2025 Vol. 47, No. 11
Display Method:
2025, 47(11): 1-3.
Abstract:
2025, 47(11): 1-12.
doi: 10.12284/hyxb2025126
Abstract:
Massive Porites corals, widely inhabiting in tropical oceans, are considered ideal archives for high-resolution environmental records and have garnered significant attention in the fields of paleoclimate and paleoenvironmental reconstruction. The fluorescence emitted by coral skeletons under long-wave ultraviolet light, due to its sensitivity to terrestrial runoff, pollutants, and climatic events, has emerged as an another tool for revealing various environmental changes related to rainfall, river discharge, and other factors. This review synthesizes the formation mechanisms of fluorescent substances in coral skeletons, measurement techniques, applications in environmental reconstruction, as well as current challenges and future research directions. Overall, the fluorescent signals in coral skeletons primarily originate from terrestrially derived organic matter dominated by fulvic acids and humic-like substances produced by symbiotic algal metabolism. Additionally, coral skeletal structure, mineral properties, and interactions with environmental factors such as rainfall and runoff influence fluorescence characteristics. By combining high-precision micro-sampling techniques with fluorescence analysis, scientists have successfully reconstructed environmental histories of terrestrial runoff, precipitation, and human activities across different timescales. Based on current international research progress, this paper suggests that future studies should explore novel analytical techniques, develop more accurate fluorescence-hydrological quantitative models by integrating multi-source data, and strengthen cross-validation with other proxy indicators to establish a high-precision, high-resolution global coral fluorescence database.
Massive Porites corals, widely inhabiting in tropical oceans, are considered ideal archives for high-resolution environmental records and have garnered significant attention in the fields of paleoclimate and paleoenvironmental reconstruction. The fluorescence emitted by coral skeletons under long-wave ultraviolet light, due to its sensitivity to terrestrial runoff, pollutants, and climatic events, has emerged as an another tool for revealing various environmental changes related to rainfall, river discharge, and other factors. This review synthesizes the formation mechanisms of fluorescent substances in coral skeletons, measurement techniques, applications in environmental reconstruction, as well as current challenges and future research directions. Overall, the fluorescent signals in coral skeletons primarily originate from terrestrially derived organic matter dominated by fulvic acids and humic-like substances produced by symbiotic algal metabolism. Additionally, coral skeletal structure, mineral properties, and interactions with environmental factors such as rainfall and runoff influence fluorescence characteristics. By combining high-precision micro-sampling techniques with fluorescence analysis, scientists have successfully reconstructed environmental histories of terrestrial runoff, precipitation, and human activities across different timescales. Based on current international research progress, this paper suggests that future studies should explore novel analytical techniques, develop more accurate fluorescence-hydrological quantitative models by integrating multi-source data, and strengthen cross-validation with other proxy indicators to establish a high-precision, high-resolution global coral fluorescence database.
2025, 47(11): 13-26.
doi: 10.12284/hyxb2025134
Abstract:
Sexual reproduction in scleractinian corals is a fundamental biological process that sustains the structure and function of coral reef ecosystems. It directly determines population dynamics and genetic diversity, thereby playing a crucial role in the stability and evolution of coral reefs. This review summarizes recent advances in the study of coral sexual reproduction, including: (1) reproductive strategies, (2) gonadal development, (3) spawning and fertilization, (4) embryogenesis, (5) larval settlement, and (6) juvenile development. Current research indicates that coral sexual reproduction is jointly regulated by endogenous biological mechanisms and exogenous environmental factors; however, the detailed molecular mechanisms underlying these processes remain largely unclear. Future studies should focus on elucidating the environmental regulation of spawning timing, mechanisms inducing larval settlement, establishment and plasticity of early symbiotic relationships, and the development of molecular-assisted breeding strategies for selecting thermotolerant coral strains.
Sexual reproduction in scleractinian corals is a fundamental biological process that sustains the structure and function of coral reef ecosystems. It directly determines population dynamics and genetic diversity, thereby playing a crucial role in the stability and evolution of coral reefs. This review summarizes recent advances in the study of coral sexual reproduction, including: (1) reproductive strategies, (2) gonadal development, (3) spawning and fertilization, (4) embryogenesis, (5) larval settlement, and (6) juvenile development. Current research indicates that coral sexual reproduction is jointly regulated by endogenous biological mechanisms and exogenous environmental factors; however, the detailed molecular mechanisms underlying these processes remain largely unclear. Future studies should focus on elucidating the environmental regulation of spawning timing, mechanisms inducing larval settlement, establishment and plasticity of early symbiotic relationships, and the development of molecular-assisted breeding strategies for selecting thermotolerant coral strains.
