Current Articles
2024, Volume 46, Issue 1
Display Method:
2024,
46(1):
1-11.
doi: 10.12284/hyxb2024002
Abstract:
Study on the coral reef canopy hydrodynamics not only provides guidance for the health of coral reef ecosystem and the ecological restoration project, but also supports the decision-making process for the reef coast hazard prevention and mitigation under extreme wave events such as the typhoons. Meanwhile, it also has significant value for predicting the sediment transport over the reef and the reef coast evolution. This paper reviews the state-of-the-art research on reef canopy hydrodynamics, and systematically summarize the research progress from three aspects: the flows inside and outside of reef canopy, the characteristics of canopy resistance as well as the simulation of canopy resistance. This paper finally proposes the further research directions as follows: future study can focus on the hydrodynamics under more severe wave condition or under combined action of wave and current. It should also fully consider the anisotropy of canopy skeleton. Moreover, it can solve the Navier-Stokes equations directly to reproduce the finer flow field at the canopy scale.
Study on the coral reef canopy hydrodynamics not only provides guidance for the health of coral reef ecosystem and the ecological restoration project, but also supports the decision-making process for the reef coast hazard prevention and mitigation under extreme wave events such as the typhoons. Meanwhile, it also has significant value for predicting the sediment transport over the reef and the reef coast evolution. This paper reviews the state-of-the-art research on reef canopy hydrodynamics, and systematically summarize the research progress from three aspects: the flows inside and outside of reef canopy, the characteristics of canopy resistance as well as the simulation of canopy resistance. This paper finally proposes the further research directions as follows: future study can focus on the hydrodynamics under more severe wave condition or under combined action of wave and current. It should also fully consider the anisotropy of canopy skeleton. Moreover, it can solve the Navier-Stokes equations directly to reproduce the finer flow field at the canopy scale.
2024,
46(1):
12-26.
doi: 10.12284/hyxb2024024
Abstract:
Beach is a common and vulnerable coastal ecosystem with huge ecological service functions. Due to the multiple impacts of climate change and human activities, beach ecosystem has been seriously damaged. Beach nourishment is an effective approach to prevent coastal erosion and improve the beach environment by using sand replenishment to restore beach morphology. Previous nourishments have often neglected the impacts on beach ecosystem. Many studies show that beach nourishment have multifaceted, multi-scale and complex impacts on beach ecosystem. Based on reviewing previous researches, the compositions, characteristics and functions of beach ecosystem are summarized. The basic characteristics of beach ecological damage, the impact process and mechanism of beach nourishment on beach ecosystem at various scales are analyzed. Then, some adaptive measures for beach nourishment are suggested from the perspective of reducing negative ecological impacts, which would support coastal management and sustainable utilization of beach.
Beach is a common and vulnerable coastal ecosystem with huge ecological service functions. Due to the multiple impacts of climate change and human activities, beach ecosystem has been seriously damaged. Beach nourishment is an effective approach to prevent coastal erosion and improve the beach environment by using sand replenishment to restore beach morphology. Previous nourishments have often neglected the impacts on beach ecosystem. Many studies show that beach nourishment have multifaceted, multi-scale and complex impacts on beach ecosystem. Based on reviewing previous researches, the compositions, characteristics and functions of beach ecosystem are summarized. The basic characteristics of beach ecological damage, the impact process and mechanism of beach nourishment on beach ecosystem at various scales are analyzed. Then, some adaptive measures for beach nourishment are suggested from the perspective of reducing negative ecological impacts, which would support coastal management and sustainable utilization of beach.
2024,
46(1):
101-110.
doi: 10.12284/hyxb2024005
Abstract:
To study the hydrodynamic performance of an oscillating-water-column (OWC) wave energy converter in a real sea, a two-dimensional nonlinear numerical model of the interaction between irregular waves and a land-based OWC device is developed based on the potential flow theory and the high-order boundary element method (HOBEM) in this paper. The irregular waves are generated based on the JONSWAP spectrum. The viscous damping is introduced on the water surface boundary conditions inside the air chamber to consider the energy dissipation due to water viscosity. And physical modeling experiments are carried out in the wave-current flume at Dalian University of Technology to validate the numerical model. It is found that the OWC hydrodynamic efficiency under irregular waves is reduced in comparison with that under regular waves, especially in the low-frequency wave region where the efficiency difference is the largest. The frequency corresponding to the peak efficiency under the action of irregular waves is larger than that under regular waves. The dimensionless surface elevation inside the chamber decreases, while the dimensionless air pressure inside the chamber increases with the significant wave heights. The OWC hydrodynamic efficiency is less affected by the significant wave height. The frequency corresponding to the peak efficiency is not dependent on wave nonlinearity. This work can provide a reference for the design of OWCs.
