Microplastics influence physiological processes, growth and reproduction in the Manila clam, Ruditapes philippinarum

Bioturbation effects and behavioral changes in buried bivalves after exposure to microplastics

Microplastic pollution has become an increasing concern. Vertical transport of microplastics is one of the major research questions concerning the distribution and fate of microplastics in the marine environment, and biologically mediated vertical transport is particularly significant. However, studies on the effects of different types of benthic organisms on the vertical distribution of microplastics in sediments are still scarce. The results of this study revealed that when exposed to environmentally relevant concentrations of fluorescent polystyrene microbeads (200 µm), Manila clams (Ruditapes philippinarum) exhibited prolonged acclimation period, yet subsequent burrowing behavior (burrowing rate and burrowing velocity) was unaffected. The condition index, clearance rate, and oxygen consumption rate of the clams similarly exhibited no stress response after 14 days of exposure. We determined that microplastics were rapidly transported to deeper layers (6-8 cm below the surface) in the sediment under bioturbation. This study elucidates the mechanisms of microplastic transport, showing that clam behaviors such as burrowing, movement, and ingestion contribute to this process. The results suggest that a biologically based management strategy may be a more environmentally friendly means of mitigating microplastic pollution in seawater.

A multi-levels analysis to evaluate the toxicity of microplastics on aquatic insects: A case study with damselfly larvae (Ischnura elegans)

Microplastic (MP) pollution prevalent in freshwater environments and jeopardizes the organisms living there. Dozens of studies have been conducted to investigate the harmful effects of microplastics on organisms. However, the most diverse and sensitive aquatic insects are often overlooked, also there is a lack of a comprehensive research exploring the toxicity of microplastics. Here, taking the damselfly larvae (Ischnura elegans) as the subject, we investigated the effects of different concentration levels of polystyrene microplastics (PS MPs) on their physiological characters, behavioristics, metabolomics and transcriptomics, as well as gut microbiome. The results showed that the PS MPs had no significant effects on the body weight and survival rate, but led to behavioral inhibition. Furthermore, expression levels of some metabolites altered, such as nicotinic acid, fumaric acid, and stearic acid. Meanwhile, the pathways related to oxidative phosphorylation and carbon metabolism were upregulated at the transcriptomic level. Moreover, there was a modification of the gut microbial community, with an increase in species richness but a shift towards potentially harmful bacteria. Our findings suggested that exposure to PS MPs affected the overall health of damselfly larvae. Therefore, effective management of MPs to minimize their environmental input is crucial in reducing health risks to aquatic organisms.

Omics insights in responses of bivalves exposed to plastic pollution

Plastic pollution, particularly microplastics and nanoplastics, poses a significant threat to marine ecosystems. Bivalves, vital filter feeders that accumulate plastic particles, underscore the necessity for advanced omics technologies to grasp their molecular reactions to plastic exposure. This review delves into the impact of microplastics and nanoplastics on bivalves utilizing advanced omics technologies. Through an examination of omics data, this review sheds light on how bivalves react to plastic pollution, informing strategies for conservation and food safety. Furthermore, theoretical pathways have been formulated to decipher how bivalves respond to environmental stressors from microplastics or nanoplastics through the integration of diverse biological fields. In this review, we report that microplastics and nanoplastics in marine ecosystems primarily stem from human activities on land and in marine domains. Bivalves are negatively influenced by plastic contamination, impacting their health and economic worth. Exposure to plastic particles disrupts bivalve behavior, metabolism, and reproduction, precipitating health concerns. Integration of omics data is instrumental in unraveling molecular interactions and devising biomarkers for monitoring purposes. Ingestion of plastics by bivalves poses risks to human health. Additionally, mitigation tactics involve bans, levies, and advocating for biodegradable alternatives to curtail plastic pollution. The amalgamation of omics findings aids in the comprehension of bivalve responses and effectively addressing plastic pollution. Moreover, addressing plastic pollution necessitates a multidisciplinary approach encompassing scientific inquiry, regulatory frameworks, and collaboration with stakeholders. These strategies are paramount in safeguarding bivalves, marine ecosystems, food safety, and human health.

