Pub Date : 2026-02-11DOI: 10.3389/fmars.2026.1765870
Jiaxin Li, Zhuohang Xin, Changchun Song, Liang Dong, Chi Zhang
Endogenous phosphorus (P) release and its complex biogeochemical transformation pose ongoing challenges for effective P management in estuarine ecosystems. However, the understanding of how these processes respond to runoff regulations remains rarely constrained. This study investigated the spatiotemporal distribution of P forms in bottom water and sediment of the Liao River Estuary under anthropogenic runoff regulations characterized by low runoff in summer and normal runoff in winter. The sediment P adsorption capacity and release potential were studied through adsorption kinetics and thermodynamic experiments. Soluble reactive P (SRP) and total dissolved P (TDP) concentrations in bottom water were low in summer but increased markedly in winter (p<0.01). The average sediment total P (TP) concentrations were 495.26 mg/kg in summer and 399.62 mg/kg in winter, with higher TP levels mainly observed in the nearshore muddy areas, likely attributable to the high proportion of fine particles. Equilibrium P concentration generally exceeded the SRP concentration in bottom water under both conditions, indicating that the sediment served as a P source. The sediment P eutrophication risk index (ERI) further showed that release risk was predominantly moderate in summer, whereas it was low in winter. Both PLS-PM and correlation analysis showed that the concentrations of Fe, Al, organic matter, and the proportion of fine particles served as key determinants influencing the content of aluminum-bound P (NaOH-rP), organic P (NaOH-nrP), and calcium-bound P (HCl-P). Furthermore, elevated SRP levels combined with reduced salt in winter likely constrain P accumulation in the sediment. This study offers novel insight into the migration and transformation of P in the estuarine environment under anthropogenic runoff regulations.
{"title":"Unravelling phosphorus adsorption characteristics and release potential in estuarine sediment under runoff regulation","authors":"Jiaxin Li, Zhuohang Xin, Changchun Song, Liang Dong, Chi Zhang","doi":"10.3389/fmars.2026.1765870","DOIUrl":"https://doi.org/10.3389/fmars.2026.1765870","url":null,"abstract":"Endogenous phosphorus (P) release and its complex biogeochemical transformation pose ongoing challenges for effective P management in estuarine ecosystems. However, the understanding of how these processes respond to runoff regulations remains rarely constrained. This study investigated the spatiotemporal distribution of P forms in bottom water and sediment of the Liao River Estuary under anthropogenic runoff regulations characterized by low runoff in summer and normal runoff in winter. The sediment P adsorption capacity and release potential were studied through adsorption kinetics and thermodynamic experiments. Soluble reactive P (SRP) and total dissolved P (TDP) concentrations in bottom water were low in summer but increased markedly in winter (p&lt;0.01). The average sediment total P (TP) concentrations were 495.26 mg/kg in summer and 399.62 mg/kg in winter, with higher TP levels mainly observed in the nearshore muddy areas, likely attributable to the high proportion of fine particles. Equilibrium P concentration generally exceeded the SRP concentration in bottom water under both conditions, indicating that the sediment served as a P source. The sediment P eutrophication risk index (ERI) further showed that release risk was predominantly moderate in summer, whereas it was low in winter. Both PLS-PM and correlation analysis showed that the concentrations of Fe, Al, organic matter, and the proportion of fine particles served as key determinants influencing the content of aluminum-bound P (NaOH-rP), organic P (NaOH-nrP), and calcium-bound P (HCl-P). Furthermore, elevated SRP levels combined with reduced salt in winter likely constrain P accumulation in the sediment. This study offers novel insight into the migration and transformation of P in the estuarine environment under anthropogenic runoff regulations.","PeriodicalId":12479,"journal":{"name":"Frontiers in Marine Science","volume":"115 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146153511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-11DOI: 10.3389/fmars.2026.1774354
Gabriela Gonçalves, Rafaela A. Santos, Isabel M. Cerezo, Tomás Gabriel, José Dias, Rui Magalhães, Pedro Pousão-Ferreira, Paula Enes, Carolina Tafalla, Aires Oliva-Teles, Ana Couto, Patricia Díaz-Rosales, Cláudia R. Serra
Despite the availability of commercial vaccines against several pathogens, infectious diseases continue to cause substantial economic losses in aquaculture. Current vaccine development focuses on exploring antigen delivery systems that enable efficient needle-free, mass vaccination. Bacterial spores offer a promising platform for oral vaccine delivery, as they are highly resistant structures that can act as adjuvants and antigen carriers. This technology has been explored in recent years, mostly using spores from laboratory strains, for which a variety of genetic tools have been optimized. The use of spores of autochthonous probiotic strains for displaying antigens remains to be further explored. In this study, we engineered two fish-gut Bacillus subtilis strains (FI314 and FI442) with probiotic potential to display the immunogenic proteins OmpK or TolC of Vibrio spp. Their immunomodulatory effect was evaluated using in vitro , ex vivo , and in vivo approaches. In RTgutGC cells, both FI314 and FI314-TolC spores induced an up-regulation of innate immune markers, including il1b and il8 , while FI314 spores down-regulated casp3a2 expression. These effects were not observed with the probiotic FI442. In European seabass gut explants, FI314-TolC spores induced the expression of il10 , while all spores induced the upregulation of ifng after bacterial challenge with V. anguillarum . In vivo , however, feeding European seabass with diets containing FI314, FI314-OmpK, or FI314-TolC spores for 30 days did not elicit a robust adaptive immune response, as indicated by the lack of significant modulation of immune-related genes and unchanged serum IgM levels. RNA-seq analysis of the distal intestine showed that FI314 spores induced a down-regulation of cell proliferation pathways. while OmpK-carrying spores affected innate immunity pathways. The results of this study indicate that the immunomodulatory effects of autochthonous probiotics are strain dependent. FI314 antigen-displaying spores were insufficient to induce an effective adaptive immunity, under the conditions tested. This study emphasizes the importance of optimizing bacterial strain selection, antigen choice, and immunization regimen when designing oral spore-based vaccines for fish.
