How does bivalve size influence microplastics accumulation?

Exposure to plastic debris alters expression of biomineralization, immune, and stress-related genes in the eastern oyster (Crassostrea virginica)

The degradation of marine plastic debris poses a threat to organisms by fragmenting into micro- and nano-scale pieces and releasing a complex chemical leachate into the water. Numerous studies have investigated harms from plastic pollution such as microplastic ingestion and exposure to single chemicals. However, few studies have examined the holistic threat of plastic exposure and the synergistic impacts of chemical mixtures. The objective of this study was to measure changes in gene expression of gill and gonadal tissue of the eastern oyster (Crassostrea virginica) in response to plastic debris exposure during their first year, using RNA-seq to explore multiple types of physiological responses. Shell and polyethylene terephthalate plastic were used as substrate for the metamorphosis of larval oysters in a settlement tank. Substrate pieces were then transferred to metal cages and outplanted in pairs - shell cage and plastic cage - onto restoration reefs in the St. Mary's River, Maryland, USA. After 10 months of growth, the oysters were collected, gill and gonadal tissue removed, and sex identified. The tissues of six oysters from each sex and substrate type were then analyzed in RNA-seq. Both gill and gonadal tissue samples had altered expression of immune and stress-response genes in response to plastic exposure. Genes upregulated in response to plastic were enriched for gene ontology functions of proteolysis and fibrinolysis. Downregulated genes were involved in shell biomineralization and growth. One male oyster exposed to plastic had "feminized" gene expression patterns despite developing mature sperm, suggesting plastic leachate can alter gene expression and shift protandric individuals to develop as females. Plastic pollution may therefore reduce shell growth, initiate immune and stress responses, alter sex differentiation, and impact reproductive output of eastern oysters through changes in transcription.

Microplastics in the European native oyster, Ostrea edulis, to monitoring pollution-related patterns in the Solent region (United Kingdom)

Microplastics (MPs) are the most abundant type of debris in the marine environment, creating a significant threat to aquatic ecosystems due to their persistence, ability to absorb organic pollutants and potential ingestion by marine fauna. Shellfish are particularly vulnerable to MPs accumulation as they filter large volumes of seawater, and they become an important route for human exposure to these particles. This study, the first to examine MPs in European flat oyster (Ostrea edulis) populations, aimed to quantify these particles in the gill and digestive tissues of oysters from the Solent region (southern England). Enzymatic digestion using Proteinase-K was used in this study and MPs were identified in every oyster sampled to determine whether differences in abundance, type and size of MPs exist between locations. Oysters near urban areas contained significantly more MPs than those near rural areas. Fibres were the most prevalent type of MPs, with sizes varying across locations. The study found no significant differences in MPs presence between gills and digestive tissues, and an inverse correlation between the size of MPs and oyster size. The presence of MPs in wild O. edulis could be an additional threat to the survival of an already threatened species and may pose health risks for predatory species and human consumers of seafood. The use of O. edulis as a biomonitoring species for marine MPs pollution could help determine the extent, distribution and sources of MPs, potentially informing management strategies to reduce pollution.

Risk assessments of microplastic exposure in bivalves living in the coral reefs of Vietnam

This study aimed to assess the presence of microplastics in bottom sediment and bivalve species, including Pinna bicolor, Atrina vexillum, Saccostrea sp., and Pinctada margaritifera, living in coral reefs on Vietnam's Southern coastal. The average microplastic abundance were 0.45 ± 0.13 items/g of wet soft tissue weight or 5.60 ± 1.49 items/individual in bivalve samples and 294 ± 43 items/kg dry weight of sediment samples. The fragment shape, size smaller than 100 μm, and polyethylene, polyamide, cellophane and polyethylene terephthalate were identified as the predominant constituents of the microplastics. The pollution load and potential ecological risk index of microplastics were at a minor level, whereas the polymer hazard index was at a high level. Overall, this study provides a basis for assessing the risks posed by microplastics in the marine ecosystems of Vietnam.

First multi-compartment approach to microplastics in an urbanized estuary of Argentina: The case of Magallana gigas

This study assesses MP in water, sediment, gills, and digestive tract of the oyster Magallana gigas in three Bahía Blanca estuary sites, Argentina, using, Pollution Load Index (PLI) and SEM/EDX (Scanning Electron Microscopy with Energy-dispersive X-ray spectroscopy) and FTIR (Fourier-transform infrared spectroscopy) techniques. A total of 51 MPs were detected in water (mean: 16 items L-1) and 126 in sediments (mean: 1399 items Kg-1) with no significant differences between sites. In oysters, 186 MPs were found, with no significant differences in the MPs load between gills (mean: 2.41 items g-1 w.w), digestive tract (2.06 ± 2 items g-1 w.w), and the total tissues. Transparent fiber MPs were predominant, with cellulose, polyamides, polyethylene terephthalate and polyethylene being common polymers. SEM/EDX showed Si, Fe, Cl, Na, Ti, Al, K, Ca and suspended particulate matter on MP surfaces. The PLI indicated a low-risk level for estuary bivalves and water, suggesting minimal MPs impact.

