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2025, 47(3): 1-12.
doi: 10.12284/hyxb2025019
Abstract:
Based on the hydrographic observations carried out in the austral summer during 2013 and 2015 from the continental shelf to the front regions of Vincennes Bay, East Antarctica, this study utilizes an optimum multiparameter analysis method to evaluate the export pathway of Vincennes Bay Bottom Water (VBBW) and its contribution rate to Antarctic bottom water (AABW). The results show that the freshest, coldest, and most oxygen-rich bottom water is distributed above the northwestern ridge of Vincennes Bay. The highest proportion of local Dense Shelf Water (DSW) on the bottom over this ridge was (28.58 ± 1.75)%, which exceeded the proportion observed at all other stations on the offshore side of the continental slope. The VBBW, a mixture of local DSW and modified Circumpolar Deep Water, was also maximized in the AABW layer on this northwestern ridge. The results suggest that topography plays an important role in guiding the outflow of local DSW and even VBBW, and the northwestern ridge could be the main pathway for VBBW export. In the vertical direction, the proportion of DSW decreases with the shallower depth at most stations, but patchy DSW contribution layers were commonly observed in the sub-bottom layers, which means that the proportion of DSW increases in some depth ranges. According to the anomaly distribution of seawater characteristics on the density surfaces, the DSW in the sub-bottom layers can also be exported along the isopycnals, manifested as thermohaline intrusion patches. These thermohaline intrusion patches have significantly colder, fresher, and oxygen-rich characteristics, which may contribute to the enhancement of sub-bottom ventilation. In addition, VBBW can reach the bottom of the Australia-Antarctic basin at depths deeper than4000 m but with a limited contribution rate, no more than 17%, and is mainly contributed by mCDW. This study helps understand the export pathway and contribution of bottom water from the medium bay to the bottom layer of the Australia-Antarctic Basin. It provides a reference for further study on the formation and modification of the AABW in this basin.
Based on the hydrographic observations carried out in the austral summer during 2013 and 2015 from the continental shelf to the front regions of Vincennes Bay, East Antarctica, this study utilizes an optimum multiparameter analysis method to evaluate the export pathway of Vincennes Bay Bottom Water (VBBW) and its contribution rate to Antarctic bottom water (AABW). The results show that the freshest, coldest, and most oxygen-rich bottom water is distributed above the northwestern ridge of Vincennes Bay. The highest proportion of local Dense Shelf Water (DSW) on the bottom over this ridge was (28.58 ± 1.75)%, which exceeded the proportion observed at all other stations on the offshore side of the continental slope. The VBBW, a mixture of local DSW and modified Circumpolar Deep Water, was also maximized in the AABW layer on this northwestern ridge. The results suggest that topography plays an important role in guiding the outflow of local DSW and even VBBW, and the northwestern ridge could be the main pathway for VBBW export. In the vertical direction, the proportion of DSW decreases with the shallower depth at most stations, but patchy DSW contribution layers were commonly observed in the sub-bottom layers, which means that the proportion of DSW increases in some depth ranges. According to the anomaly distribution of seawater characteristics on the density surfaces, the DSW in the sub-bottom layers can also be exported along the isopycnals, manifested as thermohaline intrusion patches. These thermohaline intrusion patches have significantly colder, fresher, and oxygen-rich characteristics, which may contribute to the enhancement of sub-bottom ventilation. In addition, VBBW can reach the bottom of the Australia-Antarctic basin at depths deeper than
2025, 47(3): 13-26.