To study the hydrodynamic performance of an oscillating-water-column (OWC) wave energy converter in a real sea, a two-dimensional nonlinear numerical model of the interaction between irregular waves and a land-based OWC device is developed based on the potential flow theory and the high-order boundary element method (HOBEM) in this paper. The irregular waves are generated based on the JONSWAP spectrum. The viscous damping is introduced on the water surface boundary conditions inside the air chamber to consider the energy dissipation due to water viscosity. And physical modeling experiments are carried out in the wave-current flume at Dalian University of Technology to validate the numerical model. It is found that the OWC hydrodynamic efficiency under irregular waves is reduced in comparison with that under regular waves, especially in the low-frequency wave region where the efficiency difference is the largest. The frequency corresponding to the peak efficiency under the action of irregular waves is larger than that under regular waves. The dimensionless surface elevation inside the chamber decreases, while the dimensionless air pressure inside the chamber increases with the significant wave heights. The OWC hydrodynamic efficiency is less affected by the significant wave height. The frequency corresponding to the peak efficiency is not dependent on wave nonlinearity. This work can provide a reference for the design of OWCs.
2024,
46(1):
27-38.
doi: 10.12284/hyxb2024070
Abstract:
Based on the high-resolution oceanic numerical model product of MITgcm with a resolution of (1/48)°, the geostrophic balanced motion and unbalanced wave motion are decomposed via the frequency-wavenumber spectrum analysis method to analyze the distribution of submesoscale characteristics and diagnose the main factors affecting their seasonal variations in the Agulhas current system. The results show that the submesoscale processes in the Agulhas current system have a significant seasonal distribution with strong features in winter but weak features in summer. The mixed layer baroclinic instability is the main reason affecting the submesoscale seasonal differences in the area. In addition, the geostrophic balanced motions are predominant in the submesoscale process in the regions with stronger eddy kinetic energy (EKE) and have no obvious seasonality. For the regions with weaker EKE, the balanced and unbalanced geostrophic motions show significant seasonality, where the local mixing layer shallowness is responsible for the increase of the unbalanced kinetic energy in summer. Our analysis helps to further clarify the characteristics of submesoscale seasonal variation and its primary factors in the Agulhas current system. The effective separation of geostrophic balanced and unbalanced motion enhances our understanding of energy transformation between multiscale processes in the ocean.
Based on the high-resolution oceanic numerical model product of MITgcm with a resolution of (1/48)°, the geostrophic balanced motion and unbalanced wave motion are decomposed via the frequency-wavenumber spectrum analysis method to analyze the distribution of submesoscale characteristics and diagnose the main factors affecting their seasonal variations in the Agulhas current system. The results show that the submesoscale processes in the Agulhas current system have a significant seasonal distribution with strong features in winter but weak features in summer. The mixed layer baroclinic instability is the main reason affecting the submesoscale seasonal differences in the area. In addition, the geostrophic balanced motions are predominant in the submesoscale process in the regions with stronger eddy kinetic energy (EKE) and have no obvious seasonality. For the regions with weaker EKE, the balanced and unbalanced geostrophic motions show significant seasonality, where the local mixing layer shallowness is responsible for the increase of the unbalanced kinetic energy in summer. Our analysis helps to further clarify the characteristics of submesoscale seasonal variation and its primary factors in the Agulhas current system. The effective separation of geostrophic balanced and unbalanced motion enhances our understanding of energy transformation between multiscale processes in the ocean.
