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- Green synthesis of iron oxide (Fe3O4) nanoparticles using two selected brown seaweeds: Characterization and application for lead bioremediation
- A nowcasting model for the prediction of typhoon tracks based on a long short term memory neural network
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- Effect of temperature, salinity and irradiance on growth and photosynthesis of Ulva prolifera
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Abstract:
As our understanding of ecology deepens and modeling techniques advance, species distribution models have grown increasingly sophisticated, enhancing both their fitting and predictive capabilities. However, the dependability of predictive accuracy remains a critical issue, as the precision of these predictions largely hinges on the quality of the base data. We developed models using both field survey and remote sensing data from 2016 to 2020 to evaluate the impact of different data sources on the accuracy of predictions for S. japonicus distributions. Our research findings indicate that the variability of water temperature and salinity data from field suvery is significantly greater than that from remote sensing data. Within the same season, we found that the relationship between the abundance of S. japonicus and environmental factors varied significantly depending on the data source. Models using field survey data were able to more accurately reflect the complex relationships between resource distribution and environmental factors. Additionally, in terms of model predictive performance, models based on field survey data demonstrated greater accuracy in predicting the abundance of S. japonicus compared to those based on remote sensing data, allowing for more accurate mastery of their spatial distribution characteristics. This study highlights the significant impact of data sources on the accuracy of species distribution models and offers valuable insights for fisheries resources management.
As our understanding of ecology deepens and modeling techniques advance, species distribution models have grown increasingly sophisticated, enhancing both their fitting and predictive capabilities. However, the dependability of predictive accuracy remains a critical issue, as the precision of these predictions largely hinges on the quality of the base data. We developed models using both field survey and remote sensing data from 2016 to 2020 to evaluate the impact of different data sources on the accuracy of predictions for S. japonicus distributions. Our research findings indicate that the variability of water temperature and salinity data from field suvery is significantly greater than that from remote sensing data. Within the same season, we found that the relationship between the abundance of S. japonicus and environmental factors varied significantly depending on the data source. Models using field survey data were able to more accurately reflect the complex relationships between resource distribution and environmental factors. Additionally, in terms of model predictive performance, models based on field survey data demonstrated greater accuracy in predicting the abundance of S. japonicus compared to those based on remote sensing data, allowing for more accurate mastery of their spatial distribution characteristics. This study highlights the significant impact of data sources on the accuracy of species distribution models and offers valuable insights for fisheries resources management.
, Available online ,
doi: https://doi.org/10.1007/s13131-024-2420-x
Abstract:
Phytoplankton blooms are complex environmental phenomena driven by multiple factors. Understanding their relationships with meteorological factors and climate oscillations is essential for advancing data-driven and hybrid statistical-dynamical models. However, these relationships have rarely been investigated across different temporal scales. This study employs wavelet transform coherence and multiple wavelet coherence to examine the multiscale and multivariate relationships between phytoplankton blooms, meteorological factors, and climate oscillations in eight large marine ecosystems of the Western North Pacific. The results reveal that all phytoplankton blooms in the studied ecosystems exhibit significant annual oscillations, while seasonal climate patterns demonstrate either unimodal or bimodal distributions. A comparison of the wavelet transform coherence and multiple wavelet coherence results indicates that meteorological factors primarily drive short-period variations in phytoplankton blooms, whereas climate oscillations exert more influence on long-term changes. The explanation of phytoplankton blooms increases as the driver factors increase, but there is also some decreasing due to the collinearity between different factors. The sea-air temperature difference emerges as the most significant driving factor, with its mechanisms varying across marine ecosystems: one type influences mixed-layer depth, while the other arises from interspecific differences in temperature sensitivity. Furthermore, the results underscore the importance of integrating non-dominant large-scale circulation indices with predominant meteorological factors for a more comprehensive understanding.
Phytoplankton blooms are complex environmental phenomena driven by multiple factors. Understanding their relationships with meteorological factors and climate oscillations is essential for advancing data-driven and hybrid statistical-dynamical models. However, these relationships have rarely been investigated across different temporal scales. This study employs wavelet transform coherence and multiple wavelet coherence to examine the multiscale and multivariate relationships between phytoplankton blooms, meteorological factors, and climate oscillations in eight large marine ecosystems of the Western North Pacific. The results reveal that all phytoplankton blooms in the studied ecosystems exhibit significant annual oscillations, while seasonal climate patterns demonstrate either unimodal or bimodal distributions. A comparison of the wavelet transform coherence and multiple wavelet coherence results indicates that meteorological factors primarily drive short-period variations in phytoplankton blooms, whereas climate oscillations exert more influence on long-term changes. The explanation of phytoplankton blooms increases as the driver factors increase, but there is also some decreasing due to the collinearity between different factors. The sea-air temperature difference emerges as the most significant driving factor, with its mechanisms varying across marine ecosystems: one type influences mixed-layer depth, while the other arises from interspecific differences in temperature sensitivity. Furthermore, the results underscore the importance of integrating non-dominant large-scale circulation indices with predominant meteorological factors for a more comprehensive understanding.
, Available online ,
doi: 10.1007/s13131-024-2301-3
Abstract:
The spatial variability of mesozooplankton (MZ) community characteristics, with an emphasis on the predominant taxa, copepods, were evaluated between two distinct coastal water environments of Mangalore: the Netravati-Gurupura estuarine system (NGES) and the adjacent nearshore waters (<20 m depth) on the southwest coast of India during winter 2018. The nearshore waters were characterised by uniformly distributed hydrographic properties, particularly in terms of water column temperature, salinity and turbidity. This well-mixed water column likely stimulated increased phytoplankton chlorophyll a concentrations (av. 2.9±2.2 mg/m3), which in turn supported higher MZ biomass (av. 0.4±0.15 mL/m3) and abundance (av.6889 ±3387 ind./m3) in the nearshore waters. In contrast, the NGES exhibited highly variable hydrographic conditions, leading to inconsistent chlorophyll a (av. 3.2±3.7 mg/m3), along with significantly lower MZ biomass (av. 0.1±0.2 mL/m3) and abundance (av. 238±339 ind./m3). The MZ community was dominated by herbivorous copepods (HCs), particularly Bestiolina similis, in the entire study region; however, the nearshore waters supported a more diverse taxon. The overall dominance of HCs, e.g., B. similis and Pseudodiaptomous aurivillii, in the nearshore waters, indicates the presence of stable hydrographic conditions, especially consistently higher salinity and chlorophyll a level. In contrast, the unstable hydrographic conditions in the NGES, primarily reflected in the uneven salinity distributions, likely contributed to the reduced MZ biomass and abundance. The relative increase in the abundance of B. similis observed exclusively in the euhaline zones of the estuary highlights the significant influence of neritic waters.
The spatial variability of mesozooplankton (MZ) community characteristics, with an emphasis on the predominant taxa, copepods, were evaluated between two distinct coastal water environments of Mangalore: the Netravati-Gurupura estuarine system (NGES) and the adjacent nearshore waters (<20 m depth) on the southwest coast of India during winter 2018. The nearshore waters were characterised by uniformly distributed hydrographic properties, particularly in terms of water column temperature, salinity and turbidity. This well-mixed water column likely stimulated increased phytoplankton chlorophyll a concentrations (av. 2.9±2.2 mg/m3), which in turn supported higher MZ biomass (av. 0.4±0.15 mL/m3) and abundance (av.
, Available online ,
doi: 10.1007/s13131-024-2383-y
Abstract:
The correct understanding of fish population structure plays a positive role in their fishery management. The dotted gizzard shad, Konosirus punctatus, is widely distributed in the coastal waters of the Northwestern Pacific. With the over-exploitation of economically important fishes, its importance is increasingly prominent. To further examine the population genetic structure of K. punctatus across the Northwestern Pacific, the amplified fragment length polymorphism (AFLP) and the inter-simple sequence repeats (ISSRs) were employed to perform genetic variation analysis. The results showed that the combination of polyacrylamide gel electrophoresis and silver staining can effectively detect genetic variation for K. punctatus populations. The average proportions of polymorphic loci were 46.26% and 87.13% for AFLP and ISSR markers, respectively, and the genetic diversity parameters showed no obvious differences among populations. Both AMOVA and pairwise Fst suggested that there was significant genetic differentiation between Chinese and Japanese populations. All samples also clustered into two clades based on the UPGMA tree by two markers, which indicated significant genetic differentiation among populations. Consistent with the previous studies, there are two highly differentiated groups at the nuclear gene level and they were suggested to be treated as two separate genetic management units. The results of the present study could provide the genetic management strategy for this important economic species.
