Southern East China Sea Research Articles

Effect of a tropical cyclone on the pelagic ecosystem of a continental shelf

AbstractThis study aimed to comprehend the effects of Typhoon Maria on the pelagic ecosystem in the southern East China Sea. Shipboard measurements were conducted at eight sampling stations before (2–4 d) and after (3–6 d) the typhoon, which enabled the evaluation of the potential impacts of the typhoon on this pelagic ecosystem, with particular focus on carbon dynamics. Following the typhoon's passage, there was a slight drop in sea surface temperature. The response of the variables to the typhoon, however, exhibited variations at different sampling stations. For further analysis, t‐tests compared variables, while type II regression assessed the linear correlation between two variables. Overall, during the post‐typhoon period, concentrations of nitrate, chlorophyll a, primary production, bacterial biomass and production, plankton community respiration, and abundance of large phytoplankton (> 2 μm) and the relative abundance of picophytoplankton among larger‐sized picoeukaryotes were higher compared to the pre‐typhoon period. The mean value of fugacity of CO2 was similar to or slightly lower than pre‐typhoon period. Although the typhoon‐induced vigorous primary production might have absorbed a significant amount of CO2, the decrease in fugacity of CO2 could have been offset by the plankton community respiration. The findings suggest that the typhoon enhanced physical disturbance and increased water column mixing, which, in turn, augmented nutrient availability and promoted plankton growth in the shallow water column. Overall, this study sheds light on the complex interactions between typhoons and marine ecosystems and highlights the importance of further investigating these phenomena to better understand their ecological implications.

Integrated Genetic and Statolith Shape Analysis Reveals the Population Structure of Loliolus (Nipponololigo) uyii (Cephalopoda: Loliginidae) in the Coastal Waters of China

Understanding population structure is a priority for evaluating population dynamics of commercially fished cephalopods under fishing pressure and environmental changes. This study employed a multidisciplinary approach to clarify the population structure of Loliolus (Nipponololigo) uyii, a common squid in inshore fisheries. Sampling was conducted multiple times to cover the distribution range across the East China Sea and South China Sea. High haplotype diversity was revealed by three gene markers (COI, 16S and ODH). Two geographical clades with significant genetic differentiation were divided through phylogenetic trees and haplotype networks. The boundary between the two clades is delineated by the Dongshan population in the southern East China Sea. Furthermore, the neutrality tests and mismatch analysis suggested that L. (N.) uyii populations may have undergone population expansion. Correspondingly, statolith differences in lateral dome and posterior indentation, along with high classification success, further supported the genetic division. The overall difference in statolith shape also efficiently identified seasonal groups in the Beibu Gulf lacking genetic differentiation. This result offers new insights into the influence of genetic and environmental factors on statolith shape. The integrated results provide a comprehensive understanding of the population structure of L. (N.) uyii, laying the foundation for resource development and the conservation of the species.

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

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

Otolith elemental composition indicates differences in the habitat use for larvae and early juveniles of Japanese jack mackerel (Trachurus japonicus) in the waters around Japan

AbstractTrace element analysis of otoliths from core to edge was used to reveal differences in habitats of larvae and early juveniles of Japanese jack mackerel (Trachurus japonicus) caught in the East China Sea (ECS), Pacific Ocean, and Sea of Japan. Multi‐element signatures (Sr:Ca, Mg:Ca, Na:Ca, K:Ca, and Ba:Ca) were analyzed with multivariate statistics to determine whether these element signatures provide insight into regional population structure. The median values of elements: Ca ratios in otolith core region differed significantly among areas, with most elements between the ECS and the Pacific Ocean or Sea of Japan showing significant differences. The Sr:Ca ratios exhibited a V‐shaped trend from the otolith core to the edge, which was likely related to the vertical habitat layer shift of larvae and early juveniles of T. japonicus. Canonical analysis of principal coordinates using the element: Ca ratios and the hatching day were re‐classified according to the sampling area with higher accuracy in the ECS (88–95%) and the Sea of Japan (76–83%) compared to the Pacific Ocean (69–72%). These results indicate that the proportion of eggs, larvae, and early juveniles transported by the Kuroshio Current from the southern ECS—the main spawning ground—to the Pacific Ocean or the Sea of Japan is low and that juveniles distributed in the coastal waters off southwestern Japan may have originated from local spawners. These results suggest that determining the elemental composition of larvae and juveniles of T. japonicus is effective in determining the habitat differences of this species in the three regions. These findings will help to understand population structure and recruitment process of this species around Japan.

