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The hydrodynamic performance of a floating oscillating water column (OWC) breakwater under the co-action of waves and currents is numerically investigated. A time domain two-dimensional (2D) fully nonlinear numerical model was established for the OWC-breakwater, and its reliability was validated using experimental data. The effects of the current speed, the rear wall draft, and the rear wall thickness on the transmission coefficient, the reflection coefficient, and the hydrodynamic efficiency are numerically analyzed. The results indicate that under following current conditions, the transmission coefficient, reflection coefficient, and hydrodynamic efficiency of the device all exhibit a decreasing trend; whereas under opposing current conditions, the opposite trends are observed. Furthermore, increasing the rear wall draft reduces the transmission coefficient and improves the hydrodynamic efficiency, with a limited effect on the reflection coefficient. Besides, increasing the rear wall thickness also decreases the transmission coefficient and enhances hydrodynamic efficiency, while its influence on the reflection coefficient is insignificant. The findings of this study provide important references for the structural optimization and engineering design of OWC breakwaters.
The hydrodynamic performance of a floating oscillating water column (OWC) breakwater under the co-action of waves and currents is numerically investigated. A time domain two-dimensional (2D) fully nonlinear numerical model was established for the OWC-breakwater, and its reliability was validated using experimental data. The effects of the current speed, the rear wall draft, and the rear wall thickness on the transmission coefficient, the reflection coefficient, and the hydrodynamic efficiency are numerically analyzed. The results indicate that under following current conditions, the transmission coefficient, reflection coefficient, and hydrodynamic efficiency of the device all exhibit a decreasing trend; whereas under opposing current conditions, the opposite trends are observed. Furthermore, increasing the rear wall draft reduces the transmission coefficient and improves the hydrodynamic efficiency, with a limited effect on the reflection coefficient. Besides, increasing the rear wall thickness also decreases the transmission coefficient and enhances hydrodynamic efficiency, while its influence on the reflection coefficient is insignificant. The findings of this study provide important references for the structural optimization and engineering design of OWC breakwaters.
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Coral reef ecological restoration is internationally recognized as a pivotal technology and essential approach to reverse the degradation trend of coral reefs, which requires selecting native coral species for restoration and matched artificial reefs based on local conditions. Taking the degraded coral reef area of Weizhou Island, Guangxi as the research object, this study systematically investigated the growth adaptability of hermatypic stony corals and their compatibility with artificial reefs through a 10-month monitoring program of artificial nursery cultivation and an 18-month transplantation experiment involving three types of concrete artificial reefs (trapezoidal, table-shaped, and truncated conical). The results showed that the 10-month survival rates of all four tested coral species exceeded 85%. Both Acropora muricata and Acropora hyacinthus achieved 100% survival. Acropora hyacinthus exhibited a higher growth rate of living tissue projection area during some periods, while Acropora muricata performed better comprehensively in terms of survival stability, three-dimensional morphology formation, and engineering application potential, and can be used as the core restoration species. Among the three types of artificial reefs, the 18-month survival rate of corals on the trapezoidal artificial reef reached 92%, which was significantly higher than that on the truncated conical reef (77%) and the table-shaped reef (60%). Under environmental stress, physiological indicators including effective quantum yield and net photosynthetic rate showed significant specific responses to reef shapes, with the trapezoidal artificial reef demonstrating superior resistance to high temperature and typhoon stress as well as stronger damage recovery capability. The coral reef ecological restoration model established in this study—featuring Acropora muricata as the main restoration species, cable tie binding as the fixation method, metal seedbeds as the cultivation carrier, and trapezoidal artificial reefs as the colonization substrate—provides a scientific basis and practical technical reference for coral reef ecological restoration in typhoon-prone subtropical marine areas of China.
Coral reef ecological restoration is internationally recognized as a pivotal technology and essential approach to reverse the degradation trend of coral reefs, which requires selecting native coral species for restoration and matched artificial reefs based on local conditions. Taking the degraded coral reef area of Weizhou Island, Guangxi as the research object, this study systematically investigated the growth adaptability of hermatypic stony corals and their compatibility with artificial reefs through a 10-month monitoring program of artificial nursery cultivation and an 18-month transplantation experiment involving three types of concrete artificial reefs (trapezoidal, table-shaped, and truncated conical). The results showed that the 10-month survival rates of all four tested coral species exceeded 85%. Both Acropora muricata and Acropora hyacinthus achieved 100% survival. Acropora hyacinthus exhibited a higher growth rate of living tissue projection area during some periods, while Acropora muricata performed better comprehensively in terms of survival stability, three-dimensional morphology formation, and engineering application potential, and can be used as the core restoration species. Among the three types of artificial reefs, the 18-month survival rate of corals on the trapezoidal artificial reef reached 92%, which was significantly higher than that on the truncated conical reef (77%) and the table-shaped reef (60%). Under environmental stress, physiological indicators including effective quantum yield and net photosynthetic rate showed significant specific responses to reef shapes, with the trapezoidal artificial reef demonstrating superior resistance to high temperature and typhoon stress as well as stronger damage recovery capability. The coral reef ecological restoration model established in this study—featuring Acropora muricata as the main restoration species, cable tie binding as the fixation method, metal seedbeds as the cultivation carrier, and trapezoidal artificial reefs as the colonization substrate—provides a scientific basis and practical technical reference for coral reef ecological restoration in typhoon-prone subtropical marine areas of China.