The correct understanding of fish population structure plays a positive role in their fishery management. The dotted gizzard shad, Konosirus punctatus, is widely distributed in the coastal waters of the Northwestern Pacific. With the over-exploitation of economically important fishes, its importance is increasingly prominent. To further examine the population genetic structure of K. punctatus across the Northwestern Pacific, the amplified fragment length polymorphism (AFLP) and the inter-simple sequence repeats (ISSRs) were employed to perform genetic variation analysis. The results showed that the combination of polyacrylamide gel electrophoresis and silver staining can effectively detect genetic variation for K. punctatus populations. The average proportions of polymorphic loci were 46.26% and 87.13% for AFLP and ISSR markers, respectively, and the genetic diversity parameters showed no obvious differences among populations. Both AMOVA and pairwise Fst suggested that there was significant genetic differentiation between Chinese and Japanese populations. All samples also clustered into two clades based on the UPGMA tree by two markers, which indicated significant genetic differentiation among populations. Consistent with the previous studies, there are two highly differentiated groups at the nuclear gene level and they were suggested to be treated as two separate genetic management units. The results of the present study could provide the genetic management strategy for this important economic species.
, Available online ,
doi: 10.1007/s13131-024-2386-8
Abstract:
The proposed study focuses on the reported oil spill detection and assessments of oil impacts on marine ecosystems. Five selected oil spills, including those in East China Sea, Balikpapan Bay, Red Sea, Mauritius coast, and Colombo coast were detected using the Sentinel-1 (S-1) satellite dataset. Sentinel-2 (S-2)/ Landsat 8 (OLI), and Sentinel-5 Precursor (S-5P) satellite datasets were utilized to observe the impacts of oil spills on vegetation cover and air quality respectively. Synthetic Aperture Radar (SAR)-based oil spill detection techniques are effective in monitoring oil pollution. Impacts of oil spills on vegetation are monitored via different Vegetation Indices (VI). The East China Sea spill moved around 190 km from the source point. The area of vegetation cover impacted by the Balikpapan Bay oil spill was 118 km2. Near real-time (NRT) data of different toxic gases from S-5P were analyzed for Sri Lanka and the Red Sea using the Google Earth Engine (GEE). It is concluded that wind speed was between the range of 3 to 9 m/s that is favorable for the oil spill detection, and it is also observed that wind direction had impacts on oil spill movement as well. VI provides highly reliable results for the four events but the Red Sea oil spill findings were not satisfactory due to low vegetation cover in this area.
The proposed study focuses on the reported oil spill detection and assessments of oil impacts on marine ecosystems. Five selected oil spills, including those in East China Sea, Balikpapan Bay, Red Sea, Mauritius coast, and Colombo coast were detected using the Sentinel-1 (S-1) satellite dataset. Sentinel-2 (S-2)/ Landsat 8 (OLI), and Sentinel-5 Precursor (S-5P) satellite datasets were utilized to observe the impacts of oil spills on vegetation cover and air quality respectively. Synthetic Aperture Radar (SAR)-based oil spill detection techniques are effective in monitoring oil pollution. Impacts of oil spills on vegetation are monitored via different Vegetation Indices (VI). The East China Sea spill moved around 190 km from the source point. The area of vegetation cover impacted by the Balikpapan Bay oil spill was 118 km2. Near real-time (NRT) data of different toxic gases from S-5P were analyzed for Sri Lanka and the Red Sea using the Google Earth Engine (GEE). It is concluded that wind speed was between the range of 3 to 9 m/s that is favorable for the oil spill detection, and it is also observed that wind direction had impacts on oil spill movement as well. VI provides highly reliable results for the four events but the Red Sea oil spill findings were not satisfactory due to low vegetation cover in this area.
, Available online ,
doi: 10.1007/s13131-024-2395-7
Abstract:
Over the past two decades, numerous countries have actively participated in the International Argo Program, working toward the global "OneArgo" goal. China's Argo program has deployed over 500 autonomous profiling floats in the Indo-Pacific, with 80 BD floats, equipped with the Beidou satellite communication system, currently operational. During the operation of the BD float network, we found that in addition to the limitation of floats battery, the loss may also be caused by communication loss due to the floats escaping from the Beidou-2’s short message coverage. In this study, float trajectories are simulated using velocity fields from an eddy-resolved resolution Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) model and a Lagrangian particle tracking model programmed to represent the vertical motions of profiling floats. The simulations can help to explore both the representativeness and the predictability of profiling float displacements. By deploying a large number of synthetic floats in the Lagrangian particle tracking system, we construct probability density functions (PDFs) of the simulated-float trajectory among key oceans, for example, a joint region of East Indian-South China Sea-Northwest Pacific Ocean (5°–40°N, 70°–140°E), which is generally similar to the location of the present BD float network. These statistics can help to estimate the chance of floats drifting into shallow seas (such as the East China Sea) and out of the coverage of the Beidou satellite communication. With this knowledge changes to the future China’s Argo observing system could be made.
Over the past two decades, numerous countries have actively participated in the International Argo Program, working toward the global "OneArgo" goal. China's Argo program has deployed over 500 autonomous profiling floats in the Indo-Pacific, with 80 BD floats, equipped with the Beidou satellite communication system, currently operational. During the operation of the BD float network, we found that in addition to the limitation of floats battery, the loss may also be caused by communication loss due to the floats escaping from the Beidou-2’s short message coverage. In this study, float trajectories are simulated using velocity fields from an eddy-resolved resolution Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) model and a Lagrangian particle tracking model programmed to represent the vertical motions of profiling floats. The simulations can help to explore both the representativeness and the predictability of profiling float displacements. By deploying a large number of synthetic floats in the Lagrangian particle tracking system, we construct probability density functions (PDFs) of the simulated-float trajectory among key oceans, for example, a joint region of East Indian-South China Sea-Northwest Pacific Ocean (5°–40°N, 70°–140°E), which is generally similar to the location of the present BD float network. These statistics can help to estimate the chance of floats drifting into shallow seas (such as the East China Sea) and out of the coverage of the Beidou satellite communication. With this knowledge changes to the future China’s Argo observing system could be made.
, Available online ,
doi: 10.1007/s13131-024-2415-7
Abstract:
Aquaculture, as the fastest-growing food production sector in the world, is becoming an increasingly nonnegligible source of greenhouse gas emissions. Despite this, there has been limited research on nitrous oxide (N2O) emission from marine aquaculture in China, where more marine aquaculture occurs than anywhere else, globally. We estimated N2O emissions (E) from marine mariculture of 10 fish and 6 crustacean species in China from 2003 to 2022 using production data from China’s fishing industry statistical yearbooks (2004–2023), and data for feed conversion rates and types from the literature. From 2003, marine aquaculture production, the annual N2O emissions (EA), and the annual N2O emissions per unit of aquaculture area (EIA) trend upward. The EA of fish culture was lower than that of crustaceans, but the EIA of fish culture was generally higher. Sea bass (0.308 Tg·N·yr−1) and white shrimp (0.945 Tg·N·yr−1) had the highest average EA among fish and crustacean cultures, respectively. The highest average EA from fish and crustacean were both Guangdong Province (fish: 0.248 Tg, crustacean: 0.547 Tg), and the highest sea area were both the South China Sea (fish: 0.316 Tg, crustacean: 1.082 Tg); The highest average EIA for fish and crustacean were Tianjin (35.40 t/ha) and Guangxi Province (19.83 t/ha), respectively, and the highest sea areas were both the South China Sea (fish: 0.316 Tg, crustacean: 1.082 Tg). These analyses provide baseline data for a greenhouse gas emissions inventory for China, based on an interpretation of them, we provide recommendations for reducing N2O emissions in marine fish and crustacean culture.