doi: 10.12284/hyxb2025032
Abstract:
Based on observations in the Bohai Sea (BS) and North Yellow Sea (NYS) obtained during the late summer and early autumn of 2021, the hypoxic characteristics and influencing factors were explored by analyzing the spatial patterns of temperature, salinity, density, dissolved oxygen (DO) and nutrients, revealing the regulation mechanisms of hydro-biogeochemical processes on the distributions of DO and hypoxia. A narrow hypoxic zone (with the minimum DO mass concentration of 2.18 mg/L) in a southwest-northeast orientation, which was characterized by a high apparent oxygen consumption (AOU) (＞4 mg/L), was observed within the bottom cold water-dominated region in the western BS; a low-DO area with a small scope existed in the northeastern region off the Bohai Bay mouth at 10-m layer. DO concentrations in the NYS were overall higher than that in the BS, and a relatively high DO level was maintained within the Bottom Cold Water Mass (BCWM) in the central NYS, although there was a high AOU (＞2.5 mg/L). The low-lying topography and higher stratification intensity within the bottom cold water-dominated region in the western BS provided the basis for the formation and maintenance of bottom hypoxia, and the fronts around this cold water significantly controlled the boundary and extension scope of the hypoxic zone. The low-DO area at 10-m layer in the northeastern region off the Bohai Bay mouth was caused by the uplift of the hypoxic cold water from the bottom. The presence of an anticyclonic eddy in the shallow bank of the central BS led to the formation of a DO-rich water (＞6 mg/L) at bottom. The decomposition of organic matter and related oxygen consumption in the context of stratification was an important material basis for the formation of hypoxia in the western BS, exactly corresponding to a high-nutrient area at bottom layer. In contrast, due to the higher background levels of DO within the BCWM and the lower AOU than that in the bottom layer of the western BS, it was difficult to form hypoxia in the central NYS even under the relatively high stratification strength; moreover, the deeper water depth was another factor responsible for this situation. This study could provide a scientific basis for understanding the multi-scale variations and regulation of DO in the BS and the NYS, laying a foundation for the subsequent refined simulation and prediction of hypoxia in this sea area.
Based on observations in the Bohai Sea (BS) and North Yellow Sea (NYS) obtained during the late summer and early autumn of 2021, the hypoxic characteristics and influencing factors were explored by analyzing the spatial patterns of temperature, salinity, density, dissolved oxygen (DO) and nutrients, revealing the regulation mechanisms of hydro-biogeochemical processes on the distributions of DO and hypoxia. A narrow hypoxic zone (with the minimum DO mass concentration of 2.18 mg/L) in a southwest-northeast orientation, which was characterized by a high apparent oxygen consumption (AOU) (＞4 mg/L), was observed within the bottom cold water-dominated region in the western BS; a low-DO area with a small scope existed in the northeastern region off the Bohai Bay mouth at 10-m layer. DO concentrations in the NYS were overall higher than that in the BS, and a relatively high DO level was maintained within the Bottom Cold Water Mass (BCWM) in the central NYS, although there was a high AOU (＞2.5 mg/L). The low-lying topography and higher stratification intensity within the bottom cold water-dominated region in the western BS provided the basis for the formation and maintenance of bottom hypoxia, and the fronts around this cold water significantly controlled the boundary and extension scope of the hypoxic zone. The low-DO area at 10-m layer in the northeastern region off the Bohai Bay mouth was caused by the uplift of the hypoxic cold water from the bottom. The presence of an anticyclonic eddy in the shallow bank of the central BS led to the formation of a DO-rich water (＞6 mg/L) at bottom. The decomposition of organic matter and related oxygen consumption in the context of stratification was an important material basis for the formation of hypoxia in the western BS, exactly corresponding to a high-nutrient area at bottom layer. In contrast, due to the higher background levels of DO within the BCWM and the lower AOU than that in the bottom layer of the western BS, it was difficult to form hypoxia in the central NYS even under the relatively high stratification strength; moreover, the deeper water depth was another factor responsible for this situation. This study could provide a scientific basis for understanding the multi-scale variations and regulation of DO in the BS and the NYS, laying a foundation for the subsequent refined simulation and prediction of hypoxia in this sea area.
2025, 47(3): 27-38.
doi: 10.12284/hyxb2025006
Abstract:
The dynamics of microplastic pollution in coastal zones, in the context of climate change, is a crucial global environmental issue. This study investigated and analyzed changes in microplastic abundance, composition, and diversity in beach sediments in Xiamen City before and after Typhoon Haikui. The results showed that the abundance of microplastics on the beaches in Xiamen City before Typhoon Haikui was (251.5 ± 27.9) n/kg, which significantly decreased to (127.0 ± 18.8) n/kg post-typhoon. Before and after the typhoon, the composition of microplastics on the beaches exhibited distinct variations. 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 the Pielou’s evenness index increased. Based on the results of this study and previous research, it is concluded that heavy rainfall is the driving factor behind the changes in microplastic abundance and composition on Xiamen’s beaches caused by Typhoon Haikui. The impact of typhoons on the dynamics of microplastic pollution in coastal zones results from the coupling of multiple physical processes, influenced by a complex combination of factors, such as dynamic conditions, sediment physical and chemical factors, and topography. In the future, it will be necessary to conduct long-term monitoring of hydrological and meteorological data, and to carry out more in-depth, systematic, and comprehensive research on the underlying mechanisms.