Microplastics in commercial marine bivalves: Abundance, characterization and main effects of single and combined exposure

Microplastics (MPs) are persistent and ubiquitous pollutants in marine ecosystems, and they can be ingested and accumulated by marine organisms with economic value to humans, such as marine bivalves, which may pose a threat to the marine food chains and to human health. In this literature review, we summarized the recent findings on the abundance and main characteristics (shape, size, color, polymer) of MPs detected in valuable marine bivalve species. Furthermore, we surveyed the major impacts triggered by MP exposure, alone or in combination with other pollutants, in these organisms. Additionally, we discussed the methodologies, techniques and equipment commonly used by researchers for the determination of the abundance, characterization and effects of the MP particles in these organisms. We verified that MPs have been widely detected in multiple species of commercial marine bivalves, with a great variety of shapes, sizes, colors and polymer types. In general, the methodologies used by researchers to determine the MP abundance in marine bivalves need to be harmonized to facilitate the comparability between studies. So far, previous research showed that the main effects of MPs, either alone or combined with other pollutants, on commercial marine bivalves include the induction of immunological, physiological and behavioral responses, reproductive modifications, genotoxicity and neurotoxicity, which were surveyed by using a wide variety of techniques and analytical equipment. In the future, researchers should focus on less studied bivalve species and should use the most precise and innovative methodologies to assess the effects of MPs and other pollutants on marine bivalves.

Assessing the physiological effects of microplastics on cultured mussels in the Mediterranean Sea

Microplastics (MPs) pollution has gained attention due to its ecological threats and potential economic impacts. Yet significant knowledge gaps remain in understanding MPs effects on marine organisms' physiology. This study quantifies the physiological impacts of MPs on farmed mussels (Mytilus galloprovincialis) across various locations in the Mediterranean Sea by combining a laboratory experiment with a Dynamic Energy Budget (DEB) model. Mussels' clearance rates (CR) were measured under different conditions of microplastics and suspended sediment. The DEB model, driven by satellite data and an MPs distribution model, was validated with literature growth and CR data, supporting further the data extracted from the conducted experiment. Results indicate that while the physiological impacts are minimal in most areas, important reductions in CR (8-25%) were estimated in regions like the Gulf of Napoli, leading to reduced growth (6-16%) and reduced reproductive output (7-19%). In addition to microplastic concentrations, seasonal and spatial variations of food availability and suspended inorganic matter importantly control the impacts, with mussels in oligotrophic environments (such as the Gulf of Napoli) showing higher vulnerability to MPs compared to those in more eutrophic locations. This study underscores the utility of bioenergetics models, such as DEB, in evaluating the ecological risks of microplastics and suggests their broader application in MPs research.

Comprehensive assessment of multiple biomarker mechanisms in the brackish water clam Corbicula japonica exposed to polystyrene microplastics using structural equation modeling

Using structural equation modeling (SEM), we investigated multiple biomarker mechanisms in terms of biochemical and individual marker responses in the brackish water clam Corbicula japonica following acute exposure to polystyrene microplastic (PS-MP). This study is the first to comprehensively explore multiple biomarker responses in bivalves using SEM. The model revealed that PS-MP accumulation was an independent biomarker, exhibiting significant direct effects on superoxide dismutase (SOD) and catalase (CAT) among the biochemical markers. Although CAT generally interacts closely with SOD, no significant relationship was identified between them, indicating that CAT may have independently responded to PS-MP stress. Among individual markers, significant indirect effects were observed on clearance rate (CR), reflecting feeding activity and valve open rate, indicating excretion activity via SOD and CAT. Finally, the carbon-based scope for growth was significantly influenced by CR. SEM is efficient and useful for identifying significant direct and indirect pathway relationships and for uncovering uncommon relationships in unified multiple biomarker mechanisms in aquatic studies.

Bio-based microplastic polylactic acid exerts the similar toxic effects to traditional petroleum-based microplastic polystyrene in mussels

Microplastics (MPs) have accumulated in the oceans, causing adverse effects on marine organisms and the environment. Biodegradable polylactic acid (PLA) is considered as an excellent substitute for traditional petroleum-based plastics, but it is difficult to degrade completely and easily become MPs in the marine environment. To test the ecological risk of bio-based PLA, we exposed thick-shelled mussels (Mytilus coruscus) to bio-based PLA and petroleum-based polystyrene (PS) (at 102, 104, and 106 particles/L) for 14 days. The significant increase in enzyme activities related to oxidative stress and immune response showed that mussels were under physiological stress after MP ingestion. While enzyme activities of nerve conduction and energy metabolism were significantly disturbed after exposure. Meanwhile, normal physiological activities in respiration, ingestion and assimilation were also suppressed in association with enzyme changes. The negative effects of PS and PLA in mussels were not differentiated, and further integration analysis of integrated biomarker response (IBR) and principal component analysis (PCA) also showed that PLA would induce adverse effects in mussels and ecological risks as PS, especially at environmental concentrations. Therefore, it is necessary to pay more attention to the environmental and ecological risk of bio-based MP PLA accumulating in the marine environment.

