East China Sea Research Articles

Effective law enforcement in gray zone operations: A Chinese perspective of coastguard law implementation in delimited maritime zones

The states attempt to claim more areas in maritime zones to control the oceans and their resources effectively. This position has led many states into disputes and conflicts in the maritime zones, and such unsettled zones are known as 'gray zones'. The 'gray zones' of the East China Sea and South China Sea (together East and South China Seas) challenge the effective enforcement of the law because of the ambiguity in the law of the sea and its interpretation by international courts and tribunals. In the East and South China Seas, law enforcement in gray zones has raised many concerns about maritime security, illegal fishing, terrorism, and piracy. The conflict among the states neighboring the East and South China Seas hinders the effective enforcement of the law. Against this backdrop, this research paper suggests that insensitive forces such as the coastguard of states in dispute shall cooperate for effective law enforcement in gray zones. This paper argues that if enforcement actions are legitimate with lawful grounds and reasonable measures, such cooperation will not escalate disputes among states. In the East and South China Seas, the cooperation for effective law enforcement by coastguards will depend on the continuous overcoming of uncertainties in international law until the conflicting states reach a consensus on the competitive interpretation of law by the international courts and tribunals.

Using alpha, beta, and zeta diversity to map the structure and function of fish community in the central East China Sea

Using alpha, beta, and zeta diversity to map the structure and function of fish community in the central East China Sea

Regional significant wave height forecast in the East China Sea based on the Self-Attention ConvLSTM with SWAN model

Accurate prediction of regional significant wave heights is crucial for marine resource development, especially in areas with limited wave observations. This paper proposes a method for predicting regional significant wave heights by integrating the numerical wave model Simulating Wave Nearshore (SWAN) with the spatio-temporal prediction network Self-Attention ConvLSTM. The SWAN model is used to simulate regional significant wave heights in the East China Sea. To improve simulation accuracy, calibration of wind input, whitecapping dissipation, quadruplet wave–wave interactions, and bottom friction parameterization schemes in the model source terms were conducted, resulting in a simulated correlation coefficient of 0.97 with measured significant wave heights. The regional significant wave height training dataset constructed using the SWAN model preserves the intrinsic relationships between waves, wind speed, and wind direction over a recent period. Subsequently, a regional prediction system is built based on the output of the SWAN model, integrating the self-attention mechanism into the spatio-temporal prediction model ConvLSTM to construct SA-ConvLSTM. This model extracts correlated features among regional waves from the training dataset to predict future significant wave heights at different time intervals. The prediction performance of four spatio-temporal forecasting networks was compared to verify the accuracy of the SA-ConvLSTM model. The average errors in predicting regional significant wave heights at 3, 6, and 12 h were 0.07 m, 0.09 m, and 0.09 m, respectively. The R-Square metrics for these three prediction intervals were 0.85, 0.78, and 0.7, respectively.

The impact of organic carbon mineralization on pollution and toxicity of toxic metal in sediments: Yellow Sea and East China Sea study

Organic carbon mineralization is the main driving force of metal migration and transformation in sediments, greatly influencing the distribution, pollution degree, and toxicity of toxic metals. However, relevant research on this subject is still limited. In this study, the concentration of toxic metals (Cr, Cd, Cu, Pb, Zn, Co, Fe, Mn, Ni, As) in the solid and liquid phase (porewater) of sediments were measured, toxic metal pollution degree and toxicity of the Yellow Sea (YS) and the East China Sea (ECS) were assessed. Combined with the rate of organic carbon mineralization, the impact of organic carbon mineralization was analyzed. The results showed that Ni was slightly enriched and posed a certain ecological risk, and As was moderately enriched in the studied area, Pb was at a moderate pollution level in the studied area. Zn, Co, Mn, and Fe were at a moderate pollution level in the mud area of SYS and the west coastal area of ECS. Additionally, the total organic carbon mineralization rate (TCMR) in the ECS (5.12–18.04 mmol C m−2 d−1) was slightly higher than that in the YS (3.29–14.46 mmol C m−2 d−1) during spring. Moreover, organic carbon mineralization promotes metal enrichment, and the TCMR was significantly correlated with the pollution load index. Thus, TCMR can be used as an indicator to predict the degree of metal pollution. Furthermore, organic carbon mineralization promotes the mobilization of Cu from the solid phase to the liquid phase, while facilitating the transfer of Cr, Pb, Co, Ni, and Fe from the liquid phase to the solid phase. This process increases the potential risks of Cu and reduces the toxicity of Cr, Pb, Co, Ni, and Fe. Therefore, the impact of organic carbon mineralization should be considered in future assessments and predictions of toxic metal pollution and toxicity.

