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This study investigated the presence of microplastics (MPs) in mussels from an urbanized bay in Korea, focusing on intra-annual variation. The average MP concentration was 0.36 ± 0.14 n/g w.w. (1.24 ± 0.56 n/individual). MPs were detected throughout the year with minor monthly variation and no significant monthly changes. Although there was no correlation between MP concentration in mussel and seawater, a positive relationship was observed when normalizing MPs to mussel's condition index (except for July). Polypropylene, polyethylene and acrylate polymer were dominant MPs, with high-density polymers comprising 59 % of the total. Most MPs were fragments and particles <200 μm. This study indicates that strict time restrictions for mussel sampling may not be necessary to assess MP levels in this bay. Additionally, considering MPs in seawater, biological conditions of mussel may be essential for understanding variations in MP levels in mussels. Including small MPs (<200 μm) and high-density polymers in MP assessment is recommended. • One-year monthly monitoring of microplastics (MPs) using mussel was performed. • MPs were detected year-round in mussel with minor monthly variation. • High-density polymers and MP <200 μm were abundant. • MP characteristics between mussel and seawater were similar. • MPs in seawater and biological conditions may co-influence in MP levels in mussel. [ABSTRACT FROM AUTHOR]

Abstract Microplastic contamination in marine organisms is a growing environmental issue with implications for seafood safety. Among marine organisms, shellfish are considered to be an important route of human exposure to microplastics because they filter a large volume of seawater while feeding and, thus, accumulate microplastics from seawater; furthermore, they are consumed whole, without gut removal. In this study, a market survey was carried out to understand microplastic contamination in domestic bivalves sold in fishery markets in three major cities of South Korea. Four popular bivalve species, oyster (Crassostrea gigas), mussel (Mytilus edulis), Manila clam (Tapes philippinarum) and scallop (Patinopecten yessoensis), were selected as monitoring species, which together account for 79–84% of total shellfish consumption in Korea. The mean concentration of microplastics in these four species was 0.15 ± 0.20 n/g and 0.97 ± 0.74 n/individual. Fragments and particles smaller than 300 μm were dominant shape and size, accounting for 76% and 65% of total microplastics, respectively. Polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyester were the major polymer types. Interestingly, differing polymer compositions were observed according to the culture methods and habitat characteristics of each species. PS was found in high proportions in oysters and mussels cultured in the upper layer of the water column, while the proportions decreased and those of polyester increased in Manila clams and scallops that were cultured in intertidal sediments or the middle and bottom layers of the water column. The annual dietary intake of microplastics by the Korean population via shellfish consumption was estimated as 212 n/person·year. Our results suggested that microplastic pollution is widespread in commercial bivalves and we recommend a systematic and integrative market-basket survey to clarify the current status of human exposure to microplastics. Graphical abstract Image 1 Highlights • Microplastic (MP) contamination in bivalves purchased from markets was studied. • MP contamination was widespread in market bivalves. • Shape and polymer type of MP were influenced by farming method of each species. • The dietary intake of MP by the Korean population via shellfish was estimated. • Seafood consumption can be a route of MP exposure for humans. Microplastic contamination in market bivalves from South Korea was investigated to understand human exposure to microplastics via seafood consumption. [ABSTRACT FROM AUTHOR]

Seafloor sediments are an important sink for microplastics (MPs), and the vertical profile of MP accumulation in a sediment core represents historical pollution trends. In this study, MP (20–5000 μm) pollution in surface sediments of urban, aquaculture, and environmental preservation sites in South Korea was evaluated, and the historical trend was investigated using age-dated core sediments from the urban and aquaculture sites. The abundance of MPs ranked in the order of urban, aquaculture, and environmental preservation sites. Polymer types were more diverse at the urban site compared to other sites, and expanded polystyrene was dominant in the aquaculture site. An increase in MP pollution and polymer types was observed from bottom to top of cores, and historical trends of MP pollution reflect local influences. Our results indicate that the characteristics of MPs are determined by human activities, and MP pollution should be addressed according to the characteristics of each site. • The abundance of microplastic was in order of urban, aquafarm, and reference sites. • Characteristics of microplastic pollution well reflect the sea area use patterns. • Polymer composition of fiber was different between urban and aquafarm sites. • Increasing trend of microplastic pollution levels reflected surrounding sources. [ABSTRACT FROM AUTHOR]

