Pub Date : 2026-03-01Epub Date: 2026-02-09DOI: 10.1016/j.seares.2026.102682
Caiyun Zhang
The Zhejiang–Fujian Coastal Front (ZFCF) is a key dynamic structure regulating material and energy exchanges on the East China Sea shelf and shaping regional fisheries and ecosystems; its long-term evolution is therefore critical for understanding shelf responses to climate change. Using sea surface temperature (SST) data from OSTIA and wind data from CCMP during 1987–2022, this study applied a gradient-based frontal-axis tracking method to examine winter and spring trends in the intensity and position of the ZFCF. The results show that the frontal intensity increased significantly, at rates of 2.78 × 10−3 °C/km per decade in winter and 3.20 × 10−3 °C/km per decade in spring. Concurrently, the frontal axis exhibited a westward migration, with more pronounced shifts between 26°N and 28°N. These changes were primarily driven by two mechanisms: enhanced onshore Ekman transport and an increased nearshore–offshore thermal contrast, the latter mainly resulting from offshore warming. These long-term changes provide insights into climate-induced shelf dynamics and support ecosystem-based marine resource management in the East China Sea.
{"title":"Winter–spring trends of the Zhejiang–Fujian coastal front in the East China Sea (1988–2022)","authors":"Caiyun Zhang","doi":"10.1016/j.seares.2026.102682","DOIUrl":"10.1016/j.seares.2026.102682","url":null,"abstract":"<div><div>The Zhejiang–Fujian Coastal Front (ZFCF) is a key dynamic structure regulating material and energy exchanges on the East China Sea shelf and shaping regional fisheries and ecosystems; its long-term evolution is therefore critical for understanding shelf responses to climate change. Using sea surface temperature (SST) data from OSTIA and wind data from CCMP during 1987–2022, this study applied a gradient-based frontal-axis tracking method to examine winter and spring trends in the intensity and position of the ZFCF. The results show that the frontal intensity increased significantly, at rates of 2.78 × 10<sup>−3</sup> °C/km per decade in winter and 3.20 × 10<sup>−3</sup> °C/km per decade in spring. Concurrently, the frontal axis exhibited a westward migration, with more pronounced shifts between 26°N and 28°N. These changes were primarily driven by two mechanisms: enhanced onshore Ekman transport and an increased nearshore–offshore thermal contrast, the latter mainly resulting from offshore warming. These long-term changes provide insights into climate-induced shelf dynamics and support ecosystem-based marine resource management in the East China Sea.</div></div>","PeriodicalId":50056,"journal":{"name":"Journal of Sea Research","volume":"210 ","pages":"Article 102682"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189581","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ostracods (micro-crustaceans) are widely distributed, abundant, and sensitive to environmental conditions that make them valuable indicators for human impacts and the reconstruction of palaeoenvironments and palaeoclimate. However, ostracods in Iceland are very poorly studied. To improve knowledge on the diversity and distribution of ostracods in coastal waters of Iceland, 11 sediment samples were collected from 5 to 86 m depth in the fjord Hvalfjörður. In addition, 16 samples were analysed as part of a biomonitoring experiment to investigate whether the deployment of 500 kg of lime-coated wood chips affects the ostracod assemblage over a period of ten months. As a result of the analysis, a total of 19 taxa were identified, with Elofsonella concinna, Sarsicytheridea bradii, Actinocythereis dunelmensis and Robertsonites tuberculatus representing the most abundant species. Propontocypris trigonella, Jonesia acuminata, Cytherura atra and Kyphocythere limicola are here reported for Icelandic waters for the first time. Baffinicythere emarginata and J. acuminata occur in Hvalfjörður probably close to their upper water-temperature-tolerance limits, representing most vulnerable taxa if waters warm due to global change. The deployment of wood chips did not cause significant changes of the ostracod assemblage during the observational period. These results provide important reference data for assessing future changes in ostracod diversity.