Abundant small microplastics hidden in water columns of the Yellow Sea and East China Sea: Distribution, transportation and potential risk

Microplastics (MPs) pose significant concerns for marine ecological security due to their minuteness and ubiquity. However, comprehensive knowledge on their distribution and fate in seawater columns remains limited. This study investigated the abundances and characteristics of MPs across 3–6 water layers in the South Yellow Sea and East China Sea. Results indicate that high-abundance small MPs (< 100 µm) (average 6567 items/m3) were hidden beneath the sea-surface, predominantly fine-grained particles (< 20 µm) and high-density polymers (> 1.03 g/cm3). The total suspended MPs (5.0–834.2 µm) are estimated at 2.9–3.1 × 1017 particles, with most of them occurring in upper layers. In profiles, their distribution varied by physical properties with depth; fragment-shaped and high-density MPs increased in proportion at greater depths, contrasting with fibrous MPs. These MPs originated primarily from the Yangtze River and their winter transport was driven by the Yangtze River Dilution Water, East China Sea Coastal Current, and Yellow Sea Warm Current, resulting in their accumulation in coastal and estuarine regions. Consequently, the Yangtze River Estuary ecosystem faces substantial risks from MP pollution throughout the water column. This work unveils the prevalence of small MPs in coastal water columns and intricate interaction between their fate and hydrodynamic conditions.

Evaluation of Sustainable Tourism Development in Dachen Island, East China Sea: Stakeholders’ Perspective

Sustainable tourism development on small islands remains challenging because of the potential conflict of interest among relevant stakeholders. This study aims to explore the issue of sustainable tourism development in small island destinations through the example of Dachen Island in China. More specifically, this study intends to fulfill three objectives: (1) assess the stakeholders’ perception of tourism sustainable development using five major sustainability dimensions: economic sustainability, sociocultural sustainability, environmental sustainability, tourism development, and tourism management; (2) explore the major reasons for potential conflict of interest among the stakeholders; and (3) propose some conflict resolution mechanisms. Semistructured interviews were used to collect data from 29 stakeholders including locals, visitors, officials, and academicians. The findings indicated that sustainable tourism is developing rapidly on Dachen Island and our respondents showed reasonable satisfaction with the five sustainability dimensions, with emphasis placed on the potential for improving sustainable performance in the future. However, locals were less satisfied with the economic sustainability than other stakeholders. Limited conflict of interest among stakeholders was justified based on the ranking of their perceived priorities. Our findings recommend adopting responsible tourism and we highlight three conflict resolution mechanisms to ensure effective sustainable tourism development on Dachen Island, including the involvement of local communities in decision making, encouraging responsible visitor behavior, and enhancing infrastructure and services.

Precipitable water vapor retrieval for rainfall forecasting using BDS-3 PPP-B2b signal in the coastal region of China

Abstract Currently, rainfall cannot be accurately forecast because of poor network communication at the ocean. The advantage of the BeiDou Global Navigation Satellite System (BDS-3) precise point positioning (PPP-B2b) signal, which does not rely on network communication to receive data, is that it can provide precipitable water vapor (PWV) retrieval application services for the open seas in eastern China, where the communication system presents difficulties. In this study, data from stations in the coastal region of China were used to establish a rainfall forecasting method for monitoring extreme weather on the sea. First, the service performance of PPP-B2b was explored. Then, based on 17 Chinese coastal stations, the PWV accuracy was evaluated. Finally, based on an analysis of the relationship between PWV and actual rainfall, a threshold rainfall forecasting method based on a sliding window was constructed. The experimental results show that the PWV accuracy varies slightly depending on the geographic location, in which the mean absolute error in the North Sea region is the smallest (2.1 mm), that of the South China Sea region is the largest (2.60 mm), and that of the East China Sea region is in the middle (2.48 mm). The optimal predictors of the constructed 12 h sliding-window threshold rainfall prediction method are a PWV maximum of 49 mm, PWV increase of 5 mm, and PWV increase rate of 1.2 mm h−1. The prediction results can reach a critical success index value of more than 45%, indicating high prediction accuracy and applicability to the coastal region of China during the same period.

