Metagenomic insights into jellyfish-associated microbiome dynamics during strobilation.

Host-associated microbiomes can play key roles in the metamorphosis of animals. Most scyphozoan jellyfish undergo strobilation in their life cycles, similar to metamorphosis in classic bilaterians. The exploration of jellyfish microbiomes may elucidate the ancestral mechanisms and evolutionary trajectories of metazoan-microbe associations and interactions during metamorphosis. However, current knowledge of the functional features of jellyfish microbiomes remains limited. Here, we performed a genome-centric analysis of associated microbiota across four successive life stages (polyp, early strobila, advanced strobila, and ephyra) during strobilation in the common jellyfish Aurelia coerulea. We observed shifts in taxonomic and functional diversity of microbiomes across distinct stages and proposed that the low microbial diversity in ephyra stage may be correlated with the high expression of the host-derived antimicrobial peptide aurelin. Furthermore, we recovered 43 high-quality metagenome-assembled genomes and determined the nutritional potential of the dominant Vibrio members. Interestingly, we observed increased abundances of genes related to the biosynthesis of amino acids, vitamins, and cofactors, as well as carbon fixation during the loss of host feeding ability, indicating the functional potential of Aurelia-associated microbiota to support the synthesis of essential nutrients. We also identified several potential mechanisms by which jellyfish-associated microbes establish stage-specific community structures and maintain stable colonization in dynamic host environments, including eukaryotic-like protein production, bacterial secretion systems, restriction-modification systems, and clustered regularly interspaced short palindromic repeats-Cas systems. Our study characterizes unique taxonomic and functional changes in jellyfish microbiomes during strobilation and provides foundations for uncovering the ancestral mechanism of host-microbe interactions during metamorphosis.

Isolated Langerhans cell histiocytosis in the stomach of adults: four-case series and literature review.

Langerhans cell histiocytosis (LCH) of the stomach is rare. Moreover, it is usually found in pediatric patients with systemic diseases and may be associated with a poor prognosis. Solitary gastric LCH in adults is extremely rare and is often misdiagnosed or missed. The aim of our study was to review cases of gastric LCH and explore the characteristics of the disease further. A retrospective study of all patients admitted with solitary gastric LCH was conducted between 2013 and 2023. Clinical manifestations, endoscopic and pathological features, immunophenotypes, and molecular changes were collected from medical records. We examined four cases (one female, three males) of gastric LCH. The affected patients were between 33 and 70 years of age. Endoscopically, three patients presented with a solitary polyp or elevated lesions, whereas one patient showed no abnormalities. Under a microscope, all cases showed abnormal proliferation of histiocytoid cells infiltrating in a nested or sheet-like fashion. The tumor cells were medium-sized, with a slightly eosinophilic cytoplasm, irregular or renal-shaped nuclei, folded nuclear membranes, visible nuclear grooves, and the infiltration of inflammatory cells in the background. Immunohistochemically, all lesions expressed CD1a, S-100, langerin, and cyclinD1. One case showed diffuse BRAF V600E positivity. Follow-up data were available for all patients from 4 to 36 months, and all patients were alive without recurrence or progress at the time of manuscript preparation. Combined with previously reported data, solitary adult gastric LCH is more common in male patients, most of whom are asymptomatic or exhibit only mild gastrointestinal symptoms, with a good prognosis. Endoscopy often reveals solitary polyps or protruding lesions; rare cases may progress to multifocal/multisystem lesions, necessitating long-term close follow-up.

Effects of ocean acidification and polystyrene microplastics on the oysters Crassostrea gigas: An integrated biomarker and metabolomic approach.

The adverse impacts of microplastics (MPs) or ocean acidification (OA) on mollusks have been widely reported, however, little is known about their combined effects on mollusks. The oysters Crassostrea gigas were exposed to two sizes of polystyrene MPs with 1 × 104 particles/L (small polystyrene MPs (SPS-MPs): 6 µm, large polystyrene MPs (LPS-MPs): 50-60 µm) at two pH levels (7.7 and 8.1) for 14 days. The antagonistic effects between MPs and OA on oysters were mainly observed. Single SPS-MPs exposure can induce CAT enzyme activity and LPO level in gills, while LPS-MPs exposure alone can increase PGK and PEPCK gene expression in digestive glands. Ocean acidification can increase clearance rate and inhibit antioxidant enzyme activity, whereas combined exposure of OA and SPS-MPs can affect the metabolomic profile of digestive glands. This study emphasized that the potential toxic effects of MPs under the scene of climate change should be concerned.

