East China Sea Research Articles

Fault Characteristics and Reservoir Potential of Mesozoic Basins in the Southern East China Sea

The East China Sea Basin (ECSB) is an integral part of the Western Pacific tectonic system. Its development is linked to the Kula–Pacific Plate and the formation and expansion of the Philippine Sea Basin. Recent advancements in exploration technologies and theory have been applied to Mesozoic basins in the East China Sea. Researchers have posited that the southern basin has great oil and gas exploration potential. However, the characteristics and evolution of fault structures and their influence on hydrocarbon accumulation remain unclear. Here, in-depth geometric and kinematic analyses of Mesozoic fault structures in the southern ECSB were conducted using the latest interpretations of 2D seismic data and structural analysis theory. The findings revealed that the fault system was well developed and predominantly exhibited multiphase extensional and extensional-torsional features. Based on their lateral distribution and morphology, faults were categorized into three structural styles and seven combinations. According to their developmental timing, periods of active faulting were attributed to the Yanshan and Himalayan epochs. Multiphase fault activities strongly controlled the formation of traps and thus hydrocarbon accumulation, while earlier NE-trending faults controlled the formation of structural belts and hydrocarbon source areas.

Patterns and mechanism of wintertime penetrating fronts in the East China Sea

Patterns and mechanism of wintertime penetrating fronts in the East China Sea

The flyway construct and assessment of offshore wind farm impacts on migratory marine fauna

Abstract The flyway construct was developed in the 1930s to protect networks of bird stopover habitats along annual migration circuits. Here flyway is conceived as a quantifiable vector, a construct of the seasonal velocity and the geographic route taken among networked habitats, generalizable among marine migratory animals, and a way forward in assessing regional offshore wind (OW) development impacts. OW development in the South and East China Sea, North Sea, and US Mid-Atlantic Bight will result in thousands of offshore wind turbines that transect coastal and shelf flyways, not only for birds but also for fishes, sea turtles, and marine mammals. With increased capacity to fully measure the extent and dynamics of migrations through electronic tracking and observing systems, avian-like behaviors are apparent for whales, turtles, and fishes, such as stopover behaviors, migration synchrony, and partial migration. Modeled northwest Atlantic flyways (migration vectors) for northern gannets, striped bass, and North Atlantic right whale quantified seasonal speed, persistence, and variance during seasonal migration phases. From these flyway models, a series of flyway metrics are proposed that lend themselves to hypothesis-testing, dynamic habitat models, and before–after impact assessment. The flyway approach represents a departure from current impact designs, which are dominated by local OW farm studies and, at regional dimensions, survey-based (Eulerian) data structures (overlap models). As a next step, we encourage colleagues to develop flyway databases and test flyway hypotheses for model species.

Archaeal community from the Northern Hangzhou Bay to the East China Sea: biogeography, ecological processes, and functional potential

IntroductionArchaeal communities play a crucial role in marine ecosystems, yet our understanding of their ecological and functional traits remains incomplete. This study focuses on northern Hangzhou Bay to fill gaps in knowledge regarding the biogeography and functionality of archaeal groups.MethodsWe utilized a high-throughput sequencing dataset based on the 16S rRNA gene to characterize the archaeal community, aiming to identify biogeographic patterns and assess the influence of environmental factors on community structure.ResultsThe predominant phyla identified were Woesearchaeota, Thaumarchaeota, Euryarchaeota, and Crenarchaeota. Archaeal community structure in sediments showed a geographical pattern along the environmental gradient, influenced by factors such as salinity, ammonium, total phosphorus, pH, and total nitrogen content. Network analysis revealed nonrandom co-occurrence patterns, with associations changing along the salinity gradient. Additionally, this study directly proved the existence of dispersal limitation in this strongly connected marine ecological system through null model analyses. Variation in the archaeal community was attributed to both environmental constraints and stochastic processes due to dispersal limitation. Furthermore, our results revealed that the key biogeochemical functions of the archaeal community also exhibited a clear salinity gradient, the functional differences appear to be influenced by salinity, and the critical roles of archaeal diversity were highlighted.DiscussionAll these findings enhance our understanding of microbial ecology and element transformation in estuarine environments. The highlighted roles of archaeal diversity and the influence of environmental factors on community structure and function underscore the complexity of marine microbial ecosystems.