Microplastic pollution in the surface waters of the zuari river, goa, india

Limited research has been conducted on microplastic (MP) contamination in the rivers of Goa. To address this gap, this study examines the levels of MP contamination in the surface water of the Zuari River, Goa. We investigate the abundance, characteristics (size, shape, colour, and polymer composition), and risk assessment of MPs. MPs were detected at all sampling stations in the Zuari River, with concentrations varying from 0.01 particles/L (S3) to 1.38 particles/L (S13). The average abundance of MPs in the water samples was 0.28 ± 0.35 particles/L. MPs were more common in the 0.3-1 mm size range (51.70%) than in the 1-5 mm range (48.30%). The most common MP shapes observed were fibers (37.88%) and fragments (29.66%). FTIR analysis confirmed the presence of polyethylene terephthalate, high-density polyethylene, polypropylene, and polyacrylamide carboxyl-modified MPs. The Pollution Load Index (PLI) showed an average value of 3.8, indicating significant contamination (PLI > 1). Scanning electron microscopy (SEM) revealed various degradation features such as pits, scratches, grooves, and cracks on the MPs surfaces, while energy dispersive X-ray spectroscopy (EDS) detected metals on the MP's surfaces. This study provides key insights into MP pollution in the Zuari River's surface water and lays the groundwork for future research and management strategies in the region.

Microplastics and arsenic speciation in edible bivalves from the coast of China: Distribution, bioavailability, and human health risk

Bivalves, such as oysters and mussels, are exposed to environmental pollutants, like microplastics (MPs) and arsenic (As). This study investigated co-existence and interaction of MPs and As (total As and As species) in two bivalve species from the Chinese coastline. Smaller MPs (20-100 μm) averaged 30.98 items/g, while larger MPs (100-500 μm) averaged 2.98 items/g. Oysters contained more MPs (57.97 items/g) in comparison to mussels (11.10 items/g). In Contrast, mussels had a higher As concentrations (8.36-23.65 mg/kg) than oysters (4.97-11.02 mg/kg). The size and composition of MPs influenced As uptake and speciation in bivalves, with inorganic arsenic (iAs) and methylated arsenic (MMA and DMA) correlating with larger-sized MPs. Polyethylene (PE) may interact with the formation of arsenobetaine (AsB) in oyster. This study provides valuable insights into the interaction of MPs and As in marine ecosystems and highlights their implications for food safety.

Exploring the co-exposure effects of environmentally relevant microplastics and an estrogenic mixture on the metabolome of the Sydney rock oyster

In aquatic environments the concurrent exposure of molluscs to microplastics (MPs) and estrogens is common, as these pollutants are frequently released by wastewater treatment plants into estuaries. Therefore, this study aimed to evaluate the independent and co-exposure impacts of polyethylene microplastics (PE-MPs) and estrogenic endocrine-disrupting chemicals (EEDCs) at environmentally relevant concentrations on polar metabolites and morphological parameters of the Sydney rock oyster. A seven-day acute exposure revealed no discernible differences in morphology; however, significant variations in polar metabolites were observed across oyster tissues. The altered metabolites were mostly amino acids, carbohydrates and intermediates of the Kreb's cycle. The perturbation of metabolites were tissue and sex-specific. All treatments generally showed an increase of metabolites relative to controls - a possible stimulatory and/or a potential hormetic response. The presence of MPs impeded the exposure of adsorbed and free EEDCs potentially due to the selective feeding behaviour of oysters to microplastics, favouring algae over similar-sized PE-MPs, and the formation of an eco/bio-corona involving faeces, pseudo-faeces, natural organic matter, and algae.

Mangrove plants are promising bioindicator of coastal atmospheric microplastics pollution

Plastics are commonly used by society and their break down into millimeter-sized bits known as microplastics (MPs). Due to the possibility of exposure, reports of them in atmospheric deposition, indoor, and outdoor air have sparked worry for public health. In tropical and subtropical regions all throughout the world, mangroves constitute a distinctive and significant type of coastal wetlands. Mangrove plants are considered to have the effect of accumulating sediment MPs, but the sedimentation of atmospheric MPs has not been reported. In this study, we illustrated the characteristics, abundance and spatial distribution of MPs in different species of mangrove leaves along the Seagull Island in Guangzhou. MPs samples from leaves in five species showed various shapes, colors, compositions, sizes and abundance. Acanthus ilicifolius had an average fallout rate of 1223 items/m2/day which has the highest abundance of MPs in all samples. Four shapes of MPs were found in all leaves surfaces including fiber, fragment, pellet, and film, with fiber is the most. The dominant types of MPs in all leaves were cellulose and rayon. Most of the total MPs size were smaller than 2 mm. Clearly, the microstructures of each species leaf surfaces had an impact on its ability to retain MPs. The plants rough blade surfaces and big folds or gullies caused more particles to accumulate and had a higher MPs retention capacity. Overall, our study contributes to a better knowledge of the condition of MPs pollution in atmosphere and the connection between leaves structure and the retention of MPs, which indicates that mangrove plants are promising bioindicator of coastal atmospheric MPs pollution.

