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Abstract:
To ensure the structural stability of subsea infrastructure under prolonged exposure to marine dynamic loads (e.g., waves, ocean currents, and seismic activities), it is essential to understand the rheological behavior of deep-sea soft clay in the surface layer of the seabed. In this study, deep-sea soft clay was selected as the research subject, and dynamic shear tests were conducted under varying salinity and temperature conditions using a strain-controlled rheometer. The variation patterns of storage modulus (G'), loss modulus (G''), and cross-strain were systematically analyzed. By integrating liquid and plastic limit tests and free settlement tests with, the influence mechanisms of salinity and temperature on the rheological properties of deep-sea soft clay were explored. The experimental results indicate that as the concentration of NaCl solution increases and temperature decreases, the liquid limit, plastic limit, settlement volume, G', G'', and cross-strain of deep-sea soft clay all exhibit an upward trend. This behavior is closely associated with the formation of a flocculated clay structure and the reduction in thickness of the double electric layer. Under increasing shear strain, deep-sea soft clay demonstrates a distinct two-step yielding behavior: the first yield occurs during the initial stage of modulus reduction, corresponding to the breakdown of the flocculated network; the second yield appears in the subsequent modulus reduction phase, associated with the disruption of the shear-induced hollow cylindrical structure. The plateau phase between the two yielding stages reflects the shear resistance provided by the hollow cylindrical structure. The findings of this study provide a scientific foundation for the design and stability evaluation of engineering foundations in ultra-deep marine environments.
To ensure the structural stability of subsea infrastructure under prolonged exposure to marine dynamic loads (e.g., waves, ocean currents, and seismic activities), it is essential to understand the rheological behavior of deep-sea soft clay in the surface layer of the seabed. In this study, deep-sea soft clay was selected as the research subject, and dynamic shear tests were conducted under varying salinity and temperature conditions using a strain-controlled rheometer. The variation patterns of storage modulus (G'), loss modulus (G''), and cross-strain were systematically analyzed. By integrating liquid and plastic limit tests and free settlement tests with, the influence mechanisms of salinity and temperature on the rheological properties of deep-sea soft clay were explored. The experimental results indicate that as the concentration of NaCl solution increases and temperature decreases, the liquid limit, plastic limit, settlement volume, G', G'', and cross-strain of deep-sea soft clay all exhibit an upward trend. This behavior is closely associated with the formation of a flocculated clay structure and the reduction in thickness of the double electric layer. Under increasing shear strain, deep-sea soft clay demonstrates a distinct two-step yielding behavior: the first yield occurs during the initial stage of modulus reduction, corresponding to the breakdown of the flocculated network; the second yield appears in the subsequent modulus reduction phase, associated with the disruption of the shear-induced hollow cylindrical structure. The plateau phase between the two yielding stages reflects the shear resistance provided by the hollow cylindrical structure. The findings of this study provide a scientific foundation for the design and stability evaluation of engineering foundations in ultra-deep marine environments.
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Abstract:
Mesoscale eddies, as an important phenomenon in the ocean, significantly influence the distribution of water masses and material transport within their regions. Obtaining the three-dimensional distribution of mesoscale eddies is of great significance for marine resource development, maritime transportation, and military applications. However, existing intelligent identification models for mesoscale eddies typically rely on sea surface data such as sea surface height and sea surface temperature, and are only used to identify mesoscale eddies at the ocean surface. This paper proposes a multi-scale feature adaptive fusion model based on multi-source data, including flow fields, temperature, and salinity. In the encoder stage, the model uses a multi-branch structure to independently extract features from the multi-source data. In the decoder stage, an attention mechanism is employed to perform weighted adaptive fusion of multi-layer features from each branch. During training, a hybrid loss function combining classification probability gradient loss and Dice coefficient loss is used to improve the identification accuracy of the model. Experimental validation is conducted using data from the South China Sea region. The model achieves a global accuracy of 98.49%, an average Dice coefficient of0.8777 , and a weighted Dice coefficient of 0.8225 , demonstrating the model’s effectiveness and high accuracy in identifying the distribution of mesoscale eddies at both the sea surface and various water depths.
Mesoscale eddies, as an important phenomenon in the ocean, significantly influence the distribution of water masses and material transport within their regions. Obtaining the three-dimensional distribution of mesoscale eddies is of great significance for marine resource development, maritime transportation, and military applications. However, existing intelligent identification models for mesoscale eddies typically rely on sea surface data such as sea surface height and sea surface temperature, and are only used to identify mesoscale eddies at the ocean surface. This paper proposes a multi-scale feature adaptive fusion model based on multi-source data, including flow fields, temperature, and salinity. In the encoder stage, the model uses a multi-branch structure to independently extract features from the multi-source data. In the decoder stage, an attention mechanism is employed to perform weighted adaptive fusion of multi-layer features from each branch. During training, a hybrid loss function combining classification probability gradient loss and Dice coefficient loss is used to improve the identification accuracy of the model. Experimental validation is conducted using data from the South China Sea region. The model achieves a global accuracy of 98.49%, an average Dice coefficient of
, Available online
Abstract:
In the context of global warming, the intensity of typhoon activity has exhibited an increasing trend. Typhoons are typically associated with heavy rainfall and strong winds, which can result in significant alterations to the nearshore hydrodynamical environment over a short period, thereby triggering pronounced ecological responses. In this paper, a three-dimensional hydro-biogeochemical model was constructed based on the unstructured-grid, Finite Volume Community Ocean Model (FVCOM) to study the impact of Typhoon Lekima (No. 1909) on residual currents, salinity, water quality and nutrient transport in Laizhou Bay (LZB). Sensitivity experiments were conducted to quantify the contributions of river inputs and winds to water quality during the passage of Lekima. The results show that a strong southwest coastal current developed south of the Yellow River Estuary (YRE), and the pattern of residual currents in LZB was characterized by westward inflow and eastward outflow. The heavy rainfall led to a marked increase in freshwater and dissolved inorganic nitrogen (DIN) fluxes from the surrounding rivers into the bay. Consequently, the surface salinity near the YRE and the southwest coast of LZB decreased rapidly, while DIN concentrations increased. The surface salinity reached the minimum value of 25.91 PSU two days after the passage of Lekima, which was 1.57 PSU lower than pre-typhoon levels. Conversely, surface DIN concentrations peaked at 0.61 mg/L eight days after the passage of Lekima, approximately 1.51 times higher than pre-typhoon levels. Calculations of DIN fluxes through the bay mouth section revealed that the DIN exchange between LZB and the Bohai Sea (BS) occurred in two distinct phases: strong inflow and outflow during the passage of Lekima, with a total of 1.88 kt of DIN transported from LZB to the BS. The contributions of river inputs and winds to water quality were 70.15% and −18.47%, respectively. River input was identified as the primary factor of changes in water quality in LZB, while the direction of residual currents was landward due to the force of typhoon winds, which was adverse to the transport of DIN from LZB to the BS. This study underscores the crucial role of typhoons in regulating water quality changes in coastal bays and provides scientific support for sustainable development and ecological protection in coastal regions.