{"title":"Antigen-displaying probiotic Bacillus subtilis spores induce subtle, strain-dependent immunomodulation in fish","authors":"Gabriela Gonçalves, Rafaela A. Santos, Isabel M. Cerezo, Tomás Gabriel, José Dias, Rui Magalhães, Pedro Pousão-Ferreira, Paula Enes, Carolina Tafalla, Aires Oliva-Teles, Ana Couto, Patricia Díaz-Rosales, Cláudia R. Serra","doi":"10.3389/fmars.2026.1774354","DOIUrl":"https://doi.org/10.3389/fmars.2026.1774354","url":null,"abstract":"Despite the availability of commercial vaccines against several pathogens, infectious diseases continue to cause substantial economic losses in aquaculture. Current vaccine development focuses on exploring antigen delivery systems that enable efficient needle-free, mass vaccination. Bacterial spores offer a promising platform for oral vaccine delivery, as they are highly resistant structures that can act as adjuvants and antigen carriers. This technology has been explored in recent years, mostly using spores from laboratory strains, for which a variety of genetic tools have been optimized. The use of spores of autochthonous probiotic strains for displaying antigens remains to be further explored. In this study, we engineered two fish-gut <jats:italic>Bacillus subtilis</jats:italic> strains (FI314 and FI442) with probiotic potential to display the immunogenic proteins OmpK or TolC of <jats:italic>Vibrio</jats:italic> spp. Their immunomodulatory effect was evaluated using <jats:italic>in vitro</jats:italic> , <jats:italic>ex vivo</jats:italic> , and <jats:italic>in vivo</jats:italic> approaches. In RTgutGC cells, both FI314 and FI314-TolC spores induced an up-regulation of innate immune markers, including <jats:italic>il1b</jats:italic> and <jats:italic>il8</jats:italic> , while FI314 spores down-regulated <jats:italic>casp3a2</jats:italic> expression. These effects were not observed with the probiotic FI442. In European seabass gut explants, FI314-TolC spores induced the expression of <jats:italic>il10</jats:italic> , while all spores induced the upregulation of <jats:italic>ifng</jats:italic> after bacterial challenge with <jats:italic>V. anguillarum</jats:italic> . <jats:italic>In vivo</jats:italic> , however, feeding European seabass with diets containing FI314, FI314-OmpK, or FI314-TolC spores for 30 days did not elicit a robust adaptive immune response, as indicated by the lack of significant modulation of immune-related genes and unchanged serum IgM levels. RNA-seq analysis of the distal intestine showed that FI314 spores induced a down-regulation of cell proliferation pathways. while OmpK-carrying spores affected innate immunity pathways. The results of this study indicate that the immunomodulatory effects of autochthonous probiotics are strain dependent. FI314 antigen-displaying spores were insufficient to induce an effective adaptive immunity, under the conditions tested. This study emphasizes the importance of optimizing bacterial strain selection, antigen choice, and immunization regimen when designing oral spore-based vaccines for fish.","PeriodicalId":12479,"journal":{"name":"Frontiers in Marine Science","volume":"242 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146153436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-11DOI: 10.3389/fmars.2025.1592546
Isabelle Mirouze, Elisabeth Rémy, Giovanni Ruggiero, Mathieu Hamon, Jean-Michel Lellouche, Gérald Dibarboure, Yannice Faugère
In recent years, the accuracy of ocean forecasts has significantly improved thanks to spatial altimetry. However, despite their importance, forecasting accurate currents is still a challenge. Therefore, satellite missions are proposed to provide measurements of surface velocity on a global coverage. The Ocean DYnamics and Surface Exchange with the Atmosphere (ODYSEA) mission of the National Aeronautics and Space Administration (NASA) and Centre National d’Etudes Spatiales (CNES) is currently competing for selection in the Earth System Explorers program. As part of the preliminary studies for ODYSEA, we have carried out Observing System Simulation Experiments (OSSEs) to assess the impact of assimilating these prospective observations in terms of Root Mean Square differences of the model state variables to a reference run. We focus on disentangling the impact of the ODYSEA observations from the impact of the observations provided by altimetry, on large scale, and checking the complementarity of these networks to avoid redundant information. We show that zonal velocity out of the Equator, sea surface height and surface salinity are mainly constrained by altimetry. Conversely, the meridional velocity is mainly constrained by velocity observations. Moreover, these latter observations help better prescribing both components of velocity at the Equator as well as the sea surface temperature in the Eastern Pacific. They also tend to significantly improve surface salinity in some regions where freshwater input occurs. Altimetry and surface velocity observations are complementary, and when they are assimilated together, all the model state variables are improved in all regions compared to assimilating altimetry only.