Aquaculture, as the fastest-growing food production sector in the world, is becoming an increasingly nonnegligible source of greenhouse gas emissions. Despite this, there has been limited research on nitrous oxide (N2O) emission from marine aquaculture in China, where more marine aquaculture occurs than anywhere else, globally. We estimated N2O emissions (E) from marine mariculture of 10 fish and 6 crustacean species in China from 2003 to 2022 using production data from China’s fishing industry statistical yearbooks (2004–2023), and data for feed conversion rates and types from the literature. From 2003, marine aquaculture production, the annual N2O emissions (EA), and the annual N2O emissions per unit of aquaculture area (EIA) trend upward. The EA of fish culture was lower than that of crustaceans, but the EIA of fish culture was generally higher. Sea bass (0.308 Tg·N·yr−1) and white shrimp (0.945 Tg·N·yr−1) had the highest average EA among fish and crustacean cultures, respectively. The highest average EA from fish and crustacean were both Guangdong Province (fish: 0.248 Tg, crustacean: 0.547 Tg), and the highest sea area were both the South China Sea (fish: 0.316 Tg, crustacean: 1.082 Tg); The highest average EIA for fish and crustacean were Tianjin (35.40 t/ha) and Guangxi Province (19.83 t/ha), respectively, and the highest sea areas were both the South China Sea (fish: 0.316 Tg, crustacean: 1.082 Tg). These analyses provide baseline data for a greenhouse gas emissions inventory for China, based on an interpretation of them, we provide recommendations for reducing N2O emissions in marine fish and crustacean culture.
, Available online ,
doi: 10.1007/s13131-024-2423-7
Abstract:
Particle size is an important characteristic of suspended matter, and it contains crucial information about the deposition process. Suspended particle samples in the water mixing zone of the Yangtze River Estuary were collected in December 2016. Untreated original grain size and the decentralized grain size of the suspended particles were measured via a laser particle size analyzer. Morphological characteristics and the chemical composition of the suspended particles were also studied systematically using a scanning electron microscope(SEM) with an energy dispersive X-ray spectrometer(EDS). Then, the flocculation and sedimentation of suspended matter in the water mixing zone were explored by combining them with the water mixing processes in the estuary. The average particle size of suspended matter in the mixing zone of the Yangtze River Estuary ranges from 5.73 Ф to 7.98 Ф. The particle size distribution pattern is an abnormal model with a mainly unimodal pattern. In the freshwater area that was dominated by runoff, the suspended matter is mainly composed of fine particles, the settling velocity is slow, and the flocculation is weak. Floc particles were often seen in the mixing zone, with the flocs having a relatively large particle size, a low density and a loose structure appearing at the weak mixing zone; the flocs had a compacted structure in most areas of the mixing zone. The changes of suspended particle size in the estuarine mixing zone promote the settling and deposition of suspended matter, which has an important influence on the bed geomorphology and preservation of the fine suspended particles in the estuary.
Particle size is an important characteristic of suspended matter, and it contains crucial information about the deposition process. Suspended particle samples in the water mixing zone of the Yangtze River Estuary were collected in December 2016. Untreated original grain size and the decentralized grain size of the suspended particles were measured via a laser particle size analyzer. Morphological characteristics and the chemical composition of the suspended particles were also studied systematically using a scanning electron microscope(SEM) with an energy dispersive X-ray spectrometer(EDS). Then, the flocculation and sedimentation of suspended matter in the water mixing zone were explored by combining them with the water mixing processes in the estuary. The average particle size of suspended matter in the mixing zone of the Yangtze River Estuary ranges from 5.73 Ф to 7.98 Ф. The particle size distribution pattern is an abnormal model with a mainly unimodal pattern. In the freshwater area that was dominated by runoff, the suspended matter is mainly composed of fine particles, the settling velocity is slow, and the flocculation is weak. Floc particles were often seen in the mixing zone, with the flocs having a relatively large particle size, a low density and a loose structure appearing at the weak mixing zone; the flocs had a compacted structure in most areas of the mixing zone. The changes of suspended particle size in the estuarine mixing zone promote the settling and deposition of suspended matter, which has an important influence on the bed geomorphology and preservation of the fine suspended particles in the estuary.
, Available online ,
doi: 10.1007/s13131-024-2307-x
Abstract:
The lanternfishes are mesopelagic fish that are highly productive as common bycatch of deep-sea shrimp trawlers, but they are often neglected or discarded. Despite being one of the dominant lanternfish species in the Arabian Sea, little is known about the life history of Diaphus thiollierei and its role in marine ecosystems. In this study, 103 D. thiollierei were collected in the Arabian Sea during October-November 2020 to study population growth based on sagittal otolith daily ages; and 10 fish collected during April–May 2021 were subjected to otolith microchemistry analysis to reconstruct the vertical migration in their life history using LA-ICP-MS technique. The standard length–dry weight (SL-DW) relationships for D. thiollierei revealed both negative allometric growth and a significant difference between the sexes. Using daily growth annuli counts on the sagittal section of otoliths, the von Bertalanffy growth equation for D. thiollierei was determined. The pattern of four elemental ratios (Sr to Ca, Mg to Ca, Li to Ca, and Ba to Ca) in sagittal otolith suggested that, in general, D. thiollierei descended continually after hatching until the post-larval (PL) stage when they reached a depth of approximately 200 m. Subsequently, from the PL stage to the post-metamorphosis II (PM II) stage, D. thiollierei likely further sank from 200 m to a depth of approximately 300 m, and then in the daytime they were at a depth of approximately 300–800 m to take refuge from predators. This pilot study explored to unravel the vertical migration during life history in D. thiollierei from sagittal otoliths, whereas further investigation on otolith is needed to better delineate the population ecology in detail, and thus to provide basic information for the exploitation of the lanternfish resource and the understanding of their ecological roles.
The lanternfishes are mesopelagic fish that are highly productive as common bycatch of deep-sea shrimp trawlers, but they are often neglected or discarded. Despite being one of the dominant lanternfish species in the Arabian Sea, little is known about the life history of Diaphus thiollierei and its role in marine ecosystems. In this study, 103 D. thiollierei were collected in the Arabian Sea during October-November 2020 to study population growth based on sagittal otolith daily ages; and 10 fish collected during April–May 2021 were subjected to otolith microchemistry analysis to reconstruct the vertical migration in their life history using LA-ICP-MS technique. The standard length–dry weight (SL-DW) relationships for D. thiollierei revealed both negative allometric growth and a significant difference between the sexes. Using daily growth annuli counts on the sagittal section of otoliths, the von Bertalanffy growth equation for D. thiollierei was determined. The pattern of four elemental ratios (Sr to Ca, Mg to Ca, Li to Ca, and Ba to Ca) in sagittal otolith suggested that, in general, D. thiollierei descended continually after hatching until the post-larval (PL) stage when they reached a depth of approximately 200 m. Subsequently, from the PL stage to the post-metamorphosis II (PM II) stage, D. thiollierei likely further sank from 200 m to a depth of approximately 300 m, and then in the daytime they were at a depth of approximately 300–800 m to take refuge from predators. This pilot study explored to unravel the vertical migration during life history in D. thiollierei from sagittal otoliths, whereas further investigation on otolith is needed to better delineate the population ecology in detail, and thus to provide basic information for the exploitation of the lanternfish resource and the understanding of their ecological roles.
, Available online ,
doi: 10.1007/s13131-024-2365-0
Abstract:
We introduce a new method, the piecewise Reynolds mean (PREM), for decomposing the flow velocity into the mean-flow and eddy-flow parts in the time domain for subsequent calculation of the mean and eddy kinetic energies (MKE and EKE). Compared with conventional methods like the Reynolds mean (REM) and running mean (RUM), PREM has the advantage of exact balance between the MKE and EKE, without the additional residual kinetic energy (RKE), while retaining time-dependent mean-flow. It is mathematically simple and computationally lightweight, depending on a pre-defined separation scale for the mean-flow and eddies. Based on satellite observations and the separation scale of 1 year, we compare PREM with RUM, as well as another newly proposed method, the eddy detection and extraction (EDEX). The latter is based on objective identification of mesoscale eddies and eddy anomaly extraction algorithms, and is therefore only suitable for mesoscale eddy energetics, but independent of separation scales. It is shown that compared with RUM, PREM gives larger mean EKE and stronger interannual variability. In strong-current and eddy-rich regions, the two methods differ the most (max: Kuroshio Extension, RMSD = 60.3 J/m3); but in areas with weak current and eddy, the difference accounts for the largest fraction of total EKE (max: south of the Aleutian Islands, 208%). EKE estimated by the two methods is out of phase (min correlation = 0.38). The mean EKE and standard deviation from the EDEX method resemble the PREM with 1-year separation scale, but is generally smaller in magnitude.