{"title":"Ostracoda from Hvalfjörður (W Iceland): Diversity, distribution and biomonitoring experiment","authors":"Sarah Schmickal , Hafrún Birta Hafliðadóttir , Angel Ruiz-Angulo , Hildur Magnúsdóttir , Íris Mýrdal Kristinsdóttir , Steffen Mischke","doi":"10.1016/j.seares.2026.102680","DOIUrl":"10.1016/j.seares.2026.102680","url":null,"abstract":"<div><div>Ostracods (micro-crustaceans) are widely distributed, abundant, and sensitive to environmental conditions that make them valuable indicators for human impacts and the reconstruction of palaeoenvironments and palaeoclimate. However, ostracods in Iceland are very poorly studied. To improve knowledge on the diversity and distribution of ostracods in coastal waters of Iceland, 11 sediment samples were collected from 5 to 86 m depth in the fjord Hvalfjörður. In addition, 16 samples were analysed as part of a biomonitoring experiment to investigate whether the deployment of 500 kg of lime-coated wood chips affects the ostracod assemblage over a period of ten months. As a result of the analysis, a total of 19 taxa were identified, with <em>Elofsonella concinna</em>, <em>Sarsicytheridea bradii</em>, <em>Actinocythereis dunelmensis</em> and <em>Robertsonites tuberculatus</em> representing the most abundant species. <em>Propontocypris trigonella</em>, <em>Jonesia acuminata</em>, <em>Cytherura atra</em> and <em>Kyphocythere limicola</em> are here reported for Icelandic waters for the first time. <em>Baffinicythere emarginata</em> and <em>J. acuminata</em> occur in Hvalfjörður probably close to their upper water-temperature-tolerance limits, representing most vulnerable taxa if waters warm due to global change. The deployment of wood chips did not cause significant changes of the ostracod assemblage during the observational period. These results provide important reference data for assessing future changes in ostracod diversity.</div></div>","PeriodicalId":50056,"journal":{"name":"Journal of Sea Research","volume":"210 ","pages":"Article 102680"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A nuanced understanding of the reproductive dynamics, growth trajectories, and environmental interactions of the Indian backwater oyster (Crassostrea madrasensis) is indispensable for advancing knowledge for ensuring population sustainability, tropical mariculture, and guiding conservation strategies in monsoon-driven tropical ecosystems. Therefore, this study undertook an integrated, year-long (May 2023–April 2024) investigation of reproductive biology, biometric growth patterns, and trophic relationships of C. madrasensis from the Moheshkhali Channel, a dynamic marine-influenced habitat along the southeast coast of the Bay of Bengal, Bangladesh, employing a multivariate analytical framework. Biometric assessments revealed consistent negative allometric growth, indicating preferential energetic allocation to shell accretion over somatic tissue development, thereby reflecting adaptive morphological plasticity in response to local environmental pressures. Histological analyses identified two distinct spawning peaks during the pre-monsoon (April–June) and post-monsoon (October–December) periods, corroborated by elevated condition indices (CI) and presumptive gonadosomatic indices (P.GSI). Seasonal fluctuations in sex ratios demonstrated a flexible reproductive strategy, characterized by female predominance during periods of heightened primary productivity and the occurrence of transient hermaphroditism during transitional months. Multivariate analyses (PCA and CVA) revealed strong seasonal coupling among reproductive stages, plankton ingestion patterns, and key environmental drivers, including temperature, salinity, dissolved oxygen, and nutrient availability. Planktonic diet composition exhibited pronounced seasonal shifts aligned with reproductive cycles, underscoring adaptive nutritional adjustments that support gametogenesis. The pre-monsoon reproductive phase appeared to rely primarily on endogenous energy reserves, whereas post-monsoon spawning was closely synchronized with peaks in phytoplankton abundance and nutrient influx, suggesting opportunistic utilization of exogenous energy inputs. Collectively, these findings advance ecological understanding of wild populations of C. madrasensis, offering vital baseline knowledge to guide conservation and sustainable utilization for maintaining natural oyster stocks and adaptive mariculture strategies in monsoon-influenced tropical estuarine environments.