Riverine Influences and Seasonal Dynamics: Exploring Carbonate System Variations and Air‐Sea CO2 Fluxes in the Southern Yellow Sea and East China Sea

AbstractIn this work, the seasonal variations of the carbonate system and air‐sea CO2 fluxes were investigated by two cruises in the southern Yellow Sea (SYS) and the East China Sea (ECS), which were significantly influenced by the Changjiang riverine inputs across seasons. Biological‐mediated change of dissolved inorganic carbon (DIC) was first quantitated through a three end‐member mixing model from winter to spring. Our modeling results suggested that DIC addition through biological remineralization persisted in the SYS during winter and spring, while DIC removal was evident in the Changjiang River Plume and the offshore ECS triggered by river inputs in spring. Horizontal and vertical mixing together constituted the largest contribution to the interseasonal variability of partial pressure of CO2 (pCO2) in the SYS (−69.5%), the river plume (−59.3%), and the ECS offshore (−43.8%), followed by temperature effects in the plume area (29.4%), and biological processes in the ECS offshore (24.1%) and the SYS (−7.7%), with air‐sea CO2 exchange contributing the least in both three subregions. The SYS, the river plume, and the ECS offshore all acted as atmospheric CO2 sinks in both winter and spring. Furthermore, their ability to absorb atmospheric CO2 increased from winter to spring, as reflected in a ∼1.8‐fold increase in the overall spring air‐sea CO2 flux compared to winter estimation.

Long-term trends and extreme events of marine heatwaves in the Eastern China Marginal Seas during summer

Marine heatwaves (MHWs) are a type of widespread, persistent, and extreme marine warming event that can cause serious harm to the global marine ecology and economy. This study provides a systematic analysis of the long-term trends of MHWs in the Eastern China Marginal Seas (ECMS) during summer spanning from 1982 to 2022, and occurrence mechanisms of extreme MHW events. The findings show that in the context of global warming, the frequency of summer MHWs in the ECMS has increased across most regions, with a higher rate along the coast of China. Areas exhibiting a rapid surge in duration predominantly reside in the southern Yellow Sea (SYS) and southern East China Sea (ECS, south of 28°N). In contrast, the long-term trends of mean and maximum intensities exhibit both increases and decreases: Rising trends primarily occur in the Bohai Sea (BS) and Yellow Sea (YS), whereas descending trends are detected in the northern ECS (north of 28°N). Influenced jointly by duration and mean intensity, cumulative intensity (CumInt) exhibits a notable positive growth off the Yangtze River Estuary, in the SYS and southern ECS. By employing the empirical orthogonal function, the spatio-temporal features of the first two modes of CumInt and their correlation with summer mean sea surface temperature (SST) and SST variance are further examined. The first mode of CumInt displays a positive anomalous pattern throughout the ECMS, with notable upward trend in the corresponding time series, and the rising trend is primarily influenced by summer mean SST warming. Moreover, both of the first two modes show notable interannual variability. Extreme MHW events in the SYS in 2016 and 2018 are examined using the mixed layer temperature equation. The results suggest that these extreme MHW events originate primarily from anomalous atmospheric forcing and oceanic vertical mixing. These processes involve an anomalous high-pressure system over the SYS splitting from the western Pacific subtropical high, augmented atmospheric stability, diminished wind speeds, intensified solar radiation, and reduced oceanic mixing, thereby leading to the accumulation of more heat near the sea surface and forming extreme MHW events.