The dynamics of microplastic pollution in coastal zones, in the context of climate change, is a crucial global environmental issue. This study investigated and analyzed changes in microplastic abundance, composition, and diversity in beach sediments in Xiamen City before and after Typhoon Haikui. The results showed that the abundance of microplastics on the beaches in Xiamen City before Typhoon Haikui was (251.5 ± 27.9) n/kg, which significantly decreased to (127.0 ± 18.8) n/kg post-typhoon. Before and after the typhoon, the composition of microplastics on the beaches exhibited distinct variations. 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 the Pielou’s evenness index increased. Based on the results of this study and previous research, it is concluded that heavy rainfall is the driving factor behind the changes in microplastic abundance and composition on Xiamen’s beaches caused by Typhoon Haikui. The impact of typhoons on the dynamics of microplastic pollution in coastal zones results from the coupling of multiple physical processes, influenced by a complex combination of factors, such as dynamic conditions, sediment physical and chemical factors, and topography. In the future, it will be necessary to conduct long-term monitoring of hydrological and meteorological data, and to carry out more in-depth, systematic, and comprehensive research on the underlying mechanisms.
2025, 47(3): 39-50.
doi: 10.12284/hyxb2025044
Abstract:
Typhoons, as one of the common natural disasters in coastal zones, have severe impacts on tidal flats. However, there is a significant lack of field data on typhoons, and studies on how salt marsh vegetation protects tidal flats during typhoon events are still very limited. This study selected Chongming Dongtan in the Changjiang River Estuary as the research site. During the passage of Typhoon In-Fa in July 2021, hydrodynamic instruments and UAV photogrammetry (elevation measurements) were used to monitor hydrodynamics and sediment in both salt marsh and the marsh front areas, as well as to monitor the salt marsh ecosystem before and after the typhoon. The findings are as follows: (1) During the typhoon, wind speed, water depth, and wave height were 1.1−2.8 times those before and after the typhoon, and the hydrodynamic forces in the marsh front area were higher than those in the salt marsh area, with water depth, wave height, and flow velocity being 1.3 times, 1.2 times, and 1.9 times those of the salt marsh area, respectively. (2) Under the influence of Typhoon In-Fa, vegetation patches at the marsh front, directly exposed to strong winds and waves, experienced hydrodynamic forces such as water depth and wave height that were 1.1−1.9 times those of the salt marsh area, resulting in erosion at the marsh front being 1.2−1.8 times that of the inland vegetation patches under the same vegetation coverage conditions. (3) In the marsh-front area, densely vegetated patches demonstrated stronger sediment accretion capacity compared to sparsely vegetated patches, with the maximum accretion thickness in densely vegetated areas reaching 45 cm, whereas sparse patches were mainly subject to erosion, with a maximum erosion depth of 17 cm. This indicates that the density of vegetation patches directly affects the sedimentation and erosion dynamics of the tidal flat. This study reveals that the arrangement and location of vegetation patches are crucial to the sedimentation and erosion of tidal flats under extreme weather events, which has significant implications for tidal flat management and ecological protection. It also provides theoretical support for establishing a robust natural barrier in response to extreme weather conditions.