Potential risks of accumulated microplastics in shells and soft tissues of cultured hard clams (Meretrix taiwanica) and associated metals

Microplastics (MPs) pose risks to both aquatic ecosystems and human health. This study investigated MPs in the shells and soft tissues of hard clams (Meretrix taiwanica) cultured in the inland waters of Taiwan. This study further developed two novel risk indices for assessing the potential ecological and health consequences of MPs. Moreover, the metal concentrations in the clam's soft tissues and the associated consumption health risks were investigated. Clamshells contained significant amounts of MPs with an average abundance of 16.6 ± 6.9 MPs/ind., which was higher than in the soft tissues (2.7 ± 1.7 MPs/ind.). The distribution and sizes of MPs in shells and soft tissues were similar, primarily small-sized (<2 mm, >99 %), blue (>65 %), and fibrous (>99 %). Dominant MP polymer types included rayon (83.5 %), polyethylene terephthalate (11.8 %), and polyacrylonitrile (3.6 %). The proposed MP potential ecological risk index indicates a higher potential ecological MP risk in soft tissues (302-423) than in shells (270-278) of the clams. The MP potential hazard risk index showed that the risk of exposure to MP through shellfish consumption decreased with age. The total hazard index (THI) value suggested negligible health hazards from metal exposure through shellfish consumption. Moreover, there was no significant correlation between MPs and metal concentrations in soft tissues, suggesting that metals bound to MPs contribute minimally to the total accumulated metals in clam's soft tissues. This study confirms the presence of MPs in clam shells and provides a novel tool to assess the potential ecological and health risks associated with MPs in shellfish.

Occurrence of microplastics in store-bought fresh and processed clams in Italy

Compared to the large amount of data on wild samples, only a few studies reported microplastic occurrence in store-bought bivalves in which the production chain can be the main contamination route. Microplastic occurrence was herein investigated in 100 samples of store-bought clams sold as fresh or processed (vacuum-frozen or in brine) in Italy. A 10 % KOH was used for soft tissue digestion and FT-IR spectroscopy for polymer identification. A total of 135 potential microplastics ranging in size between 20 μm and 5000 μm were enumerated estimating an annual dietary intake via clam consumption of 59.472 microplastics/person. No significant difference in the average abundance between the two commercial conditions was observed, while a prevalence of smaller particles was detected in processed samples suggesting a detrimental effect of cooking during production. Polyethylene (PE), polyethylene terephthalate (PET), and polystyrene (PS) were identified posing an overall low risk (class II). Microplastic occurrence in store-bought seafood requires additional and specific attention and future studies should investigate microplastic contribution linked to the production chain.

Quantification and characterization of microplastics ingested by mangrove oysters across West Africa

Microplastic ingestion by marine organisms presents a challenge to both ecosystem functioning and human health. We characterized microplastic abundance, shape, size, and polymer types ingested by the West African mangrove oyster, Crassostrea tulipa (Lamarck, 1819) sampled from estuaries and lagoons from the Gambia, Sierra Leone, Ghana, Benin, and Nigeria using optical microscopy and Fourier transform infrared (FTIR) techniques. A total of 780 microplastics were isolated in the whole tissues of the 250 oysters (n = 50 oysters per country). The abundance and distribution of microplastics in the oysters followed the pattern: the Gambia > Ghana > Sierra Leone > Nigeria > Benin. The Tanbi wetlands in the Gambia recorded the highest average of 10.50 ± 6.69 per oyster while the Ouidah lagoon in Benin recorded the lowest average of 1.80 ± 1.90 per oyster. Overall, microplastic numbers varied significantly (p < 0.05) among the five countries. Microfibers, particularly those within 1001-5000 μm size, dominated the total microplastic count with a few fragments and films. No spherical microplastics were isolated in the oysters. In the Sierra Leone and Benin oysters, fragments and films were absent in the samples. Microplastic between the 1001 and 5000 μm size class dominated the counts, followed by 501-1000 μm, 101-500 μm, and 51-100 μm. Five polymer groups namely polyethylene, polyester, nylon, polypropylene, and polyamide were identified across the five countries, with polyethylene occurring in oysters from all five countries and polyester occurring in all but the oysters from Nigeria. This diversity of polymers suggests varied sources of microplastics ingested by the studied oysters. The absence of microspheres across the five supports findings from other studies that they are the least ingested and highly egested by the oysters.