Globally, sea turtles are at high risk of ingesting plastic. However, research on plastic ingestion by sea turtles in East Asia is scant, and no quantitative or qualitative investigation has been conducted in Korean waters. This study examined the plastic ingestion of sea turtles stranded, floating, or incidentally captured in Korean waters between 2012 and 2018. The quantity, shape, color, size, polymer type, and original usage of plastic debris (>1 mm) ingested by sea turtles were analyzed after being sorted from the gastrointestinal tracts of 34 turtles (21 loggerheads (Caretta caretta), 9 green turtles (Chelonia mydas), 2 leatherbacks (Dermochelys coriacea), and 2 olive ridleys (Lepidochelys olivacea)). The ingestion frequencies of greens, loggerheads, olive ridleys, and leatherbacks were 100%, 81%, 50%, and 50%, respectively. The mean amount of plastic ingested was 108 ± 253 mg/kg (38 ± 61 n/ind.). The ingested debris tended to be films and fibers (>80%), light in color (white and transparent; 65%), and light polymers (polyethylene, polypropylene, polypropylene [poly (ethylene:propylene)], expanded polystyrene; 93%). The original uses were identified for 187 pieces; single-use plastics (e.g., plastic bag and packaging) and fishing and aquaculture items (e.g., twine and net) were found to dominate. Green turtles (264 ± 433 mg/kg) ingested significantly higher amounts of plastic than loggerheads (72.8 ± 156 mg/kg). Green turtles ingested mostly fibers (51%), such as rope, twine, and net, while loggerheads ingested largely films (61%), such as plastic bags and packaging. Interspecies differences in quantities and shapes of ingested debris may be related to their distinct feeding habits and geographical range of movement. The present study demonstrates that sea turtles foraging in Korean waters are considerably affected by marine plastic debris, and indicates that proper waste management of single-use plastics and fishing gears is urgently needed to mitigate the damage that plastic debris causes to marine wildlife. [Display omitted] • Sea turtles inhabiting Korean waters are significantly affected by plastic debris. • Ingested plastics were mainly single-use and fishery items. • Plastic ingestion frequency and quantity were highest in green turtles. • Fibers and films were dominant in herbivore and carnivore turtles, respectively. • Sea turtles are key indicator species for assessing marine plastic pollution. [ABSTRACT FROM AUTHOR]

Microplastic pollution is emerging as a global environmental issue, and its potential for transferring hazardous chemicals to aquatic organisms is gaining attention. Studies have investigated the transfer of chemicals, mainly sorbed chemicals, through ingestion of microplastics by organisms, but limited information is available regarding chemical additives and uptake via the aqueous route through plastic leaching. In this study, we compared two bioaccumulation pathways of the additive hexabromocyclododecane (HBCD) by exposing mussels (Mytilus galloprovincialis) to two different sizes of expanded polystyrene (EPS): inedible size (4.2–5.5 mm) for leachate uptake and edible size (20–770 μm) for particle ingestion and leachate uptake. Over 10 days, the HBCD concentration increased significantly in mussels in the EPS exposure groups, indicating that EPS microplastic acts as a source of HBCD to mussels. The concentration and isomeric profiles of HBCD in mussels show that uptake through the aqueous phase is a more significant pathway for bioaccumulation of HBCD from EPS to mussels than particle ingestion. HBCD levels measured in EPS, leachate and exposed mussels from this study are environmentally relevant concentration. The fate and effects of chemical additives leached from plastic debris in ecosystem requires further investigation, as it may affect numerous environments and organisms through the aqueous phase. Image 1 • Additive HBCD uptake via EPS particle ingestion and EPS leachate were compared. • Mussels were exposed to edible and inedible sizes of EPS microplastics. • Aqueous leachate uptake is an important exposure route of EPS additives for mussels. • EPS microplastic acts as a source of plastic additives HBCD to mussel. Aqueous leachate uptake can be an important exposure route of microplastic additives for aquatic invertebrates. [ABSTRACT FROM AUTHOR]