The Northeast Mindoro block is the conjugate margin of the southern East China Sea Basin: Insight from detrital zircon data

There is a hot debate over whether the initial opening of the South China Sea (SCS) took place in continental crust or oceanic crust. In this study, we present new detrital zircon U–Pb ages from late Eocene sedimentary rocks in the East China Sea Basin (ECSB). Our results reveal a broad U–Pb age spectrum with a substantial proportion of grains dating >1500 Ma. Notably, the provenance characteristics of the late Eocene ECSB are markedly distinct from other regions along the South China margin, as evidenced by kernel density estimation, nonmetric multidimensional scaling, and cumulative age distribution plots. The ECSB shared nearly identical provenance features with the northeast Mindoro block on the southern SCS margin during the late Eocene. Considering the previously proposed widespread breakup unconformity across the southern ECSB and the slab-based plate reconstruction from tomography of the SCS, we propose that northern Mindoro was the conjugate margin of the southern ECSB and underwent southward drifting during the SCS opening. This study provides a new plate reconstruction model of the SCS and evidence supporting the contention that the initial breakup of the SCS occurred within the continental crust.

Assessing inorganic nitrogen transport in marine phytoplankton assemblages through the 15N-tracer technique and metatranscriptomics

The availability of inorganic nitrogen is considered one of the limiting factors for primary production in the ocean. However, different phytoplankton possess unique strategies to take up and assimilate nitrate and ammonium to cope with environmental changes. To investigate the nitrogen uptake characteristics of different size-fractionated phytoplankton in natural assemblages, 3 research cruises were conducted in the southern East China Sea in 2018 and 2019. The nitrogen uptake characteristics of 2 size-fractionated natural assemblages, microphytoplankton (20-200 µm) and pico-nanophytoplankton (<20 µm), were measured using the 15N-tracer technique. At most of the stations, significantly higher potential maximum uptake rates of ammonium than of nitrate were detected in the pico-nanophytoplankton, indicating that small phytoplankton possess a relatively superior capacity to take up ammonium. By contrast, comparing the potential maximum uptake rate for nitrate between microphytoplankton and pico-nanophytoplankton showed that microphytoplankton exhibit a higher capacity for nitrate uptake as a nitrogen source compared to pico-nanophytoplankton. However, repressed uptake rates of ammonium and nitrate in microphytoplankton were sometimes found at the coastal station even when ambient nitrate concentrations remained high. Metatranscriptomic analysis of nitrogen transporter genes in microphytoplankton suggests that most diatoms utilize regenerated ammonium before nitrate to maintain their populations at the end of blooms. Metatranscriptomic approaches identify the transcriptional responses of dominant diatoms to explain how diatoms regulate their nitrogen transporter genes to cope with environmental changes in natural assemblages.

Neogene morphotectonic evolution of the East Asian Continental Shelf

The offshore basins in the East Asian Continental Shelf have undergone distinct tectono-geomorphic-sedimentary evolution since the Neogene, driven by complex interactions between tectonic and surface Earth processes. However, the contribution of the latter to the evolution of the offshore basins has been less studied. The landscape simulation software Badlands serves as an ideal tool to investigate the impacts of tectonic and surface processes on sedimentation as it simulates the sediment routing in a source-to-sink context. Focusing on the southern East China Sea Basin (ECSB) and the northern South China Sea Shelf Basin (SCSSB), two key components of the East Asian Continental Shelf, we used Badlands to reconstruct the tectono-geomorphic-sedimentary evolution since the Neogene. It revealed two-phase evolutionary processes: (1) the southern ECSB and the northern SCSSB were in the unified shelf environment and represented as an integral during the Early Miocene, though the northern SCSSB experienced anomalous subsidence due to the southward jump of the SCS mid-ocean ridge. The integrated southern ECSB and northern SCSSB experienced uplift and denudation since the Middle Miocene, under the influence of the Philippine Sea Plate extrusion. (2) Subsequently, the southern ECSB and the northern SCSSB were separated into two independent basins in the Late Miocene, when Taiwan Island was significantly uplifted due to the Philippine Sea Plate extrusion and the arc-continental collision. Then Taiwan Island experienced a multi-stage uplift characterized by southward and westward migration. It concluded that tectonics (i.e. Taiwan Orogeny and the subduction of the Philippine Sea Plate) primarily dominated the differential evolution of the southern ECSB and the northern SCSSB. Surface Earth processes (i.e. the intensification of the East Asian Monsoon and the sea-level fluctuation) are the secondary contributors.