Mangrove mud clam as an effective sentinel species for monitoring changes in coastal microplastic pollution

The worldwide mangrove shorelines are experiencing considerable contamination from microplastics (MPs). Finding an effective sentinel species in the mangrove ecosystem is crucial for early warning of ecological and human health risks posed by coastal microplastic pollution. This study collected 186 specimens of the widely distributed mangrove clam (Geloina expansa, Solander, 1786) from 18 stations along the Leizhou Peninsula, the largest mangrove coast in Southern China. This study discovered that mangrove mud clams accumulated a relatively high abundance of MPs (2.96 [1.61 - 6.03] items·g-1) in their soft tissue, wet weight, as compared to previously reported levels in bivalves. MPs abundance is significantly (p < 0.05 or 0.0001) influenced by coastal urban development, aquaculture, and shell size. Furthermore, the aggregated MPs exhibit a significantly high polymer risk index (Level III, H = 353.83). The estimated annual intake risk (EAI) from resident consumption, as calculated via a specific questionnaire survey, was at a moderate level (990 - 2475, items·g -1·Capita -1). However, the EAI based on suggested nutritional standards is very high, reaching 113,990 (79,298 - 148,681), items·g -1·Capita -1. We recommend utilizing the mangrove mud clam as sentinel species for the monitoring of MPs pollution changing across global coastlines.

Do Antarctic bivalves present microdebris? The case of Livingston Island

Marine microdebris (MD) seem to be widespread in benthic invertebrates, even in the most remote areas of the planet such as Antarctica, although the information available is still very scarce. Here we provide a detailed quantification and characterization of the MD found on three common bivalve species (Aequiyoldia eightsii, Thracia cf. meridionalis, and Cyclocardia astartoides) inhabiting shallow areas in Johnsons' Bay, Livingston Island (South Shetland Islands, Antarctica) as a snapshot of the MD present. On average, these bivalves contained 0.71 ± 0.89 items per individual and 1.49 ± 2.35 items per gram, being comparable to the few previous existing studies in other Antarctic areas. Nearly half of the organisms analysed here (45.6 %), contained at least one item. No significant differences were found in the three bivalve species. As far as we know, this is the first study to analyse and compare MD in three bivalve species in the Antarctic Peninsula. Although our results indicate bivalves are as not as polluted as in other areas of the planet, this is remarkable since this is considered one of the last pristine areas of the world. Our results point to local activities as the main source of MD pollution in Livingston Island, although global pollution cannot be discarded. We believe this research provides a useful baseline for future studies and will contribute to develop policies and strategies to preserve Antarctic marine ecosystems from MD pollution.

Microplastic contamination in different shell length in Tivela mactroides (Born, 1778)

Microplastic identification and distribution throughout oceans has become a great concern due to its substantial uprising and its consequent interactions with marine biota. Microplastics can be absorbed and adsorbed by several marine species owing to their very small size. Among these organisms are bivalves, including ones used as food for humans. In this context, this research aims to understand the absorption scale of microplastics by Tivela mactroides according to their size and consequently life stage. Thus, T. mactroides mussels were collected at Camburi Beach (Brazil) and grouped into 30 different size classes from 06 to 35 mm. Later, 20 specimens from each size class (N = 600) had the soft tissues removed and a pool was performed through digestion with 10 % KOH solution. Results showed the presence of microplastics in all size classes of T. mactroides, evidencing that organisms from 06 mm can already be contaminated by microplastics and a tendency of the number of microplastics particles to increase as shell size increases. Furthermore, the amount of blue filament-type MPs was significantly higher than the other types and colors. Additionally, analyzes performed by Raman spectroscopy showed that the blue filaments have a PET composition. Finally, larger individuals presented larger quantities of MPs, as well as larger filaments. This might suggest that there are differences between the assimilation of the size of MPs in the different size classes, i.e. that size makes a difference.