{"title":"On the complementarity of satellite surface velocity and altimetry observation networks in the Mercator ocean analysis and forecasting system: first insights","authors":"Isabelle Mirouze, Elisabeth Rémy, Giovanni Ruggiero, Mathieu Hamon, Jean-Michel Lellouche, Gérald Dibarboure, Yannice Faugère","doi":"10.3389/fmars.2025.1592546","DOIUrl":"https://doi.org/10.3389/fmars.2025.1592546","url":null,"abstract":"In recent years, the accuracy of ocean forecasts has significantly improved thanks to spatial altimetry. However, despite their importance, forecasting accurate currents is still a challenge. Therefore, satellite missions are proposed to provide measurements of surface velocity on a global coverage. The Ocean DYnamics and Surface Exchange with the Atmosphere (ODYSEA) mission of the National Aeronautics and Space Administration (NASA) and Centre National d’Etudes Spatiales (CNES) is currently competing for selection in the Earth System Explorers program. As part of the preliminary studies for ODYSEA, we have carried out Observing System Simulation Experiments (OSSEs) to assess the impact of assimilating these prospective observations in terms of Root Mean Square differences of the model state variables to a reference run. We focus on disentangling the impact of the ODYSEA observations from the impact of the observations provided by altimetry, on large scale, and checking the complementarity of these networks to avoid redundant information. We show that zonal velocity out of the Equator, sea surface height and surface salinity are mainly constrained by altimetry. Conversely, the meridional velocity is mainly constrained by velocity observations. Moreover, these latter observations help better prescribing both components of velocity at the Equator as well as the sea surface temperature in the Eastern Pacific. They also tend to significantly improve surface salinity in some regions where freshwater input occurs. Altimetry and surface velocity observations are complementary, and when they are assimilated together, all the model state variables are improved in all regions compared to assimilating altimetry only.","PeriodicalId":12479,"journal":{"name":"Frontiers in Marine Science","volume":"32 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146153435","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-11DOI: 10.3389/fmars.2026.1728376
Hoon Mo Koo, Inho Yang, Jinsoon Park, Yong-Woo Lee, Yong Hwa Oh
Physicochemical and biological parameters (temperature, salinity, pH, dissolved inorganic nutrients, and chlorophyll-a) were analyzed to evaluate the effects of precipitation variability associated with climate change on the water quality in the Nakdong River Estuary, South Korea. Multi-year monitoring data (2016–2021) were collected seasonally (February, May, August, and November) throughout the study period. Extreme rainfall events caused pronounced estuarine freshening (salinity < 1) and sharply enhanced riverine nutrient fluxes, with wet-to-dry season increases of 4–70 times for dissolved inorganic nitrogen, 4–36 times for phosphorus, and 9–740 times for silicate, showing strong positive correlations with precipitation (r² = 0.76–0.82, p < 0.001). Time-series and self-organizing map classifications revealed estuarine that the water quality was strongly controlled by seasonal precipitation and river discharge, whereas offshore waters exhibited weaker but detectable responses. Notably, extreme rainfall events altered the chlorophyll-a distribution, suppressing phytoplankton accumulation in the estuary because of dilution and flushing, while enhancing chlorophyll-a concentrations in offshore waters through nutrient-enriched river plume dispersion. These results demonstrated that extreme rainfall driven by climate change can enhance the terrestrial nutrient input into coastal waters, thereby increasing the potential for eutrophication and harmful algal blooms.