We introduce a new method, the piecewise Reynolds mean (PREM), for decomposing the flow velocity into the mean-flow and eddy-flow parts in the time domain for subsequent calculation of the mean and eddy kinetic energies (MKE and EKE). Compared with conventional methods like the Reynolds mean (REM) and running mean (RUM), PREM has the advantage of exact balance between the MKE and EKE, without the additional residual kinetic energy (RKE), while retaining time-dependent mean-flow. It is mathematically simple and computationally lightweight, depending on a pre-defined separation scale for the mean-flow and eddies. Based on satellite observations and the separation scale of 1 year, we compare PREM with RUM, as well as another newly proposed method, the eddy detection and extraction (EDEX). The latter is based on objective identification of mesoscale eddies and eddy anomaly extraction algorithms, and is therefore only suitable for mesoscale eddy energetics, but independent of separation scales. It is shown that compared with RUM, PREM gives larger mean EKE and stronger interannual variability. In strong-current and eddy-rich regions, the two methods differ the most (max: Kuroshio Extension, RMSD = 60.3 J/m3); but in areas with weak current and eddy, the difference accounts for the largest fraction of total EKE (max: south of the Aleutian Islands, 208%). EKE estimated by the two methods is out of phase (min correlation = 0.38). The mean EKE and standard deviation from the EDEX method resemble the PREM with 1-year separation scale, but is generally smaller in magnitude.
, Available online
Abstract:
The exchange of inorganic nutrients at the coastal sediment-water interface (SWI) plays a crucial role in regulating the nutrient budget in overlying water. The related studies mainly focus on the mid to high-latitude regions, leaving a significant gap in the quantitative assessment of nutrient exchange and environmental controls at the SWI in low-latitude coastal regions. We quantitatively assess the exchange of inorganic nutrients at the SWI in three tropical bays (Dongzhai harbor, Xiaohai lagoon, Qinglan harbor). Sediments act as a source of ammonium, phosphate, and silicate, but for nitrate, sediments can be both a source and sink, although with substantial spatial and temporal variations in their fluxes. Labile organic matter is a critical regulator for the fluxes of inorganic nutrients at the SWI. The sedimentary nutrients input with high N/P ratio will alter the nutrient stoichiometry to mitigate the nitrogen limitation in coastal waters. However, the internal sediment release in these tropical bays plays a relative weak role in contributing to the nutrient addition in comparison with the other external nutrient sources including riverine input, submarine groundwater discharge, and atmospheric deposition. According to the global compilation on SWI nutrient fluxes, we propose that water column primary production and external inputs to interpret the variation in exchange and fluxes of nutrients at the SWI in different ecosystems. Such a conceptual understanding of these chain biogeochemical processes involving external nutrient input, primary production, particulate organic matter settling, and the accumulation and release of inorganic nutrients in sediments will be helpful for the scientific-based pollution prevent and control in coastal waters.
The exchange of inorganic nutrients at the coastal sediment-water interface (SWI) plays a crucial role in regulating the nutrient budget in overlying water. The related studies mainly focus on the mid to high-latitude regions, leaving a significant gap in the quantitative assessment of nutrient exchange and environmental controls at the SWI in low-latitude coastal regions. We quantitatively assess the exchange of inorganic nutrients at the SWI in three tropical bays (Dongzhai harbor, Xiaohai lagoon, Qinglan harbor). Sediments act as a source of ammonium, phosphate, and silicate, but for nitrate, sediments can be both a source and sink, although with substantial spatial and temporal variations in their fluxes. Labile organic matter is a critical regulator for the fluxes of inorganic nutrients at the SWI. The sedimentary nutrients input with high N/P ratio will alter the nutrient stoichiometry to mitigate the nitrogen limitation in coastal waters. However, the internal sediment release in these tropical bays plays a relative weak role in contributing to the nutrient addition in comparison with the other external nutrient sources including riverine input, submarine groundwater discharge, and atmospheric deposition. According to the global compilation on SWI nutrient fluxes, we propose that water column primary production and external inputs to interpret the variation in exchange and fluxes of nutrients at the SWI in different ecosystems. Such a conceptual understanding of these chain biogeochemical processes involving external nutrient input, primary production, particulate organic matter settling, and the accumulation and release of inorganic nutrients in sediments will be helpful for the scientific-based pollution prevent and control in coastal waters.
, Available online ,
doi: 10.1007/s13131-024-2303-1
Abstract:
Macrobenthic organisms are commonly employed as biomonitors for environmental risk assessment. In this study, we aimed to investigate the spatial and temporal patterns of the macrobenthic community, which is influenced by environmental factors of sediments and bottom water layer. We sampled a total of 12, 11, 10, and 11 stations in the Shengsi Archipelago during June 2010, August 2010, November 2020, and April 2021 respectively. A total of 124 species of macrobenthos were identified, with polychaetes being the dominant group. The abundance, biomass, and diversity indices exhibited no significant temporal differences. Similarly, biodiversity did not exhibit a clear spatial gradient, likely due to the small study area and the absence of significant differences in key factors such as depth. However, the stations with the lowest biodiversity values consistently appeared in the southwest region, possibly due to the impact of human activities. Significant differences in the macrobenthic community were observed between all months except between June and August, and mollusk Endopleura lubrica and polychaete Sigambra hanaokai were important contributors to these differences according to the results of the Similarity Percentages analysis. Suspended particulate matter (SPM) was identified as the primary driving factors of macrobenthic variability. In summary, the community structure underwent temporal changes influenced by complex current patterns, while biodiversity remained relatively stable. This study contributes to our understanding of the key environmental factors affecting macrobenthic communities and biodiversity. It also provides valuable data support for the long-term monitoring of macrobenthos and the environment in the Shengsi Archipelago.
Macrobenthic organisms are commonly employed as biomonitors for environmental risk assessment. In this study, we aimed to investigate the spatial and temporal patterns of the macrobenthic community, which is influenced by environmental factors of sediments and bottom water layer. We sampled a total of 12, 11, 10, and 11 stations in the Shengsi Archipelago during June 2010, August 2010, November 2020, and April 2021 respectively. A total of 124 species of macrobenthos were identified, with polychaetes being the dominant group. The abundance, biomass, and diversity indices exhibited no significant temporal differences. Similarly, biodiversity did not exhibit a clear spatial gradient, likely due to the small study area and the absence of significant differences in key factors such as depth. However, the stations with the lowest biodiversity values consistently appeared in the southwest region, possibly due to the impact of human activities. Significant differences in the macrobenthic community were observed between all months except between June and August, and mollusk Endopleura lubrica and polychaete Sigambra hanaokai were important contributors to these differences according to the results of the Similarity Percentages analysis. Suspended particulate matter (SPM) was identified as the primary driving factors of macrobenthic variability. In summary, the community structure underwent temporal changes influenced by complex current patterns, while biodiversity remained relatively stable. This study contributes to our understanding of the key environmental factors affecting macrobenthic communities and biodiversity. It also provides valuable data support for the long-term monitoring of macrobenthos and the environment in the Shengsi Archipelago.
, Available online ,
doi: 10.1007/s13131-022-2131-0
Abstract:
, Available online
Abstract:
Seasonal location and intensity changes in the western Pacific subtropical high (WPSH) are important factors dominating the synoptic weather and the distribution and magnitude of precipitation in the rain belt over East Asia. Therefore, this article delves into the forecast of the western Pacific subtropical high index during typhoon activity by adopting a hybrid deep learning model. Firstly, the predictors, which are the inputs of the model, are analysed based on three characteristics: the first is the statistical discipline of the WPSH index anomalies corresponding to the three types of typhoon paths; the second is the correspondence of distributions between sea surface temperature (SST), 850 hPa zonal wind (u), meridional wind (v), and 500 hPa potential height field; and the third is the numerical sensitivity experiment, which reflects the evident impact of variations in the physical field around the typhoon to the WPSH index. Secondly, the model is repeatedly trained through the backward propagation algorithm to predict the WPSH index using 2011-2018 atmospheric variables as the input of the training set. The model predicts the WPSH index after 6 h, 24 h, 48 h, and 72 h. The validation set using independent data in 2019 is utilized to illustrate the performance. Finally, the model is improved by changing the CNN2D module to the DeCNN module to enhance its ability to predict images. Taking the 2019 Typhoon Lekima as an example, it shows the promising performance of this model to predict the 500 hPa potential height field.