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The mantle tissue and its mucus of the hard clam Meretrix meretrix play a significant role in defending against pathogens. However, the potential links between the composition and function of their inherent microbiota and host immunity remains unclear. In this study, 16S rRNA gene high-throughput sequencing was used to compare the microbiota composition and potential functions between the mantle tissue (group M) and mantle mucus (group N) in health clams. Non-targeted metabolomics (UHPLC-Q-TOF/MS) was employed to analyze metabolite changes in the mantle mucus under Vibrio stress. Furthermore, spearman correlation analysis was applied to integrate the microbiota and metabolomics data, aiming to preliminarily explore potential associations between the microbiota and host immune metabolism. The results revealed significant niche differentiation between the mantle and mucus microbiota. The mantle microbiota exhibited higher richness and was dominated by the phylum Spirochaetota, while the mucus microbiota showed higher evenness, with Proteobacteria and Bacteroidota as the dominant phyla. The mucus was significantly enriched in taxa with polysaccharide-degrading or potential pathogenic capabilities, such as the genera vibrio, Tenacibaculum and Flavobacterium. Functional prediction indicated that the mucus microbiota was more active in immune- and energy-related pathways, like cysteine and methionine metabolism and oxidative phosphorylation. Metabolomic analysis under Vibrio stress showed significant alterations in various immune-related metabolites in the mucus, including succinate acid, propionate acid, and phenylalanine. Correlation analysis between microbiota and metabolites revealed close associations between resident microbes and host metabolites, such as a strong positive correlation between the genus Marinomonas and uracil, and a strong negative correlation between Flavobacterium and nitrate. Collectively, these findings suggest that the mantle-mucus complex functions as a dynamic interfacial microenvironment. Its specific microbial community structure may interact with host metabolism, providing immunological preparedness for the host to counteract pathogen invasion.
The mantle tissue and its mucus of the hard clam Meretrix meretrix play a significant role in defending against pathogens. However, the potential links between the composition and function of their inherent microbiota and host immunity remains unclear. In this study, 16S rRNA gene high-throughput sequencing was used to compare the microbiota composition and potential functions between the mantle tissue (group M) and mantle mucus (group N) in health clams. Non-targeted metabolomics (UHPLC-Q-TOF/MS) was employed to analyze metabolite changes in the mantle mucus under Vibrio stress. Furthermore, spearman correlation analysis was applied to integrate the microbiota and metabolomics data, aiming to preliminarily explore potential associations between the microbiota and host immune metabolism. The results revealed significant niche differentiation between the mantle and mucus microbiota. The mantle microbiota exhibited higher richness and was dominated by the phylum Spirochaetota, while the mucus microbiota showed higher evenness, with Proteobacteria and Bacteroidota as the dominant phyla. The mucus was significantly enriched in taxa with polysaccharide-degrading or potential pathogenic capabilities, such as the genera vibrio, Tenacibaculum and Flavobacterium. Functional prediction indicated that the mucus microbiota was more active in immune- and energy-related pathways, like cysteine and methionine metabolism and oxidative phosphorylation. Metabolomic analysis under Vibrio stress showed significant alterations in various immune-related metabolites in the mucus, including succinate acid, propionate acid, and phenylalanine. Correlation analysis between microbiota and metabolites revealed close associations between resident microbes and host metabolites, such as a strong positive correlation between the genus Marinomonas and uracil, and a strong negative correlation between Flavobacterium and nitrate. Collectively, these findings suggest that the mantle-mucus complex functions as a dynamic interfacial microenvironment. Its specific microbial community structure may interact with host metabolism, providing immunological preparedness for the host to counteract pathogen invasion.
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High-stability monitoring of air-sea CO2 partial pressure (pCO2) is fundamental for assessing air-sea CO2 fluxes across long temporal and broad spatial scales. Among the commonly used methods worldwide, the air-water equilibration technique and the membrane-based diffusion technique are widely applied for measuring pCO2. In this study, we conducted underway continuous observations in Yueqing Bay and a 50-hour fixed-point deployment near Bianmanyu Island using the LI-5405A (air-water equilibration method) and the CONTROS HydroC® CO2 sensor (membrane equilibration method). The performance characteristics and application scenarios of the two approaches were systematically compared. The average difference between the two methods was 0.76 ± 4.46 μatm during the entire observation period, but both approaches produced consistent temporal trends with strong correlation. These two approaches exhibited distinct advantages: the membrane equilibrium method features low power consumption and an integrated watertight design, making it suitable for long-term continuous monitoring in in-situ scenarios or where power supply and space are limited. The air-water equilibration method, featuring rapid response and high precision, is more applicable for high-resolution measurements in dynamic environments. We propose a synergistic observational framework combining baseline monitoring using the membrane equilibration technique with periodic calibration via the air-water equilibration method. This integrated approach enhances both temporal and spatial resolution of air-sea CO2 flux observations, thereby improving data reliability and providing robust technical support for nearshore carbon source-sink assessments.