{"title":"Impacts of precipitation variability on water quality in the Nakdong River Estuary: multi-year (2016–2021) data analysis","authors":"Hoon Mo Koo, Inho Yang, Jinsoon Park, Yong-Woo Lee, Yong Hwa Oh","doi":"10.3389/fmars.2026.1728376","DOIUrl":"https://doi.org/10.3389/fmars.2026.1728376","url":null,"abstract":"Physicochemical and biological parameters (temperature, salinity, pH, dissolved inorganic nutrients, and chlorophyll-a) were analyzed to evaluate the effects of precipitation variability associated with climate change on the water quality in the Nakdong River Estuary, South Korea. Multi-year monitoring data (2016–2021) were collected seasonally (February, May, August, and November) throughout the study period. Extreme rainfall events caused pronounced estuarine freshening (salinity &lt; 1) and sharply enhanced riverine nutrient fluxes, with wet-to-dry season increases of 4–70 times for dissolved inorganic nitrogen, 4–36 times for phosphorus, and 9–740 times for silicate, showing strong positive correlations with precipitation (r² = 0.76–0.82, p &lt; 0.001). Time-series and self-organizing map classifications revealed estuarine that the water quality was strongly controlled by seasonal precipitation and river discharge, whereas offshore waters exhibited weaker but detectable responses. Notably, extreme rainfall events altered the chlorophyll-a distribution, suppressing phytoplankton accumulation in the estuary because of dilution and flushing, while enhancing chlorophyll-a concentrations in offshore waters through nutrient-enriched river plume dispersion. These results demonstrated that extreme rainfall driven by climate change can enhance the terrestrial nutrient input into coastal waters, thereby increasing the potential for eutrophication and harmful algal blooms.","PeriodicalId":12479,"journal":{"name":"Frontiers in Marine Science","volume":"6 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146153434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-10DOI: 10.3389/fmars.2026.1782614
JinYang Zhang, Yang Huang, JiaYu Yang, KaiYu Deng, HaiXiang Li, DunQiu Wang, YuFeng Xu, Kun Dong
Rivers serve as critical conduits for transporting pollutants and nutrients to coastal zones, directly influencing coastal ecosystem functions and marine environmental health. Understanding spatiotemporal variations and driving mechanisms of river water quality is therefore critical for effective watershed management and coastal zone protection. This study analyzed water quality data from three monitoring sections (Suqiao, Xialiang Village, and Longxi) along the Luoqing River in Guilin, China, collected during January 2023–March 2025. Seven conventional parameters—water temperature, pH, dissolved oxygen (DO), permanganate index (COD Mn ), total nitrogen (TN), total phosphorus (TP), and ammonia nitrogen (NH 3 -N)—were evaluated using Spearman correlation analysis, principal component analysis (PCA), and machine learning models (CatBoost, Random Forest, and XGBoost). The results showed pronounced monthly variability but relatively stable interannual patterns, indicating dominant control by seasonal hydrological and biogeochemical processes. Spatial differences were evident, with downstream sections exhibiting higher pollution levels and more complex parameter interactions, reflecting intensified anthropogenic influences. PCA extracted two principal components explaining over 70% of the total variance: PC1 associated with nutrient and organic pollution (TN, TP, NH 3 -N, COD Mn ) and PC2 representing physicochemical conditions (pH and DO). A Composite Pollution Index (CPI) was constructed based on NH 3 -N, TN, TP and COD Mn to characterize overall pollution levels. Machine learning models achieved high predictive performance for the CPI (R 2 ≈ 0.994). The shapley Additive Explanations (SHAP) and partial dependence analyses identified TN as the primary controlling factor, with synergistic enhancement between TN and COD Mn under high nitrogen conditions. Overall, Luoqing River water quality is characterized by a nitrogen-centered pollution structure, providing a scientific basis for targeted watershed management and coastal ecosystem protection.
{"title":"Machine learning-based correlation analysis of conventional water quality parameters and composite pollution index in the Luoqing river of the South China Sea Coastal Zone","authors":"JinYang Zhang, Yang Huang, JiaYu Yang, KaiYu Deng, HaiXiang Li, DunQiu Wang, YuFeng Xu, Kun Dong","doi":"10.3389/fmars.2026.1782614","DOIUrl":"https://doi.org/10.3389/fmars.2026.1782614","url":null,"abstract":"Rivers serve as critical conduits for transporting pollutants and nutrients to coastal zones, directly influencing coastal ecosystem functions and marine environmental health. Understanding spatiotemporal variations and driving mechanisms of river water quality is therefore critical for effective watershed management and coastal zone protection. This study analyzed water quality data from three monitoring sections (Suqiao, Xialiang Village, and Longxi) along the Luoqing River in Guilin, China, collected during January 2023–March 2025. Seven conventional parameters—water temperature, pH, dissolved oxygen (DO), permanganate index (COD <jats:sub>Mn</jats:sub> ), total nitrogen (TN), total phosphorus (TP), and ammonia nitrogen (NH <jats:sub>3</jats:sub> -N)—were evaluated using Spearman correlation analysis, principal component analysis (PCA), and machine learning models (CatBoost, Random Forest, and XGBoost). The results showed pronounced monthly variability but relatively stable interannual patterns, indicating dominant control by seasonal hydrological and biogeochemical processes. Spatial differences were evident, with downstream sections exhibiting higher pollution levels and more complex parameter interactions, reflecting intensified anthropogenic influences. PCA extracted two principal components explaining over 70% of the total variance: PC1 associated with nutrient and organic pollution (TN, TP, NH <jats:sub>3</jats:sub> -N, COD <jats:sub>Mn</jats:sub> ) and PC2 representing physicochemical conditions (pH and DO). A Composite Pollution Index (CPI) was constructed based on NH <jats:sub>3</jats:sub> -N, TN, TP and COD <jats:sub>Mn</jats:sub> to characterize overall pollution levels. Machine learning models achieved high predictive performance for the CPI (R <jats:sup>2</jats:sup> ≈ 0.994). The shapley Additive Explanations (SHAP) and partial dependence analyses identified TN as the primary controlling factor, with synergistic enhancement between TN and COD <jats:sub>Mn</jats:sub> under high nitrogen conditions. Overall, Luoqing River water quality is characterized by a nitrogen-centered pollution structure, providing a scientific basis for targeted watershed management and coastal ecosystem protection.","PeriodicalId":12479,"journal":{"name":"Frontiers in Marine Science","volume":"14 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146153440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-10DOI: 10.3389/fmars.2026.1744499
