Evaluation of antioxidant capacity and digestive enzyme activities in Mytilus galloprovincialis exposed to nanoplastics under different patterns of hypoxia

The effects of expanded polystyrene particle on energy metabolism of the sea slater (Ligia cinerascens) originating from a highly EPS-polluted area

Due to its high concentration and persistence, microplastic (MP) pollution is a major threat to marine environments. Expanded polystyrene (EPS) particles are the most abundant MP type in Asian regions, including the Korean coastal region. Although many previous studies have reported the toxicity of MPs to marine biota, the toxicity of environmentally relevant MPs to coastal organisms is not well understood. Thus, we investigated the toxicity of EPS on the growth and energy metabolism of the juvenile marine isopods, Ligia cinerascens, obtained from a population that has been exposed to EPS through multiple generations. After 14 and 21 days of dietary EPS exposure, body weight and molting of L. cinerascens were unaffected. However, the energy reserves (carbohydrates, proteins, and lipids) were significantly reduced, resulting in a decrease in the total energy budget (Ea) by dietary EPS exposure. The transcriptional modulation patterns of genes related to energy metabolism suggested that dietary EPS exposure may increase the digestion of non-carbohydrate sources, such as proteins and lipids, to compensate for increased energy expenditure. Our findings suggest that dietary EPS exposure, although no toxic at the individual level, can reduce the energy status of juvenile marine isopods, which provides useful information on the toxic effects of environmentally relevant MPs to coastal ecosystem.

Sex-specific reproductive impairment in Pacific oysters (Magallana gigas) exposed to TiO2 NPs: A focus on gonadal status

Environmentally realistic concentrations of titanium dioxide nanoparticles (TiO2 NPs) are considered reprotoxic for marine bivalves. However, further investigation is needed to understand their impact on gonadal health, particularly concerning sex-specific responses. Thus, this study aimed to understand sex-based effects of TiO2 NPs environmentally realistic concentrations in the gonad of Pacific oysters (Magallana gigas). Oysters were exposed to 10 and 100 μg·L-1 of TiO2 NPs for 3 and 7 days. Morphological parameters (condition index, sex and gametogenic stage), energy-related responses (carbohydrates, lipids, proteins, and electron transport system (ETS) activity), digestive function (alpha-amylase activity), and oxidative stress profile (antioxidants and damage) were assessed to address gonadal status. The results revealed sex-specific responses based on duration and concentration. Females reflected a drop in carbohydrate levels after 3 days at 100 μg·L-1, suggesting mobilization of this energy reserve to counteract TiO2 NP effects, followed by recovery after 7 days. Males showed reduced metabolic activity after 3 days at 10 μg·L-1, marked by ETS depletion, independently of oxidative stress demonstrating a compensatory response to TiO2 NP exposure. After 7 days, both concentrations triggered male lipid peroxidation despite carbohydrate mobilization at 10 μg·L-1, indicating oxidative damage in testes. These findings revealed that TiO2 NPs are reprotoxic for male oysters at 10 μg·L-1, through oxidative stress pathways, while females reflected vulnerability to 100 μg·L-1. This study provides valuable insights into understanding TiO2 NP's reprotoxicity at environmental concentrations, highlighting gonads as a target for these NPs, and their potential risks to marine bivalves.

UV-Aged Nanoplastics Increase Mercury Toxicity in a Marine Copepod under Multigenerational Exposure: A Carrier Role

Aged plastics possess diverse interactive properties with metals compared to pristine ones. However, the role of aging for nanoplastics (NPs) in being a carrier of mercury (Hg), a common marine environmental pollutant, and their combined effects remain unclear. This study investigated the carrier effect of ultraviolet-aged NPs on Hg and the ensuing toxicity in a marine copepod Tigriopus japonicus under a multigenerational scenario. Aged NPs revealed a better carrier role in Hg bioaccumulation than pristine ones, which was increased by 1.61, 1.52, and 1.54 times in F0, F1, and F2, respectively, probably attributed to increased levels of O-containing functional groups and better adsorption for Hg. Consequently, relative to Hg alone, Hg combined with aged NPs (rather than pristine ones) significantly compromised the copepod's fitness, e.g., the survival rate decreasing by 74.2 and 62.1% in F1 and F2, respectively. This is possibly linked to the most pronounced transcriptomic response under Hg combined with aged NPs, including disturbed cuticle formation, activated antioxidants, and down-regulation of reproductive genes. Overall, our findings emphasize the non-negligible risk of aged NPs as carriers of toxic metals and provide a better understanding about the long-term effects of coexisting NPs and metal pollution on organisms in real marine environments.