Typhoons, as one of the common natural disasters in coastal zones, have severe impacts on tidal flats. However, there is a significant lack of field data on typhoons, and studies on how salt marsh vegetation protects tidal flats during typhoon events are still very limited. This study selected Chongming Dongtan in the Changjiang River Estuary as the research site. During the passage of Typhoon In-Fa in July 2021, hydrodynamic instruments and UAV photogrammetry (elevation measurements) were used to monitor hydrodynamics and sediment in both salt marsh and the marsh front areas, as well as to monitor the salt marsh ecosystem before and after the typhoon. The findings are as follows: (1) During the typhoon, wind speed, water depth, and wave height were 1.1−2.8 times those before and after the typhoon, and the hydrodynamic forces in the marsh front area were higher than those in the salt marsh area, with water depth, wave height, and flow velocity being 1.3 times, 1.2 times, and 1.9 times those of the salt marsh area, respectively. (2) Under the influence of Typhoon In-Fa, vegetation patches at the marsh front, directly exposed to strong winds and waves, experienced hydrodynamic forces such as water depth and wave height that were 1.1−1.9 times those of the salt marsh area, resulting in erosion at the marsh front being 1.2−1.8 times that of the inland vegetation patches under the same vegetation coverage conditions. (3) In the marsh-front area, densely vegetated patches demonstrated stronger sediment accretion capacity compared to sparsely vegetated patches, with the maximum accretion thickness in densely vegetated areas reaching 45 cm, whereas sparse patches were mainly subject to erosion, with a maximum erosion depth of 17 cm. This indicates that the density of vegetation patches directly affects the sedimentation and erosion dynamics of the tidal flat. This study reveals that the arrangement and location of vegetation patches are crucial to the sedimentation and erosion of tidal flats under extreme weather events, which has significant implications for tidal flat management and ecological protection. It also provides theoretical support for establishing a robust natural barrier in response to extreme weather conditions.
2025, 47(3): 51-61.
doi: 10.12284/hyxb2025034
Abstract:
Mangroves represent the most productive ecosystem along the coastline. The mangrove forest is a source of diverse organic carbon, which contributes to the complexity of the trophic structure of the benthic food web. This study employed the benthic animals in the mangroves along Yanpu Bay as the research object, analysing the community trophic structure and determining the potential food sources through the utilisation of the stable isotope technique in conjunction with the Stable Isotope Bayesian Ellipses (SIBER) model and the Stable Isotope Mixing Models (Simmr). The study demonstrated that the carbon stable isotope (δ13C) values of benthic animals ranged from −22.04‰ to −11.27‰, while the nitrogen stable isotope (δ15N) values ranged the trophic levels ranged from 1.33 (Cerithidea rhizophorarum) to 3.95 (Periophthalmus cantonensis), with carbon stable isotope (δ13C) values from 5.86‰ to 16.21‰. The trophic level of fish is relatively high, ranging from 2.38 to 3.95, while that of crustaceans is 2.61 to 3.52. In contrast, the trophic level of mollusc is relatively low, ranging from 1.33 to 3.15. These differences are related to the feeding preferences of the different groups. The analysis of the nutritional structure indicates that the length of the food chain and the nutritional diversity of fish are greater than those of crustaceans and mollusc. The diversity of food sources and nutritional uniformity of crustaceans are the highest, while the nutritional diversity and similarity of mollusc are the highest. Overall, there is a varying degree of overlap between the core nutritional niches of fish, crustaceans and mollusc. An analysis of the potential food sources of benthic animals based on a Simmr mixed model revealed that SOM was the primary carbon source, accounting for 78.2% of the total, followed by phytoplankton, which constituted 21.6% of the total, while litter and POM represented the lowest proportions, at 3.7% and 3.3%, respectively. The findings of this study enhance our comprehension of the trophic relationships of benthic animals in mangrove ecosystems along the northern coast of China. They will facilitate more effective conservation and restoration of mangrove biodiversity from a trophic regulation perspective.
Mangroves represent the most productive ecosystem along the coastline. The mangrove forest is a source of diverse organic carbon, which contributes to the complexity of the trophic structure of the benthic food web. This study employed the benthic animals in the mangroves along Yanpu Bay as the research object, analysing the community trophic structure and determining the potential food sources through the utilisation of the stable isotope technique in conjunction with the Stable Isotope Bayesian Ellipses (SIBER) model and the Stable Isotope Mixing Models (Simmr). The study demonstrated that the carbon stable isotope (δ13C) values of benthic animals ranged from −22.04‰ to −11.27‰, while the nitrogen stable isotope (δ15N) values ranged the trophic levels ranged from 1.33 (Cerithidea rhizophorarum) to 3.95 (Periophthalmus cantonensis), with carbon stable isotope (δ13C) values from 5.86‰ to 16.21‰. The trophic level of fish is relatively high, ranging from 2.38 to 3.95, while that of crustaceans is 2.61 to 3.52. In contrast, the trophic level of mollusc is relatively low, ranging from 1.33 to 3.15. These differences are related to the feeding preferences of the different groups. The analysis of the nutritional structure indicates that the length of the food chain and the nutritional diversity of fish are greater than those of crustaceans and mollusc. The diversity of food sources and nutritional uniformity of crustaceans are the highest, while the nutritional diversity and similarity of mollusc are the highest. Overall, there is a varying degree of overlap between the core nutritional niches of fish, crustaceans and mollusc. An analysis of the potential food sources of benthic animals based on a Simmr mixed model revealed that SOM was the primary carbon source, accounting for 78.2% of the total, followed by phytoplankton, which constituted 21.6% of the total, while litter and POM represented the lowest proportions, at 3.7% and 3.3%, respectively. The findings of this study enhance our comprehension of the trophic relationships of benthic animals in mangrove ecosystems along the northern coast of China. They will facilitate more effective conservation and restoration of mangrove biodiversity from a trophic regulation perspective.