Bioconcentration, biotransformation, and transcriptomic impact of the UV-filter 4-MBC in the manila clam Ruditapes philippinarum

Ultraviolet filters (UV-filters) are compounds extensively used in personal care products. These compounds are produced at increasing rates and discharged into marine ecosystems in unknown quantities and with no regulation, making them emerging contaminants. Among those, the UV-filter 4-Methylbenzylidene camphor (4-MBC) is used in a variety of personal care products such as sunscreens, soaps, or lipsticks. This high consumption has resulted in its presence in various environmental matrices at in concentrations ranging from ng to μg L-1. Very little is known, however, about the possible adverse effects in exposed non-target organisms. Our study presents novel data on the bioconcentration, toxicokinetics, and molecular effects of 4-MBC in a marine bivalve species of commercial interest, Ruditapes philippinarum (Manila clam). Organisms were exposed at two different concentrations (1.34 and 10.79 μg L-1) of 4-MBC for 7 days, followed by a 3-day depuration period (clean sea waters). Bioconcentration factors (BCF) were 3562 and 2229 L kg-1 for the low and high exposure concentrations, respectively, making this pollutant bioaccumulative according to REACH criteria. Up to six 4-MBC biotransformation products (BTPs)were identified, 2 of them for the first time. Transcriptomic analysis revealed between 658 and 1310 differently expressed genes (DEGs) after 4-MBC exposure. Functional and enrichment analysis of the DEGs showed the activation of the detoxification pathway to metabolize and excrete the bioconcentrated 4-MBC, which also involved energy depletion and caused an impact on the metabolism of carbohydrates and lipids and in the oxidative phosphorylation pathways. Oxidative stress and immune response were also evidenced through the activation of cathepsins and the complement system. Such elucidation of the mode of action of a ubiquitous pollutant such as 4-MBC at the molecular level is valuable both from an environmental point of view and for the sustainable production of Manila clam, one of the most cultivated mollusk species worldwide.

Microplastic pollution and risk assessment in surface water and sediments of the Zandvlei Catchment and estuary, Cape Town, South Africa

Microplastic (MP) (plastic <5 mm) pollution in South Africa is widespread but few studies have been done in catchments and estuaries of the country. The aim of this study was to investigate the abundance, characteristics and risks posed by microplastics in the Zandvlei Catchment and Estuary in Cape Town, South Africa. Water and sediment were sampled between 2019 and 2021, during wet and dry seasons, MPs extracted and identified using microscopy and fourier-transformed infrared spectrophotometry (FTIR) analyses. MP abundances were 70.23 ± 7.36 (standard error) MPs/Kg dw in sediment and 2.62 ± 0.41 MP/L in water samples for the study period. Lower reaches of the catchment and upper reaches of the estuary can be considered sinks for MP contamination as these sites recorded higher MP abundances. MPs were mainly transparent fibres smaller than 0.5 mm. Polyethylene (46%) followed by polypropylene (16%) fibres were the most common polymers recorded. Pollution load indices in MPs were categorised as dangerous in both water and sediment. MP polymer risk indices ranged from moderate in catchment sediment to very high in catchment water. Pollution risk indices were categories as dangerous in water (catchment and sediment) and sediment estuary but low in catchment sediment. Ecological risk assessments hence indicated that polymers in water and sediment were mostly dangerous and poses a threat to the ecological health of both the catchment and estuary studied.

Microplastics aggravate the bioaccumulation and corresponding food safety risk of antibiotics in edible bivalves by constraining detoxification-related processes