Xuancheng Liu, Junhua Huang, Zhengyi Fu, Jie Chang, Zhenhua Ma
This study aimed to examine the physiological responses of juvenile yellowfin tuna ( Thunnus albacares ) to short-term cold stress by comparing oxidative stress, metabolic regulation, and immune-related transcriptional responses in red and white muscles under two low-temperature conditions (24 °C and 18 °C) and a control temperature (30 °C). Juvenile tuna were exposed to these temperature conditions for 36 h, and muscle samples were collected at multiple time points to assess enzyme activities, biochemical indicators, and gene expression. Antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px), exhibited a biphasic response, characterized by an initial upregulation at 18 °C after 12 h followed by a decline under prolonged cold exposure. Elevated malondialdehyde (MDA) levels in the red muscle at 24 h indicated enhanced lipid peroxidation and oxidative stress. At 36 h, increased activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and acid phosphatase (ACP) in the red muscle reflected altered metabolic status and enhanced involvement of amino acid-related processes, whereas reduced lactate dehydrogenase (LDH) activity suggested suppression of anaerobic metabolic capacity under prolonged cold stress. Gene expression analysis revealed tissue-specific responses: the red muscle showed a pronounced and sustained induction of hspa1b and acadm , while the white muscle exhibited a faster but less persistent transcriptional response. In addition, the immune-related gene irf3 was downregulated in the red muscle but transiently upregulated in the white muscle. Overall, red muscle displayed slower yet more sustained regulation, whereas white muscle responded more rapidly but exhibited greater sensitivity to cold-induced biochemical perturbations. These findings highlight time- and tissue-specific mechanisms underlying tuna muscle responses to cold stress and provide insights relevant to adaptive management strategies for pelagic fish under climate change scenarios.
{"title":"Short-term cold stress effects on antioxidant, metabolic, and immune responses in the red and white muscles of juvenile yellowfin tuna (Thunnus albacares)","authors":"Xuancheng Liu, Junhua Huang, Zhengyi Fu, Jie Chang, Zhenhua Ma","doi":"10.3389/fmars.2026.1744499","DOIUrl":"https://doi.org/10.3389/fmars.2026.1744499","url":null,"abstract":"This study aimed to examine the physiological responses of juvenile yellowfin tuna ( <jats:italic>Thunnus albacares</jats:italic> ) to short-term cold stress by comparing oxidative stress, metabolic regulation, and immune-related transcriptional responses in red and white muscles under two low-temperature conditions (24 °C and 18 °C) and a control temperature (30 °C). Juvenile tuna were exposed to these temperature conditions for 36 h, and muscle samples were collected at multiple time points to assess enzyme activities, biochemical indicators, and gene expression. Antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px), exhibited a biphasic response, characterized by an initial upregulation at 18 °C after 12 h followed by a decline under prolonged cold exposure. Elevated malondialdehyde (MDA) levels in the red muscle at 24 h indicated enhanced lipid peroxidation and oxidative stress. At 36 h, increased activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and acid phosphatase (ACP) in the red muscle reflected altered metabolic status and enhanced involvement of amino acid-related processes, whereas reduced lactate dehydrogenase (LDH) activity suggested suppression of anaerobic metabolic capacity under prolonged cold stress. Gene expression analysis revealed tissue-specific responses: the red muscle showed a pronounced and sustained induction of <jats:italic>hspa1b</jats:italic> and <jats:italic>acadm</jats:italic> , while the white muscle exhibited a faster but less persistent transcriptional response. In addition, the immune-related gene <jats:italic>irf3</jats:italic> was downregulated in the red muscle but transiently upregulated in the white muscle. Overall, red muscle displayed slower yet more sustained regulation, whereas white muscle responded more rapidly but exhibited greater sensitivity to cold-induced biochemical perturbations. These findings highlight time- and tissue-specific mechanisms underlying tuna muscle responses to cold stress and provide insights relevant to adaptive management strategies for pelagic fish under climate change scenarios.","PeriodicalId":12479,"journal":{"name":"Frontiers in Marine Science","volume":"59 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146153574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-10DOI: 10.3389/fmars.2026.1771231
Shuwen Wang, Zikang Zhang, Yang Shi, Xiujun Sun, Ying Zhou, Yihang Shu, Fan Yang, Hongzhe Zhu, Kunde Yang