{"title":"Linking estuarine ecology with reproductive phenology in the Indian backwater oyster Crassostrea madrasensis: A multivariate framework perspective","authors":"Afshana Ferdous , Israt Jahan , Sourav Chowdhury , Md Ramzan Ali , Md Nayeem Hossain , Md Moshiur Rahman , Mohammad Sadequr Rahman Khan , Md Asaduzzaman","doi":"10.1016/j.seares.2026.102677","DOIUrl":"10.1016/j.seares.2026.102677","url":null,"abstract":"<div><div>A nuanced understanding of the reproductive dynamics, growth trajectories, and environmental interactions of the Indian backwater oyster (<em>Crassostrea madrasensis</em>) is indispensable for advancing knowledge for ensuring population sustainability, tropical mariculture, and guiding conservation strategies in monsoon-driven tropical ecosystems. Therefore, this study undertook an integrated, year-long (May 2023–April 2024) investigation of reproductive biology, biometric growth patterns, and trophic relationships of <em>C. madrasensis</em> from the Moheshkhali Channel, a dynamic marine-influenced habitat along the southeast coast of the Bay of Bengal, Bangladesh, employing a multivariate analytical framework. Biometric assessments revealed consistent negative allometric growth, indicating preferential energetic allocation to shell accretion over somatic tissue development, thereby reflecting adaptive morphological plasticity in response to local environmental pressures. Histological analyses identified two distinct spawning peaks during the pre-monsoon (April–June) and post-monsoon (October–December) periods, corroborated by elevated condition indices (CI) and presumptive gonadosomatic indices (P.GSI). Seasonal fluctuations in sex ratios demonstrated a flexible reproductive strategy, characterized by female predominance during periods of heightened primary productivity and the occurrence of transient hermaphroditism during transitional months. Multivariate analyses (PCA and CVA) revealed strong seasonal coupling among reproductive stages, plankton ingestion patterns, and key environmental drivers, including temperature, salinity, dissolved oxygen, and nutrient availability. Planktonic diet composition exhibited pronounced seasonal shifts aligned with reproductive cycles, underscoring adaptive nutritional adjustments that support gametogenesis. The pre-monsoon reproductive phase appeared to rely primarily on endogenous energy reserves, whereas post-monsoon spawning was closely synchronized with peaks in phytoplankton abundance and nutrient influx, suggesting opportunistic utilization of exogenous energy inputs. Collectively, these findings advance ecological understanding of wild populations of <em>C. madrasensis</em>, offering vital baseline knowledge to guide conservation and sustainable utilization for maintaining natural oyster stocks and adaptive mariculture strategies in monsoon-influenced tropical estuarine environments.</div></div>","PeriodicalId":50056,"journal":{"name":"Journal of Sea Research","volume":"210 ","pages":"Article 102677"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146078790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2026-02-13DOI: 10.1016/j.seares.2026.102685
Xiaoyan Li , Kaida Xu , Wenjun Zheng , Kai Zhu , Dongming Lin
Marine fish, constituting critical components for marine ecosystems, exhibit trophodynamic characteristics in their energy storage strategies. However, evidence of such strategies for demersal fish remains inadequately characterized. Herein, we used seven ecologically and economically important demersal fish species from the coastal waters of the Zhoushan Archipelago (East China Sea) as a model system to investigate the trophodynamic characteristics. Sampled in April 2022, we quantified their muscle energy density, a metric of energy storage status and metabolic efficiency, and evaluated the effects of dietary habits through fatty acid biomarkers. We observed significant differences in the energy storage capacity among the species, with energy density ranging from 16.52 to 26.15 kJ g−1. Lipid content was the principal physiological correlate, explaining a substantial proportion (6–38.57%) of the total energetic value and exhibiting species-specific allometric scaling. Analysis of fatty acid profiles revealed interspecific dissimilarity, indicative of divergent feeding habits, and hierarchical modeling demonstrated that dietary composition exerts a significant modulating influence on the energy storage capacity. The muscle energy density was inversely related to zooplanktonivory biomarkers of C16:0, C18:0 and C18:1n9c, but positively correlated with the piscivory biomarker C22:6n3. These findings reveal interspecific variations in the energy storage capacity for the seven demersal fishes, linking to their feeding habits where trophic ecology fundamentally modulates this capacity, with high-quality prey facilitating energy storage.