Interaction Between Typhoon, Marine Heatwaves, and Internal Tides: Observational Insights From Ieodo Ocean Research Station in the Northern East China Sea

AbstractTyphoons, fueled by warm sea surface waters, heighten concern as they increasingly interact with frequent Marine Heatwaves (MHWs) in a changing climate. Typhoon Hinnamnor (2022) weakened and re‐intensified as it approached the Korean Strait, interacting with an underlying MHW in the northern East China Sea (nECS). In‐situ observations and reanalysis products revealed a significant increase in latent heat loss from the nECS during the MHW period, contributing to the typhoon re‐intensification. Strong sea surface wind forcing with the typhoon enhanced vertical mixing and upwelling, resulting in a pronounced (0.90°C) sea surface cooling after the typhoon passage, facilitating MHW disappearance with reduced thermal stratification. During MHWs, increased background stratification increases temperature oscillations associated with semidiurnal internal tides. Furthermore, post‐typhoon changes in stratification weakened semidiurnal internal tides due to unfavorable conditions for generation from a nearby source. These findings highlight the importance of continuous time‐series observations to monitor interactions among climatic extremes.

Dominant host phase of mercury within the sediments of the East China Sea inner shelf: Implications for mercury inputs

Mercury (Hg) concentrations normalized to their dominant hosts have been widely used to identify geological events such as massive volcanic eruptions. However, the modern Hg cycle has significantly changed, and the implications of host-normalized Hg concentrations for the Hg dynamics in contemporary coastal environments (e.g., sources, delivery mechanisms, and Hg fluxes) remain poorly understood. In this study, 66 surface sediment samples from the continental shelf of the East China Sea (ECS) were analyzed, and the total organic carbon (TOC), aluminum (Al), total sulfur (TS), and Hg concentrations were determined. Our results support that organic matter predominantly hosts Hg in these sediments. Factors such as the Hg source and abundances of organic fractions influence Hg distributions, with notable enrichment in the Changjiang River estuary and the inner shelf of the ECS, especially near the mud depocenter located off the Oujiang River estuary. The oxic to suboxic redox state and the lack of significant sulfide accumulation in surface sediments suggest that sulfides are not the primary Hg hosts. The Hg/TOC ratios, ranging from 3.0 to 169.6 (ppb/%), are particularly high in the Changjiang River estuary and exhibit an exponential correlation with the Hg accumulation rates (Hg-AR). These findings suggest that the host-normalized Hg concentration could serve as a valuable tool for assessing Hg dynamics where the accumulation rates are uncertain.

Mapping the main harmful algal species in the East China Sea (Yangtze River estuary) and their possible response to the main ecological status and global climate change via a global vision

The Yangtze River Estuary (YRE) is one of the areas in China most severely affected by harmful algal blooms (HABs). This study explored the distributive patterns of HABs in the YRE and how they are influenced by the El Niño-Southern Oscillation (ENSO) and other environmental factors. Quantitative real-time PCR (qPCR) was employed to detect and quantify the four predominant HAB species in the YRE, Karenia mikimotoi, Margalefidinium polykrikoides, Prorocentrum donghaiense, and Heterosigma akashiwo. Additionally, the study analyzed how turbidity, pH, salinity, and temperature influence these algae. Distribution of the four HAB species in the YRE area shows clear geographical variations: K. mikimotoi is predominantly found in the northwest and central sea areas, M. polykrikoides (East Asian Ribotype, EAR) is mainly distributed in the southeastern part, P. donghaiense is abundant in the northern regions, and H. akashiwo is especially prevalent at stations S26 and S27 in the northeastern part of the study area. HABs dominated by H. akashiwo and P. donghaiense were observed in the northeastern sea area of the YRE on July 22, 2020. Our study reveals that K. mikimotoi, M. polykrikoides (EAR), and P. donghaiense are mainly affected by turbidity, pH, and salinity, while temperature predominantly influences the blooms of H. akashiwo. Moreover, runoff in the YRE has a certain correlation with ENSO events, which may also impact the nutrient content of the region. The findings of this study illustrate the distributive patterns of the four HAB species under various ecological conditions in the YRE and emphasize the importance of establishing practical cases for future warning systems. To better understand how climate change affects HABs, exploring the link between ENSO and HABs is essential.