2025, 47(3): 62-72.
doi: 10.12284/hyxb2025038
Abstract:
To investigate the survival, growth, and physiological responses of Zostera marina transplants to different water velocities and determine the optimal flow velocity range, an experiment was conducted. The study aimed to elucidate the effects of water velocity on Z. marina transplants by measuring and evaluating their survival rates, growth performance, and physiological indicators, as well as examining the interrelationships among these factors. Results indicated that the survival rate of transplanted Z. marina plants peaked at 0.4 m/s, being 1.1−2.4 times higher than those in the other treatments (P < 0.05). Notably, all plants in the control group perished. Aboveground tissue growth decreased progressively with increasing water velocity, while belowground tissue growth increased gradually. Specifically, leaf elongation rate at 1 m/s was 24.0% lower compared to 0.2 m/s, whereas belowground dry weight at 0.4 m/s was 1.6 times higher than that at 0.2 m/s. Photosynthetic pigment and nonstructural carbohydrates contents in leaves reached their lowest levels between 0.4 and 0.6 m/s, decreasing by 0.8% to 18.5% relative to other treatments. Considering the survival and growth comprehensive income index and physiological index stability coefficient, the suitable flow velocity range for Z. marina transplants is 0.3 to 0.8 m/s, with an optimal range of 0.4 to 0.6 m/s. These findings suggest that moderately increasing water flow velocity can facilitate the rapid establishment and expansion of Z. marina transplants.
To investigate the survival, growth, and physiological responses of Zostera marina transplants to different water velocities and determine the optimal flow velocity range, an experiment was conducted. The study aimed to elucidate the effects of water velocity on Z. marina transplants by measuring and evaluating their survival rates, growth performance, and physiological indicators, as well as examining the interrelationships among these factors. Results indicated that the survival rate of transplanted Z. marina plants peaked at 0.4 m/s, being 1.1−2.4 times higher than those in the other treatments (P < 0.05). Notably, all plants in the control group perished. Aboveground tissue growth decreased progressively with increasing water velocity, while belowground tissue growth increased gradually. Specifically, leaf elongation rate at 1 m/s was 24.0% lower compared to 0.2 m/s, whereas belowground dry weight at 0.4 m/s was 1.6 times higher than that at 0.2 m/s. Photosynthetic pigment and nonstructural carbohydrates contents in leaves reached their lowest levels between 0.4 and 0.6 m/s, decreasing by 0.8% to 18.5% relative to other treatments. Considering the survival and growth comprehensive income index and physiological index stability coefficient, the suitable flow velocity range for Z. marina transplants is 0.3 to 0.8 m/s, with an optimal range of 0.4 to 0.6 m/s. These findings suggest that moderately increasing water flow velocity can facilitate the rapid establishment and expansion of Z. marina transplants.