Plastic pollution and marine mussels: Unravelling disparities in research efforts, biological effects and influences of global warming

The ever-growing contamination of the environment by plastics is a major scientific and societal concern. Specifically, the study of microplastics (1 μm to 5 mm), nanoplastics (< 1 μm), and their leachates is a critical research area as they have the potential to cause detrimental effects, especially when they impact key ecological species. Marine mussels, as ecosystem engineers and filter feeders, are particularly vulnerable to this type of pollution. In this study, we reviewed the 106 articles that focus on the impacts of plastic pollution on marine mussels. First, we examined the research efforts in terms of plastic characteristics (size, polymer, shape, and leachates) and exposure conditions (concentration, duration, species, life stages, and internal factors), their disparities, and their environmental relevance. Then, we provided an overview of the effects of plastics on mussels at each organisational levels, from the smaller scales (molecular, cellular, tissue and organ impacts) to the organism level (functional, physiological, and behavioural impacts) as well as larger-scale implications (associated community impacts). We finally discussed the limited research available on multi-stressor studies involving plastics, particularly in relation to temperature stress. We identified temperature as an underestimated factor that could shape the impacts of plastics, and proposed a roadmap for future research to address their combined effects. This review also highlights the impact of plastic pollution on mussels at multiple levels and emphasises the strong disparities in research effort and the need for more holistic research, notably through the consideration of multiple stressors, with a specific focus on temperature which is likely to become an increasingly relevant forcing factor in an era of global warming. By identifying critical gaps in current knowledge, we advocate for more coordinated interdisciplinary and international collaborations and raise awareness of the need for environmental coherence in the choice and implementation of experimental protocols.

Simultaneous exposure to microplastics and heavy metal lead induces oxidative stress, histopathological damage, and immune dysfunction in marine mussel Mytilus coruscus

The increasing deposition of microplastics (MPs) in aquatic ecosystems is a worldwide concern. MPs can interact with other environmental pollutants, such as heavy metals, and change their toxicity. In this study, we focused on the effects of MPs and lead (Pb), as a toxic heavy metal, on marine mussel Mytilus coruscus under separate and co-exposure situations at environmentally relevant concentrations: MPs (1 mg/L) and Pb (50 μg/L). We found that MPs alone or in combination with Pb significantly decreased the respiration and filtration rates of the mussels (p < 0.05). Histological observations revealed varying extents of damage to the gill and digestive gland caused by a single exposure to MPs, which was aggravated by co-exposure to Pb. In addition, co-exposure induced a higher level of oxidative stress, which was reflected by an increase in hydrogen peroxide and malondialdehyde content, and a decrease in antioxidant enzyme activity. Meanwhile, co-exposure poses a significant threat to the immune function of the mussels, as evidenced by induction of hemocytes to produce excess reactive oxygen species (ROS), significantly reducing lysosome activity (p < 0.05), inhibiting the expression of autophagy-related genes, and inducing the expression of apoptosis-related genes, resulting in hemocyte apoptosis. Furthermore, the TLR/MyD88/NFκB signaling pathway is involved in the immune response of mussels to environmental stress. This study provides novel perspectives on the toxicity of MPs combined with Pb in marine animals, as well as the molecular mechanisms underlying their ecotoxicological effects.

