here, we report on the distribution, abundance, and characteristics of MPs at the surface of the Northwestern Pacific Ocean, from which environmental implications are assessed. A manta trawl with a mesh size of ~330 μm and a rectangular net opening of 0.45 × 1 m was used to collect MPs samples on May 11-June 3, 2018. The MPs samples were sequentially isolated, digested, filtered, and characterized using an optical microscope, micro-Raman spectroscopy, and scanning electron microscopy. The results indicate the heterogeneity in abundance, shapes, color, and sizes of MPs. The study provides strong environmental implications such as sources, environmental degradation, residence time, transportation routes, and biological interactions.

Microplastic pollution in the sediments of Sidi Mansour Harbor in Southeast Tunisia

Despite the increasing interest in microplastic (MP) research, the accurate prevalence, distribution and fate of these materials in the environment is yet poorly known and, consequently, a focus of debate. Hence, to better ascertain the presence of microplastics in specific environments, samples from 35 random sites distributed across a 4200-meter long section from the area of Sidi Mansour, Sfax-Tunisia, were collected and analyzed. MPs were extracted, digested with potassium hydroxide and dyed with Eosin B, for visual microscopy counting and sorting. Polymer composition and surface morphology were identified by FTIR-ATR spectroscopy and SEM microscopy. Total abundances ranged from 252 to-5332 particles per m² where fragments and granules were the most frequent types of microplastics. These findings highlight the considerable presence of these materials in the studied harbor region and underscore the density dependence on the distribution and occurrence of MPs and how these tend to accumulate in the sandy sediments.

Microplastics in special protected areas for migratory birds in the Bay of Biscay

Plastic pollution is a major ecological catastrophe that endangers vulnerable species. Small plastic fragments and filaments enter the food web in the ocean threatening marine species health. Here microplastics between 0.5 and 5 mm were quantified from eight beaches of southwest Bay of Biscay (Spain) within Natura-2000 Special Protection Areas for birds. Sand samples were taken using a randomized quadrat-based protocol. Between 145 and 382 particles per kg of dry sand were found, which is relatively high in comparison with other European beaches. Microfibers were more abundant than microplastics. PERMANOVA revealed a significant effect of the beach location (inside versus outside the estuary). Open beaches contained a higher microplastic density than sheltered ones suggesting that many beached microplastics come from the ocean. Birds are at risk in the studied protected spaces as revealed from high concentrations of fibres in depositions of European shag and gulls.

Dynamic of small polyethylene microplastics (≤10 μm) in mussel's tissues

MPs' uptake and tissue accumulation were investigated in mussel exposed to a single dose (2.85 mg ind^-1, 3 mg l^-1) of a heterogeneous mixture of irregularly shaped particles of HDPE (mainly ≤10 μm), followed by a 7 days depuration period. The results showed that mussels efficiently cleared MPs from water during exposure, and that MPs were accumulated in digestive gland and gills during depuration. In digestive gland, the amount and size of the MPs accumulated decreased with time, indicating a slower processing and elimination of small MPs than of larger ones. In gills, MPs' burdens increased with time, the MPs accumulated were the smallest ones, suggesting the translocation of small MPs from the digestive system to the gills. The hazardous potential of the smaller fraction of MPs (≤4 μm) underlined that more focus should be directed towards the accumulation and effects of this fraction of MPs in the marine environment.

A novel method enabling the accurate quantification of microplastics in the water column of deep ocean

Little information concerning microplastic (MP) pollution in the deep ocean is currently available, and a huge gap exists between sampling methodology and obtaining an authentic dataset. Verified sampling methodology is a fundamental step in the accurate determination of MP pollution in the pelagic environment, of which sample volume is a crucial factor. To address this methodological challenge, in situ filtration technology, a novel sampling method for microplastics in the water column, was proposed and investigated. On 27 April 2019, we took the East China Sea as a typical example in order to determine the relationship between sample volume and MP abundance. Analysis indicated that the filtrated volume has an impact on MP quantification and significant exponential regression between the sample volume and MPs was observed. This investigation indicated that a small volume sample could easily lead to MP overestimation, with at least 8 m³ water required to obtain reliable data.

Microplastics in the Coral Reef Systems from Xisha Islands of South China Sea

The impacts of microplastics on coral reefs are gaining attention due to findings that microplastics affect coral health. This work investigated the distribution and characteristics of microplastics in the seawater, fish, and corals in 3 atolls from the Xisha Islands of South China Sea. In the seawater samples, microplastics were detected in the outer reef slopes, reef flats, and lagoons with abundances ranging from 0.2 to 11.2, 1.0 to 12.2, and 1.0 to 45.2 items L^-1, respectively. Microplastic abundance was 0-12.0 items individual^-1 (0-4.7 items g^-1) in fish and 1.0-44.0 items individual^-1(0.02-1.3 items g^-1) in coral. The predominant shape and polymer of microplastics in seawater, fish, and coral were fibrous rayon and polyethylene terephthalate (PET). Microplastic sizes primarily ranged from 20-330 μm in both the seawater and fish, while there were relatively more 1-5 mm microplastics in the corals. The shape, size, color, and polymer type distribution patterns of microplastics in seawater more closely resembled those in fish gills than those in fish gastrointestinal tracts or coral samples. This study shows that microplastics are abundant in these coral reef systems and they are captured by fish or "trapped" by corals.