Fine spatio-temporal prediction of fishing time using big data

Overfishing, bycatch, and other anthropogenic threats may lead to the destruction of fragile habitats and substantial losses of marine life. Marine fishery resources can be protected by adjusting fishing intensity and establishing marine reserves. Currently, China adopts the closed fishing season management approach to protect traditional fishing grounds, where fine spatio-temporal prediction is essential to efficiently supervise the wide scope. Fishing vessel behaviors reflect fishers’ experience as well as the information provided by fish detection radar, while the fishery resource distribution is relevant to the marine environment. In this study, we identified fishing vessel behaviors (gillnets, trawls, purse seines, and abnormal behaviors) and qualitatively assessed and predicted fishing time of different fishing vessel behaviors to search for high intensity fishing operation areas by constructing a time-space prediction model. The model was based on big data of fishing vessel automatic identification systems and3 the marine environment, and was verified in the East China Sea. The prediction results generally corresponded with the distribution of traditional fishery resources in the East China Sea and the fishing efforts provided by the Global Fishing Watch. This model can provide an accurate and effective refined fishing vessel operation time prediction, and benefits fishing management and fishery resources protection.

Comparative analysis of diffusion length based on the volume scattering function measurements from the East and South China Seas

Comparative analysis of diffusion length based on the volume scattering function measurements from the East and South China Seas

Development of arcuate faults and controls on hydrocarbon accumulation in the Tiantai slope, Xihu Depression, East China Sea basin

The strike-slip movement of NW-trending transfer zone in the Tiantai slope of the Xihu Depression governed the development of the Cenozoic arcuate faults. These faults significantly influenced trap formation, sand-bodies distribution, and hydrocarbon migration. Based on seismic, drilling data and fault activity analysis methods, this paper describes the origin and evolution of the arcuate faults and their impact on hydrocarbon accumulation. These arcuate faults exhibit a change from NE to NW strike orientation in plan view, and are distributed in the hanging wall of the NW-trending basement faults. The main arcuate faults penetrate the bottom of the Cenozoic strata and extend upward through the top of the lower member of the Huagang Formation, markedly affecting the depositional dynamics of the Pinghu Formation. The segments of the arcuate faults began to grow during the Middle Eocene, and experienced hard linkages in the Late Eocene. The activity of these arcuate faults diminished significantly and gradually stopped during the Middle and Late Oligocene. The segmentation and linkage growth processes of the arcuate faults controlled the formation and evolution of traps. Additionally, the activities of these faults influenced the distribution of sandbodies, with the segmentation points of the arcuate faults serving as important conduits for sediment input. Moreover, the arcuate faults served as effective pathways for vertical hydrocarbon migration. The area with the arcuate faults present favorable conditions for hydrocarbon accumulation in the Tiantai slope of the Xihu Depression.

The Mesoscale SST–Wind Coupling Characteristics in the Yellow Sea and East China Sea Based on Satellite Data and Their Feedback Effects on the Ocean

The Mesoscale SST–Wind Coupling Characteristics in the Yellow Sea and East China Sea Based on Satellite Data and Their Feedback Effects on the Ocean

Evaluation of the stock enhancement effect of Phascolosoma esculenta on macrobenthic communities using diversity and biotic indices in Yueqing Bay, East China Sea