Terrestrial input changes and their controlling factors as revealed by the elemental geochemical evidence in the East China Sea muddy area during the last century

Terrestrial input changes in large river-dominated marginal seas are influenced by anthropogenic and climate forces with spatiotemporal heterogeneity that has not been well clarified. In this work, based on elemental geochemical evidence of a centennial-scale sediment core from the muddy belt in the East China Sea (ECS), together with previously published organic geochemical data of the same core and selected environmental parameters, we reveal a synchronous decline in terrestrial input with enhanced anthropogenic activities after ca. 2000. The rapid decrease in 2000–2004 may be attributed to the construction of dams such as the Three Gorges Dam (TGD). During the pre-TGD period, the terrestrial input maintained stable high values (except for a distinct peak in 1965), which coincided with enhanced chemical weathering, stable annual temperature, increased precipitation, and strong East Asian winter monsoon (EAWM) driven by climatic factors. After ca. 2000, anthropogenic activities gradually became the dominant controlling factor on terrestrial input variations. In addition, significant coastal erosion recorded by Al/Si ratios during 2000–2004 and intensified nearshore eutrophication captured by δ15N values from 1950 to 1985 are linked to the construction of the TGD and increased fertilizer usage, respectively. Overall, our findings provide vital insights into modern processes using inorganic and organic geochemical proxies in marginal seas. Notably, terrestrial input and related geochemical parameters in representative cores from north to south in this region show considerable spatiotemporal variations, requiring further investigation into their underlying causes.

Trends of maximum annual sea surface temperature in the Eastern China Seas

The increasing ocean warming due to climate change significantly threatens regional marine ecosystems by raising the frequency and severity of extreme temperature events. This study examines patterns and trends of maximum annual sea surface temperature (Tmax) in the Eastern China Seas from 1985 to 2022. The results show a significant warming trend in Tmax, exceeding the global average, with notable differences between southern and northern regions. The northern Tmax warming rate is faster, with occurrence times significantly advancing, while the southern Tmax warming rate is slower, with occurrence times significantly delayed. The southern Tmax and its timing are closely correlated with the annual maximum air temperature and its timing. In the north, Tmax timing is influenced by latent heat flux (QLH); a significant increase in August QLH inhibits the continued rise of SST, causing Tmax to advance. The study also highlights a significant increase in marine heatwaves at Tmax timing, with higher Tmax indicating a higher occurrence probability. By elucidating these Tmax trends and dynamics, our study enhances understanding of regional climate impacts, supporting targeted conservation efforts and adaptive ecosystem management strategies in the Eastern China Seas.

A comparison of global and regional ocean tide models with tide gauges in the East Asian marginal seas

To enhance storm surge forecasting and establish open boundary conditions for sophistical numerical simulation of tides and tidal currents in the Bohai Sea, Yellow Sea, and East China Sea, this study evaluated the accuracy of eight global and regional tide models (EOT20, FES2014, NAO.99Jb, TPXO9, DTU16, HAMTIDE12, OSU12, and GOT4.10c) based on 41 tide gauges in the region. The differences between tide models and 8 offshore tide gauges were notable, with the root mean square (RMS) values ranging from 12.67 to 25.97 cm for M2, 6.09–13.73 cm for S2, 2.96–6.56 cm for K1, and 2.50–4.20 cm for O1. For the offshore stations, the NAO.99Jb model demonstrated superior performance with the root square sum (RSS) value of 12.63 cm among the eight tide models. For the island and coastal stations, the EOT20 model performed the best for M2 (RMS 13.03 cm), the FES2014 model for S2 (RMS 6.26 cm), and the DTU16 model for K1 and O1 (RMS 2.73 cm and 2.26 cm, respectively). Overall, the EOT20 model also exhibited the lowest RSS value (15.22 cm) among the eight models for 24 island and coastal stations. The EOT20 model slightly outperformed others with the RSS of 14.88 cm across all 32 tide gauges. Regarding the Sa tidal component, great discrepancies were found between TIDAL CONSTANTS (TICON) harmonic constant data and tide gauges. The reason for this is that the Doodson number for the Sa tidal component derived from tide gauge data, which is influenced by meteorological factors, should be (0,0,1,0,0,0), while the TICON harmonic constant data employed the Doodson number of (0,0,1,0,0,−1) corresponding to the basic astronomical variables. A correction method was proposed to adjust tidal constants from inconsistent Doodson numbers. Comparing with the harmonic constants of the Sa tidal component at 28 coastal tide stations revealed large errors in the NAO.99b, FES2014, and EOT20 models, with RMS values of 19.03, 22.08, and 13.61 cm, respectively. Consequently, caution should be taken when using the Sa results from these ocean tide models.