In the context of global warming, the intensity of typhoon activity has exhibited an increasing trend. Typhoons are typically associated with heavy rainfall and strong winds, which can result in significant alterations to the nearshore hydrodynamical environment over a short period, thereby triggering pronounced ecological responses. In this paper, a three-dimensional hydro-biogeochemical model was constructed based on the unstructured-grid, Finite Volume Community Ocean Model (FVCOM) to study the impact of Typhoon Lekima (No. 1909) on residual currents, salinity, water quality and nutrient transport in Laizhou Bay (LZB). Sensitivity experiments were conducted to quantify the contributions of river inputs and winds to water quality during the passage of Lekima. The results show that a strong southwest coastal current developed south of the Yellow River Estuary (YRE), and the pattern of residual currents in LZB was characterized by westward inflow and eastward outflow. The heavy rainfall led to a marked increase in freshwater and dissolved inorganic nitrogen (DIN) fluxes from the surrounding rivers into the bay. Consequently, the surface salinity near the YRE and the southwest coast of LZB decreased rapidly, while DIN concentrations increased. The surface salinity reached the minimum value of 25.91 PSU two days after the passage of Lekima, which was 1.57 PSU lower than pre-typhoon levels. Conversely, surface DIN concentrations peaked at 0.61 mg/L eight days after the passage of Lekima, approximately 1.51 times higher than pre-typhoon levels. Calculations of DIN fluxes through the bay mouth section revealed that the DIN exchange between LZB and the Bohai Sea (BS) occurred in two distinct phases: strong inflow and outflow during the passage of Lekima, with a total of 1.88 kt of DIN transported from LZB to the BS. The contributions of river inputs and winds to water quality were 70.15% and −18.47%, respectively. River input was identified as the primary factor of changes in water quality in LZB, while the direction of residual currents was landward due to the force of typhoon winds, which was adverse to the transport of DIN from LZB to the BS. This study underscores the crucial role of typhoons in regulating water quality changes in coastal bays and provides scientific support for sustainable development and ecological protection in coastal regions.
, Available online
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 (UV) 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 (UV) 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.
, Available online
Abstract:
To enhance the accuracy and reliability of extreme wave height inference in ocean engineering, this study systematically compares the applicability and uncertainty of the Annual Maxima (AM) method and the Peak Over Threshold (POT) method. Utilizing reanalysis wave data from two representative sites in Hangzhou Bay, annual maxima series and POT samples were constructed. These were modeled using the Generalized Extreme Value (GEV) distribution and the Generalized Pareto Distribution (GPD), respectively; for the POT method, threshold selection was optimized via a tail least squares error (TLSE) criterion. Confidence intervals for model parameters and return period level wave height estimates were further quantified using both the Delta method and the Bootstrap method. The results demonstrate that for high return periods, the POT method yields higher wave height estimates with narrower confidence intervals, rendering it more suitable for engineering design scenarios sensitive to extreme events. In uncertainty analysis, the Bootstrap method more comprehensively captures model uncertainty compared to the Delta method. This work establishes a more robust analytical framework and inferential basis for extreme wave height modeling.
To enhance the accuracy and reliability of extreme wave height inference in ocean engineering, this study systematically compares the applicability and uncertainty of the Annual Maxima (AM) method and the Peak Over Threshold (POT) method. Utilizing reanalysis wave data from two representative sites in Hangzhou Bay, annual maxima series and POT samples were constructed. These were modeled using the Generalized Extreme Value (GEV) distribution and the Generalized Pareto Distribution (GPD), respectively; for the POT method, threshold selection was optimized via a tail least squares error (TLSE) criterion. Confidence intervals for model parameters and return period level wave height estimates were further quantified using both the Delta method and the Bootstrap method. The results demonstrate that for high return periods, the POT method yields higher wave height estimates with narrower confidence intervals, rendering it more suitable for engineering design scenarios sensitive to extreme events. In uncertainty analysis, the Bootstrap method more comprehensively captures model uncertainty compared to the Delta method. This work establishes a more robust analytical framework and inferential basis for extreme wave height modeling.
, Available online , doi: 10.12284/hyxb2025000
Abstract:
Ocean buoy observations serve as a vital means of acquiring data for marine research. However, direct measurements from buoys are subject to significant biases induced by factors such as sensor baseline drift, biofouling, and seawater corrosion, necessitating rigorous bias correction to ensure data reliability. While numerous quality control (QC) schemes for physical oceanographic parameters from buoy data have been extensively studied and reported, robust and practical sensor QC measures for more complex and variable chemical parameters remain lacking. To address this gap, this study analyzed 90-day laboratory monitoring data for parameters including dissolved oxygen, chlorophyll concentration, pH, and partial pressure of CO2 (pCO2). The analysis revealed that the drift bias in these monitored parameters exhibits a strong linear correlation with fundamental sensor parameters such as conductivity and sensor output voltage and with biological factors to varying degrees. Building upon these findings, we developed a drift bias correction method based on machine learning algorithm to fit the nonlinear relationships between drift bias and fundamental sensor parameters. This method effectively validates buoy sensor data for chemical parameters. Application of this method to observational data across different parameters significantly reduces the deviation between drifted data and true values. It thus provides a novel QC approach for achieving sustained, stable, and high-quality acquisition of marine chemical parameter data from buoy observations.
Ocean buoy observations serve as a vital means of acquiring data for marine research. However, direct measurements from buoys are subject to significant biases induced by factors such as sensor baseline drift, biofouling, and seawater corrosion, necessitating rigorous bias correction to ensure data reliability. While numerous quality control (QC) schemes for physical oceanographic parameters from buoy data have been extensively studied and reported, robust and practical sensor QC measures for more complex and variable chemical parameters remain lacking. To address this gap, this study analyzed 90-day laboratory monitoring data for parameters including dissolved oxygen, chlorophyll concentration, pH, and partial pressure of CO2 (pCO2). The analysis revealed that the drift bias in these monitored parameters exhibits a strong linear correlation with fundamental sensor parameters such as conductivity and sensor output voltage and with biological factors to varying degrees. Building upon these findings, we developed a drift bias correction method based on machine learning algorithm to fit the nonlinear relationships between drift bias and fundamental sensor parameters. This method effectively validates buoy sensor data for chemical parameters. Application of this method to observational data across different parameters significantly reduces the deviation between drifted data and true values. It thus provides a novel QC approach for achieving sustained, stable, and high-quality acquisition of marine chemical parameter data from buoy observations.
, Available online , 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 was a hydrophobic transmembrane protein, containing 12 transmembrane domains, belonging to the Rhesus-type ammonia transporter. Its amino acid sequence shares 44.14% identity with Homo sapiens ammonia transporter gene 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 is 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 PdRhp-1.
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
, Available online , 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.
, Available online
Abstract:
The Asian continental marginal seas are among the most representative “source-to-sink” coupled systems globally. Understanding their organic carbon (OC) burial processes under the context of Quaternary climate change is of great significance for unraveling the evolution of the global carbon cycle. This study provides a comprehensive review of the sources, burial flux variations, and driving mechanisms of OC in sediments from major Asian marginal seas. The results indicate that during glacial periods, most marginal seas exhibit increased OC content and burial fluxes. In many regions, total organic carbon (TOC) content, organic carbon isotopic composition (δ13Corg), and TOC/total nitrogen (TOC/TN) ratios display cyclic variations on orbital timescales. Mechanistically, sea-level changes regulate the process and intensity of terrigenous material delivery, monsoon systems influence watershed erosion and water column structure, while ocean currents and the distribution of oxygen minimum zones (OMZs) jointly control the spatial variability of carbon sink efficiency. Sedimentary records from representative sites suggest that increased terrigenous input, OMZ development, or higher sedimentation rates during glacials often enhance the preservation and burial of OC. However, in certain high-latitude or deep-water regions (e.g., the Sea of Okhotsk and the Japan Sea), reduced marine productivity during glacials may lower OC burial efficiency. Furthermore, this study employs combined proxies such as δ13Corg and TOC/TN ratios to quantify the mixing characteristics and evolutionary history of different OC sources, and estimates of OC burial fluxes reveal the differential responses of regional carbon sinks to glacial–interglacial cycles. Despite significant progress, challenges remain in end-member construction, proxy standardization, and high-resolution spatiotemporal reconstructions. Future research should focus on cross-regional comparisons, coupled mechanistic modeling, and refined chronological controls. These efforts will enhance our understanding of the evolution of carbon sinks in Asian marginal seas and their geological roles in the global carbon cycle, contributing to more accurate predictions of oceanic carbon sink dynamics under future climate change scenarios.
