Environmental and social framework to protect marine bivalves under extreme weather events.

Rising ocean temperatures, a consequence of anthropogenic climate change, are increasing the frequency, intensity, and magnitude of extreme marine heatwaves (MHWs). These persistent anomalous warming events can have severe ecological and socioeconomic impacts, threatening ecologically and economically vital organisms such as bivalves and the ecosystems they support. Developing robust environmental and social frameworks to enhance the resilience and adaptability of bivalve aquaculture is critical to ensuring the sustainability of this crucial food source. This review synthesizes the current understanding of the physiological and ecological impacts of MHWs on commercially important bivalve species farmed globally. We propose an integrated risk assessment framework that encompasses environmental monitoring, farm-level preparedness planning, and community-level social support systems to safeguard bivalve aquaculture. Specifically, we examine heatwave prediction models, local mitigation strategies, and social programs that could mitigate the impacts on bivalve farms and vulnerable coastal communities economically dependent on this fishery. At the farm level, adaptation strategies such as selective breeding for heat-tolerant strains, optimized site selection, and adjustments to culture practices can improve survival outcomes during MHWs. Robust disease surveillance and management programs are essential for early detection and rapid response. Furthermore, we highlight the importance of stakeholder engagement, knowledge exchange, and collaborative governance in developing context-specific, inclusive, and equitable safeguard systems. Proactive measures, such as advanced forecasting tools like the California Current Marine Heat Wave Tracker developed by NOAA's Southwest Fisheries Science Center, enable preemptive action before losses occur. Coordinated preparation and response, underpinned by continuous monitoring and adaptive management, promise to protect these climate-vulnerable food systems and coastal communities. However, sustained research, innovation, and cross-sector collaboration are imperative to navigate the challenges posed by our rapidly changing oceans.

The physiological responses to titanium dioxide nanoparticles exposure in pearl oysters (Pinctada fucata martensii).

To evaluate the physiological responses to titanium dioxide nanoparticles exposure in pearl oysters (Pinctada fucata martensii), pearl oysters were exposed for 14 days to different levels (0.05, 0.5, and 5 mg/L) of nano-TiO2 suspensions, while a control group did not undergo any nano-TiO2 treatment. And then recovery experiments were performed for 7 days without nano-TiO2 exposure. At days 1, 3, 7, 14, 17, and 21, hepatopancreatic tissue samples were collected and used to examine the activities of protease, amylase, lipase, catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), lysozyme (LYS), alkaline phosphatase (AKP), and acid phosphatase (ACP). The microstructure of the nacreous layer in shell was also analyzed by scanning electron microscopy. Results showed that pearl oysters exposed to 5 mg/L of TiO2 nanoparticles had significantly lower protease, amylase, and lipase activities and significantly higher CAT, SOD, GPx, LYS, ACP, and AKP activities than control pearl oysters did even after 7-day recovery (P-values <0.05). Pearl oysters exposed to 0.5 mg/L or 0.05 mg/L of TiO2 nanoparticles had lower protease, amylase, and lipase activities and higher CAT, SOD, GPx, LYS, ACP, and AKP activities than control pearl oysters did during the exposure period. After 7-day recovery, no significant differences in protease, lipase, SOD, GPx, CAT, ACP, AKP, or LYS activities were observed between pearl oysters exposed to 0.05 mg/L of TiO2 nanoparticles and control pearl oysters (P-values >0.05). In the period from day 7 to day 14, indistinct and irregular nacreous layer crystal structure in shell was observed. This study demonstrates that TiO2 nanoparticles exposure influences the levels of digestion, immune function, oxidative stress, and biomineralization in pearl oysters, which can be partially and weakly alleviated by short-term recovery. These findings contribute to understanding the mechanisms of action of TiO2 nanoparticles in bivalves. However, studies should evaluate whether a longer recovery period can restore to their normal levels in the future.

Effects of titanium dioxide nanoparticle exposure on the gut microbiota of pearl oyster (Pinctada fucata martensii).

With the advancement of nanotechnology and the growing utilization of nanomaterials, titanium dioxide (TiO2) has been released into aquatic environments, posing potential ecotoxicological risks to aquatic organisms. In this study, the toxicological effects of TiO2 nanoparticles were investigated on the intestinal health of pearl oyster (Pinctada fucata martensii). The pearl oysters were subjected to a 14-day exposure to 5-mg/L TiO2 nanoparticle, followed by a 7-day recovery period. Subsequently, the intestinal tissues were analyzed using 16S rDNA high-throughput sequencing. The results from LEfSe analysis revealed that TiO2 nanoparticle increased the susceptibility of pearl oysters to potential pathogenic bacteria infections. Additionally, the TiO2 nanoparticles led to alterations in the abundance of microbial communities in the gut of pearl oysters. Notable changes included a decrease in the relative abundance of Phaeobacter and Nautella, and an increase in the Actinobacteria, which could potentially impact the immune function of pearl oysters. The abundance of Firmicutes and Bacteroidetes, as well as the expression of genes related to energy metabolism (AMPK, PK, SCS-1, SCS-2, SCS-3), were down-regulated, suggesting that TiO2 nanoparticles exposure may affect the digestive and energy metabolic functions of pearl oysters. Furthermore, the short-term recovery of seven days did not fully restore these levels to normal. These findings provide crucial insights and serve as an important reference for understanding the toxic effects of TiO2 nanoparticles on bivalves.

Exploring changes in microplastic-associated bacterial communities with time, location, and polymer type in Liusha Bay, China.

