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Background: Uroteuthis edulis is a significant economic cephalopod resource utilized by mainland China, Taiwan, and Japan. Understanding the population genetic structure of U.edulis is essential to evaluate the changes of its resource abundance. In this study, we used the COI gene as a marker to evaluate the population structure of U.edulis. Methods and results: Molecular marker analysis indicated that the sampled individuals were categorized into three populations (ES1, ES2, and ES3). All populations exhibited high haplotype diversity indices (Hd) and low nucleotide diversity indices (Pi), with the ES2 population showing the lowest Hd and Pi values. Analysis of molecular variance (AMOVA) revealed that genetic variation among populations accounted for 89.06% of the total variation. The phylogenetic tree illustrated distinct lineage clustering, with each population forming a separate clade. Combined with the biological information, it was observed that the majority of female individuals were larger in size and exhibited high sexual maturity. Male individuals displayed notable differences across populations: ES1 individuals were primarily small to medium-sized with low sexual maturity, ES2 individuals were mainly medium-sized with a relatively even distribution of sexual maturity, and ES3 individuals were predominantly large-sized with high sexual maturity. Conclusions: The findings indicate substantial genetic differentiation and ecological variation among U.edulis. populations. Strengthen monitoring of population resources and genetic diversity, long-term tracking of changes, and the timely formulation of scientifically sound conservation and management measures to ensure the sustainable development in future. [ABSTRACT FROM AUTHOR]

Simple Summary: Ecosystem processes and energy flow drive marine food web dynamics with primary food sources, trophic interactions, and functional groups are crucial for stability. In continental shelf ecosystems, seasonal benthic–pelagic coupling influences food webs and fisheries, but research on shelf fish responses to environmental shifts is limited. The Southern Sea of Korea (SSK), influenced by the Tsushima Warm Current (TWC) and Changjiang River Diluted Water (CDW), faces rapid warming and seasonal changes that affect productivity and trophic dynamics. Using carbon (δ13C) and nitrogen (δ15N) stable isotopes, we examined fish trophic structures, revealing distinct seasonal food web patterns. During stratified conditions, reduced benthic–pelagic coupling shifts TWC fish to more pelagic prey, with some species showing lower trophic positions. Benthic fish rely on detrital sources, while pelagic fish are more influenced by pelagic production, especially in spring. Seasonal isotopic shifts reflect changes in pelagic and benthic pathways, with a stronger pelagic influence in spring and reduced resources in summer. Higher productivity in the CDW region leads to more pronounced variations in pelagic consumers, while benthic consumers in TWC regions remain stable. These findings emphasize the need for monitoring warming and TWC influence, which could shift food webs toward greater benthic dependence, impacting fisheries. In seasonally stratified marine environments, the dynamics of benthic–pelagic coupling plays a crucial role in shaping food web structures and fisheries production. We examined fish food web structures across three distinct shelf areas in the Southern Sea of Korea (SSK) during both stratified (summer) and mixed (spring) water conditions using stable isotopes of carbon (δ13C) and nitrogen (δ15N). In spring, fish communities exhibited a broader range of δ13C values compared with summer, indicating more diverse feeding strategies. Seasonal variations in the proportion of benthic and pelagic prey in consumer diets highlighted shifts in benthic–pelagic coupling, illustrating how consumers adjust their reliance on benthic or pelagic resources. The relative importance of the benthic pathway varied among species groups throughout the year. During stratified conditions, reduced benthic–pelagic coupling led to increased reliance on benthic prey, particularly in the oligotrophic region influenced by the Tsushima Warm Current (TWC). The food web spanned five trophic levels, with a median of 3.6. Several species, notably benthic ones, declined in their trophic positions during the summer stratification. These results suggest that fish food webs in the SSK are shaped by temperature-driven seasonal bottom-up control. Our findings further offer insights into how increased water-column stratification could impact the trophic niches of shelf-food webs in the TWC region. [ABSTRACT FROM AUTHOR]

The El Niño‐Southern Oscillation (ENSO)‐related interannual variability of the Kuroshio in the East China Sea (ECS) was revisited based on reanalysis outputs during 1993–2018. Unlike the synchronized variations from 2006 to 2018, the period of 1993–2005 showed regional differences in how the ECS‐Kuroshio responded to ENSO events. Specifically, from the upstream region to the midway of the continental slope, the ECS‐Kuroshio exhibited distinct six‐year interannual modulation during 1993–2005. In contrast, downstream Kuroshio variability primarily followed a four‐year cycle, aligning with ENSO variability during the same period. Further analysis suggested that the sea surface height anomaly (SSHA) east of the Kerama Gap, near the midpoint of the Ryukyu Island chain, extended inside the ECS until the southern side of the Tokara Strait along the ECS‐Kuroshio path and was well correlated with the Kuroshio in the Tokara Strait during 1993–2005. The cause of this SSHA signal was attributed to forcing by ENSO‐related wind stress curl changes in the interior region. There was an obvious difference in the ENSO‐related atmospheric circulation before and after 2005. The wind stress curl pattern in the North Pacific during 1993–2005, characterized by a maximum in the Kerama Gap latitude band, shifted northward compared to that during 2006–2018. The relative northward shift of the ENSO‐related wind stress curl, which stimulates the long baroclinic Rossby wave propagating westward and arriving east of the Kerama Gap, affect the interannual variabilities of both the upstream and downstream Kuroshio. Plain Language Summary: The Kuroshio is the western boundary current of the North Pacific Ocean. It plays a significant role in the marine ecosystem and the global heat budget of the East China Sea (ECS). This study revealed that the responses of the Kuroshio in the ECS to the El Niño‐Southern Oscillation (ENSO) show distinctive regional differences from upstream to downstream region during 1993–2005, which is different from the synchronized response during 2006–2018. The sea surface height anomaly (SSHA) east of the Kerama Gap, which is forced by ENSO‐related wind stress curl changes in the North Pacific, could extend inside the ECS until the Tokara Strait along the ECS‐Kuroshio path and is well correlated with the Kuroshio in the Tokara Strait before 2005. Key Points: Upstream and downstream ECS‐Kuroshio exhibited inconsistent (consistent) responses to the ENSO variation before (and after) 2005Variation of the Kuroshio in the Tokara Strait is related to the SSHA east of the Kerama Gap, which may be attributed to the El Niño state before 2005The ENSO‐related wind stress pattern shifted northward during 1993–2005 compared with that during 2006–2018 [ABSTRACT FROM AUTHOR]