Characterized by a sessile filter-feeding lifestyle, commercial marine bivalves inhabiting pollution-prone coastal areas may accumulate significant amounts of pollutants, such as antibiotic residues, in their soft tissues and thus pose a potential threat to the health of seafood consumers. Microplastics are another type of emerging pollutant that are prevalent in coastal areas and have been reported to interact with common antibiotics such as enrofloxacin (ENR) and trimethoprim (TMP). Nevertheless, little is known about the impacts of MPs on the accumulation and corresponding food safety risk of antibiotics in edible bivalve species. Taking the frequently detected ENR, TMP, and polystyrene (PS)-MPs as representatives, the accumulation of above-mentioned antibiotics in three commercial bivalves with or without the copresence of MPs was assessed. In addition, the corresponding food safety risks of consuming antibiotic-contaminated bivalves were evaluated. Moreover, the impacts of these pollutants on detoxification-related processes were analyzed using the thick-shell mussel as a representative. Our results demonstrated that blood clams (Tegillarca granosa), thick-shell mussels (Mytilus coruscus), and Asiatic hard clams (Meretrix meretrix) accumulated significantly higher amounts of antibiotics in their bodies under antibiotic-MP coexposure scenarios. Although based on the target hazard quotients (THQs) and the margins of exposure (MoEs) obtained, the direct toxic risks of consuming ENR- or TMP-contaminated bivalves were negligible, the TMP residue accumulated in TMP-MP-coexposed mussels did surpass the maximum residue limits (MRLs) of the corresponding National Food Safety Standard of China, suggesting that other forms of potential risks should not be ignored. In addition, it was shown that the detoxification, energy provision, and antioxidant capacities of the thick-shell mussels were significantly hampered by exposure to the pollutants. In general, our data indicate that MPs may aggravate the accumulation and corresponding food safety risk of antibiotics in edible bivalves by disrupting detoxification-related processes, which deserves closer attention.

Triclosan exposure induces immunotoxic impacts by disrupting the immunometabolism, detoxification, and cellular homeostasis in blood clam (Tegillarca granosa)

Omnipresent presence of triclosan (TCS) in aqueous environment puts a potential threat to organisms. However, it's poorly understood about its immunometabolic impacts of marine invertebrates. In present study, we use a representative bivalve blood clam (Tegillarca granosa) as a model, investigating the effects of TCS exposure at 20 and 200 μg/L for 28 days on immunometabolism, detoxification, and cellular homeostasis to explore feasible toxicity mechanisms. Results demonstrated that the clams exposed to TCS resulting in evident immunotoxic impacts on both cellular and humoral immune responses, through shifting metabolic pathways and substances, as well as suppressing the expressions of genes from the immune- and metabolism-related pathways. In addition, significant alterations in contents (or activity) of detoxification enzymes and the expression of key detoxification genes were detected in TCS-exposed clams. Moreover, exposure to TCS also disrupted cellular homeostasis of clams through increasing MDA contents and caspase activities, and promoting activation of the apoptosis-related genes. These findings suggested that TCS might induce immunotoxic impacts by disrupting the immunometabolism, detoxification, and cellular homeostasis.

Occurrence and sources of microplastics on Arctic beaches: Svalbard

Plastic pollution is recognised as a major global environmental concern, especially within marine environments. The small size of microplastics (< 5 mm) make them readily available for ingestion by organisms in all trophic levels. Here, four beach sites in Adventfjorden on the west coast of Svalbard, were sampled with the aim of investigating the occurrence and abundance of microplastics on beaches to assess potential sources of microplastic pollution. High variability in microplastic amount, type and polymers were found at all sites ranging from means of 0.7 n/g (number) at the remotest site and 2.2 n/g (number) at the site closest to Longyearbyen. Statistical analyses suggested that patterns observed were linked to direct proximity to human activities through land uses and effluent discharge. These findings point to an increased importance of localised factors on driving elevated microplastic pollution in beach sediments over oceanic controls in remote but inhabited Arctic locations and have important implications for our understanding and future assessments of microplastic pollution in such settings.

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.

The role of microbe-microplastic associations in marine Nematode feeding behaviors

Fauna across many taxa and trophic levels have been shown to consume microplastics (MPs) in experiments, providing evidence that supports field-based gut content assessments. Multiple explanations exist regarding why fauna consume MPs, one of which posits that microbial growth on MPs may facilitate faunal ingestion. However, laboratory assessments on the reasons why MPs are consumed remain limited. Here, we assessed if the presence of microbes on MPs altered marine nematode feeding behaviors across current and potential future concentrations of MPs in a local system. We used a microcosm experiment in which field-collected sediment was spiked with bacterially treated or untreated fluorescent plastic microbeads (1.0-5.0 μm) in concentrations of 102, 104, and 106 per microcosm, representing local and potential future concentrations of MPs. Ingestion by the dominant interstitial fauna was investigated after 0, 3, and 7 days using bright field microscopy. Nematodes were the only fauna across microcosms that consumed MPs, but this consumption was variable and there were no apparent trends across exposure time, bacterial treatment, or MP concentration. There were also no genera- or feeding-type-specific trends in the number of MPs consumed, though four of the top five nematode genera that consumed MPs were pollution-tolerant genera. Our study demonstrates that microbe-MP associations do not drive marine nematodes to eat MPs, especially at local field concentrations. While there were no trends across any of the nematode genera in our study, we recognize that unrealistic MP concentrations in other studies may provide alternative explanations for nematode consumption of MPs.