High-stability monitoring of air-sea CO2 partial pressure (pCO2) is fundamental for assessing air-sea CO2 fluxes across long temporal and broad spatial scales. Among the commonly used methods worldwide, the air-water equilibration technique and the membrane-based diffusion technique are widely applied for measuring pCO2. In this study, we conducted underway continuous observations in Yueqing Bay and a 50-hour fixed-point deployment near Bianmanyu Island using the LI-5405A (air-water equilibration method) and the CONTROS HydroC® CO2 sensor (membrane equilibration method). The performance characteristics and application scenarios of the two approaches were systematically compared. The average difference between the two methods was 0.76 ± 4.46 μatm during the entire observation period, but both approaches produced consistent temporal trends with strong correlation. These two approaches exhibited distinct advantages: the membrane equilibrium method features low power consumption and an integrated watertight design, making it suitable for long-term continuous monitoring in in-situ scenarios or where power supply and space are limited. The air-water equilibration method, featuring rapid response and high precision, is more applicable for high-resolution measurements in dynamic environments. We propose a synergistic observational framework combining baseline monitoring using the membrane equilibration technique with periodic calibration via the air-water equilibration method. This integrated approach enhances both temporal and spatial resolution of air-sea CO2 flux observations, thereby improving data reliability and providing robust technical support for nearshore carbon source-sink assessments.
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To overcome key challenges such as the tendency of seeds to drift with water currents during sowing and low seedling establishment rates, this study focused on eelgrass (Zostera marina), a dominant temperate seagrass species. The effects of two types of pelleting matrices—wood-based and mineral-based—and varying drying durations (0–12 min) on the physical and physiological properties of eelgrass seeds were systematically investigated. Following a preliminary screening of groups exhibiting germination potential, the impacts of these treatments on seed germination and seedling establishment were further evaluated. Results demonstrated that prolonged drying significantly enhanced both sinking acceleration and compressive strength of granulated seeds. Notably, seeds coated with the mineral-based matrix exhibited the highest sinking acceleration, reaching 3.2 times that of uncoated seeds, and displayed 3.1 times greater compressive strength than those in the wood-based matrix group. However, seed viability decreased progressively with increasing drying time: the uncoated and wood-based matrix groups maintained viability above 80% up to 8 min of drying, whereas the mineral-based group fell below this threshold after only 4 min. The wood-based matrix played a protective role in alleviating physiological stress induced by drying. Throughout the 0–12 min drying period, α-/β-amylase activities and total protein content in the wood-based matrix group remained comparable to those in the uncoated control group and were significantly higher than those in the mineral-based matrix group (P < 0.05). With respect to seedling establishment, the wood-based matrix treatment achieved rates of 39.0%–43.0% under drying durations of 0–4 min, which were statistically similar to the uncoated control (42.0%) and markedly higher than those observed in the mineral-based treatment (8%–12.5%). Correlation analysis revealed a highly significant positive association between seedling establishment rate and key physiological parameters, including enzyme activity and protein content. Furthermore, comprehensive benefit index analysis indicated that the wood-based matrix could achieve an optimal trade-off between physical suitability and physiological vitality when drying duration was restricted to 2–4 min. These findings suggest that using a wood-based pelleting matrix combined with a short drying duration (2–4 min) is a feasible and effective strategy for improving Z. marina seed handling and establishment in seagrass restoration practices.
To overcome key challenges such as the tendency of seeds to drift with water currents during sowing and low seedling establishment rates, this study focused on eelgrass (Zostera marina), a dominant temperate seagrass species. The effects of two types of pelleting matrices—wood-based and mineral-based—and varying drying durations (0–12 min) on the physical and physiological properties of eelgrass seeds were systematically investigated. Following a preliminary screening of groups exhibiting germination potential, the impacts of these treatments on seed germination and seedling establishment were further evaluated. Results demonstrated that prolonged drying significantly enhanced both sinking acceleration and compressive strength of granulated seeds. Notably, seeds coated with the mineral-based matrix exhibited the highest sinking acceleration, reaching 3.2 times that of uncoated seeds, and displayed 3.1 times greater compressive strength than those in the wood-based matrix group. However, seed viability decreased progressively with increasing drying time: the uncoated and wood-based matrix groups maintained viability above 80% up to 8 min of drying, whereas the mineral-based group fell below this threshold after only 4 min. The wood-based matrix played a protective role in alleviating physiological stress induced by drying. Throughout the 0–12 min drying period, α-/β-amylase activities and total protein content in the wood-based matrix group remained comparable to those in the uncoated control group and were significantly higher than those in the mineral-based matrix group (P < 0.05). With respect to seedling establishment, the wood-based matrix treatment achieved rates of 39.0%–43.0% under drying durations of 0–4 min, which were statistically similar to the uncoated control (42.0%) and markedly higher than those observed in the mineral-based treatment (8%–12.5%). Correlation analysis revealed a highly significant positive association between seedling establishment rate and key physiological parameters, including enzyme activity and protein content. Furthermore, comprehensive benefit index analysis indicated that the wood-based matrix could achieve an optimal trade-off between physical suitability and physiological vitality when drying duration was restricted to 2–4 min. These findings suggest that using a wood-based pelleting matrix combined with a short drying duration (2–4 min) is a feasible and effective strategy for improving Z. marina seed handling and establishment in seagrass restoration practices.