海洋鱼类是海洋生态系统的重要组成部分，其能量储存策略表现出营养动力学特征。然而，这种策略对底栖鱼类的证据仍然没有充分表征。本文以舟山群岛（East China Sea，中国东海）沿海7种具有重要生态和经济意义的底栖鱼类为模型系统，研究了其营养动力学特征。我们于2022年4月取样，量化了它们的肌肉能量密度，这是一种能量储存状态和代谢效率的指标，并通过脂肪酸生物标志物评估了饮食习惯的影响。不同物种的能量储存能力差异显著，能量密度在16.52 ~ 26.15 kJ g−1之间。脂质含量是主要的生理相关因素，解释了总能量值的很大一部分（6-38.57%），并表现出物种特异性异速缩放。脂肪酸谱分析揭示了种间差异，表明了不同的摄食习惯，分层模型表明，膳食组成对能量储存能力有显著的调节影响。肌肉能量密度与浮游动物象牙生物标志物C16:0、C18:0和C18:1n9c呈负相关，与鱼类生物标志物C22:6n3呈正相关。这些发现揭示了七种底栖鱼类能量储存能力的种间差异，与它们的摄食习惯有关，营养生态从根本上调节了这种能力，高质量的猎物促进了能量储存。
{"title":"Trophic ecology underpins energy storage in demersal fishes from the Zhoushan Archipelago, East China Sea: insights from fatty acid biomarkers","authors":"Xiaoyan Li , Kaida Xu , Wenjun Zheng , Kai Zhu , Dongming Lin","doi":"10.1016/j.seares.2026.102685","DOIUrl":"10.1016/j.seares.2026.102685","url":null,"abstract":"<div><div>Marine fish, constituting critical components for marine ecosystems, exhibit trophodynamic characteristics in their energy storage strategies. However, evidence of such strategies for demersal fish remains inadequately characterized. Herein, we used seven ecologically and economically important demersal fish species from the coastal waters of the Zhoushan Archipelago (East China Sea) as a model system to investigate the trophodynamic characteristics. Sampled in April 2022, we quantified their muscle energy density, a metric of energy storage status and metabolic efficiency, and evaluated the effects of dietary habits through fatty acid biomarkers. We observed significant differences in the energy storage capacity among the species, with energy density ranging from 16.52 to 26.15 kJ g<sup>−1</sup>. Lipid content was the principal physiological correlate, explaining a substantial proportion (6–38.57%) of the total energetic value and exhibiting species-specific allometric scaling. Analysis of fatty acid profiles revealed interspecific dissimilarity, indicative of divergent feeding habits, and hierarchical modeling demonstrated that dietary composition exerts a significant modulating influence on the energy storage capacity. The muscle energy density was inversely related to zooplanktonivory biomarkers of C16:0, C18:0 and C18:1n9c, but positively correlated with the piscivory biomarker C22:6n3. These findings reveal interspecific variations in the energy storage capacity for the seven demersal fishes, linking to their feeding habits where trophic ecology fundamentally modulates this capacity, with high-quality prey facilitating energy storage.</div></div>","PeriodicalId":50056,"journal":{"name":"Journal of Sea Research","volume":"210 ","pages":"Article 102685"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147397524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2026-01-20DOI: 10.1016/j.seares.2026.102675
Ken Ishida , Yuki Kanamori , Yuan Yao , Yoko Wada , Takehisa Yamakita , Takashi Noda
In recent years, clarification of the impacts of marine heatwaves (MHWs) on marine ecosystems has become an important topic. However, most previous studies that have assessed impacts of MHWs have not adequately reduced stochasticity, which has led to insufficient assessment of the direct effects of MHWs. There are also few studies that evaluate the accumulative carryover effects; which occur when the effects of successive events accumulatively increase over time. In addition, many studies have examined the effects of MHWs on abundance, but relatively few on diversity. From 2010 to 2016, southeastern Hokkaido in northern Japan experienced successive MHWs. Here, we assessed the accumulative carryover effects and the impact of MHWs on diversity (species richness and abundance-weighted diversity indices) with reduced stochasticity for four major functional groups (macroalgae, sessile invertebrates, herbivorous mollusks, and carnivorous invertebrates) of rocky intertidal communities. Surveys were conducted before (2004–2009), during (2010–2016), and after (2017–2018) MHWs. We found that the accumulative carryover effects were not detected in diversity. The results demonstrate that MHWs are to lead to accumulative carryover effects on abundance than on diversity. We also found that the direct effects of MHWs on diversity (i.e., increase or decrease of diversity indices during and after MHWs) were different among the four functional groups. These results were due to differences in species composition within the functional groups, such as the proportion of warm water species and cold affinity species and the proportion of dominant species. Thus, multiple metrics should be quantified simultaneously when assessing impacts on MHWs.