This study assessed the ecological risk posed by microplastics in surface and subsurface seawaters in coastal, continental shelf, and deep-sea areas of South Korea. The target microplastics for risk assessment were specified as only non-spherical type microplastics in the size range 20–300 μm, because this type was predominantly observed in our study areas, and adverse biological effects have previously been reported. Exposure data for non-spherical microplastics were obtained from a previous study or were measured for microplastics of sizes down to 20 μm. A predicted no-effect concentration (PNEC) of 12 particles/L was derived by employing a species sensitivity distribution approach. Then the results were compared to the in situ observed concentrations at each site. The detected microplastic concentrations did not exceed the derived PNEC, i.e., the current pollution levels of fragment and fiber microplastics in the size range 20–300 μm would not pose a significant threat to the marine ecosystem in South Korea. However, predictions are that microplastic pollution will increase to 50-fold by 2100 at the current rates, and in this scenario, the microplastic concentration is expected to far exceed the derived PNEC values for marine ecosystems. It is therefore urgent to take precautionary actions to prevent a further increase in microplastic concentrations in these environments. Image 1 • Predicted no effect concentration (PNEC) for non-spherical microplastic was derived. • The microplastic concentrations in Korean marine water was lower than PNEC. • No ecological risk in Korean saltwater environments is suspected. • The microplastic concentration is predicted to well exceed PNEC value by 2100. • Actions to prevent a further increase in microplastic concentrations should be taken. Ecological risk assessment was conducted by matching size range and morphology of microplastics in both toxicity data and field monitoring data. [ABSTRACT FROM AUTHOR]

Bivalves are useful bioindicators of microplastic contamination in the marine environment for several reasons, such as extensive filter feeding activity, broad geographical distribution, and limited movement capability. This study conducted a nationwide monitoring of microplastic pollution along the Korean coasts using filter-feeding bivalves (including oyster, mussel, and Manila clam) as bioindicators to identify the national contamination level and characteristics of microplastics. Seawater sample was collected from the same sampling stations of oyster and mussel for comparison. Microplastics were widely distributed in both coastal bivalves and waters with mean concentrations of 0.33 ± 0.23 n/g (1.21 ± 0.68 n/individual) in oyster/mussel, 0.43 ± 0.32 n/g (2.19 ± 1.20 n/individual) in Manila clam, and 1400 ± 560 n/m3 in seawater. Despite the lack of significant relationship in the abundance of microplastics, their dominant features such as size, shape, color and polymer type were similar between bivalves and seawater. Fragments (69% for oyster/mussel, 72% for Manila clam, and 77% for seawater), particles smaller than 300 μm (96% for oyster/mussel, 83% for Manila clam, and 84% for seawater) and colorless (79% for oyster/mussel, 85% for Manila clam, 75% for seawater) were the dominant shape, size and color, respectively. The major polymer types were polypropylene, polyethylene, and polyester. The microplastic level in bivalves was relatively high in urbanized areas with a wide diversity of polymer types compared with those in non-urbanized areas, and the proportion of polystyrene in the Korean samples was abundant compared with other regions due to wide use of polystyrene products in Korea. Our result suggests that microplastic contamination is widespread in the Korean coastal environment, and bivalves can reflect the microplastic pollution characteristics of the surrounding waters where they live. Image 1 • Microplastic (MP) was widespread in bivalves and seawater from the Korea coasts. • Size, shape, and polymer type were similar between bivalves and nearby seawater. • Bivalves from urbanized areas exhibited high abundance and diversity of MP. A nationwide biomonitoring study was conducted to identify the national contamination level and characteristics of microplastics in Korea. [ABSTRACT FROM AUTHOR]

Plastic products contain numerous additive chemicals, which are present in large amount, and can be transferred to the marine environment. In this study, we quantified chemical additives and persistent organic pollutants (POPs) in marine plastic debris, along with their corresponding new plastic products (e.g., fishing gear, packaging material, and cigarette butts). The levels of chemical additives were significantly higher than those of conventional POPs in plastic samples, which was indicative of the widespread utilization of additives in plastics. New plastic products contained significantly higher additive concentrations than plastic debris, implying potential leaching during use or after disposal in the marine environment. In fishing gear materials, buoys generally contained high concentrations of antioxidants (280–91,000 ng/g). Polyvinyl chloride (PVC) rope used in aquaculture had the highest phthalate and bisphenol A (BPA) concentrations, and the second-highest ultraviolet radiation stabilizers. Rubber bars from the tire recycling used in aquaculture contained the highest 6PPD-quinone concentration, which is known to be responsible for salmon death. This is the first quantitative analysis of 6PPD-quinone in recycling tire, suggesting a need for chemical analysis of the tires itself, not only in environmental matrices. Compared to fishing gear materials, concentrations of the targeted chemical additives were relatively low in packaging material and cigarette butts, except for plastic bags. The concentration difference between new and debris was largest in PVC rope for aquaculture farm. It was estimated that 340–470 kg of phthalates and 140–194 kg of BPA are released into the sea from this PVC rope in Korean marine aquaculture. The study indicates that aquaculture fishing gear represents a significant source of chemical additives in the marine environment. It also suggests that exercising caution is crucial when considering the use of recycled plastics in aquaculture gear due to potential chemical contamination of the marine environment. [Display omitted] • First comprehensive quantification of plastic additives in fishing gears from Korea. • New products contained significantly higher additive contents than debris samples. • Fishing gears displayed greater additive contents compared to other plastic items. • High levels of hazardous chemicals in aquaculture gear with recycled plastic. • Fishing gear is a significant source of chemical additives in the marine environment. [ABSTRACT FROM AUTHOR]