The crosstalk between M1 macrophage polarization and energy metabolism disorder contributes to polystyrene nanoplastics-triggered testicular inflammation

Ubiquitous microplastics have become a threat to animal and human health, due to their potential toxicity, persistent nature and consequent bioaccumulation. Supporting evidence elucidates that polystyrene nanoplastics (PS-NPs) can destroy blood-testis barrier integrity, thus causing testicular hypoplasia and impairment of spermatogenesis. Nevertheless, how PS-NPs modulate macrophage polarization-energy metabolism crosstalk has not been fully investigated in testicular tissue. Here, we observed that polystyrene PS-NPs exposure contributes to severe vacuolization in the seminiferous tubules, accompanied by apoptosis of testicular tissue and infiltration of M1 macrophages. Meanwhile, we found that PS-NPs could trigger the M1 polarization phenotype, which activated ROS-macrophage migration inhibitory factor (MIF)/NF-κB signaling that in turn induced apoptosis of GC2 cells in the GC2-macrophage cell coculture model. Simultaneously, we confirmed that PS-NPs exposure increased 3-phospho-D-glycerate, phosphoenolpyruvate and lactate concentrations, accompanied by decreased pyruvate and adenosine triphosphate (ATP) production, likely due to downregulated pyruvate kinase M2 (PKM2) dimer expression. In conclusion, the mechanism of PS-NPs-induced testicular inflammation can be mediated by promoting the infiltration of M1 macrophages, thereby resulting in an ROS burst and subsequent induction of energy metabolism disorders. The current study will provide new insights into PS-NPs-induced male reproductive toxicity and highlight the context-specific roles of testicular macrophages.

Impact of polyethylene microplastics on the clam Ruditapes decussatus (Mollusca: Bivalvia): examination of filtration rate, growth, and immunomodulation

The present study was conducted to assess, for the first time, the effects of a 14 days experimental exposure to polyethylene (PE) based MPs (40-48 µm) on the clam Ruditapes decussatus. Clams were exposed to three different concentrations of MPs in controlled laboratory conditions: 10 µg/L (low), 100 µg/L (medium), and 1000 µg/L (high). The effects of MPs were assessed using a multi-marker approach, including the filtration rate, growth, and the integrity of immune cells (such as haemocyte numbers, viability, and lysosomal membrane destabilization). The results revealed that as the concentration of PE-MPs increased, the filtration rate decreased, indicating that PE-MPs hindered the clams' ability to filter water. Furthermore, there was a noticeable decrease in the overall weight of the clams, particularly in the group exposed to 1000 µg/L. This decrease could be attributed to the impairment of their nutrient filtration function. In terms of immune system biomarkers, exposure to PE-MPs led to immune system disruption, characterized by a significant increase in the number of haemocytic cells, especially in the group exposed to the high concentration. Additionally, there was a notable reduction in the viability of haemocytes, resulting in the destabilization of their lysosomal membranes, particularly in the groups exposed to medium and high PE-MPs concentrations. The findings of this study indicate that the sensitivity of hemolymph parameter changes and filtration rate in R. decussatus exposed to PE-MPs (100 and 1000 µg/L), surpasses that of growth performance and can serve as reliable indicators to assess habitat conditions and contaminant levels.

A review of microplastic pollution in aquaculture: Sources, effects, removal strategies and prospects

As microplastic pollution has become an emerging environmental issue of global concern, microplastics in aquaculture have become a research hotspot. For environmental safety, economic efficiency and food safety considerations, a comprehensive understanding of microplastic pollution in aquaculture is necessary. This review outlines an overview of sources and effects of microplastics in aquaculture. External environmental inputs and aquaculture processes are sources of microplastics in aquaculture. Microplastics may release harmful additives and adsorb pollutants in aquaculture environment, cause deterioration of aquaculture environment, as well as cause toxicological effects, affect the behavior, growth and reproduction of aquaculture products, ultimately reducing the economic benefits of aquaculture. Microplastics entering the human body through aquaculture products also pose potential health risks at multiple levels. Microplastic pollution removal strategies used in aquaculture in various countries are also reviewed. Ecological interception and purification are considered to be effective methods. In addition, strengthening aquaculture management and improving fishing gear and packaging are also currently feasible solutions. As proactive measures, new portable microplastic monitoring system and remote sensing technology are considered to have broad application prospects. And it was encouraged to comprehensively strengthen the supervision of microplastic pollution in aquaculture through talent exchange and strengthening the construction of laws and regulations.