Sea-level changes control coastal organic carbon burial in the southern East China Sea during the late MIS 3

Sea-level changes control coastal organic carbon burial in the southern East China Sea during the late MIS 3

Effects of spatial–temporal conditions and fishing-vessel capacity on the capture of swimming crabs by using different fishing gear around the waters of Taiwan

Context Swimming crab is a vital fishery resource and a valuable source of income in the southern East China Sea, but it lacks management strategies, especially when using different fishing gear. Aims This study aimed to determine the effects of spatial–temporal conditions and vessel capacity on swimming crabs by using different fishing-gear types in the Taiwan Strait (TS). Methods We used generalised linear mixed models (GLMMs) to investigate data from Taiwanese vessels (2011–2019) on how spatial–temporal conditions and vessel capacity affected the catch of swimming crabs when using trawls, gill-nets and traps. Key results The results showed that the traps (>80.0%) caught more swimming crabs in the TS than did the gill-nets (6.6%) and trawls (8.0%). Additionally, the GLMM analysis showed that Charybdis feriatus, Portunus pelagicus and Portunus sanguinolentus catches by traps and trawls were significantly affected by different fishing locations, climate events, work hours and vessel sizes. However, for gill-nets, spatial–temporal conditions and vessel capacity did not affect the catch of C. feriatus. Conclusions Monitoring fishing efforts and environmental factors is vital to understanding their impacts on marine ecosystems. Implications These findings enable future sustainable crab fishing through harvesting strategy planning, ecosystem management and spatial–temporal governance.

Marine ecological effect of typhoon influenced by the frequency-phases of ENSO and anthropogenic activity: the East China Sea example

In coastal regions, typhoons are one of the most frequent natural disasters, and instrumental data indicate that they can greatly boost marine primary productivity. Typhoons' long-term ecological repercussions, however, are still little understood. To investigate the ecological effects of typhoons since the mid-Holocene, we focused on the sediment cores in the East China Sea, with key parameters of organic CN and Bio-Si to reveal the paleo-productivity variation. Over a millennium, the occurrence of El Niño-Southern Oscillation (ENSO) has had a substantial impact on primary productivity in the southern East China Sea. The primary productivity in the southern East China Sea was risen by humid climate conditions in ∼3.0–2.0 ka and frequent typhoons in 1.5–0 ka. With a millennial period, ENSO frequency has been significantly influencing primary productivity in the southern East China Sea since the mid-Holocene. During 1.5–0 ka, frequent ENSO events have led to more frequent typhoons, which caused terrestrial materials input and water vertically mix in the southern East China Sea, ultimately increasing primary productivity. Particularly on a centennial time scale, ENSO phases determined how much primary productivity was increased, and this magnitude was bigger during the La Niña-like periods than it was during the El Niño-like periods since La Niña is when typhoons occur more frequently. During the Little Ice Age, the cold climate hindered the reproduction of phytoplankton, but increased human activities in Taiwan resulted in more soil erosion and the supply of terrestrial-derived nutrients into the sea, then amplified the typhoon-induced increase in primary productivity. As a result, this stage showed the highest primary productivity since the mid-Holocene. This study reveals that frequent typhoons promote marine primary productivity on centennial-millennial timescales and emphasizes that human activities amplify the ecological effect of typhoons in recent centuries.