2025, 47(3): 73-84.
doi: 10.12284/hyxb2025042
Abstract:
This study aimed to investigate the allelopathic effects of Sesuvium portulacastrum (Aizoaceae) on typical red tide algae and identify the sources of the active compounds. Three red tide algae species, Prorocentrum micans, Karenia mikimotoi, and Alexandrium catenella, were selected as test subjects. The planting water of the coastal salt-tolerant plant Sesuvium portulacastrum served as the research material. Root exudates from the plant were adsorbed using a C18 solid-phase extraction column and then extracted with methanol, ethyl acetate, dichloromethane, and n-hexane. The four extracts exhibited varying degrees of inhibition on the growth of the algae, with the dichloromethane extract showing the most significant inhibitory effect. At a concentration of 10 g/L, the inhibition rates for the three algae species were 50.83%, 97.30%, and 81.41%, respectively. Gas chromatography-mass spectrometry (GC-MS) analysis identified 19 fatty acids and their derivatives. Among these, stearic acid, oleamide, and docosanol exhibited algicidal activity, with docosanol showing the strongest effect. At a concentration of 2 mg/L, the inhibition rates for the three algae species were 90%, 100%, and 81.04%, respectively. These results indicate that Sesuvium portulacastrum can release fatty acids and their derivatives to inhibit the growth of red tide algae, demonstrating its potential as a plant-based tool for red tide control and environmental remediation.
This study aimed to investigate the allelopathic effects of Sesuvium portulacastrum (Aizoaceae) on typical red tide algae and identify the sources of the active compounds. Three red tide algae species, Prorocentrum micans, Karenia mikimotoi, and Alexandrium catenella, were selected as test subjects. The planting water of the coastal salt-tolerant plant Sesuvium portulacastrum served as the research material. Root exudates from the plant were adsorbed using a C18 solid-phase extraction column and then extracted with methanol, ethyl acetate, dichloromethane, and n-hexane. The four extracts exhibited varying degrees of inhibition on the growth of the algae, with the dichloromethane extract showing the most significant inhibitory effect. At a concentration of 10 g/L, the inhibition rates for the three algae species were 50.83%, 97.30%, and 81.41%, respectively. Gas chromatography-mass spectrometry (GC-MS) analysis identified 19 fatty acids and their derivatives. Among these, stearic acid, oleamide, and docosanol exhibited algicidal activity, with docosanol showing the strongest effect. At a concentration of 2 mg/L, the inhibition rates for the three algae species were 90%, 100%, and 81.04%, respectively. These results indicate that Sesuvium portulacastrum can release fatty acids and their derivatives to inhibit the growth of red tide algae, demonstrating its potential as a plant-based tool for red tide control and environmental remediation.
2025, 47(3): 85-97.
doi: 10.12284/hyxb2025040
Abstract:
To understand the spatio-temporal variation characteristics of zooplankton communities in the Nanji Islands sea area, three voyage surveys of aquatic organisms and hydrological factors were conducted in November 2022, May 2023, and September 2023, respectively. Laboratory experimental results showed that a total of 93 species of zooplankton were identified, including 20 species of plankton larvae. The 2023.09 voyage recorded the highest species richness (63 species), while the 2022.11 voyage had the lowest (45 species). Among these, 19 dominant species (Y ≥ 0.02) included Sagitta bedoti, Flaccisagitta enflata, Calanus sinicus, Acartia pacifica, and others. The average abundance of zooplankton was 512.84 ind./m³, and the average biomass was 614.82 mg/m³, with significant differences among the voyages. The 2023.09 voyage had the highest abundance and biomass, while the 2022.11 voyage had the lowest. The average values of the Shannon-Wiener diversity index (H'), species evenness index (J'), and richness index (D) for zooplankton were 1.64, 0.55, and 2.57, respectively. Results from Spearman correlation analysis, non-metric Multidimensional Scaling Analysis and Canonical Correspondence Analysis indicated that salinity, temperature, total nitrogen content, nitrate concentration, and phytoplankton abundance were important environmental factors influencing the biomass of dominant zooplankton species in the Nanji Islands sea area.
To understand the spatio-temporal variation characteristics of zooplankton communities in the Nanji Islands sea area, three voyage surveys of aquatic organisms and hydrological factors were conducted in November 2022, May 2023, and September 2023, respectively. Laboratory experimental results showed that a total of 93 species of zooplankton were identified, including 20 species of plankton larvae. The 2023.09 voyage recorded the highest species richness (63 species), while the 2022.11 voyage had the lowest (45 species). Among these, 19 dominant species (Y ≥ 0.02) included Sagitta bedoti, Flaccisagitta enflata, Calanus sinicus, Acartia pacifica, and others. The average abundance of zooplankton was 512.84 ind./m³, and the average biomass was 614.82 mg/m³, with significant differences among the voyages. The 2023.09 voyage had the highest abundance and biomass, while the 2022.11 voyage had the lowest. The average values of the Shannon-Wiener diversity index (H'), species evenness index (J'), and richness index (D) for zooplankton were 1.64, 0.55, and 2.57, respectively. Results from Spearman correlation analysis, non-metric Multidimensional Scaling Analysis and Canonical Correspondence Analysis indicated that salinity, temperature, total nitrogen content, nitrate concentration, and phytoplankton abundance were important environmental factors influencing the biomass of dominant zooplankton species in the Nanji Islands sea area.