, Available online , doi: 10.12284/hyxb20260000
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Artemia is important live bait in the cultivation of marine fish and crustacean seedlings, with more than 90% derived from wild Artemia resources. In order to study the effects of environmental changes and the unique aquaculture and harvest management on the morphometrical and genetic characteristics of Artemia in Yuncheng Salt Lake, Shanxi Province in the past 30 years, Artemia cysts collected in 1993 (YC-1993), 2019 (YC-2019) and 2023 (YC-2023) from Yuncheng Salt Lake were cultured and morphometrical measurements were conducted. Specific-locus amplified fragments sequencing (SLAF-seq) was used for population genetics analysis. The results showed that the YC-2023 group was extremely significantly larger than the YC-1993 group in terms of body length, abdominal length, ovary width, interocular distance, eye diameter, second antenna length, and peripheral claspers, while the cyst diameter of the YC-2023 group was significantly smaller than that of the YC-1993 group. The results of genetic analysis showed that the YC-2023 group had the lowest genetic diversity. The polymorphism information content (PIC) of three populations was between 0.252 and 0.305, showing moderate polymorphism (0.25<PIC<0.5). The Fst value of the genetic differentiation coefficient between the YC-2019 and YC-2023 populations is 0.087, indicating moderate genetic differentiation (0.05<Fst<0.15). However, the Fst value between the YC-1993 and the other two populations is 0.151, indicating a high degree of genetic differentiation (0.15<Fst<0.25). Phylogenetic tree, principal component analysis, the kinship heat map and Admixture analysis further revealed that although there was a certain degree of genetic differentiation among the three populations, their genetic information originated from the same original ancestor. The morphometrical traits and genetic variations of Yuncheng Artemia may result from genetic selection and genetic drift caused by the environmental changes that Yuncheng Salt Lake has undergone in recent years, and unique aquaculture and harvest management. This study will provide theoretical support for the conservation and utilization of Artemia germplasm resources in Yuncheng Salt Lake.
Artemia is important live bait in the cultivation of marine fish and crustacean seedlings, with more than 90% derived from wild Artemia resources. In order to study the effects of environmental changes and the unique aquaculture and harvest management on the morphometrical and genetic characteristics of Artemia in Yuncheng Salt Lake, Shanxi Province in the past 30 years, Artemia cysts collected in 1993 (YC-1993), 2019 (YC-2019) and 2023 (YC-2023) from Yuncheng Salt Lake were cultured and morphometrical measurements were conducted. Specific-locus amplified fragments sequencing (SLAF-seq) was used for population genetics analysis. The results showed that the YC-2023 group was extremely significantly larger than the YC-1993 group in terms of body length, abdominal length, ovary width, interocular distance, eye diameter, second antenna length, and peripheral claspers, while the cyst diameter of the YC-2023 group was significantly smaller than that of the YC-1993 group. The results of genetic analysis showed that the YC-2023 group had the lowest genetic diversity. The polymorphism information content (PIC) of three populations was between 0.252 and 0.305, showing moderate polymorphism (0.25<PIC<0.5). The Fst value of the genetic differentiation coefficient between the YC-2019 and YC-2023 populations is 0.087, indicating moderate genetic differentiation (0.05<Fst<0.15). However, the Fst value between the YC-1993 and the other two populations is 0.151, indicating a high degree of genetic differentiation (0.15<Fst<0.25). Phylogenetic tree, principal component analysis, the kinship heat map and Admixture analysis further revealed that although there was a certain degree of genetic differentiation among the three populations, their genetic information originated from the same original ancestor. The morphometrical traits and genetic variations of Yuncheng Artemia may result from genetic selection and genetic drift caused by the environmental changes that Yuncheng Salt Lake has undergone in recent years, and unique aquaculture and harvest management. This study will provide theoretical support for the conservation and utilization of Artemia germplasm resources in Yuncheng Salt Lake.
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This study examines the mechanism of the unexpected absence of bottom hypoxia in the lower Pearl River Estuary during summer 2023 through integrated analysis of hydrological, biogeochemical and physical drivers. The Pear River discharge during 2023 summer was only 51% of the historical average summer average. This led to a 45% reduction in riverine nutrient fluxes and a sharp decline in marine-sourced organic carbon production. Persistent northeasterly downwelling-favorable winds during the 15 days preceding sampling weakened stratification (stratification factor of 0.074 ± 0.20 during 2023 cruise versus 0.14 ± 0.17, 0.38 ± 0.50 and 0.18 ± 0.20 during other three cruises of 2015, 2017 and 2018 when hypoxia occurred) enhanced vertical mixing and oxygen replenishment in the bottom water. The reduced river discharge also shortened the water residence time in the estuary to 1.8 days, compared to 3.1 days under average summer discharge conditions, thereby limiting the oxygen-depleting effect of organic matter degradation. The synergistic effect of these factors led to the absence of bottom-water hypoxia in the Pearl River Estuary in summer 2023. This study reveals the important regulating role of extreme hydro-meteorological conditions in the formation of estuarine hypoxia.