Aerosol deposition is one of the major processes providing bioavailable Fe to the surface ocean. However, the quantification of aerosol Fe flux in the surface ocean is highly challenging operationally. In this study, we measured both Fe isotopic composition and specific elemental ratios in 5 size‐fraction aerosols collected over the East China Sea (ECS) to quantify the relative contribution of lithogenic and anthropogenic aerosol Fe. Both the isotopic and elemental ratios indicate that anthropogenic aerosol Fe mainly originates from high‐temperature combustion activities with the end member of the δ56Fe to be −4.5‰. We found that the Cd/Ti ratio is a much more reliable proxy to quantify the contribution of anthropogenic aerosol Fe in coarse aerosols than δ56Fe in the ECS. Attributed to extremely high deposition velocities and high total Fe concentrations for large size aerosols, lithogenic aerosols are still the dominant dissolved aerosol Fe source in the ECS. Plain Language Summary: The supply of iron to the surface oceans is a crucial factor deciding primary production and carbon cycling in the ocean. Traditionally, it was thought that natural dust was the primary contributor of both total and soluble aerosol iron to the surface oceans. However, some studies suggest that human‐made aerosols could also play a significant role in supplying soluble Fe to surface waters. Yet, accurately estimating the flux of either natural or human‐made aerosol Fe to the ocean surface is complex and challenging. During the winter and spring monsoon seasons, the East China Sea (ECS) receives substantial amounts of both natural and human‐made aerosols from East Asia and serves as an ideal location to study the fluxes of natural and anthropogenic aerosol Fe. In this study, we used Fe isotopic analysis and elemental ratios of some specific elements in the ECS aerosols to estimate the relative contributions of anthropogenic and natural aerosol Fe. We found that in spite of the high anthropogenic aerosol input, natural dust remains the predominant supplier of soluble Fe to the surface waters in the ECS. Key Points: Anthropogenic aerosol Fe collected in the East China Sea mainly originates from high‐temperature coal combustion of East AsiaCd to Ti ratio is a reliable proxy to quantify the contribution of total anthropogenic Fe in the coarse aerosolsLithogenic aerosol Fe is still the dominant source of aerosol dissolved Fe in the surface water of the East China Sea [ABSTRACT FROM AUTHOR]

The largehead hairtail (Trichiurus japonicus) is the most productive fish caught in China. In order to understand the seasonal distribution of T. japonicus in the East China Sea and the central and southern parts of the Yellow Sea, three species distribution models were used in this study, namely the random-forest model, K-nearest-neighbor algorithm, and gradient-ascending decision-tree model, based on the data of trawling surveys in the East China Sea and central and southern parts of the Yellow Sea from 2008 to 2009. Combined with a variance inflation factor and cross-check, a distribution model of T. japonicus was screened and constructed to analyze the influence of environmental factors on the distribution of T. japonicus in the East China Sea and central and southern parts of the Yellow Sea. The results showed that the random-forest model had the advantages of fitting effect and prediction ability among the three models. The analysis of this model showed that the water depth, bottom water temperature, and surface salinity had a great influence on the habitat distribution of T. japonicus. The relative resources of T. japonicus increased with the increase of bottom water temperature, reached the maximum at 23.8 °C, and first increased and then decreased with the increase of water depth and surface salinity, reaching the maximum when water depth is 72 m and surface salinity is 31.2%. This study also used the random-forest model to predict the spatial distribution of T. japonicus in the central and southern waters of the East China Sea and south-central Yellow Sea from 2008 to 2009, and the results showed that the predicted results were close to the actual situation. The research results can provide a reference for the exploitation and protection of T. japonicus resources in the East China Sea and the south-central Yellow Sea. [ABSTRACT FROM AUTHOR]

The Dʺ layer, defined as 200–400 km in the lowermost mantle, is a thermal and chemical boundary layer between the solid silicate mantle and the liquid outer core. Deciphering the detailed structures of the Dʺ region is essential for unlocking the thermal and chemical states in the deep Earth. Here, we precisely measure the slowness and back‐azimuth of the direct P‐waves by beamforming based on the F‐trace stack at the KZ Array in Kazakhstan, to investigate the detailed Dʺ structures beneath the East China Sea. The P‐wave slowness for rays turning beneath the East China Sea exhibits a significant anomaly as a function of the P‐wave turning depth. Strong correlations between slowness and back‐azimuth anomalies for rays from different directions suggest a tilted Moho, with a tilting direction of ∼103° and a dip angle of ∼15°, beneath the KZ Array, further supported by radial receiver functions. After correcting for the slowness anomalies caused by the tilted Moho and heterogeneities outside the Dʺ layer, we construct a series of Vp Dʺ models to fit the remaining slowness anomalies for rays sampling the East China Sea. We obtain the best Dʺ model with a height of 360 km, a maximum δVp of +1.4%, a Dʺ discontinuity thickness of 120 km, and an 80‐km low‐velocity layer at the base of the mantle by minimizing residuals between the predicted and observed slowness anomalies. Combining the sharpness of the Dʺ discontinuity imaged here with mineralogical analysis suggests a Fe‐enriched region in a cold subduction environment beneath the East China Sea. Plain Language Summary: The Dʺ region, defined as several hundreds of kilometers in the lowermost mantle, contains multi‐scale heterogeneities. Constraining the detailed Dʺ structures is key to estimating the thermal and chemical states in the deep Earth. Using recorded P waveform data at the KZ Array in Kazakhstan, we measure the two parameters (slowness and back‐azimuth) that describe the propagation direction of the incident wavefield, to explore the detailed Dʺ structures beneath the East China Sea. Strong correlations between anomalies of these two parameters for rays from different directions reveal a tilted Moho (an interface separating crust and mantle) beneath the KZ Array with a tilting direction of ∼103° and a dip angle of ∼15°. The attitude of this tilted Moho is further supported by results from another seismic data called receiver functions. After correcting the anomalies introduced by the tilted Moho and heterogeneities outside the Dʺ region, we build a series of P‐wave velocity Dʺ models to fit the remaining anomalies and obtain the best Dʺ model beneath the East China Sea. Accordingly, we estimate the thermal and chemical states in our study region by combining the seismological observations and mineralogical analysis. Key Points: Analysis of P‐wave slowness and back‐azimuth anomalies reveals a tilted Moho beneath the KZ Array and detailed Dʺ structures beneath the East China SeaThe Dʺ model approximately has a height of 360 km, a maximum δVp of +1.4%, and an 80‐km low‐velocity layer at the base of the mantleEnriched Fe in a cold environment can explain the observed seismic signatures of Dʺ structures [ABSTRACT FROM AUTHOR]