The Asian continental marginal seas are among the most representative “source-to-sink” coupled systems globally. Understanding their organic carbon (OC) burial processes under the context of Quaternary climate change is of great significance for unraveling the evolution of the global carbon cycle. This study provides a comprehensive review of the sources, burial flux variations, and driving mechanisms of OC in sediments from major Asian marginal seas. The results indicate that during glacial periods, most marginal seas exhibit increased OC content and burial fluxes. In many regions, total organic carbon (TOC) content, organic carbon isotopic composition (δ13Corg), and TOC/total nitrogen (TOC/TN) ratios display cyclic variations on orbital timescales. Mechanistically, sea-level changes regulate the process and intensity of terrigenous material delivery, monsoon systems influence watershed erosion and water column structure, while ocean currents and the distribution of oxygen minimum zones (OMZs) jointly control the spatial variability of carbon sink efficiency. Sedimentary records from representative sites suggest that increased terrigenous input, OMZ development, or higher sedimentation rates during glacials often enhance the preservation and burial of OC. However, in certain high-latitude or deep-water regions (e.g., the Sea of Okhotsk and the Japan Sea), reduced marine productivity during glacials may lower OC burial efficiency. Furthermore, this study employs combined proxies such as δ13Corg and TOC/TN ratios to quantify the mixing characteristics and evolutionary history of different OC sources, and estimates of OC burial fluxes reveal the differential responses of regional carbon sinks to glacial–interglacial cycles. Despite significant progress, challenges remain in end-member construction, proxy standardization, and high-resolution spatiotemporal reconstructions. Future research should focus on cross-regional comparisons, coupled mechanistic modeling, and refined chronological controls. These efforts will enhance our understanding of the evolution of carbon sinks in Asian marginal seas and their geological roles in the global carbon cycle, contributing to more accurate predictions of oceanic carbon sink dynamics under future climate change scenarios.
, Available online
Abstract:
The influence of suspended particulate matters (SPM) on denitrifying metabolism and potential of nearshore waters were investigated in the sea area outside Dagu River estuary and southern mouth of Jiaozhou Bay based on 15N-isotopic tracing incubation experiments. Sediment cores and overlying waters were collected from two sampling sites and then incubated under in situ conditions and simulated SPM gradient (i.e., 50 mg/L, 100 mg/L, 150 mg/L, 200 mg/L, 300 mg/L and 400 mg/L in setting concentration). Detection of denitrification rates combined with relative abundances of narG and nirS genes measurement were conducted to reveal the denitrification potential. The results showed that significant denitrification occurred in all incubations. Under SPM gradient simulated condition, the denitrifying rates as well as narG and nirS gene abundances increased with SPM concentrations, and the abundance of particle-associated denitrifying bacteria probably played a dominated role on potential enhancement, implying that SPM should act as important media on promoting denitrification potential in the Jiaozhou Bay waters. The variance between two study sites was obvious with denitrification rate measured in estuary area being higher than that in southern mouth, while the functional gene abundances just the opposite. It could be well explained by the composition and grain size difference of the SPM, indicating a complicated regulation of SPM to the denitrification potential in Jiaozhou Bay waters. This study suggests that SPM will expand the spatial activity of denitrifying metabolism and then more release the denitrification potential in the nearshore ecosystem, which is ecologically meaningful for the relief of eutrophication level and risk in coastal environments.
The influence of suspended particulate matters (SPM) on denitrifying metabolism and potential of nearshore waters were investigated in the sea area outside Dagu River estuary and southern mouth of Jiaozhou Bay based on 15N-isotopic tracing incubation experiments. Sediment cores and overlying waters were collected from two sampling sites and then incubated under in situ conditions and simulated SPM gradient (i.e., 50 mg/L, 100 mg/L, 150 mg/L, 200 mg/L, 300 mg/L and 400 mg/L in setting concentration). Detection of denitrification rates combined with relative abundances of narG and nirS genes measurement were conducted to reveal the denitrification potential. The results showed that significant denitrification occurred in all incubations. Under SPM gradient simulated condition, the denitrifying rates as well as narG and nirS gene abundances increased with SPM concentrations, and the abundance of particle-associated denitrifying bacteria probably played a dominated role on potential enhancement, implying that SPM should act as important media on promoting denitrification potential in the Jiaozhou Bay waters. The variance between two study sites was obvious with denitrification rate measured in estuary area being higher than that in southern mouth, while the functional gene abundances just the opposite. It could be well explained by the composition and grain size difference of the SPM, indicating a complicated regulation of SPM to the denitrification potential in Jiaozhou Bay waters. This study suggests that SPM will expand the spatial activity of denitrifying metabolism and then more release the denitrification potential in the nearshore ecosystem, which is ecologically meaningful for the relief of eutrophication level and risk in coastal environments.
, Available online
Abstract:
To elucidate nitrogen cycling processes and identify dominant nitrogen pollution sources in the Pearl River Estuary (PRE), 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 Pearl River Estuary (PRE), 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-
, Available online
Abstract:
Transparent exopolymer particles (TEP) are a special class of extracellular polymeric substances which is ubiquitous in seawater, characterized by transparency; high carbon content and stickiness; with colloidal and particulate characteristics, play a significant role in marine carbon transportation. In this review, we describe the Biogeochemistry characteristic and contribution to carbon transportation of Transparent Exopolymer Particles (TEP) in the ocean systematically. Marine TEP are amorphous, their size is variable, mainly generated by self-assembly of precursors which is released by phytoplankton and removed from ocean through processes such as biological metabolism, air-sea exchange and settlement, their abundance and distribution driven by the activity of organisms such as phytoplankton such as phytoplankton and bacteria, as well as the physicochemical environment and hydrodynamic processes. TEP concentrations in coastal waters exhibit considerable variability(0-14,800 μg XG eq L-1) and decrease with increasing offshore distance and closely related to productivity, thus demonstrating marked seasonal variations; In the open ocean, TEP concentrations are usually lower (0-200 μg XG eq L-1) and decrease with depth in epipelagic waters, while remaining relatively steady in Mesopelagic and Bathypelagic waters. As an important component of particulate organic carbon (POC), TEP typically account for less than 40% of the POC pool and its sinking flux in coastal areas, but can contribute more than 50% in the open ocean. In addition to altering particle sinking rates and affecting vertical carbon transport, TEP can also mediate air-sea carbon exchange through enrichment in the sea surface microlayer, though the underlying mechanisms and their significance in carbon transport require further investigation. Future research should focus on improving quantitative detection methods for TEP, analyzing their composition and morphology, and optimizing carbon conversion factors. to better understand the biogeochemical behaviors of TEP and their mechanisms in marine carbon transportation.