Seasonal location and intensity changes in the western Pacific subtropical high (WPSH) are important factors dominating the synoptic weather and the distribution and magnitude of precipitation in the rain belt over East Asia. Therefore, this article delves into the forecast of the western Pacific subtropical high index during typhoon activity by adopting a hybrid deep learning model. Firstly, the predictors, which are the inputs of the model, are analysed based on three characteristics: the first is the statistical discipline of the WPSH index anomalies corresponding to the three types of typhoon paths; the second is the correspondence of distributions between sea surface temperature (SST), 850 hPa zonal wind (u), meridional wind (v), and 500 hPa potential height field; and the third is the numerical sensitivity experiment, which reflects the evident impact of variations in the physical field around the typhoon to the WPSH index. Secondly, the model is repeatedly trained through the backward propagation algorithm to predict the WPSH index using 2011-2018 atmospheric variables as the input of the training set. The model predicts the WPSH index after 6 h, 24 h, 48 h, and 72 h. The validation set using independent data in 2019 is utilized to illustrate the performance. Finally, the model is improved by changing the CNN2D module to the DeCNN module to enhance its ability to predict images. Taking the 2019 Typhoon Lekima as an example, it shows the promising performance of this model to predict the 500 hPa potential height field.
, Available online ,
doi: 10.1007/s13131-020-1589-x
Abstract:
Protease-producing bacteria play key roles in the degradation of organic nitrogen materials in marine sediments. However, their diversity, production of proteases and other extracellular enzymes, even in situ ecological functions remain largely unknown. In this study, we investigated the diversity of cultivable extracellular protease-producing bacteria in the sediments of the Bohai Bay. A total of 109 bacterial isolates were obtained from the sediments of 7 stations. The abundance of cultivable protease-producing bacteria was about 104 CFU/g of sediment in all the samples. Phylogenetic analysis based on 16S rRNA gene sequences classified all the isolates into 14 genera from phyla Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria, with Pseudoalteromonas (63/109, 57.8%), Bacillus (9/109, 8.2%), Sulfitobacter (8/109, 7.3%) and Salegentibacter (6/109, 5.5%) as the dominant taxa. Enzymatic inhibition tests indicated that all the tested isolates produced serine and/or metalloprotease, with only a small proportion producing cysteine and/or aspartic proteases. Several extracellular enzyme activities, including alginase, lipase, amylase and cellulose, and nitrate reduction were also detected for strains with higher protease activities. According the results, the protease-producing bacteria could also be participate in many biogeochemical processes in marine sediments. Our study broadened understanding and knowledge on the potential ecological functions of protease-producing bacteria in marine sediments.
Protease-producing bacteria play key roles in the degradation of organic nitrogen materials in marine sediments. However, their diversity, production of proteases and other extracellular enzymes, even in situ ecological functions remain largely unknown. In this study, we investigated the diversity of cultivable extracellular protease-producing bacteria in the sediments of the Bohai Bay. A total of 109 bacterial isolates were obtained from the sediments of 7 stations. The abundance of cultivable protease-producing bacteria was about 104 CFU/g of sediment in all the samples. Phylogenetic analysis based on 16S rRNA gene sequences classified all the isolates into 14 genera from phyla Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria, with Pseudoalteromonas (63/109, 57.8%), Bacillus (9/109, 8.2%), Sulfitobacter (8/109, 7.3%) and Salegentibacter (6/109, 5.5%) as the dominant taxa. Enzymatic inhibition tests indicated that all the tested isolates produced serine and/or metalloprotease, with only a small proportion producing cysteine and/or aspartic proteases. Several extracellular enzyme activities, including alginase, lipase, amylase and cellulose, and nitrate reduction were also detected for strains with higher protease activities. According the results, the protease-producing bacteria could also be participate in many biogeochemical processes in marine sediments. Our study broadened understanding and knowledge on the potential ecological functions of protease-producing bacteria in marine sediments.
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2024, 43(11): 1-11.
doi: 10.1007/s13131-024-2432-6
Abstract:
Based on in-situ observations in the East China Sea (ECS) during October 2021, we investigated a cross-shelf penetrating front (PF) in the inner shelf and explored its potential biogeochemical-ecological effects from a multidisciplinary perspective. The results show that a pronounced tongue-shaped PF was present at the southeast of the Hangzhou Bay, with salinity of 29−32 and a seaward horizontal penetration scale of ~200 km. It mainly occurred in the upper layers, and a spatial separation existed between this PF and the bottom salinity front in the northern coastal region off Zhejiang. In contrast, the salinity fronts at surface and bottom were well matched in the southern coastal area. Compared to the surface-to-bottom consistent coastal front in the southern region off Zhejiang, a stronger thermocline and halocline were sustained in the northern PF-dominated region, and suitable conditions could be achieved for phytoplankton growth and accumulation. The in-situ observed high-chlorophyll a (Chl a) zone in a seaward tongue shape was further an important indicator or signal for PF occurrence, and it was responsible for the decoupling of nutrient distributions and PF. The southern coastal front off Zhejiang might largely restrict the seaward transport of nutrients, and the dynamic environment under weak stratification in this region was disadvantageous for the growth of phytoplankton; thus the Chl a content was maintained at a relatively low level near the southern coastal region. Our results demonstrate that the PF combined with the coastal front may play an important role in shaping/regulating hydrodynamics, nutrient distributions and the Chl a regime over the inner ECS shelf.
Based on in-situ observations in the East China Sea (ECS) during October 2021, we investigated a cross-shelf penetrating front (PF) in the inner shelf and explored its potential biogeochemical-ecological effects from a multidisciplinary perspective. The results show that a pronounced tongue-shaped PF was present at the southeast of the Hangzhou Bay, with salinity of 29−32 and a seaward horizontal penetration scale of ~200 km. It mainly occurred in the upper layers, and a spatial separation existed between this PF and the bottom salinity front in the northern coastal region off Zhejiang. In contrast, the salinity fronts at surface and bottom were well matched in the southern coastal area. Compared to the surface-to-bottom consistent coastal front in the southern region off Zhejiang, a stronger thermocline and halocline were sustained in the northern PF-dominated region, and suitable conditions could be achieved for phytoplankton growth and accumulation. The in-situ observed high-chlorophyll a (Chl a) zone in a seaward tongue shape was further an important indicator or signal for PF occurrence, and it was responsible for the decoupling of nutrient distributions and PF. The southern coastal front off Zhejiang might largely restrict the seaward transport of nutrients, and the dynamic environment under weak stratification in this region was disadvantageous for the growth of phytoplankton; thus the Chl a content was maintained at a relatively low level near the southern coastal region. Our results demonstrate that the PF combined with the coastal front may play an important role in shaping/regulating hydrodynamics, nutrient distributions and the Chl a regime over the inner ECS shelf.
2024, 43(11): 12-25.
doi: 10.1007/s13131-024-2433-5
Abstract:
Estuaries are often a significant source of atmospheric CO2. However, studies of carbonate systems have predominantly focused on large estuaries, while smaller estuaries have scarcely been documented. In this study, we collected surface and bottom seawater carbonate samples in the subtropical Jiulong River Estuary across different tidal levels from 2019 to 2021. The results showed that estuarine mixing of freshwater from the river with seawater was the dominant factor influencing the estuarine carbonate system. Moreover, estuarine mixing is concomitantly impacted by the net metabolism of biological production and decomposition, groundwater input, release of CO2 from the estuary, and precipitation or dissolution of calcium carbonate. The estuarine partial pressure of CO2 (pCO2) varied from 530 μatm to7715 μatm, which represents a strong source of atmospheric CO2. The mean annual air-sea CO2 flux estimated from three different parameterized equations was approximately (25.63 ± 10.25) mol/(m2·a). Furthermore, the annual emission to the atmosphere was approximately (0.031 ± 0.012) Tg C, which accounts for a mere 0.0077 %−0.015% of global estuarine emissions. Dissolved inorganic carbon (DIC), total alkalinity (TA) and the pCO2 exhibited high variability throughout the tidal cycle across all cruises. Specifically, the disparities observed between DIC and TA during low and high tides at identical stations during all cruises ranged from approximately 15% to 30%. The variance in the pCO2 was even more pronounced, ranging from approximately 30% to 40%. Thus, tidal discrepancies may need to be taken into consideration to estimate the CO2 flux from estuarine systems more accurately.