Environmental and Sublethal Concentrations of Polystyrene Nanoplastics Induced Antioxidant System, Transcriptomic Responses, and Disturbed Gut Microbiota in Oyster Magallana Hongkongensis

Nanoplastics (NPs) are emerging contaminants having persistent nature, diverse ecological impacts, and potential food safety risks. Here, we examined the ecotoxicity of 80 nm polystyrene nanoplastics (PS-NPs) at environmentally relevant concentrations (ERCs, 10 and 100 μg/L), and sublethal concentrations (SLCs, 500 and 2500 μg/L) in Magallana hongkongensis. Results showed that SLCs significantly (p < 0.05) increased superoxide dismutase (SOD), catalase (CAT), and alkaline phosphatase (AKP) activities and altered tnfα, cat, gst, sod, and se-gpx genetic expressions. Further, PS-NP exposure at both levels reduced beneficial bacteria and increased potentially pathogenic bacteria in the gut. In transcriptomic analysis, 5118 and 4180 differentially expressed genes (DEGs) were identified at ERCs, while 5665 and 4817 DEGs were found at SLCs, respectively. Upregulated DEGs enriched lysosomes, ABC transporters, and apoptosis pathways, while downregulated DEGs enriched ribosomal pathways. Overall, ERCs significantly altered gut microbiota and transcriptomic responses, while SLCs, in addition, also impacted the antioxidant and immune systems.

Physiological response of mussel to rayon microfibers and PCB's exposure: Overlooked semi-synthetic micropollutant?

Rayon microfibers, micro-sized semi-synthetic polymers derived from cellulose, have been frequently detected and reported as "micropollutants" in marine environments. However, there has been limited research on their ecotoxicity and combined effects with persistent organic pollutants (POPs). To address these knowledge gaps, thick-shell mussels (Mytilus coruscus) were exposed to rayon microfibers at 1000 pieces/L, along with polychlorinated biphenyls (PCBs) at 100 and 1000 ng/L for 14 days, followed by a 7-day recovery period. We found that rayon microfibers at the environmentally relevant concentration exacerbated the irreversible effects of PCBs on the immune and digestive systems of mussels, indicating chronic and sublethal impacts. Furthermore, the results of 16 s rRNA sequencing demonstrated significant effects on the community structure, species richness, and diversity of the mussels' intestinal microbiota. The branching map analysis identified the responsive bacteria to rayon microfibers and PCBs belonging to the Proteobacteria, Actinobacteriota, and Bacteroidota phyla. Despite not being considered a conventional plastic, the extensive and increasing use of rayon fibers, their direct toxicological effects, and their interaction with POPs highlight the need for urgent attention, investigation, and regulation to address their contribution to "micropollution".

Effects of ambient UVB light on Pacific oyster Crassostrea gigas mantle tissue based on multivariate data

Ambient ultraviolet radiation (UVB) from solar and artificial light presents serious environmental risks to aquatic ecosystems. The Pacific oyster, Crassostrea gigas, perceives changes in the external environment primarily through its mantle tissue, which contains many nerve fibers and tentacles. Changes within the mantles can typically illustrate the injury of ambient UVB. In this study, a comprehensive analysis of phenotypic, behavioral, and physiological changes demonstrated that extreme UVB radiation (10 W/m²) directly suppressed the behavioral activities of C. gigas. Conversely, under ambient UVB radiation (5 W/m²), various physiological processes exhibited significant alterations in C. gigas, despite the behavior remaining relatively unaffected. Using mathematical model analysis, the integrated analysis of the full-length transcriptome, proteome, and metabolome showed that ambient UVB significantly affected the metabolic processes (saccharide, lipid, and protein metabolism) and cellular biology processes (autophagy, apoptosis, oxidative stress) of the C. gigas mantle. Subsequently, using Procrustes analysis and Pearson correlation analysis, the association between multi-omics data and physiological changes, as well as their biomarkers, revealed the effect of UVB on three crucial biological processes: activation of autophagy signaling (key factors: Ca2+, LC3B, BECN1, caspase-7), response to oxidative stress (reactive oxygen species, heat shock 70, cytochrome c oxidase), and recalibration of energy metabolism (saccharide, succinic acid, translation initiation factor IF-2). These findings offer a fresh perspective on the integration of multi-data from non-model animals in ambient UVB risk assessment.