Adverse impacts of high-density microplastics on juvenile growth and behaviour of the endangered tri-spine horseshoe crab Tachypleus tridentatus

The impacts of high-density microplastics, namely polyamine 6,6 (nylon), polymethyl methacrylate (PMMA) and polyethylene terephthalate (PET), on growth and behaviour of the endangered tri-spine horseshoe crab Tachypleus tridentatus were investigated for 100 days. Negative changes in wet weight and prosomal width of the juveniles were observed in all treatments of microplastics, but significant difference was only detected in prosomal width between control and PMMA. T. tridentatus became significantly less active upon exposure to nylon and PET. The extent of burrowing by T. tridentatus did not significantly differ among the treatments but was overall significantly reduced towards day 100. T. tridentatus exposed to PET significantly showed the lowest survival probability (30 %), compared to the other treatments (70-90 %). In conclusion, high-density microplastics compromised growth and behaviour of juvenile horseshoe crabs. Among the polymers that were tested, PET was considered more harmful and associated with higher mortality.

Effect of size continuum from nanoplastics to microplastics on marine mussel Mytilus edulis: Comparison in vitro/in vivo exposure scenarios

For several decades, plastic has been a global threat in terms of pollution. Plastic polymers, when introduce in the aquatic environment, are exposed to fragmentation processes into microplastics (MPs) and nanoplastics (NPs) which could potentially interact with living organisms. The objective of this work was to study the effects of plastic particles representative of those found in the environment, on the marine mussels Mytilus edulis, under two exposure scenarios: in vivo and in vitro. Whole mussels or cultured hemocytes were exposed for 24 h to NPs and MPs generated from macro-sized plastics collected in the field, but also to reference NPs, at concentrations found in the environment: 0.08, 10 μg and 100 μg·L^-1. Results showed that immune response was only activated when mussels were exposed in vivo. However, cytotoxicity (hemocyte mortality) and genotoxicity (DNA damage) parameters were induced after both types of exposure, but in a dose-dependent manner after in vitro hemocyte exposure to all tested plastic conditions. These results indicate that in vitro approaches could be considered as potential predictors of in vivo exposures.

Influence of ultraviolet-aging and adsorbed pollutants on toxicological effects of polyvinyl chloride microplastics to zebrafish

Microplastics (MPs) undergo various aging processes and interact with diverse pollutants in the environment. In the present study, we investigated the influence of ultraviolet (UV) aging on the adsorption of organic pollutants by polyvinyl chloride microplastics (mPVC) and explored toxicity variations among pristine, aged, and pollutant-loaded mPVCs to zebrafish. Irradiation of UV for 30 d significantly changed the physiochemical properties of mPVC, leading to more oxygen-containing groups and free radicals (¹O₂, ·O₂^-, and ·OH) on mPVC surfaces. The aging process reduced the adsorption of mPVC against a hydrophobic compound chlorpyrifos (CPF) but enhanced the adsorption against a moderately hydrophilic compound erythromycin (ERY). Ingestion of CPF- and ERY-loaded mPVCs resulted in bioaccumulation of the two compounds in zebrafish, suggesting a carrier effect of mPVCs. In toxicity tests, the aged mPVC caused severer gut damages, stronger oxidative stresses, and greater interference with the gut microbiota in zebrafish than the pristine mPVC. The CPF and ERY-loaded mPVCs produced lower oxidative stresses in zebrafish than mPVCs alone, due to fewer radicals on mPVC surfaces after the adsorption of organic contaminants. Notably, the CPF and ERY-loaded mPVCs presented greater effects on fish swimming behaviors and gut microbial compositions, which was associated with the released CPF and ERY from mPVCs within the zebrafish. Overall, the present study demonstrated significant influences of UV-aging and the adsorbed pollutants on the toxicological effects of MPs and highlighted the necessity to perform toxicity studies of MPs using more environmentally relevant MPs.