{"title":"Assessing the impact of successive marine heatwaves on the diversity of rocky intertidal communities","authors":"Ken Ishida , Yuki Kanamori , Yuan Yao , Yoko Wada , Takehisa Yamakita , Takashi Noda","doi":"10.1016/j.seares.2026.102675","DOIUrl":"10.1016/j.seares.2026.102675","url":null,"abstract":"<div><div>In recent years, clarification of the impacts of marine heatwaves (MHWs) on marine ecosystems has become an important topic. However, most previous studies that have assessed impacts of MHWs have not adequately reduced stochasticity, which has led to insufficient assessment of the direct effects of MHWs. There are also few studies that evaluate the accumulative carryover effects; which occur when the effects of successive events accumulatively increase over time. In addition, many studies have examined the effects of MHWs on abundance, but relatively few on diversity. From 2010 to 2016, southeastern Hokkaido in northern Japan experienced successive MHWs. Here, we assessed the accumulative carryover effects and the impact of MHWs on diversity (species richness and abundance-weighted diversity indices) with reduced stochasticity for four major functional groups (macroalgae, sessile invertebrates, herbivorous mollusks, and carnivorous invertebrates) of rocky intertidal communities. Surveys were conducted before (2004–2009), during (2010–2016), and after (2017–2018) MHWs. We found that the accumulative carryover effects were not detected in diversity. The results demonstrate that MHWs are to lead to accumulative carryover effects on abundance than on diversity. We also found that the direct effects of MHWs on diversity (i.e., increase or decrease of diversity indices during and after MHWs) were different among the four functional groups. These results were due to differences in species composition within the functional groups, such as the proportion of warm water species and cold affinity species and the proportion of dominant species. Thus, multiple metrics should be quantified simultaneously when assessing impacts on MHWs.</div></div>","PeriodicalId":50056,"journal":{"name":"Journal of Sea Research","volume":"210 ","pages":"Article 102675"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146038833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2025-12-31DOI: 10.1016/j.seares.2025.102665
Shenglin Zhou , Zhicheng Wan , Xinwei Li
Marine financial support, as an important means of optimizing resource allocation and risk protection in coastal areas, provides key support for enhancing economic resilience and achieving sustainable development. This paper constructs the Marine financial support index based on panel data of 11 coastal provinces in China from 2011 to 2023, and uses fixed effects, instrumental variables and threshold models to systematically evaluate its economic and ecological effects. The study found that Marine financial support significantly enhanced the economic resilience and sustainable development level of coastal regions, and its promoting effect was achieved through the optimization of capital factor allocation and the improvement of green innovation capacity, and showed obvious nonlinear threshold characteristics. Heterogeneity analysis shows that after the release of the maritime power strategy, the function of Marine finance has shifted from scale expansion to quality improvement, and its role is more prominent in regions with a better economic foundation, moderate environmental regulations and southern coastal areas. This paper provides empirical evidence and policy references for optimizing the allocation of Marine financial resources and enhancing the resilience and green transformation capacity of coastal systems.
{"title":"Research on the impact of marine financial support on economic resilience and sustainable development in coastal areas","authors":"Shenglin Zhou , Zhicheng Wan , Xinwei Li","doi":"10.1016/j.seares.2025.102665","DOIUrl":"10.1016/j.seares.2025.102665","url":null,"abstract":"<div><div>Marine financial support, as an important means of optimizing resource allocation and risk protection in coastal areas, provides key support for enhancing economic resilience and achieving sustainable development. This paper constructs the Marine financial support index based on panel data of 11 coastal provinces in China from 2011 to 2023, and uses fixed effects, instrumental variables and threshold models to systematically evaluate its economic and ecological effects. The study found that Marine financial support significantly enhanced the economic resilience and sustainable development level of coastal regions, and its promoting effect was achieved through the optimization of capital factor allocation and the improvement of green innovation capacity, and showed obvious nonlinear threshold characteristics. Heterogeneity analysis shows that after the release of the maritime power strategy, the function of Marine finance has shifted from scale expansion to quality improvement, and its role is more prominent in regions with a better economic foundation, moderate environmental regulations and southern coastal areas. This paper provides empirical evidence and policy references for optimizing the allocation of Marine financial resources and enhancing the resilience and green transformation capacity of coastal systems.</div></div>","PeriodicalId":50056,"journal":{"name":"Journal of Sea Research","volume":"210 ","pages":"Article 102665"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145980221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2026-01-08DOI: 10.1016/j.seares.2026.102669
Hanna-May Malahel , Charlotte R. Dromard , Isabelle Mussio , Pascal Claquin
This review explores the application of nitrogen stable isotopes measurements as a tool for monitoring nitrogen inputs in coastal zones, focusing on oligotrophic tropical ecosystems. Pulsed nutrient enrichment leads to the proliferation of macroalgae, compromising the health of coral reefs and seagrass beds. Through the analysis of 52 studies, we compile isotopic signatures measured in macroalgae and seagrass, while proposing reference thresholds to identify nitrogen pollution sources in tropical areas. By standardizing these isotopic compositions, our review aims to provide useful benchmarks for researchers and managers of coastal ecosystems. The main pollution sources identified include wastewater, groundwater, aquaculture, and fertilizers, each characterized by distinct δ15N ranges. Among these, wastewater and sewage show the highest isotopic values (>10 ‰), while inorganic fertilizers exhibit the lowest (down to −4.5 ‰). Macroalgae, particularly Dictyota and Rhodophyta species (e.g. Laurencia), were most frequently used as bioindicators due to their wide distribution and responsiveness to nutrient variation. Thalassia testudinum emerged as the most commonly used seagrass species across studies. However, seagrasses overall were less frequently employed than macroalgae, and typically displayed less sensitivity to nitrogen enrichment in their isotopic signatures. The review highlights practical aspects of isotopic monitoring, including macrophyte selection, caging techniques, sample preparation, and environmental variables affecting interpretation such as seasonality, depth, and hydrodynamic conditions. Caging, though underused in seagrass studies, proved essential in areas lacking native bioindicators. Finally, we provide recommendations for future studies to enhance consistency and standardization allowing temporal and intersites comparisons. This approach offers a cost-effective and sensitive tool for detecting nutrient inputs in vulnerable tropical ecosystems.