2025, 47(11): 84-94.
doi: 10.12284/hyxb2025124
Abstract:
To reveal the effect of high temperature on the ammonia assimilation of Pocillopora damicornis and elucidate the thermal adaptation mechanism of scleractinian coral, we identified and cloned an ammonia transporter gene PdRhp-1 from P. damicornis. The open reading frame (ORF) of PdRhp-1 is1410 bp, encoding a polypeptide chain composed of 469 amino acid residues. Sequence analysis showed that PdRhp-1 encodes a hydrophobic transmembrane protein with 12 transmembrane domains and belongs to the Rhesus-type ammonia transporter. Its amino acid sequence shares 44.14% identity with Homo sapiens ammonia transporter RhCG. In order to analyze the biological function of PdRhp-1, its recombinant expression vector was transfected into HEK293T cells, and ammonium chloride was added to the culture medium. It was found that the total ammonia uptake rate in the cells expressing PdRhp-1 was significantly higher than that in the control group, indicating that PdRhp-1 has ammonia transport function. At the same time, the transcriptome data of high temperature treated P. damicornis were analyzed, and it was found that high temperature significantly inhibited the expression of PdRhp-1 and some genes related to ammonia assimilation. The above results demonstrate that PdRhp-1 encodes a Rhesus-type ammonia transporter, and high temperature may affect the symbiotic homeostasis of corals and zooxanthellae by inhibiting the ammonia transport process mediated by this protein.
To reveal the effect of high temperature on the ammonia assimilation of Pocillopora damicornis and elucidate the thermal adaptation mechanism of scleractinian coral, we identified and cloned an ammonia transporter gene PdRhp-1 from P. damicornis. The open reading frame (ORF) of PdRhp-1 is
2025, 47(11): 95-107.
doi: 10.12284/hyxb2025114
Abstract:
In order to compare the seawater quality, the growth and nutrient composition of harvesting period Pacific oysters (Crassostrea gigas) under two different culture model of oyster monoculture or polyculture with Laminaria japonica (L. japonica) in Longkou. The indicators such as physicochemical factors, bacteria and phytoplankton in seawater from aquaculture areas (monoculture area M1, polyculture area M2) were detected during a period time, the growth and nutrient composition of oysters in M1 and M2 were assayed and compared when oysters were harvested. The results showed that there had no significant difference in water temperature, salinity, pH, dissolved oxygen (DO) and vibrio abundance between M1 and M2, and they were all in line with the national seawater quality standard of Class II. The content of chemical oxygen demand (COD), nitrogen and phosphorus nutrient salts, heterotrophic bacterial abundance content in M2 were lower than that in M1 in most of months, we inferred that L. japonica in M2 could effectively absorb organic nitrogen and phosphorus from oyster metabolic wastes. The diatom content was higher in M2 than that in M1, it maybe be related to the fact that the nitrogen to phosphorus ratio in M2 was more suitable for diatom growth, and oysters in M2 indirectly reduce their consumption of phytoplankton by filter feeding on L. japonica detritus. The oyster’s plumpness, soft body wet weight and protein content in M2 were significantly (P ＜ 0.05) higher than that in M1, the oyster’s shell width and fat content in M2 were extremely significantly (P ＜ 0.01) higher than that in M1, it was believed that oysters in M2 could filter-fed the L. japonica detritus at the same time the L. japonica reduced seawater COD in M2 and purified the seawater, all above factors were beneficial for oyster growth. The water content, ash content and shell dry weight were significantly higher (P ＜ 0.05) in oysters from M1 than M2, total sugars in oysters from M1 were extremely significantly higher (P ＜ 0.01) than from M2, the above results were speculated to be related to the low phytoplankton densities in M1, which increased filter feeding frequency and energy consumption of oyster in M1. EAA was significantly higher (P ＜ 0.05) in oysters from M1 than from M2, it was believed that rich species of phytoplankton and higher nutrient salts content could promote EAA accumulation. The study suggested that shellfish-algae polyculture can increases the consumption of oyster metabolites, prevent seawater pollution, and facilitate oyster growth.