Short-Term Exposure to MPs and DEHP Disrupted Gill Functions in Marine Bivalves

The synergistic impact of microplastics (MPs) and organic pollutants remains poorly understood in the marine environment. This study aimed to assess the toxicity of polypropylene microplastics (PS) and/or di-(2-ethylhexyl) phthalate (DEHP) on marine clams. Both Ruditapes philippinarum and Tegillarca granosa were exposed to PS and DEHP individually and combined at environmentally relevant concentrations for 48 h. The filtration rate, antioxidant enzymes activity, lipid peroxidation, reactive oxygen species accumulation, and histological alterations were evaluated. Our results show that single or co-exposure to MPs and DEHP significantly decreases the filtration rate in both type of clams, but the latter exhibited stronger inhibition effect. Close examination of accumulation of reactive oxygen species and related biomarkers revealed that combined exposure exerts greater oxidative stress in the cells, which causes more serious histopathological damage in the gills of the bivalves. Our study implies that MPs, in synergy with organic pollutants, can be more harmful for marine organisms.

Immunotoxicity of pentachlorophenol to a marine bivalve species and potential toxification mechanisms underpinning

The ubiquitous presence of pentachlorophenol (PCP) in ocean environments threatens marine organisms. However, its effects on immunity of marine invertebrates at environmentally realistic levels are still largely unknown. In this study, the immunotoxicity of PCP to a representative bivalve species was evaluated. In addition, its impacts on metabolism, energy supply, detoxification, and oxidative stress status were also analysed by physiological examination as well as comparative transcriptomic and metabolomic analyses to reveal potential mechanisms underpinning. Results illustrated that the immunity of blood clams was evidently hampered upon PCP exposure. Additionally, significant alterations in energy metabolism were detected in PCP-exposed clams. Meanwhile, the expressions of key detoxification genes and the in vivo contents (or activity) of key detoxification enzymes were markedly altered. Exposure to PCP also triggered significant elevations in intracellular ROS and MDA whereas evident suppression of haemocyte viability. The abovementioned findings were further supported by transcriptomic and metabolomic analyses. Our results suggest that PCP may hamper the immunity of the blood clam by (i) constraining the cellular energy supply through disrupting metabolism; and (ii) damaging haemocytes through inducing oxidative stress. Considering the high similarity of immunity among species, many marine invertebrates may be threatened by PCP, which deserves more attention.

Effects of microplastics on physiological performance of marine bivalves, potential impacts, and enlightening the future based on a comparative study

This review aims to explore the effects of microplastics and their corresponding additives on the physiological performances of marine bivalves together with their related genes. We identified gaps based on studies that were conducted on other organisms, and we conducted a comparative study on similar and relevant aspects for exploring future potential areas of study and interest. Microplastics are widely dispersed in all forms of media (solid, liquid, and gas). Exposure to an organism (including humans) is inevitable. However, impacts depend on the concentration of exposure, location of a biomarker being observed, and treatment involved. Different shapes, colors, and polymer types are reported and the transfer of microplastics along the food chain are recorded. The impacts of microplastics intensify when coupled with other chemicals or additives (referred to as xenobiotics) in a treated group. Thus, the degree of inhibition or enhancement of a physiological response magnifies when a coexposure of microplastic and a xenobiotic occurs. Microplastics have been observed to reduce immune system functionality by reducing hemocytes count, distorting oxidative system, respiration, and increasing energy consumption in bivalves due to physiological modulations that result from ingestion of microplastics or their additives. We found knowledge gaps and suggested future research directions to fully understand the impact of microplastics and their additives on marine bivalves.

Transcriptomic and metabolic responses of earthworms to contaminated soil with polypropylene and polyethylene microplastics at environmentally relevant concentrations

Examining transcriptomic and metabolic responses of earthworms to microplastic-contaminated soil is critical for understanding molecular-level toxicity of microplastics; yet very little research on this topic exists. We investigated influences of environmentally relevant concentrations (ERC) of polypropylene (PP) and polyethylene (PE) microplastic-contaminated soil on earthworms at the transcriptomic, metabolic, tissue and whole-body levels to study their molecular toxicity. The addition of PP and PE at ERC induced oxidative stress on earthworms, as indicated by the high enrichment of glutathione metabolism and increased glutamine at the transcriptomic and metabolic levels. Digestive and immune systems of earthworms were damaged according to the injuries of the intestinal epithelium, partial shedding of chloragogenous tissues and unclear structure of coelom tissues, which were confirmed by pathway analysis at the transcriptomic level. Significant enrichment of arachidonic acid and glycerolipid metabolisms indicated that PP and PE disturbed the lipid metabolism in earthworms. Significantly increased betaine and myo-inositol, and decreased 2-hexyl-5-ethyl-3-furansulfonate suggested that PP and PE caused differences in osmoregulation extent. In conclusion, most similar responses of earthworm might result from special size rather than type effects of PP and PE microplastics. Contamination of soils with microplastics even at ERC has health risks to earthworms; therefore, proper management of microplastics to reduce their input to the environment is key to reducing the health risks to soil fauna.