Biodiversity serves as the foundation for human survival and development. Marine fishes play a crucial role in supporting both global biodiversity and food sources. The conventional methods for fish diversity and fishery resources survey are inadequate to meet the growing demand for large-scale and long-period surveys. The eDNA metabarcoding approach provides an effective and non-invasive monitoring revolution, and has been applied to identify fish diversities. This study conducted a comprehensive comparison of fish diversity in the East China Sea on a large scale both horizontally and vertically. The results showed a total of 81 fish species, which were classified into 20 orders, 44 families and 72 genera. Although no statistically significant difference in fish diversity was found amongst the horizontal groups (east-middle-west, south-middle-north, and shallow-middle-deep) and the various sampling layers (surface-middle-bottom), discernible trends were obtained in this study. Fish diversity results revealed the orders of east > middle > west, middle > north > south and deep > shallow > middle in horizontal groups. Additionally, surface water exhibited a higher level of fish diversity than other water layers. Some fish species were only detected at specific vertical depths. The diverse composition of fish species across different water layers can be attributed to their distinct ecological types. The overall findings suggest that an increase of sampling stations and mixed samples should be collected in deeper water bodies for comprehensive understanding of fish diversity. This study can also provide the fundamental data and experimental design reference for future studies and fishery management. [ABSTRACT FROM AUTHOR]

Acanthocephalans in the polymorphid genus Bolbosoma Porta, 1908 utilize marine mammals and seabirds as the definitive host, and marine fish as the paratenic host. As in many other groups of acanthocephalans, morphology-based species identification at the cystacanth stage of Bolbosoma is challenging; at present, DNA barcoding is the most reliable approach for larval identification. However, sequence data currently available for Bolbosoma are scarce. In this study, we report the morphology and DNA sequence information (cytochrome c oxidase subunit I and 18S rRNA genes) of Bolbosoma cystacanths from six marine fish species collected in Japan.

Particle scattering is a key factor affecting underwater light transport. The diffusion length (zD), defined as 1/[b(1 - g)], where b is the scattering coefficient and g is the asymmetry factor, is obtained from the volume scattering function (VSF) of the particle and plays a vital role in assessing the potential for underwater optical detection, imaging and communication. Owing to the lack of VSF datasets, the variation in zD at different wavelengths in various ocean areas remains unclear. In this study, we used a dual-wavelength (488 & 532 nm) VSFLab to conduct the VSF measurement experiments in the East China Sea (ECS) and the South China Sea (SCS), obtaining VSFs from 1.5° to 178.5° at 51 stations. Seven optical properties, including absorption (a), scattering (b), attenuation (c), diffuse attenuation coefficient (Kd), backscattering (bb), g, and zD, were calculated from the measured VSFs. A comparative analysis of the results was performed, which showed that the laser transmission capability at 532 nm was better than that at 488 nm in terms of the absorption or diffuse attenuation coefficient in the ECS, whereas superior performance was observed at 488 nm in the SCS. However, from the perspective of scattering, zD at 532 nm (zD(532)) demonstrated superior performance in both the ECS and SCS. This superiority was particularly noticeable in regions with exceptionally clear water, such as the eastern side of the Luzon Strait, where zD(532) exceeded zD(488) by approximately 20%. Overall, the findings of this study provide a new perspective for assessing underwater light transmission capabilities. [ABSTRACT FROM AUTHOR]

How does China signal foreign policy intentions to domestic and international audiences during territorial conflicts? While China can signal its resolve by provoking nationalism at home, doing so may risk appearing threatening to neighbouring countries in the region. We argue that China resolves the dilemma by sending different types of messages to domestic and international audiences. Focusing on China's maritime conflicts in the South China Sea and the East China Sea, we examine China's narratives regarding the maritime disputes through the analysis of state-run media. Our findings from text mining and topic analyses of more than 31,000 state media reports from 2002 to 2021 suggest that China signals to the international audience on international cooperation emphasising diplomatic and peaceful resolutions while relatively less so in domestic media. The analyses have implications for how China signals foreign policy intentions amidst rising nationalism. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Observations 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. Plain Language Summary: The Okinawa Trough (OT) is a key link between the Pacific Ocean and the East China Sea (ECS) continental shelf. It was observed by previous studies that persistent southwestward slope countercurrents (SCCs) exist beneath the northeastward Kuroshio Current at several locations over the ECS continental slope. These countercurrents have been attributed to a variety of mechanisms based on analyses and interpretations of observations made at different locations. It is yet not clear whether these flows are localized circulation features or segments of an OT‐wide circulation system. In this study, we find that there indeed exists a trough‐scale SCC along the ECS slope that is associated with an anti‐clockwise circulation. Analyses indicate the OT experiences different vertical volume exchanges at the deep layer, which induces lateral exchanges of potential vorticity (a dynamically conserved quantity in an ideal and rotating fluid) and eventually drives the SCC. Numerical experiments are performed to show the validity of this process. The SCC may be of vital importance in transporting heat and nutrients and regulating the sediment distributions in the OT. This mechanism is potentially applicable to explain the undercurrent in similar semi‐enclosed marginal seas. Key Points: Over the entire East China Sea continental slope, the slope countercurrent beneath the surface Kuroshio Current is potentially continuousThe slope countercurrent is the western part of a deep cyclonic circulation in the Okinawa TroughThe upwelling divergence along the East China Sea continental slope is the main forcing mechanism of the slope countercurrent [ABSTRACT FROM AUTHOR]

Simple Summary: This study examines the spatial distribution patterns of key fishery resources in the East China Sea across four seasons. Utilizing a habitat suitability index model, we identified the primary environmental factors influencing these patterns. Our results indicate that water temperature is a crucial factor for hairtail, while salinity and water depth are significant for small yellow croaker and Bombay duck, respectively. We also assessed the ecological niche overlap among different species and seasons, finding that predator-prey interactions primarily drive spatial habitat overlap. During summer and autumn, multiple species show increased overlap due to synchronized life cycles. An overlap index analysis demonstrated that species overlap rises from spring to winter, peaking in winter due to overwintering behavior and reduced food competition. These findings provide insights into species interactions and inform effective fishery resource management. 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. [ABSTRACT FROM AUTHOR]

To test the potential of high‐resolution satellite image analysis for assessing and predicting the mesoscale (<10 km in this study) effects of climate and environmental change on temperature and primary productivity in fishing grounds, we conducted satellite image analysis around an island in a coastal strait west of Japan from 2018 to 2023. We observed a distinct north–south gradient in sea surface temperature (SST) and chlorophyll a concentration (CHL) over approximately 20 km of the transect, which was likely affected by the current system. The model configuration suggests that the frequency of southward currents during winter–spring can control the magnitude of spring phytoplankton blooms. In the study region, an increase in SST at a rate of 0.06–0.13°C y−1 occurred during the study period, accompanied by a decrease in CHL. The north–south gradient in the rate of change suggests that the variation in the temperature and flow rate of the Kuroshio Current into the study area was due to these abrupt changes. The relationship between the annual mean SST and CHL was also spatially heterogeneous, showing a higher sensitivity of CHL to SST in the southwest of the island than in the north. In addition to the intrusion of warm and oligotrophic Kuroshio waters, the spread of less saline and more eutrophic coastal waters likely influenced this spatial heterogeneity. The satellite image analysis in the present study successfully revealed mesoscale mosaics of environmental conditions in coastal fishery grounds. [ABSTRACT FROM AUTHOR]