{"title":"Monitoring nitrogen pollution using isotopic composition of macrophytes in oligotrophic tropical coastal areas: A short review","authors":"Hanna-May Malahel , Charlotte R. Dromard , Isabelle Mussio , Pascal Claquin","doi":"10.1016/j.seares.2026.102669","DOIUrl":"10.1016/j.seares.2026.102669","url":null,"abstract":"<div><div>This review explores the application of nitrogen stable isotopes measurements as a tool for monitoring nitrogen inputs in coastal zones, focusing on oligotrophic tropical ecosystems. Pulsed nutrient enrichment leads to the proliferation of macroalgae, compromising the health of coral reefs and seagrass beds. Through the analysis of 52 studies, we compile isotopic signatures measured in macroalgae and seagrass, while proposing reference thresholds to identify nitrogen pollution sources in tropical areas. By standardizing these isotopic compositions, our review aims to provide useful benchmarks for researchers and managers of coastal ecosystems. The main pollution sources identified include wastewater, groundwater, aquaculture, and fertilizers, each characterized by distinct δ<sup>15</sup>N ranges. Among these, wastewater and sewage show the highest isotopic values (>10 ‰), while inorganic fertilizers exhibit the lowest (down to −4.5 ‰). Macroalgae, particularly <em>Dictyota</em> and Rhodophyta species (e.g. <em>Laurencia</em>), were most frequently used as bioindicators due to their wide distribution and responsiveness to nutrient variation. <em>Thalassia testudinum</em> emerged as the most commonly used seagrass species across studies. However, seagrasses overall were less frequently employed than macroalgae, and typically displayed less sensitivity to nitrogen enrichment in their isotopic signatures. The review highlights practical aspects of isotopic monitoring, including macrophyte selection, caging techniques, sample preparation, and environmental variables affecting interpretation such as seasonality, depth, and hydrodynamic conditions. Caging, though underused in seagrass studies, proved essential in areas lacking native bioindicators. Finally, we provide recommendations for future studies to enhance consistency and standardization allowing temporal and intersites comparisons. This approach offers a cost-effective and sensitive tool for detecting nutrient inputs in vulnerable tropical ecosystems.</div></div>","PeriodicalId":50056,"journal":{"name":"Journal of Sea Research","volume":"210 ","pages":"Article 102669"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145929181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2026-01-13DOI: 10.1016/j.seares.2026.102671
Tavailau Tauala Segi , Richard A. Gill
Terrigenous sediment transport is a major driver of coastal degradation in high-island tropical systems, where steep volcanic watersheds rapidly deliver sediment to the nearshore littoral zone. Indigenous Hawaiian fishponds are engineered coastal embankments with sluice structures that retain land-derived sediments and limit their dispersal across reef platforms. This study quantified the distribution of terrigenous sediment within and adjacent to coastal fishponds along the south-central shore of Moloka'i, Hawaii, using grain-size analysis and elemental composition. We also assessed whether fishpond wall restoration influences sediment retention and whether coastal drainage channels affect spatial sediment patterns across the inner littoral zone. Our results show that fishponds retain significantly higher proportions of clay, fine silt, and land-derived trace elements compared to adjacent open coastal flats, confirming their role as effective sediment traps. While restoration status influences elemental accumulation associated with embankment structure and hydrological connectivity, it does not significantly affect particle-size distribution. Spatial patterns of terrigenous sediment across the inner littoral zone were more strongly associated with proximity to watershed outlets than with fishpond condition. These findings demonstrate that traditional coastal embankments can meaningfully modulate watershed-to-coastal sediment fluxes, highlighting their relevance to contemporary sediment-mitigation and coastal-management strategies in Pacific Island ecosystems.