Characterization and source apportionment of pharmaceuticals in surface water of the Yangtze Estuary and adjacent sea.

Pharmaceuticals, which are closely linked to human activities, have attracted global attention. This study investigated the occurrence characteristics of 20 pharmaceuticals in surface water of the Yangtze Estuary and adjacent sea. A total of 14 targeted pharmaceuticals were detected in both spring and summer sampling campaigns. The mean concentrations of sulfonamides and non-sulfonamides were 36.60 ± 19.43ng·L-1 and 50.02 ± 41.07ng·L-1, respectively. As for non-antibiotics, their concentrations were in the range of 24.34 ± 916.8ng·L-1 with caffeine accounting for 6.17 ~ 86.70% (average percentage of 42.22%). Meanwhile, spatial distribution patterns showed similarities between antibiotics and non-antibiotics, with high levels occurring near the upper estuary, aquaculture areas, wastewater treatment plants, and the maximum turbidity zone. This phenomenon could be related to the sources of pharmaceuticals and the physicochemical properties of water bodies. Obviously, the first three areas are highly impacted by human activities or serve as important sources of terrestrial contaminants entering the East China Sea. The last area retains high amounts of suspended particles which may exert strong trapping effects on hydrophobic chemicals. Principal component analysis revealed the presence of three potential sources for pharmaceuticals in the Yangtze Estuary, with a relatively high percentage originating from incompletely treated municipal sewage. As for the temporal trend, pharmaceutical contamination was found to be higher in spring compared to summer, potentially due to variations in pharmaceutical consumption patterns, local rainfalls, and water temperatures. These findings provide fundamental data support for implementing appropriate local management strategies for pharmaceutical usages.

Dissolved oxygen fluctuation alters dissolved organic carbon stability and can accumulate resistant fraction

Recurrent dissolved oxygen (DO) depletion is common in many estuaries and coastal areas worldwide. However, its impact on the accumulation of resistant dissolved organic carbon (DOC) remains controversial. To address how recurrent DO depletion affects the degradation and stability of marine DOC, a series of DOC degradation incubations in a particulate-dissolved coexisting system in April 2021 were conducted, followed by a field investigation in the East China Sea (ECS) in October. In the ECS, we found that DO ranged from 4.71 to 7.40 mg/L in the near-bottom waters, while the degradation index (DI), an indicator of amino acids molecules, increased from −0.78–2.84, suggesting an accumulation of labile DOC over DO depletion. This is further supported by the bacteria community composition that showed an increase in anaerobic metabolism families when DO <6.29 mg/L. Laboratory incubation revealed strong labile DOC release (∼ 243 ± 38 μmol/L) from particulate organic carbon (POC) over oxygen depletion, followed by significant DOC loss in either anoxic-oxic or oxic-oxic groups. The degraded original DOC was slightly less in the oxygen depletion-treated group compared to the oxic group, and the resistant proportion was estimated as 1% ∼ 8% after 1–14 days of anoxic treatments. The resistant DOC accumulation after DO alleviation for 30 days was much less in amount when compared to the big release of labile DOC over DO depletion (48 vs. 243 μmol/L) and we believed that the lack of observed resistant DOC accumulation in the field observation was due to the overlap of multiple anoxic-oxic cycling processes and the masking effect of newly labile DOC released from the POC.