Bioaccumulation, microbiome composition and immunity, and epigenetic signatures associated with exposure to spherical, fibrous, and fragmented microplastics in the mussel Mytilus galloprovincialis

Microplastic (MP) pollution has become a major global concern due to the widespread use and discharge of plastics into the environment. However, very few studies have assessed the potential variations in the toxicity of MPs according to their shape and size. Therefore, our study sought to identify the biotoxic effects of spherical, fiber-shaped, and fragment-shaped polyethylene terephthalate MPs of different sizes at different concentrations on the Mediterranean mussel Mytilus galloprovincialis. The survival rate after exposure to small-sized MPs was lower than that observed for the larger type MPs. Bioaccumulation of MPs was different depending on the exposure periods and MP shapes. Interestingly, the fiber-shaped MPs underwent morphological modifications in the mussel body upon uptake. MP exposure also increased the global DNA methylation levels (i.e., an epigenetic signature), expression of the microbiota immunity-related toll-like receptor gene, and alteration of the gut microbial composition in the mussel. These findings indicated that MPs of different shapes and sizes at different concentrations can alter the bioaccumulation sensitivity of mussels according to the exposure periods, and the balance of gut immunity and epigenetic process. Furthermore, our results demonstrated that MPs of different shapes, particularly fiber types, can undergo morphological modification in mussel tissues, thus posing a hazardous threat.

First Record of Microplastic Contamination in the Non-Native Dark False Mussel Mytilopsis leucophaeata (Bivalvia: Dreissenidae) in a Coastal Urban Lagoon

Microplastic contamination is a global concern due to its conspicuous presence in aquatic ecosystems and its toxic nature to environmental and human health. False mussels are among the most notable fresh- and brackish water invaders. The invasive Mytilopsis leucophaeata in Rodrigo de Freitas Lagoon-RFL (Rio de Janeiro, Brazil) is the most abundant macrofaunal invertebrate, widely established and distributed throughout the lagoon. This study aimed to assess microplastic contamination in this invasive filter feeder and evaluate its potential use as a bioindicator. Agglomerates (~100 mussels) were manually collected using a stainless-steel spatula in ten sampling areas distributed throughout the whole lagoon and kept frozen. In the laboratory, 60 individuals were sorted by area for soft-tissue digestion. Each pool of 10 soft-tissue mussels (n = 6 by area) was wet-weighted and then placed in a 150-mL decontaminated glass beaker with 50 mL of 10% KOH. Samples were heated (40 °C) for 48 h, and digested samples were filtered in glass-fiber membranes. Microplastics were found in all samples of mussels (n = 60) from RFL; the particles were mostly lower than 100 µm with a mean concentration (±SD) of 35.96 ± 47.64 MPs g wet-weight-1. Microplastics were distinguished in seven shapes with different occurrences in samples (%): fiber (43.3%); fragment (34.3%); film (16.3%); sponge/foam (4.9%); pellet (0.57%), rope/filaments (0.17%); and undefined (0.4%). Thirteen colors of microplastics were found, but transparent (54.94%), black (10.77%), and white (9.36%) were the most common. Mytilopsis leucophaeata were useful to assess microplastic contamination in RFL and might be preferentially used in other invaded brackish systems instead of native and often threatened bivalves. Our results confirm the effective application of bivalves as an indicator of coastal microplastic pollution.

Microplastic accumulation in bivalves collected from different coastal areas of Vietnam and an assessment of potential risks

Microplastic (MP) pollution is an emerging problem in many areas around the world and in coastal areas of Vietnam, requiring more studies dedicated to the accumulation of this pollutant in the food chain as well as its potential risk to human health. This study investigated MP levels in tissues of five common bivalve species collected from aquaculture areas along the coast of Vietnam. MPs were found in all bivalve samples, with average values of 10.84 ± 2.61 items/individual or 2.40 ± 1.34 items/g wet weight. Impacts of feeding habits of bivalves showed influences on MP abundance in the samples. Fibers were the dominant shape of MPs recorded, most of which accumulated in the gills and digestive glands of all bivalve samples, with the majority falling within the size range of 300-2000 µm. MPs found in all studied species had relatively similar chemical compositions, mainly composed of polypropylene (PP) and polyethylene (PE). In this study, a diverse diet consisting of different bivalve species and detailed data on the consumption rate of these species were used to assess the human health risk of MPs dedicated to the coastal communities of Vietnam. The results suggested a significant part of MP uptake by human could be via bivalve consumption, in which removing viscera and proper depuration should be applied prior to eating, thereby reducing the risk.

