Microplastics (MPs) are prevalent throughout the oceans and pose a significant global environmental concern due to their detrimental effects on various living organisms. While researchers have investigated the toxicity mechanisms of MPs in marine species, there is a need for a more comprehensive understanding, particularly regarding the potential adverse effects on the growth and metabolism of bivalves. In this study, indoor exposure experiments were conducted on Pinctada fucata martensii to examine the impact of commercial polyvinyl chloride (PVC)-MPs (50 μm, 15 mg/L). The aim was to determine the effects of MPs on the hepatopancreas metabolism of P. f. martensii. Non-targeted metabolomics analysis indicated alterations in the hepatopancreatic metabolic of P. f. martensii following exposure to PVC-MPs. A total of 32, 27, and 154 differential metabolites (SDM) were identified in EG (1-d) vs CG (1-d), EG (15-d) vs CG (15-d), and EG (1-d) vs EG (15-d), respectively (VIP > 1 and P < 0.05). Further examination of metabolic pathways revealed that PVC-MPs disrupted the metabolism of amino acids, particularly alanine, aspartic acid, and glutamic acid metabolism; this suggests that the organism may have developed neurotoxicity. Sphingolipid metabolites showed a significant up-regulation in both EG (15-d) vs CG (15-d), as well as in EG (1-d) vs EG (15-d), indicating lipid peroxidation in the hepatopancreas of P. f. martensii following PVC-MPs exposure. Additionally, in EG (1-d) vs CG (1-d), starch and sucrose metabolism were significantly inhibited, glycolysis or gluconeogenesis pathways were promoted, and changes in energy metabolism were promoted. This study sheds light on the impact of MPs on the metabolism of bivalves, offering fresh insights into the detrimental effects of MPs on aquatic organisms.

Microplastics (MPs), particularly polyvinyl chloride microplastics (PVC MPs) have become a notable environmental pollutant that affect various marine organisms such as Pinctada fucata martensii. As filter feeders, these bivalves consume significant volumes of water containing MPs, leading to contact with and ingestion of MPs. Moreover, given the ecological and economic importance of P. f. martensii in artificial pearl production, investigating the effects of PVC MPs exposure is crucial. This study aimed to investigate the effects of PVC MPs exposure on nucleus retention, pearl formation, oxidative stress by examining superoxide dismutase (SOD) activity, catalase (CAT) activity, lipid peroxidation (LPO), and total antioxidant capacity (TAOC) of P. f. martensii, while also exploring transcriptomic changes at different concentrations and exposure time points, including a recovery period. The pearl oysters were exposed to PVC MPs at concentrations of 1-, 2.5-, and 5-mg PVC MPs/L for 10 d followed by 6 d of recovery. After 1-, 4-, 10-d of exposure, and additional 6 d of recovery, samples were taken and analyzed. Findings revealed that only prolonged exposure (10 d) to PVC MPs affected SOD activity, while CAT activity, LPO, and TAOC remained unaffected throughout the experiment. Notably, SOD activity was restored during the 6-d recovery phase. Transcriptome analysis highlighted significant gene alterations linked to various pathways, affecting cellular processes, environmental information processing, genetic information processing, metabolism, and organismal systems, with an increase in pathway-related genes during recovery, implying a potential role of PVC MPs as gene inhibitors. This study provided insights into the effects of PVC MPs on P. f. martensii, shedding light on pearl retention, oxidative systems, and molecular pathways influenced by PVC MPs. Additionally, it contributed novel information on potential MPs exposure biomarkers, particularly relevant to marine organisms like P. f. martensii.