2024,
46(1):
39-52.
doi: 10.12284/hyxb2024018
Abstract:
The Sardinops melanostictus and the Scomber japonicus are important economic species in the northwestn Pacific Ocean, and exploring the correlation between their habitat changes is conducive to the rational development and management of fishery resources. This study utilizes fishery data of Sardinops melanostictus and Scomber japonicus in the northwestern Pacific Ocean from June to November between 2017 and 2021. By incorporating three key environmental variables, namely sea surface temperature, sea surface height, and chlorophyll a mass concentration, habitat models with different weights are constructed. The models are then validated using fishery data from 2021. The optimal models are selected to predict the most suitable habitat distribution of Sardinops melanostictus and Scomber japonicus under different El Niño-Southern Oscillation (ENSO) events. The study analyzes the differences and synchronicity in the spatial and temporal distribution of the most suitable habitat between the two species under different ENSO events. The results indicate that the suitable habitat area of Sardinops melanostictus (above 15%) was higher than that of Scomber japonicus (less than 6%) under different ENSO events; however, the growth rate of the most suitable habitat area for Sardinops melanostictus under La Niña events is higher than that of El Niño events. The former has a growth rate of 0.197 and the latter has a growth rate of 0.123, on the contrary, the growth rate of Scomber japonicus under the La Niña event is lower than that of El Niño event, the former has a growth rate of 1.114 and the latter has a growth rate of 2.082; additionally, when the distribution locations of Sardinops melanostictus and Scomber japonicus are close to each other, it promotes favorable conditions for their habitats. On the other hand, when the distribution locations are far apart, it somewhat inhibits the increase in the suitable habitat area for Scomber japonicus. The co-variation of suitable habitat areas for Sardinops melanostictus and Scomber japonicus under different ENSO events may be related to their interspecies relationship (competition/predation-prey) and the distribution of ocean currents in the northwestern Pacific Ocean.
The Sardinops melanostictus and the Scomber japonicus are important economic species in the northwestn Pacific Ocean, and exploring the correlation between their habitat changes is conducive to the rational development and management of fishery resources. This study utilizes fishery data of Sardinops melanostictus and Scomber japonicus in the northwestern Pacific Ocean from June to November between 2017 and 2021. By incorporating three key environmental variables, namely sea surface temperature, sea surface height, and chlorophyll a mass concentration, habitat models with different weights are constructed. The models are then validated using fishery data from 2021. The optimal models are selected to predict the most suitable habitat distribution of Sardinops melanostictus and Scomber japonicus under different El Niño-Southern Oscillation (ENSO) events. The study analyzes the differences and synchronicity in the spatial and temporal distribution of the most suitable habitat between the two species under different ENSO events. The results indicate that the suitable habitat area of Sardinops melanostictus (above 15%) was higher than that of Scomber japonicus (less than 6%) under different ENSO events; however, the growth rate of the most suitable habitat area for Sardinops melanostictus under La Niña events is higher than that of El Niño events. The former has a growth rate of 0.197 and the latter has a growth rate of 0.123, on the contrary, the growth rate of Scomber japonicus under the La Niña event is lower than that of El Niño event, the former has a growth rate of 1.114 and the latter has a growth rate of 2.082; additionally, when the distribution locations of Sardinops melanostictus and Scomber japonicus are close to each other, it promotes favorable conditions for their habitats. On the other hand, when the distribution locations are far apart, it somewhat inhibits the increase in the suitable habitat area for Scomber japonicus. The co-variation of suitable habitat areas for Sardinops melanostictus and Scomber japonicus under different ENSO events may be related to their interspecies relationship (competition/predation-prey) and the distribution of ocean currents in the northwestern Pacific Ocean.
2024,
46(1):
53-63.
doi: 10.12284/hyxb2024016
Abstract:
Based on the data from 56 acoustic survey sections in the southwestern Indian Ocean from 2011 to 2020, a total of 201 diel vertical migration were observed. The characteristics of diel vertical migration of the deep scattering layer and its spatiotemporal differences were analyzed. The research results show that the deep scattering layer in the southwestern India Ocean exhibits a stratification phenomenon, with the first scattering layer located in the shallow water layer below 200 m. The average depth of its nautical area scattering coefficient (NASC) peak is (58.66 ± 24.63) m, and there is a significant difference between summer and winter (p < 0.001); the second scattering layer is located in the water layer between 400 m and 700 m, with an average depth of (589.02 ± 66.33) m for its NASC peak. There is no significant difference between summer and winter (p = 0.51). The average time for the scattering layer to migrate upwards is 16:20, the average time for the end of migration is 18:31, and the average migration rate is (5.28 ± 1.53) cm/s; the average time for the scattering layer to start migrating downwards is 4:38, and the average time for the end of migration is 6:52. The average migration rate is (5.56 ± 2.13) cm/s. As latitude increases, the start time of downward migration become later and the migration rate slows down; as the longitude increases, the migration rate of the scattering layer also slows down, and there is a significant difference between different longitude sea areas (p < 0.001). Analysis suggests that studying the seasonal changes in the physical and chemical environment of the sea area, as well as the different life cycle stages of organisms in the scattering layer, are the main reasons for the spatiotemporal differences in the vertical structure and diurnal vertical migration characteristics of the scattering layer. They are of great significance in explaining the diurnal vertical migration behavior of tuna and indicating the distribution of tuna fishing grounds.