Estuaries are often a significant source of atmospheric CO2. However, studies of carbonate systems have predominantly focused on large estuaries, while smaller estuaries have scarcely been documented. In this study, we collected surface and bottom seawater carbonate samples in the subtropical Jiulong River Estuary across different tidal levels from 2019 to 2021. The results showed that estuarine mixing of freshwater from the river with seawater was the dominant factor influencing the estuarine carbonate system. Moreover, estuarine mixing is concomitantly impacted by the net metabolism of biological production and decomposition, groundwater input, release of CO2 from the estuary, and precipitation or dissolution of calcium carbonate. The estuarine partial pressure of CO2 (pCO2) varied from 530 μatm to
2024, 43(11): 26-33.
doi: 10.1007/s13131-024-2430-8
Abstract:
Trace metals emitted from human activities may have penetrated into the deep seas, and the underlying control mechanisms remain poorly understood. Sinking particles collected by moored time-series sediment traps from the northern South China Sea (NSCS) basin showed significant enrichment of anthropogenic aerosol Pb relative to lithogenic Fe. Total mass flux was primarily driven by seasonal primary production, and significant positive correlations were found between Pb/Fe flux and major biogenic components, indicating the crucial role of the biological pump in Pb/Fe scavenging in the water column. Notably, Pb exhibited 30−50 times higher affinity to biogenic components than Fe. A comparison was made between the enrichment factors of Fe and Pb in aerosols, euphotic particles, and sinking particles, which revealed that Pb exhibited significantly higher particle reactivity than Fe. This higher particle reactivity may encompass processes such as adsorption/desorption, bioaccumulation and decomposition release. The differential scavenging behavior of Pb suggested that the majority of Pb was rapidly scavenged in the euphotic zone and was preferentially released for accumulation in the twilight zone. This accumulation may further outflow through the Luzon Strait and result in the high dissolved Pb concentration observed in the subsurface water columns in both the NSCS and western Pacific Ocean. The rest of anthropogenic Pb in sinking particles tended to penetrate into deeper water layers and continue to be released below the twilight zone. These findings provide new insights into the biogeochemical cycling of trace metals originating from anthropogenic aerosols in marginal seas and serve as an example of the fate of other anthropogenic atmospheric pollutants.
Trace metals emitted from human activities may have penetrated into the deep seas, and the underlying control mechanisms remain poorly understood. Sinking particles collected by moored time-series sediment traps from the northern South China Sea (NSCS) basin showed significant enrichment of anthropogenic aerosol Pb relative to lithogenic Fe. Total mass flux was primarily driven by seasonal primary production, and significant positive correlations were found between Pb/Fe flux and major biogenic components, indicating the crucial role of the biological pump in Pb/Fe scavenging in the water column. Notably, Pb exhibited 30−50 times higher affinity to biogenic components than Fe. A comparison was made between the enrichment factors of Fe and Pb in aerosols, euphotic particles, and sinking particles, which revealed that Pb exhibited significantly higher particle reactivity than Fe. This higher particle reactivity may encompass processes such as adsorption/desorption, bioaccumulation and decomposition release. The differential scavenging behavior of Pb suggested that the majority of Pb was rapidly scavenged in the euphotic zone and was preferentially released for accumulation in the twilight zone. This accumulation may further outflow through the Luzon Strait and result in the high dissolved Pb concentration observed in the subsurface water columns in both the NSCS and western Pacific Ocean. The rest of anthropogenic Pb in sinking particles tended to penetrate into deeper water layers and continue to be released below the twilight zone. These findings provide new insights into the biogeochemical cycling of trace metals originating from anthropogenic aerosols in marginal seas and serve as an example of the fate of other anthropogenic atmospheric pollutants.
2024, 43(11): 34-44.
doi: 10.1007/s13131-024-2397-5
Abstract:
Ridges are common features found on continental shelves and understanding their formation processes is crucial for sedimentology, stratigraphy, and geological engineering. This study investigates the development of ridges on the broad shelf of the East China Sea using a core (DH03) and associated seismic profile. Lithology analysis of the core revealed a 50 m thick shallow sandy sequence which consisted mainly of silty fine sands with intercalations of mud beds composed of sand-mud couplets. Benthic foraminifera examination indicated the offshore species were dominant. The seismic profile indicated that the ridges were separated from the older delta layers due to a boundary formed by river erosion during the last glacial maximum. Radiocarbon dating of the sandy sequence revealed an irregular chronological sequence, with most age ranges falling within the past 3 ka. Based on the chronological data from DH03 and other cores, we propose that the ridges, which were formed during the early Holocene transgression, have been active on a shelf scale in the recent 3–2 ka. Synthetic analysis of the shelf-scale ridge formation processes indicates that the sea-level fluctuations during the mid-late Holocene sea-level highstand triggered the ridge activities. A center for ridge activity developed in the southern shelf, facilitated by thicker ridge deposits in the paleo-Changjiang River Estuary and stronger currents (tidal currents and possibly internal waves) induced by the remaining funnel-shaped estuary topography. Based on these findings, we propose a conceptual model for ridge development, which includes a ridge formation stage during the early Holocene transgression and a ridge activation stage during the mid-late Holocene sea-level highstand.
Ridges are common features found on continental shelves and understanding their formation processes is crucial for sedimentology, stratigraphy, and geological engineering. This study investigates the development of ridges on the broad shelf of the East China Sea using a core (DH03) and associated seismic profile. Lithology analysis of the core revealed a 50 m thick shallow sandy sequence which consisted mainly of silty fine sands with intercalations of mud beds composed of sand-mud couplets. Benthic foraminifera examination indicated the offshore species were dominant. The seismic profile indicated that the ridges were separated from the older delta layers due to a boundary formed by river erosion during the last glacial maximum. Radiocarbon dating of the sandy sequence revealed an irregular chronological sequence, with most age ranges falling within the past 3 ka. Based on the chronological data from DH03 and other cores, we propose that the ridges, which were formed during the early Holocene transgression, have been active on a shelf scale in the recent 3–2 ka. Synthetic analysis of the shelf-scale ridge formation processes indicates that the sea-level fluctuations during the mid-late Holocene sea-level highstand triggered the ridge activities. A center for ridge activity developed in the southern shelf, facilitated by thicker ridge deposits in the paleo-Changjiang River Estuary and stronger currents (tidal currents and possibly internal waves) induced by the remaining funnel-shaped estuary topography. Based on these findings, we propose a conceptual model for ridge development, which includes a ridge formation stage during the early Holocene transgression and a ridge activation stage during the mid-late Holocene sea-level highstand.
2024, 43(11): 45-56.
doi: 10.1007/s13131-024-2313-z
Abstract:
The deltas serve as the primary interactive zone where terrestrial and marine environments converge, playing a pivotal role in the coastal deposition. In the Holocene, climate changes and sea level fluctuation are the principal driving factors in the evolution of deltas. However, human activities such as the construction of dams and reservoirs in the Anthropocene have significantly altered sediment transport in rivers, leading to depositional pattern variation during deltaic evolution. In this study, we have conducted a comparative analysis of the morphological variations (1986–2021) in the barrier system of the Hanjiang River Delta (HRD) using satellite remote sensing (SRS) method. Additionally, we have examined the lithological changes and facies alterations observed in eight boreholes on the present barrier spit. Our findings indicate that the intensification of anthropogenic activities led to a significant reduction in the sediment flux of the Hanjiang River (HR), resulting in depocenter landward migration at the estuary. SRS analysis reveals their periodical morphological characteristics and spatial variations of estuarine sandbars (1986–1992), barrier islands-lagoons (1993–2009), and barrier spits (2010–2021) during 1986 to 2021. The stratigraphy of boreholes demonstrates a south-to-north facies transition from lagoon to lagoon-barrier spit and barrier spit in vertical lithology. Therefore, the depositional evolution of the HRD barrier system is categorized into three phases: estuarine sandbar-barrier island phase (1986–1998); barrier island-lagoon phase (1999–2009); and barrier spit phase (2010–2021). During the estuarine sandbar-barrier island phase, fluvial processes played a predominate role in the deposition. Consequently, with a significant decrease in river sediment load, the dominant factors driving depositional processes shifted towards wave action and alongshore current. Based on the conceptual model in the Holocene, we propose a modified depositional model of wave-dominated deltas during Anthropocene that encompasses three evolutionary phases: estuarine sandbars and delta front platforms, barrier island-lagoon formation and landward migration of barrier spits. This pattern highlights that human-induced reduction in river sediment flux has led to a seaward deltaic progradation driven by barrier landward migration.