Differences in the diversity and community structure of the intestinal microbiota of commercial fishes in the central and southern East China Sea in spring and autumn

Differences in the diversity and community structure of the intestinal microbiota of commercial fishes in the central and southern East China Sea in spring and autumn

Rapidly Changing East Asian Marine Heatwaves Under a Warming Climate

AbstractThe East Asian marginal seas (EAMS) are one of the fastest‐warming ocean regions globally. This study presents the long‐term trends (1982–2020) of extreme ocean warming events called “marine heatwaves” over the EAMS and examines the relationships between marine heatwave trends and mean SST warming trends. We focus on five subregions with different influences from atmospheric perturbation and ocean currents: the northern East Sea (N‐ES), southern East Sea, Yellow Sea, Korea Strait (KS), and East China Sea (ECS). During the past four decades, marine heatwave duration and intensity in the EAMS have increased to approximately +4 days and +0.3°C per decade on average, respectively. In summer, the positive trend of marine heatwaves is the highest in the ECS, primarily due to the rapidly increasing mean sea surface temperature (SST). In winter, the N‐ES reveals remarkably rapid increases in marine heatwave properties in the last two decades, with increasing rates of approximately 6.2 (4.9) times longer total duration (stronger intensity) than the global average changes. Beyond the impact of the rapid increase in mean SST, the N‐ES marine heatwaves can be further extended due to the northward shift of the East Korea Warm Current. In general, mean SST changes are critical to the increasing trend in marine heatwave duration and intensity. This study further emphasizes that the changes in ocean circulation may expedite more rapid changes in extreme ocean events, which can produce more vulnerability in some places, such as the N‐ES, to marine heatwaves under continued global warming.

Shrimp community structure and influence of environmental variables in the East China Sea and Yellow Sea in spring.

Based on data collected from research vessel cruises performed in May 2020 off the East China Sea (ECS) and the southern Yellow Sea (YS) (26°30'-35°00' N, 120°30'-127°00' E), we analyzed the shrimp community and its relationships with environmental variables by using index of relative importance, biodiversity indices, and multivariate techniques. A total of 29 species were recorded, belonging to 11 families and 19 genera. The dominant species were Metapenaeopsis longirostris, Leptochela gracilis, Solenocera melantho, Crangon hakodatei, Parapenaeus fissuroides, Plesionika izumiae, and Trachypenaeus curvirostris, which together accounted for 82.9% of the total biomass and 90.8% of the total abundance of shrimps. Results of Cluster and NMDS analyses showed that three groups were identified for the shrimp community in the ECS and YS in spring, including group A (inshore of northern ECS and YS group), group B (offshore of northern ECS group) and group C (southern ECS group). ANOSIM and SIMPER analysis showed significant differences between group A and B, gourp A and C, and group B and C, with the dissimilarity of 92.2%, 95.8% and 91.6%, respectively. The typical species were T. curvirostris, C. hakodatei, L. gracilis and Palaemon gravieri in group A, and S. melantho in group B, and M. longirostris, P. fissuroides, P. izumiae and Solenocera alticarinata in group C. Significant differences were also detected in biomass, diversity index, species richness index and evenness index among groups, with significantly greater values in group C than those in A and B. Environmental variables and the substrate also displayed significant differences among groups. Results of canonical correspondence analysis showed that bottom temperature, bottom salinity, depth, and the substrate were the main environmental variables affecting spatial structure of shrimp community. Water mass characteristics and substrate type had important influences on the distribution of shrimp community in the ECS and YS in spring.

The Cretaceous Sedimentary Environments and Tectonic Setting of the Southern East China Sea Shelf Basin