2025, 47(3): 98-107.
doi: 10.12284/hyxb2025030
Abstract:
Aegiceras corniculatum is a common pioneer species in China’s mangroves. It plays an important role in the composition of estuarine higher plant communities and in preventing wind and waves along the coast in southern China. To gain a deeper understanding of the variation patterns of leaf functional traits in different developmental stages (old and young forests) of A. corniculatum, this study used A. corniculatum as the research object and analyzed the differences and trade-offs of leaf functional traits between old and young forests. The results show that: (1)leaf area (LA), leaf nitrogen content (LN), leaf thickness (LT), chlorophyll content (Chl) and leaf dry matter content (LDMC) of the old forest were significantly lower than that of the young forest, while the specific leaf area (SLA) shows that the old forest was significantly larger than that of the young forest; (2)the SLA of old and young forests of A. corniculatum was significantly negatively correlated with Chl, LN, LDMC and LT, but the negative correlation was stronger in the old forests and weaker in young forests. There was a significant positive correlation between the Chl, LN and LT in the old forests and the young forests, but the correlation ship was stronger in the young forests and weaker in the old forests; (3)the results of principal component analysis showed that SLA was the key trait affecting the stability of the old forests, while Chl and LN were the key traits affecting the growth and development of the young forests; (4)the trade-offs relationship between leaf functional traits in young forests is generally greater than that in the old forests.
Aegiceras corniculatum is a common pioneer species in China’s mangroves. It plays an important role in the composition of estuarine higher plant communities and in preventing wind and waves along the coast in southern China. To gain a deeper understanding of the variation patterns of leaf functional traits in different developmental stages (old and young forests) of A. corniculatum, this study used A. corniculatum as the research object and analyzed the differences and trade-offs of leaf functional traits between old and young forests. The results show that: (1)leaf area (LA), leaf nitrogen content (LN), leaf thickness (LT), chlorophyll content (Chl) and leaf dry matter content (LDMC) of the old forest were significantly lower than that of the young forest, while the specific leaf area (SLA) shows that the old forest was significantly larger than that of the young forest; (2)the SLA of old and young forests of A. corniculatum was significantly negatively correlated with Chl, LN, LDMC and LT, but the negative correlation was stronger in the old forests and weaker in young forests. There was a significant positive correlation between the Chl, LN and LT in the old forests and the young forests, but the correlation ship was stronger in the young forests and weaker in the old forests; (3)the results of principal component analysis showed that SLA was the key trait affecting the stability of the old forests, while Chl and LN were the key traits affecting the growth and development of the young forests; (4)the trade-offs relationship between leaf functional traits in young forests is generally greater than that in the old forests.
2025, 47(3): 108-117.
doi: 10.12284/hyxb2025018
Abstract:
The transport of phosphorus by suspended sediment plays a pivotal role as a nutrient and ecological factor in aquatic environments, particularly in the complex hydrodynamic and sedimentary settings of Jiangsu’s coastal tidal flats, where diverse organic coatings on sediment surfaces further complicate sediment dynamics. Investigating the impact of organic matter on both sediment transport and phosphorus adsorption processes, therefore, is crucial for predicting phosphorus dynamics in coastal tidal flats and nearshore waters. To elucidate the influence of organic matter content and sediment initiation characteristics on aqueous phosphorus mass concentrations, this study employs xanthan as a model organic substance. Through sediment initiation-resuspension-adsorption experiments and constant-temperature oscillation tests, the study systematically examines how xanthan alters sediment mobility and phosphorus adsorption under varying flow conditions. The research findings are as follows: (1) Xanthan significantly impedes the initiation of sediment motion from the bed, enhancing the bed’s resistance to erosive shear stress by approximately twofold. (2) Sediment initiation characteristics act as a direct determinant in the adsorption of phosphorus by the bed sediment, a marked increase in aqueous phosphorus concentration is observed only after substantial sediment initiation commences. (3) While xanthan itself has negligible direct impact on phosphorus adsorption, it indirectly suppresses phosphorus adsorption by the bed sediment through inhibiting sediment initiation.