Distribution characteristics of microplastics in the seawater and sediment: A case study in Jiaozhou Bay, China

As a newly identified form of pollutant in the ocean, microplastics are receiving more and more attention from researchers. In order to evaluate the potential impact of microplastics, it is important to have comprehensive knowledge of the current microplastic situation. This study analyzed the abundance, polymer type, size, shape and color of microplastics in the seawater and sediments of Jiaozhou Bay, China, a semi-enclosed bay highly affected by surrounding human activities. Qualitative and quantitative analysis of microplastics were carried out using stereo microscope and attenuated total reflection micro-Fourier transform infrared spectrometer (ATR-μ-FT-IR). The abundance of microplastics in the bay seawater samples ranged between 20 items/m³ and 120 items/m³. The abundance of microplastics in sediment samples in the bay were between 7 items/kg d.w. and 25 items/kg d.w. The microplastics were mainly in black and blue colors with fiber being the dominant shape in all samples. All microplastics identified were smaller than 4 mm in this study. Polyethylene terephthalate (PET) was the main type of microplastics, followed by polypropylene (PP) and polyethylene (PE). Both the abundance and types of microplastics show positive correlations between the seawater and sediment samples. Microplastic polymer types in the bay showed close match to the polymer types in the estuaries. Relatively higher abundance of microplastics tended to be found in the area where there were residual currents and sediment transport trends. Our study showed riverine input is an important contributor to the microplastics in the bay and physical factors such as residual currents would greatly affect the aggregation of microplastics.

Microplastic pollution in the rivers of the Tibet Plateau

The Tibet Plateau, the so-called Third Pole of the world, is home to the headstreams of many great rivers. The levels of microplastic pollution in those rivers, however, are unknown. In this study, surface water and sediment samples were collected from six sampling sites along five different rivers. The surface water and sediment samples were collected with a large flow sampler and a stainless steel shovel, respectively. The abundance of microplastics ranged from 483 to 967 items/m³ in the surface water and from 50 to 195 items/kg in the sediment. A large amount of small, fibrous, transparent microplastics were found in this study. Five types of microplastics with different chemical compositions were identified using micro-Raman spectroscopy: polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyamide (PA). These results demonstrate that rivers in the Tibet Plateau have been contaminated by microplastics, not only in developed areas with intense human activity but also in remote areas, where microplastic pollution requires further attention.

Microplastics abundance and characteristics in surface waters from the Northwest Pacific, the Bering Sea, and the Chukchi Sea

Microplastics (MPs) in the Arctic Ocean have gained considerable attention due to its ubiquity and impacts within ecosystems. However, little information is available on MPs in the Pacific section of the Arctic Ocean. The present study determined the abundance, distribution, and composition of MPs in surface waters from the Northwestern Pacific, the Bering Sea, and the Chukchi Sea. The MPs abundances varied from 0.018 items/m³ to 0.31 items/m³, with a mean abundance of 0.13 ± 0.11 items/m³. The highest level of MPs was found in the Chukchi Sea. Of all of the detected MPs, polyethylene terephthalate (PET) accounted for the largest proportion of MPs, and fiber was predominant with regard to the total amount. Our results highlighted that the Arctic Ocean is becoming a hotspot for plastic pollution, and the risks posed by MPs need to be paid closer attention in future investigations.

Prevalence of microplastic pollution in the Northwestern Pacific Ocean

People are increasingly aware of ubiquitous microplastic (MP) pollution in the world's ocean due to its far-reaching harmful impacts on marine ecosystem and potential hazards to human health, yet surprisingly comparatively limited studies about the abundance, source, transport, and fate of MPs in the Northwestern Pacific Ocean are available. We conducted the field survey of MPs pollution at the surface of the Northwestern Pacific Ocean between August 25 and September 26, 2017. MPs were collected from 18 sampling stations in the Northwestern Pacific Ocean using a manta trawl net with a mesh size of ∼330 μm and a rectangular net opening of 0.45 × 1 m. The abundance, shape, color, size, chemical composition, and surface morphology were characterized using light microscopy, μ-Raman spectroscopy, and scanning electron microscopy (SEM). The results show surface MPs at concentrations ranging over two orders of magnitude (6.4 × 10² to 4.2 × 10⁴ particles km^-2) and a mean abundance of 1.0 × 10⁴ particles km^-2. The most concentrated MPs were found at XTJ3-9, which may be associated with the convergence of surface currents collectively affected by the Kuroshio and its extension, adjacent eddies, and flow regimes. Polyethylene accounts for 57.8% of enumerated MPs, followed by polypropylene (36.0%) and nylon (3.4%). Pellets, sheets, lines, and films are major forms which may be linked to the breakdown of larger particles, aging processes, and movement over long distances by prevailing currents. Four possible MPs migration pathways were proposed based on the source-specific distribution, chemical fingerprints, size distribution patterns, and the observed physical oceanographic parameters.