Transparent exopolymer particles (TEP) are a special class of extracellular polymeric substances which is ubiquitous in seawater, characterized by transparency; high carbon content and stickiness; with colloidal and particulate characteristics, play a significant role in marine carbon transportation. In this review, we describe the Biogeochemistry characteristic and contribution to carbon transportation of Transparent Exopolymer Particles (TEP) in the ocean systematically. Marine TEP are amorphous, their size is variable, mainly generated by self-assembly of precursors which is released by phytoplankton and removed from ocean through processes such as biological metabolism, air-sea exchange and settlement, their abundance and distribution driven by the activity of organisms such as phytoplankton such as phytoplankton and bacteria, as well as the physicochemical environment and hydrodynamic processes. TEP concentrations in coastal waters exhibit considerable variability(0-14,800 μg XG eq L-1) and decrease with increasing offshore distance and closely related to productivity, thus demonstrating marked seasonal variations; In the open ocean, TEP concentrations are usually lower (0-200 μg XG eq L-1) and decrease with depth in epipelagic waters, while remaining relatively steady in Mesopelagic and Bathypelagic waters. As an important component of particulate organic carbon (POC), TEP typically account for less than 40% of the POC pool and its sinking flux in coastal areas, but can contribute more than 50% in the open ocean. In addition to altering particle sinking rates and affecting vertical carbon transport, TEP can also mediate air-sea carbon exchange through enrichment in the sea surface microlayer, though the underlying mechanisms and their significance in carbon transport require further investigation. Future research should focus on improving quantitative detection methods for TEP, analyzing their composition and morphology, and optimizing carbon conversion factors. to better understand the biogeochemical behaviors of TEP and their mechanisms in marine carbon transportation.
, Available online , doi: 10.12284/hyxb2025100
Abstract:
Symbiodiniaceae are indispensable partners in the coral symbiotic system, and different species exhibit varying sensitivities to environmental stress, thereby influencing the environmental adaptability of their coral hosts. This study investigates the stress response patterns of two widely distributed coral symbiotic Symbiodiniaceae species—environmentally sensitive Cladocopium goreaui and environmentally tolerant Durusdinium trenchii—under heat stress from the perspective of lipid metabolism. The results showed that heat stress significantly affected their cell density, photosynthetic pigment content, photochemical efficiency of photosystem II (Fv/Fm), and antioxidant activity, with statistically significant differences (P < 0.05). Lipidomics revealed that lipid-differentiated metabolites such as phosphatidylcholine, triglycerides, phosphatidylethanolamine and lysophosphatidylcholine were significantly enriched in glycerophospholipid metabolism, triglyceride metabolism, and polyunsaturated fatty acid-related metabolic pathways in response to heat stress in C. goreaui and D. trenchii. Notably, the two species exhibited significant differences in sphingolipid metabolism: D. trenchii downregulated ceramide levels to reduce oxidative stress damage, regulate autophagy, and adapt to changes in membrane fluidity, whereas C. goreaui primarily upregulated lipid molecules rich in polyunsaturated fatty acids to maintain membrane stability and regulate signal transduction. A deeper understanding of the lipid metabolic stress response mechanisms of Symbiodiniaceae with different environmental sensitivities under heat stress provides new insights into enhancing coral adaptability to environmental changes from a symbiotic partner perspective.
Symbiodiniaceae are indispensable partners in the coral symbiotic system, and different species exhibit varying sensitivities to environmental stress, thereby influencing the environmental adaptability of their coral hosts. This study investigates the stress response patterns of two widely distributed coral symbiotic Symbiodiniaceae species—environmentally sensitive Cladocopium goreaui and environmentally tolerant Durusdinium trenchii—under heat stress from the perspective of lipid metabolism. The results showed that heat stress significantly affected their cell density, photosynthetic pigment content, photochemical efficiency of photosystem II (Fv/Fm), and antioxidant activity, with statistically significant differences (P < 0.05). Lipidomics revealed that lipid-differentiated metabolites such as phosphatidylcholine, triglycerides, phosphatidylethanolamine and lysophosphatidylcholine were significantly enriched in glycerophospholipid metabolism, triglyceride metabolism, and polyunsaturated fatty acid-related metabolic pathways in response to heat stress in C. goreaui and D. trenchii. Notably, the two species exhibited significant differences in sphingolipid metabolism: D. trenchii downregulated ceramide levels to reduce oxidative stress damage, regulate autophagy, and adapt to changes in membrane fluidity, whereas C. goreaui primarily upregulated lipid molecules rich in polyunsaturated fatty acids to maintain membrane stability and regulate signal transduction. A deeper understanding of the lipid metabolic stress response mechanisms of Symbiodiniaceae with different environmental sensitivities under heat stress provides new insights into enhancing coral adaptability to environmental changes from a symbiotic partner perspective.
, Available online , doi: 10.12284/hyxb2025106
Abstract:
To evaluate the toxicological effects of polystyrene microplastics (PS-MPs) on the intestinal health of Sebastiscus marmoratus, individuals were exposed to PS-MP solutions at concentrations of 0, 1, and 10 mg/L for 21 days. A combination of analytical approaches, including enrichment analysis, histological examination, transcriptomic profiling, and 16S rRNA gene sequencing, was employed to assess alterations in intestinal morphology, gene expression, and microbial community composition. The results demonstrated a time-dependent accumulation of PS-MPs in the intestines, with concentrations reaching 16.20 μg/g by day 7. Histopathological analysis revealed dose-dependent intestinal damage: at 1 mg/L, necrosis, detachment, and vacuolar degeneration of mucosal cells were observed; at 10 mg/L, severe villus atrophy, necrosis, vacuolization, and significant reductions in intestinal wall thickness, muscle layer thickness, and villus length and width were evident. Transcriptomic analysis identified 313 and 169 differentially expressed genes (DEGs) after 7 and 21 days of exposure, respectively. KEGG pathway enrichment revealed that DEGs at day 7 were primarily involved in the p53 signaling pathway, starch and sucrose metabolism, and Toll-like receptor signaling. By day 21, enrichment was observed in pathways related to steroid biosynthesis, arachidonic acid metabolism, and NOD-like receptor signaling. Although no significant changes in microbial composition were detected at the phylum level, notable increases in the relative abundances of Fusobacteriaceae, Cetobacterium, Vibrionaceae, and Prevotella were observed, potentially indicating enhanced intestinal barrier repair and anti-inflammatory responses. In conclusion, PS-MP exposure resulted in structural damage to intestinal tissues, disruption of the mucosal barrier, and inflammatory responses in S. marmoratus, ultimately compromising organismal health.
To evaluate the toxicological effects of polystyrene microplastics (PS-MPs) on the intestinal health of Sebastiscus marmoratus, individuals were exposed to PS-MP solutions at concentrations of 0, 1, and 10 mg/L for 21 days. A combination of analytical approaches, including enrichment analysis, histological examination, transcriptomic profiling, and 16S rRNA gene sequencing, was employed to assess alterations in intestinal morphology, gene expression, and microbial community composition. The results demonstrated a time-dependent accumulation of PS-MPs in the intestines, with concentrations reaching 16.20 μg/g by day 7. Histopathological analysis revealed dose-dependent intestinal damage: at 1 mg/L, necrosis, detachment, and vacuolar degeneration of mucosal cells were observed; at 10 mg/L, severe villus atrophy, necrosis, vacuolization, and significant reductions in intestinal wall thickness, muscle layer thickness, and villus length and width were evident. Transcriptomic analysis identified 313 and 169 differentially expressed genes (DEGs) after 7 and 21 days of exposure, respectively. KEGG pathway enrichment revealed that DEGs at day 7 were primarily involved in the p53 signaling pathway, starch and sucrose metabolism, and Toll-like receptor signaling. By day 21, enrichment was observed in pathways related to steroid biosynthesis, arachidonic acid metabolism, and NOD-like receptor signaling. Although no significant changes in microbial composition were detected at the phylum level, notable increases in the relative abundances of Fusobacteriaceae, Cetobacterium, Vibrionaceae, and Prevotella were observed, potentially indicating enhanced intestinal barrier repair and anti-inflammatory responses. In conclusion, PS-MP exposure resulted in structural damage to intestinal tissues, disruption of the mucosal barrier, and inflammatory responses in S. marmoratus, ultimately compromising organismal health.