This study examines the mechanism of the unexpected absence of bottom hypoxia in the lower Pearl River Estuary during summer 2023 through integrated analysis of hydrological, biogeochemical and physical drivers. The Pear River discharge during 2023 summer was only 51% of the historical average summer average. This led to a 45% reduction in riverine nutrient fluxes and a sharp decline in marine-sourced organic carbon production. Persistent northeasterly downwelling-favorable winds during the 15 days preceding sampling weakened stratification (stratification factor of 0.074 ± 0.20 during 2023 cruise versus 0.14 ± 0.17, 0.38 ± 0.50 and 0.18 ± 0.20 during other three cruises of 2015, 2017 and 2018 when hypoxia occurred) enhanced vertical mixing and oxygen replenishment in the bottom water. The reduced river discharge also shortened the water residence time in the estuary to 1.8 days, compared to 3.1 days under average summer discharge conditions, thereby limiting the oxygen-depleting effect of organic matter degradation. The synergistic effect of these factors led to the absence of bottom-water hypoxia in the Pearl River Estuary in summer 2023. This study reveals the important regulating role of extreme hydro-meteorological conditions in the formation of estuarine hypoxia.
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Abstract:
The Miaodao Archipelago in Shandong Province are rich in seaweed resources and hold great potential for nearshore marine carbon sinks. However, fundamental data and research related to the seaweed beds in this region remain scarce, which astricts the calculation and evaluation to carbon sink of seaweed beds. Therefore, this study aimed to complement the gap in baseline information regarding seaweed beds in the Miaodao Archipelago. In this study, 10 residential islands of Miaodao archipelago in Shandong Province were selected and the distribution of seaweed fields in the subtidal zone was investigated and sampled by scuba diving. Seaweed resource information in the seaweed beds, including the distribution and area of seaweed beds, species composition, biomass, dominant species, and community diversity, was identified and counted, and then combined with the environmental context, the community structure characteristics of the seaweed beds in the 10 islands were clustered. A total of 34 species of macroalgae were collected, belonging to 21 families and 25 genera. Among them were 18 species of red algae (11 families, 15 genera), 4 species of green algae (2 families, 2 genera), and 12 species of brown algae (8 families, 8 genera). The dominant macroalgal species in the region included Saccharina japonica, Undaria pinnatifida, Sargassum muticum, Gelidium amansii, Chondrus nipponicus, Ulva lactuca, Dictyopteris divaricata, Sargassum pallidum, and Desmarestia viridis. The results of statistical analysis revealed that Tuoji Island and Xiaoqin Island had relatively high biomass density. Nouth Changshan Island exhibited the highest species richness, followed by Miao Island and South Huangcheng Island. South Huangcheng Island had the highest diversity index, with Nouth Changshan Island and Tuoji Island ranking next, and also showed the highest evenness index among the surveyed sites. Cluster analysis results indicated significant differences in community structure between the five southern islands (South Changshan Island, North Changshan Island, Miao Island, Daheishan Island, Xiaoheishan Island) and the five northern islands (Tuoji Island, Daqin Island, Xiaoqin Island, South Huangcheng Island, North Huangcheng Island), mainly due to geographic variation. This study helps complement the gap in baseline information regarding seaweed beds in Shandong Province, thus providing essential data for the carbon sink evaluation and theoretical support for development of nearshore blue carbon sink of seaweed beds in Shandong Province.
The Miaodao Archipelago in Shandong Province are rich in seaweed resources and hold great potential for nearshore marine carbon sinks. However, fundamental data and research related to the seaweed beds in this region remain scarce, which astricts the calculation and evaluation to carbon sink of seaweed beds. Therefore, this study aimed to complement the gap in baseline information regarding seaweed beds in the Miaodao Archipelago. In this study, 10 residential islands of Miaodao archipelago in Shandong Province were selected and the distribution of seaweed fields in the subtidal zone was investigated and sampled by scuba diving. Seaweed resource information in the seaweed beds, including the distribution and area of seaweed beds, species composition, biomass, dominant species, and community diversity, was identified and counted, and then combined with the environmental context, the community structure characteristics of the seaweed beds in the 10 islands were clustered. A total of 34 species of macroalgae were collected, belonging to 21 families and 25 genera. Among them were 18 species of red algae (11 families, 15 genera), 4 species of green algae (2 families, 2 genera), and 12 species of brown algae (8 families, 8 genera). The dominant macroalgal species in the region included Saccharina japonica, Undaria pinnatifida, Sargassum muticum, Gelidium amansii, Chondrus nipponicus, Ulva lactuca, Dictyopteris divaricata, Sargassum pallidum, and Desmarestia viridis. The results of statistical analysis revealed that Tuoji Island and Xiaoqin Island had relatively high biomass density. Nouth Changshan Island exhibited the highest species richness, followed by Miao Island and South Huangcheng Island. South Huangcheng Island had the highest diversity index, with Nouth Changshan Island and Tuoji Island ranking next, and also showed the highest evenness index among the surveyed sites. Cluster analysis results indicated significant differences in community structure between the five southern islands (South Changshan Island, North Changshan Island, Miao Island, Daheishan Island, Xiaoheishan Island) and the five northern islands (Tuoji Island, Daqin Island, Xiaoqin Island, South Huangcheng Island, North Huangcheng Island), mainly due to geographic variation. This study helps complement the gap in baseline information regarding seaweed beds in Shandong Province, thus providing essential data for the carbon sink evaluation and theoretical support for development of nearshore blue carbon sink of seaweed beds in Shandong Province.