Physiological and transcriptomic responses of Aurelia coerulea polyps to acidified seawater conditions.

Scyphozoan jellyfish, known for their evolutionary position and ecological significance, are thought to exhibit relatively notable resilience to ocean acidification. However, knowledge regarding the molecular mechanisms underlying the scyphozoan jellyfish response to acidified seawater conditions is currently lacking. In this study, two independent experiments were conducted to determine the physiological and molecular responses of moon jellyfish (Aurelia coerulea) polyps to within- and trans-generational exposure to two reduced pH treatments (pH 7.8 and pH 7.6). The results revealed that the asexual reproduction of A. coerulea polyps significantly declined under acute exposure to pH 7.6 compared with that of polyps at ambient pH conditions. Transcriptomics revealed a notable upregulation of genes involved in immunity and cytoskeleton components. In contrast, genes associated with metabolism were downregulated in response to reduced pH treatments after 6 weeks of within-generational acidified conditions. However, reduced pH treatments had no significant influence on the asexual reproduction of A. coerulea polyps after exposure to acidified conditions over a total of five generations, suggesting that A. coerulea polyps may acclimate to low pH levels. Transcriptomics revealed distinct gene expression profiles between within- and trans-generational exposure groups to two reduced pH treatments. The offspring polyps of A. coerulea subjected to trans-generational acidified conditions exhibited both upregulated and downregulated expression of genes associated with metabolism. These physiological and transcriptomic characteristics of A. coerulea polyps in response to elevated CO2 levels suggest that polyps produced asexually under acidified conditions may be resilient to such conditions in the future.

Biodiversity and distribution patterns of blooming jellyfish in the Bohai Sea revealed by eDNA metabarcoding.

BACKGROUND: The mass occurrence of scyphozoan jellyfish severely affects marine ecosystems and coastal economies, and the study of blooming jellyfish population dynamics has emerged in response. However, traditional ecological survey methods required for such research have difficulties in detecting cryptic life stages and surveying population dynamics owing to high spatiotemporal variations in their occurrence. The environmental DNA (eDNA) technique is an effective tool for overcoming these limitations. RESULTS: In this study, we investigated the biodiversity and spatial distribution characteristics of blooming jellyfish in the Bohai Sea of China using an eDNA metabarcoding approach, which covered the surface, middle, and bottom seawater layers, and sediments. Six jellyfish taxa were identified, of which Aurelia coerulea, Nemopilema nomurai, and Cyanea nozakii were the most dominant. These three blooming jellyfish presented a marked vertical distribution pattern in the offshore regions. A. coerulea was mainly distributed in the surface layer, whereas C. nozakii and N. nomurai showed a upper-middle and middle-bottom aggregation, respectively. Horizontally, A. coerulea and C. nozakii were more abundant in the inshore regions, whereas N. nomurai was mainly distributed offshore. Spearman's correlation analysis revealed a strong correlation between the eDNA of the three dominant blooming jellyfish species and temperature, salinity, and nutrients. CONCLUSIONS: Our study confirms the applicability of the eDNA approach to both biodiverstiy evaluation of blooming jellyfish and investigating their spatial distribution, and it can be used as a supplementary tool to traditional survey methods.

The physiological response of the clam Ruditapes philippinarum and scallop Chlamys farreri to varied concentrations of microplastics exposure.

Microplastics (MPs) pollution's impact on the marine ecosystem is widely recognized. This study compared the effects of polyethylene (PE) and polyethylene terephthalate (PET) on two bivalve species, Ruditapes philippinarum (clam) and Chlamys farreri (scallop), at two particle concentrations (10 and 1000 µg/L). MPs were found in the digestive glands and gills of both species. Although clearance rates showed no significant changes, exposure to different MPs caused oxidative stress, energy disruption, and lipid metabolism disorders in both clam and scallop. Histopathological damage was observed in gills and digestive glands. IBR values indicated increasing toxicity with concentration, with PET being more toxic than PE. WOE model suggested increasing hazard with concentration, highlighting higher PET toxicity on clam digestive glands. In contrast, PE hazard increased in gills, showing different species responses. R. philippinarum exhibited higher sensitivity to MPs than C. farreri, providing insights for assessing ecological risk under realistic conditions and stress conditions.

The pollution characteristics and risk assessment of microplastics in mollusks collected from the Bohai Sea.