, Available online , doi: 10.12284/hyxb2025104
Abstract:
The coastal estuarine ecosystem is a unique ecosystem formed at the confluence of rivers and oceans. It has high primary productivity, can provide food and habitat for many organisms, and plays an important role in maintaining the stability of ecosystem structure. In order to explore the temporal and spatial dynamics of phytoplankton community and its environmental impact factors in Liuqing River Bay, four cruises were carried out at seven sampling sites in Liuqing River Bay in winter (March), spring (May), summer (August) and autumn (October) of 2023. The results showed that a total of 97 species of phytoplankton belonging to 56 genera and 3 phyla were identified in the four cruises. The phytoplankton community structure was mainly composed of diatoms and dinoflagellates. The cell abundance of phytoplankton in Liuqing River Bay has obvious temporal and spatial dynamic changes. From the time dimension, the average abundance of phytoplankton in the four seasons from high to low is winter, autumn, summer and spring.In terms of spatial distribution, the phytoplankton abundance in Liuqing Bay reflects seasonal spatial distribution differences. The high abundance areas in spring, autumn and winter are concentrated in the northeast coastal waters, which are mainly driven by terrestrial input. The low abundance area is continuously distributed in the northwest sea area, which is mainly related to turbulent mixing. The overall spatial pattern is characterized by near-shore enrichment and offshore decline. The dominant species mainly include Cladophora in Bacillariophyta, Coscinodiscus in Ophiales, Chaetoceros capillipes, Chaetoceros spiralis, Coscinodiscus astromboides, Coscinodiscus grijsii and Chaetoceros capillipes, Chaetoceros tricornis in Pyrrophyta. The biodiversity in summer and autumn was significantly higher than that in spring and winter. The results of redundancy analysis showed that salinity, DIN (dissolved inorganic nitrogen) and DIP (dissolved inorganic phosphorus) were the key environmental factors affecting the changes of phytoplankton community structure.
The coastal estuarine ecosystem is a unique ecosystem formed at the confluence of rivers and oceans. It has high primary productivity, can provide food and habitat for many organisms, and plays an important role in maintaining the stability of ecosystem structure. In order to explore the temporal and spatial dynamics of phytoplankton community and its environmental impact factors in Liuqing River Bay, four cruises were carried out at seven sampling sites in Liuqing River Bay in winter (March), spring (May), summer (August) and autumn (October) of 2023. The results showed that a total of 97 species of phytoplankton belonging to 56 genera and 3 phyla were identified in the four cruises. The phytoplankton community structure was mainly composed of diatoms and dinoflagellates. The cell abundance of phytoplankton in Liuqing River Bay has obvious temporal and spatial dynamic changes. From the time dimension, the average abundance of phytoplankton in the four seasons from high to low is winter, autumn, summer and spring.In terms of spatial distribution, the phytoplankton abundance in Liuqing Bay reflects seasonal spatial distribution differences. The high abundance areas in spring, autumn and winter are concentrated in the northeast coastal waters, which are mainly driven by terrestrial input. The low abundance area is continuously distributed in the northwest sea area, which is mainly related to turbulent mixing. The overall spatial pattern is characterized by near-shore enrichment and offshore decline. The dominant species mainly include Cladophora in Bacillariophyta, Coscinodiscus in Ophiales, Chaetoceros capillipes, Chaetoceros spiralis, Coscinodiscus astromboides, Coscinodiscus grijsii and Chaetoceros capillipes, Chaetoceros tricornis in Pyrrophyta. The biodiversity in summer and autumn was significantly higher than that in spring and winter. The results of redundancy analysis showed that salinity, DIN (dissolved inorganic nitrogen) and DIP (dissolved inorganic phosphorus) were the key environmental factors affecting the changes of phytoplankton community structure.
, Available online
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.
, Available online , doi: 10.12284/hyxb2025108
Abstract:
Global warming and extreme thermal events have induced widespread coral bleaching, leading to the rapid degradation of coral reef ecosystems across the globe. Identifying functional genes associated with thermotolerance is crucial for elucidating coral adaptation mechanisms to climate warming and enabling scientific predictions regarding coral reef ecosystem trajectories. However, the current understanding of the molecular mechanism of coral holobiont in response to heat stress is very insufficient. Therefore, this paper reviews the research progress of functional genes related to coral thermal adaptation. Initially, pattern recognition receptors (PRRs), including Toll-like receptors (TLRs), play a crucial role in detecting heat stress and activating downstream signaling cascades, thereby initiating the immune response process. These responses primarily involve: upregulation of heat shock proteins (HSPs) to facilitate the refolding of denatured polypeptides; induction of antioxidant protein genes to mitigate oxidative damage caused by reactive oxygen species (ROS); genes associated with apoptosis and pyroptosis play a crucial role in eliminating "harmful" cells. As thermal stress intensifies, corals initiate a sophisticated network of cellular processes to maintain. As heat stress intensifies, corals initiate a series of complex processes to jointly maintain cellular homeostasis. This includes: rapid activation of photoprotective protein genes to repair the photosynthetic apparatus of Symbiodiniaceae; expression of host fluorescent proteins to maintain redox balance; calcium channel proteins maintain the stability of intracellular Ca2+ levels; modulation of metabolic pathways to ensure adequate nutrient supply; inhibition of cell cycle progression to conserve energy; maintenance of cytoskeletal integrity to preserve structural stability; and regulation of ubiquitin-proteasome system for protein quality control. Furthermore, recurrent thermal stress events can induce acclimatization in corals, potentially enhancing their thermal tolerance through multiple mechanisms: downregulation of host metabolic rate, protection of heat-sensitive proteins, and upregulation of antioxidant enzymes and ammonium assimilation pathways.
Global warming and extreme thermal events have induced widespread coral bleaching, leading to the rapid degradation of coral reef ecosystems across the globe. Identifying functional genes associated with thermotolerance is crucial for elucidating coral adaptation mechanisms to climate warming and enabling scientific predictions regarding coral reef ecosystem trajectories. However, the current understanding of the molecular mechanism of coral holobiont in response to heat stress is very insufficient. Therefore, this paper reviews the research progress of functional genes related to coral thermal adaptation. Initially, pattern recognition receptors (PRRs), including Toll-like receptors (TLRs), play a crucial role in detecting heat stress and activating downstream signaling cascades, thereby initiating the immune response process. These responses primarily involve: upregulation of heat shock proteins (HSPs) to facilitate the refolding of denatured polypeptides; induction of antioxidant protein genes to mitigate oxidative damage caused by reactive oxygen species (ROS); genes associated with apoptosis and pyroptosis play a crucial role in eliminating "harmful" cells. As thermal stress intensifies, corals initiate a sophisticated network of cellular processes to maintain. As heat stress intensifies, corals initiate a series of complex processes to jointly maintain cellular homeostasis. This includes: rapid activation of photoprotective protein genes to repair the photosynthetic apparatus of Symbiodiniaceae; expression of host fluorescent proteins to maintain redox balance; calcium channel proteins maintain the stability of intracellular Ca2+ levels; modulation of metabolic pathways to ensure adequate nutrient supply; inhibition of cell cycle progression to conserve energy; maintenance of cytoskeletal integrity to preserve structural stability; and regulation of ubiquitin-proteasome system for protein quality control. Furthermore, recurrent thermal stress events can induce acclimatization in corals, potentially enhancing their thermal tolerance through multiple mechanisms: downregulation of host metabolic rate, protection of heat-sensitive proteins, and upregulation of antioxidant enzymes and ammonium assimilation pathways.