The deltas serve as the primary interactive zone where terrestrial and marine environments converge, playing a pivotal role in the coastal deposition. In the Holocene, climate changes and sea level fluctuation are the principal driving factors in the evolution of deltas. However, human activities such as the construction of dams and reservoirs in the Anthropocene have significantly altered sediment transport in rivers, leading to depositional pattern variation during deltaic evolution. In this study, we have conducted a comparative analysis of the morphological variations (1986–2021) in the barrier system of the Hanjiang River Delta (HRD) using satellite remote sensing (SRS) method. Additionally, we have examined the lithological changes and facies alterations observed in eight boreholes on the present barrier spit. Our findings indicate that the intensification of anthropogenic activities led to a significant reduction in the sediment flux of the Hanjiang River (HR), resulting in depocenter landward migration at the estuary. SRS analysis reveals their periodical morphological characteristics and spatial variations of estuarine sandbars (1986–1992), barrier islands-lagoons (1993–2009), and barrier spits (2010–2021) during 1986 to 2021. The stratigraphy of boreholes demonstrates a south-to-north facies transition from lagoon to lagoon-barrier spit and barrier spit in vertical lithology. Therefore, the depositional evolution of the HRD barrier system is categorized into three phases: estuarine sandbar-barrier island phase (1986–1998); barrier island-lagoon phase (1999–2009); and barrier spit phase (2010–2021). During the estuarine sandbar-barrier island phase, fluvial processes played a predominate role in the deposition. Consequently, with a significant decrease in river sediment load, the dominant factors driving depositional processes shifted towards wave action and alongshore current. Based on the conceptual model in the Holocene, we propose a modified depositional model of wave-dominated deltas during Anthropocene that encompasses three evolutionary phases: estuarine sandbars and delta front platforms, barrier island-lagoon formation and landward migration of barrier spits. This pattern highlights that human-induced reduction in river sediment flux has led to a seaward deltaic progradation driven by barrier landward migration.
2024, 43(11): 57-67.
doi: 10.1007/s13131-024-2434-4
Abstract:
The establishment of effective proxies for the differentiation of sedimentary facies in the tide-dominated river mouth is fundamental to the delineation of stratigraphy and the study of paleoenvironments. Geochemical signatures of the acetic acid (HAc) extractive phases of alkaline earth metals, such as Sr, Ba, and Ca, are closely related to sedimentary environments and thus provide a novel method for discriminating the sedimentary facies of river mouth. In this study, 50 surface water and surface sediment samples were obtained from different geomorphological units of the Jiulong River mouth, i.e., river channel, distributary channel, delta front, delta front slope, prodelta, and shallow marine area, and the salinity of the water, the grain size, and the Sr, Ba, and Ca contents and Sr/Ba molar ratio (Sr/Ba) in HAc leachates of the sediments were determined. Contents of alkaline earth metals in HAc leachates of surface sediments from the Changjiang (Yangtze) River coast were also collated. The goals of this study were to reveal the spatial distribution of alkaline earth metals in the Jiulong River mouth, define their depositional mechanisms, and search for effective geochemical proxies for identification of the various sedimentary facies in the fluvial to marine transition zone. The results revealed several land-to-sea gradients. The Ba content decreased rapidly from the distributary channel to the sea, and the Sr and Ca contents and Sr/Ba increased gradually with the increase in salinity. Salinity, marine biomass, and sedimentary dynamic processes, were speculated to be the main reasons for the differences in their spatial distributions. There were significant differences in Ba, Sr, Ca, and Sr/Ba between the river channel and the distributary channel, in Ca and Ba between the distributary channel and the delta front (slope), and in Sr, Ca, and Sr/Ba between the delta front (slope) and the prodelta–shallow marine region. The Sr–Ba scatterplot showed that the sediments of the river channel and alluvial plain were located as a high Ba and low Sr element-defined end-member, whereas samples of the prodelta and shallow marine formed a high Sr and low Ba end-member. These can be used as characteristic end-members indicating terrestrial facies and marine facies, respectively. The sediments of the delta plain, tidal river, distributary channel, delta front, and delta front slope are located between these two end-member regions of the scatterplot, and this region of the diagram can be used to identify land–sea transitional sedimentary facies.
The establishment of effective proxies for the differentiation of sedimentary facies in the tide-dominated river mouth is fundamental to the delineation of stratigraphy and the study of paleoenvironments. Geochemical signatures of the acetic acid (HAc) extractive phases of alkaline earth metals, such as Sr, Ba, and Ca, are closely related to sedimentary environments and thus provide a novel method for discriminating the sedimentary facies of river mouth. In this study, 50 surface water and surface sediment samples were obtained from different geomorphological units of the Jiulong River mouth, i.e., river channel, distributary channel, delta front, delta front slope, prodelta, and shallow marine area, and the salinity of the water, the grain size, and the Sr, Ba, and Ca contents and Sr/Ba molar ratio (Sr/Ba) in HAc leachates of the sediments were determined. Contents of alkaline earth metals in HAc leachates of surface sediments from the Changjiang (Yangtze) River coast were also collated. The goals of this study were to reveal the spatial distribution of alkaline earth metals in the Jiulong River mouth, define their depositional mechanisms, and search for effective geochemical proxies for identification of the various sedimentary facies in the fluvial to marine transition zone. The results revealed several land-to-sea gradients. The Ba content decreased rapidly from the distributary channel to the sea, and the Sr and Ca contents and Sr/Ba increased gradually with the increase in salinity. Salinity, marine biomass, and sedimentary dynamic processes, were speculated to be the main reasons for the differences in their spatial distributions. There were significant differences in Ba, Sr, Ca, and Sr/Ba between the river channel and the distributary channel, in Ca and Ba between the distributary channel and the delta front (slope), and in Sr, Ca, and Sr/Ba between the delta front (slope) and the prodelta–shallow marine region. The Sr–Ba scatterplot showed that the sediments of the river channel and alluvial plain were located as a high Ba and low Sr element-defined end-member, whereas samples of the prodelta and shallow marine formed a high Sr and low Ba end-member. These can be used as characteristic end-members indicating terrestrial facies and marine facies, respectively. The sediments of the delta plain, tidal river, distributary channel, delta front, and delta front slope are located between these two end-member regions of the scatterplot, and this region of the diagram can be used to identify land–sea transitional sedimentary facies.
2024, 43(11): 68-87.
doi: 10.1007/s13131-024-2380-1
Abstract:
The biological pump, driven by phytoplankton production and death, plays a crucial role in the ocean’s sequestration of atmospheric CO2. In particular, marginal seas with high primary productivity show a significant capacity for carbon fixation. Variations in phytoplankton biomass and community structure are key factors influencing the efficiency of the marine biological pump. The Taiwan Strait (TS) is a unique shallow conduit that connects the East China Sea (ECS) and the South China Sea (SCS), which are subject to seasonal monsoons and episodic events (e.g., typhoons and floods). Thus, its planktonic ecosystem is significantly influenced by physical processes such as strong ocean currents, coastal upwelling and river discharge, resulting in noticeable seasonal variability. In this study, we examined spatiotemporal patterns of phytoplankton biomass and community structure using phytoplankton-sourced biomarkers from suspended particles in surface waters across all four seasons from 2019 to 2020 in the TS. The findings highlight notable seasonal disparities in phytoplankton biomass, with spring and summer exhibiting significantly higher levels compared to autumn and winter. In order to determine phytoplankton ecosystem responses to various physical and biological processes on a seasonal scale, we used Empirical Orthogonal/Eigen Function (EOF) analysis to investigate the covarying spatiotemporal patterns of: marine-sourced biomarkers and terrestrial-sourced biomarkers in surface suspended particles, a biomass indicator (Chl a), water-mass indicators [sea surface temperature (SST), sea surface salinity (SSS), nutrients], and a hydrodynamic indicator [total suspended solids at surface/bottom water, (TSS_S and TSS_B)]. The results identified six physical-biological coupling modes that influence seasonal variations in marine phytoplankton ecosystems within the energetic strait system. Additionally, an in-depth understanding of the coupling between physical process and lipid biomarker signals from suspended particles in the contemporary marine environment can offer valuable insights for interpreting ancient sediment records of phytoplankton ecosystem evolution in the TS.