The transport of phosphorus by suspended sediment plays a pivotal role as a nutrient and ecological factor in aquatic environments, particularly in the complex hydrodynamic and sedimentary settings of Jiangsu’s coastal tidal flats, where diverse organic coatings on sediment surfaces further complicate sediment dynamics. Investigating the impact of organic matter on both sediment transport and phosphorus adsorption processes, therefore, is crucial for predicting phosphorus dynamics in coastal tidal flats and nearshore waters. To elucidate the influence of organic matter content and sediment initiation characteristics on aqueous phosphorus mass concentrations, this study employs xanthan as a model organic substance. Through sediment initiation-resuspension-adsorption experiments and constant-temperature oscillation tests, the study systematically examines how xanthan alters sediment mobility and phosphorus adsorption under varying flow conditions. The research findings are as follows: (1) Xanthan significantly impedes the initiation of sediment motion from the bed, enhancing the bed’s resistance to erosive shear stress by approximately twofold. (2) Sediment initiation characteristics act as a direct determinant in the adsorption of phosphorus by the bed sediment, a marked increase in aqueous phosphorus concentration is observed only after substantial sediment initiation commences. (3) While xanthan itself has negligible direct impact on phosphorus adsorption, it indirectly suppresses phosphorus adsorption by the bed sediment through inhibiting sediment initiation.
2025, 47(3): 118-128.
doi: 10.12284/hyxb2025007
Abstract:
Sea ice is a typical environmental feature of polar sea areas, and pixel-level classification of ship-borne video images can provide high-resolution sea ice information. Due to the complex light conditions and sea ice morphology in polar scenes, traditional computer graphics methods lack the generalization needed for intelligent identification of sea ice elements. Therefore, this paper deploys a deep learning approach based on the DeeplabV3+ semantic segmentation network structure to identify sea ice elements in polar scenes. The dataset consists of sea ice images captured by the icebreaker Xuelong during its navigation in ice-covered regions, and also is used to train and validate the deep learning model. To meet the requirements of sea ice element identification and the characteristics of the underway observation video images, the pixel information is divided into four semantic categories: sea ice, sky, seawater, and ship. The deep learning model is built based on the correlation between image information and semantic information in the training set. The model trained is used to predict the semantic information of pixels in the validation set or other images, thereby achieving automatic identification of sea ice information. To study the robustness of this method, the influences of sea ice concentration, lighting conditions, and sea ice types on the identification results was further analyzed. Additionally, the effects of dataset size and the number of iterations on identification accuracy were examined. The recognition results for images show that the mean Intersection over Union (mIoU) for the four types of semantic information exceeds 95%, indicating that the deep learning method can accurately classify various elements in the polar environment.
Sea ice is a typical environmental feature of polar sea areas, and pixel-level classification of ship-borne video images can provide high-resolution sea ice information. Due to the complex light conditions and sea ice morphology in polar scenes, traditional computer graphics methods lack the generalization needed for intelligent identification of sea ice elements. Therefore, this paper deploys a deep learning approach based on the DeeplabV3+ semantic segmentation network structure to identify sea ice elements in polar scenes. The dataset consists of sea ice images captured by the icebreaker Xuelong during its navigation in ice-covered regions, and also is used to train and validate the deep learning model. To meet the requirements of sea ice element identification and the characteristics of the underway observation video images, the pixel information is divided into four semantic categories: sea ice, sky, seawater, and ship. The deep learning model is built based on the correlation between image information and semantic information in the training set. The model trained is used to predict the semantic information of pixels in the validation set or other images, thereby achieving automatic identification of sea ice information. To study the robustness of this method, the influences of sea ice concentration, lighting conditions, and sea ice types on the identification results was further analyzed. Additionally, the effects of dataset size and the number of iterations on identification accuracy were examined. The recognition results for images show that the mean Intersection over Union (mIoU) for the four types of semantic information exceeds 95%, indicating that the deep learning method can accurately classify various elements in the polar environment.
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