In order to compare the seawater quality, the growth and nutrient composition of harvesting period Pacific oysters (Crassostrea gigas) under two different culture model of oyster monoculture or polyculture with Laminaria japonica (L. japonica) in Longkou. The indicators such as physicochemical factors, bacteria and phytoplankton in seawater from aquaculture areas (monoculture area M1, polyculture area M2) were detected during a period time, the growth and nutrient composition of oysters in M1 and M2 were assayed and compared when oysters were harvested. The results showed that there had no significant difference in water temperature, salinity, pH, dissolved oxygen (DO) and vibrio abundance between M1 and M2, and they were all in line with the national seawater quality standard of Class II. The content of chemical oxygen demand (COD), nitrogen and phosphorus nutrient salts, heterotrophic bacterial abundance content in M2 were lower than that in M1 in most of months, we inferred that L. japonica in M2 could effectively absorb organic nitrogen and phosphorus from oyster metabolic wastes. The diatom content was higher in M2 than that in M1, it maybe be related to the fact that the nitrogen to phosphorus ratio in M2 was more suitable for diatom growth, and oysters in M2 indirectly reduce their consumption of phytoplankton by filter feeding on L. japonica detritus. The oyster’s plumpness, soft body wet weight and protein content in M2 were significantly (P ＜ 0.05) higher than that in M1, the oyster’s shell width and fat content in M2 were extremely significantly (P ＜ 0.01) higher than that in M1, it was believed that oysters in M2 could filter-fed the L. japonica detritus at the same time the L. japonica reduced seawater COD in M2 and purified the seawater, all above factors were beneficial for oyster growth. The water content, ash content and shell dry weight were significantly higher (P ＜ 0.05) in oysters from M1 than M2, total sugars in oysters from M1 were extremely significantly higher (P ＜ 0.01) than from M2, the above results were speculated to be related to the low phytoplankton densities in M1, which increased filter feeding frequency and energy consumption of oyster in M1. EAA was significantly higher (P ＜ 0.05) in oysters from M1 than from M2, it was believed that rich species of phytoplankton and higher nutrient salts content could promote EAA accumulation. The study suggested that shellfish-algae polyculture can increases the consumption of oyster metabolites, prevent seawater pollution, and facilitate oyster growth.
2025, 47(11): 108-120.
doi: 10.12284/hyxb2025140
Abstract:
Since 2008, the South Yellow Sea has been persistently affected by green tide disasters caused by Ulva prolifera, while since 2009, the North Yellow Sea has frequently experienced large-scale macroalgal accumulations. The massive outbreaks of green tides severely damage marine ecosystems and threaten coastal ecological balance and economic structures. However, research on the differences in green tide outbreaks between the South Yellow Sea and North Yellow Sea remains limited. This study systematically compares the differences in Ulva prolifera between the two regions from two complementary dimensions—spatiotemporal distribution patterns and genetic basis—using multi-source remote sensing data, UAV monitoring, and molecular biology methods. The results indicate: (1) Significant differences in outbreak timing and scale. Ulva prolifera in the South Yellow Sea first appears in May, reaches its maximum coverage in mid-to-late June, and gradually disappears between July and August, with an entire life cycle lasting approximately 50–90 d. In contrast, Ulva prolifera in the North Yellow Sea is locally sourced, appearing in the coastal waters of Yantai from late June to early July and gradually disappearing in August. It exhibits smaller coverage areas and shorter duration compared to the South Yellow Sea. In recent years, the outbreak area in the South Yellow Sea has consistently exceeded 200 km2, while that in the North Yellow Sea has remained within2000 m2, significantly smaller. (2) From 2018 to 2024, the migration paths of Ulva prolifera in the South Yellow Sea can be categorized into two types: northward drifting and northward-then-southward drifting. Spatially, Ulva prolifera blooms in the South Yellow Sea exhibit large-scale, continuous aggregation, whereas those in the North Yellow Sea are characterized by localized, scattered distributions. Ulva prolifera in the South Yellow Sea originates from the Subei Shoal, drifting northward with monsoon winds and ocean currents to accumulate along the southern coast of the Shandong Peninsula. In the North Yellow Sea, Ulva prolifera is mainly concentrated in areas such as the Jinshatan Beach in Yantai Development Zone and the estuary of the Guangdang River in Laishan District, with no large-scale drifting observed. (3) ITS gene sequencing reveals that Ulva prolifera in the North Yellow Sea along the Yantai coast belongs to a novel genetic strain (ITS JST3), which is distinctly different from the South Yellow Sea strain in terms of its light green, short, clustered morphology and underdeveloped air sac structures. By integrating macroscopic spatiotemporal patterns with microscopic genetic foundations, this study systematically demonstrates that the green tides in the South and North Yellow Sea are independent ecological events driven by different mechanisms, providing important insights for targeted regional prevention and control of green tides.