Human activity is thought to affect the abundance and contamination characteristics of microplastics (MPs) in the environment, which may in turn affect aquatic species. However, few studies have examined the impact of coastal area use pattern on characteristics of MPs in coastal regions. In this study, we investigated MP contamination of abiotic matrices (seawater and sediment) and biotic matrices (bivalves and polychaetes) in three coastal regions characterized by different types of human activity, covering urban, aquafarm, and rural areas. MP abundance was higher in sediment from the urban site than in that from the rural site, but similar to that from the aquafarm site. In the abiotic matrices, different MP polymer compositions were observed among the three sites. Diverse polymers were found in marine matrices from the urban site, implying diverse MP sources in highly populated and industrialized areas. Polystyrene was more abundant in the aquafarm site, reflecting the wide use of expanded polystyrene aquaculture buoys. Polypropylene was more abundant at the rural site, probably due to the use of polypropylene ropes and nets in fishing activity. MP accumulation profiles in marine invertebrates showed trends similar to those exhibited by abiotic matrices, reflecting coastal area use patterns. These results indicate that marine MPs are generated from both land- and marine-based sources, and that the abiotic and biotic marine matrices reflect the MP characteristics. Image 1 • Microplastic (MP) contamination was compared in urban, aquafarm, and rural areas. • MP shape, size, and polymer type were examined in various marine matrices. • Coastal area use pattern and MP contamination were found to be closely related. • Diverse polymers were found in marine matrices, creek, and road dust from urban. • Marine-based activities are important contributors to MP contamination. [ABSTRACT FROM AUTHOR]

This is the first report to evaluate the potential effects of microplastics (MPs) on wild wharf roaches (Ligia exotica) in a shoreline habitant. L. exotica is an important plastic detritus consumer in coastal area. A survey was conducted from May to June in the years 2019 and 2020 in two South Korean nearshore sites: Nae-do (as MPs-uncontaminated) and Maemul-do (as MPs-contaminated). MPs (>20 μm in size) were detected highly in gastrointestinal tracts of the L. exotica from Maemul-do, at an average level of 50.56 particles/individual. They were detected in much lower levels in the L. exotica from Nae-do. at an average rate of 1.00 particles/individual. The polymer type and shape were dominated by expanded polystyrene (EPS, 93%) and fragment (99.9%) in L. exotica from Maemul-do. Especially, Hexabromocyclododecanes, brominated flame retardants added to EPS, have been detected highly in L. exotica from Maemul-do (630.86 ± 587.21 ng/g l. w.) than those of Nae-do (detection limit: 10.5 ng/g l. w). Genome-wide transcriptome profiling revealed altered expression of genes associated with fatty acid metabolic processes, the innate-immune response-activating system and vesicle cytoskeletal trafficking in L. exotica from Maemul-do. The activation of the p53 signaling pathway (which is related to proteasome, ER regulation and cell morphogenesis) is likely to be involved in the EPS-uptake of wild L. exotica. Four neurosteroids were also detected in head tissue, and cortisol and progesterone concentrations differed significantly in L. exotica from Maemul-do. Our findings also suggest that resident plastic detritus consumer might be a useful indicator organism for evaluating pollution and potential effects of environmental microplastics. [Display omitted] • This is the first study to clarify the toxic effects derived from MP contamination in L. exotica. • MP contamination was higher in L. exotica from Maemul-do (50.56 particles/individual). • Composition of MP was dominated by the expanded polystyrene in L. exotica from Maemul-do (93%). • Abundant MP concentration altered the metabolic and immune system. • Significant variated neurosteroids also might be caused by MP contamination. [ABSTRACT FROM AUTHOR]