Toxicity assessment of microplastics within the Loire River in the clam Corbicula fluminea exposed to environmentally relevant exposure conditions

The dispersed pollution caused by microplastics (MPs) represents a current and global concern. While the fragmentation of plastic debris into smaller particles occurs in rivers, little MP research is done on freshwater species and is published compared to the marine environment. The Loire River is the longest river in France and is subject to moderate to high anthropic pressure while it represents major societal and economic issues. However, there are not many studies that have been put forward with regards to the effect of environmental MPs (EMPs) on aquatic organisms and no policies have been enacted to monitor the plastic pollution. In this study, freshwater bivalves, Corbicula fluminea, were exposed for 21 days to environmentally relevant concentrations of a mixture of <200 µm MPs generated from plastic litter collected directly along the banks of the Loire River. This mixture was composed of 40% polyethylene (PE), 40% polypropylene (PP), 10% polyethylene terephthalate (PET) and 10% polyvinylchloride (PVC) (mass percentage). Ecotoxicological effects were assessed from the individual to the molecular levels on several endpoints: condition index, filtration efficiency, enzyme activities, lipid peroxidation, energy reserves and gene expression. The ingestion of EMPs caused damages at the biochemical level. Indeed, we reported an increase in catalase activity in gills and digestive mass, a decrease in TBARs in gills, a decrease in acetylcholinesterase activity in the digestive mass, a decrease of glycogen and lipid contents in the whole organisms and a significant induction of the expression of gst, cat, mp, acp genes. The current results suggest therefore that long-term exposure to realistic doses of EMPs causes toxicity towards freshwater benthic biota. The analysis of biomarker activities and the analysis of gene expression are complementary to prevent the effects of a plastic contamination at higher biological levels in aquatic organisms.

Recent Study of Separation and Identification of Micro- and Nanoplastics for Aquatic Products

Micro- and nanoplastics (MNPs) are polymeric compounds widely used in industry and daily life. Although contamination of aquatic products with MNPs exists, most current research on MNPs focuses on environmental, ecological, and toxicological studies, with less on food safety. Currently, the extent to which aquatic products are affected depends primarily on the physical and chemical properties of the consumed MNPs and the content of MNPs. This review presents new findings on the occurrence of MNPs in aquatic products in light of their properties, carrier effects, chemical effects, seasonality, spatiality, and differences in their location within organisms. The latest studies have been summarized for separation and identification of MNPs for aquatic products as well as their physical and chemical properties in aquatic products using fish, bivalves, and crustaceans as models from a food safety perspective. Also, the shortcomings of safety studies are reviewed, and guidance is provided for future research directions. Finally, gaps in current knowledge on MNPs are also emphasized.

The impact of microplastics on bivalve mollusks: A bibliometric and scientific review

Bivalves are important members of the ecosystem and their populations are declining globally, making them a concern for their role in ecosystem services and the fishing industry. Bivalves are excellent bioindicators of MPs pollution due to their widespread distribution, filtering capabilities, and close association with human health. Microplastics (MPs) have direct and indirect impacts on bivalves, affecting their physiology, habitat structure, food sources, and persistence of organic pollutants. This review provides an extensive overview of the impact of MPs on bivalves, covering various aspects such as their economic significance, ecological roles, and importance in biomonitoring environmental quality. The article presents the current state of knowledge on the sources and pathways of MPs in aquatic environments and their effects on bivalves. The mechanisms underlying the effects of MPs on bivalves, including ingestion, filtration activity, feeding inhibition, accumulation, bioaccumulation, and reproduction, are also discussed. Additionally, a bibliometric analysis of research on MPs in bivalves is presented, highlighting the number of papers, geographical distribution, and keyword clusters relating to MPs. Finally, the review emphasizes the importance of ongoing research and the development of mitigation strategies to reduce the negative effects of MPs pollution on bivalves and their habitats in oceans and coastal waters.

Effects of microplastics in aquatic environments on inflammatory bowel disease

The incidence of inflammatory bowel disease (IBD) has been increasing in recent years, particularly in newly industrialized nations. Environmental factors have been identified as playing a crucial role in IBD pathogenesis. Microplastics (MPs), a novel class of environmental pollutants, are a significant global pollution concern. MPs are found in almost all aquatic environments. MPs in the environment may pose health risks, specifically concerning the intestinal system, due to prolonged exposure through the consumption of aquatic foods and drinking water. In this review, we aimed to provide a comprehensive overview of the current knowledge on the impact of MPs in water resources on the occurrence and progression of IBD. Our systematic analysis of in vitro and in vivo studies found that MPs induce intestinal barrier dysfunction, imbalance in the intestinal microbiome, and metabolic abnormalities, ultimately leading to IBD. In addition, MP exposure causes greater harm to individuals with preexisting gastrointestinal disorders than those without them. Our analysis of this literature review highlights the need for further research to improve the understanding of the complex relationship between MP exposure and IBD.