Stock enhancement activities have many benefits but also negative impacts. The macrobenthic diversity index and the M-AMBI index were adopted to assess the effects of stock enhancement of Phascolosoma esculenta on macrobenthic communities and the local ecosystem in Yueqing Bay. The results revealed that the Shannon–Wiener diversity index (H’) and Margalef richness index (d) increased in October 2022 after stock enhancement, indicating a positive ecological restoration effect. The average M-AMBI in the intertidal zone of Yueqing Bay was 0.59, indicating good benthic ecological quality. Excluding seasonal factors, the M-AMBI in the intertidal zone increased after stock enhancement, indicating that stock enhancement by Phascolosoma esculenta had a certain positive effect on the intertidal ecological environment of Yueqing Bay. The increase in the M-AMBI occurred mainly in the low-tide zone, increased slightly in the mid-tide zone, and remained basically unchanged in the high-tide zone. On the one hand, Phascolosoma esculenta can accumulate heavy metals from the environment and release a large amount of organic matter throughout its lifecycle, promoting nutrient cycling, which plays a positive role in the environment. On the other hand, Phascolosoma esculenta is an economic species; however, the planting of mangroves in the low tide zone causes fishers to fish in the mid- and high-tide zones, so the changes in the M-AMBI values in each tidal zone are related mainly to Phascolosoma esculenta and anthropogenic disturbances.

Stock exploitation status of silver croaker (Pennahia argentata) from the East China Sea

Silver croaker (Pennahia argentata) is an important economic species in the East China Sea (ECS); however, its population has been declining, and studies on its status are scarce. This study collected biological data, including length, weight, and gonadal maturity of silver croaker from the southern coastal waters of Zhejiang Province between 2015 and 2021, to evaluate its life history and assess stock status. Methods from the TropFishR package were employed to estimate population growth and natural mortality parameters. Two widely used length-based data-limited models, length-based bayesian biomass estimation method (LBB) and length-based spawning potential ratio method (LBSPR), were applied to assess the stock status of silver croaker in the ECS. The results indicated that with a maximum age (Amax) of 4 years, the asymptotic length (Linf) was 23.80 cm, growth rate (K) was 0.74/year, and natural mortality coefficient (M) ranged from 1.068 to 1.376. Under the assumption of Amax = 5 years, Linf was 26.77 cm, K was 0.63/year, and M ranged from 0.818 to 1.193. The LBB and LBSPR models showed that, except for scenarios with L∞ = 23.8 cm, M/K = 1.46, and L∞ = 26.77 cm, M/K = 1.30, 1.38, or 1.48, the selectivity at length parameters L50SandL95S for silver croaker exhibited an increasing trend over the years. In the LBB model, L50S for different years consistently fell below the optimum length (Lc_opt), indicating that most individuals did not reach the size at first sexual maturity or optimal catch length. Moreover, under high fishing pressure, the Spawning Potential Ratio (SPR) and the unfished biomass ratio (B/B0) for silver croaker showed a decreasing trend, despite some stability or recovery in recent years. However, in all scenarios, SPR values were below 0.2, and B/B0 values were below 0.5, suggesting a significant risk of population collapse for silver croaker in the ECS due to intense fishing pressure. Therefore, it is recommended to reduce the current fishing pressure and increase the minimum catch size of this species for effective conservation and management in this region.

Strong seasonality and unsuspected diversity of haptophytes explored by metabarcoding analysis in the Chinese seas

The haptophytes, are essential components of the marine pico- and nano-plankton but little is known about their diversity and abundance due to the small size. In this study, the taxonomic composition, geographical distribution, and seasonal variation of the haptophytes in the Bohai Sea, the Yellow Sea, and the East China Sea were investigated using DNA metabarcoding in April and October of 2021. A total of 623 and 3756 haptophyte amplicon sequence variants (ASVs) were obtained in spring and autumn, respectively. All currently described or detected haptophyte orders were retrieved, including several deep-branching novel environmental lineages with relative high abundance. The predominant groups were Chrysochromulina, Clade HAP 2-3-4-5, Phaeocystis, and Prymnesium in spring, and Chrysochromulina, Phaeocystis, and Emiliania/Gephyrocapsa Compelx in autumn. The richness and diversity showed seasonal variation, with higher alpha diversity occurred in autumn than that of spring. Different haptophyte taxa exhibited unique spatial distribution patterns and water temperature was significantly correlated with the observed community dissimilarities and was the most influential driving factor in both seasons. Our results highlight the high hidden diversity and seasonal variations of haptophytes in the Chinese seas.