Microplastics (MPs) pollution in the marine environment has become a global problem. In this study, a number of 21 mollusk species (n = 2006) with different feeding habits were collected from 11 sites along the Bohai Sea for MPs uptake analysis. The MPs in mollusk samples were isolated and identified by micro-Fourier Transform Infrared Spectroscopy (µ-FTIR), and an assessment of the health risks of MPs ingested by mollusk consumption is also conducted. Approximately 91.9 % of the individuals among all the collected species inhaled MPs, and there was an average abundance of 3.30 ± 2.04 items·individual-1 or 1.04 ± 0.74 items·g-1 of wet weight. The shape of MPs was mainly fiber, and a total number of 8 polymers were detected, of which rayon had the highest detection rate (58.3 %). The highest abundance, uptake rate and polymer composition of MPs was observed in creeping types, suggesting that they might ingest these MPs from their food. The gastropod Siphonalia subdilatata contains the highest levels of MPs, which may increase the risk of human exposure if consumed whole without removing the digestive gland. The polymer risk level of MPs in these mollusks was Level III (H = 299), presenting harmful MPs such as polyvinyl chloride. In terms of human exposure risk, the average risk of human exposure to MPs through consumption of Bohai mollusks is estimated to be 3399 items·(capita·year)-1 (424-9349 items·(capita·year)-1). Overall, this study provides a basis for the ecological and health Risk assessment of MPs in mollusks collected from the coastline of China.

Interactive effects of multiple antibiotic residues and ocean acidification on physiology and metabolome of the bay scallops Argopecten irradians irradians.

Coastal areas are confronted with compounding threats arising from both climatic and non-climatic stressors. Antibiotic pollution and ocean acidification are two prevalently concurrent environmental stressors. Yet their interactive effects on marine biota have not been investigated adequately and the compound hazard remain obscure. In this study, bay scallops Argopecten irradians irradians were exposed to multiple antibiotics (sulfamethoxazole, tetracycline, oxytetracycline, norfloxacin, and erythromycin, each at a concentration of 1 µg/L) combined with/without acidic seawater (pH 7.6) for 35 days. The single and interactive effects of the two stressors on A. irradians irradians were determined from multidimensional bio-responses, including energetic physiological traits as well as the molecular underpinning (metabolome and expressions of key genes). Results showed that multiple antibiotics predominantly enhanced the process of DNA repair and replication via disturbing the purine metabolism pathway. This alternation is perhaps to cope with the DNA damage induced by oxidative stress. Ocean acidification mainly disrupted energy metabolism and ammonia metabolism of the scallops, as evidenced by the increased ammonia excretion rate, the decreased O:N ratio, and perturbations in amino acid metabolism pathways. Moreover, the antagonistic effects of multiple antibiotics and ocean acidification caused alternations in the relative abundance of neurotransmitter and gene expression of neurotransmitter receptors, which may lead to neurological disorders in scallops. Overall, the revealed alternations in physiological traits, metabolites and gene expressions provide insightful information for the health status of bivalves in a natural environmental condition under the climate change scenarios.

Intrinsic and extrinsic pathways of apoptosis induced by multiple antibiotics residues and ocean acidification in hemocytes of scallop Argopecten irradians irradians: An interactionist perspective.

The increasing prevalence of antibiotics in seawater across global coastal areas, coupled with the ocean acidification induced by climate change, present a multifaceted challenge to marine ecosystems, particularly impacting the key physiological processes of marine organisms. Apoptosis is a critical adaptive response essential for maintaining cellular homeostasis and defending against environmental threats. In this study, bay scallops Argopecten irradians irradians were exposed to multiple antibiotics (sulfamethoxazole, tetracycline, oxytetracycline, norfloxacin, and erythromycin, each at a concentration of 1 µg/L) combined with/without acidic seawater (pH 7.6) for 35 days. The single and interactive effects of the two stressors on apoptosis and the underlying mechanisms in hemocytes of A. irradians irradians were determined through flow cytometry analysis, comet assay, oxidative stress biomarkers analysis, and transcriptome analysis. Results showed that apoptosis could be triggered by either AM exposure or OA exposure, but through different pathways. Exposure to AM leads to mitochondrial dysfunction and oxidative damage, which in turn triggers apoptosis via a series of cellular events in both intrinsic and extrinsic pathways. Conversely, while OA exposure similarly induced apoptosis, its effects are comparatively subdued and are predominantly mediated through the intrinsic pathway. Additionally, the synergistic effects of AM and OA exposure induced pronounced mitochondrial dysfunction and oxidative damages in the hemocytes of A. irradians irradians. Despite the evident cellular distress and the potential initiation of apoptotic pathways, the actual execution of apoptosis appears to be restrained, which might be attributed to an energy deficit within the hemocytes. Our findings underscore the constrained tolerance capacity of A. irradians irradians when faced with multiple environmental stressors, and shed light on the ecotoxicity of antibiotic pollution in the ocean under prospective climate change scenarios.