Based on the data from 56 acoustic survey sections in the southwestern Indian Ocean from 2011 to 2020, a total of 201 diel vertical migration were observed. The characteristics of diel vertical migration of the deep scattering layer and its spatiotemporal differences were analyzed. The research results show that the deep scattering layer in the southwestern India Ocean exhibits a stratification phenomenon, with the first scattering layer located in the shallow water layer below 200 m. The average depth of its nautical area scattering coefficient (NASC) peak is (58.66 ± 24.63) m, and there is a significant difference between summer and winter (p < 0.001); the second scattering layer is located in the water layer between 400 m and 700 m, with an average depth of (589.02 ± 66.33) m for its NASC peak. There is no significant difference between summer and winter (p = 0.51). The average time for the scattering layer to migrate upwards is 16:20, the average time for the end of migration is 18:31, and the average migration rate is (5.28 ± 1.53) cm/s; the average time for the scattering layer to start migrating downwards is 4:38, and the average time for the end of migration is 6:52. The average migration rate is (5.56 ± 2.13) cm/s. As latitude increases, the start time of downward migration become later and the migration rate slows down; as the longitude increases, the migration rate of the scattering layer also slows down, and there is a significant difference between different longitude sea areas (p < 0.001). Analysis suggests that studying the seasonal changes in the physical and chemical environment of the sea area, as well as the different life cycle stages of organisms in the scattering layer, are the main reasons for the spatiotemporal differences in the vertical structure and diurnal vertical migration characteristics of the scattering layer. They are of great significance in explaining the diurnal vertical migration behavior of tuna and indicating the distribution of tuna fishing grounds.
2024,
46(1):
64-76.
doi: 10.12284/hyxb2024020
Abstract:
The concept of ecosystem-based fisheries management has been widely recognized, but it’s application in the construction of marine ranch is still very rare. In this study, based on the data from a bottom trawl survey of fishery resources conducted in the waters of Wuzhizhou Island from 2020 to 2021, a marine ranch fish community size-spectrum model (SSM) was built, which reflects the complex structure of food webs and interspecies interactions in marine ranch, to assess the impacts of fishing on the fish community in marine ranch. The study analyzed the effects of changes in species-specific fishing death coefficient on fish community by simulating two management strategies (single-species management and multispecies management) and monitored the state of fish community characteristics using five community ecological indicators: the total biomass of the community, the slope of size spectrum, the mean maximum weight, the mean weight, and the large fish index. The results of the single-species management strategy showed that the marine ranch ecosystem of Wuzhizhou Island showed top-down control, and there was a strong regulatory effect of carnivorous fish on plankton-feeding fish. Complex interactions such as competitive predation among different species produce trophic cascade effects after changes in fishing death coefficient. The results of the multispecies management strategy showed that fishing death coefficient of Muraenesox cinereus had the greatest effect on the slope of size spectrum, and that fishing death coefficient of Trachiocephalus myops and Muraenesox cinereus had the greatest effect on fish community biomass and community structure and function. The results of this study have important implications for the conservation and stabilization of fish community, and can help managers to better understand the potential impacts of changes in fishing death coefficient rates on fish communities, so that viable and effective conservation and management strategies can be developed based on the importance of the species to the fishery.