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 16 S 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.

Elucidating responses of the intertidal clam Ruditapes philippinarum to compound extreme oceanic events.

Ocean acidification and heatwaves caused by rising CO2 affect bivalves and other coastal organisms. Intertidal bivalves are vital to benthic ecosystems, but their physiological and metabolic responses to compound catastrophic climate events are unknown. Here, we examined Manila clam (Ruditapes philippinarum) responses to low pH and heatwaves. Biochemical and gene expression demonstrated that pH and heatwaves greatly affect physiological energy enzymes and genes expression. In the presence of heatwaves, Manila clams expressed more enzymes and genes involved in physiological energetics regardless of acidity, even more so than in the presence of both. In this study, calcifying organisms' biochemical and molecular reactions are more susceptible to temperature rises than acidity. Acclimation under harsh weather conditions was consistent with thermal stress increase at lower biological organization levels. These substantial temporal biochemical and molecular patterns illuminate clam tipping points. This study helps us understand how compound extreme weather and climate events affect coastal bivalves for future conservation efforts.

Bacterial community profiling associated with pearl culture facilities of Liusha Bay, the largest marine pearl culture base on the western Guangdong coast, South China.

A large number of aquaculture facilities produced during the farming process are made of plastics. These plastics can be a distinct habitat for bacteria due to their unique materials. Therefore, this paper focuses on plastic aquaculture facilities and investigates the impact of bacterial accumulation on plastic surfaces. In this study, the high-throughput sequencing of 16S rRNA was conducted to investigate bacterial community profiling associated with the pearl culture facilities (cultured net cages and foam buoys) and surrounding water of Liusha Bay. Alpha diversity analysis showed that the richness and diversity indexes of bacterial communities in pearl culture facilities were higher than those in the aquatic environment. The richness and diversity indexes of bacterial communities were different between cultured net cages and foam buoys. Spatially influenced bacterial communities attached to pearl culture facilities varied between aquaculture areas. Thus, plastic has become a habitat for bacteria, floating in the marine environment and providing a favorable living environment for marine microorganisms and specific preferences for different substrate types. The relative abundance of certain functions on the attached bacterial community of the culture facility was high, which suggested that plastics did not only alter community structure but also influenced bacterial function. In addition, we detected small amounts of pathogenic bacteria, such as Vibrio and Bruegeria, in pearl culture facilities and surrounding seawater, suggesting that plastics can act as vectors for potentially pathogenic bacteria that may have an impact on the development of aquaculture. Our understanding of plastic ecology has been enriched by the discovery of the various microbial assemblages that can occur in aquaculture facilities.

Integrated transcriptomic and metabolomic analysis reveals the response of pearl oyster (Pinctada fucata martensii) to long-term hypoxia.

The frequency at which organisms are exposed to hypoxic conditions in aquatic environments is increasing due to coastal eutrophication and global warming. To reveal the effects of long-term hypoxic stress on metabolic changes of pearl oyster, commonly known as Pinctada (Pinctada fucata martensii), the present study performed the integrated analysis of transcriptomics and metabolomics to investigate the global changes of genes and metabolites following 25 days hypoxia challenge. Transcriptome analysis detected 1108 differentially expressed genes (DEGs) between the control group and the hypoxia group. The gene ontology (GO) analysis of DEGs revealed that they are significantly enriched in functions such as "microtubule-based process", "histone (H3-K4, H3-K27, and H4-K20) trimethylation", "histone H4 acetylation", "kinesin complex", and "ATPase activity", and KEGG pathway functions, such as "DNA replication", "Apoptosis", and "MAPK signaling pathways". Metabolome analysis identified 68 significantly different metabolites from all identified metabolites, and associated with 25 metabolic pathways between the control and hypoxia groups. These pathways included aminoacyl-tRNA biosynthesis, arginine and proline metabolism, and phenylalanine metabolism. Our integrated analysis suggested that pearl oysters were subject to oxidative stress, apoptosis, immune inhibition, and neuronal excitability reduction under long-term hypoxic conditions. We also found a remarkable depression in a variety of biological functions under long-term hypoxia, including metabolic rates, biomineralization activities, and the repression of reorganization of the cytoskeleton and cell metabolism. These findings provide a basis for elucidating the mechanisms used by marine bivalves to cope with long-term hypoxic stress.

Integrated transcriptomic and metabolomic analysis sheds new light on adaptation of Pinctada fucata martensii to short-term hypoxic stress.

Analyses of the transcriptome and metabolome were conducted to clarify alterations of key genes and metabolites in pearl oysters following exposure to short-term hypoxic treatment. We totally detected 209 DEGs between the control and hypoxia groups. Enrichment analysis indicated the enrichment of GO terms including "oxidation-reduction process", "ECM organization", "chaperone cofactor-dependent protein refolding", and "ECM-receptor interaction" KEGG pathway by the DEGs. In addition, between the two groups, a total of 28 SDMs were identified, which were implicated in 13 metabolic pathways, such as "phenylalanine metabolism", "D-amino acid metabolism", and "aminoacyl-tRNA biosynthesis". Results suggest that pearl oysters are exposed to oxidative stress and apoptosis under short-term hypoxia. Also, pearl oysters might adapt to short-term hypoxic treatment by increasing antioxidant activity, modulating immune and biomineralization activities, maintaining protein homeostasis, and reorganizing the cytoskeleton. The results of our study help unveil the mechanisms by which pearl oysters respond adaptively to short-term hypoxia.

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.