Formed by humidity stratification in the marine atmospheric boundary layer, evaporation ducts serve as critical natural channels for maritime over-the-horizon (OTH) wireless communication. Their unique structure effectively confines electromagnetic (EM) wave propagation, substantially enhancing the link stability and transmission quality of long-range maritime communication while exerting notable impact on OTH EM wave propagation. Tropical cyclones profoundly alter near-surface meteorological conditions and disrupt the distribution uniformity of evaporation ducts, directly inducing fluctuations in communication link path loss (PL), intensified signal attenuation, and even short-term outages, severely impairing maritime broadband communication. However, direct and mobile observations of evaporation ducts within typhoon interiors remain limited. This study investigated the evolution of evaporation duct height (EDH) during Typhoon Koinu (202314) through analysis of 108 hours of continuous observations by three clustered wave gliders. One glider traversed the typhoon eye, while the other two monitored regions of high wind speed (WS). The maximum recorded WS reached 26.5 m/s, accompanied by EDH of 11.9 m, whereas within the eye region, WS was 4.36 m/s with EDH of 5.7 m. The presence of the typhoon’s eye caused a 6.2-m reduction in EDH. Relative humidity (RH) fluctuated from 70% to 95% before the typhoon’s arrival and remained at around 90% during the typhoon’s passage. Correlation analysis indicated that RH was the dominant factor influencing EDH before the typhoon’s arrival, showing negative correlation (Spearman correlation coefficient: −0.83). In contrast, WS was the main driver of EDH variation during the typhoon’s passage, exhibiting strong positive correlation (Spearman correlation coefficient: 0.82). Sensitivity analysis confirmed that the inhibitory effect of elevated RH outweighed the contribution of high WS to EDH enhancement, leading to lower EDH values during the passage of the typhoon than in the pre-typhoon period. Analysis of the spatial distribution of EM wave propagation indicated that the low EDH induced by low WS in the typhoon’s eye caused PL that was 24 dB greater than under high-WS scenarios; overall, the presence of the typhoon’s eye caused greater PL.
{"title":"Continuous observation of evaporation ducts in Super Typhoon Koinu (202314) using clustered wave gliders: mechanisms and maritime communication implications","authors":"Shuwen Wang, Zikang Zhang, Yang Shi, Xiujun Sun, Ying Zhou, Yihang Shu, Fan Yang, Hongzhe Zhu, Kunde Yang","doi":"10.3389/fmars.2026.1771231","DOIUrl":"https://doi.org/10.3389/fmars.2026.1771231","url":null,"abstract":"Formed by humidity stratification in the marine atmospheric boundary layer, evaporation ducts serve as critical natural channels for maritime over-the-horizon (OTH) wireless communication. Their unique structure effectively confines electromagnetic (EM) wave propagation, substantially enhancing the link stability and transmission quality of long-range maritime communication while exerting notable impact on OTH EM wave propagation. Tropical cyclones profoundly alter near-surface meteorological conditions and disrupt the distribution uniformity of evaporation ducts, directly inducing fluctuations in communication link path loss (PL), intensified signal attenuation, and even short-term outages, severely impairing maritime broadband communication. However, direct and mobile observations of evaporation ducts within typhoon interiors remain limited. This study investigated the evolution of evaporation duct height (EDH) during Typhoon Koinu (202314) through analysis of 108 hours of continuous observations by three clustered wave gliders. One glider traversed the typhoon eye, while the other two monitored regions of high wind speed (WS). The maximum recorded WS reached 26.5 m/s, accompanied by EDH of 11.9 m, whereas within the eye region, WS was 4.36 m/s with EDH of 5.7 m. The presence of the typhoon’s eye caused a 6.2-m reduction in EDH. Relative humidity (RH) fluctuated from 70% to 95% before the typhoon’s arrival and remained at around 90% during the typhoon’s passage. Correlation analysis indicated that RH was the dominant factor influencing EDH before the typhoon’s arrival, showing negative correlation (Spearman correlation coefficient: −0.83). In contrast, WS was the main driver of EDH variation during the typhoon’s passage, exhibiting strong positive correlation (Spearman correlation coefficient: 0.82). Sensitivity analysis confirmed that the inhibitory effect of elevated RH outweighed the contribution of high WS to EDH enhancement, leading to lower EDH values during the passage of the typhoon than in the pre-typhoon period. Analysis of the spatial distribution of EM wave propagation indicated that the low EDH induced by low WS in the typhoon’s eye caused PL that was 24 dB greater than under high-WS scenarios; overall, the presence of the typhoon’s eye caused greater PL.","PeriodicalId":12479,"journal":{"name":"Frontiers in Marine Science","volume":"317 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146153438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-10DOI: 10.3389/fmars.2026.1737002
Belén Martín Míguez, Emma Heslop, Narissa Bax, Lisandro Benedetti-Cecchi, Gabrielle Canonico, Kim Currie, Karen Evans, Albert S. Fischer, Véronique Garçon, Maria Hood, Johannes Karstensen, Ana Lara-López, David Legler, Frank E. Muller-Karger, Balakrishnan Nair Thayannur Mullachery, Lina Mtwana Nordlund, Artur P. Palacz, Joanna Post, Samantha E. Simmons, Sabrina Speich, Laura Stukonytė, Adrienne J. Sutton, Toste Tanhua, Maciej Telszewski, Karina von Schuckmann, Anya M. Waite, Weidong Yu
The need for ocean information has never been greater. From climate change to food security and extreme events, we need to understand the role of the ocean and better predict change and impact. This is only possible with the sustained collection of a key set of ocean observations. The Global Ocean Observing System (GOOS) coordinates international efforts to collect these Essential Ocean Variables (EOVs), which span physics, biogeochemistry, biology and ecosystem realms. Guided by three expert panels, these EOVs are used to define the needs and design of a sustained, fit for purpose global ocean observing system, aimed at maximizing investments in observing infrastructure. As the GOOS EOVs are increasingly used, it has become important to discuss and refine the understanding of this framework, to ensure that the right balance is struck between their essential nature and the need to expand to new domains and integrate with key global policies. In this paper we provide a description of the EOV framework, discuss some of the challenges in implementing it, and identify a set of recommendations for GOOS and the ocean observing community to take forward. These recommendations include increasing the transparency of the EOV adoption process, and the need to periodically assess the EOVs in consultation with observing communities and with the entities managing other global essential variable frameworks in cross cutting realms such as climate and biodiversity. This will contribute to building a useful and responsive global ocean observing system that delivers the observations required to meet societal needs.