The concept of ecosystem-based fisheries management has been widely recognized, but it’s application in the construction of marine ranch is still very rare. In this study, based on the data from a bottom trawl survey of fishery resources conducted in the waters of Wuzhizhou Island from 2020 to 2021, a marine ranch fish community size-spectrum model (SSM) was built, which reflects the complex structure of food webs and interspecies interactions in marine ranch, to assess the impacts of fishing on the fish community in marine ranch. The study analyzed the effects of changes in species-specific fishing death coefficient on fish community by simulating two management strategies (single-species management and multispecies management) and monitored the state of fish community characteristics using five community ecological indicators: the total biomass of the community, the slope of size spectrum, the mean maximum weight, the mean weight, and the large fish index. The results of the single-species management strategy showed that the marine ranch ecosystem of Wuzhizhou Island showed top-down control, and there was a strong regulatory effect of carnivorous fish on plankton-feeding fish. Complex interactions such as competitive predation among different species produce trophic cascade effects after changes in fishing death coefficient. The results of the multispecies management strategy showed that fishing death coefficient of Muraenesox cinereus had the greatest effect on the slope of size spectrum, and that fishing death coefficient of Trachiocephalus myops and Muraenesox cinereus had the greatest effect on fish community biomass and community structure and function. The results of this study have important implications for the conservation and stabilization of fish community, and can help managers to better understand the potential impacts of changes in fishing death coefficient rates on fish communities, so that viable and effective conservation and management strategies can be developed based on the importance of the species to the fishery.
2024,
46(1):
77-87.
doi: 10.12284/hyxb2024012
Abstract:
The semienclosed pyloric caecum of Larimichthys crocea is an ideal organ to perform the host source tracking, as it containes several local bacteria colonized during early development. The alpha diversity, relative abundance of core bacteria and network relationship of the pyloric caecum microbiota in L. crocea from Sansha Bay were analyzed using the Illumina high-throughput sequencing. Furthermore, the random forest model was used to predict the population source (the wild population or the farmed population). The results showed that the farmed fish had more unique OUT and higher alpha diversity than the wild one. The wild and farmed fish significantly differed in the relative abundance of dominant bacteria (Proteobacteria, Firmicutes, Bacteroidota, Actinobacteria and Acidobacteria) (p < 0.05). The result of network analysis showed that the wild fish had higher ratio of negative to positive edges and modularity, but fewer nodes and edges than the farmed fish. Furthermore, a random forest classification prediction model with the accuracy of 92.31%, the Kappa coefficient of 0.8452, and an area under the ROC curve of 0.952 4 was constructed. Using this prediction model, the accuracy of source identification for the wild and farmed fish was 91.67% and 92.86%, respectively. Overall, the structure of microbial communities in the pyloric caecum of L. crocea was different between the wild and farmed populations, making it a potential marker for host source tracking. Our findings provide new insights into distinguishing wild and farmed L. crocea.
The semienclosed pyloric caecum of Larimichthys crocea is an ideal organ to perform the host source tracking, as it containes several local bacteria colonized during early development. The alpha diversity, relative abundance of core bacteria and network relationship of the pyloric caecum microbiota in L. crocea from Sansha Bay were analyzed using the Illumina high-throughput sequencing. Furthermore, the random forest model was used to predict the population source (the wild population or the farmed population). The results showed that the farmed fish had more unique OUT and higher alpha diversity than the wild one. The wild and farmed fish significantly differed in the relative abundance of dominant bacteria (Proteobacteria, Firmicutes, Bacteroidota, Actinobacteria and Acidobacteria) (p < 0.05). The result of network analysis showed that the wild fish had higher ratio of negative to positive edges and modularity, but fewer nodes and edges than the farmed fish. Furthermore, a random forest classification prediction model with the accuracy of 92.31%, the Kappa coefficient of 0.8452, and an area under the ROC curve of 0.952 4 was constructed. Using this prediction model, the accuracy of source identification for the wild and farmed fish was 91.67% and 92.86%, respectively. Overall, the structure of microbial communities in the pyloric caecum of L. crocea was different between the wild and farmed populations, making it a potential marker for host source tracking. Our findings provide new insights into distinguishing wild and farmed L. crocea.
2024,
46(1):
88-100.