Since 2008, the South Yellow Sea has been persistently affected by green tide disasters caused by Ulva prolifera, while since 2009, the North Yellow Sea has frequently experienced large-scale macroalgal accumulations. The massive outbreaks of green tides severely damage marine ecosystems and threaten coastal ecological balance and economic structures. However, research on the differences in green tide outbreaks between the South Yellow Sea and North Yellow Sea remains limited. This study systematically compares the differences in Ulva prolifera between the two regions from two complementary dimensions—spatiotemporal distribution patterns and genetic basis—using multi-source remote sensing data, UAV monitoring, and molecular biology methods. The results indicate: (1) Significant differences in outbreak timing and scale. Ulva prolifera in the South Yellow Sea first appears in May, reaches its maximum coverage in mid-to-late June, and gradually disappears between July and August, with an entire life cycle lasting approximately 50–90 d. In contrast, Ulva prolifera in the North Yellow Sea is locally sourced, appearing in the coastal waters of Yantai from late June to early July and gradually disappearing in August. It exhibits smaller coverage areas and shorter duration compared to the South Yellow Sea. In recent years, the outbreak area in the South Yellow Sea has consistently exceeded 200 km2, while that in the North Yellow Sea has remained within
2025, 47(11): 121-130.
doi: 10.12284/hyxb2025132
Abstract:
Diatoms, as an important component of biofilms, can induce the settlement of invertebrates such as mussels. Extracellular polymeric substances (EPS) secreted by diatom play important roles in the induction process. However, the mechanism by which diatoms promote mussel settlement remains unclear. Diatom EPS typically consists of polysaccharides, proteins, nucleic acids, and other substances, with specific composition varying among species. To investigate the biological characteristics of different diatom biofilms and their ability to induce the settlement of Mytilus coruscus, two strains of diatoms were isolated and purified from natural biofilms in this study. After a cultivation period of 21 days, the chlorophyll a content and density of the diatom biofilm were measured. Moreover, its inducing activity on mussel settlement was investigated. Bound EPS from marine diatom biofilms was extracted using a hot solvent extraction method, and the content of polysaccharides and proteins was measured. The results showed that the biofilm of Navicula pelliculosa had high induction activity for mussel larvae settlement (63.8%), while the biofilm of Nitzschia traheaformis showed no difference from the blank group. Analysis by confocal laser scanning microscopy revealed that Navicula pelliculosa biofilm contained more extracellular polysaccharides, with water-insoluble polysaccharide components accounting for 51.49%. In contrast, Nitzschia traheaformis biofilms contained a higher proportion of protein components. This study preliminarily explored the biological characteristics of different marine diatom biofilms, providing theoretical support for understanding how diatom biofilm extracellular substances induce mussel larvae settlement.
Diatoms, as an important component of biofilms, can induce the settlement of invertebrates such as mussels. Extracellular polymeric substances (EPS) secreted by diatom play important roles in the induction process. However, the mechanism by which diatoms promote mussel settlement remains unclear. Diatom EPS typically consists of polysaccharides, proteins, nucleic acids, and other substances, with specific composition varying among species. To investigate the biological characteristics of different diatom biofilms and their ability to induce the settlement of Mytilus coruscus, two strains of diatoms were isolated and purified from natural biofilms in this study. After a cultivation period of 21 days, the chlorophyll a content and density of the diatom biofilm were measured. Moreover, its inducing activity on mussel settlement was investigated. Bound EPS from marine diatom biofilms was extracted using a hot solvent extraction method, and the content of polysaccharides and proteins was measured. The results showed that the biofilm of Navicula pelliculosa had high induction activity for mussel larvae settlement (63.8%), while the biofilm of Nitzschia traheaformis showed no difference from the blank group. Analysis by confocal laser scanning microscopy revealed that Navicula pelliculosa biofilm contained more extracellular polysaccharides, with water-insoluble polysaccharide components accounting for 51.49%. In contrast, Nitzschia traheaformis biofilms contained a higher proportion of protein components. This study preliminarily explored the biological characteristics of different marine diatom biofilms, providing theoretical support for understanding how diatom biofilm extracellular substances induce mussel larvae settlement.