The biological pump, driven by phytoplankton production and death, plays a crucial role in the ocean’s sequestration of atmospheric CO2. In particular, marginal seas with high primary productivity show a significant capacity for carbon fixation. Variations in phytoplankton biomass and community structure are key factors influencing the efficiency of the marine biological pump. The Taiwan Strait (TS) is a unique shallow conduit that connects the East China Sea (ECS) and the South China Sea (SCS), which are subject to seasonal monsoons and episodic events (e.g., typhoons and floods). Thus, its planktonic ecosystem is significantly influenced by physical processes such as strong ocean currents, coastal upwelling and river discharge, resulting in noticeable seasonal variability. In this study, we examined spatiotemporal patterns of phytoplankton biomass and community structure using phytoplankton-sourced biomarkers from suspended particles in surface waters across all four seasons from 2019 to 2020 in the TS. The findings highlight notable seasonal disparities in phytoplankton biomass, with spring and summer exhibiting significantly higher levels compared to autumn and winter. In order to determine phytoplankton ecosystem responses to various physical and biological processes on a seasonal scale, we used Empirical Orthogonal/Eigen Function (EOF) analysis to investigate the covarying spatiotemporal patterns of: marine-sourced biomarkers and terrestrial-sourced biomarkers in surface suspended particles, a biomass indicator (Chl a), water-mass indicators [sea surface temperature (SST), sea surface salinity (SSS), nutrients], and a hydrodynamic indicator [total suspended solids at surface/bottom water, (TSS_S and TSS_B)]. The results identified six physical-biological coupling modes that influence seasonal variations in marine phytoplankton ecosystems within the energetic strait system. Additionally, an in-depth understanding of the coupling between physical process and lipid biomarker signals from suspended particles in the contemporary marine environment can offer valuable insights for interpreting ancient sediment records of phytoplankton ecosystem evolution in the TS.
2024, 43(11): 88-98.
doi: 10.1007/s13131-024-2381-0
Abstract:
The characteristics of the terrain of a strait can lead to a “fine tube” effect that enhances a monsoon and thereby affects the physical, chemical, and biological processes of marine ecosystems. This effect is a highly dynamic and complex phenomenon involving interactions among atmospheric, oceanic, and terrestrial systems, as well as biogeochemical cycles and biological responses driven by it. However, current understanding has been focused mainly on the differences between monsoons, and there have been few studies concerned with the weakening or strengthening of monsoons. To explore the biogeochemical and phytoplankton responses during varying intensities of the northeast (NE) monsoon in the Taiwan Strait, high-resolution, across-front observations combined with FerryBox online data and satellite observations were conducted in this study during a strong, moderate, and weak NE monsoon. The spatiotemporal changes of nutrient concentrations and phytoplankton communities were regulated by the dynamics of ocean currents forced by NE winds. The weakening of the NE monsoon caused shrinkage of the coastal currents that led to a reduction of nutrient concentrations and an alteration of the distribution patterns of phytoplankton communities along cross-front sections. Specifically, there was a notable decrease in the proportions of dinoflagellates and cryptophytes in inshore regions and of prasinophytes in offshore areas. This study showed for the first time the dynamics of phytoplankton with changes of ocean currents during varying intensities of the NE monsoon in a strait system. The findings helped to elucidate the general spatial patterns of the phytoplankton community based on satellite-derived surface temperature and wind patterns and further enhanced the understanding of biogeochemical cycles in marine systems.
The characteristics of the terrain of a strait can lead to a “fine tube” effect that enhances a monsoon and thereby affects the physical, chemical, and biological processes of marine ecosystems. This effect is a highly dynamic and complex phenomenon involving interactions among atmospheric, oceanic, and terrestrial systems, as well as biogeochemical cycles and biological responses driven by it. However, current understanding has been focused mainly on the differences between monsoons, and there have been few studies concerned with the weakening or strengthening of monsoons. To explore the biogeochemical and phytoplankton responses during varying intensities of the northeast (NE) monsoon in the Taiwan Strait, high-resolution, across-front observations combined with FerryBox online data and satellite observations were conducted in this study during a strong, moderate, and weak NE monsoon. The spatiotemporal changes of nutrient concentrations and phytoplankton communities were regulated by the dynamics of ocean currents forced by NE winds. The weakening of the NE monsoon caused shrinkage of the coastal currents that led to a reduction of nutrient concentrations and an alteration of the distribution patterns of phytoplankton communities along cross-front sections. Specifically, there was a notable decrease in the proportions of dinoflagellates and cryptophytes in inshore regions and of prasinophytes in offshore areas. This study showed for the first time the dynamics of phytoplankton with changes of ocean currents during varying intensities of the NE monsoon in a strait system. The findings helped to elucidate the general spatial patterns of the phytoplankton community based on satellite-derived surface temperature and wind patterns and further enhanced the understanding of biogeochemical cycles in marine systems.
2024, 43(11): 99-117.
doi: 10.1007/s13131-024-2431-7
Abstract:
As the most important component of marine siliceous organisms, diatoms are vital primary producers of the ocean that are often used as indicators of paleoenvironmental change. To understand the response of sedimental diatoms to regional environmental changes and the factors affecting the distribution of sedimental diatoms in the Taiwan Strait, this study quantified and classified the diatoms found in surface sediments collected during four surveys from 2019 to 2020. Overall, 118 diatom taxa and 44 genera were identified with total diatom abundance of 8–27 353 valves/g. Four diatom assemblages representing different environments were identified. Among them, assemblage Ⅰ represented a coastal environment, assemblage Ⅱ comprised warm water species of a coastal environment, Assemblage Ⅲ represented a coastal environment affected markedly by exorheism, Assemblage Ⅳ represented a group with lowest diatom abundance. Seasonal variation in total diatom abundance was controlled by seven environmental factors: depth, sea surface salinity, mean grain size, silicate, nitrite, nitrate, and phosphate. Spatiotemporal variation in each of the diatom assemblages was substantial and strongly affected by various currents, upwelling, and low-salinity water. Specifically, it was found that the succession of diatom assemblages reflects change in the range of influence of local warm currents.
As the most important component of marine siliceous organisms, diatoms are vital primary producers of the ocean that are often used as indicators of paleoenvironmental change. To understand the response of sedimental diatoms to regional environmental changes and the factors affecting the distribution of sedimental diatoms in the Taiwan Strait, this study quantified and classified the diatoms found in surface sediments collected during four surveys from 2019 to 2020. Overall, 118 diatom taxa and 44 genera were identified with total diatom abundance of 8–27 353 valves/g. Four diatom assemblages representing different environments were identified. Among them, assemblage Ⅰ represented a coastal environment, assemblage Ⅱ comprised warm water species of a coastal environment, Assemblage Ⅲ represented a coastal environment affected markedly by exorheism, Assemblage Ⅳ represented a group with lowest diatom abundance. Seasonal variation in total diatom abundance was controlled by seven environmental factors: depth, sea surface salinity, mean grain size, silicate, nitrite, nitrate, and phosphate. Spatiotemporal variation in each of the diatom assemblages was substantial and strongly affected by various currents, upwelling, and low-salinity water. Specifically, it was found that the succession of diatom assemblages reflects change in the range of influence of local warm currents.
2024, 43(11): 118-130.
doi: 10.1007/s13131-024-2437-1
Abstract:
The Macao Special Administrative Region is located in the southeastern coastal area of China. The region of Macao was narrow in the history, so land reclamation has become a main means of expanding its geographical scope. Exploring the significance of land reclamation for the planning and urban construction of the Macao region provides valuable references. (1) The Google Earth Engine (GEE) cloud processing platform is used in this study to calculate the modified normalized difference water index (MNDWI) based on Landsat data from 1986 to 2021; (2) the Jenks natural index classification method is used to extract the water body range, and the water body boundary as well as area at different periods is calculated combined with the neural network classification method in the environment for visualizing images (ENVI) software; (3) this study then combines the patch-generating land use simulation (PLUS) model to predict the future trend of shoreline changes in the study area in 2036. The result indicates that the MNDWI and neural net classification method lead to a high classification accuracy with both the overall accuracy (OA) and Kappa coefficient being higher than 87%. Land reclamation activities in Macao were gradually intense from 1986 to 2021, with social and economic conditions such as transportation being main influencing factors, which provides valuable references and inspiration for the regional planning of the Macao Special Administrative Region.
The Macao Special Administrative Region is located in the southeastern coastal area of China. The region of Macao was narrow in the history, so land reclamation has become a main means of expanding its geographical scope. Exploring the significance of land reclamation for the planning and urban construction of the Macao region provides valuable references. (1) The Google Earth Engine (GEE) cloud processing platform is used in this study to calculate the modified normalized difference water index (MNDWI) based on Landsat data from 1986 to 2021; (2) the Jenks natural index classification method is used to extract the water body range, and the water body boundary as well as area at different periods is calculated combined with the neural network classification method in the environment for visualizing images (ENVI) software; (3) this study then combines the patch-generating land use simulation (PLUS) model to predict the future trend of shoreline changes in the study area in 2036. The result indicates that the MNDWI and neural net classification method lead to a high classification accuracy with both the overall accuracy (OA) and Kappa coefficient being higher than 87%. Land reclamation activities in Macao were gradually intense from 1986 to 2021, with social and economic conditions such as transportation being main influencing factors, which provides valuable references and inspiration for the regional planning of the Macao Special Administrative Region.
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