{"title":"GOOS Essential Ocean Variables: the backbone of a sustained and evolving global ocean observing system","authors":"Belén Martín Míguez, Emma Heslop, Narissa Bax, Lisandro Benedetti-Cecchi, Gabrielle Canonico, Kim Currie, Karen Evans, Albert S. Fischer, Véronique Garçon, Maria Hood, Johannes Karstensen, Ana Lara-López, David Legler, Frank E. Muller-Karger, Balakrishnan Nair Thayannur Mullachery, Lina Mtwana Nordlund, Artur P. Palacz, Joanna Post, Samantha E. Simmons, Sabrina Speich, Laura Stukonytė, Adrienne J. Sutton, Toste Tanhua, Maciej Telszewski, Karina von Schuckmann, Anya M. Waite, Weidong Yu","doi":"10.3389/fmars.2026.1737002","DOIUrl":"https://doi.org/10.3389/fmars.2026.1737002","url":null,"abstract":"The need for ocean information has never been greater. From climate change to food security and extreme events, we need to understand the role of the ocean and better predict change and impact. This is only possible with the sustained collection of a key set of ocean observations. The Global Ocean Observing System (GOOS) coordinates international efforts to collect these Essential Ocean Variables (EOVs), which span physics, biogeochemistry, biology and ecosystem realms. Guided by three expert panels, these EOVs are used to define the needs and design of a sustained, fit for purpose global ocean observing system, aimed at maximizing investments in observing infrastructure. As the GOOS EOVs are increasingly used, it has become important to discuss and refine the understanding of this framework, to ensure that the right balance is struck between their essential nature and the need to expand to new domains and integrate with key global policies. In this paper we provide a description of the EOV framework, discuss some of the challenges in implementing it, and identify a set of recommendations for GOOS and the ocean observing community to take forward. These recommendations include increasing the transparency of the EOV adoption process, and the need to periodically assess the EOVs in consultation with observing communities and with the entities managing other global essential variable frameworks in cross cutting realms such as climate and biodiversity. This will contribute to building a useful and responsive global ocean observing system that delivers the observations required to meet societal needs.","PeriodicalId":12479,"journal":{"name":"Frontiers in Marine Science","volume":"13 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146153437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-09DOI: 10.3389/fmars.2026.1761703
Kristina M. Barclay, Helen J. Gurney-Smith, Mohamed Ahmed, James R. Christian, Frédéric Cyr, Patrick J. Duke, Brent G. T. Else, Iria Gimenez, Martine Lizotte, M. Catherine Reader, Myron Roth, Krysten Rutherford, Michel Starr, Nadja S. Steiner, Jessie Turner, David L. VanderZwaag, Wiley Evans
Ocean acidification (OA) generally receives far less consideration than other climate stressors and related hazards, such as global warming and extreme weather events. Canada is uniquely vulnerable to OA given its extensive coastal oceans, the oceanographic processes in its three basins, accelerated warming and sea-ice melt, and extensive coastal communities and maritime economic sectors. Canada’s coastline is also home to extensive and diverse First Nations peoples with distinct histories, rights, title, laws, governance and whose traditions and cultures are extrinsically linked to the sea. However, there are currently very limited pathways to support OA action, mitigation, and/or adaptation in Canada, particularly at the policy level. Here, we present a first synthesis of the current state of OA knowledge across Canada's Pacific, Arctic, and Atlantic regions, including monitoring, modelling, biological responses, socioeconomic and policy perspectives, and examples of existing OA actions and efforts at local and provincial levels. We also suggest a step-wise pathway for actions to enhance the coordinated filling of OA knowledge gaps and integration of OA knowledge into decision-making frameworks. The goals of these recommendations are to improve our ability to respond to OA in Canada, and minimize risks to coastal marine environments and ecosystems, vulnerable sectors, and communities.