This article analyzes ECS maritime disputes through two lenses: as a globally comparable case study mediated through LOS and as a distinct regional case that differs in several respects from disputes outside East Asia. This study focuses on the Senkaku/Diaoyu island dispute but also examines broader EEZ and ADIZ disputes between China, Japan, and South Korea and the Ieodo dispute between China and South Korea. It finds that global dynamics are applicable to the ECS disputes, as countries depend on LOS rules even while attempting to interpret them for unilateral advantage whenever possible, and parties avoid formal arbitration, when possible, in favor of bilateral agreements. However, regional factors impact these dynamics. The sudden and sometimes violent transition from the Sino-Centric tributary system to the Westphalian system has undermined the legitimacy of LOS and western international law regionally. Finally, the presence of China as a party to almost all ECS disputes limits the application of LOS because China's position as a near-peer competitor with the US gives it additional options to unilaterally impose its will. Unlike relatively weaker parties to these disputes, China may be less concerned about flouting LOS that it does not see as necessary for protecting its maritime claims. [ABSTRACT FROM AUTHOR]

A comprehensive analysis was carried out to investigate the driving factors and influencing mechanisms of spatiotemporal variation of sea level at multiple scales in the East China Sea (ECS) via satellite altimetry datasets from 1993 to 2020. Based on the altimetry grid data processed by the local mean decomposition method, the spatiotemporal changes of ECS sea level are analyzed from the multi-scale perspective in terms of multi-year, seasonal, interannual, and multi-modal scales. The results revealed that the ECS regional mean sea level change rate is 3.41 ± 0.58 mm/year over the 28-year period. On the seasonal scale, the regional mean sea level change rates are 3.45 ± 0.66 mm/year, 3.35 ± 0.60 mm/year, 3.39 ± 0.71 mm/year, and 3.57 ± 0.75 mm/year, for the four seasons (i.e., spring, summer, autumn, and winter) respectively. The spatial distribution analysis showed that ECS sea level changes are most pronounced in coastal areas. The northeast sea area of Taiwan and the edge of the East China Sea shelf are important areas of mesoscale eddy activity, which have an important impact on regional sea level change. The ECS seasonal sea level change is mainly affected by monsoons, precipitation, and temperature changes. The spatial distribution analysis indicated that the impact factors, including seawater thermal expansion, monsoons, ENSO, and the Kuroshio Current, dominated the ECS seasonal sea level change. Additionally, the ENSO and Kuroshio Current collectively affect the spatial distribution characteristics. Additionally, the empirical orthogonal function was employed to analyze the three modes of ECS regional sea level change, with the first three modes contributing 26.37%, 12.32%, and 10.47%, respectively. Spatially, the first mode mainly corresponds to ENSO index, whereas the second and third modes are linked to seasonal factors, and exhibit antiphase effects. The analyzed correlations between the ECS sea level change and southern oscillation index (SOI), revealed the consistent spatial characteristics between the regions affected by ENSO and those by the Kuroshio Current. [ABSTRACT FROM AUTHOR]

The East China Sea (ECS) is one of the region's most significant and oft-times under-addressed potential flashpoints. In this article we take a holistic approach and reexamine the recent actions of East Asia's two most significant powers, China and Japan, in relation to this important body of maritime space, as well as those of the United States (US), as the incumbent regional hegemon. Specifically, we examine the efficacy of each. This highlights a dynamism in Chinese actions, as well as elucidating how the US and Japan have come to adopt policies that are of dubious efficacy as a means of alleviating or nullifying the escalation of unwanted tensions across the ECS. In so doing, we draw upon two key concepts, immobilism and confirmation bias, that help us to understand why the US and Japan are failing to achieve their assumed objectives of regional stability and the maintenance of the status quo. Ultimately, we argue that a combination of immobilism and confirmation bias in American and Japanese foreign policy, in response to the greater dynamism and adaptability of regional great powers such as China, has led to latent changes in the status quo that risk undermining stability across the ECS. [ABSTRACT FROM AUTHOR]

Context: Climate change reportedly affects global fisheries, including the highly valuable swimming crabs, an important benthic species in Asian waters. Aims: The aim of this study was to determine the effects of El Niño–Southern Oscillation (ENSO) events on catch rates and habitat suitability of Portunus pelagicus , Portunus sanguinolentus and Charybdis feriatus in the Taiwan Strait. Methods: We combined marine remote sensing data with Taiwanese trap vessel data to develop a weighted habitat suitability index modelling and analyse the recruitment dynamics of swimming crabs in different ENSO events. Key results: Our results suggest that Increasing salinity (>33.5 PSU) and sea temperature (>18.6°C) during La Niña events had a positive effect on stock recruitment and habitat suitability index of P. pelagicus and C. feriatus. By contrast, P. sanguinolentus were not affected by ENSO events. The low catch rates for P. sanguinolentus in normal years and for C. feriatus and P. pelagicus in normal and El Niño years were highly consistent with the significant shrinkage of the habitat suitability index. Conclusions: Monitoring climate change and environmental factors is essential for understanding their effects on marine ecosystems. Implications: This research can help implement sustainable crab fisheries. Climate change affects marine environments, disrupting fisheries and ecosystems. Marine crustaceans, like swimming crabs in the Taiwan Strait, respond by altering catchability and habitat suitability. El Niño events significantly affect their fishing grounds, whereas water exchange and wind changes influence temperature, salinity and water mass structure. During La Niña years, positive ocean temperature and salinity anomalies may further affect the optimal habitats and catchability of swimming crabs. [ABSTRACT FROM AUTHOR]

Variable fluorescence measurements provide automatic and rapid estimates of electron-based photosynthesis. However, electron transport rates (ETR) to phytoplankton production vary greatly due to biological physiology and environmental stress along the Changjiang River to the adjacent seawater, where the turbid riverside, nutrient-rich river plume, and seawater are divided by the sediment front and plume front. We assessed the light responses of ETR, 18O-labeled gross primary production (GPP), and O2-based net community production (NCP) during the bloom season at the Changjiang River Estuary. The distribution of phytoplankton and potential photosynthesis efficiency were positively correlated, exhibiting offshore decreasing trends and peaking around the upwelling areas. The conversion factors of ΦGPP (mol e- per mol O2 production) ranged from 0.8 to 31.8, and ΦNCP ranged from 0.9 to 36.9, respectively. Φe: O increased from the nutrient-rich Changjiang diluted water (CDW) to the nutrient-poor seawater. Although ΦGPP and ΦNCP were linearly related to non-photochemical quenching (R² > 0.5) in the CDW, this relationship was decoupled in offshore seawater due to P-limitation, light stress, and shifts in the phytoplankton community. A better relationship between ΦGPP and ΦNCP was quantified usingmultiple linear analyses with the light attenuation coefficient (Kd), euphotic depth (Zeu), salinity, nutrients, and temperature (p< 0.001). This improvement in accuracy represents a major step forward for widespread and accurate fluorometry-based GPP and NCP applications at high temporal and spatial resolutions in the future. [ABSTRACT FROM AUTHOR]