, Available online
Abstract:
This study is based on survey data of fish communities in the Zhoushan fishing ground and uses a resampling technique to simulate the random loss of rare and common species. It also employs a biomass proportion reduction method to simulate scenarios of biomass loss, in order to explore the mechanisms by which the loss of different ecological groups affects functional diversity in fish communities. The results show that although rare species account for only 3% of the total community biomass, their species richness constitutes nearly 40% of the community, indicating an important ecological niche within the community structure. The simulation of species loss scenarios revealed that the loss of rare species’ richness directly impacts the functional diversity indices, specifically leading to a decrease in functional richness and an increase in functional evenness, while functional divergence and Rao’s quadratic entropy indices showed no significant changes. In contrast, the loss of common species’ richness resulted in a decline in functional richness, while the other three functional diversity indices remained relatively stable. Under the biomass loss scenarios, the reduction in rare species’ biomass led to unchanged functional richness but declines in functional evenness, functional divergence, and Rao’s quadratic entropy indices. The functional evenness index exhibited a nonlinear decline that started slowly and then accelerated, while the other two indices showed linear decreasing patterns. In contrast, the loss of common species’ biomass caused the latter three indices to decline in a pattern that started rapidly and then slowed down. Rare species occupy unique functional niches in the community, with their functional traits distributed at the edges of the multidimensional functional space. They play a unique role in maintaining community functional diversity. Strengthening the protection of rare species and their habitats is a key strategy for maintaining regional ecosystem diversity and stability.
This study is based on survey data of fish communities in the Zhoushan fishing ground and uses a resampling technique to simulate the random loss of rare and common species. It also employs a biomass proportion reduction method to simulate scenarios of biomass loss, in order to explore the mechanisms by which the loss of different ecological groups affects functional diversity in fish communities. The results show that although rare species account for only 3% of the total community biomass, their species richness constitutes nearly 40% of the community, indicating an important ecological niche within the community structure. The simulation of species loss scenarios revealed that the loss of rare species’ richness directly impacts the functional diversity indices, specifically leading to a decrease in functional richness and an increase in functional evenness, while functional divergence and Rao’s quadratic entropy indices showed no significant changes. In contrast, the loss of common species’ richness resulted in a decline in functional richness, while the other three functional diversity indices remained relatively stable. Under the biomass loss scenarios, the reduction in rare species’ biomass led to unchanged functional richness but declines in functional evenness, functional divergence, and Rao’s quadratic entropy indices. The functional evenness index exhibited a nonlinear decline that started slowly and then accelerated, while the other two indices showed linear decreasing patterns. In contrast, the loss of common species’ biomass caused the latter three indices to decline in a pattern that started rapidly and then slowed down. Rare species occupy unique functional niches in the community, with their functional traits distributed at the edges of the multidimensional functional space. They play a unique role in maintaining community functional diversity. Strengthening the protection of rare species and their habitats is a key strategy for maintaining regional ecosystem diversity and stability.
, Available online
Abstract:
Nearshore coral reefs are frequently subjected to prolonged exposure to high levels of suspended particulate matter (SPM). However, the tolerance threshold of scleractinian corals to SPM remains inadequatedly understood, complicating the protection and management of nearshore scleractinian coral communities. In this study, we investigated the physiological responses of Dipsastraea speciosa and Cyphastrea sp., the dominant species of scleractinian corals in the Dongshan waters, which represent the northern distribution limit of scleractinian coral communities, under varying SPM concentrations (0 mg/L, 35 mg/L, 50 mg/L and 100 mg/L). A SPM-controlled simulated system was employed by injecting SPM into experimental tanks to regulate its concentration over a 28-day period. Morphological characteristics and a series of photosynthetic physiological parameters were used as indicators. The results indicated that the polyps of both coral species exposed to three groups of SPM treatments exhibited shrinkageduring the initial stages of the experiment, but quickly recovered over time. No individual of coral bleaching or mortality were observed. Additionally, both coral species demonstrated significant photosynthetic physiological plasticity, evidenced by rising ΦPSII values with SPM concentration increased, reaching a maximum at 100 mg/L. This suggests that the two coral species can mitigate light shading by enhancing their photosynthetic efficiency in response to high SPM concentrations. Furthermore, Fv/Fm ratios, chlorophyll content, and zooxanthella density for both coral species remained relatively stable under high SPM exposure, indicating that their photosynthetic performance remained healthy despite elevated SPM levels. This implies that the tolerance threshold of these two scleractinian corals to SPM may exceed 100 mg/L. This study is the first experiment in China to successfully maintain high SPM levels over an extended period, and the findings provide essential data for the protection and management of scleractinian coral communities in China.
Nearshore coral reefs are frequently subjected to prolonged exposure to high levels of suspended particulate matter (SPM). However, the tolerance threshold of scleractinian corals to SPM remains inadequatedly understood, complicating the protection and management of nearshore scleractinian coral communities. In this study, we investigated the physiological responses of Dipsastraea speciosa and Cyphastrea sp., the dominant species of scleractinian corals in the Dongshan waters, which represent the northern distribution limit of scleractinian coral communities, under varying SPM concentrations (0 mg/L, 35 mg/L, 50 mg/L and 100 mg/L). A SPM-controlled simulated system was employed by injecting SPM into experimental tanks to regulate its concentration over a 28-day period. Morphological characteristics and a series of photosynthetic physiological parameters were used as indicators. The results indicated that the polyps of both coral species exposed to three groups of SPM treatments exhibited shrinkageduring the initial stages of the experiment, but quickly recovered over time. No individual of coral bleaching or mortality were observed. Additionally, both coral species demonstrated significant photosynthetic physiological plasticity, evidenced by rising ΦPSII values with SPM concentration increased, reaching a maximum at 100 mg/L. This suggests that the two coral species can mitigate light shading by enhancing their photosynthetic efficiency in response to high SPM concentrations. Furthermore, Fv/Fm ratios, chlorophyll content, and zooxanthella density for both coral species remained relatively stable under high SPM exposure, indicating that their photosynthetic performance remained healthy despite elevated SPM levels. This implies that the tolerance threshold of these two scleractinian corals to SPM may exceed 100 mg/L. This study is the first experiment in China to successfully maintain high SPM levels over an extended period, and the findings provide essential data for the protection and management of scleractinian coral communities in China.
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Abstract:
Stable carbon (δ13C) and nitrogen (δ15N) isotope compositions are powerful tools for elucidating fish physiology, trophic interactions, and origin. However, pretreatment methods can substantially influence isotopic results, and the underlying mechanisms remain poorly understood. This study investigates the effects of lipid removal from muscle and acid leaching of scales on the δ13C and δ15N values of large yellow croaker (Larimichthys crocea), a major mariculture species in China. We found that lipid extraction significantly increased muscle δ13C, while acid leaching decreased scale δ13C. An isotope mixing model effectively explained these δ13C variations. Conversely, both pretreatments increased δ15N, suggesting potential losses of specific nitrogen isotope signals. Utilizing a dynamic equilibrium model, we established a theoretical relationship between carbon and nitrogen isotopes in muscle and scales, validating scales as a muscle proxy for nitrogen isotope analysis. This research provides critical baseline data for understanding stable isotope heterogeneity in large yellow croaker, contributes to our understanding of inter-tissue metabolic dynamics, and supports the application of non-lethal sampling in fish stable isotope studies.
Stable carbon (δ13C) and nitrogen (δ15N) isotope compositions are powerful tools for elucidating fish physiology, trophic interactions, and origin. However, pretreatment methods can substantially influence isotopic results, and the underlying mechanisms remain poorly understood. This study investigates the effects of lipid removal from muscle and acid leaching of scales on the δ13C and δ15N values of large yellow croaker (Larimichthys crocea), a major mariculture species in China. We found that lipid extraction significantly increased muscle δ13C, while acid leaching decreased scale δ13C. An isotope mixing model effectively explained these δ13C variations. Conversely, both pretreatments increased δ15N, suggesting potential losses of specific nitrogen isotope signals. Utilizing a dynamic equilibrium model, we established a theoretical relationship between carbon and nitrogen isotopes in muscle and scales, validating scales as a muscle proxy for nitrogen isotope analysis. This research provides critical baseline data for understanding stable isotope heterogeneity in large yellow croaker, contributes to our understanding of inter-tissue metabolic dynamics, and supports the application of non-lethal sampling in fish stable isotope studies.