Environmental and molecular regulation of diapause formation in a scyphozoan jellyfish.

Understanding the mechanisms underlying diapause formation is crucial for gaining insight into adaptive survival strategies across various species. In this study, we aimed to uncover the pivotal role of temperature and food availability in regulating diapausing podocyst formation in the jellyfish Aurelia coerulea. Furthermore, we explored the cellular and molecular basis of diapause formation using single-cell RNA sequencing. Our results showed cell-type-specific transcriptional landscapes during podocyst formation, which were underscored by the activation of specific transcription factors and signalling pathways. In addition, we found that the heat shock protein-coding genes HSC70 and HSP90a potentially act as hub genes that regulate podocyst formation. Finally, we mapped the single-cell atlas of diapausing podocysts and identified cell types involved in metabolism, environmental sensing, defence and development that may collectively contribute to the long-term survival and regulated excystment of diapausing podocysts. Taken together, the findings of this study provide novel insights into the molecular mechanisms that regulate diapause formation and contributes to a better understanding of adaptive survival strategies in a variety of ecological contexts.

Microbiota regulates life-cycle transition and nematocyte dynamics in jellyfish.

Jellyfish represent one of the most basal animal groups with complex life cycles. The polyp-to-medusa transition, termed strobilation, is the pivotal process that determines the switch in swimming behavior and jellyfish blooms. Their microbiota plays an essential role in strobilation. Here, we investigated microbiota-mediated host phenotype dynamics during strobilation in the jellyfish Aurelia coerulea via antibiotic-induced microbiome alteration. Microbial depletion delayed the initiation of strobilation and resulted in fewer segments and ephyrae, which could be restored via microbial recolonization. Jellyfish-associated cyanobacteria, which were eliminated by antibiotics in the polyp stage, had the potential to supply retinal and trigger the retinoic acid signaling cascade, which drove the strobilation process. The microbiota regulated nematocyte development and differentiation, influencing the feeding and growth of the jellyfish. The findings improve our understanding of jellyfish-microbe interactions and provide new insights into the role of the microbiota in shaping feeding behavior through nematocyte dynamics.

Application of environmental DNA metabarcoding and quantitative PCR to detect blooming jellyfish in a temperate bay of northern China.

Frequently occurring jellyfish blooms have severe impacts on the socioeconomics of coastal areas, which stress the importance of early detection and assessments of blooming jellyfish taxa. Environmental DNA (eDNA) techniques (quantitative PCR and eDNA metabarcoding) have the advantage of high sensitivity and are an emerging powerful tool for investigations of target species. However, a comprehensive analysis of the biodiversity and biomass of jellyfish taxa in the target area by combining the two eDNA techniques is still lacking. Here, we developed eDNA metabarcoding and quantitative PCR for the detection and assessment of jellyfish taxa in the temperate Yantai Sishili Bay (YSB) and estimated the spatial distribution of Aurelia coerulea. Species-specific quantitative PCR assays targeting the mitochondrial cytochrome c oxidase subunit I gene of A. coerulea were developed. Additionally, eDNA metabarcoding based on the mitochondrial 16S rDNA sequences identified six jellyfish species in YSB. Moreover, our results indicate that A. coerulea aggregations were more likely to occur in the inner part of the bay than in the outer part, and they gathered in the bottom layer of seawater rather than in the surface layer. Our results demonstrate the potential of two eDNA techniques in jellyfish biomass investigation and jellyfish taxa detection. These eDNA techniques may contribute to the discovery of jellyfish aggregation so as to achieve early warning of large-scale jellyfish blooms in coastal areas.

Genome-wide characterization of regulator of chromosome condensation 1 (RCC1) gene family in Artemisia annua L. revealed a conservation evolutionary pattern.