{"title":"Indigenous fishponds are sediment traps for terrigenous sediment on the southern coast of Moloka'i, Hawaii","authors":"Tavailau Tauala Segi , Richard A. Gill","doi":"10.1016/j.seares.2026.102671","DOIUrl":"10.1016/j.seares.2026.102671","url":null,"abstract":"<div><div>Terrigenous sediment transport is a major driver of coastal degradation in high-island tropical systems, where steep volcanic watersheds rapidly deliver sediment to the nearshore littoral zone. Indigenous Hawaiian fishponds are engineered coastal embankments with sluice structures that retain land-derived sediments and limit their dispersal across reef platforms. This study quantified the distribution of terrigenous sediment within and adjacent to coastal fishponds along the south-central shore of Moloka'i, Hawaii, using grain-size analysis and elemental composition. We also assessed whether fishpond wall restoration influences sediment retention and whether coastal drainage channels affect spatial sediment patterns across the inner littoral zone. Our results show that fishponds retain significantly higher proportions of clay, fine silt, and land-derived trace elements compared to adjacent open coastal flats, confirming their role as effective sediment traps. While restoration status influences elemental accumulation associated with embankment structure and hydrological connectivity, it does not significantly affect particle-size distribution. Spatial patterns of terrigenous sediment across the inner littoral zone were more strongly associated with proximity to watershed outlets than with fishpond condition. These findings demonstrate that traditional coastal embankments can meaningfully modulate watershed-to-coastal sediment fluxes, highlighting their relevance to contemporary sediment-mitigation and coastal-management strategies in Pacific Island ecosystems.</div></div>","PeriodicalId":50056,"journal":{"name":"Journal of Sea Research","volume":"210 ","pages":"Article 102671"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146038777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In recent decades, oligotrophication and climate change have impacted the structure and functioning of aquatic ecosystems. The combined effects of these two forcing have been studied little, particularly in Mediterranean coastal lagoons, which are considered vulnerable sentinel ecosystems that harbor numerous ecosystem services. Phytoplankton communities are a sensitive indicator of hydroclimatic changes; however there is a lack of knowledge regarding long-term changes in their trends and seasonality. Using time-series analyses from 22 years of environmental monitoring in a large coastal lagoon (Thau lagoon), we examined trends in hydrological and climatic variables, as well as phytoplankton biomass and microphytoplankton abundance. We examined the seasonal patterns of 56 dominant taxonomic units (TUs) of diatoms and dinoflagellates, identifying the primary hydrological and climatic variables that determine changes in their seasonality. Our results reveal an unprecedented increase in seawater temperature of +0.09 °C yr−1 from 1998 to 2019. Diatom abundance decreased significantly over the last decade, with earlier peaks. The three main planktonic diatoms (Skeletonema, Pseudo-nitzschia and Chaetoceros), which are dominant in spring and winter, all showed decreasing trends and unprecedented changes in their seasonality for first two. In contrast, benthic diatoms (Cylindrotheca, Nitszchia, Hantzschia) and two other summer taxa increased steadily. Seawater temperature and solar radiation appear to be the main drivers of changes in community seasonality. Results from long-term phytoplankton monitoring are essential for identifying future changes in coastal ecosystems, as such changes could have cascading impacts on the entire food web and substantial economic repercussions.
{"title":"Long-term impacts of climate change on the seasonal trajectories of phytoplankton in a coastal lagoon (western Mediterranean Sea)","authors":"Béatrice Bec , Dominique Soudant , Tania Hernández-Fariñas , Ophélie Serais , Elise Caillard , Valérie Derolez","doi":"10.1016/j.seares.2026.102678","DOIUrl":"10.1016/j.seares.2026.102678","url":null,"abstract":"<div><div>In recent decades, oligotrophication and climate change have impacted the structure and functioning of aquatic ecosystems. The combined effects of these two forcing have been studied little, particularly in Mediterranean coastal lagoons, which are considered vulnerable sentinel ecosystems that harbor numerous ecosystem services. Phytoplankton communities are a sensitive indicator of hydroclimatic changes; however there is a lack of knowledge regarding long-term changes in their trends and seasonality. Using time-series analyses from 22 years of environmental monitoring in a large coastal lagoon (Thau lagoon), we examined trends in hydrological and climatic variables, as well as phytoplankton biomass and microphytoplankton abundance. We examined the seasonal patterns of 56 dominant taxonomic units (TUs) of diatoms and dinoflagellates, identifying the primary hydrological and climatic variables that determine changes in their seasonality. Our results reveal an unprecedented increase in seawater temperature of +0.09 °C yr<sup>−1</sup> from 1998 to 2019. Diatom abundance decreased significantly over the last decade, with earlier peaks. The three main planktonic diatoms (<em>Skeletonema</em>, <em>Pseudo-nitzschia</em> and <em>Chaetoceros</em>), which are dominant in spring and winter, all showed decreasing trends and unprecedented changes in their seasonality for first two. In contrast, benthic diatoms (<em>Cylindrotheca</em>, <em>Nitszchia</em>, <em>Hantzschia</em>) and two other summer taxa increased steadily. Seawater temperature and solar radiation appear to be the main drivers of changes in community seasonality. Results from long-term phytoplankton monitoring are essential for identifying future changes in coastal ecosystems, as such changes could have cascading impacts on the entire food web and substantial economic repercussions.