The East China Sea (ECS) is among the most important and highly dynamic shelf seas, where the coupling of physical and biogeochemical processes is distinctive and may play a crucial role in regulating nutrient conditions and the pattern of primary production. Based on field observations during the late summer of 2019, the physical controls of nutrient supply and the subsequent influences on phytoplankton chlorophyll‐a (Chl‐a) regime were investigated in the ECS. The coastal upwelling originating from the Kuroshio Subsurface Water (KSSW) intrusion serves as a nutrient source on the inner East China Sea (ECS) shelf, and this inshore upwelling combined with the coastal water largely governs the surface Chl‐a patterns. The halocline, thermocline and nutricline exhibit a vertically synchronous fluctuating phenomenon, and the coexistence of several subsurface cold rings/patches was significantly observed on the middle‐outer ECS shelf, indicating intense vertical advection and the occurrence of upwelling. The subsurface cold rings greatly regulate the vertical hydrodynamics, constituting unique upward pathways of the onshore intruded KSSW on the middle‐outer shelf. Nutrients can be upwelled within these cold rings to support primary production, thus partially leading to the spatial variability of subsurface Chl‐a maximum in terms of intensity and depth. Our findings would considerably contribute to our understanding of the physical‐biogeochemical‐ecological processes on the ECS shelf. Plain Language Summary: The East China Sea (ECS) is one of the most important continental shelves in the world. Exploring the physical‐biogeochemical processes is of great significance for the in‐depth understanding of ecosystem in this shelf sea. Here, specific attention was paid to the physical controls on the nutrient supply and the associated influences on phytoplankton chlorophyll‐a (Chl‐a) regime in the ECS. We show that the coastal/inshore upwelling originating from the nearshore branch of the Kuroshio Subsurface Water (KSSW) intrusion serves as a nutrient source on the inner ECS shelf. The co‐occurrence of several subsurface cold rings clearly indicates the upward transport of the onshore intruded KSSW on the middle‐outer ECS shelf. The subsurface cold rings may play a role in modulating the vertical hydrodynamics and related biogeochemical‐ecological processes, leading to the upward delivery of nutrients and enhanced Chl‐a levels. Our results would provide a sound scientific basis for the studies of biogeochemical and ecological dynamics in the ECS. Key Points: The coexistence of several subsurface cold rings indicating upwelling on the middle‐outer East China Sea shelf was observedSubsurface cold rings and coastal upwelling constituted unique upward pathways of the onshore intruded Kuroshio Subsurface WaterNutrients could be upwelled within the cold rings and potentially modulated the associated biogeochemical‐ecological processes [ABSTRACT FROM AUTHOR]

Carbon monoxide (CO) plays a vital role in the biochemical processes of marine microorganisms, climate regulation, and global carbon cycle. In this study, seasonal and spatial variations of CO and oceanographic factors influencing these variations were investigated in the East China Sea (ECS) during two cruises from 16 to 30 May 2020 and from 8 to 30 October 2021. ECS was as a net source of atmospheric CO in both spring and autumn. The average values of seawater CO concentrations ([CO]surf), atmospheric CO mixing ratio ([CO]atm) and sea‐to‐air flux of CO were 2.22 ± 0.47 nmol L−1 and 0.97 ± 0.86 nmol L−1, 182.8 ± 71.8 ppbv and 102.7 ± 38.8 ppbv, 96.14 ± 25.82 nmol m−2 hr−1 and 31.96 ± 35.61 nmol m−2 hr−1 in spring and autumn, respectively. A steady‐state model was used to estimate the biogeochemical cycling rates of [CO]atm over the ECS. The effect of CO sea‐to‐air fluxes on atmospheric ·OH concentration was likely decreased from spring to autumn. Photoirradiation experiments further showed that the actual contributions of ultraviolet radiation and photosynthetically active radiation to CO photoproduction in the surface waters were 72.2% ± 13.8% and 27.8% ± 13.8%, respectively. The sea‐to‐air fluxes of CO in autumn were 5.15 μmol m−2 day−1 lower than in spring, which were due to larger bacterial consumption and lower [CO]surf in autumn in the ECS. Further, this study is expected to improve our understanding of the biogeochemical processes of CO in the eastern marginal seas of China. Plain Language Summary: Over the past decade, there has been a significant increase in global carbon emissions. CO is a potent greenhouse gas, and chromophoric dissolved organic matter (CDOM) photochemical processes control CO emission from the ocean to the atmosphere. Coastal waters dominate global oceanic carbon emissions, but the dynamics, controls and roles of CO remain largely unconstrained in the marginal seas around China. Here, we conducted a variety of biogeochemical analyses to investigate the controls of CO dynamics cycling in the East China Sea during spring and autumn. [CO]surf, [CO]atm, and sea‐to‐air flux of CO showed significant seasonal variability between spring and autumn, with higher values observed in spring. A variety of environmental factors such as CDOM concentration, wind speed and direction, physical mixing, air‐sea exchange, bacterial consumption, and dark production could affect CO distribution. Compared to air‐sea exchange, bacterial consumption represented the main CO‐sink and contributed over 90% of the total CO loss. These results provide a supplement to the global database of CO cycling processes and improve our current understanding of CO seasonal distribution in coastal ecosystems. Key Points: [CO]surf, [CO]atm, and sea‐to‐air flux of CO in spring were significantly higher than in autumn in the East China SeaThe effect of CO sea‐to‐air fluxes on ·OH was decreased from spring to autumnDark production accounted for about 23% of the total CO production in autumn [ABSTRACT FROM AUTHOR]