BACKGROUND: Artemisia annua is the major source for artemisinin production. The artemisinin content in A. annua is affected by different types of light especially the UV light. UVR8, a member of RCC1 gene family was found to be the UV-B receptor in plants. The gene structures, evolutionary history and expression profile of UVR8 or RCC1 genes remain undiscovered in A. annua. RESULTS: Twenty-two RCC1 genes (AaRCC1) were identified in each haplotype genome of two diploid strains of A. annua, LQ-9 and HAN1. Varied gene structures and sequences among paralogs were observed. The divergence of most RCC1 genes occurred at 46.7 - 51 MYA which overlapped with species divergence of core Asteraceae during the Eocene, while no recent novel RCC1 members were found in A. annua genome. The number of RCC1 genes remained stable among eudicots and RCC1 genes underwent purifying selection. The expression profile of AaRCC1 is analogous to that of Arabidopsis thaliana (AtRCC1) when responding to environmental stress. CONCLUSIONS: This study provided a comprehensive characterization of the AaRCC1 gene family and suggested that RCC1 genes were conserved in gene number, structures, constitution of amino acids and expression profiles among eudicots.

Alteration of microbial mediated carbon cycle and antibiotic resistance genes during plastisphere formation in coastal area.

Microorganisms can attach on the surface of microplastics (MPs) through biological fouling process to form a diverse community called the "plastisphere", which has attracted extensive attention. Although the microbial structure and composition of biofilm have been studied, the knowledge of its microbial function and ecological risk is still limited. In this study, we investigated how the surface properties of MPs affect the biofilm communities and metabolic features under different environmental conditions, and explored the biofilm enrichment of antibiotic resistance genes (ARGs). The results showed that the incubation time, habitat and MPs aging state significantly influenced the structure and composition of biofilm microbial communities, and a small amount of pathogens have been found in the MPs-attached biofilm. The microbial carbon utilization capacity of the biofilm in different incubation habitats varies greatly with highest metabolism capacity appear in the river. The utilization efficiency of different carbon sources is polymer > carbohydrate > amino acid > carboxylic acids > amine/amide, which indicates that the biofilm communities have selectivity between different types of carbon sources. More importantly, ARGs were detected in all the MPs samples and showed a trend of estuary > river > marine. The aged MPs can accumulate more ARGs than the virgin items. In general, MPs in the aquatic environment may become a carrier for pathogens and ARGs to spread to other environment, which may enhance their potential risks to the ecosystem and human health.

Development of a trace quantitative method to investigate caffeine distribution in the Yellow and Bohai Seas, China, and assessment of its potential neurotoxic effect on fish larvae.

Caffeine is an emerging contaminant in aquatic environments. The study utilized a validated method to investigate the presence and distribution of caffeine in the surface water of the Yellow and Bohai Seas, urban rivers, and the Yantai estuary area. The analytical method conforms to EPA guidelines and exhibits a limit of quantification that is 200 times lower than that of prior investigations. The study revealed that the highest concentration of 1436.4 ng/L was found in convergence of ocean currents in the Yellow and Bohai Seas. The presence of larger populations and the process of urban industrialization have been observed to result in elevated levels of caffeine in offshore regions, confirming that caffeine can serve as a potential indicator of anthropogenic contamination. Fish larvae exhibited hypoactivity in response to caffeine exposure at environmentally relevant concentrations. The study revealed that caffeine pollution can have adverse effects on marine and offshore ecosystems. This emphasizes the importance of decreasing neurotoxic pollution in the aquatic environment.

Effects of exposure to nanoplastics on the gill of mussels Mytilus galloprovincialis: An integrated perspective from multiple biomarkers.

The pervasive presence of nanoplastics (NPs) in marine environments poses a threat to marine organisms. Gills, as the organ in direct contact with the environment in marine invertebrates, maybe the first to accumulate NPs. To date, the toxic effects of NPs on the gills of marine invertebrates are still largely unknown. In this study, the response of multiple biomarkers (i.e., total antioxidant capacity, the activity of acetylcholine, ion content and transport enzyme, metabolic enzymes, and lipids content) in mussels Mytilus galloprovincialis exposed to polystyrene nanoplastics (PS-NPs) for 7 days were evaluated. Significant inductions of total antioxidant capacity (T-AOC) and inhibition of acetylcholine (AChE) activity were detected after 7 days of PS-NPs exposure. PS-NPs also triggered significant alteration in ion content (Na+ and K+) and suppressed the activities of the ion transport enzyme (Na+/K+-ATPase). Moreover, we found the activity of metabolic enzymes (succinate dehydrogenase and pyruvate kinase) and lipids content (triacylglycerol and cholesterol) were significantly altered, suggesting the interference of PS-NPs on energy metabolism and lipid metabolism. This investigation provides substantial information to understand the physical responses of invertebrate gills to PS-NPs exposure. Given the crucial ecological roles of invertebrates, the presence of PS-NPs in the marine environment may have far-reaching impacts on population abundance, biodiversity, and stability of the marine ecosystem.