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Abstract:
A self-developed separation and enrichment device was employed to investigate the pretreatment method for isolating and concentrating 15 trace elements (Al, Sc, V, Fe, Co, Ni, Cu, Zn, Ga, Cd, Nd, Pb, Bi, Th, and U) from seawater using Toyopearl AF-Chelate 650M chelating resin. Key parameters including sample loading pH, washing solution composition and volume, and eluent type and volume were optimized. High-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) was used for accurate determination. The results demonstrated that when 8.92 mL of seawater sample was mixed with acetic acid-ammonium acetate buffer solution at a 1:1 ratio (loading pH = 5.25) and loaded onto the resin, matrix impurities could be effectively removed by washing with 8.0 mL of Milli-Q water. After matrix removal, the adsorbed trace elements were quantitatively recovered by elution with 2.25 mL of 0.8 mol/L HNO3. Rh was added as an internal standard to the eluent prior to HR-ICP-MS analysis. Method blanks ranged from 0.27 pg (Cd) to 52.5 pg (Al), with method detection limits between 0.06 ng/L (Cd) and 1.67 ng/L (Zn). Excellent linearity (R2 > 0.999) was achieved across the concentration range of 0.01−50.0 μg/L. The method was validated using certified reference materials GBW(E)080040 and CASS-6. For GBW(E)080040, measured concentrations of Cu, Zn, Cd and Pb agreed well with certified values (relative error < 4.1%, RSD < 4.1%), with spike recoveries of 92.6%−107% for all 15 elements. Results for CASS-6 also showed good agreement with certified and reported values (RSD < 6.4%). This method features simple and rapid pretreatment, efficient matrix removal, low detection limits, high accuracy and good precision, making it suitable for simultaneous determination of trace elements in various water matrices including natural freshwater, drinking water, estuarine and marine waters.
A self-developed separation and enrichment device was employed to investigate the pretreatment method for isolating and concentrating 15 trace elements (Al, Sc, V, Fe, Co, Ni, Cu, Zn, Ga, Cd, Nd, Pb, Bi, Th, and U) from seawater using Toyopearl AF-Chelate 650M chelating resin. Key parameters including sample loading pH, washing solution composition and volume, and eluent type and volume were optimized. High-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) was used for accurate determination. The results demonstrated that when 8.92 mL of seawater sample was mixed with acetic acid-ammonium acetate buffer solution at a 1:1 ratio (loading pH = 5.25) and loaded onto the resin, matrix impurities could be effectively removed by washing with 8.0 mL of Milli-Q water. After matrix removal, the adsorbed trace elements were quantitatively recovered by elution with 2.25 mL of 0.8 mol/L HNO3. Rh was added as an internal standard to the eluent prior to HR-ICP-MS analysis. Method blanks ranged from 0.27 pg (Cd) to 52.5 pg (Al), with method detection limits between 0.06 ng/L (Cd) and 1.67 ng/L (Zn). Excellent linearity (R2 > 0.999) was achieved across the concentration range of 0.01−50.0 μg/L. The method was validated using certified reference materials GBW(E)080040 and CASS-6. For GBW(E)080040, measured concentrations of Cu, Zn, Cd and Pb agreed well with certified values (relative error < 4.1%, RSD < 4.1%), with spike recoveries of 92.6%−107% for all 15 elements. Results for CASS-6 also showed good agreement with certified and reported values (RSD < 6.4%). This method features simple and rapid pretreatment, efficient matrix removal, low detection limits, high accuracy and good precision, making it suitable for simultaneous determination of trace elements in various water matrices including natural freshwater, drinking water, estuarine and marine waters.
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Abstract:
Calcium carbonate (CaCO3), as a major component of shells, interacts with the organic matter framework to form shells and provide protection for mollusks. Ca2+ is an important component of CaCO3, and its acquisition, transport, and precipitation processes can significantly affect calcium carbonate deposition in mollusks. However, there is still a lack of clarity regarding the process of calcium carbonate deposition and mechanism of related genes in forming shells. Calmodulin (CaM) is a protein widely found in eukaryotic cells and specifically binds to Ca2+, which is mainly involved in a variety of physiological processes such as cellular signal transduction, regulation of target enzyme activities and regulation of Ca2+ homeostasis. In order to investigate the relationship between CaM gene and calcium carbonate deposition in shells, we performed molecular identification and expression characterization of CaM gene in Sinonovacula constricta (ScCaM), and investigated the Ca2+-binding activity of the recombinant protein ScCaM and its role in calcium carbonate deposition. The results showed that the ScCaM gene encoded a total of 149 amino acids and contained four consecutive EF-hand structural domains. ScCaM was expressed in all tissues, with the expression level in gill and mantle tissues being significantly higher than in foot, siphon, adductor muscle and hepatopancreas tissues (P < 0.05). Furthermore, the content of calcium carbonate in shells was positively proportional to their shell weight. Meanwhile, individuals with larger shell weights had higher expression levels of ScCaM. ScCaM recombinant protein had calcium ion binding activity, which can accelerate the rate of calcium carbonate deposition, and the promotion effect showed an obvious protein concentration dependence. The results showed that ScCaM gene/protein expression was closely related to shell calcium carbonate content: elevated ScCaM gene/protein expression could enhance Ca2+ transport efficiency, promote shell calcium carbonate deposition, and thus increase shell weight. This study preliminarily investigated the role of ScCaM gene in shell calcium carbonate deposition, and provided a theoretical basis for analyzing the molecular mechanism of shell formation in S. constricta.
Calcium carbonate (CaCO3), as a major component of shells, interacts with the organic matter framework to form shells and provide protection for mollusks. Ca2+ is an important component of CaCO3, and its acquisition, transport, and precipitation processes can significantly affect calcium carbonate deposition in mollusks. However, there is still a lack of clarity regarding the process of calcium carbonate deposition and mechanism of related genes in forming shells. Calmodulin (CaM) is a protein widely found in eukaryotic cells and specifically binds to Ca2+, which is mainly involved in a variety of physiological processes such as cellular signal transduction, regulation of target enzyme activities and regulation of Ca2+ homeostasis. In order to investigate the relationship between CaM gene and calcium carbonate deposition in shells, we performed molecular identification and expression characterization of CaM gene in Sinonovacula constricta (ScCaM), and investigated the Ca2+-binding activity of the recombinant protein ScCaM and its role in calcium carbonate deposition. The results showed that the ScCaM gene encoded a total of 149 amino acids and contained four consecutive EF-hand structural domains. ScCaM was expressed in all tissues, with the expression level in gill and mantle tissues being significantly higher than in foot, siphon, adductor muscle and hepatopancreas tissues (P < 0.05). Furthermore, the content of calcium carbonate in shells was positively proportional to their shell weight. Meanwhile, individuals with larger shell weights had higher expression levels of ScCaM. ScCaM recombinant protein had calcium ion binding activity, which can accelerate the rate of calcium carbonate deposition, and the promotion effect showed an obvious protein concentration dependence. The results showed that ScCaM gene/protein expression was closely related to shell calcium carbonate content: elevated ScCaM gene/protein expression could enhance Ca2+ transport efficiency, promote shell calcium carbonate deposition, and thus increase shell weight. This study preliminarily investigated the role of ScCaM gene in shell calcium carbonate deposition, and provided a theoretical basis for analyzing the molecular mechanism of shell formation in S. constricta.