2025, 47(11): 131-140.
doi: 10.12284/hyxb2025130
Abstract:
To comprehensively understand and analyze the current status and developmental trends of capture resource utilization in China’s coastal waters, this study constructs individual ARIMA models and their hybrid models with XGBoost, using fishery production data from 1980, 1985, 1991, 1997, 2003, 2009, and 2016 as temporal reference points. The model demonstrating the highest fitting accuracy was selected to forecast the marine catch in China's coastal waters from 2024 to 2028. The results indicate that the individual ARIMA models exhibited Mean Absolute Percentage Errors (MAPE) ranging from 0.11% to 12.12% and coefficients of determination (R2) between0.4561 and 0.9794 , while the hybrid models showed MAPE values of 0.12%−12.12% and R2 values of 0.7584 −0.9933 . Notably, the ARIMA(1, 2, 1) hybrid model constructed with 1980 capture data demonstrated optimal fitting performance, with MAPE and R2 values of 0.12% and 0.9933 , respectively. This model forecasts a marine catch of 9.5×106 t in China’s coastal waters from 2024 to 2028, indicating a gradual upward trend. The research findings reveal that the predictive accuracy of both model types initially decreases and subsequently increases with the extension of time series data, achieving optimal prediction accuracy and fitting degree with the longest time series. The hybrid model demonstrates significantly superior predictive accuracy compared to the individual ARIMA model. The forecasted catch values for 2024−2028 indicate an increase of less than 0.1%.
To comprehensively understand and analyze the current status and developmental trends of capture resource utilization in China’s coastal waters, this study constructs individual ARIMA models and their hybrid models with XGBoost, using fishery production data from 1980, 1985, 1991, 1997, 2003, 2009, and 2016 as temporal reference points. The model demonstrating the highest fitting accuracy was selected to forecast the marine catch in China's coastal waters from 2024 to 2028. The results indicate that the individual ARIMA models exhibited Mean Absolute Percentage Errors (MAPE) ranging from 0.11% to 12.12% and coefficients of determination (R2) between
2025, 47(11): 27-41.
doi: 10.12284/hyxb2025136
Abstract:
The rapid expansion of oxygen minimum zone (OMZ) in recent decades represents a microcosm of the global ocean deoxygenation problem, exerting profound impacts on marine ecosystems. This study systematically reviewed the ecological effects of OMZ from the perspectives of their linkages with biogeochemical cycles, biological activities, and climate change. Within OMZ, nitrogen cycling is primarily governed by denitrification and anammox, which act synergistically to drive nitrogen removal from the ocean. OMZ can enhance the efficiency of the biological pump, influence microbial carbon transformation, and alter the balance of the carbonate pump, thereby exerting significant control over the marine carbon cycle. Furthermore, the redox alterations induced by OMZ strongly affect the cycling of key elements such as phosphorus, iron, and sulfur. From an ecological standpoint, OMZ suppress diel vertical migration of zooplankton, impose physiological stress and habitat compression on nektonic organisms, alter the diversity, community structure, and physiological responses of benthic fauna, and restructure the metabolic pathways of microbial communities. OMZ also exhibit a bidirectional feedback relationship with climate change. Climate warming reduces oxygen solubility, enhances biological oxygen consumption, and intensifies stratification, collectively accelerating OMZ expansion. Conversely, OMZ can influence climate by altering oceanic carbon sequestration efficiency and enhancing the emission of greenhouse gases such as N2O and CH4. Future research should focus on elucidating the quantitative relationships between OMZ and various forms of carbon, assessing the ecological impacts of OMZ on biological activity, exploring their coupled interactions with climate change, and improving the methodologies of OMZ research. These ways will be essential for deepening our understanding of OMZ.
The rapid expansion of oxygen minimum zone (OMZ) in recent decades represents a microcosm of the global ocean deoxygenation problem, exerting profound impacts on marine ecosystems. This study systematically reviewed the ecological effects of OMZ from the perspectives of their linkages with biogeochemical cycles, biological activities, and climate change. Within OMZ, nitrogen cycling is primarily governed by denitrification and anammox, which act synergistically to drive nitrogen removal from the ocean. OMZ can enhance the efficiency of the biological pump, influence microbial carbon transformation, and alter the balance of the carbonate pump, thereby exerting significant control over the marine carbon cycle. Furthermore, the redox alterations induced by OMZ strongly affect the cycling of key elements such as phosphorus, iron, and sulfur. From an ecological standpoint, OMZ suppress diel vertical migration of zooplankton, impose physiological stress and habitat compression on nektonic organisms, alter the diversity, community structure, and physiological responses of benthic fauna, and restructure the metabolic pathways of microbial communities. OMZ also exhibit a bidirectional feedback relationship with climate change. Climate warming reduces oxygen solubility, enhances biological oxygen consumption, and intensifies stratification, collectively accelerating OMZ expansion. Conversely, OMZ can influence climate by altering oceanic carbon sequestration efficiency and enhancing the emission of greenhouse gases such as N2O and CH4. Future research should focus on elucidating the quantitative relationships between OMZ and various forms of carbon, assessing the ecological impacts of OMZ on biological activity, exploring their coupled interactions with climate change, and improving the methodologies of OMZ research. These ways will be essential for deepening our understanding of OMZ.
