Combined effects of temperature and emersion-immersion cycles on metabolism and bioenergetics of the Pacific oyster Crassostrea (Magallana) gigas

Impacts of elevated temperature, decreased salinity and microfibers on the bioenergetics and oxidative stress in eastern oyster, Crassostrea virginica

Projected increases in temperature and decreases in salinity associated with global climate change will likely have detrimental impacts on eastern oyster, Crassostrea virginica, as these variables can influence physiological processes in these keystone species. We set out to determine how the interactive effects of temperature (20 °C or 27 °C) and/or salinity (27‰ or 17‰) impacted the energetic reserves, aerobic and anaerobic metabolism, and changes to oxidative stress or total antioxidant potential as a consequence of an altered environment over a 21-day exposure. Gill and adductor muscle were used to quantify changes in total glycogen and lipid content, Electron Transport System and Citrate Synthase activities, Malate Dehydrogenase activity, Protein Carbonyl formation, lipid peroxidation, and total antioxidant potential. A second exposure was performed to determine if these environmental factors influenced the ingestion of microfibers, which are now one of the leading forms of marine debris. Elevated temperature and the combination of elevated temperature and decreased salinity led to an overall decline in oyster mass, which was exacerbated by the presence of microfibers. Changes in metabolism and oxidative stress were largely influenced by time, but exposure to elevated temperature, decreased salinity, the combination of these stressors or exposure to microfibers had small impacts on oyster physiology and survival. Overall these studies demonstrate that oyster are fairly resilient to changes in salinity in short-term exposures, and elevations in temperature or temperature combined with salinity result in changes to the oyster energetic response, which can be further impacted by the presence of microfibers.

How water acidification influences the organism antioxidant capacity and gill structure of Mediterranean mussel (Mytilus galloprovincialis, Lamarck, 1819) at normoxia and hypoxia

The effect of water acidification in combination with normoxia or hypoxia on the antioxidant capacity and oxidative stress markers in gills and hemolymph of the Mediterranean mussel (Mytilus galloprovincialis), as well as on gill microstructure, has been evaluated through an in vivo experiment. Mussels were exposed to a low pH (7.3) under normal dissolved oxygen (DO) conditions (8 mg/L), and hypoxia (2 mg/L) for 8 days, and samples were collected on days 1, 3, 6, and 8 to evaluate dynamic changes of physiological responses. Cytoplasmic concentrations of reactive oxygen species (ROS) and levels of DNA damage were measured in hemocytes, while the activity of catalase (CAT) and superoxide dismutase (SOD) and histopathological changes were assessed in gills. The results revealed that while water acidification did not significantly affect the activity of SOD and CAT in gills under normoxic and hypoxic conditions, there was a trend towards suppression of CAT activity at the end of the experimental period (day 8). Similarly, we did not observe increased formation of ROS in hemocytes or changes in the levels of DNA damage during the experimental period. These results strongly suggest that the oxidative stress response system in mussels is relatively stable to experimental conditions of acidification and hypoxia. Experimental acidification under normoxia and hypoxia caused changes to the structure of the gills, leading to various histopathological alterations, including dilation, hemocyte infiltration into the hemal sinuses, intercellular edema, vacuolization of epithelial cells in gill filaments, lipofuscin accumulation, changes in the shape and adjacent gill filaments, hyperplasia, exfoliation of the epithelial layer, necrosis, swelling, and destruction of chitinous layers (chitinous rods). Most of these alterations were reversible, non-specific changes that represent a general inflammatory response and changes in the morphology of the gill filaments. The dynamics of histopathological alterations suggests an active adaptive response of gills to environmental stresses. Taken together, our data indicate that Mediterranean mussels have a relative tolerance to water acidification and hypoxia at tissue and cellular levels.

Combined effects of organic and mineral UV-filters on the lugworm Arenicola marina

Pollution from personal care products, such as UV-filters like avobenzone and nano-zinc oxide (nZnO), poses a growing threat to marine ecosystems. To better understand this hazard, especially for lesser-studied sediment-dwelling marine organisms, we investigated the physiological impacts of simultaneous exposure to nZnO and avobenzone on the lugworm Arenicola marina. Lugworms were exposed to nZnO, avobenzone, or their combination for three weeks. We assessed pollutant-induced metabolic changes by measuring key metabolic intermediates in the body wall and coelomic fluid, and oxidative stress by analyzing antioxidant levels and oxidative lesions in proteins and lipids of the body wall. Exposure to UV filters resulted in shifts in the concentrations of Krebs' cycle and urea cycle intermediates, as well as alterations in certain amino acids in the body wall and coelomic fluid of the lugworms. Pathway enrichment analyses revealed that nZnO induced more pronounced metabolic shifts compared to avobenzone or their combination. Exposure to avobenzone or nZnO alone prompted an increase in tissue antioxidant capacity, indicating a compensatory response to restore redox balance, which effectively prevented oxidative damage to proteins or lipids. However, co-exposure to nZnO and avobenzone suppressed superoxide dismutase and lead to accumulation of lipid peroxides and methionine sulfoxide, indicating oxidative stress and damage to lipids and proteins. Our findings highlight oxidative stress as a significant mechanism of toxicity for both nZnO and avobenzone, especially when combined, and underscores the importance of further investigating the fitness implications of oxidative stress induced by these common UV filters in benthic marine organisms.

Flexible Sensing Enabled Nondestructive Detection on Viability/Quality of Live Edible Oyster

Environmental and physiological fluctuations in the live oyster cold chain can result in reduced survival and quality. In this study, a flexible wireless sensor network (F-WSN) monitoring system combined with knowledge engineering was designed and developed to monitor environmental information and physiological fluctuations in the live oyster cold chain. Based on the Hazard Analysis and Critical Control Point (HACCP) plan to identify the critical control points (CCPs) in the live oyster cold chain, the F-WSN was utilized to conduct tracking and collection experiments in real scenarios from Yantai, Shandong Province, to Beijing. The knowledge model for shelf-life and quality prediction based on environmental information and physiological fluctuations was established, and the prediction accuracies of TVB-N, TVC, and pH were 96%, 85%, and 97%, respectively, and the prediction accuracy of viability was 96%. Relevant managers, workers, and experts were invited to participate in the efficiency and applicability assessment of the established system. The results indicated that combining F-WSN monitoring with knowledge-based HACCP modeling is an effective approach to improving the transparency of cold chain management, reducing quality and safety risks in the oyster industry, and promoting the sharing and reuse of HACCP knowledge in the oyster cold chain.