Mitigation of hypoxia and ocean acidification on the inner East China Sea shelf impacted by the 2023 summer drought

Hypoxia and acidification are universal environmental issues in coastal seas, especially in large river dominated shelves, and the East China Sea shelf is a typical case among them. However, the responses of status of hypoxia and acidification in coastal seas to the extremes of river discharges are still to be revealed. This study surveyed the influences of a summer drought on the status of hypoxia and acidification on the inner East China Sea shelf off the Changjiang estuary. In August of 2023 during a summer drought, carbonate system parameters and dissolved oxygen (DO) were surveyed on the East China Sea shelf off the Changjiang estuary. As expected, dissolved inorganic carbon (DIC) removal (up to >40 μmol kg−1) and DO over-saturation (up to >110 %) accompanied by high pH (up to >8.15) in the surface water were observed. However, low DO (32–172 μmol kg−1), low pH (7.63–8.04) and low saturation state index of aragonite (ΩAr) (1.34–3.06) in the bottom water were observed. Relationships of Excess DIC with DO consumption, and pH and ΩAr with Excess DIC indicated that the hypoxia and acidification in the bottom water was due mainly to the remineralization of the marine-sourced organic matter. Nevertheless, both hypoxia and acidification were mitigated, i.e. the hypoxic area was smaller, the minimum DO concentration, pH and saturation state index of aragonite were higher in August of 2023 than under the general summer condition. The lower Changjiang discharge (∼60 % of the long-term monthly average) mitigated eutrophication of the East China Sea shelf and decreased the phytoplankton biomass in the surface water and subsequently the hypoxia and acidification in the bottom water. However, acidification of the bottom water on the East China Sea shelf was still severe even during the summer drought. Regulating the anthropogenic impact on the coastal marginal seas is still urgently needed to mitigate the acidification status.

Peteryoungia algae sp. nov. isolated from seaweeds of Gouqi Island, China, and its unique genetic features among Peteryoungia strains.

A Gram-stain-negative, light khaki, strictly aerobic, rod-shaped, motile via multiple flagella, and catalase- and oxidase-positive bacterium, designated as SSM4.3T, was isolated from the seaweed of Gouqi Island in the East China Sea. The novel isolate grows at 0-5.0% NaCl concentrations (w/v) (optimum 1%), pH 5.0-9.0 (optimum pH 7.0), and 15-37°C (optimum 30°C). The 16S rRNA gene sequences-based phylogeny indicates that the novel marine isolate belongs to the family Rhizobiaceae and that it shared the greatest sequence similarity (98.9%) with Peteryoungia rhizophila CGMCC 1.15691T. This classification was also supported by phylogenetic analysis using core genes. The predominant fatty acids (≥ 10%) of the strain were identified as C18:1 ω7c/C18:1 ω6c. Q-10 was identified as the major isoprenoid quinone, with trace levels of Q-9 present. The major polar lipids were identified as diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. The complete genome size of strain SSM4.3T is 4.39Mb with a DNA G+C content of 61.3%. The average nucleotide identity, digital DNA-DNA hybridization, and average amino acid identity values between the genomes of strain SSM4.3T and its closely related representatives were 74.80-86.93%, 20.00-32.30%, and 70.30-91.52%, respectively. Phylogenetic analysis, grounded on the core genes, reveals the evolutionary relationship between SSM4.3T and other Peteryoungia strains. Pan-genomics analysis of 8 previously classified Peteryoungia species and SSM4.3T revealed their unique genetic features and functions. Overall, strain SSM4.3T was considered to be a new species of the Peteryoungia genus; the name Peteryoungia algae sp. nov. has been proposed, with type strain SSM4.3T (= LMG 32561 = MCCC 1K07170).

A Three–Year Comparison of Fluctuations in the Occurrence of the Giant Jellyfish (Nemopilema nomurai)

In this study, acoustic, sighting, trawl, and marine environmental surveys were used to determine the vertical distribution and density of giant jellyfish that have been observed in Korean waters over the past 3 years. From 2020 to 2022, annual surveys were conducted in May and July in the East China Sea and waters adjacent to South Korea. The acoustic data were processed by identifying and eliminating all signals considered as noise while excluding those suspected to be jellyfish signals. Subsequently, a single target detection method was employed. Giant jellyfish are distributed mostly in the middle and low layers. In May 2021, the average population density of giant jellyfish was recorded as 11.6 (ind./ha), which was the highest density. In July 2022, this value decreased to 1.7 (ind./ha), marking the lowest density. The sighting survey, which allows for the identification of jellyfish distributed in the surface layer, exhibited a difference of approximately 0.13 times compared to the acoustic survey conducted in the middle and low layers in 2020. In 2021 and 2022, this difference was approximately 0.11 times and 0.24 times, respectively. The average of this difference was 0.16 times or greater.