2025, 47(11): 42-56.
doi: 10.12284/hyxb2025146
Abstract:
The Changjiang Estuary-East China Sea (ECS) shelf system is one of the world's largest seasonal hypoxic zones, significantly influencing regional biogeochemical and ecological processes. However, the variation processes and controlling mechanisms during its autumn decay phase remain a limited understanding. Using multidisciplinary survey data collected from the ECS shelf in September 2017, this study documents the spatial distribution of the hypoxic zone and the characteristics of physical and chemical environment in autumn. And through analysis of hydrodynamic and biogeochemical processes, the controlling factors of hypoxia are further investigated. Results reveal a northeast-southwest oriented bottom dissolved oxygen (DO) minimum zone (DO mass concentration ＜ 4 mg/L, minimum of 2.52 mg/L) over the mid-shelf off Zhejiang within the 40−60 m isobath, showing a certain uplift tendency on its nearshore side. This hypoxic zone is basically within the influence area of the Kuroshio subsurface water (KSSW) nearshore branch (also known as the bottom water of the Taiwan Warm Current). The pycnocline and front structures near the outer edge of this branch restrict oxygen exchange between the hypoxic water and the overlying and surrounding water, providing hydrodynamic conditions that sustain the hypoxia into the autumn. The upwelling of the KSSW nearshore branch is identified as a major cause of the mid-water hypoxia over the inner shelf. Furthermore, the nutrients transported by southeastward offshore expansion of low-salinity water and upwelling at Zhejiang coast serve as a critical material foundation for in situ primary production, which partly modulates the intensity of the hypoxic zone. It is also shown that as the KSSW nearshore branch retreats southward and seaward in autumn, the core of the hypoxic zone moves correspondingly southward and offshore, eventually dissipating. This study provides an important insight into the decay processes and controlling mechanisms of the hypoxic zone in the Changjiang Estuary-ECS shelf system during autumn.
The Changjiang Estuary-East China Sea (ECS) shelf system is one of the world's largest seasonal hypoxic zones, significantly influencing regional biogeochemical and ecological processes. However, the variation processes and controlling mechanisms during its autumn decay phase remain a limited understanding. Using multidisciplinary survey data collected from the ECS shelf in September 2017, this study documents the spatial distribution of the hypoxic zone and the characteristics of physical and chemical environment in autumn. And through analysis of hydrodynamic and biogeochemical processes, the controlling factors of hypoxia are further investigated. Results reveal a northeast-southwest oriented bottom dissolved oxygen (DO) minimum zone (DO mass concentration ＜ 4 mg/L, minimum of 2.52 mg/L) over the mid-shelf off Zhejiang within the 40−60 m isobath, showing a certain uplift tendency on its nearshore side. This hypoxic zone is basically within the influence area of the Kuroshio subsurface water (KSSW) nearshore branch (also known as the bottom water of the Taiwan Warm Current). The pycnocline and front structures near the outer edge of this branch restrict oxygen exchange between the hypoxic water and the overlying and surrounding water, providing hydrodynamic conditions that sustain the hypoxia into the autumn. The upwelling of the KSSW nearshore branch is identified as a major cause of the mid-water hypoxia over the inner shelf. Furthermore, the nutrients transported by southeastward offshore expansion of low-salinity water and upwelling at Zhejiang coast serve as a critical material foundation for in situ primary production, which partly modulates the intensity of the hypoxic zone. It is also shown that as the KSSW nearshore branch retreats southward and seaward in autumn, the core of the hypoxic zone moves correspondingly southward and offshore, eventually dissipating. This study provides an important insight into the decay processes and controlling mechanisms of the hypoxic zone in the Changjiang Estuary-ECS shelf system during autumn.