, Available online , doi: 10.12284/hyxb2025006
Abstract:
Studying the occurrence and dynamics of microplastics on coastal beaches is crucial for the integrated management of coastal zones and the assessment of ecological risks. Previous research has highlighted that physical processes play a pivotal role in influencing the occurrences of microplastic on coastal beaches. However, the impact of extreme meteorological events such as typhoons on the distribution of microplastic pollution has yet to be explored. This study conducted field fixed-plot experiments on the coastal beaches of Xiamen City before and after Typhoon "Haikui" to analyze the variations in the abundance, composition, and diversity of microplastic on beaches. The results showed that the abundance of microplastics on the beaches in Xiamen City before Typhoon Haikui was (251.5 ± 27.9) n/kg, and this value significantly decreased to (127.0 ± 18.8) n/kg post-typhoon. Before and after the typhoon, the composition of microplastics on the beaches showed distinct variations, with the abundance of microplastics of different shapes and sizes responding differently to the typhoon. In particular, the abundance of smaller particles (<500 μm) significantly decreased, while the proportion of fibrous particles increased. Moreover, the typhoon event led to a general decrease in the Shannon-Wiener diversity index, while an increase in the Pielou’s evenness index. The impact of typhoons on the distribution of microplastics on beaches arises from the complex coupling of multiple dynamic physical processes in extreme weather, and it is also closely related to factors such as the location and substrate conditions of the coasts. To achieve simulation and prediction of the dynamics of microplastic pollution during typhoon processes, systematic and comprehensive research on the relevant mechanisms is still required in the future.
Studying the occurrence and dynamics of microplastics on coastal beaches is crucial for the integrated management of coastal zones and the assessment of ecological risks. Previous research has highlighted that physical processes play a pivotal role in influencing the occurrences of microplastic on coastal beaches. However, the impact of extreme meteorological events such as typhoons on the distribution of microplastic pollution has yet to be explored. This study conducted field fixed-plot experiments on the coastal beaches of Xiamen City before and after Typhoon "Haikui" to analyze the variations in the abundance, composition, and diversity of microplastic on beaches. The results showed that the abundance of microplastics on the beaches in Xiamen City before Typhoon Haikui was (251.5 ± 27.9) n/kg, and this value significantly decreased to (127.0 ± 18.8) n/kg post-typhoon. Before and after the typhoon, the composition of microplastics on the beaches showed distinct variations, with the abundance of microplastics of different shapes and sizes responding differently to the typhoon. In particular, the abundance of smaller particles (<500 μm) significantly decreased, while the proportion of fibrous particles increased. Moreover, the typhoon event led to a general decrease in the Shannon-Wiener diversity index, while an increase in the Pielou’s evenness index. The impact of typhoons on the distribution of microplastics on beaches arises from the complex coupling of multiple dynamic physical processes in extreme weather, and it is also closely related to factors such as the location and substrate conditions of the coasts. To achieve simulation and prediction of the dynamics of microplastic pollution during typhoon processes, systematic and comprehensive research on the relevant mechanisms is still required in the future.
, Available online
Abstract:
This study focuses on the physical process of a sea fog event during Typhoon Lekima in the Northern Yellow Sea by using observation data, reanalysis data and backward trajectory model. The analysis indicates that the typhoon circulation was the decisive factor determining whether fog formed offshore and developed inland. The warm and humid southerlies from the south Yellow Sea condensed into fog on the colder sea surface besides the typhoon center, which not only provided sufficient moisture for the formation and development of the sea fog but also formed a significant inversion layer over the fog area with the downdraft in the center of the typhoon. The "stable up and turbulent down" structure in the atmospheric boundary layer improved the development of sea fog on the coast and inland area. However, the horizontal wind steering and the strengthening wind speed behind the typhoon strengthened the wind shear in the atmospheric boundary layer, resulting in the enhanced turbulent mixing and the decrease of the stability in the bottom atmospheric boundary layer, which was the main cause of the fog dissipation.
This study focuses on the physical process of a sea fog event during Typhoon Lekima in the Northern Yellow Sea by using observation data, reanalysis data and backward trajectory model. The analysis indicates that the typhoon circulation was the decisive factor determining whether fog formed offshore and developed inland. The warm and humid southerlies from the south Yellow Sea condensed into fog on the colder sea surface besides the typhoon center, which not only provided sufficient moisture for the formation and development of the sea fog but also formed a significant inversion layer over the fog area with the downdraft in the center of the typhoon. The "stable up and turbulent down" structure in the atmospheric boundary layer improved the development of sea fog on the coast and inland area. However, the horizontal wind steering and the strengthening wind speed behind the typhoon strengthened the wind shear in the atmospheric boundary layer, resulting in the enhanced turbulent mixing and the decrease of the stability in the bottom atmospheric boundary layer, which was the main cause of the fog dissipation.
, Available online
Abstract:
The possibility of the Indonesian submarine wreck on 20 April 2021 was analyzed based on satellite remote sensing observation and numerical simulation. The results indicate that large-amplitude oceanic internal waves, estimated to be approximately 50 m using satellite images, originate from the Lombok Strait. They are widely distributed to the north of the Bali Island and are suggested to cause an abrupt sinking of the Indonesian submarine.
The possibility of the Indonesian submarine wreck on 20 April 2021 was analyzed based on satellite remote sensing observation and numerical simulation. The results indicate that large-amplitude oceanic internal waves, estimated to be approximately 50 m using satellite images, originate from the Lombok Strait. They are widely distributed to the north of the Bali Island and are suggested to cause an abrupt sinking of the Indonesian submarine.
, Available online
Abstract:
Abstract：The potential fish production was controlled largely by ocean primary production (OPP) and there were a lot of research findings of estimating fish production by using OPP in China. The relationships between the biomass of fishery stock and OPP were often complicated by the varieties of trophic control in the ecosystem. In this paper, we examined the relationship between biomass of chub mackerel (Scomber japonicus) and net primary production (NPP) and discussed mechanism of trophic control in the ecosystem of chub mackerel fishing ground in south East China Sea by using catch and effort data from the large purse sense of China fishery and NPP derived from remote sensing. The results showed there was a significant non-linear relationship between NPP and standardized CPUE (Catch Per Unit Effort) (P<0.05) instead of the linear trend. The non-linear relationship could be described by a reversed parabolic curve, which meant the biomass of chub mackerel increased with NPP and then decreased when the NPP exceeded a point. The results implied there were other trophic controls in addition to bottom-up control occurred in the ecosystem in south East China Sea. We speculated the change of abundance of the key species at intermediate trophic levels or/and interspecific competitions contribute to the relationship.
Abstract：The potential fish production was controlled largely by ocean primary production (OPP) and there were a lot of research findings of estimating fish production by using OPP in China. The relationships between the biomass of fishery stock and OPP were often complicated by the varieties of trophic control in the ecosystem. In this paper, we examined the relationship between biomass of chub mackerel (Scomber japonicus) and net primary production (NPP) and discussed mechanism of trophic control in the ecosystem of chub mackerel fishing ground in south East China Sea by using catch and effort data from the large purse sense of China fishery and NPP derived from remote sensing. The results showed there was a significant non-linear relationship between NPP and standardized CPUE (Catch Per Unit Effort) (P<0.05) instead of the linear trend. The non-linear relationship could be described by a reversed parabolic curve, which meant the biomass of chub mackerel increased with NPP and then decreased when the NPP exceeded a point. The results implied there were other trophic controls in addition to bottom-up control occurred in the ecosystem in south East China Sea. We speculated the change of abundance of the key species at intermediate trophic levels or/and interspecific competitions contribute to the relationship.
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