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Abstract:
Taking the Caofeidian seagrass bed—the largest existing seagrass bed in China—as the research object, this study adopted a combined method of remote sensing interpretation, field investigation, and model analysis to carry out research on the quantitative zoning of density and the formation mechanism of spatial heterogeneity of the Caofeidian seagrass bed. Through the interpretation of high-resolution satellite remote sensing images and combined with on-site field verification, the quantitative data of three core zoning types under the spatial pattern of “dense in the north and sparse in the south” of the Caofeidian seagrass bed were obtained, namely the dense area (with an area of 7.31 km2, accounting for 18.34%), the moderately dense area (with an area of 10.36 km2, accounting for 26.00%), and the sparse area (with an area of 22.18 km2, accounting for 55.66%). On the whole, it shows the characteristics of patchy mosaic distribution. Based on 10 environmental data items (including illumination, ammonium, and sediment density) obtained from field investigations, an MLP-ANN (Multilayer Perceptron-Artificial Neural Network) model was used for analysis, and it was found that the internal friction angle of sediment (contribution: 18%), water temperature (contribution: 15%), and sediment phosphate (contribution: 15%) were the core driving factors affecting the density zoning of the seagrass bed, with a cumulative influence accounting for 48%. The research results indicated that the density zoning of the Caofeidian seagrass bed is formed by thejoint effect of natural dynamic factors and human activities: in the southern region, strong tidal currents cause sediment scouring, and superimposed on the impacts of engineering activities such as oilfield exploration and channel dredging, as well as land-based pollution, forming the degradation chain of “sediment disturbance - nutrient imbalance”; the northern region is far from these disturbance sources, and through ecological restoration, the sediment conditions have been optimized, thus providing support for the formation of the medium-to-high density seagrass bed areas. This study fills the gaps in the quantitative research on the density zoning of the Caofeidian seagrass bed and the research on its formation mechanism, and provides a scientific basis and technical paradigm for the scientific assessment and effective restoration of seagrass beds in the Bohai Bay.
Taking the Caofeidian seagrass bed—the largest existing seagrass bed in China—as the research object, this study adopted a combined method of remote sensing interpretation, field investigation, and model analysis to carry out research on the quantitative zoning of density and the formation mechanism of spatial heterogeneity of the Caofeidian seagrass bed. Through the interpretation of high-resolution satellite remote sensing images and combined with on-site field verification, the quantitative data of three core zoning types under the spatial pattern of “dense in the north and sparse in the south” of the Caofeidian seagrass bed were obtained, namely the dense area (with an area of 7.31 km2, accounting for 18.34%), the moderately dense area (with an area of 10.36 km2, accounting for 26.00%), and the sparse area (with an area of 22.18 km2, accounting for 55.66%). On the whole, it shows the characteristics of patchy mosaic distribution. Based on 10 environmental data items (including illumination, ammonium, and sediment density) obtained from field investigations, an MLP-ANN (Multilayer Perceptron-Artificial Neural Network) model was used for analysis, and it was found that the internal friction angle of sediment (contribution: 18%), water temperature (contribution: 15%), and sediment phosphate (contribution: 15%) were the core driving factors affecting the density zoning of the seagrass bed, with a cumulative influence accounting for 48%. The research results indicated that the density zoning of the Caofeidian seagrass bed is formed by thejoint effect of natural dynamic factors and human activities: in the southern region, strong tidal currents cause sediment scouring, and superimposed on the impacts of engineering activities such as oilfield exploration and channel dredging, as well as land-based pollution, forming the degradation chain of “sediment disturbance - nutrient imbalance”; the northern region is far from these disturbance sources, and through ecological restoration, the sediment conditions have been optimized, thus providing support for the formation of the medium-to-high density seagrass bed areas. This study fills the gaps in the quantitative research on the density zoning of the Caofeidian seagrass bed and the research on its formation mechanism, and provides a scientific basis and technical paradigm for the scientific assessment and effective restoration of seagrass beds in the Bohai Bay.