Heterogeneous Sources, Distribution, and removal processes of dissolved black carbon from East China Sea shelf to open ocean of Northwest Pacific

Heterogeneous Sources, Distribution, and removal processes of dissolved black carbon from East China Sea shelf to open ocean of Northwest Pacific

Sediment source-to-sink patterns along the southeast China coast during the late Quaternary: New insights from sediment geochemistry and OSL ages in Ningde Bay

The geomorphology and environmental conditions of the southeast China coast are significantly influenced by sediment discharge from the Yangtze River, a major river located to the north. Nonetheless, the extent to which the Yangtze River affects sediment transport processes from source to sink along the southeast coast remains unclear. Our recent findings in coastal/marine deposits from the late Quaternary period (MIS5e, MIS3, and MIS1) in Ningde Bay offer new perspectives on this issue. Provenance discrimination of the late Quaternary boreholes was carried out using sediment geochemical analysis and OSL dating of fine- and medium-grained quartz. The results indicate varying provenances during sea-level fluctuation, with distal Yangtze River origins during MIS5e, MIS3, and MIS1, and a local source during MIS4. The findings also suggest that the southward transport of Yangtze sediments along the southeast China coast has occurred since MIS5e. However, OSL ages of the fine-grained quartz in the MIS3 deposit range from approximately 90 to 140 kyr, notably older than those of medium-grained quartz (40–80 kyr). This remarkable age discrepancy indicates that Yangtze-derived sediments previously deposited on the shelf of the East China Sea during MIS5 were reworked and transported southward in MIS3. This phenomenon can be elucidated by the insufficient supply of Yangtze sediments during MIS3, which could be linked to the weakened East Asian monsoon. This new source-to-sink pattern for the southeast China coast is characterized by a compensating mechanism of inner shelf old sediment in response to the inadequate supply of Yangtze sediments. This study contributes to a better understanding of the significant impacts of reduced Yangtze sediment input on its distal sedimentary systems over time.

Trough‐Scale Slope Countercurrent Over the East China Sea Continental Slope Driven by Upwelling Divergence

AbstractObservations have revealed the existence of persistent slope countercurrents (SCCs) that flow southwestward beneath the Kuroshio Current at several locations over the East China Sea (ECS) continental slope. It was not clear whether these flows are localized circulation features or segments of a trough‐scale circulation system in the Okinawa Trough (OT). We demonstrate that there indeed exists a potentially continuous trough‐scale SCC along the ECS slope that is associated with an OT‐wide cyclonic circulation using high‐resolution model simulations and physical interpretations. The detailed features of the deep OT circulation are illustrated by the trajectories of the Lagrangian drifters and the time‐varying distributions of passive tracers. The SCC in the ECS is characterized by its weak yet persistent nature, typically located in narrow sloping regions at the isopycnal layer of 26.6–27.3 kg m−3. It exhibits a characteristic speed of approximately O‐(1) cm s−1. Analyses and experiments suggest that the divergence of upwelling in the SCC layer (26.6–27.3 σθ surface) gives rise to lateral potential vorticity transport, ultimately driving the deep cyclonic circulation. Furthermore, the SCC also displays a substantial connection with the onshore intrusion of the Kuroshio Current, particularly to the northeast of Taiwan Island. The SCC may potentially play a crucial role in the transport of heat and nutrients, as well as in regulating sediment distributions within the deep OT. This mechanism offers fresh insights into explaining the presence of undercurrents in semi‐enclosed marginal seas.

Importance of dissolved organic nutrients on nutrient stoichiometry in the Yellow Sea and the East China Sea

We investigated seasonal variations in the dissolved nutrients and organic matter (DOM) in the Yellow Sea and the East China Sea shelf waters from 2017 to 2021. Dissolved organic nitrogen and phosphorus (DON and DOP) concentrations were the highest in the upper layer (<30 m) during the time of spring and autumn bloom and were the lowest in summer. In spring, DON and DOP contributed up to approximately 90% and 80% of the total dissolved nitrogen (TDN) and phosphorus (TDP), respectively. The C:N:P stoichiometry of the DOM pool in spring and autumn indicates that freshly in-situ produced DOM is N-rich compared to the DOM observed in summer and winter, resulting in a dissolved inorganic nitrogen (DIN)-limited environment in the upper layer of seawater during spring and autumn. Conversely, in summer, the highest C:N ratios (∼27) of the DOM pool revealed the DOM remained after the degradation and formation of the refractory pool by marine bacteria. In winter, all nutrients were vertically uniform due to active vertical mixing. This study highlights notable seasonal variations in the cycling of DON and DOP, leading to changes in their bioavailability and subsequent ecosystem responses in the shelf sea.