doi: 10.12284/hyxb2024010
Abstract:
The ocean acidification effect is increasing with the large amount of CO2 emissions. To investigate the effects of future seawater acidification on Ruditapes philippinarum, a control group (pH = 8.1) and acidification group (pH = 7.7, 7.1 and 6.4) were set up for 42 days. The changes in tissue structure, immune and antioxidant enzyme activities of Ruditapes philippinarum under acidification conditions were measured, as well as the effects produced at the molecular level. The results show that when Ruditapes philippinarum are placed in an acidified seawater environment, gill filament spacing expands with decreasing pH, gill filament cilia adhere, and the pipes and outer epidermal folds of the mantle gradually deepen. The activities of acid phosphatase (ACP) and superoxide dismutase (SOD) in gill tissues show a pattern of decreasing followed by increasing. Alkaline phosphatase (AKP) activities exhibit different trends in each group. Total antioxidant capacity (T-AOC), catalase (CAT), and lysozyme (LZM) activities show a pattern of increasing followed by decreasing. Glutathione peroxidase (GSH-Px) activities in gill and visceral masses show a continuous increase. LZM activity in the viscera group displays varying trends, while ACP activity shows a decreasing and then increasing pattern. AKP, SOD, and CAT activities exhibited an increasing and then decreasing pattern, while T-AOC activity shows a continuous decrease. Analysis of the transcriptome reveals that the GO functions in gill tissue are mainly enriched in DNA integration, integral components of the membrane, and RNA-directed DNA polymerase activity, among others. The KEGG pathway analysis shows enrichment in the phagosome pathway and pathways related to protein processing in the endoplasmic reticulum. The acidification of seawater caused varying degrees of damage to the tissues of Ruditapes philippinarum, disrupting its internal environmental homeostasis and altering metabolic levels and immune-related gene expression, and led to an increased risk of disease and even death in Ruditapes philippinarum.
The ocean acidification effect is increasing with the large amount of CO2 emissions. To investigate the effects of future seawater acidification on Ruditapes philippinarum, a control group (pH = 8.1) and acidification group (pH = 7.7, 7.1 and 6.4) were set up for 42 days. The changes in tissue structure, immune and antioxidant enzyme activities of Ruditapes philippinarum under acidification conditions were measured, as well as the effects produced at the molecular level. The results show that when Ruditapes philippinarum are placed in an acidified seawater environment, gill filament spacing expands with decreasing pH, gill filament cilia adhere, and the pipes and outer epidermal folds of the mantle gradually deepen. The activities of acid phosphatase (ACP) and superoxide dismutase (SOD) in gill tissues show a pattern of decreasing followed by increasing. Alkaline phosphatase (AKP) activities exhibit different trends in each group. Total antioxidant capacity (T-AOC), catalase (CAT), and lysozyme (LZM) activities show a pattern of increasing followed by decreasing. Glutathione peroxidase (GSH-Px) activities in gill and visceral masses show a continuous increase. LZM activity in the viscera group displays varying trends, while ACP activity shows a decreasing and then increasing pattern. AKP, SOD, and CAT activities exhibited an increasing and then decreasing pattern, while T-AOC activity shows a continuous decrease. Analysis of the transcriptome reveals that the GO functions in gill tissue are mainly enriched in DNA integration, integral components of the membrane, and RNA-directed DNA polymerase activity, among others. The KEGG pathway analysis shows enrichment in the phagosome pathway and pathways related to protein processing in the endoplasmic reticulum. The acidification of seawater caused varying degrees of damage to the tissues of Ruditapes philippinarum, disrupting its internal environmental homeostasis and altering metabolic levels and immune-related gene expression, and led to an increased risk of disease and even death in Ruditapes philippinarum.
2024,
46(1):
121-130.
doi: 10.12284/hyxb2024022
Abstract:
Based on the comprehensive fishery survey in the Chongming Island adjacent waters in November 2020, January 2021, April 2021, and August 2021, we used an open-source program Rpath to build a mass balance model containing 22 functional groups for this area. The ecosystem structure and characteristics in this sea area were then studied. Results showed that the trophic level for these 18 functional groups ranged from 1 to 4.32, with the highest trophic level of bottom carnivorous fish. The ecological transfer efficiency of small benthic organisms is the lowest (0.01), suggesting a bottleneck in their energy transfer to higher trophic levels and indicated it was the bottleneck to limit the energy transfer in the benthic food chain. The analysis of the overall characteristics of the ecosystem shows that the total system throughput of the Chongming Island adjacent waters ecosystem was 2 909.42 t/(km2·a), which was lower than that of the nearby marine ecosystem. Phytoplankton contributes 60% of the energy to the total primary productivity of the ecosystem and was the main nutrient source of this ecosystem. The total primary production/total respiration is 1.99 and the system omnivorous index is 0.18. This indicate that the Chongming Island adjacent waters ecosystem has low maturity, simple trophic interaction, and low recovery ability after disturbance. Sensitivity analysis showed that functional group biomass was the main index that affected the accuracy of ecosystem model output. The results of this study can provide a reference for the evaluation of the effect of the Changjiang River fishing ban.