Dynamics of Benthic Nitrate Reduction Pathways and Associated Microbial Communities Responding to the Development of Seasonal Deoxygenation in a Coastal Mariculture Zone.

Intensive mariculture activities result in eutrophication and enhance coastal deoxygenation. Deoxygenation profoundly influences nitrate reduction processes and further the fate of nitrogen (N) in coastal systems. Herein, 15N isotope labeling, real-time PCR, and high-throughput sequencing techniques were jointly used to investigate the participation and seasonal dynamics of sediment nitrate reduction pathways and the succession of functional microbial communities during the development of seasonal deoxygenation in a coastal aquaculture zone. Denitrification dominated benthic nitrate reduction (46.26-80.91%). Both denitrification and dissimilatory nitrate reduction to ammonium were significantly enhanced by summer deoxygenation (dissolved oxygen levels fell to 2.94 ± 0.28 mg L-1), while anammox remained unchanged. The abundance of the nitrous oxide reductase gene nosZ increased during deoxygenation. The community of the nosZ gene was sensitive to deoxygenation, with Azospirillum and Ruegeria accounting for the majority. Pelobacter was overwhelming in the nrfA gene (encoding dissimilatory nitrite reductase) community, which was less affected by deoxygenation. The variations of benthic nitrate reduction processes were driven by bottom water oxygen combined with temperature, chlorophyll a, and microbial gene abundances and community compositions. Our results implicated that seasonal oxygen-deficient zones could be substantial N sinks of coastal ecosystems and important for N balance. Effective management measures need to be developed to avoid further exacerbation of coastal deoxygenation and maintain the sustainable development of mariculture.

Culture-Independent Single-Cell PacBio Sequencing Reveals Epibiotic Variovorax and Nucleus Associated Mycoplasma in the Microbiome of the Marine Benthic Protist Geleia sp. YT (Ciliophora, Karyorelictea).

Microbes in marine sediments constitute up to five-sixths of the planet's total biomass, but their diversity is little explored, especially for those forming associations with unicellular protists. Heterotrophic ciliates are among the most dominant and diversified marine benthic protists and comprise hotspot niches of bacterial colonization. To date, studies using culture-independent single-cell approaches to explore microbiomes of marine benthic ciliates in nature are almost absent, even for the most ubiquitous species. Here, we characterize the major bacterial groups associated with a representative marine benthic ciliate, Geleia sp. YT, collected directly from the coastal zone of Yantai, China. PacBio sequencing of the nearly full-length 16Sr RNA genes was performed on single cells of Geleia. Fluorescence in situ hybridization (FISH) analysis with genus-specific probes was further applied to locate the dominant bacterial groups. We identified a Variovorax-like bacterium as the major epibiotic symbiont residing in the kineties of the ciliate host. We provide evidence of a nucleus-associated bacterium related to the human pathogen Mycoplasma, which appeared prevalently in the local populations of Geleia sp. YT for 4 months. The most abundant bacterial taxa associated with Geleia sp. YT likely represent its core microbiome, hinting at the important roles of the ciliate-bacteria consortium in the marine benthos. Overall, this work has contributed to the knowledge of the diversity of life in the enigmatic marine benthic ciliate and its symbioses.

Combined effects of salinity and polystyrene microplastics exposure on the Pacific oysters Crassostrea gigas: Oxidative stress and energy metabolism.

Microplastics (MPs) pollution and salinity variation are two environmental stressors, but their combined effects on marine mollusks are rarely known. Oysters (Crassostrea gigas) were exposed to 1 × 104 particles L-1 spherical polystyrene MPs (PS-MPs) of different sizes (small polystyrene MPs (SPS-MPs): 6 µm, large polystyrene MPs (LPS-MPs): 50-60 µm) under three salinity levels (21, 26, and 31 psu) for 14 days. Results demonstrated that low salinity reduced PS-MPs uptake in oysters. Antagonistic interactions between PS-MPs and low salinity mainly occurred, and partial synergistic effects were mainly induced by SPS-MPs. SPS-MPs induced higher lipid peroxidation (LPO) levels than LPS-MPs. In digestive glands, low salinity decreased LPO levels and glycometabolism-related gene expression, which was related to salinity levels. Low salinity instead of MPs mainly affected metabolomics profiles of gills through energy metabolism and osmotic adjustment pathway. In conclusion, oysters can adapt to combined stressors through energy and antioxidative regulation.