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Abstract:
Toxic algal species pose significant threats to ecological environmental safety and human health. Azadinium dexteroporum, one of the main producers of azaspiracid toxins, remains poorly studied in China, and its distribution in Chinese coastal waters is still unclear. In this study, environmental DNA (eDNA) methods were used to obtain occurrence records of A. dexteroporum in Chinese coastal areas. Using the 2050s and 2100s as future projection periods, the Maximum Entropy (MaxEnt)model was applied to simulate the potential suitable habitats of this species under current and three future climate scenarios (SSP126, SSP245, and SSP585). The results indicated that nitrate concentration, silicate concentration, and sea surface temperature were the primary environmental factors influencing the distribution of A. dexteroporum. Under current conditions, the suitable habitat area was estimated to be 63.71 × 104 km2, mainly concentrated in the northern South China Sea. With climate change, the potential suitable area of A. dexteroporum is projected to shrink, decreasing to 5.58×104 km2～32.21×104 km2 by the 2100s. The spatial distribution pattern of suitable habitats shows an overall “southward contraction and northward expansion” trend: the extensive suitable areas in the South China Sea are expected to disappear, while new suitable areas may emerge in the Yellow and Bohai Seas. The centroid of suitable habitats is projected to shift up to 1,439 km, migrating from the northern South China Sea to north of the Yangtze River estuary. These findings provide important scientific insights for the ecological risk monitoring, forecasting, and management of harmful dinoflagellates.
Toxic algal species pose significant threats to ecological environmental safety and human health. Azadinium dexteroporum, one of the main producers of azaspiracid toxins, remains poorly studied in China, and its distribution in Chinese coastal waters is still unclear. In this study, environmental DNA (eDNA) methods were used to obtain occurrence records of A. dexteroporum in Chinese coastal areas. Using the 2050s and 2100s as future projection periods, the Maximum Entropy (MaxEnt)model was applied to simulate the potential suitable habitats of this species under current and three future climate scenarios (SSP126, SSP245, and SSP585). The results indicated that nitrate concentration, silicate concentration, and sea surface temperature were the primary environmental factors influencing the distribution of A. dexteroporum. Under current conditions, the suitable habitat area was estimated to be 63.71 × 104 km2, mainly concentrated in the northern South China Sea. With climate change, the potential suitable area of A. dexteroporum is projected to shrink, decreasing to 5.58×104 km2～32.21×104 km2 by the 2100s. The spatial distribution pattern of suitable habitats shows an overall “southward contraction and northward expansion” trend: the extensive suitable areas in the South China Sea are expected to disappear, while new suitable areas may emerge in the Yellow and Bohai Seas. The centroid of suitable habitats is projected to shift up to 1,439 km, migrating from the northern South China Sea to north of the Yangtze River estuary. These findings provide important scientific insights for the ecological risk monitoring, forecasting, and management of harmful dinoflagellates.
, Available online , doi: 10.12284/hyxb2025006
Abstract:
Studying the occurrence and dynamics of microplastics on coastal beaches is crucial for the integrated management of coastal zones and the assessment of ecological risks. Previous research has highlighted that physical processes play a pivotal role in influencing the occurrences of microplastic on coastal beaches. However, the impact of extreme meteorological events such as typhoons on the distribution of microplastic pollution has yet to be explored. This study conducted field fixed-plot experiments on the coastal beaches of Xiamen City before and after Typhoon "Haikui" to analyze the variations in the abundance, composition, and diversity of microplastic on beaches. The results showed that the abundance of microplastics on the beaches in Xiamen City before Typhoon Haikui was (251.5 ± 27.9) n/kg, and this value significantly decreased to (127.0 ± 18.8) n/kg post-typhoon. Before and after the typhoon, the composition of microplastics on the beaches showed distinct variations, with the abundance of microplastics of different shapes and sizes responding differently to the typhoon. In particular, the abundance of smaller particles (<500 μm) significantly decreased, while the proportion of fibrous particles increased. Moreover, the typhoon event led to a general decrease in the Shannon-Wiener diversity index, while an increase in the Pielou’s evenness index. The impact of typhoons on the distribution of microplastics on beaches arises from the complex coupling of multiple dynamic physical processes in extreme weather, and it is also closely related to factors such as the location and substrate conditions of the coasts. To achieve simulation and prediction of the dynamics of microplastic pollution during typhoon processes, systematic and comprehensive research on the relevant mechanisms is still required in the future.
Studying the occurrence and dynamics of microplastics on coastal beaches is crucial for the integrated management of coastal zones and the assessment of ecological risks. Previous research has highlighted that physical processes play a pivotal role in influencing the occurrences of microplastic on coastal beaches. However, the impact of extreme meteorological events such as typhoons on the distribution of microplastic pollution has yet to be explored. This study conducted field fixed-plot experiments on the coastal beaches of Xiamen City before and after Typhoon "Haikui" to analyze the variations in the abundance, composition, and diversity of microplastic on beaches. The results showed that the abundance of microplastics on the beaches in Xiamen City before Typhoon Haikui was (251.5 ± 27.9) n/kg, and this value significantly decreased to (127.0 ± 18.8) n/kg post-typhoon. Before and after the typhoon, the composition of microplastics on the beaches showed distinct variations, with the abundance of microplastics of different shapes and sizes responding differently to the typhoon. In particular, the abundance of smaller particles (<500 μm) significantly decreased, while the proportion of fibrous particles increased. Moreover, the typhoon event led to a general decrease in the Shannon-Wiener diversity index, while an increase in the Pielou’s evenness index. The impact of typhoons on the distribution of microplastics on beaches arises from the complex coupling of multiple dynamic physical processes in extreme weather, and it is also closely related to factors such as the location and substrate conditions of the coasts. To achieve simulation and prediction of the dynamics of microplastic pollution during typhoon processes, systematic and comprehensive research on the relevant mechanisms is still required in the future.