Thermal stability of sedimentary organic carbon in a large river dominated marginal sea

The thermal stability of organic carbon (OC) in marine sediments is one of the critical factors that influences its burial efficiency in marine environments. However, the distribution patterns and influencing factors of the thermal stability of OC in marginal seas remain poorly understood. In this study, we conducted the thermal gravimetric analysis (TGA) of OC in surface sediments of the Changjiang Estuary (CE) and its adjacent East China Sea (ECS) shelf. Both labile and refractory organic matter (OML and OMR) contents derived from the TGA were higher in the CE and Zhe-Min Coast (ZMC) mobile muds relative to those in the sandy areas. The average Carbon Reactivity Index (CRI) is 69.3 ± 4.2 %, ranging from 62.8 % to 85.1 %. Most of the stations in the CE and ZMC mobile muds were characterized by relatively low CRI values, while only some stations in the inner estuary and outer shelf had higher CRI values. As a result, the CRI values correlated reversely with the OC contents and positively with the median grain size, especially in sandy sediments. Despite being sandy sediments, there were significant differences in the thermal stability of OC among the three different sandy sediment areas, with the highest CRI value in the inner estuary, lower CRI values in the outer estuary and outer shelf sediments, possibly related to the sources and composition of OC in different regions as shown by the negative correlation between CRI and δ13C for sandy sediments. Compared with certain European marginal seas, the sedimentary OC (SOC) in the CE and ECS shelf exhibits greater thermal stability, which is probably linked to the reduced preservation efficiency of OC caused by the extensive sediment dynamics in this area. This study supports the notion that organo-mineral interactions and the sources are two major factors controlling the reactivity of OC.

ENSO modulates soil organic carbon retention and deposition in the East China Sea

Accurately quantifying the contribution of terrestrial soil organic carbon (SOC) in marine environment is still a challenge. Moreover, reassessing the effect of climate change on SOC variability is necessary, with the increasing variability of El Niño under greenhouse warming. Here, we present new insights from bacterial 3-hydroxy fatty acids (3-OH-FAs) by systematically analyzing the distributions of 3-OH-FA in soils, lake/river sediments and marine sediments, and propose a novel proxy (RIA, the ratio of odd carbon number iso to anteiso 3-OH-FAs) to quantificationally evaluate the contribution of OC from different components. The reliability of the RIA proxy is tested by using a three end-member model and Monte Carlo simulations along a transect from the Yangtze River estuary to the ECS shelf. Then the RIA proxy is applied to a core in the East China Sea covering the past 700 years, and the results reveal that El Niño (La Niña) induced more (less) precipitation and increased (decreased) SOC deposition. This study provides a novel approach for quantifying terrigenous OC inputs and burial in marginal seas and shows the impact of El Niño-Southern Oscillation (ENSO) modes on SOC loss and burial in marginal seas under global warming.

Analysis of the Interrelation and Seasonal Variation Characteristics of the Spatial Niche of Dominant Fishery Species-A Case Study of the East China Sea.

The spatial niche has garnered significant attention in ecological research, particularly regarding species distribution patterns. The East China Sea, known for its favorable natural conditions and abundant fishery resources, exhibits diverse spatial distribution patterns among species, shaped by their seasonal physiological needs. This study utilized a habitat suitability index model to explore the spatial distribution patterns of key fishery resources in the East China Sea across four seasons and their interactions. Two methodologies were employed to identify key environmental factors and assess the ecological niche overlap among different species and seasons. Results indicated that the initial method identified water temperature as the critical factor for hairtail, while the subsequent method emphasized water temperature and salinity for hairtail, salinity for small yellow croaker, and water depth for Bombay duck. The main spatial habitat overlap was observed between paired species, likely driven by predator-prey interactions. During summer and autumn, increased overlap among multiple species was primarily influenced by synchronized life cycles. An overlap index formula quantified the seasonal species overlap, showing an increase from spring to winter, reflecting changes in convergent habitat preferences. The peak overlap occurred in winter, driven by overwintering, reduced food competition, and enhanced coexistence potential, while the lowest overlap was noted in spring as overwintering ended and predation and competition intensified.