{"title":"Ocean acidification in Canada: the current state of knowledge and pathways for action","authors":"Kristina M. Barclay, Helen J. Gurney-Smith, Mohamed Ahmed, James R. Christian, Frédéric Cyr, Patrick J. Duke, Brent G. T. Else, Iria Gimenez, Martine Lizotte, M. Catherine Reader, Myron Roth, Krysten Rutherford, Michel Starr, Nadja S. Steiner, Jessie Turner, David L. VanderZwaag, Wiley Evans","doi":"10.3389/fmars.2026.1761703","DOIUrl":"https://doi.org/10.3389/fmars.2026.1761703","url":null,"abstract":"Ocean acidification (OA) generally receives far less consideration than other climate stressors and related hazards, such as global warming and extreme weather events. Canada is uniquely vulnerable to OA given its extensive coastal oceans, the oceanographic processes in its three basins, accelerated warming and sea-ice melt, and extensive coastal communities and maritime economic sectors. Canada’s coastline is also home to extensive and diverse First Nations peoples with distinct histories, rights, title, laws, governance and whose traditions and cultures are extrinsically linked to the sea. However, there are currently very limited pathways to support OA action, mitigation, and/or adaptation in Canada, particularly at the policy level. Here, we present a first synthesis of the current state of OA knowledge across Canada's Pacific, Arctic, and Atlantic regions, including monitoring, modelling, biological responses, socioeconomic and policy perspectives, and examples of existing OA actions and efforts at local and provincial levels. We also suggest a step-wise pathway for actions to enhance the coordinated filling of OA knowledge gaps and integration of OA knowledge into decision-making frameworks. The goals of these recommendations are to improve our ability to respond to OA in Canada, and minimize risks to coastal marine environments and ecosystems, vulnerable sectors, and communities.","PeriodicalId":12479,"journal":{"name":"Frontiers in Marine Science","volume":"35 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-09DOI: 10.3389/fmars.2026.1733628
Min Wang, Shijun Zhang, M. Jahanzeb Butt, Khadija Zulfiqar
Recently, international judicial forums have issued landmark advisory opinions on the subject of the ocean–climate nexus. The opinions are based on the recognition of the interconnection between the United Nations Framework Convention on Climate Change (UNFCCC) and the United Nations Convention on the Law of the Sea (UNCLOS). All judicial forums stated that Small Island Developing States (SIDS) are a distinct focus due to their disproportionate vulnerability to climate change, as reported by the Intergovernmental Panel on Climate Change (IPCC). According to the opinions, SIDS could become uninhabitable in the coming years, necessitating urgent global climate action. The United Nations (UN) has acknowledged the unique challenges of SIDS through various resolutions, which emphasise the need for climate justice and adherence to the 1.5 C climate target. Sustainable Development Goal 14 (SDG 14) brought attention to the direct impacts of climate change on oceans and the issues faced by SIDS. This paper reviews the historical and legal developments necessary for the sustainable development of SIDS, emphasising the nexus between climate change, ocean governance, and human rights. It highlights the potential for further advocacy and the interconnected nature of SDG 14 with judicial opinions.
{"title":"Advisory opinion of the ITLOS on climate change and International Law on the Request of Small Island Developing States (SIDS): a Sustainable Development Goal - 14 (SDG 14) perspective","authors":"Min Wang, Shijun Zhang, M. Jahanzeb Butt, Khadija Zulfiqar","doi":"10.3389/fmars.2026.1733628","DOIUrl":"https://doi.org/10.3389/fmars.2026.1733628","url":null,"abstract":"Recently, international judicial forums have issued landmark advisory opinions on the subject of the ocean–climate nexus. The opinions are based on the recognition of the interconnection between the United Nations Framework Convention on Climate Change (UNFCCC) and the United Nations Convention on the Law of the Sea (UNCLOS). All judicial forums stated that Small Island Developing States (SIDS) are a distinct focus due to their disproportionate vulnerability to climate change, as reported by the Intergovernmental Panel on Climate Change (IPCC). According to the opinions, SIDS could become uninhabitable in the coming years, necessitating urgent global climate action. The United Nations (UN) has acknowledged the unique challenges of SIDS through various resolutions, which emphasise the need for climate justice and adherence to the 1.5 C climate target. Sustainable Development Goal 14 (SDG 14) brought attention to the direct impacts of climate change on oceans and the issues faced by SIDS. This paper reviews the historical and legal developments necessary for the sustainable development of SIDS, emphasising the nexus between climate change, ocean governance, and human rights. It highlights the potential for further advocacy and the interconnected nature of SDG 14 with judicial opinions.","PeriodicalId":12479,"journal":{"name":"Frontiers in Marine Science","volume":"314 1","pages":""},"PeriodicalIF":3.7,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146100","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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