, Available online
Abstract:
This study focuses on the physical process of a sea fog event during Typhoon Lekima in the Northern Yellow Sea by using observation data, reanalysis data and backward trajectory model. The analysis indicates that the typhoon circulation was the decisive factor determining whether fog formed offshore and developed inland. The warm and humid southerlies from the south Yellow Sea condensed into fog on the colder sea surface besides the typhoon center, which not only provided sufficient moisture for the formation and development of the sea fog but also formed a significant inversion layer over the fog area with the downdraft in the center of the typhoon. The "stable up and turbulent down" structure in the atmospheric boundary layer improved the development of sea fog on the coast and inland area. However, the horizontal wind steering and the strengthening wind speed behind the typhoon strengthened the wind shear in the atmospheric boundary layer, resulting in the enhanced turbulent mixing and the decrease of the stability in the bottom atmospheric boundary layer, which was the main cause of the fog dissipation.
This study focuses on the physical process of a sea fog event during Typhoon Lekima in the Northern Yellow Sea by using observation data, reanalysis data and backward trajectory model. The analysis indicates that the typhoon circulation was the decisive factor determining whether fog formed offshore and developed inland. The warm and humid southerlies from the south Yellow Sea condensed into fog on the colder sea surface besides the typhoon center, which not only provided sufficient moisture for the formation and development of the sea fog but also formed a significant inversion layer over the fog area with the downdraft in the center of the typhoon. The "stable up and turbulent down" structure in the atmospheric boundary layer improved the development of sea fog on the coast and inland area. However, the horizontal wind steering and the strengthening wind speed behind the typhoon strengthened the wind shear in the atmospheric boundary layer, resulting in the enhanced turbulent mixing and the decrease of the stability in the bottom atmospheric boundary layer, which was the main cause of the fog dissipation.
, Available online
Abstract:
The possibility of the Indonesian submarine wreck on 20 April 2021 was analyzed based on satellite remote sensing observation and numerical simulation. The results indicate that large-amplitude oceanic internal waves, estimated to be approximately 50 m using satellite images, originate from the Lombok Strait. They are widely distributed to the north of the Bali Island and are suggested to cause an abrupt sinking of the Indonesian submarine.
The possibility of the Indonesian submarine wreck on 20 April 2021 was analyzed based on satellite remote sensing observation and numerical simulation. The results indicate that large-amplitude oceanic internal waves, estimated to be approximately 50 m using satellite images, originate from the Lombok Strait. They are widely distributed to the north of the Bali Island and are suggested to cause an abrupt sinking of the Indonesian submarine.
, Available online
Abstract:
Abstract：The potential fish production was controlled largely by ocean primary production (OPP) and there were a lot of research findings of estimating fish production by using OPP in China. The relationships between the biomass of fishery stock and OPP were often complicated by the varieties of trophic control in the ecosystem. In this paper, we examined the relationship between biomass of chub mackerel (Scomber japonicus) and net primary production (NPP) and discussed mechanism of trophic control in the ecosystem of chub mackerel fishing ground in south East China Sea by using catch and effort data from the large purse sense of China fishery and NPP derived from remote sensing. The results showed there was a significant non-linear relationship between NPP and standardized CPUE (Catch Per Unit Effort) (P<0.05) instead of the linear trend. The non-linear relationship could be described by a reversed parabolic curve, which meant the biomass of chub mackerel increased with NPP and then decreased when the NPP exceeded a point. The results implied there were other trophic controls in addition to bottom-up control occurred in the ecosystem in south East China Sea. We speculated the change of abundance of the key species at intermediate trophic levels or/and interspecific competitions contribute to the relationship.
Abstract：The potential fish production was controlled largely by ocean primary production (OPP) and there were a lot of research findings of estimating fish production by using OPP in China. The relationships between the biomass of fishery stock and OPP were often complicated by the varieties of trophic control in the ecosystem. In this paper, we examined the relationship between biomass of chub mackerel (Scomber japonicus) and net primary production (NPP) and discussed mechanism of trophic control in the ecosystem of chub mackerel fishing ground in south East China Sea by using catch and effort data from the large purse sense of China fishery and NPP derived from remote sensing. The results showed there was a significant non-linear relationship between NPP and standardized CPUE (Catch Per Unit Effort) (P<0.05) instead of the linear trend. The non-linear relationship could be described by a reversed parabolic curve, which meant the biomass of chub mackerel increased with NPP and then decreased when the NPP exceeded a point. The results implied there were other trophic controls in addition to bottom-up control occurred in the ecosystem in south East China Sea. We speculated the change of abundance of the key species at intermediate trophic levels or/and interspecific competitions contribute to the relationship.
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