Micro(nano)plastics in commercial foods: A review of their characterization and potential hazards to human health

Micro (nano)plastics (MNPs) are pollutants of worldwide concern for their ubiquitous environmental presence and associated impacts. The higher consumption of MNPs contaminated commercial food can cause potential adverse human health effects. This review highlights the evidence of MNPs in commercial food items and summarizes different sampling, extraction, and digestion techniques for the isolation of MNPs, such as oxidizing digestion, enzymatic digestion, alkaline digestion and acidic digestion. Various methods for the characterization and quantification of microplastics (MPs) are also compared, including μ-Raman spectroscopy, μ-Fourier transform infrared spectroscopy (FTIR), thermal analysis and Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX). Finally, we share our concerns about the risks of MNPs to human health through the consumption of commercial seafood. The knowledge of the potential human health impacts at a subcellular or molecular level of consuming mariculture products contaminated with MNPs is still limited. Moreover, MNPs are somewhat limited, hard to measure, and still contentious. Due to the nutritional significance of fish consumption, the risk of exposure to MNPs and the associated health effects are of the utmost importance.

Transcriptomic analysis of oxidative stress mechanisms induced by acute nanoplastic exposure in Sepia esculenta larvae

Nanoplastics (NPs), as a new type of pollutant with a size small than 1 μm, are ubiquitous and harmful to organisms. There has been an increasing amount of research concerning the effects of NPs on organisms over recent years, especially on aquatic animals. However, there is a limited study on the impact of NPs on mollusk cephalopods. In this research, Sepia esculenta, belonging to Cephalopoda, Coleoidea, Sepioidea, was selected to explore the effects caused by NPs exposure. The S. esculenta larvae were exposed to polystyrene NPs (PS-NPs) with diameter 50 nm (100 mg/L) for 4 h. The detection of oxidative stress biomarkers displayed an obvious increase in SOD (superoxide dismutase) activity and MDA (malondialdehyde) level. Then, RNA-Seq was performed to explore the oxidative stress response at mRNA level. The transcriptome analysis demonstrated that the expression of 2,570 genes was affected by PS-NPs. Besides, the signaling pathways of ribosome, ribosome biogenesis in eukaryotes, proteasome, and MAPK were enriched. This study not only provides novel references for understanding the mechanisms of oxidative stress response induced by NPs, but also reminds us to follow with interest the influence of acute exposure to NPs.

Combined effect of salinity and hypoxia on digestive enzymes and intestinal microbiota in the oyster Crassostrea hongkongensis

Anthropologic activities caused frequent eutrophication in coastal and estuarine waters, resulting in diel-cycling hypoxia. Given global climate change, extreme weather events often occur, thus salinity fluctuation frequently breaks out in these waters. This study aimed to evaluate the combined effects of salinity and hypoxia on intestinal microbiota and digestive enzymes of Crassostrea hongkongensis. Specifically, we sequenced 16 S rRNA of intestinal microbiota and measured the digestive enzymes trypsin (TRS), lipase (LPS) and amylase (AMY) in oysters exposed for 28 days to three salinities (10, 25 and 35) and two dissolved oxygen conditions, normoxia (6 mg/L) and hypoxia (6 mg/L for 12 h, 2 mg/L for 12 h). Oysters in normoxia and salinity of 25 were treated as control. After 28-day exposure, for microbial components, Fusobacteriota, Firmicutes, Bacteroidota, Proteobacteria and Actinobacteriota comprised the majority for all experimental groups. Compared with the control group, the diversity and structure of intestinal microbiota tended to change in all treated groups. The species richness in C. hongkongensis intestine also changed. It was the most significant that high salinity increased Proteobacteria proportion while low salinity and hypoxia increased Fusobacteriota but decreased Proteobacteria, respectively. Additionally, Actinobacteriota was sensitive and changed under environmental stressor (P < 0.01). The prediction results on intestinal microbiota showed that, all functions of oysters were up-regulated to distinct degrees under low/high salinity with hypoxia. According to the KEGG prediction, cellular processes were more active and energy metabolism upregulated, indicating the adaptation of C. hongkongensis to environmental change. Periodical hypoxia and low/high salinity had complex effect on the digestive enzymes, in which the activity of TRS and LPS decreased while AMY increased. High/low salinity and periodical hypoxia can change the secretion of digestive enzymes and influence intestinal microbial diversity and species richness of C. hongkongensis, deducing the chronic adverse effects on the digestive physiology in long-term exposure.