Although the amount of oil and gas reserves and the reservoir properties in the East China Sea Shelf Basin (ECSSB) indicate good prospects for oil and gas exploration in the Mesozoic strata, there has not yet been a significant breakthrough in oil and gas production. An important reason is that there are few detailed studies on the sedimentary paleogeography of the ECSSB which make it difficult to predict the distribution of sand bodies. In this paper, well-core observations, thin-section identifications, electron probe microanalysis, trace elements analysis and seismic interpretations were synthetically applied to study the sedimentary environments and the tectonic setting of the Upper Cretaceous in the southern ECSSB. In the Oujiang Sag, red mudstones and pyroclastic rocks were deposited, accompanied by wedged, chaotic pro-grading reflections in the seismic profile, indicating a volcano-alluvial fan sedimentary system. Abundant sedimentary structures including double-mud drapes, asymmetric herringbone cross-beddings and burrows, such as Planolites and Skolithos, were developed in the Minjiang Sag, typically indicating a high-energy tidal environment. The autogenetic glauconites in situ and the fossil Tintinnid also indicate a shallow marine environment. The resulting sedimentary characteristics are in accordance with the littoral facies revealed by the seismic reflections in the Minjiang Sag. Moreover, volcanic conduit facies, effusive facies, and pyroclastic facies were also recognized in the seismic profile in the Minjiang Sag. Therefore, it was presumed that subaqueous volcanic eruptions occurred in the Minjiang Sag. In the Keelung Sag, the littoral facies were dominant. The tectonic setting of the Upper Cretaceous in the southern ECSSB is the transitional arc accompanied by large-scale volcanic activities. In conclusion, the volcano-alluvial fan sedimentary system was developed in the Oujiang Sag and volcano-littoral sedimentary system was developed from the Minjiang Sag to the Keelung Sag. This study is intended to promote the understanding of the sedimentary paleogeography of the Upper Cretaceous in the southern ECSSB and to provide help in oil and gas exploration.

Decadal Shift in Summer Precipitation Variability over East Asia in the Mid-2000s and Wave Propagation toward North America

Abstract The East Asian summer climate displays a marked change after the late 1990s. This is principally due to a weakening of the Pacific–Japan (PJ) teleconnection pattern that was a dominant driver of precipitation variability over East Asia. Nevertheless, western Japan has frequently experienced heavy rainfall events over the past several years. Atmospheric reanalysis and observational datasets are used to investigate summer precipitation variability over East Asia in a view of interdecadal changes from 1979 to 2020. East Asian summer precipitation has increased the most in Japan, especially over and around the Southwest Islands in southern Japan, where cumulus convection has been more dominant for the characteristic of precipitation variability including mei-yu–baiu rainfall than frontal structure since the mid-2000s. Atmospheric analysis in vertical structures and convective instability indicates that moist instability is neutralized by cumulus convection over the southern East China Sea and off the Pacific coast of Japan, where recent warming in sea surface temperature (SST) along the Kuroshio exceeds the SST threshold for convection. This decadal shift in precipitation variability has a close relationship with the second precipitation mode over East Asia, which has taken the place of the PJ pattern as a leading driver of precipitation variability over western Japan in the past decade. The enhanced cumulus convection is enabled to act as a forcing mechanism for the Rossby wave train from East Asia toward North America along the westerly jet or for the eastward extension of the Silk Road pattern, which possibly favors a heatwave in the Pacific Northwest areas of North America.

Isotopic Evidence of Population Connectivity at Multiple Life Stages for Larimichthys polyactis in the Southern Yellow Sea and East China Sea