The frequency of riverine floods is predicted to increase in East Asia. However, the response of coastal hypoxia (<63 μmol L−1) to floods has not been well understood. In the summer of 2020, characterized by one of the most significant Changjiang water fluxes in three decades, we conducted a cruise during the flood period on the East China Sea inner shelf. Our observations revealed severe bottom hypoxia with a maximum spatial coverage of ∼11,600 km2 and a minimum dissolved oxygen concentration (DO) of 21 μmol L−1. In the surface layer, the relationships between salinity and nitrate, dissolved inorganic carbon (DIC) indicated significant organic matter production, validated by a high‐Chlorophyll‐a (Chl a) patch (>5 μg L−1). Furthermore, the significant relationship between apparent oxygen utilization and DIC of deep waters reveals that the organic matter decomposition primarily drove the hypoxia during the flood period. Episodic wind events also influenced bottom DO and DIC, by transporting surface waters to the deep. Multiple‐years data set shows that the average Changjiang nitrate flux during flood years is about 1.4 times that during non‐flood years. The flood waters mix with estuarine waters, forming the high‐nutrient plume waters, which expanded farther offshore during the flood period. While high turbidity remained confined to the inner estuary. Consequently, the high‐Chl a area significantly expanded, which significantly exacerbated the hypoxia. Plain Language Summary: Coastal waters are severely threatened by hypoxia, which impacts the growth, reproduction, and migration of marine organisms. Nutrient inputs from river basins are one of the major controlling factors of hypoxia in coastal oceans. The frequency and intensity of floods in river basins are projected to increase in the context of global warming in East Asia. However, the relationship between floods and coastal hypoxia is not well documented. The year 2020 witnessed lots of riverine flood events across Asian countries, which provided us with an excellent opportunity to reveal the influences of flood on hypoxia development on the shelf. In 2020, the August nitrate flux of Changjiang was 1.5 times higher compared to that in non‐flood years. We observed maximum hypoxic waters covering 11,600 km2 with a minimum DO of 21 μmol L−1 on the East China Sea inner shelf. Historical data showed that the floods led to the expansion of the high‐nutrient plume area, resulting in high biological production in the plume, and a nearly doubling of the hypoxia extent in the bottom waters. With the growing risk of intensive floods, hypoxia is likely to aggravate in coastal waters. Key Points: We observed a maximum hypoxia area of ∼11,600 km2, and a minimum dissolved oxygen of 21 μmol L−1 during the flood period in 2020Significant nitrate removal and surface Chlorophyll a exceeding 29 μg L−1 suggested intense biological production during the flood periodThe expansion of high‐Chl a plume area during flood periods surpasses that of non‐flood periods, contributing to hypoxia area increase [ABSTRACT FROM AUTHOR]

This study investigated long-term interannual changes in summer circulation and hydrology in the East China Sea (ECS) by performing 35-year high-resolution ocean model simulation from 1981 to 2015. The sea surface temperature (SST) warming trend was considerably weaker in summer than in winter. To the east of the Yangtze Estuary, the interannual variation of SST in summer was mainly dominated by horizontal advection associated with variations in the Taiwan warm current and heat flux in the offshore region north of the Yangtze Estuary. Baroclinic circulation during summer played a crucial role in subsurface mixing. Near the surface, the significant atmospheric wind mode (EOF1) and Kuroshio mode (EOF2) dominate interannual variations in ocean circulation. In the subsurface, local wind around the Tsushima Strait dominated the interannual ocean variation. Anomalous northeasterly winds induced a southwestward pressure gradient due to topographical confinement. These anomalies propagated to the south along the continental shelf through topographic Rossby waves. This study identified two types of anomalous features based on combinations of surface and subsurface EOFs. The combination represents an in-phase contribution between wind and Kuroshio forcings and between the surface and subsurface circulation that enhances the hydrological variability in the ECS. The implication on the relevant biogeochemical and ecological studies in the East China Sea is also very crucial at the interannual time scale.

Life history characteristics of Watases lanternfish Diaphus watasei from a deep sea fishing ground of the East China Sea were studied. Overall, 452 adult individuals with standard length ranging from 91 to 147 mm were collected in the continental slope during 3 years. The growth pattern and hatching date were inferred from otolith microstructure analysis, and the stomach contents were examined to clarify feeding ecology. Three distinct zones of the otolith microstructure were depicted, the numbers of increments in the central and middle zones of the D. watasei otolith are in the lowest level in myctophid species studied. The maximum number of growth increments indicated a short lifespan of 2 years. The spawning time almost lasted throughout the year, and then two cohorts were separated according to the estimated hatching time. The length–weight relationship revealed a negative allometric pattern and significant difference between the two cohorts, and a significant seasonal difference was also detected in somatic growth pattern. A piscivorous habit dominated by Maurolicus muelleri was revealed across sampling seasons and standard length groups. Overall, D. watasei show distinct life history characteristics compared to coinhabiting myctophids, and such characteristics could reduce interspecific competition. [ABSTRACT FROM AUTHOR]

During the summer, substantial freshwater discharge from the Changjiang River into the East China Sea (ECS) results in extensive low-salinity water (LSW) plumes that significantly affect regions along the southern Korean Peninsula and near Jeju Island. Previous research developed an empirical equation to estimate sea surface salinity (SSS) in the ECS during the summer season using remote-sensing reflectance (Rrs) data from bands 3–6 (490, 555, 660, and 680 nm) of the Geostationary Ocean Color Imager (GOCI). With the conclusion of the GOCI mission in March 2021, this study aims to ensure the continuity of SSS estimation in the ECS by transitioning to its successor, the GOCI-II. This transition was facilitated through two approaches: applying the existing GOCI-based equation and introducing a new machine learning method using a random forest model. Our analysis demonstrated a high correlation between SSS estimates derived from the GOCI and GOCI-II when applying the equation developed for the GOCI to both satellites, as indicated by a robust R2 value of 0.984 and a low RMSD of 0.8465 psu. This study successfully addressed the challenge of maintaining continuous SSS estimation in the ECS post-GOCI mission and evaluated the accuracy and limitations of the GOCI-II-derived SSS, proposing future strategies to enhance its effectiveness. [ABSTRACT FROM AUTHOR]

The Pollution Nagasaki (PN) section of the East China Sea (ECS) is a typical area for studying the complex hydrographic dynamics between Changjiang River discharge and Kuroshio, displaying intense variations of environmental gradients from nearshore to offshore. However, the temporal and spatial changes of microbial communities along the PN section have long been overlooked. In this study, we performed a comprehensive investigation into the abundance, diversity and ecology of free-living (FL) and particle-associated (PA) microbial communities in seawater samples along the PN section during both summer and winter. Distinct hydrological conditions and resulting environmental gradients were observed between summer and winter, with clear features of intrusive Kuroshio subsurface water in summer and strong vertical mixing of seawater in winter. Bacterial abundance along the PN section was higher in summer (1.11  ×  108 copies·L−1 – 7.37  ×  108 copies·L−1) than in winter (1.83  ×  106 copies·L−1 – 1.34  ×  108 copies·L−1). Microbial diversity, as indicated by α-diversity indices, remained at relatively stable levels in summer, while a clear decreasing trend was observed in winter along the PN section. Additionally, the winter communities exhibited a more evident spatial shift along the PN section compared to the summer communities. 16S rRNA gene amplicon sequencing showed that microbial community composition varied considerably between different seasons (summer and winter) and lifestyles (FL and PA), with a notable dominance of Ralstonia species. in winter. Regarding the assembly of microbial communities, the stochastic process represented by dispersal limitation was the dominant process in summer, while the deterministic homogeneous selection was the most important process in winter. Correspondingly, distinct topological properties of the microbial co-occurrence networks were shown between different seasons and along the PN section. These results enhance our understanding of how hydrological conditions influence dynamic changes of microbial communities along the PN section, providing new insights for the microbial community assembly and interactions in such a complex environment. [ABSTRACT FROM AUTHOR]