2025, 47(11): 57-68.
doi: 10.12284/hyxb2025118
Abstract:
To elucidate nitrogen cycling processes and identify dominant nitrogen pollution sources in the Zhujiang River Estuary (ZRE), seawater samples were systematically collected from 40 stations in coastal waters (the western of Lingdingyang, Modaomen and Huangmaohai) during July 2020. By integrating hydrochemistry parameters and nitrogen-oxygen dual stable isotope (δ15N-\begin{document}${\mathrm{NO}}_3^- $\end{document} ![]()
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To elucidate nitrogen cycling processes and identify dominant nitrogen pollution sources in the Zhujiang River Estuary (ZRE), seawater samples were systematically collected from 40 stations in coastal waters (the western of Lingdingyang, Modaomen and Huangmaohai) during July 2020. By integrating hydrochemistry parameters and nitrogen-oxygen dual stable isotope (δ15N-
2025, 47(11): 69-83.
doi: 10.12284/hyxb2025112
Abstract:
In recent years, the rapid development of the marine economy has led to intensified environmental pollution in coastal areas. As an important aquaculture base, the water environment status of Xiangshan Bay directly affects local economic development and the ecological environment. This study established a BP neural network model based on four water quality monitoring indicators DO, COD, DIN and DIP to analyze the spatial distribution and variation characteristics of the water environmental carrying capacity in Xiangshan Bay from 2020 to 2023. Results show that the Water Environmental Carrying Capacity Index (WECCI) exhibited significant interannual fluctuations, reaching its peak in 2022. Spatially, the inner bay exhibited significantly lower water environmental carrying capacity than the outer bay, attributable to diminished hydrodynamic exchange capacity and prolonged pollutant retention duration. Additional analysis incorporating three water quality evaluation indices NQI, A, and E also indicated improved water environmental quality in 2022. Analysis of the 2022 drought conditions revealed that reduced river runoff and saltwater intrusion led to decreased nutrient concentrations, consequently enhancing the water environmental carrying capacity. Compared to traditional water quality index evaluation methods, the BP neural network model demonstrated superior performance in comprehensively assessing water environmental carrying capacity and its spatial heterogeneity.
In recent years, the rapid development of the marine economy has led to intensified environmental pollution in coastal areas. As an important aquaculture base, the water environment status of Xiangshan Bay directly affects local economic development and the ecological environment. This study established a BP neural network model based on four water quality monitoring indicators DO, COD, DIN and DIP to analyze the spatial distribution and variation characteristics of the water environmental carrying capacity in Xiangshan Bay from 2020 to 2023. Results show that the Water Environmental Carrying Capacity Index (WECCI) exhibited significant interannual fluctuations, reaching its peak in 2022. Spatially, the inner bay exhibited significantly lower water environmental carrying capacity than the outer bay, attributable to diminished hydrodynamic exchange capacity and prolonged pollutant retention duration. Additional analysis incorporating three water quality evaluation indices NQI, A, and E also indicated improved water environmental quality in 2022. Analysis of the 2022 drought conditions revealed that reduced river runoff and saltwater intrusion led to decreased nutrient concentrations, consequently enhancing the water environmental carrying capacity. Compared to traditional water quality index evaluation methods, the BP neural network model demonstrated superior performance in comprehensively assessing water environmental carrying capacity and its spatial heterogeneity.
2025, 47(11): 141-153.
doi: 10.12284/hyxb2025138
Abstract:
Water quality monitoring in marine ranching areas is of vital importance for their high-quality and sustainable development. Chlorophyll a (Chl a), an important indicator of phytoplankton biomass and water eutrophication, plays a key role in environmental assessment and risk management. Satellite remote sensing, characterized by rapid observation and wide spatiotemporal coverage, offers significant advantages. However, dedicated remote sensing products for marine ranching areas remain lacking, and aquaculture facilities can interfere with satellite signals, introducing errors in the remote sensing inversion of Chl a mass concentration. Using the Gouqi Island marine ranching area (a mussel aquaculture ranching area) in Shengsi, Zhejiang Province, as a case study, Chl a mass concentration inversion models for Landsat8 OLI images were constructed based on in situ data acquired during multiple cruises. The influence of aquaculture facilities on remote sensing reflectance was analyzed and effectively corrected. Validation results demonstrated the good performance of the inversion model. Using the corrected reflectance data, high-precision Chl a mass concentration products were retrieved for the mussel aquaculture ranching area and adjacent waters, and their spatiotemporal variations and potential influencing factors were examined. This study provides methodological support and a technical foundation for high-precision remote sensing monitoring of Chl a mass concentration in mussel aquaculture ranching areas.