Based on the comprehensive fishery survey in the Chongming Island adjacent waters in November 2020, January 2021, April 2021, and August 2021, we used an open-source program Rpath to build a mass balance model containing 22 functional groups for this area. The ecosystem structure and characteristics in this sea area were then studied. Results showed that the trophic level for these 18 functional groups ranged from 1 to 4.32, with the highest trophic level of bottom carnivorous fish. The ecological transfer efficiency of small benthic organisms is the lowest (0.01), suggesting a bottleneck in their energy transfer to higher trophic levels and indicated it was the bottleneck to limit the energy transfer in the benthic food chain. The analysis of the overall characteristics of the ecosystem shows that the total system throughput of the Chongming Island adjacent waters ecosystem was 2 909.42 t/(km2·a), which was lower than that of the nearby marine ecosystem. Phytoplankton contributes 60% of the energy to the total primary productivity of the ecosystem and was the main nutrient source of this ecosystem. The total primary production/total respiration is 1.99 and the system omnivorous index is 0.18. This indicate that the Chongming Island adjacent waters ecosystem has low maturity, simple trophic interaction, and low recovery ability after disturbance. Sensitivity analysis showed that functional group biomass was the main index that affected the accuracy of ecosystem model output. The results of this study can provide a reference for the evaluation of the effect of the Changjiang River fishing ban.
2024,
46(1):
111-120.
doi: 10.12284/hyxb2024006
Abstract:
Manganese (Mn) is an essential trace element for the marine ecosystem. As the transitional zone between rivers and oceans, estuaries have a significant effect on dissolved Mn and its terrigenous input. In this study, the distribution of dissolved Mn, investigated in the surface water of Changjiang River Estuary and its adjacent area during September 2019 (autumn), March 2021 (spring) and July 2021 (summer), was analyzed by automatic solid phase extraction and inductively coupled plasma mass spectrometry. The results indicated that the average concentration and estuarine behaviors of dissolved Mn showed seasonal variations between the three cruises: the maximum average concentration occurred in summer and dissolved Mn was removed firstly and then added with the increase of salinity; the medium average concentration occurred in autumn and dissolved Mn was mainly removed with the increase of salinity; the minimum average concentration occurred in spring and dissloved Mn was mainly conservative with the increase of salinity. The results of significance test indicated that only in the season when the fresh water had high concentrations, dissloved Mn carried by the Changjiang River had significant influence on the distribution of dissolved Mn in the Changjiang River Estuary and its adjacent area; the distribution of dissolved Mn was co-dominated by a variety of biogeochemical processes in the season when the concentrations were low in the fresh water. The high suspended particulate matter concentrations were the important factor of the removal of dissolved Mn in the Changjiang Estuary’s water with medium-low salinity. And the addition mechanism of dissolved Mn in water with high salinity needs further vestigation.
Manganese (Mn) is an essential trace element for the marine ecosystem. As the transitional zone between rivers and oceans, estuaries have a significant effect on dissolved Mn and its terrigenous input. In this study, the distribution of dissolved Mn, investigated in the surface water of Changjiang River Estuary and its adjacent area during September 2019 (autumn), March 2021 (spring) and July 2021 (summer), was analyzed by automatic solid phase extraction and inductively coupled plasma mass spectrometry. The results indicated that the average concentration and estuarine behaviors of dissolved Mn showed seasonal variations between the three cruises: the maximum average concentration occurred in summer and dissolved Mn was removed firstly and then added with the increase of salinity; the medium average concentration occurred in autumn and dissolved Mn was mainly removed with the increase of salinity; the minimum average concentration occurred in spring and dissloved Mn was mainly conservative with the increase of salinity. The results of significance test indicated that only in the season when the fresh water had high concentrations, dissloved Mn carried by the Changjiang River had significant influence on the distribution of dissolved Mn in the Changjiang River Estuary and its adjacent area; the distribution of dissolved Mn was co-dominated by a variety of biogeochemical processes in the season when the concentrations were low in the fresh water. The high suspended particulate matter concentrations were the important factor of the removal of dissolved Mn in the Changjiang Estuary’s water with medium-low salinity. And the addition mechanism of dissolved Mn in water with high salinity needs further vestigation.
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