Larimichthys polyactis, a typically oceanodromous species found across the East China, Yellow, and Bohai Seas, is one of the most ecologically and commercially important species in East Asian countries. Moreover, over the past decades, L. polyactis has experienced significant changes in its biological characteristics under long-term intensive fishing pressure, suggesting a need for urgent protection. A robust understanding of connectivity at the spatiotemporal scale is critical for the effective and thorough management of L. polyactis. In the present study, the otolith stable carbon (δ13C) and oxygen (δ18O) isotope ratios of four adult L. polyactis groups (Y-1–4) sampled in the southern Yellow and East China Seas (SYS and ECS) were determined at multiple life stages, including the larval dispersal period (core), overwintering period (A1), and one whole life cycle except the post-spawning period (A2). Dunn’s multiple comparison test showed that there was no difference among the Y-1, Y-2, and Y-3 groups in the otolith core and A1 zones (p > 0.05); the otolith δ13C and δ18O of the Y-4 group were significantly higher than those of the Y-3 group (p < 0.05) in the three analysed zones. In the otolith A2 zone, δ13C and δ18O of the Y-1 group were significantly higher than those of the Y-3 group (p < 0.05). Combined with the biplot of otolith δ13C and δ18O, the quadratic discriminant analysis (QDA) of the otolith core, A1 and A2 zones showed that: (1) in the otolith core zone, two dominant larval aggregations occurred, likely distributed in the coastal waters of northern Lvsi and Haizhou Bay fishing grounds (Y-4 and part Y-1/2 groups) and Zhoushan and southern Yangtze Estuary fishing grounds (Y-3 and part Y-1/2); (2) in the otolith A1 zone, two clear aggregations were separated by Y-4 and Y-1/2/3, suggesting two dominant groups overwintering in the SYS and ECS, respectively; and (3) in the otolith A2 zone, two dominant aggregations were separated by Y-4/1 and Y-2/3. In addition to the long-term larval dispersal process, the migratory route between spawning and overwintering grounds may be diverse, explaining the non-significant genetic differentiation of L. polyactis from different groups. Combining these results with those of previous studies on the life history of L. polyactis, a schematic map of the migratory routes is depicted providing important references for effective resource management.

Comparison of Viral Production and Decay Rates at the Surface and Bottom of the Euphotic Zone in the Summertime in the Southern East China Sea

Viral dynamics are the result of the balance between the rates of viral production and decay. Here, we have carried out independent measurements of viral production and decay rates in different depths of the southern East China Sea in summer (August and October 2021). In this study, the prevalence of viral abundance at the surface waters (14.2~27.6 × 105 viruses mL−1) was significantly higher than the bottom of the euphotic zone (2.9~12.6 × 105 viruses mL−1). As for viruses to bacteria ratio (VBR) values, we found a wide variability both at the surface (1.4 to 3.2) and bottom of the euphotic zone (2.1 to 16.2). The results of our study showed that at all stations examined, in the southern East China Sea, the values of gross viral production (GVP) were significantly higher in the sunlit surfaces compared to the bottom of the euphotic zone. In particular, our analysis indicates that no significant viral decay rates (VD) were observed in some regions at the bottom of the euphotic zone. Here, we also provide a budget for viral abundance and net viral production in different regions in the southern East China Sea. The GVP or VD is not applicable in our case to explain VBR is high at bottom of the euphotic zone. The mechanisms underlying VBR uncoupling, viral production, and viral loss in marine systems are still being investigated.

Spatiotemporal distribution of Lophius litulon in the southern Yellow Sea and East China Sea

In order to investigate the temporal-spatial distribution of yellow goosefish in the open waters of the southern Yellow Sea (SYS) and East China Sea (ECS), according to the fishery data by bottom-trawl surveys and environmental data including sea bottom temperature (SBT), sea bottom salinity (SBS), bottom concentration of dissolved oxygen (BDO) and depth during 2018-2019, we established habitat suitability index (HSI) models by arithmetic mean (AMM) and geometric mean (GMM) methods, and compared the model outputs by cross validations. Especially, the weight of each environmental factor was evaluated by boosted regression tree (BRT). Results showed that the area with the highest habitat quality varied among seasons. The yellow goosefish mainly inhabited in the adjacent area of the Yangtze River Estuary and coastal waters of Jiangsu Province with depth ranged from 22 to 49 m in spring. The optimal inhabitation was located in the SYS, with the bottom temperature ranged from 8.9-10.9 ℃ in summer and autumn. Particularly, the optimal inhabitation extended from the SYS to the ECS with bottom temperature ranged from 9.2-12.7 ℃ in winter. Results of BRT models showed that depth was the most important environmental factor in spring and bottom temperature was the crucial one in the other three seasons. Results of cross validation showed that the weighted AMM-based HSI model performed better for yellow goosefish in spring, autumn and winter. The distribution of yellow goosefish was closely related to its biological traits and environmental factors in the SYS and ECS, China.