</div></div>","PeriodicalId":50056,"journal":{"name":"Journal of Sea Research","volume":"210 ","pages":"Article 102678"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189228","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-03-01Epub Date: 2026-02-08DOI: 10.1016/j.seares.2026.102683
Maxime Daviray , Emmanuelle Geslin , Edouard Metzger , Sophie Quinchard , Bruno Deflandre , Céline Charbonnier , Pierre Anschutz
As many coastal areas draining intensive agricultural activities, Ledano estuary mudflats (French Brittany) experience Ulva proliferation, causing green tides. We studied the seasonal dynamics of sulphoxidizing cable bacteria from April 2019 to July 2020 using microsensors (O2, pH, H2S). The activity of these filamentous bacteria, called electrogenic sulphur oxidation (eSOx), results in strong acidification and in pore-water CO32− depletion in the first few centimeters of sediment (within the suboxic zone). Living and dead benthic foraminiferal assemblages were studied in July 2020 to observe the effects of eSOx on the calcareous meiofauna and their shell preservation in the sediment. eSOx was patchy on the mudflat but persistent throughout the year. It contributed up to 45% of oxygen consumption during the algal mat decay, and exceeded 100% during the flooding period suggesting stimulation by nitrate inputs. The corrosive effect was maximal in July 2020 (∆pH ∼ 1.7, [CO32−]calc < 10 μM). The living foraminiferal community was sparse and nearly monospecific, dominated by the calcareous species Haynesina germanica, probably due to green tides coupled with eSOx-driven acidification. However, living specimens of H. germanica showed no signs of advanced dissolution of their shell suggesting a biological capacity to survive in such environmental acidification, potentially linked to their photosynthetic capability. In contrast, the dead assemblages displayed greater diversity despite a loss of about 20% of the calcareous shell recording with depth due to the synergetic effect of low salinity and eSOx. Overall, this study shows that green tides strongly influence cable bacteria activity and then, sedimentary biogeochemical processes in eutrophic coastal environments.
{"title":"Seasonal dynamics of cable bacteria in an estuarine intertidal mudflat subject to green tides: Implications for the foraminiferal community and test preservation","authors":"Maxime Daviray , Emmanuelle Geslin , Edouard Metzger , Sophie Quinchard , Bruno Deflandre , Céline Charbonnier , Pierre Anschutz","doi":"10.1016/j.seares.2026.102683","DOIUrl":"10.1016/j.seares.2026.102683","url":null,"abstract":"<div><div>As many coastal areas draining intensive agricultural activities, Ledano estuary mudflats (French Brittany) experience <em>Ulva</em> proliferation, causing green tides. We studied the seasonal dynamics of sulphoxidizing cable bacteria from April 2019 to July 2020 using microsensors (O<sub>2</sub>, pH, H<sub>2</sub>S). The activity of these filamentous bacteria, called electrogenic sulphur oxidation (eSOx), results in strong acidification and in pore-water CO<sub>3</sub><sup>2−</sup> depletion in the first few centimeters of sediment (within the suboxic zone). Living and dead benthic foraminiferal assemblages were studied in July 2020 to observe the effects of eSOx on the calcareous meiofauna and their shell preservation in the sediment. eSOx was patchy on the mudflat but persistent throughout the year. It contributed up to 45% of oxygen consumption during the algal mat decay, and exceeded 100% during the flooding period suggesting stimulation by nitrate inputs. The corrosive effect was maximal in July 2020 (∆pH ∼ 1.7, [CO<sub>3</sub><sup>2−</sup>]<sub>calc</sub> < 10 μM). The living foraminiferal community was sparse and nearly monospecific, dominated by the calcareous species <em>Haynesina germanica</em>, probably due to green tides coupled with eSOx-driven acidification. However, living specimens of <em>H. germanica</em> showed no signs of advanced dissolution of their shell suggesting a biological capacity to survive in such environmental acidification, potentially linked to their photosynthetic capability. In contrast, the dead assemblages displayed greater diversity despite a loss of about 20% of the calcareous shell recording with depth due to the synergetic effect of low salinity and eSOx. Overall, this study shows that green tides strongly influence cable bacteria activity and then, sedimentary biogeochemical processes in eutrophic coastal environments.</div></div>","PeriodicalId":50056,"journal":{"name":"Journal of Sea Research","volume":"210 ","pages":"Article 102683"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189577","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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