Salinity significantly affects shellfish metabolism and growth. In this study, we evaluated the characterization of metabolomic differences in the juvenile black-shelled pearl oyster, Pinctada fucata martensii, under 15‰ (LSG), 25‰ (CG), and 35‰ (HSG) salinity conditions. Non-targeted metabolomics analyses revealed that salinity stress altered the metabolism of pearl oyster. A total of 229 significant differential metabolites (SDMs) were identified between LSG and CG via an in-house MS2 database, 241 SDMs were identified between LSG and HSG, and 50 SDMs were identified between CG and HSG. The pathway analysis showed that 21 metabolic pathways were found between LSG and CG, such as arginine and proline metabolism, glycerophospholipid metabolism, and pentose and glucuronide interconversion. A total of 23 metabolic pathways were obtained between LSG and HSG, such as aspartate, alanine, and glutamate metabolism. Only aminoacyl-tRNA biosynthesis, cysteine and methionine metabolism, and biotin metabolism were enriched between CG and HSG. A further integrated analysis suggested that amino acid metabolism might participate in osmoregulation and energy metabolism to respond to salinity stress in P. f. martensii, and the metabolic pathways differed under varying salinity stress conditions. In addition, low salinity stress might promote apoptosis in pearl oysters. Altogether, these results clarify the salinity tolerance mechanism of pearl oysters.

Microplastics (MPs) have recently attracted attention as an emerging pollutant. To investigate the effects of microplastics on the pearl oyster Pinctada fucata martensii (P. f. martensii) polyvinyl chloride microplastics (PVC-MPs) were used. We aimed to investigate the effect of PVC-MPs on the oxidation and reduction system by using the superoxide dismutase (SOD), malondialdehyde (MDA), reduced glutathione (GSH), and total antioxidant capacity (T-AOC); the immune system using acid phosphatase (ACP) and alkaline phosphatase (AKP); and the digestive system using amylase and protease as biomarkers. P. f. martensii were exposed to PVC-MPs at 0.15 mg/L, 1.5 mg/L, and 15 mg/L. Exposure to PVC-MPs increased the SOD activity and MDA content in the 15 mg/L dose group in 15 d compared to the control group. When compared with the control and other groups, MDA content and GSH content in the 0.15 mg/L group were higher on day 10. The T-AOC and AKP in all treatment groups were lower than the control group throughout the experiment, except in 1.5 mg/L and 15 mg/L groups in 15 d. The ACP activity increased with time except in the 0.15 mg/L group. The amylase and protease activity had an opposite pattern with amylase activity decreasing with time except in the 1.5 mg/L group in 15 d while protease increased with time except in the 0.15 mg/L group in 15 d group. The results indicate that PVC-MPs exposure induced oxidative stress, distorted the immune system, and digestive functions of P. f. martensii. The results help to understand the effects of MPs on the physiological responses of P. f. martensii.

Microplastics have become a widespread concern within marine environments and are particularly evident in aquaculture regions that are characterized by plastic accumulation. This study employed 16S rDNA sequencing to investigate the dynamic succession of microbial communities colonizing polyvinyl chloride (PVC), polystyrene (PS), and polyamide (PA) microplastics in seawater, when subjected to varying exposure durations in the Liusha Bay aquaculture region. Results revealed that the composition of microplastics microbial communities varied remarkably across geographical locations and exposure times. With an increase in exposure duration, both the diversity and richness of bacterial communities colonizing microplastics significantly increased, microbial communities show adaptations to the plastisphere. The type of microplastics had a significant effect on the community structure characteristicsof bacteria attached to their surfaces, with inconsistent trends in the relative abundance of different genera on different substrates. Notably, microplastic surfaces harbored a significant abundance of hydrocarbon-degrading bacteria, exemplified by Erythrobacter. These findings underscore the potential of microplastics as unique microbial niches. Meanwhile, long-term exposure experiments also offer the possibility of screening for plastic-degrading bacteria. In addition, the presence of the pathogenic bacterium Vibrio was detected in all microplastic samples, implying that microplastics could serve as carriers for pathogenic dissemination. This underscores the urgency of addressing the risk posed by the proliferation of harmful bacteria on microplastic surfaces. Overall, this study enhances our understanding of microbial community dynamics on microplastics under diverse conditions. It contributes to the broader comprehension of plastisphere microbial ecosystems in the marine environment, thereby addressing critical environmental implications.