Shelf seas are experiencing a rise in shallow gas leaks, primarily methane, raising concerns due to their environmental impact. However, the effect of the leaks on early diagenesis remains poorly understood. This study analyzes sediment lithology, organic geochemistry and porewater geochemistry of two short cores collected nearby the pockmarks in the muddy inner shelf of the East China Sea. Our findings clearly demonstrate the impact of methane leakage on early diagenesis, evidenced by the shallower position of the SMTZ (sulfate-methane transition zone), higher concentrations of uranium (U), vanadium (V), and manganese (Mn) in the porewater near and above the SMTZ, and downcore decrease in Mg2+, Ca2+, and Sr2+ concentrations versus increase in Mg2+/Ca2+ and Sr2+/Ca2+ ratios. Their profile variations and the difference between two cores are determined by the intensity of methane leakage. The estimated methane diffusive flux of 619 mmol m-2 yr-1 at YEC7-2 is roughly 8.5 times that at YEC7-1 (73 mmol m-2 yr-1), consistent with a shorter distance of YEC7-2 to the pockmark with active methane leakage. A schematic model is summarized to demonstrate the response of early diagenesis processes to the increasing methane leakages in response to changing sedimentation regimes from accretion to severe erosion. This study undoubtedly improves our understanding mutual promotion effect between seafloor erosion and gas leakage, and their impact on early diagenesis processes and resultant porewater geochemical changes and authigenic mineral records. [ABSTRACT FROM AUTHOR]

Atmospheric forcings are significant physical factors that influence the variation of sea surface temperature (SST) and are often used as essential input variables for ocean numerical models. However, their contribution to the prediction of SST based on machine-learning methods still needs to be tested. This study presents a prediction model for SST in the East China Sea (ECS) using two machine-learning methods: Random Forest and SA-ConvLSTM algorithms. According to the Random Forest feature importance scores and correlation coefficients R, 2 m air temperature and longwave radiation were selected as the two most important key atmospheric factors that can affect the SST prediction performance of machine-learning methods. Four datasets were constructed as input to SA-ConvLSTM: SST-only, SST-T2m, SST-LWR, and SST-T2m-LWR. Using the SST-T2m and SST-LWR, the prediction skill of the model can be improved by about 9.9% and 9.43% for the RMSE and by about 8.97% and 8.21% for the MAE, respectively. Using the SST-T2m-LWR dataset, the model's prediction skill can be improved by 10.75% for RMSE and 9.06% for MAE. The SA-ConvLSTM can represent the SST in ECS well, but with the highest RMSE and AE in summer. The findings of the presented study requires much more exploration in future studies. [ABSTRACT FROM AUTHOR]

The nutrients from the East China Sea (ECS) through the Tsushima/Korea Strait (TS) strongly impact the ecosystem of the Japan Sea (JS). The complex origins of the Tsushima Warm Current and the various nutrient sources in the ECS result in complex spatial-temporal variations in nutrients in the TS. Using a physical-biological model with a tracking technique, we studied the effects of nutrient sources from the ECS on the TS. Among all the nutrient sources, the Kuroshio has the highest nutrient concentrations in the TS. Its maximum concentration occurs at the bottom, while those of rivers and atmospheric deposition occur at the surface, and that of the Taiwan Strait occurs in the middle layer. The nutrient transport through the TS exhibits similar seasonal variations, as does the volume transport. The transport of nutrients from the Kuroshio accounts for more than 85% of the total. The transport of nutrients from the Taiwan Strait is greater during autumn and winter. The transport of dissolved inorganic nitrogen (DIN) from both rivers and atmospheric deposition through the TS peak in August. Nutrient transport cannot be equated with volume transport. The DIN in the less saline zone originates not only from rivers but also from atmospheric deposition and the Kuroshio. The transport of nutrients from the Taiwan Strait is not as significant as its volume transport in the TS. [ABSTRACT FROM AUTHOR]

Off the east shore of China, thermal front plays a crucial role in modulating coastal biogeochemical environment. Based on multi‐source observational and reanalysis products, decadal variation and regulatory mechanism of Zhejiang‐Fujian coastal front (ZFCF) were investigated. The intensity of ZFCF showed a two‐stage inversed varying trend over past four decades: a downtrend from 1982 to 2002 followed by an uptrend from 2002 to 2022. During 1982–2002, sea surface temperature (SST) experienced more pronounced warming in inshore areas than offshore due to weakening of the southward coastal current, and this primarily led to the downtrend of ZFCF. Within 2002–2022, opposite SST trends were observed on two sides of ZFCF, that is, the ZFCF kept intensifying due to the cooperation of cooling inshore and warming offshore. The enhanced coastal current driven by stronger monsoon and increased Yangtze River discharge cooled the inshore area, then the cooling was further facilitated by intensified heat loss in the upper layer of the plume. Meanwhile, the onshore shift of Kuroshio led to strengthened intrusion of warm water into the East China Sea, heating the offshore side of ZFCF and thus intensifying the front. Plain Language Summary: Oceanic fronts delineate the boundaries of different water masses and, in coastal regions, front zones are closely associated with biological habitats and hydrodynamics. Located along the East China Sea (ECS), the Zhejiang‐Fujian coastal front (ZFCF) is a region of high biological production, and the famous Zhoushan fishing ground is in that front zone. In this study, we found the ZFCF showed significant decadal variations based on 40 years of satellite observations of sea surface temperature: the intensity of ZFCF exhibits a negative trend during 1982–2002 and a positive trend during 2002–2022. These processes were primarily driven by the combined effects of the terrigenous runoff, coastal current and the Kuroshio Current, with the latter two factors closely related to the variabilities of local winds. The current study provides critical insights into the long‐term change of the ZFCF and we aim to better understand the coastal environments in the ECS. Key Points: Zhejiang‐Fujian coastal thermal front kept weakening within 1982–2002 while intensifying during 2002–2022Weakened coastal current dominated the downtrend of front intensity in the context of global warmingEnhanced coastal current and increased runoff together with stronger westward intrusion of Kuroshio governed the uptrend of front intensity [ABSTRACT FROM AUTHOR]