Combined Effects of Fishing and Environment on the Growth of Larimichthys polyactis in Coastal Regions of China

In fisheries’ stock assessments, the concept of “growth plasticity”—the ability of organisms to modulate their growth rates in response to environmental conditions—has gained attention in recent years. Historically, the impacts of fishing activities and environmental fluctuations were considered separately, while their combined effects have recently come into focus. This study collected 834 adult small yellow croakers (Larimichthys polyactis) from the northern Yellow Sea, the central Yellow Sea, the southern Yellow Sea, and the northern East Sea by trawling during 2020–2021. Using otolith increments as a proxy for annual somatic growth, the study reconstructed otolith chronologies during 2015–2020 for these four stocks. The results of the mixed-effects modeling suggested that temperature during spawning and previous overwintering seasons had comparable importance for the annual growth of small yellow croakers, with higher temperature promoting growth. The growth of small yellow croakers was also found to be correlated with ENSO events, with a lag of 1 to 2 years. A further investigation into combined effects revealed that higher fishing pressure might inhibit the small yellow croaker’s response to favorable environmental conditions. Furthermore, considering the potential differences in growth plasticity among stocks, an analysis was conducted on the spatial variations in growth response to these factors. The analysis revealed that, compared to the stocks in the Yellow Sea, the stock from the East China Sea could exhibit higher growth, superior adaptability to temperature, and a distinctive response to fishing pressure. In conclusion, the present study, while primarily focusing on temperature, preliminarily analyzed the combined effects of fishing and environment and underscored the differences in growth plasticity between stocks in the Yellow Sea and the East China Sea. Despite the limited factors analyzed in this study, it suggests a direction for future studies, highlighting the necessity to include more environmental factors, and even population factors (e.g., the biomass of preys), for a more comprehensive understanding of the combined effects. Based on the observed differences between the two potential subpopulations, this study also provides new insights for the management of the small yellow croaker based on metapopulation dynamics.

Microeukaryotic communities varied along the gradient in the seaweed habitats: A case study in a typical reef island in the East China Sea

Seaweeds are ecologically important primary producers, forming unique habitats. Microeukaryotes are pivotal in ecological functioning of seaweeds, but their ecological role and processes in seaweed habitats remain poorly understood due to a lack of field data. Here we presented an innovative insights into the microeukaryotic communities along the seaweed habitat gradients using 18S rDNA sequencing around a typical reef island, Gouqi Island. We set and verified habitat gradients of brown (HB, mainly Sargassum) and green algae (HG, mainly Ulva), and the control site between them (M), with detritus samples collected from collectors by SCUBA (Self-Contained Underwater Breathing Apparatus). Along the seaweed habitats, microeukaryotic biodiversity decreased from the detritus close to the seaweed habitats to surface water with increasing distance from detritus. For the dominant ecological function, clear distinction was also found in detritus and water samples along the seaweed habitat gradient, where phototrophs, mixotrophs and phagotrophs dominated in the detritus of brown algae dominated site, medium site, and green algae dominated site, respectively, responding differently to the environmental factors and seaweeds by Mantel analysis. Furthermore, we found that stochastic processes dominated in microeukaryotic community assembly in the brown seaweed habitat whereas deterministic processes dominated in green algae habitat. Highly varied occupancy was revealed in the green algae habitat by Specificity-Occupancy (SPEC-OCCU) analysis. Our result contributed to a better understanding of the ecological functioning of microeukaryotic communities in seaweed habitats, and further provided data for the bioassessment and conservation of seaweed habitats within marine ecosystems.