OSL and radiocarbon dating of core TBF-1 on the outer shelf of the East China Sea and implications for late Quaternary stratigraphic correlation

It is crucial to establish a robust chronology for understanding late Quaternary sedimentation processes and environment changes in response to sea-level fluctuation on shelves. The shelf of the East China Sea (ECS) is featured by huge terrigenous sediment input and striking land -sea interaction during the late Quaternary. However, there remains controversy in chronostratigraphic rebuilding of transgression and regression deposits during eustatic-glacial cycles, mainly due to a lack of reliable dating data. In this study, an extensive comparison of 17 optically stimulated luminescence (OSL) and 15 AMS 14C ages from core TBF-1 (upper 40 m) provides a constraint in chronostratigraphic reconstruction since Marine Isotope Stage (MIS) 5. OSL ages range from 9.5 ± 0.7 to 67.3 ± 4.8 ka at depths from 2.00 to 28.00 m, while 14C ages range from 6645 to 41435 cal a BP at depths from 0.02 to 17.52 m. Regression analysis demonstrates a high level of agreement between OSL and 14C ages, with r2 values of 0.91 and 0.90, respectively. For Holocene sediments (U1), both OSL and 14C methods are applicable in tidal sand ridges, however, it should be noted that 14C ages may exhibit a young bias of up to 3 ka. For pre-Holocene sediments (U6-U2), OSL ages are robust within saturation limitation of OSL signal (De up to ca. 166 Gy), cross-checked by feldspar post-IR IRSL (pIRIR) dating protocol. Nevertheless, the shell 14C ages (11620 and 10390 cal a BP at depths of 13.95–14.56 m) in Last Glacial Maximum (LGM) fluvial sediments of U2 are significantly underestimated, because of their susceptibility to recrystallization and overgrowth, resulting in carbon exchange with environment. While the peaty layer's14C age in deltaic deposition (17.50 m, U5) was determined to be 36420 cal a BP, coincided with OSL age of 39.6 ± 3.9 ka. The chronostratigraphy since MIS 5 for core TBF-1 exhibits a significant correlation with previously published cores SFK-1, DZQ4, and DH02, on the ECS outer shelf. Through the evaluation of those underestimated 14C ages and saturated OSL ages, we re-elucidated the primary sedimentary facies and their respective formation periods. This sedimentary stratigraphic illustration exhibits significant consistency with eustatic-glacial cycles. The renewed chronological framework for ECS shelf allows better correlation between the late Quaternary sedimentary evolution and the land-sea interaction on open shelves dominated by siliciclastic sedimentation.

Integrated multi-omics analyses reveal microbial community resilience to fluctuating low oxygen in the East China sea

Climate change and eutrophication are accelerating ocean deoxygenation, leading to a global decline in oxygen levels. The East China Sea, frequently experiencing deoxygenation events, harbors diverse microbial communities. However, the response of these communities to the changing deoxygenation dynamics remains poorly understood. Here, we explored the composition and function of microbial communities inhabiting seawaters of the Changjiang Estuary and offshore areas. Our findings suggested that neutral processes significantly influenced the assembly of these communities. The overall bacterial composition demonstrated remarkable high stability across the oxygen gradient. Salinity exhibited a significantly stronger correlation with bacterial community structure than dissolved oxygen. Both metagenomics and metaproteomics revealed that all of the samples exhibited similar functional community structures. Heterotrophic metabolism dominated these sites, as evidenced by a diverse array of transporters and metabolic enzymes for organic matter uptake and utilization, which constituted a significant portion of the expressed proteins. O2 was the primary electron acceptor in bacteria even under hypoxic conditions, evidenced by expression of low- and high-affinity cytochrome oxidases. Proteins associated with anaerobic processes, such as dissimilatory sulfite reductases, were virtually undetectable. Untargeted liquid chromatography with tandem mass spectrometry analysis of seawater samples revealed a diverse range of dissolved organic matter (DOM) components in amino acids, lipids, organic acids, peptides, and carbohydrates, potentially fueling dominant taxa growth. Despite fluctuations in the abundance of specific genera, the remarkable similarity in community structure, function, and DOM suggests that this ecosystem possesses robust adaptive mechanisms that buffer against abrupt changes, even below the well-defined hypoxic threshold in marine ecosystem.