Water quality monitoring in marine ranching areas is of vital importance for their high-quality and sustainable development. Chlorophyll a (Chl a), an important indicator of phytoplankton biomass and water eutrophication, plays a key role in environmental assessment and risk management. Satellite remote sensing, characterized by rapid observation and wide spatiotemporal coverage, offers significant advantages. However, dedicated remote sensing products for marine ranching areas remain lacking, and aquaculture facilities can interfere with satellite signals, introducing errors in the remote sensing inversion of Chl a mass concentration. Using the Gouqi Island marine ranching area (a mussel aquaculture ranching area) in Shengsi, Zhejiang Province, as a case study, Chl a mass concentration inversion models for Landsat8 OLI images were constructed based on in situ data acquired during multiple cruises. The influence of aquaculture facilities on remote sensing reflectance was analyzed and effectively corrected. Validation results demonstrated the good performance of the inversion model. Using the corrected reflectance data, high-precision Chl a mass concentration products were retrieved for the mussel aquaculture ranching area and adjacent waters, and their spatiotemporal variations and potential influencing factors were examined. This study provides methodological support and a technical foundation for high-precision remote sensing monitoring of Chl a mass concentration in mussel aquaculture ranching areas.
2025, 47(11): 154-166.
doi: 10.12284/hyxb2025128
Abstract:
Coral reef ecosystems are the most biologically diverse marine ecosystems on Earth and form the basis for coral reef research and conservation. Underwater monitoring is an important method for obtaining coral reef data. For underwater environments characterized by spectral complexity and high structural complexity, this paper proposes a residual SuperPoint underwater coral reef image registration method based on adaptive equalization sample. To address the issue of Visual Geometry Group (VGG) networks causing partial loss of high-frequency features and low feature extraction efficiency, a residual module is introduced into the encoding network to retain original features while reducing fitting difficulty and improving the accuracy of image feature point extraction. To address the issue of feature point extraction easily neglecting negative samples, we propose an adaptive equalization sample comparison loss function that incorporates a difficult negative sample mining mechanism. This improves parameter optimization efficiency, accelerates convergence speed, and enhances feature point extraction accuracy. Experiments conducted using the Hainan Jiajing Island underwater coral reef optical dataset, COCO, and HPatches datasets demonstrate that on the HPatches dataset, the residual SuperPoint algorithm achieves a feature point overlap rate of 61.7%, outperforming comparison algorithms by 4.8% to 23.1%. In underwater coral reef scenarios, Residual SuperPoint achieved a 11.8% improvement in structural similarity index measure (SSIM) and a 22.60% increase in mutual information (MI) compared to the classic SuperPoint at the image-level registration evaluation metrics, while maintaining comparable root mean square error (RMSE). Compared to other traditional algorithms, it demonstrated optimal performance in both structural similarity index and mutual information metrics, with suboptimal RMSE. The proposed method provides technical support for coral reef surveys, ecological monitoring, and related fields.
Coral reef ecosystems are the most biologically diverse marine ecosystems on Earth and form the basis for coral reef research and conservation. Underwater monitoring is an important method for obtaining coral reef data. For underwater environments characterized by spectral complexity and high structural complexity, this paper proposes a residual SuperPoint underwater coral reef image registration method based on adaptive equalization sample. To address the issue of Visual Geometry Group (VGG) networks causing partial loss of high-frequency features and low feature extraction efficiency, a residual module is introduced into the encoding network to retain original features while reducing fitting difficulty and improving the accuracy of image feature point extraction. To address the issue of feature point extraction easily neglecting negative samples, we propose an adaptive equalization sample comparison loss function that incorporates a difficult negative sample mining mechanism. This improves parameter optimization efficiency, accelerates convergence speed, and enhances feature point extraction accuracy. Experiments conducted using the Hainan Jiajing Island underwater coral reef optical dataset, COCO, and HPatches datasets demonstrate that on the HPatches dataset, the residual SuperPoint algorithm achieves a feature point overlap rate of 61.7%, outperforming comparison algorithms by 4.8% to 23.1%. In underwater coral reef scenarios, Residual SuperPoint achieved a 11.8% improvement in structural similarity index measure (SSIM) and a 22.60% increase in mutual information (MI) compared to the classic SuperPoint at the image-level registration evaluation metrics, while maintaining comparable root mean square error (RMSE). Compared to other traditional algorithms, it demonstrated optimal performance in both structural similarity index and mutual information metrics, with suboptimal RMSE. The proposed method provides technical support for coral reef surveys, ecological monitoring, and related fields.
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