Swordtip squid (Uroteuthis edulis) is characterized by a complex population structure and rapid generation renewal and sensitive to habitat changes. Its population growth response to environmental variations implies its flexible life history traits. In this study, with the samples collected in the north‐central waters of the East China Sea from 2017 to 2021, the daily growth of the spring stock was analyzed based on the age and increment width of statolith. The gradient forest method (GFM) and generalized additive mixed models (GAMMs) were used to explore the changes in the weights of environmental variables and the relationships between daily growth and environmental variables in various growth stages. The age of the samples collected from 2017 to 2021 mainly ranged from 180 to 240 days, and the spring stock was the dominant stock. According to the distance from daily increment to core in the statolith, the life history of the spring stock was divided into four growth stages (S1 embryo–larval stage, S2 juvenile stage, S3 subadult stage, and S4 adult stage). For the spring stock, the cumulative weight of temperature and salinity in the population growth was the largest in S1 stage; the cumulative weight of temperature and velocity was the largest in S2 stage; the cumulative weight of temperature was the largest in S3 stage; and the cumulative weight of mixed layer depth (MLD), temperature, and salinity was the largest in S4 stage. The relationship between temperature at the depth of 25 m (T25) and daily growth of the spring stock was first positively correlated (S1–S2), then negatively correlated (S3), and finally positively correlated (S4). The relationship between environment variable and growth of the spring stock gradually decreased with the increase in MLD (30 to 50 m) and SSS (S3–S4, 32.2‰ to 33.2‰) and gradually increased with the increase in the velocity of currents (S1,.1 to.2 m/s). The differences in the responses of the spring stock to environmental variations in different growth stages may lead to the changes in the growth traits for the spring stock. This study provides a scientific basis for a comprehensive understanding of the life history traits of U. edulis. [ABSTRACT FROM AUTHOR]

Sulfate-reducing Bacteria (SRB) corrosion is a serious threat to the safety of marine pipelines.To reveal the influence of the corrosion behavior of X60 pipeline steel in the presence of SRB cultured in seawater and mud from the East China Sea The corrosion behavior of X60 pipeline steel was studied with weight loss measurements, microstructure and membrane composition analysis, electrochemical measurements The corrosion rate in sterile seawater is 0.11 mm/y, whereas, in SRB-infested seawater, it increases by 245 % to 0.38 mm/y. In sterile sea mud, the corrosion rate is 0.15 mm/y, but in SRB-infested sea mud, it increases by 87 % to 0.28 mm/y. In the corrosive environment of seawater and mud in the East China Sea, SRB significantly accelerates the microbial corrosion of X60 pipeline steel. These findings provide theoretical guidance for further research on SRB corrosion mechanisms and corrosion control of marine pipelines.

AbstractWe report the complete mitochondrial genome of Rhynchocinetes brucei Okuno 1994. The mitogenome was found to contain 16158 bp with 13 protein-coding genes (PCGs), 22 tRNA genes (tRNAs), 2 rRNA genes (rRNAs), and 1 putative control region. Phylogenetic analysis indicated that R. brucei was sister to Rhynchocinetes durbanensis (PP= 1), of the same family Rhynchocinetidae. These results are helpful for research on the phylogenetic and evolutionary studies of this group.

An unidentified colonial ascidian called gaikotsu-panda-hoya in Japanese, literally meaning ‘skeleton panda ascidian,’ has been attracting SCUBA divers’ attention for the past few years since its strange appearance was introduced on the Internet by a diving shop in Kumejima Island, Japan. To confirm the taxonomic status of this species, fresh samples were collected from a diving point off the coast of Kumejima Island. Our morphological examination revealed that they represent a new species, herein described as Clavelina ossipandae sp. nov., which can be distinguished from 44 congeners in the genus Clavelina Savigny, 1816 by the combination of the following seven characteristics: i) colony consisting of completely free zooids, ii) zooids up to 20 mm in length, iii) in the living state, zooids transparent, with laterally elongated white patch between oral and atrial siphons, as well as four black markings, one between siphons, one mid-dorsally, and the other two situated laterally in a pair on the anterior part of the body, iv) transverse vessels white, v) endostyle black, vi) 10–14 stigmatal rows, and vii) two longitudinal muscular bands running from the abdomen to the endostyle on each side. Partial sequences (810 bp) of the cytochrome c oxidase subunit I gene from the holotype and one of the paratypes differed at 10 sites from each other (1.26% K2P distance) but were the same when translated into amino acids. A phylogenetic tree supported that this species is included in the genus Clavelina.

Using 2‐year platform observations, this study investigates seasonal characteristics of sea land breeze (SLB) and how it influences air‐sea turbulent heat fluxes (THFs) in the coastal areas of East China Sea (ECS) in different seasons. Unlike other SLB studies, this study uses hourly observation on a sea platform to explore SLB's effect on both air‐sea latent heat and sensible heat transferring. The results show that sea wind (SW) does not have an obvious seasonal variation pattern while land wind (LW) is stronger in autumn and winter. The SLB day number shows a clear seasonal variation pattern, which accounts for 38.04% and 18.23% of summertime and wintertime days, reaching its peak and bottom respectively. The latent heat flux (LHF) and sensible heat flux (SHF) are high in autumn and winter while low in summer. The SLB‐contributed LHF and SHF reach peaks in autumn and winter, which are 61.07 and 7.39 W/m2 respectively. The contribution importance of SLB on air‐sea sensible/latent heat transferring is highest in summer while lowest in winter. On SLB days, the SHF decreases significantly by at least about 50% while LHF decreases moderately in all seasons, among which spring witnesses an inversion of sensible heat transferring direction. The warming effect of SLB is mainly responsible for the slump of SHF on SLB days. Multiple factors including relative humidity (RH), background wind field and in situ radiation cause the LHF decrease together, whose changing range varies with season. Plain Language Summary: Sea land breeze (SLB) has a great impact on regional environment and meteorological fields. Turbulent heat flux (THF), including sensible heat flux (SHF) and latent heat flux (LHF), is fundamentally engaged in nearly every atmosphere‐ocean interaction process and undoubtedly serve as an important driving force of global atmospheric and oceanic circulation as well as a sensitive variable when facing global climate change. However, there are few studies relating SLB to the variation of THF in the near coastal region, which is a sensitive‐area to climatic changes under the effects of both natural and human variabilities. In this study, instead of using land‐based data like other SLB studies, we investigate SLB's effects on air‐sea THFs in different seasons based on sea‐based data. We find that SLB's role in transferring air‐sea energy in form of THF is most important in summer among all seasons. The SHF decreases significantly while LHF decreases moderately on SLB days in all four seasons. The warming effect of SLB is mainly responsible for the slump of SHF on SLB days, while the external factors such as background wind field, relative humidity, and in situ radiation are responsible for the LHF decrease on SLB days. Key Points: The peak SLB‐contributed LHF and SHF are 61.1 W/m2 in autumn and 7.4 W/m2 in winter, respectivelyThe SHF decreases significantly while LHF decreases moderately on SLB days in four seasonsThe warming effect of SLB is mainly responsible for the slump of SHF on SLB days [ABSTRACT FROM AUTHOR]